Rivers of Europe

List of Contributors vii List of Contributors Aydın Akbulut, Gazi University, Faculty of Science and Arts, Departmen...

Author: Klement Tockner | Christopher T. Robinson | Urs Uehlinger

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List of Contributors

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List of Contributors

Aydın Akbulut, Gazi University, Faculty of Science and Arts, Department of Biology, 06500 Be¸sevler Ankara, Turkey Nuray (Emir) Akbulut, Hacettepe University, Faculty of Science, Department of Biology, 06532 Beytepe, Ankara, Turkey Jurij V. Aleksandrov, Pskov Department of GosNIORH, Gorkij Street 13, Pskov, Russian Federation Margarita S. Alexevnina, Permsky State University, Perm’, Russia Claude Amoros, UMR CNRS 5023, Université Lyon 1, 43 Boulevard du 11 novembre 1918, F-69622 Villeurbanne Cedex, France Hans E. Andersen, National Environmental Research Institute (NERI) - University of Aarhus, Vejlsovej 25, 8600 Silkeborg, Denmark N.A. Arnaut, Laboratory of Hydrogeology and Engineering Geology, Institute of Geophysics and Seismology, Moldavian Academy of Sciences, Academiei Street 3, 2028 Kishinev, Republic of Moldova Hartmut Arndt, Institute for Zoology, University of Cologne, D-50931 Köln, Germany Mikhail A. Baklanov, Permsky State University, Perm’, Russia Jürgen Bäthe, EcoRing, Graftstr. 12, 37170 Uslar, Germany Christian Baumgartner, Donauauen National Park GmbH, 2304 Orth an der Donau, Schloss Orth, Austria Serdar Bayarı, Hacettepe University, Faculty of Engineering, Hydrogeological Engineering Section, 06532 Beytepe, Ankara, Turkey Horst Behrendt, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 310, 12587 Berlin, Germany V.V. Bekh, Laboratory of Fish Genetics and Selection, Institute of Fisheries, Ukrainian Academy of Agrarian Science, Obukhivska Street 135, 03164 Kyiv, Ukraine Jürg Bloesch, International Association for Danube Research (IAD), Stauffacherstrasse 159, 8004 Zürich, Switzerland. Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland B. Boz, Italian Center for River Restoration, Viale Garibaldi 44/A, Mestre 40173, Italy Jean-Paul Bravard, Université Lyon 2, Faculté de Géographie, Histoire, Histoire de l’art, Tourisme, 5 Avenue Pierre Mendès-France, 69676 Bron Cedex, France John E. Brittain, Norwegian Water Resources and Energy Directorate, PO Box 5091 Majorstua, 0301 Oslo, Norway. Natural History Museum, University of Oslo, PO Box 1172 Blindern, 0318 Oslo, Norway Jim Bogen, Norwegian Water Resources and Energy Directorate, PO Box 5091 Majorstua, 0301 Oslo, Norway

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Agrita Briede, Institute of Biology, University of Latvia, Miera Str. 3, 2169, Latvia Sturla Brørs, Directorate for Nature Management, 7485 Trondheim, Norway Georges Carrel, UR Hydrobiologie, Cemagref, 3275 Route Cézanne, CS 40061, F-13182 Aix-enProvence Cedex 5, France Jean-Pierre Descy, Research Unit in Organismal Biology (URBO), University of Namur, Rue de Bruxelles 61, B-5000 Namur, Belgium Marie-José Dole-Olivier, UMR CNRS 5023, Université Lyon 1, 43 Boulevard du 11 novembre 1918, F-69622 Villeurbanne Cedex, France Ivars Druvietis, Institute of Biology, University of Latvia, Miera Str. 3, 2169, Latvia Svetlana A. Dvinskikh, Permsky State University, Perm’, Russia Alcibiades N. Economou, Hellenic Centre for Marine Research, Institute of Inland Waters 46.7 km Athens-Sounion Avenue, 190 13 Anavissos, Greece Jon Arne Eie, Norwegian Water Resources and Energy Directorate, Post Office Box 5091 Majorstuen, N-0301 Oslo, Norway Tatjana V. Eremkina, Ural Institute of Water Biological Facility, Yasnaja Street 1, 620086 Ekaterinburg, Russia Per Einar Faugli, Norwegian Water Resources and Energy Directorate, Post Office Box 5091 Majorstuen, N-0301 Oslo, Norway Maria Feio, IMAR and Department of Zoology, University of Coimbra, 3004-517 Coimbra, Portugal Helmut Fischer, Federal Institute of Hydrology (BfG), Am Mainzer Tor 1, 56068 Koblenz, Germany Nikolai Friberg, Macaulay Institute, Craigiebuckler, Aberdeen, United Kingdom Aleksandra Gancarczyk, Drawa National Park, ul. Lésników 2, 73-220 Drawno, Poland Ritma Gaumiga, Latvian Fish Resources Agency, Daugavgrivas 8, Riga, 1048 G¸ ertrude Gavrilova, Institute of Biology, University of Latvia, Miera Str. 3, 2169, Latvia Yuri V. Gerasimov, I.D. Papanin Institute Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia Chris N. Gibbins, School of Geosciences, University of Aberdeen, Aberdeen AB24 3UF, UK Gísli M. Gíslason, Institute of Biology, University of Iceland, Askja-Natural Science Building, 101 Reykjavík, Iceland Manuel A.S. Graça, IMAR and Department of Zoology, University of Coimbra, 3004-517 Coimbra, Portugal Konstantinos C. Gritzalis, Hellenic Centre for Marine Research, Institute of Inland Waters 46.7 km Athens-Sounion Avenue, 190 13 Anavissos, Greece B. Gumiero, Department of Evolutionary and Experimental Biology, Bologna University, Via Selmi 3, Bologna 40126, Italy Justyna Hachoł, Wrocław University of Environmental and Life Sciences, Institute of Environmental Development and Protection, Plac Grunwaldzki 24, 50-363 Wrocław, Poland Svein Haugland, Agder Produkjon Energi AS, Service Box 603, 4606 Kristiansand, Norway Thomas Hein, University of Natural Resources and Applied Life Sciences, Vienna, Institute of Hydrobiology and Aquatic Ecosystem Management, Max – Emanuelstrasse 17, 1180 Vienna and WasserCluster Lunz, Dr. Carl-Kupelwieser-Prom. 5, 3293 Lunz/See, Austria Alan G. Hildrew, School of Biological & Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK

List of Contributors

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Carl. C. Hoffmann, National Environmental Research Institute (NERI) - University of Aarhus, Vejlsovej 25, 8600 Silkeborg, Denmark Nils Arne Hvidsten, Norwegian Institute for Nature Research, Tungasletta 2, N-7485 Trondheim, Norway Arne J. Jensen, Norwegian Institute for Nature Research, 7485 Trondheim, Norway. Norwegian Institute for Nature Research, Tungasletta 2, N-7485 Trondheim, Norway V.M. Katolikov, Department of Channel Processes, State Hydrological Institute, 23 Second Line V.O., 199053 St. Petersburg, Russia Ludmila G. Khokhlova, Institute of Biology, Komi Science Centre, UrD RAS,167982 Syktyvkar, Komi Republic, Russia Alexander B. Kitaev, Permsky State University, Perm’, Russia Sergej K. Kochanov, Institute of Biology, Komi Science Centre, UrD RAS, 167982 Syktyvkar, Komi Republic, Russia Alexander V. Kokovkin, Institute of Social and Economic Problems of the North, Komi Science Centre, 167982 Syktyvkar, Komi Republic, Russia Ludmila G. Korneva, I.D. Papanin Institute Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia Ludmila G. Korneva, I.D. Papanin Institute Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia Brian Kronvang, National Environmental Research Institute (NERI) - University of Aarhus, Vejlsovej 25, 8600 Silkeborg, Denmark L.A. Kudersky, Department of Hydrobiology, Institute of Limnology, Russian Academy of Sciences, Sevastyanov Street 9, 196105 St. Petersburg, Russia Jan Henning L’Abée-Lund, Norwegian Water Resources and Energy Directorate, Post Office Box 5091 Majorstuen, N-0301 Oslo, Norway Nicolas Lamouroux, UR Biologie des Ecosystèmes Aquatiques, 3 bis quai Chauveau, CP 220, F-69336 Lyon Cedex 09, France Małgorzata Łapi´nska, Department of Applied Ecology, University of Łód´z, 12/16 Banacha Str., 90-237 Łód´z, Poland Valentina I. Lazareva, I.D. Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia Rob. S. E. W Leuven, Department of Environmental Science, Institute for Wetland and Water Research (IWWR), Faculty of Science, Radboud University Nijmegen, NL-6500 GL Nijmegen, The Netherlands Alexander S. Litvinov, I.D. Papanin Institute Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia N.S. Loboda, Department of Hydrology ; Odesa State Environmental University, Lvovskaya street 15, 65016 Odesa, Ukraine. B. Maiolini, Natural Science Museum, Via Calepina 14, Trento, Italy Florian Malard, UMR CNRS 5023, Université Lyon 1, 43 Boulevard du 11 novembre 1918, F-69622 Villeurbanne Cedex, France Iain A. Malcolm, Fisheries Research Services Freshwater Laboratory, Pitlochry, Perthshire PH16 8BB, UK B. Malmqvist, Department of Ecology and Environmental Science, Umeå University, SE-90187 Umeå, Sweden Marina M. Mel’nik, Pskov Department of GosNIORH, Gorkij Street 13, Pskov, Russian Federation

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Kjetil Melvold, Norwegian Water Resources and Energy Directorate, PO Box 5091 Majorstua, U 0301 Oslo, Norway. Norwegian Water Resources and Energy Directorate, Post Office Box 5091 Majorstuen, N-0301 Oslo, Norway Natalya M. Mineeva, I.D. Papanin Institute Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia F. Moroni, Po River Basin Authority, Via Garibaldi 75, Parma 43100, Italy Isabel Muñoz, Department of Ecology, Faculty of Biology, University of Barcelona, Avenue Diagonal 645, 08028 Barcelona, Spain T. Muotka, Department of Biology, University of Oulu, P.O. Box 3000, FIN-90014 Oulu, Finland C. Nilsson, Department of Ecology and Environmental Science, Umeå University, SE-90187 Umeå, Sweden Victor M. Noskov, Permsky State University, Perm’, Russia Franciszek Nowacki, Polish Geological Institute, Lower Silesian Branch, Jaworowa 19, 53-122 Wrocław, Poland Alexander G. Okhapkin, Nizhegorodski State University, Nizhni Novgorod, Russia Jón S. Ólafsson, Institute of Biology, University of Iceland, Askja-Natural Science Building, 101 Reykjavík, Iceland. Institute of Freshwater Fisheries, Keldnaholt, 112 Reykjavík, Iceland Jean-Michel Olivier, UMR CNRS 5023, Université Lyon 1, 43 Boulevard du 11 novembre 1918, F-69622 Villeurbanne Cedex, France Vaida Olšauskytè, European Commission, Joint Research Centre, Institute for Environment and Sustainability; Via E. Fermi 2749 21027 Ispra (VA), Italy Ana Ostojic’, University of Zagreb HR-10000 Zagreb Croatia

Faculty of Science Division of Biology Rooseveltov trg 6

Vladimir G. Papchenkov, I.D. Papanin Institute Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia Elga Parele, Institute of Biology, University of Latvia, Miera Str. 3, 2169, Latvia Momir Paunovic’, Institute for Biological Research 142 despota Stefana Boulevard-11060 Belgrade Serbia Morten L. Pedersen, Aalborg University, Department of Civil Engineering, Sohngaardsholmsvej 57, 9000 Aalborg, Denmark Fabian D. Peter, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland Vegard Pettersen, Statkraft Energi AS, Lilleakerveien 6, Post Office Box 200 Lilleaker, N-0216 Oslo, Norway Lars-Evan Petterson, Norwegian Water Resources and Energy Directorate, POBox 5091 Majorstuen, N-0301 Oslo, Norway Vasily I. Ponomarev, Institute of Biology, Komi Science Centre, UrD RAS, Syktyvkar, Komi Republic, Russia Elena V. Presnova, Permsky State University, Perm’, Russia Martin Pusch, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 310, 12587 Berlin, Germany M. Rinaldi, Department of Civil and Environmental Engineering, University of Florence, Via S. Marta 3, Firenze 50139, Italy Christopher T. Robinson, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland Anna M. Romaní, Institute of Aquatic Ecology, University of Girona, Campus Montilivi 17071, Girona, Spain

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Sergi Sabater, Institute of Aquatic Ecology, University of Girona, Campus Montilivi 17071, Girona, Spain Catalan Institute for Water Research (ICRA), Girona, Spain Yalçın S¸ ahin, Eski¸sehir Osman Gazi University, Faculty of Science and Arts, Department of Biology, 26480 Me¸selik, Eski¸sehir, Turkey. Svein Jakob Saltveit, Freshwater Ecology and Inland Fisheries Laboratory, Natural History Museum, University of Oslo, Post Office Box 1172 Blindern, N-0318 Oslo, Norway Leonard Sandin, Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment, 750 07 Uppsala, Sweden Martin Schneider-Jacoby, EuroNatur – European Nature Heritage Fund, Konstanzer Str. 22, 78315 Radolfzell, Germany Franz Schöll, Federal Institute of Hydrology (BfG), Am Mainzer Tor 1, 56068 Koblenz, Germany Matthias Scholten, Flussgebietsgemeinschaft Weser, An der Scharlake 39, 31135 Hildesheim, Germany Elena B. Seletkova, Permsky State University, Perm’, Russia Grigory Kh. Shcherbina, I.D. Papanin Institute Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia Galina V. Shurganova, Nizhegorodski State University, Nizhni Novgorod, Russia Rosi Siber, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland. Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland B.G. Skakalsky, Department of Environmental Chemistry, State Hydrometeorological Institute of Russia, Malookhtinsky Prospect 98, 195196 St. Petersburg, Russia ˆ Ricˇardas Skorupskas, Vilnius University, Ciurlionio g. 21/27, 03101 Vilnius, Lithuania Nikolaos Th. Skoulikidis, Hellenic Centre for Marine Research, Institute of Inland Waters 46.7 km Athens-Sounion Avenue, 190 13 Anavissos, Greece Nike Sommerwerk, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 310, 12587 Berlin, Germany Chris Soulsby, School of Geosciences, University of Aberdeen, Aberdeen AB24 3UF, UK. Fisheries Research Services Freshwater Laboratory, Pitlochry, Perthshire PH16 8BB, UK Gunta Spri´ng´ e, Institute of Biology, University of Latvia, Miera Str. 3, 2169, Latvia Bernhard Statzner, CNRS, Biodiversité des Ecosystémes Lotiques, 304 Chemin Creuse Roussillon, F-01600 Parcieux, France Sonja Stendera, Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment, 750 07 Uppsala, Sweden Angelina S. Stenina, Institute of Biology, Komi Science Centre, UrD RAS, 167982 Syktyvkar, Komi Republic, Russia A.N. Sukhodolov, Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, D-12587 Berlin, Germany N. Surian, Department of Geography, University of Padova, Via del Santo 26, Padova 35123, Italy Lars M. Svendsen, National Environmental Research Institute (NERI) - University of Aarhus, Vejlsovej 25, 8600 Silkeborg, Denmark Doerthe Tetzlaff, School of Geosciences, University of Aberdeen, Aberdeen AB24 3UF, UK. Fisheries Research Services Freshwater Laboratory, Pitlochry, Perthshire PH16 8BB, UK H. Timm, Estonian University of Life Sciences, Institute of Agricultural and Environmental Sciences, Centre for Limnology, 61117 Rannu, Tartumaa, Estonia

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Klement Tockner, Swiss Federal Institute of Aquatic Science and Technology, Uberlandstrasse 133, 8600 Dübendorf, Switzerland. Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 310, 12561 Berlin, Germany Diego Tonolla, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland Urs Uehlinger, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland. Department of Aquatic Ecology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), CH-8600 Dübendorf, Switzerland M.A. Usatii, Laboratory of Ichthyology, Institute of Zoology, Academiei Street 1, 2028 Kishinev, Republic of Moldova Karl M. Wantzen, Limnological Institute, University of Konstanz, ATIG-Aquatic-Terrestrial Interaction Group, D-78457 Konstanz, Germany Ewa Wnuk-Gławdel, Drawa National Park, ul. Les´ników 2, 73-220 Drawno, Poland Christian Wolter, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 310, 12587 Berlin, Germany Margarita I. Yarushina, Russian Academy of Science, Ural Division, Institute of Plant & Animal Ecology, Street of 8 March 202, 620144 Ekaterinburg, Russia Maciej Zalewski, Department of Applied Ecology, University of Łód´z, 12/16 Banacha Str., 90-237 Łód´z, Poland. International Institute Polish Academy of Sciences – European Regional Centre for Ecohydrology under the auspices of UNESCO, 3 Tylna Str., 90-364 Łódz´, Poland. Euvgeny A. Zinov’ev, Permsky State University, Perm’, Russia Stamatis Zogaris, Hellenic Centre for Marine Research, Institute of Inland Waters 46.7 km AthensSounion Avenue, 190 13 Anavissos, Greece Vaida Olšauskyté, European Commission, Joint Research Centre, Institute for Environment and Sustainability; Via E. Fermi 2749 21027 Ispra (VA), Italy ˆ Riˆcardas Skorupskas, Vilnius University, Ciurlionio g. 21/27, 03101 Vilnius, Lithuania

List of Contributors

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Foreword

I am grateful for the opportunity to write the foreword for Rivers of Europe as it represents the European counterpart to Rivers of North America, edited by Bert Cushing and myself (Benke and Cushing 2005), and is also published by Academic Press/Elsevier. Editors Klement Tockner, Urs Uehlinger, and Christopher T. Robinson believe as we did that comprehensive description of a continent’s rivers is essential if human societies are to have any hope of understanding and wisely managing our fresh water resource and the rivers within which it flows – now and into the future. This book is important for one simple reason: fresh water is the single most important natural resource on earth. Consider that in looking for past or current life on other planets, finding evidence of water is a primary goal. Without fresh water, inland environments would be lifeless. Rivers of Europe represents by far the most comprehensive effort to describe Europe’s rivers to date. This outstanding reference contains an enormous amount of information in characterizing and synthesizing natural features of rivers and their drainage basins (catchments), including such things as climate, land use, hydrology, and biodiversity. It also highlights environmental issues of great importance to citizens and governments, including fragmentation by dams, pollution, introduction of nonnative species, and reductions in biodiversity. Although the book deals with serious issues, it will be a pleasure to read for both professional and layperson with its many beautiful maps and photographs, as well as extensive data tables that allow comparisons of physical and biological features between rivers and across regions. The editors have assembled a team more than 130 river experts from throughout Europe to describe most rivers of the continent. Included are 165 rivers from the Atlantic Ocean to the Ural Mountains and Caspian Sea. In some ways, creating Rivers of Europe surely was an even greater challenge than Rivers of North America since editors had to work with authors from many more countries and native languages. Nonetheless, this unique compendium is the result of meeting that challenge and producing what should become a standard reference for many years to come. There are interesting contrasts between North American and European rivers. The land area of Europe is roughly half that of North America, yet European rivers are found in 48 countries rather than three. Because most rivers are transboundary, the authors emphasize the particular need for using the river catchment as the key ecological/management unit, rather than political boundaries. Like North America, the diversity of European rivers is impressive, with environments ranging from the Scandinavian-Russian Arctic to mesic regions of middle Europe to arid regions of the Iberian Peninsula and Mediterranean coast. On the other hand, with a lower biodiversity of aquatic fauna in Europe, the authors’ descriptions of river-specific biodiversity, and threatened, nonnative, and extinct species serve to highlight the pressing need for conservation. Human influence on European river systems appears to have occurred earlier than in North America, with the possible exception of southern Mexico. The first alterations to European rivers were probably deforestation of floodplains, wetland drainage, and early agriculture, at least 6000 years ago. More dramatic alterations of channels, small dams, and levee-building probably did not occur in any significant way until 1000 years ago, and as the centuries passed, such activities became more widespread. Like North America, however, most significant engineering projects, particularly large dams, did not appear until the 20th century. As a result, few European rivers today are free-flowing with significant natural floodplains (only 30 of 165 described in this book), and many suffer from a wide variety of additional impacts. Given this long history and intensity of river degradation, Tockner and his collaborators emphasize the need for conservation of the few natural rivers and restoration of many others. Restoration of rivers degraded for more than a century creates a special challenge because reference conditions are non-existent in many regions. Furthermore, all conservation, restoration and management activities come with a price tag, and establishment of priorities is a major and potentially controversial task.

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The good news for European rivers is that the European Union recently began an important program called the Water Framework Directive (WFD) that requires a management plan for all major European rivers to achieve ‘‘good ecological status’’ by 2015. Rivers of Europe seems uniquely timed to be an invaluable resource to the WFD by providing a foundation for future management decisions. In general, however, the book will greatly appeal to any individual who is fascinated by rivers and will become a single major information source for river scientists, river managers, government agencies, recreationists, and conservationists within Europe and elsewhere. Arthur C. Benke The University of Alabama Tuscaloosa, Alabama, U.S.A.

Preface and Acknowledgements

Rivers traverse our landscapes and often are the major source of water for domestic, agricultural and industrial usage, power generation, navigation, fisheries, and recreation. Rivers also are a source of fascination and discovery for ecologists, hydrologists, geologists, geographers, and environmentalists. They house a tremendous source of aquatic biodiversity, much of which is highly threatened. Because of the vital role rivers play in the landscape and for society, they have been described as the circulatory system of the landscape. In spite of their undeniable and fundamental importance, there is no comprehensive treatment of the natural characteristics and diversity of European rivers nor of the extent to which human society has exploited them. With this book, Rivers of Europe, we tried to narrow this important information gap. In 2005, editors Art Benke and Bert Cushing published the benchmark book Rivers of North America. This book inspired us to compile a similar book on European Rivers. Enthusiastically, we agreed to the task - though being unaware of the major challenges awaiting us. It took almost three years from developing the first concept until completion of the book. Geographically, Europe extends from the Ural Mountains in the east to the Caucasian Alps in the southeast. There are over 150 transboundary rivers in Europe that form or cross borders of two or more countries. Europe has a total population of 780 million people with more than 100 spoken languages. The Rivers of Europe is the first reference book that covers all of Europe. In total, 136 authors from 20 countries contributed to the book, mirroring Europe’s cultural, geographic, and ecological diversity. Our first challenge was to collect comparable information on 165 European rivers, including catchments ranging from Iceland to the Peloponnese, and from the Atlantic coast in Portugal to the shores of the Caspian Sea. On the one hand, we were pleased with the wealth of available information, even for rivers that most people are unfamiliar such as those in Anatolia or northwest Siberia. On the other hand, we were somewhat surprised that even basic information on river basins such as catchment area, discharge, or water temperature was quite difficult to obtain in adequate quality. For example, published data on catchment area varies extremely, even for well-studied rivers such as the Rhine and Danube. Our second challenge was to focus at the catchment rather than country scale. While information on biodiversity or water use is mainly available at the country scale, management of river ecosystems must be done at the catchment scale. In addition, information quality differed between countries, which created a major challenge, especially for transboundary rivers. Therefore, there might be inconsistences between data presented in the individual chapters and those in the introductory chapter, where we analysed data from the same sources for all of Europe. In this respect, this book should stimulate the collection of comparative data for all of Europe and not just for the member states of the European Union. This kind of information is a pivotal requirement for setting priorities for conservation and restoration at the continental scale. We hope that the present book stimulates further research activities on European rivers, and that it supports the implementation of the EU-Water Framework Directive (WFD). The Directive is an extremely ambiguous legislative framework to protect and improve the quality of all water resources, including rivers, lakes, groundwater, and even transitional and coastal waters. The Directive states that “good ecological status” of all European rivers must be achieved by 2015. By reading about so many rivers during the past few years, we must acknowledge that most rivers already have been irreversibly transformed. Many rivers have been managed for centuries, thereby forming important elements in our cultural landscapes. In this respect, most rivers have been trained during the past decades leading to potentially irreversible damages. This book would not have been possible without the support of many people. First and foremost, we heartily thank the contributors of the chapters. It was an amazing pleasure to collaborate with so many enthusiastic and

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dedicated authors from all over Europe. We are especially grateful to Diego Tonolla, Eawag, who has devoted an immense amount of effort to the book. Diego Tonolla developed the European Catchment Data Base, digitized all the catchments, designed the maps, and was essential during the final preparation of the book. Rosi Siber, Eawag, has overseen the entire GIS effort, at the beginning of the project in particular. Special thanks goes to Fabian Peter, who developed the fish data base on European Rivers. Further, he summarized the available information on dragonflies, wetland birds, crayfish, and amphibians. We also thank Verena Keller, Schweizerische Vogelwarte, Sempach, for her support in collecting data on wetland birds, and Vincent Kalkman, European Invertebrate Survey - Nederland Nationaal Natuurhistorisch Museum - and Chair of the IUCN Odonata Specialist Group, for the compilation of the Odonata data. Additional support came from Sónia Ferreira, Cosmin-Ovidiu Manci, Elena Dyatlova, Milen Marinov, Otakar Holusa, Milos Jovic and Vladimir Skvortsov. Jörg Freyhof provided helpful information on the European freshwater fish fauna. Special thanks go to illustrator Lydia Zweifel for drawing all graphs for the book. Jan Landert, Christoph Gasser, and Barbara Köfler-Tockner assisted in the preparation of the book at various stages. We thank the many people that contributed photos that greatly enhanced the asthetics of the book. They are acknowledged in the individual chapters. The editors thank the many colleagues and authors that encouraged us and provided feedback over the past three years. We are very grateful to Andy Richford, Stephen Pegg, Emily McCloskey, and Mara Vos-Sarmiento of Elsevier/Academic Press for guiding us through the planning and execution of the project. Finally, we thank our home institutions Eawag, the Swiss Federal Institute of Aquatic Sciences and Technology, and IGB, the LeibnizInstitute of Freshwater Ecology and Inland Fisheries, for logistic and financial support. Without this support, it would have been impossible to establish the European Catchment Data Base, to design the GIS maps, and to redraw all graphs. We thank DIVERSITAS for endorsing the work presented. This book contributes to the implementation of the Science Plan of the DIVERSITAS freshwater BIODIVERSITY Cross-cutting Network. Berlin and Dübendorf, October 2008. Klement Tockner, Christopher T. Robinson, Urs Uehlinger

Chapter 1

Introduction to European Rivers Klement Tockner

Urs Uehlinger

Christopher T. Robinson

Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), M€ uggelseedamm 310, Berlin, Germany Institute of Biology, Freie Universit€ at, Berlin, Germany

Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland

Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland

Diego Tonolla

Rosi Siber

Fabian D. Peter

Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland

Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland

Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland

1.1. 1.2. 1.3. 1.4. 1.5. 1.6. 1.7. 1.8. 1.9. 1.10. 1.11. 1.12.

1.13. 1.14.

Introduction Biogeographic Setting Cultural and Socio-economic Setting Hydrologic and Human Legacies Early and Recent Human Impact Temperature and Precipitation Water Availability and Runoff Riverine Floodplains River Deltas Water Quality Freshwater Biodiversity Environmental Pressures on Biodiversity 1.12.1. Fragmentation 1.12.2. Water Stress 1.12.3. Land Use Change 1.12.4. Non-native Fish Species The European Water Framework Directive Knowledge Gaps Acknowledgements References

1.1. INTRODUCTION Rivers recognize no political boundaries. This is particularly true for Europe, which has over 150 transboundary rivers (Whitton 1984). For example, the Danube is the 29th longest river globally, and it drains parts of 19 countries and 10 ecoregions. Further, 8 of the 10 largest catchments in Europe (Figures 1.1 and 1.2, Table 1.1) are in the eastern plains of Russia and the Ukraine and information on their present status Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

is highly limited. Europe also has a long history in river training with most rivers being severely fragmented, channelized, and polluted (Petts et al. 1989; Kristensen & Hansen 1994; Tockner & Stanford 2002; UNEP 2004; Nilsson et al. 2005). Recently, the European Union launched an ambitious program called the Water Framework Directive (WFD) that requires a catchment management plan for all major European rivers for achieving ‘good ecological status’ by 2015. In this introductory chapter, we provide a comprehensive overview of all major European catchments included in the book (Figure 1.2), starting with the biogeographic setting, with an emphasis on physiography, hydrology, ecology/biodiversity, and human impacts.

1.2. BIOGEOGRAPHIC SETTING Europe forms the northwestern physiographic constituent of the larger landmass known as Eurasia. Europe covers an area of 11.2 million km2 that includes the European part of Russia, parts of Kazakhstan (Ural River Basin), the Caucasus, Armenia, Cyprus, and Turkey (Figures 1.1 and 1.2). Armenia and Cyprus are considered as transcontinental countries; and Turkey is included because of political and cultural reasons. The average altitude of Europe is 300 m asl compared to 600 m asl for North America and 1000 m asl for Asia. Only 7% of Europe is above 1000 m asl. Europe has an extensive and deeply penetrating network of water bodies. Its 117 000 km convoluted coastline facilitated easy access to the interior, and it is this feature that contributed to the rapid development of its southern shores along the Mediterranean Sea (Stanners & Bourdeau 1995; Butlin & Dodgson 1998; Hughes 2001). 1

2

PART | I Rivers of Europe

FIGURE 1.1 Topographic map of Europe and location of geographic regions covered in the book. Data sources: see Appendix.

Europe is highly diverse, both biogeographically and ecologically. The European Environmental Agency has identified 11 biogeographical regions that are considered as useful geographical reference units for describing habitat types and species that live under similar conditions (Figure 1.3A) (http://reports.eea.europa.eu/ report_2002_0524_154909/en). The biogeographic regions dataset contains the official delineations used in the Habitats Directive and for the EMERALD Network set up under the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention). In addition, Europe has been divided into 71 ecological distinct areas, based on climatic, topographic, and geobotanical data, together with the judgement of a large team of experts from several European nature-related institutions (Figure 1.3B). Ecological regions are areas with relatively homogeneous ecological conditions, within which comparisons and assessments of different expressions of biodiversity are meaningful (e.g. rivers and lakes, see also Illies 1978).

1.3. CULTURAL AND SOCIO-ECONOMIC SETTING There are distinct cultural, demographic, socio-economic, and political gradients across Europe (Bacci 1998; Hughes 2001). Today’s human population is 780 million with an average population density of 69 people/km2. At the catchment scale, the population density ranges from <2 people/km2 (e.g. Pechora Basin in Russia) to 1257 people/km2 (Mersey basin in Great Britain). The annual Gross Domestic Product (GDP; US$/person) ranges over two-orders-of-magnitude, from 600$ (Dniester Basin in Moldova) to 65 000$ (Aare Basin in Switzerland, a subbasin of the Rhine). Human life expectancy ranges from 61 (Ural Basin) to 80 years (river basins in Iceland, Italy, Spain, Sweden, and Switzerland). More than 100 languages are spoken across Europe, with the greatest number (27 languages) spoken in the Caucasus region.

Chapter | 1 Introduction to European Rivers

FIGURE 1.2 Spatial distribution of European catchments in 17 different geographic regions (different colors), including subcatchments of the Volga, Danube, Rhine, and Rhone Basins. Data sources: see Appendix.

3

4

PART | I Rivers of Europe

TABLE 1.1 The 20 largest catchments in Europe (including Turkey and the Caucasus).

Volga Danube Dnieper Don N Dvina Pechora Neva Ural Kura Vistula Rhine Elbe Euphratesa Oder Loire Nemunas Rhone Duero Ebro W Dvina

Area (km2)

Discharge (km3/year)

Relief (m)

Population (people/km2)

Urban, Arable and Pasture (%)

GDP ($/year)

Protected (%)

Fish (native)

Fish (nonnative)

1 431 296 801 093 512 293 427 495 357 000 322 000 281 000 252 848 193 803 192 980 185 263 148 242 127 304 118 861 117 054 98 757 98 556 97 290 85 362 83 746

253.9 204.7 53.0 27.3 109.0 138.0 79.8 10.6 17.1 33.4 73.0 27.4 31.6 17.3 27.0 25.0 53.6 13.6 13.4 20.4

1536 3651 411 804 422 1604 390 1094 4816 2316 3786 1456 3557 1468 1704 354 4452 2359 3104 307

45 102 64 46 5 2 17 15 74 114 313 169 57 135 68 52 105 37 34 32

53.4 58.3 65.0 86.3 7.3 0.4 13.7 73.3 56.5 66.3 59.1 66.9 62.1 65.6 76.5 55.3 42.8 56.8 48.7 39.6

2340 7007 1388 1508 2873 2928 6181 2205 1267 3789 31 822 14 068 1535 5583 22 196 2680 24 462 15 058 19 587 2598

5.7 2.4 3.2 3.2 5.2 12.2 5.1 0.9 5.5 2.6 0.4 4.3 <0.1 1.5 1.5 5.2 8.9 1.2 3.2 8.0

59 115 40 66 35 35 44 59 33 55 60 43 42 53 26 48 46 21 27 43

25 19 13 9 6 2 3 3 8 19 25 8 1 11 31 6 18 13 20 2

Relief: Calculated difference between highest and lowest point (resolution: 1000 m 1000 m) in each catchment. Human population density: people per km2. GDP: annual gross domestic product per person and year. Protected: National parks, Ramsar sites, National nature reserves, and other nationally protected areas. For data sources and detailed explanation see Appendix. a

Only Turkey.

1.4. HYDROLOGIC AND HUMAN LEGACIES Many European rivers have substantially changed in length, catchment area, and flow direction over the past 20 000 years (Petts et al. 1989; Starkel et al. 1991). For instance, at the onset of the last glacial maximum about 20 000 year BP, a paleo-river known as the ‘Channel River’, located between the present France and Britain, extended across the raised continental margin. Most major rivers in northwestern Europe (e.g. Rhine, Meuse, and Thames) contributed to its waters. In addition, damming by the Fennoscandian ice sheet caused the development of southward-flowing melt-water valleys and ice-margin spillways running westward. These spillways collected proglacial waters from rivers west of the Elbe basin that drained into the Channel River. The Channel River was the largest river system that drained the European continent, thereby affecting the hydrology of much of Europe as well as that of coastal ecosystems (Menot et al. 2006). The long-term evolution of European rivers during the Holocene can be placed into four regional categories (Petts et al. 1989): 1. Rivers recently developed on areas formerly covered by ice sheets and affected by isostatic uplift; 2. Rivers of the former periglacial zone partly influenced by ice sheets; 3. Rivers of the former periglacial zone with lower reaches influenced by eustatic sea-level changes; and 4. Rivers of southern Europe within the region of former cold steppe and forest-steppe.

Central European rivers show 3–6 separate alluvial fills that correlate well with stages of glacial advance and treeline lowering in the Alps (Figure 1.4). In the European lowlands, 2–3 alluvial fills are at times recorded, although major lateral channel shifts are more common as a consequence of fluctuations in discharge and sediment flux. In southern Europe, the tendency towards braiding has anthropogenic (deforestation and subsequent increases in sediment transport) and natural origins (higher flood frequency during the Little Ice Age, 1450–1850). In piedmont zones, the tendency towards braiding was repeated during cooler and moister stages. In the western Siberian river valleys, for example the Pechora and Mezen valleys, braided channels probably changed to a more meandering style after the retreat of permafrost and then towards braiding during permafrost advances (Starkel 1991; Starkel et al. 1991).

1.5. EARLY AND RECENT HUMAN IMPACTS Deforestation and cultivation of soils were the main human activities that caused major changes in discharge and sediment transport. In southern and central Europe, distinct stages of sediment deposition have been recorded from the late Bronze Age and even more extensively in Roman times. General aggradation of European valley floors occurred in medieval times and is reflected in the rising of channel forms. Prior to the 11th century, river works were still primitive, consisting mostly of embankments built for flood control and land reclamation. There were two European centres

5

Chapter | 1 Introduction to European Rivers

FIGURE 1.3 (A) Distribution of European biogeographical regions. (B) distribution of European ecoregions (ecological regions). The numbers correspond to the numbers in the tables within individual chapters. Locations of the geographic regions covered in the book are indicated. Data sources: see Appendix.

of technological advance in river regulation during the medieval period. The Netherlands developed dredging technologies, designed floodgates, and built groynes and retaining walls. In Italy, land reclamation (‘La bonifica’) was common with most large rivers being partly channelized by 1900. The greatest single engineering effort in the 19th century was the regulation of the lower Tisza River, the largest tributary of the Danube River, where 12.5 106 km2 of floodplain marsh were drained and the river course shortened by 340 km (Petts et al. 1989; Tockner & Stanford 2002). Today, European catchments are highly fragmented by >6000 large dams. Reservoirs behind these dams can store 13% of the mean annual runoff of Europe (UNEP 2004). The highest numbers of dams occur in Spain (1196) and Turkey (625). Of the 20 largest European rivers, only the Northern Dvina in Russia, draining to the White Sea, is considered free-flowing. Of the 164 catchments (including subcatchments) included in this chapter (Figure 1.2), only 28 are considered as free-flowing. Most of these free-flowing rivers are in northern Europe (Arctic, Fennoscandian Shield,

Volga tributaries) or drain relatively small catchments (e.g. Amendolea in Italy, Frome and Piddle in Great Britain, and Sperchios in the Balkans).

1.6. TEMPERATURE AND PRECIPITATION European air temperatures are relatively mild, compared to those of continental land masses in North America and Asia located at similar latitudes, because of westerly winds warmed by the Gulf Stream carrying subtropical water to the European west coast. Mean annual air temperatures show a distinct north–south gradient with < 3 C in the catchment of some Arctic rivers to >15 C in the south–western part of the Iberian Peninsula, Calabria, and southern Anatolia (Figure 1.5A). The mountain ranges of the Alps and Caucasus, and the eastern Anatolian uplands (to a minor extent also the southern Carpathian Mountains and the Pyrenees) are cold islands in a relatively warm environment.

6

FIGURE 1.3 (Continued).

PART | I Rivers of Europe

7

Chapter | 1 Introduction to European Rivers

FIGURE 1.4 Changes in fluvial systems in a north–south cross-section through Europe: (b) braided (bed-load river); (m) meandering (suspended-loaded river); (m(s)): small meanders; (m(l)): large meanders. The diagram also includes the probable sequence of channel patterns for Siberian rivers.

Redrawn from Starkel (1991).

Precipitation patterns in Europe are characterized by a west–east gradient, that is decreasing precipitation with distance from the Ocean that reflects increasing continentality (Figure 1.5B). Topographic effects are superimposed on this pattern: Precipitation is high in the western front ranges of the mountains of western Britain, Norway, the western Iberian Peninsula, and low in the adjacent eastern areas (rain shadows). Areas of high precipitation (>300 cm) occur in the Alps, the adjacent northern Dinaric Alps (maximum >320 cm) and the Western Caucasus.

1.7. WATER AVAILABILITY AND RUNOFF Water availability, defined as the annual long-term average renewable water resource derived from natural discharge including consumptive water use, shows a large spatial variation among river basins. Annual water availability ranges from >1000 mm/year (western Norway, Britain’s west coast,

southern Iceland) to <100 mm/year (parts of Spain, Sicily, large parts of the Ukraine, Southern Russia, large parts of Turkey). It reflects patterns of precipitation in most of Europe, whereas available water is transferred by rivers into more dry regions in other parts. Hungary, for example, attains most of its water from outside the country via the Danube and Tisza. The total average runoff of European rivers is 3100 km3/year from 11 million km2 (8% of the world average; Shiklomanov 1997). The 20 largest rivers (total area: 5.9 million km2) contribute >1/3 to the total continental runoff (Table 1.1). The average annual specific runoff ranges from 68 mm/year (Asi River in southeast Turkey) to 1150 mm/year (Tay River in Scotland). High seasonality in runoff is typical for rivers in southern Europe and Turkey such as the Guadalquivir (Iberian Peninsula) and Upper Euphrates, and for Boreal and Arctic rivers such as the Glomma (Norway) and Pechora (Russia). Low runoff variability is characteristic for central European rivers (e.g., Elbe) and Steppic rivers (e.g. Dnieper) (Figure 1.6).

8

PART | I Rivers of Europe

FIGURE 1.5 Mean annual air temperature (A) and mean annual precipitation (B) across Europe. Locations of the geographic regions covered in the book are indicated. Data sources: see Appendix.

Chapter | 1 Introduction to European Rivers

FIGURE 1.6 Seasonal distribution in catchment runoff (L/s/km2) for selected rivers distributed across Europe. Runoff includes the difference between precipitation, evapotranspiration and catchment topography (Data source: Global Water Runoff Data Center, GRDC, http://grdc.bafg.de/servlet/is/2781/? lang=en).

9

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PART | I Rivers of Europe

1.8. RIVERINE FLOODPLAINS Due to the development of agriculture in alluvial plains, the transformation of rivers to waterways for navigation, and the protection of settlements, floodplains have been ‘trained’ for centuries. Today, about 50% of the total European human population lives on former floodplains. As a consequence, 50% of the original wetlands and up to 95% of riverine floodplains have been lost. In 45 European countries, 88% of the alluvial forests have disappeared from their potential range (Hughes 2003). The Seine River (France, not covered in the book) shows the highest impact of all European rivers with 99% of its former riparian floodplains lost. Of the former 26 000 km2 floodplain area along the Danube and its major tributaries, 20 000 km2 have been isolated by levees and have thus become ‘functionally’ lost; meaning that the basic attributes that sustain floodplains such as regular flooding and morphological dynamics are missing (Klimo & Hager 2001). Switzerland has lost about 95% of its original floodplains over the last two centuries. The remaining floodplains included in the inventory of ‘floodplains of national importance’ are far from being pristine, being heavily influenced by water abstraction, gravel mining, and fragmentation. Today, the largest remaining floodplain fragment in Switzerland covers an area of only 3 km2. Because most European floodplains are already ‘cultivated’, even impacted systems that retain some natural functions, such as those along the Oder River (Poland/Germany), the Danube River, and eastern European river corridors, are extremely important to protect. This is especially true for river corridors in Eastern Europe because of ever

increasing pressures from development (gravel exploitation, damming, dredging for navigation, road construction) (Tockner & Stanford 2002).

1.9. RIVER DELTAS Deltas are integral features of many catchments, being important depositional landforms where the river mouth flows into an ocean, sea or lake. The geometry, landform, and environment of deltas result from the accumulation of sediments added by the river and the reworking of these sediments by marine or lake forces. Because many European rivers discharge into isolated, inland seas (Baltic, Black and Mediterranean Seas) characterized by low tides and moderate wave powers, they can form extensive deltas (Table 1.2, Figure 1.7). 35 important European deltas cover a total area of 90 000 km2. Despite their ecological and socioeconomic importance, European deltas are among the least investigated aquatic ecosystems. Deltas are highly productive environments and, as a consequence, they have been extensively transformed into cropland and urban areas. Today, the human density in European deltas is often much higher than in respective upstream catchment (Tables 1.1 and 1.2), although the opposite pattern can be found such as for the Danube and some tributaries to the White Sea. Deltas formed by the Pechora, the Northern Dvina (despite having a large seaport, Archangelsk, with a population of 350 000), and the Volga are among the few remaining relatively pristine deltas. Deltas are biologically diverse ecosystems, thus major efforts are underway to conserve and

TABLE 1.2 Twenty of the largest river deltas in Europe (including Turkey and the Caucasus).

Rhine Volga Ural Pechora Kuban Danube Kura Terek Po Dnieper N Dvina Guadalquivir Seyhan Vistula Rhone Nemunas Don Kızılırmak Ebro Nestos

Area (km2)

Average temperature ( C)

Population (people/km2)

Arable and Pasture (%)

Protected (%)

25 347 11 446 8586 5490 5422 4560 4175 4026 2878 2833 2229 2213 1903 1858 1783 1088 604 474 331 319

9.2 10.3 9.1 4.0 11.7 10.7 15.5 11.6 12.8 8.7 0.6 17.6 17.1 7.7 13.5 6.7 10.1 11.1 15.9 12.5

492 53 24 <1 63 34 78 46 119 80 118 152 116 187 64 24 541 126 116 53

66.2 68.4 49.0 1.4 51.5 24.0 17.6 76.1 83.8 78.8 29.5 60.8 46.8 85.7 56.9 60.0 40.9 3.8 82.2 29.5

0.9 24.7 <0.1 26.3 20.3 89.1 20.6 3.3 10.0 7.4 5.9 31.9 <0.1 <0.1 59.7 18.6 80.8 <0.1 22.3 14.6

Average annual temperature (1961–1990). Human population density: people per km2. Protected: National parks, Ramsar sites, National nature reserves, and other nationally protected areas. For data sources and detailed explanation see Appendix.

Chapter | 1 Introduction to European Rivers

11

FIGURE 1.7 Spatial distribution of 35 important European river deltas (K. Tockner et al., unpublished data). The delimitation of each delta is based on published literature, expert opinion, and a river networks DEM.

restore them. Several large deltas are already protected by the Ramsar Convention (e.g. Nestos, Axios, Kuban, Dnieper, Volga, Danube, Rhone). Around 90% of the Danube delta today is officially protected (Ramsar site and Unesco Biosphere heritage) (e.g. RIZA 2000). Other large deltas such as the Ural, Seyhan, Vistula, and Kizilirmak are not protected.

1.10. WATER QUALITY European rivers show a wide variety of pollution problems (Van Dijk et al. 1994; Kimstach et al. 1998; UNEP 2004). In Scandinavian rivers, acidification remains a major problem due to acid rain deposition that is not neutralized

by the non-carbonated soils of the Scandinavian Shield, while other contaminants are relatively minor. Eutrophication and nitrate deposition pose the greatest challenge in western and central Europe, whereas organic matter loads, pesticides, and nitrogen inputs are major issues in southern and eastern Europe. From 1992 to 1996, over 65% of European rivers had average annual nitrate-N concentrations exceeding 1 mg/L and 15% of the rivers had concentrations >7.5 mg/L. The highest nitrate concentrations are in northwest Europe where agriculture is intense. Ammonium levels have decreased in European rivers since around 1990. Phosphorous concentrations also have generally declined since the 1990s as a result of reductions in organic matter and phosphorous loads from wastewater treatment plants and industry

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PART | I Rivers of Europe

TABLE 1.3 Estimated catchment yields for particulate and dissolved organic matter and nutrients for selected European rivers

Volga Danube Dnieper Don N Dvina Pechora Vistula Rhine Elbe Oder Loire Kuban Nemunas Ebro Glomma Kymijoki Po Seyhan

DIP (kg/km2/year)

DIN (kg/km2/year)

DOC (kg/km2/year)

TSS (ton/km2/year)

POC (ton/km2/year)

PN (ton/km2/year)

PP (ton/km2/year)

2.39 30.21 2.96 13.60 5.65 5.94 36.98 119.32 63.94 32.61 30.95 25.88 9.42 2.34 16.06 3.95 77.18 4.21

n.d. n.d. n.d. 19.1 n.d. 64.7 371.8 2200.4 795.4 389.8 n.d. 330.9 74.1 n.d. 191.8 n.d. n.d. n.d.

n.d. 1152 570 245 1494 1954 n.d. 1388 753 n.d. 1065 1044 n.d. n.d. n.d. n.d. 3046 n.d.

18 86 5 5 10 21 14 21 6 1 4 120 7 217 321 3 147 151

0.2 1.0 0.2 0.1 0.4 0.5 3.1 2.4 1.6 0.4 0.7 1.0 0.6 1.6 1.5 0.3 3.2 n.d.

0.0 0.1 0.0 0.0 0.1 0.1 0.4 0.4 0.2 0.1 0.1 0.2 0.1 0.2 0.2 0.1 0.4 n.d.

0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.1 0.1 0.0 0.1 n.d.

DIP: dissolved inorganic phosphorus, DIN: dissolved inorganic nitrogen, DOC: dissolved organic carbon, TSS: total suspended solids, POC: particulate organic carbon, PN: particulate nitrogen, PP: particulate phosphorus. n.d.: no data. (Sources: Beusen et al. 2005; Dumont et al. 2005; Harrison et al. 2005).

and of severe reduction or ban of phosphate detergents such as in Switzerland and Germany. However, micropllutants (e. g. pharmaceuticals, nanoparticles) impose risks to aquatic life and humans. While water quality has considerably improved over the last decades in many western European rivers, serious problems still exist in eastern and southern countries. For instance, 75% of the water in the Vistula, Poland’s largest river with many semi-natural flood plains, is unsuitable even for industrial use. The range of specific fluxes of river borne material (tons km2/year) is generally high at the continental scale, and it is even wider in Europe due to human impacts. Annual yields of total suspended solids (TSS) range over more than two orders-of-magnitude from <1 ton km2/year to >300 tons km2/year. Very high values occur in the Alps, reflecting natural erosion. Dissolved inorganic nitrogen yields from European catchments range over two ordersof-magnitude from <10 kg N km2/year for rivers in the remote north (e.g., Finish rivers) to >2200 kg N km2/year for the Rhine (Table 1.3; Beusen et al. 2005; Dumont et al. 2005; Harrison et al. 2005). Yields of dissolved organic carbon range from 200 kg C km2/year (Steppic Rivers) to >3000 kg C km2/year in the Po River (Table 1.3). Dissolved organic nitrogen, which primarily originates from anthropogenic sources in Western and Southern Europe, can reach 300 kg N km2/year. For all of Europe, estimated annual export rates were 1 Pg for inorganic suspended solids (ISS), 7 Tg for particulate organic carbon (POC), 1.1 Tg for particulate nitrogen (PN) and 0.3 Tg for particulate phosphorus (PP).

Toxic substances such as metals, polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCBs) have reached some of the highest values ever recorded for Europe. Because their survey is costly, recent trends are generally reconstructed from cores taken in deltas and floodplains. In Western European rivers, bordering the Atlantic coast, very high levels of cadmium, mercury, lead, zinc, and PAHs and PCBs have been recorded, with peaks from 1930 to 1970. Record contaminations are observed in river basins with high industrial and mining activities, and megacity inputs (e.g. Paris, Berlin), often in combination with limited dilution by river flows, such as for the Seine, the Scheldt, Lot (France), Meuse, Rhine, Idrija (Slovenia), Elbe, and Upper Vistula. In most cases the contamination levels have markedly declined since the 1970s, but they remain at high levels compared to natural levels. The heritage of this type of pollution, associated with particulate material, will last for decades and more.

1.11. FRESHWATER BIODIVERSITY The most up-to-date global inventory of freshwater animal biodiversity (Balian et al. 2008) lists 126 000 freshwater species (http://fada.biodiversity.be). In fact, the actual species richness is likely to be substantially higher. Nevertheless, European freshwaters are relatively species poor compared to other continents (Table 1.4, Illies 1978; Lev^eque et al. 2005; Balian et al. 2008). European waters provide habitat for <4% of the global freshwater fish fauna. The relative contribution of the European freshwater fauna to

13

Chapter | 1 Introduction to European Rivers

TABLE 1.4 Global and European freshwater fauna species richness (after L ev^ eque et al. 2005; Balian et al. 2008) Group

World

Europe

Proportion of global (%)

Bivalvia Gastropoda Ostracoda Copepoda Amphipoda Ephemeroptera Odonata Plecoptera Trichoptera Hemiptera Coleoptera Diptera Lepidoptera Hymenoptera Megaloptera Pisces Amphibia Aves

1000 4000 2000 2085 1700 >3000 5500 2000 >10 000 3300 >6000 >20 000 >1000 >130 300 >13 000 5504 1800

50 163 400 902 350 350 150 423 1724 129 1077 4050 5 74 6 400 74 253

5 4 20 43 21 <10 3 21 <17 4 <18 <20 <1 <56 2 <3 1 14

Total

>82 500

10 580

<13

the global fauna is higher for groups with widespread species such as copepods and ostracods. It must be noted that the freshwater fauna (and flora) of Europe is much better described than the fauna of most other areas of the world. Around 25% of all European birds and 11% of all European mammals are dependent on freshwater for breeding or feeding, but only three species are truly endemic to Europe (aquatic warbler, Acrocephalus palustris; southwestern water vole, Arvicola sapidus). Nine birds, two mammals and 200 fishes associated with European freshwaters are included in the International Union for the Conservation of Nature (IUCN) Red List of Globally Threatened Species. One success story is the recent spread of the European beaver. At the beginning of the last century only a few hundred individuals survived in Norway, Germany, France, and the former Soviet Union. The population has now increased to at least half a million, and is attributable to large areas of suitable habitats and restricted hunting. In a recent study, we compiled information on 368 native freshwater fish species from 33 families (Peter 2006). The most species (taxa) rich families were Cyprinidae (156 species), Gobiidae (40), Cobitidae (32), and Salmonidae (22; 64 species if all species and forms are considered). However, 60 new species have been described in Europe since 2000 (Kottelat & Freyhof 2007), which have contributed >10% to the known diversity (550 native species including about 200 endemic to Turkey and the southern Caucasus slopes). Projections suggest that no less than 1000 species might occur in Europe. In comparison, North America contains 1050 species, Africa >3000 species, and South America >5000 species.

In Europe, a distinct west–east and north–south increase in species richness is found. The Danube River catchment has the highest diversity with 130 fish species (including nonnative species) (25% of the continental fauna). Using area-corrected data (a power function of area and richness), the greatest diversity of fishes is in southeastern European catchments (Western Balkan, Turkey). River basins in Northern Europe, from Iceland to Northern Russia, have been covered by ice until 12 000–6000 years BP and therefore have low fish diversity. At the continental scale, 13 fish species became extinct (Kottelat & Freyhof 2007). At the catchment scale, up to 40% of native fishes have disappeared, especially long-migrating species such as sturgeons, Allis shad (Alosa alosa) and lampreys. Further, five native crayfish species, of the family Astacidae, and eight nonnative species occur in Europe. Species richness patterns differ greatly across Europe and depend on the taxonomic group considered. We compiled European-wide information on fish (542 species), dragonflies (174), amphibians (83), and wetland birds (98). While amphibians are most diverse in Mediterranean and Central European basins (up to 25 species per catchment), dragonflies (maximum 79 species per catchment) and wetland birds (maximum 80 species per catchment) are most species rich in Central and Eastern European catchments (Figure 1.8A–D). For Eastern Europe and Anatolia, information on biodiversity is highly limited and therefore we may expect an even higher species richness there. The proportion of species listed as threatened is particularly high for the Iberian Peninsula (amphibians, dragonlies, wetland birds) and in Eastern Europe (wetland birds) (Figure 1.8A–D). The proportion of fishes listed as threatened can be as high as 50% for an individual catchment.

1.12. ENVIRONMENTAL PRESSURES ON BIODIVERSITY Fragmentation, water stress, land use change, and the introduction of non-native species impose major threats on riverine biodiversity. These factors affect single or in concert almost all European rivers. Figure 1.9A–D show the spatial distribution of these four key pressures. The most stressed catchments occur in the Mediterranean area, the area that at the same time contains the highest proportion of threatened freshwater species (see Figure 1.8).

1.12.1. Fragmentation Most European rivers are heavily fragmented, with major consequences for sediment transport, nutrient delivery, and the dispersal and migration of organisms including fish (Dynesius & Nilsson 1994; Nilsson et al. 2005). Only a few Arctic and Fennoscandian rivers, with the Northern Dvina as the largest system, remain free-flowing. Fragmentation is responsible for the major decline of many longdistance migrating fish species in Europe (Peter 2006).

14

PART | I Rivers of Europe

FIGURE 1.8 Species richness and relative proportions (%) of threatened species for each individual catchment: (A) Amphibians; (B) Fish; (C) Dragonflies; (D) Wetland birds. Data sources: see Appendix. Catchments are not always identical with catchments in Figure 1.2.

Chapter | 1 Introduction to European Rivers

FIGURE 1.8 (Continued )

15

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PART | I Rivers of Europe

FIGURE 1.9 (A) Degree of fragmentation, (B) water stress as the proportion of withdrawal to availability, (C) developed area (urban, arable and pasture in % of the catchment), (D) relative proportion (%) of non-native fish species (Peter 2006). Data sources: see Appendix. Catchments are not always identical with catchments in Figure 1.2.

Chapter | 1 Introduction to European Rivers

FIGURE 1.9 (Continued )

17

18

1.12.2. Water stress A recent assessment of Europe’s environment by the European Environmental Agency indicated that high levels of water stress (calculated as the proportion of withdrawal to availability), both in quantity and quality, exist in many areas throughout Europe and identified several significant ongoing pressures on water resources at the European scale. Total water withdrawal has generally increased in the last decades. By 1995, a total of 476 3 water was being withdrawn annually; 45% of this water is used for industry, 41% for agriculture, and 14% for domestic needs (Henrichs & Alcamo 2001; Eisenreich 2005). There is a large difference between countries in how much and for what purpose water is withdrawn. Industrial uses dominate water withdrawals in most of Europe, whereas irrigation use is highest in southern and southeastern countries with low precipitation. Total withdrawal per catchment ranges from nearly zero (in the less populated areas of sub-polar Scandinavia and Russia) to >400 mm/year (in densely populated urban areas). In total, annual water withdrawal in Europe (excluding Turkey) is projected to rise from 415 km3 today to 660 km3 by 2070. Although the annual total withdrawal in Western Europe will decrease from 236 km3 to 190 km3, it will increase considerably in Eastern Europe from 180 km3 to 470 km3. In Southeastern Europe, growth in water demand is complemented by reductions in water availability due to climate change, which ultimately will increase water stress. Overall, severe water stress is predicted to increase from 19% today to 34–36% by 2070. Since 1970, the total annual discharge of Balkan rivers already decreased by up to 70%, mainly due to water abstraction for irrigation (Parry 2000; Henrichs & Alcamo 2001; Alcamo et al. 2007).

1.12.3. Land use change Among the major factors influencing water quality and quantity at the catchment scale is the change in land use intensity. Around 60% of the combined catchment area of the 164 examined rivers has been transformed into agricultural (arable and pasture) or urban area. The proportion of developed area exceeds 90% for Central European and Western Steppic River catchments (Table 1.1). Over 70% of the European population lives in urban areas and the total number of cities with a population >100 000 equals 350.

1.12.4. Non-native fish species A total of 76 non-native fishes belonging to 21 families have been introduced into European freshwaters, with 29 of these having self-reproducing populations. Most non-native fishes originated from North America (34 species) and from Asia (26 species), and between 30 and 50 fishes have been translocated within Europe. The proportion of non-native fish exceeds 40% in some catchments, mostly in the Iberian Peninsula and the Atlantic region of France (Peter 2006).

PART | I Rivers of Europe

The Iberian Peninsula, the southern Balkan, and Anatolia will face an even higher increase in water stress, pollution, and erosion in the near future. These areas probably will require the highest priority in respect to freshwater biodiversity conservation and restoration. Interestingly, only two freshwater fish species endemic to Anatolia are extinct. In both cases it was the consequence of the introduction of an alien predatory fish introduced for commercial fisheries.

1.13. THE EUROPEAN WATER FRAMEWORK DIRECTIVE European catchments are under pressure of ever increasing water stress and land-use change, especially those with high conservation value such as in the Mediterranean area. The Water Framework Directive (WFD) creates a legislative framework to manage, use, protect, and restore surface water and groundwater resources in the European Union. The WFD approaches water management at the scale of the river catchment (river basin), which often includes several countries. The WFD requires the establishment of a ‘river basin management plan’ (RBMP) for each river catchment in the European Union. The RBMP is a detailed account of how environmental objectives (i.e. good ecological status of natural water bodies and good ecological potential of heavily modified and artificial water bodies) are to be achieved by 2015. For those countries that can demonstrate that this is not feasible without disproportionate economic and social costs, the WFD allows the possibility of delay until 2030. This sets a time scale for restoration of water bodies during which a considerable change in climate is expected. Although it is stated ‘this Directive should provide mechanisms to address obstacles to progress in improving water status when these fall outside the scope of Community water legislation, with a view to developing appropriate Community strategies for overcoming them’ (WFD, Article 47), climate change and its possible impact on water bodies has been ignored in the scope of the WFD and the term ‘climate’ does not even appear in its text.

1.14. KNOWLEDGE GAPS The catchment must be considered as the key spatial unit to understand and manage ecosystem processes and biodiversity patterns. However, biological information is mostly available at the country rather than the catchment level. In addition, available data are unevenly distributed across Europe and limits potential comparability. Riverine floodplains and deltas are among the least studied ecosystems but yet are the most threatened. As such, we need to identify and quantify the ecosystem services that these ecosystems provide in their natural state. Historic information and long-term data for freshwater organisms as well as key environmental drivers (e.g. temperature, habitat change) are rare, especially at

19

Chapter | 1 Introduction to European Rivers

the continental scale. While conservation planning is primarily driven by the number of native, endemic and endangered species (so-called ‘hot spot’ areas), there is an urgent need to incorporate other ecosystem aspects such as the evolutionary potential of the system and its capacity to perform key ecological processes in conservation and restoration planning. Finally, there is an urgent need to establish a European network of ‘reference’ river systems against which human alterations can be assessed; and to better understand how rivers function in their (semi-)natural state. This provides pivotal baseline information for guiding future restoration and management programs.

Human population density

Land use

APPENDIX Air temperature

Amphibians Annual gross domestic product (GDP) Biogeographical regions

Catchment area

Catchment elevation

Discharge Dragonflies Ecological regions

Fish Fragmentation

Data derived from: CRU Global Climate Dataset. Monthly mean values from 1961 to 1990. Resolution: 10 000 m 10 000 m. http://www.ipcc-data.org/obs/ get_30yr_means.html. http://www.globalamphibians. Data derived form ESRIÒ Data & Maps, 2004. Resolution: 1000 m 1000 m. Data derived from: http:// dataservice.eea.europa.eu/ dataservice/metadetails.asp? id=308. The delimitation of each catchment is based on the CCM river and catchment database JRC/IES Ó European Commission, 2003, http://agrienv. jrc.it/activities/catchments/ccm. html, the HYDRO1k drainage basins database http://edc.usgs. gov/products/elevation/gtopo30/ hydro/index.html, published literature, expert opinion, and a river networks DEM. DEM derived from the USGS’ 30 arc-second digital elevation model of the world (GTOPO 30). Resolution: 1000 m 1000 m. http://edcdaac.usgs.gov/gtopo30/ hydro/index.asp. Data from experts (authors). Data kindly compiled by V. Kalkman. Data after Olson et al. (2001). http://www.worldwildlife.org/ science/data/item1875.html. Resolution: 1000 m 1000 m. Data from experts (authors). Peter (2006). Calculated after Dynesius & Nilsson (1994); Nilsson et al. (2005). Three fragmentation categories.1: Not affected; 2: Moderately affected; 3: Strongly affected.

Large cities

Large dams Precipitation

Protected area

Temperatue Threatened species Water stress

Wetland birds

Data derived from the population density grid for the year 2000 adjusted to match UN totals, persons per square km. Gridded Population of the World, Version 3 (GPWv3); 2005; Center for International Earth Science Information Network (CIESIN), Columbia University; Centro Internacional de Agricultura Tropical (CIAT). http://sedac.ciesin.columbia. edu/gpw/. Resolution: 5000 m 5000 m. Data checked by experts (authors) and changed if necessary. Modified landcover derived from USGS with classification according to International Geosphere Biosphere Programme (IGBP), 1992/1993. http://edcsns17.cr.usgs.gov/glcc/ tablambert_euras_eur.html. The original 17 classes were reclassified in 8 classes: urban, grasland, cropland, shrub, forest, barren, wetland, waterbody. Resolution: 1000 m 1000 m. Data checked by experts (authors) and changed if necessary. Cities with more than 100 000 inhabitants. Derived from cities of Europe and cities of the world. ESRIÒ Data & Maps, 2004. Dams higher than 15 m. Data from experts (authors). Data derived from: CRU Global Climate Dataset. Monthly mean values from 1961 to 1990. Resolution: 10 000 m 10 000 m. http://www.ipcc-data.org/obs/ get_30yr_means.html.x. Sum of % of the total catchment area of Ramsar sites, national parks, national nature reserves, and other nationally protected areas. Modified data derived from the world databas on protected areas (WCPA), 2005. http://sea.unep-wcmc.org/ wdbpa/. Resolution: 100 m 100 m. Data checked by experts (authors) and changed if necessary. See precipitation Data according to the IUCN Red List. www.iucn.org. for each. Data derived from Alcamo et al. (2007). Three water stress categories: Low (1), Middle (2) and Severe (3). Electronic data from Hagemeijer, J.M., and Ward, J.M (1997). The EBCC atlas of European breeding birds. ISBN 0-85661-091-7.

20

The coarse resolution of some of the data presented in the tables (e.g. human population density, precipitation and temperature) was chosen to be consistent from the Atlantic to the Ural).

Acknowledgements We would like to thank Verena Keller, Schweizerische Vogelwarte, Sempach, for her support in collecting data on wetland birds, and we are particularly grateful to Vincent Kalkman, European Invertebrate Survey – Nederland Nationaal Natuurhistorisch Museum – and Chair for the IUCN Odonata Specialist Group, for the compilation of the odonata data. Further support was from Sonia Ferreira, Cosmin-Ovidiu Manci, Elena Dyatlova, Milen Marinov, Otakar Holusa, Milos Jovic and Vladimir Skvortsov.

REFERENCES Alcamo, J., Fl€ orke, M., and M€arkle, M. 2007. Future long-term changes in global water resources driven by socio-economic and climatic changes. Hydrological Sciences Journal – Journal des Sciences Hydrologiques 52: 247–275. Bacci, M.L. 1998. Europa und seine Menschen. Eine Bev€ olkerungsgeschichte. Verlag C.H. Beck, M€unchen. Balian, E.V., Lev^eque, C., Segers, H., and Martens, K. 2008. (eds). Freshwater Animal Diversity Assessment. Development in Hydrobiology, vol. 198. Springer. Beusen, A.H.W., Dekkers, A.L.M., Bouwman, A.F., Ludwig, W., and Harrison, J. 2005. Estimation of global river transport of sediments and associated particulate C, N, and P. Global Biogeochemical Cycles 19, GB4S05. Butlin, R.A. and Dodgson, R.A. (eds). 1998. An Historical Geography of Europe, Clarendon Press, Oxford. Dumont, E., Harrison, J.A., Kroeze, C., Bakker, E.J., and Seitzinger, S.P. 2005. Global distribution and sources of dissolved inorganic nitrogen export to the coastal zone: results from a spatially explicit, global model. Global Biogeochemical Cycles 19, GB4S02. Dynesius, M., and Nilsson, C. 1994. Fragmentation and flow regulation of river systems in the northern third of the World. Science 266: 753–762. Eisenreich, S.J. (ed). 2005. Climate Change and the European Water Dimension: A Report to the European Water Directors, Ispra, Italyhttp://natural-hazards.jrc.it. Harrison, J.A., Caraco, N., and Seitzinger, S.P. 2005. Global patterns and sources of dissolved organic matter export to the coastal zones: results from a spatially explicit, global model. Global Biogeochemical Cycles 19, GB4S04. Henrichs, T., and Alcamo, J., 2001. Europe’s Water Stress Today and in the Future (http://www.usf.unikassel.de/usf/archiv/dokumente/kwws/5/ ew_5_waterstress_low.pdf). Hughes, F.M.R. (ed). 2003. The Flooded Forest: Guidance for Policy Makers and River Managers in Europe on the Restoration of Floodplain Forests. FLOBAR2, European Union and Department of Geography, University of Cambridge UK, 96 pp. Hughes, J.D. (ed). 2001. An Environmental History of the World, Routledge, London. Illies, J. 1978. Limnofauna Europaea – Eine Zusammenstellung aller die europ€ aischen Binnengew€ asser bewohnenden mehrzelligen Tierarten € mit Angaben u€ber ihre Verbreitung und Okologie. Schweitzerbart’sche Verlagsgesellschaft, Stuttgart.

PART | I Rivers of Europe

Kimstach, V. Meybeck, M. and Boroody, E. (eds). 1998. A Water Quality Assessment of the Former Soviet Union, E & F Spoon, London. Klimo, E. and Hager, H. (eds). 2001. The Floodplain Forests in Europe, Brill, Leiden, The Netherlands. Kottelat, M., and Freyhof, J. 2007. Handbook of European Freshwater Fishes. Kottelat, Cornol and Freyhof, Berlin. Kristensen, P., and Hansen, H.O. (eds). 1994. European Rivers and Lakes – Assessment of their Environmental State. EEA Environmental Monographs, vol. 1, EEA, Copenhagen. Lev^eque, C., Balian, E.V., and Martens, K. 2005. An assessment of animal species diversity in continental waters. Hydrobiologia 542: 39–67. Menot, G., Edouard Bard, E., Rostek, F. et al. 2006. Early reactivation of European Rivers during the last deglaciation. Science 313: 1623–1625. Nilsson, C., Reidy, C.A., Dynesius, M., and Revenga, C. 2005. Fragmentation and flow regulation of the world’s large river systems. Science 308: 405–408. Olson, D.M., Dinerstein, E., Wikramanayake, E.D., Burgess, N.D., Powell, G.V.N., Underwood, E.C., D’amico, J.A., Itoua, I., Strand, H.E., Morrison, J.C., Loucks, C.J., Allnutt, T.F., Ricketts, T.H., Kura, Y., Lamoreux, J.F., Wettengel, W.W., Hedao, P., and Kassem, K.R. 2001. Terrestrial ecoregions of the world: a new map of life on earth. BioScience 51: 933–938. Parry, M. (ed). 2000. The Europe ACACIA project: Assessment of Potential Effects and Adaptations for Climate Change in Europe, Jackson Environment Institute, Norwich (UK). Peter, F., 2006. Biodiversity of European Freshwater Fish – Threats and Conservation Priorities at the Catchment Scale. Diploma thesis. University of Basel, Switzerland, 71 pp. Petts, G.E. M€oller, H. and Roux, A.L. (eds). 1989. Historic Changes of Large Alluvial Rivers: Western Europe, John Wiley & Sons, Chichester. RIZA, 2000. Ecological gradients in the Danube Delta Lakes. RIZA Report 2000.015, The Netherlands (ISBN 90.369.5309x). Shiklomanov, I. 1997. Assessment of Water Resources and Water Availability of the World. Stockholm Environment Institute, Stockholm (Sweden). Stanners, D., and Bourdeau, P. 1995. Europe’s Environment – The Dobris Assessment. Earthscan Publications, London. Starkel, L. 1991. Long-distance correlation of the fluvial events in the temperate zone. In: Starkel, L., Gregory, K.J., Thornes, T.B. (eds). Temperate Palaeohydrology, John Wiley & Sons, Chichester, pp. 473–495. Starkel, L. Gregory, K.J. and Thornes, J.B. (eds). 1991. Temperate Palaeohydrology, John Wiley & Sons, Chichester. Tockner, K., and Stanford, J.A. 2002. Riverine floodplains: present state and future trends. Environmental Conservation 28: 308–330. UNEP, 2004. Freshwater in Europe – Facts, Figures and Maps United Nations Environment Programme/Division of Early Warning and Assessment – Europe. Chatelaine, Switzerland, 92 pp. Van Dijk, G.M., Van Liere, L., Bannik, B.A., and Cappon, J.J. 1994. Present state of the water quality of European rivers and implications for management. The Science of the Total Environment 145: 187–195. Whitton, B.A. 1984. Ecology of European Rivers. Blackwell, Oxford, UK.

FURTHER READING Kottelat, M. 1997. European freshwater fishes: An heuristic checklist of the freshwater fishes of Europe (exclusive of former USSR), with an introduction for non-systematists and comments on nomenclature and conservation. Biologia 52: 1–271.

Chapter | 1 Introduction to European Rivers

RELEVANT WEBSITES http://ec.europa.eu/environment/index_en.htm – European Commission. http://www.jrc.ec.europa.eu/ – EC Joined Research Center. http://www.ecnc.nl – European Centre for Nature Conservation. http://www.ecrr.org/ – European Center for River Restoration.

21

http://www.grid.unep.ch/ – United Nations Environment Programme/Division of Early Warning and Assessment. http://www.GWSC.bafgf.de/ – Global Runoff Data Center (GRDC). http://www.gwsp.org – ESSP Global Water System Project (GWSP). http://ec.europa.eu/environment/water/water-framework/index_en.html) – Water Framework Directive (WFD).

Chapter 2

Volga River Basin Alexander S. Litvinov

Natalya M. Mineeva

Vladimir G. Papchenkov

I.D. Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia

I.D. Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia

I.D. Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia

Ludmila G. Korneva

Valentina I. Lazareva

Grigory Kh. Shcherbina

I.D. Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia

I.D. Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia

I.D. Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia

Yuri V. Gerasimov

Svetlana A. Dvinskikh

Victor M. Noskov

I.D. Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl, Russia

Permsky State University, Perm’, Russia

Permsky State University, Perm’, Russia

Alexander B. Kitaev

Margarita S. Alexevnina

Elena V. Presnova

Permsky State University, Perm’, Russia

Permsky State University, Perm’, Russia

Permsky State University, Perm’, Russia

Elena B. Seletkova

Euvgeny A. Zinov’ev

Mikhail A. Baklanov

Permsky State University, Perm’, Russia

Permsky State University, Perm’, Russia

Permsky State University, Perm’, Russia

Alexander G. Okhapkin

Galina V. Shurganova

Nizhegorodski State University, Nizhni Novgorod, Russia

Nizhegorodski State University, Nizhni Novgorod, Russia

2.1. 2.2. 2.3. 2.4.

2.5.

2.6.

2.7.

2.8.

Introduction Human History Biogeographical Setting 2.3.1. Paleogeography of the Basin Physiography and Climate 2.4.1. Geological Structure and Relief 2.4.2. Climate Geomorphology, Hydrology, and Biogeochemistry 2.5.1. Geomorphic Development of the Main Corridor 2.5.2. Hydrology 2.5.3. Biogeochemistry Aquatic and Riparian Biodiversity 2.6.1. Upper Volga 2.6.2. Middle Volga 2.6.3. Lower Volga Management and Conservation 2.7.1. Economic Importance 2.7.2. Conservation and Restoration Conclusions and Perspectives

Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

2.9.

Major Tributaries of the Volga River 2.9.1. The River Kama 2.9.2. The River Oka 2.9.3. The River Sheksna References

2.1. INTRODUCTION The Volga River, at 3690 km, is the longest river in Europe and 16th in the world. The Volga ranks 5th in Russia, following the Ob’, Yenisey, Lena and Amur in Siberia. The Volga flows into the Caspian Sea, the largest inland sea on earth (Figure 2.1). There are about 151 000 rivers >10 km in length within the Volga catchment. Of these, 2600 flow into the Volga directly and the Kama, Oka and Sheksna Rivers are the largest (Butorin & Mordukhai-Boltovskoy 1979). The 1.4 million km2 catchment area of the Volga drains about 33% of European Russia, covering various biomes from taiga to semi-desert. The most northern point is at the source of the Visherka River in the Kama River basin at latitude 61 550 N, and the southern border runs along the outer edge 23

24

FIGURE 2.1 Digital elevation model (upper panel) and drainage network (lower panel) of Volga River Basin.

PART | I Rivers of Europe

25

Chapter | 2 Volga River Basin

of the Volga delta at 45 350 N. Its western border is at longitude 32 050 E and the eastern border is at 60 220 E (Butorin & Mordukhai-Boltovskoy 1979). Historically, the Volga has attracted the attention of many scientists from different fields, resulting in many publications. The present chapter was based on these papers, although much of the principal information has been summarized previously in the monograph The River Volga and its Life published in Russian (1978) and later translated into English (Butorin & Mordukhai-Boltovskoy 1979). The basic geographical and historical material used in this chapter was prepared using this monograph as well as material from the Grand Soviet Encyclopedia (Shmidt 1928a), Encyclopedic Dictionary (Belevsky 1892), and the open-access internet site Wikipedia (http://ru.wikipedia.org/).

2.2. HUMAN HISTORY Initial records of the Volga were found in the works of the ancient Greek historian, Herodotus, in 500 BC. In ancient history, the Volga was known as the Atil, Itil or Idil, a Turkish name meaning ‘long river’ or ‘river of rivers’. The ancient scholar Ptolemy of Alexandria mentions the lower Volga in his Geography, calling it the Rha «generous». ‘Volga’ is probably a Slavicization of proto-Baltic meaning ‘long river’, ‘bright river’, ‘holy river’ or ‘Mother Volga’. The Volga is considered to be the national property of Russia, often emotionally included in Russian songs, literature, films, and the fine arts. The geographical situation of the Volga promoted human colonization by various nations, and played an important role in the movement of people between east and west (from Asia to Europe) as well as south and north. The first humans in the Volga region are thought to be from the late Stone Age. The southern part of the Volga region was inhabited initially by nomadic tribes: Scythians, then Sarmatae, and since 400 AD by emigrants from Asia. Huns arrived in 500–600 AD, Bulgarians occupied the middle region of the Volga, and Khazar Khaganate was formed in the lower Volga region in 700 AD. The Slavonic Vyatichi, Olyane, Radimichi, Severyane tribes inhabited the upper region of the catchment. In 1000 AD, new nationalities colonized the lower Volga region from the Urals, Ugrs arrived from the Oka and Don basins, Pechenegs in 1000 AD and Polovtsy in 1100 AD. Following the Khazar Khaganate decline, a Bulgarian empire flourished where the river Kama joins the Volga. By the end of 1100 AD, Slavs along with the Finnish tribes Ves’, Merya, Muroma, Cheremis and Mordva lived in the Oka, Kama and Vyatka regions of the upper Volga. In the beginning of the 13th century, Tatar-Mongols occupied the lower and middle Volga regions. Around 1240, a Mongol state, the Golden Horde, was established and endured up to the 16th century. The Kazan Khanate with its capital in Kazan was part of this state in the middle Volga from 1438 to 1552. The Russian state became prominent from the middle of the 15th

century, that is Muscovite Russia gained independence from the Tatars in 1480. From 1721 to 1918, the Russian state was officially named the Russian Empire, and the Russian Federation since 1918 (the Soviet Union from 1922 to 1991). The Volga region was important in various wars: peasant wars as well as revolts of peasants and Cossacks under the leadership of Stepan Razin and Yemelyan Pugachev in the 17th–18th century, the Civil War of 1917–1922, and the Battle of Stalingrad in 1942–1943 during World War II. The present ethnographic composition of the Volga region consists of Indo-European (Russian majority, Ukrainians, Germans, Belorussians, Poles, Latvians), Finnish (Votyaks, Permyaks, Chemerisis, Mordvas, Karels) and Turkish (Bashkirs, Kyrgyzs, Tatars, Chuvashs) peoples. Kalmyks, representatives of Mongol nationality, form a separate group. As of this writing, the Volga basin is divided into three sections referred to as the upper, middle, and lower Volga. Gorky dam and Kuibyshev dam are considered the border of the upper and middle Volga, and the middle and lower Volga, respectively. The present chapter includes subsections describing each region of the Volga, along with separate sections on its largest tributaries: Kama, Oka and Sheksna.

2.3. BIOGEOGRAPHICAL SETTING The Volga catchment is on the Russian plain, encompassing various latitudinal climatic zones. Atmospheric circulation and input of solar radiation increases from north to south (Pivovarova & Stadnik 1988), and is strongly influenced from air masses generated by the Atlantic Ocean. Longitudinal zonation is emphasized by the transgression from taiga to semi-desert, incorporating local human influences. The northern part of the catchment is in a forest belt that includes southern taiga and mixed coniferous–deciduous forests. The south/southeast of this forest belt includes the forest-steppe biome, and even farther south are found steppe, semi-desert, and desert biomes. The desert biome is found only near Caspian lowlands adjacent to the southern Akhtuba floodplain. The Akhtuba floodplain and the Volga delta are intra-zonal geographical regions, in sharp contrast to the desert belt.

2.3.1. Paleogeography of the Basin The modern Volga River valley was formed in the postglacial period, and the hydrographic network of the Russian plain was transformed during different geologic epochs. Tectogenesis of the Russian plain in the southeast from geosynclines to platform occurred in the Paleozoic, giving rise to a meridian flexure. The most intensive formation was in the Age of Reptiles (Obidientova 1975). By the end of the Tertiary, the size and contour of the Ancient Sea (i.e. area of the modern Caspian Sea) changed several times. Regressions and transgressions of the Caspian Sea as well as modifications in principal watershed arrangement of the Russian

26

plain continued into the Quaternary and Holocene. The Paleo-Volga and Paleo-Kama were the main rivers to transverse the eastern part of the Russian plain at this time. The Oka glaciation began about 700 000 years ago, lasting about 200 000 years, and was the first glaciation of the Volga River catchment. At this time, the formation of the Caspian Sea began as well as the first Quaternary Caspian transgressions (Baku transgressions). During the last glaciation, the Valdai glaciation about 10 000 years ago, only a small area of the Volga River catchment bordered by the Valdai Hills was covered by ice. Fluctuations in the Caspian Sea since the end of the Khvalynsk transgression up to the present have been the most important post-glacial changes in the Volga River catchment. There have been times in the past 200 years when the Caspian Sea was lower than today, the greatest decrease took place in the 5th and 6th century. The highest levels of the Caspian Sea, called the new Caspian transgression, were observed in the 14th–16th century, and especially in the early 19th century. An increase in sea level has occurred since 1990s.

2.4. PHYSIOGRAPHY AND CLIMATE 2.4.1. Geological Structure and Relief The Russian plain is derived of Precambrian crystalline rocks, and covered by a thick layer of sedimentary rocks within the boundaries of the Volga catchment. This sedimentary layer exceeds 3000 m around the Moscow syncline, reaches 8000 m along the Glasov syncline near the Urals, and 10 000 m near the Caspian. The lowlands, at <200 m asl, occupy about 65% of the Volga catchment. Upland areas in the lowlands rarely exceed 200–250 m asl, although reaching 350–400 m at some points, and delineate the various sub-basins of the Volga. The Valdai Hills began forming in the middle Carbon period with a second lift occurring in the middle Pleistocene. The highest peak of the Valdai Hills is at 346 m asl at the head of the Tsna River that flows into Vyshnevolotskoe reservoir. The landscape of the Valdai Hills bear imprints of glaciation that ended some 15 000 years ago, including numerous lakes. Forests cover >60% of the area, and arable land is insignificant. The Valdai Hills reside mostly in the coniferous–deciduous forest biome with a small part in the taiga biome in the north. The soil is stony and there are ‘erratic blocks’ typical of terminal glacial moraines. Running from north to south, the Volga folds and forms a flexure referred to as the ‘seam’ of the Russian plain. A narrow nearVolga trough extends from Kazan south to Volgograd where it expands and disappears in the vast pre-Caspian lowland. The Volga presently flows through this trough, taking the same course as its predecessor, the Paleo-Volga. Areas of the near-Volga upland are distinctive, being best represented by the characteristic Zhiguli Hills. They are a fault mountain range, 75 km long and up to 370 m asl,

PART | I Rivers of Europe

situated in the Samara Bend (Samarskaya Luka) of the Volga. The Paleogene Sea was present here in the beginning of the Cenozoic. The northern slope of the Zhiguli Hills is covered with deciduous and pine forests, alternating with forest-steppe along the southern slope. In the west, the near-Volga upland gradually enters the Oka-Don lowlands. The Volga floodplain extends over the lowland, replacing the ancient synclines of the Russian plain. Flowing from the Valdai Hills, the Volga enters the Volga lowlands. After crossing the southern Mologa-Sheksna depression, it flows through several interconnected lowlands: YaroslavlKostroma, Unzha, Balakhna, Mari, Zavolzhye, and the nearCaspian. The Volga cuts through adjacent uplands near Plyos and Samarskaya Luka.

2.4.2. Climate Climate of the upper Volga basin is moderate continental, characterized by above freezing air temperature for 7 months from spring through autumn and below freezing temperature for 3–4 months in winter. Mean annual air temperature decreases from 3.4 C in the west to 2.8 C in the east of the catchment. The warmest month is July, averaging 16.7– 19.2 C, whereas January is the coldest month with mean temperatures ranging from 10.1 to 13.4 C. Annual precipitation varies from 548 to 706 mm, although extremes of 1.5 times those values can occur during wet or dry periods. Maximum rainfall occurs in summer, and relative humidity varies from 55–75% in spring to 70–90% in winter. Southerly, westerly and north-westerly winds prevail, increasing from west to east. Monthly average wind-speeds reach 3 m/s, being relatively constant in spring and summer and increasing sharply in autumn and winter. The climate of the middle Volga basin is similar to that of the upper basin in winter, but the summer climate is about three times less variable. Mean annual air temperature varies from 3.1 C in the north to 5.3 C in the south. Below freezing air temperatures average 161 days in the north and 147 days in the south. The coldest month is January with average temperatures of 12.5 to 14.2 C, while July is the warmest month with average temperatures of 19.5–21.5 C. Relative humidity ranges from 50% in May to 90% in November and December. Annual precipitation ranges from 282 mm in the south to 626 mm in the north. Minimum precipitation occurs from January to April and maximum from August to November. Westerly winds with velocities up to 5 m/s are the most common (42%), although southerly winds (48%) prevail during winter and westerly winds (46%) during summer. Climate of the lower Volga basin is mostly continental, as the influence of the Caspian Sea is insignificant. Mean air temperature in the north and south varies from 9.6 and 6.9 C, respectively, in January to 20.6 and 25.1 C, respectively, in July. Easterly and south-easterly winds are predominant, bringing inland air masses and reducing the relative humidity. Mean annual precipitation ranges from 340 mm in the north to 175 mm in the south.

Upper Volga Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25%) ecological regions Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparce vegetation Wetland Fresh waterbodies Protected area (% of catchment) Water stress (1–3) 1995 2070 Fragmentation (1–3) Number of large dams (>15 m) Native fish species Nonnative fish species Large cities (>100 000) Human population density (people/km2) Annual GDP ($ per person)

Middle Volga

Lower Volga

Mologa Sheksna (Upper (Upper Volga) Volga)

162 201 88 150 236 268 973 712 221 316 37 462 49.57 244.40 253.86 7.47 66.1 58.7 40.5 69.1 3.5 3.1 6.4 3.6 2 8 4 2 59; 60 28; 59 55 60

145 19 445 5.68 63.1 3.1 1 60

Unzha Oka (Upper (Middle Volga) Volga)

Sura Vetluga Kama (Middle (Middle (Middle Volga) Volga) Volga)

Samara Bol’shoi Irgiz (Lower (Lower Volga) Volga)

158 28 941 4.98 61.6 2.8 2 60

201 67 018 6.69 55.1 4.4 3 28

143 38 974 8.04 59.9 3.1 2 60

160 46 950 1.58 47.3 4.3 2 55

89 24 542 1.12 42.3 5.7 1 55

169 245 000 39.2 60.5 4.8 4 28; 59

233 516 891 104.07 58.7 2.0 7 60

0.3 24.4 6.7 57.6 0.0 0.0 6.5 4.5

1.1 49.5 0.2 46.2 1.5 0.0 0.0 1.5

1.1 54.8 21.5 16.6 2.4 0.0 0.0 3.6

0.1 24.5 7.3 48.5 0.0 0.0 14.5 5.1

0.2 24.5 0.7 54.8 0.0 0.0 3.7 16.1

0.2 12.4 0.2 85.7 0.0 0.0 0.9 0.6

2.1 53.6 10.3 32.1 0.0 0.0 1.5 0.4

1.2 71.9 0.1 25.8 0.9 0.0 0.0 0.1

0.5 31.5 2.0 61.7 0.0 0.0 4.3 0.0

0.5 35.2 0.2 61.6 1.0 0.0 0.0 1.5

1.0 73.5 3.7 19.2 2.4 0.0 0.0 0.2

0.6 40.6 36.1 19.8 2.6 0.0 0.0 0.3

6.1

5.2

7.0

8.0

11.7

3.1

5.1

4.2

2.9

5.1

1.7

5.1

1.0 1.0 3 4 42 14 2 23 3137

1.3 1.3 3 2 45 19 18 52 2206

1.3 1.3 3 2 45 17 8 40 2045

1.1 1.1 1 0 n.d. n.d. 2 38 1727

1.0 1.0 1 0 n.d. n.d. 0 9 2188

1.0 1.0 1 0 n.d. n.d. 2 27 2149

1.1 1.1 1 0 n.d. n.d. 0 9 2016

1.0 1.0 1 0 n.d. n.d. 0 9 2916

1.0 1.0 3 1 21 1 0 29 3058

1.0 1.0 1 0 n.d. n.d. 0 5 3138

2.0 2.0 1 0 30 9 10 113 2882

1.0 1.0 3 3 36 5 6 56 2027

Chapter | 2 Volga River Basin

TABLE 2.1 General characterization of the Volga River Basin

n.d.: No data. For data sources and detailed explanation see Chapter 1.

27

28

2.5. GEOMORPHOLOGY, HYDROLOGY, AND BIOGEOCHEMISTRY 2.5.1. Geomorphic Development of the Main Corridor The river network of the Volga looks like a branching tree in the north that evolves into a single trunk rooting as a delta in the Caspian Sea in the south. The lower Volga is divided into many side-arms and the 515-km long Akhtuba is the largest. The delta at the confluence of the Volga and Caspian Sea occupies a total area of 11 446 km2. Twelve large reservoirs with a total storage of 168 km3 and total area >23 000 km2 are found in the catchment, nine of these directly on the Volga River (Table 2.1). Most of the Volga from the town of Tver’ to Volgograd is affected by an uninterrupted cascade of eight large shallow reservoirs, considerably slowing the flow velocity of the river. The reservoirs differ in terms of morphometry, optical regime, chemistry, lateral inflow, water exchange and trophic status (Avakyan et al. 1987; Butorin & Mordukhai-Boltovskoy 1979; Mineeva 2004).

2.5.1.1 The Upper Volga The Upper basin is boreal, covering about 236 000 km2. The source of the Volga is in the Valdai Hills at 228 m asl, occurring as a small brook flowing from a bog through the lakes Malyi Verkhit and Bolshoi Verkhit. It then flows through a chain of lakes (Sterzh, Vselug, Peno and Volgo) that form Verhnevolzhskoe reservoir used to store water for navigation in the Upper Volga. The Verhnevolzhskaya dam was built below Lake Volgo in 1843, and completely rebuilt in

PART | I Rivers of Europe

1943–1947. Major rivers flowing into Verhnevolzhskoe reservoir include the Runa, Kud’ and Zhukopa. Below Verhnevolzhskaya dam the Volga flows through the Valdai Hills, decreasing from 200 to 150 m asl within 70 km. The Volga between Selizharovka junction and the lowlands is known as the rapids, having >20 rapids and shallows. The Volga enters the Verhnevolzhskaya lowland downstream of the town of Rzhev, becoming relatively rich in water. Below the mouth of the river Vazuza, the Volga turns sharply to the north and then northeast, flowing through the vast Verhnevolzhskaya lowland within the coniferous broad-leaf forest biome. The next 145 km of the Upper Volga reside in Ivankovo reservoir (Photo 2.1), the 1st stage in the Volga-Kama cascade chain, and lies within the coniferous–deciduous subzone of the forest biome. Forests cover 39% of the catchment area, bogs 2.8%, and lakes 2.2%. The main role of Ivankovo reservoir is water supply, typically discharging 57% of its total input. Major tributaries of the reservoir include the Tvertsa, Shosha and Lama, contributing 35.7% of the total inflow to the reservoir (Vikulina & Znamensky 1975; Butorin & Ekzertsev 1978). Below Ivankovo reservoir, the Volga turns northeast. In this area, the lowland is bordered on the southeast by the Klin-Dmitron ridge and the Uglich and Borisogleb uplands. The elongate Uglich reservoir was constructed here in 1940. The reservoir lies in the forest belt, mainly in the coniferous– deciduous forest biome. The northern part extends into the southern taiga biome. Forests occupy 42% of the basin area, bogs 11%, and lakes 2% (Vikulina & Znamensky 1975). The river from Uglich to the Rybinsk hydroworks flows along the southern Volga part of Rybinsk reservoir, and PHOTO 2.1 Upper Volga: bank of the Inankovo reservoir (Photo: N. Mineeva).

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Chapter | 2 Volga River Basin

represents the 3rd stage in the Volga cascade system. The reservoir was filled after dam construction across the Volga River near Perebory and across the Sheksna River near Rybinsk. Rybinsk reservoir lies in the southern taiga biome of the forest belt, occupying the vast Mologa-Sheksna lowland. The Rybinsk reservoir flooded river channels and their floodplains, upper floodplain terraces, and the vast watershed between the Mologa and Sheksna Rivers. Forests occupy 52% of the basin area, bogs 9.5% and lakes 5.5%, respectively. Altogether, 64 rivers flow into Rybinsk reservoir (Vikulina & Znamensky 1975). The 448-km long river section between the towns of Rybinsk and Gorodets occupies the 4th stage in the Volga cascade system, represented by Gorky reservoir within the southern taiga biome of the forest belt. The upper part of this section between Rybinsk and Yaroslavl is a valley type river, whereas the middle part around the Kostroma confluence forms the lacustrine Kostroma expansion. The Unzha and Nemda Rivers flow into the reservoir along the border between Yurievets and Gorky dam. Forests occupy 57% of the basin area, bogs 6.3%, and lakes 4.4% (Vikulina & Znamensky 1975). Gorky dam acts as a border between the upper and middle Volga. The upper Volga network is best developed in the north, west, and northeast areas of the basin. Although the exact number of small rivers cannot be counted, the four major tributaries, Kostroma, Sheksna, Mologa and Unzha have basin areas from 17 100 to 37 462 km2 and annual discharges of 5–7.5 km3. All other basins occupy between 1000 and 7000 km2. Most tributary rivers are 100–400 km long, although 13 of these are shorter. Information on

discharge is available for 24 rivers and 17 of these have an annual discharge <10 km3 (selected rivers in Table 2.1).

2.5.1.2 The Middle Volga The middle basin occupies about 1 million km2. The 5th stage in the Volga cascade, Cheboksary reservoir (Photo 2.2), is downstream of Gorky dam between the towns of Gorodetz and Cheboksary. The basin lies in the forest belt with the northeast portion in the southern taiga biome and the northwest portion in the mixed coniferous–deciduous forest biome. From Gorodetz to the mouth of the Oka River, the Volga flows through Balakhna Plain and has relatively asymmetric riverbanks. In general, the right bank is high and steep while the left bank is low and ramp shaped. Twenty-eight rivers flow into the middle Volga, the Oka being one of the largest (Table 2.1). The 6th stage of the Volga-cascade is the Kuibyshev reservoir the second largest reservoir in the world based on surface area (Photo 2.3). It lies in two vegetation zones: the coniferous–deciduous forest biome north of Kazan and the forest-steppe biome south of Kazan. Downstream of Kazan, the Volga flows sharply south along the eastern slope of the near-Volga upland. The right riverbank is often high and steep, whereas the left bank is typically low and gently sloping. The Undorski mountain range rises north of Ulyanovsk, while the Belye (at 334 m asl) and Zhiguli (at 370 m asl) mountains lie to the south. Over 100 rivers flow into Kuibyshev reservoir, the largest being the river Kama (Table 2.1) (Znamensky & Chigirinsky 1978). PHOTO 2.2 Middle Volga: Cheboksary reservoir near the city of Nizhny Novgorod (Photo: A. Pegushin).

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PART | I Rivers of Europe

PHOTO 2.3 Kuybyshev reservoir in the Middle Volga (Photo: Institute of Ecology of the Volga Basin, RAS).

2.5.1.3 The Lower Volga The lower basin contains Saratov and Volgograd reservoirs, the Akhtuba floodplain, and the Volga delta (Photos 2.4 and 2.5). The Saratov reservoir above Balakov dam lies along the forest-steppe biome on its right bank and the steppe biome along its left bank. In the Zhiguli section, the river curves (called Samara Bend) and both banks are high and steep. The river then flows southwest at Syzran. The near-Volga upland (at 300 m asl) is found south of Samara Bend on the right side of the river. Within the Samara Bend, a narrow strip of floodplain with black poplars lies along the left bank where the floodplain and upland terraces usually are inundated. Saratov reservoir stores water only in spring when lowland rivers deliver snowmelt runoff (Znamensky & Chigirinsky 1978). The elongate Volgograd reservoir is the lowest manmade impoundment in the Volga cascade, residing mostly

in the steppe biome. The semi-desert biome begins downstream of the Eruslan junction. The right bank of the Volgograd reservoir is high and steep, and closely approaches the near-Volga upland. This upland separates the Volga and Don drainages. The main tributaries in the lower basin include the Eruslan on the left and the Tereshka on the right. Downstream, only a few small temporary streams join the Volga. The Volga continues flowing southeast below Volgograd reservoir, and the major side-arm Akhtuba begins. This sidearm is 603-km long and forms the Volga-Akhtuba floodplain. The river then flows another 350 km, its width varying from 15 to 45 km, to the delta. This lower section covers about 7500 km2. Here, the river and delta reside in the semi-desert and desert biomes. Elevations are around 5–50 m asl in the north and from 0 to 28.5 m asl in the south. The lower floodplain and delta are intersected by at least 279 streams (4800 km in total length) flowing in various directions. PHOTO 2.4 Lower Volga near the city of Astrakhan (Photo: J. Gorbunova).

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Chapter | 2 Volga River Basin

PHOTO 2.5 In the Volga Delta (Photo: A. Gorbunov).

The Volga delta begins with the branching of the sidechannel Buzan, 150 km from the confluence, and covers an area of about 11 500 km2. The upstream area encompasses the transition zone with the Akhtuba floodplain, containing numerous oxbows and a few primary channels. Willows grow along the banks of the channels. In the middle area of the delta occur many ‘hillocks of Baer’ (parallel east-west running sandy hummocks about 1.5–3 m high) together with numerous ‘ilmens’ (lake-like water-bodies <1 m deep that vary in size from a few hectares to several square kilometres) and primary channels that increase in size downstream. The middle area is about 30–50 km wide.

2.5.2. Hydrology 2.5.2.1 Water Flow Presently, the hydrology of the Volga is controlled by flow regulation of the reservoirs. Because the reservoirs were built to control seasonal changes in flow, little effect was seen on river discharge (Figure 2.2) and the total annual discharge

remains near that before the reservoirs. For example, the mean annual flow near Nizhnii Novgorod (middle Volga) from 1876 to 1940 was 2876 m3/s. After construction of Ivankovo and Uglich reservoirs in the upper Volga and during the early construction stages of the Rybinsk reservoir (1942–1955), the mean annual flow in the middle Volga was 2780 m3/s. After Gorky reservoir (1956–1962), average annual discharge remained about 3000 m3/s (Butorin & Mordukhai-Boltovskoy 1979). Inter-annual variation in annual discharge ranged from 160 km3 (1937) to 391 km3 (1926), being influenced by various cyclic oscillations (Klige et al. 2000). Two highwater periods (1951–1962, 1977–1995) and two low-water periods (1963–1976, 1996–present) have occurred in the Volga catchment in the last half-century. Inter-annual variation (3.4–4.2 times) in surface inflow forms >95% of the total input to the catchment. High-water periods are typically 9–16% greater than the long-term average value; while lowwater periods are 16–28% lower than average. Long-term average water discharge varies from 1.5 to 4.2 times in different basins of the Volga (Table 2.1). FIGURE 2.2 Changes in discharge along the Volga from its source to the mouth.

Discharge [m3/s]

10000

7500

5000

2500

0 3000

2000

1000

Distance from mouth [km]

0

32

PART | I Rivers of Europe

The seasonal distribution in discharge depends on the quantity of water from tributaries during the year. The main water source of the Volga and its tributaries is snowmelt, deriving >50% of the annual flow in spring from snowmelt. Discharge in summer and autumn are essentially the same, and a minor increase in discharge occurs in October and November from precipitation. In winter the discharge is low and rarely exceeds 10% of the total annual flow. Interannual variation in water exchange ranges from 3.4 to 17.9 per year in the upper Volga, 4.1–24.3 per year in the middle Volga, and 5.4–23.8 per year in the lower Volga. The Rybinsk reservoir has the lowest water exchange in the Volga cascade system.

stations. Reservoir drawdowns show wide daily and weekly variation, and flow velocities can change by an order of magnitude below reservoir dams.

2.5.2.3 Water Temperature The temperature regime of the Volga is typical of most waters in the boreal zone, following the seasonal pattern in heat input (Figure 2.3). Water temperature generally increases downstream, although sometimes being higher than air temperature in the north and lower in the south. Reservoirs also changed the thermal regime of the Volga. For instance, the average duration of ice-cover increased by 8–20 days and now ranges from 158 days in the upper Volga to 101 days in the lower Volga. However, ice-cover duration has decreased from 90 to 70 days in its lowest section near the city of Astrakhan. In winter, temperatures within flowing reaches and shallow reaches are lowest and most uniform with depth. In deep lake-like areas, temperatures depend on heat exchange between the water and bottom sediments. A gradual increase in temperature due to heat emission of sediments leads to increases in water heat storage and reservoir stratification. The most intensive warming occurs during the spring flood from mid May to early June. Accumulation of spring runoff water in reservoirs and the loss of winter water below dams decrease temperatures by 0.8–2.4 C in the lower Volga and increases water temperatures in the upper Volga. At the end of spring runoff, thermal stratification of water usually develops in reservoirs, but the timing is short and stratification is unstable. Temperature gradients observed at depths of 2–4 m are on average 1–3 C/m. Monthly average temperature of the surface layer is maximum in July, while the total water storage temperature is maximum in August. The seasonal temperature decrease begins in late August and is most intensive in September, especially in the upper Volga (Figure 2.3). Long-term records show an increase in mean water temperature since the late 1970s (Figure 2.4). The Volga contributes on average 104 1017 J of heat per year to the Caspian Sea, and flow regulation has decreased the inter-annual fluctuation in heat runoff.

2.5.2.2 Current Reservoir construction dramatically altered the flow regime in the Volga due to current velocity decreases in the impounded water-bodies. Under natural conditions, mean velocities in the southern part of the upper Volga during low summer flows ranged from 0.26–0.32 m/s in deep areas to 0.50–0.70 m/s over shallow bars. During the annual spring flood, velocities increased to 1.50–1.70 m/s, decreasing to 1.25 m/s post flood. Flood velocities can reach 0.85 m/s in summer and 0.96 m/s in winter (Butorin & Mordukhai-Boltovskoy 1979). Currents in the present Volga system are complex, as river flows are influenced also by convective flows and wind effects formed in the reservoirs. As such, water circulation in the river depends on reservoir morphology and the interaction of these different factors. For instance, river channels dominate the morphology of Ivankovo, Uglich, Gorky, Saratov and Volgograd reservoirs, whereas the total water input governs hydrodynamic processes. Here, the highest flow velocity usually occurs during the spring flood and velocities decrease to a minimum in summer. Flow velocities become considerable again under ice-cover in winter. In contrast, wind effect and bottom relief strongly influence hydrological conditions within the more lake-like Rybinsk and Kuibyshev reservoirs. Regardless, the head and tailwaters of reservoirs have distinctive current regimes due to activities of power

Temperature [°C]

25

Upper

Middle

Lower

20

15

10

5 May

June

July

Aug

Sept

Oct

FIGURE 2.3 Annual temperature regime for the upper, middle, and lower Volga.

33

Chapter | 2 Volga River Basin

FIGURE 2.4 Long-term temperature records for the Volga.

14

12

1950

1960

1970

1980

1990

2000

2.5.3. Biogeochemistry 2.5.3.1 Mineralization The superfluous nature of the Volga results in relatively low water mineralization along the river. Total mineralization decreases with increasing discharge during spring runoff and high flows from rain, and increases during winter and summer low flows. Headwaters in the upper Volga are hydrocarbonate streams with low content of alkaline metals, chloride, and sulphate. Average mineralization values range from 100–270 mg/L in summer to 300–400 mg/L in winter. Mineralization decreases downstream of Rybinsk dam (Kopylov 2001). In the middle Volga, the Oka River adds highly mineralized waters that have a high content of strong acidic ions. For instance, the average sulphate concentration in the Oka typically exceeds that in the Volga by 4–6 times, whereas hydrocarbonate concentrations are lower. Downstream of the confluence with the Oka, chemical stratification of the two rivers is evident although mixing increases towards the mouth of the river Sura. Downstream of the confluence with the Oka, mineralization in the Volga ranges from 150– 340 mg/L in spring and summer to 220–400 mg/L in winter (Butorin & Mordukhai-Boltovskoy 1979). Downstream of the Kama confluence, calcium and hydrocarbonate remain high, but chloride increases twofold and the concentration of alkaline metals also increases. The total amount of chloride and sulphate is almost equal that of hydrocarbonate. Here, mineralization varies from 180–380 mg/L in summer to 480–560 mg/L in winter. Lateral inputs in the lower Volga are small and the salt composition of the water remains similar to those below Kuibyshev reservoir. Intra-annual variation in mineralization in the lower Volga is low with average May–October values of 160–420 mg/L and winter values of 230–470 mg/L (Butorin & Mordukhai-Boltovskoy 1979). Long-term trends indicate an increase in total mineralization of Volga waters (Figure 2.5).

2.5.3.2 Suspended matter High flow velocities within the river, as well as susceptibility to wind mixing in reservoirs, result in high levels of suspended matter in the Volga that affects water transparency. The amount and composition depends on the contribution from alluvial drift, reformation of riverbanks and beds, and

phytoplankton production. Suspended matter content varies from 2 to 35 mg/L. Seasonally, turbidity is typically maximal during spring runoff, minimum in winter, and with periodic increases in summer and autumn from precipitation events. Prior to flow regulation, water transparency generally decreased downstream, whereas presently transparency is higher in the lower Volga.

2.5.3.3 Water colour Water colour is associated with the content of humic organic matter. Due to features of the catchment area and decreased lateral inflow, water colour in the Volga decreases from north to south. Based on colour values, waters of the upper Volga are mainly mesohumic and meso-polyhumic. Occasionally, polyhumic waters with colour >100 Pt–Co degree can be found. Seasonally, water colour is highest during spring runoff with peaks in colour after heavy rains. Water colour is lower below Rybinsk dam and further downstream in the middle and lower Volga. Here, water colour corresponds to a mesohumic type in the Middle basin and to mesohumic and oligohumic type in the lower basin.

2.5.3.4 Dissolved oxygen In spite of flow regulation, the oxygen regime in the Volga remains favourable for hydrobionts and dissolved oxygen (DO) is rather high. Vertical gradients in oxygen are rare, occurring only under ice cover in shallow floodplain areas where DO content can become low enough to kill fish. During the ice-free period, DO content usually is 8–9 mg/L (75–100% saturation). Dissolved oxygen can become super-saturated near the surface during peaks in phytoplankton growth.

250 Mineralization (mg/L)

Temperature (°C)

16

200

150 1950

1960

1970

1980

1990

FIGURE 2.5 Long-term changes in mineralization in the Volga.

2000

34

PART | I Rivers of Europe

2.5.3.5 Bottom sediments

2.5.3.7 Pollution

Before flow regulation, bottom sediments of the Volga down to the confluence with the Sheksna River were stony mixed with coarse sand. Following regulation, the riverbed became gradually sandier. Downstream from the confluence with the Kama, bottom sediments were dominated by fine sand with areas of clay; areas of stony sediments were rare, and loam and mud sediments were deposited in deeper areas. The bed was covered with a mixture of loam, mud and sand sediments in side-arms of the delta having slow currents (Butorin & Mordukhai-Boltovskoy 1979). Sands and transformed soils are the most typical sediments in the littoral of the upper Volga, while grey clay silts cover deep channel areas. Brown and white silts are common in the middle and lower Volga, especially in areas of bank failure (Kopylov 2001; Zakonnov 2005). Transformation of riverbed sediments began with the filling of the reservoirs. Early on, the abrasive action of water masses caused destruction of shorelines and erosion of the streambed. At the same time, transported suspended matter deposited on the reservoir bottom formed secondary deposits that are now the main constituents of reservoir bottoms. The distribution of various sands characterizes the bed sediments of most reservoirs with grey muds common in areas next to the main channel. Muddy deposits predominate in the more lacustrine areas and near dams. The mean rate of deposition was estimated to be 1.7– 2.5 mm/year (Butorin & Mordukhai-Boltovskoy 1979). Today, the mean rate of deposition in reservoirs is 1.9– 3.8 mm/year. These secondary deposits range from 85– 300 cm in the upper Volga, 110–120 cm in the middle Volga, to 65–85 cm in the lower Volga (Zakonnov 2005).

Industrial and agricultural developments in the basin have resulted in an annual discharge of about 21 km3 of waste-water, including 11 km3 of untreated or insufficiently treated wastes. Annually, about 350 000 tons of nitrates, 90 000 tons of phenols, 521 000 tons of sulphates, 384 000 tons of chlorides, and 87 000 tons of organic matter are discharged with the wastewater. The atmosphere of the Volga basin receives 20.6 million tons of toxic substances (Lukyanenko et al. 1994; Komarov 1997, http://www.biodat. ru/doc/biodiv/part6b.htm). Serious pollution problems in the Volga catchment are associated with water abstraction for irrigation, industrial and municipal needs. In 1993, total consumption of freshwater in the Volga catchment was 34 billion m3: 47% for municipal needs, 29% for industrial production, and 24% for agriculture. The state of aquatic resources in the catchment indicates both qualitative and quantitative degradation that poses a serious threat to aquatic and terrestrial ecosystems (Avakyan 1998).

2.5.3.6 Nutrients Following flow regulation, the Volga maintains relatively high nutrient loads favourable for growth of phytoplankton. Anthropogenic inputs from the surrounding landscape sustain high levels of total phosphorus (TP) and total nitrogen (TN) in the river. Seasonally, little variation was found for TP or TN during the ice-free period in Rybinsk reservoir. Nutrient re-suspension from bottom sediments also occurs in open, large, shallow areas subject to wind mixing. In terms of inorganic nutrients, nitrate and phosphate are high in concentration. Mineral nutrients decrease substantially during phytoplankton blooms, becoming higher after elimination of algae. Total phosphorus content averages 71–139 mg/L and TN 0.88–1.32 mg/L with the highest values of both nutrients found in the middle Volga. Here, TN may be as high as 2.16 mg/L. Long-term trends show an increase in nutrient content from the river into the Caspian Sea. Indeed, TP has increased by 89% and TN has increased by 48% from 1935 to 1985. During the last 15 years, TN and TP have decreased, although nitrate and phosphate continued to increase.

2.6. AQUATIC AND RIPARIAN BIODIVERSITY 2.6.1. Upper Volga 2.6.1.1 Plants The upper Volga basin is located in the zone of southern taiga forests. Vegetation of the river and its littoral is diverse. Representative vegetation in the basin is a combination of osiers (Salix acutifolia, S. triandra, S. viminalis), oak (Quercus robur) and black alder (Alnus glutinosa) forests. Widely distributed are meadows covered by red fescue grass (Festuca rubra), foxtail (Alopecurus pratensis) and creeping bent grass (Agrostis alba). Lower areas of the floodplain are dominated by communities of reed canary grass (Phalaroides arundinacea) and narrow-leaved sedge (Carex acuta) (Isachenko & Lavrenko 1980). Riverbanks alternate between thickets of willow (S. triandra, S. cinerea) and P. arundinacea. Gentle wet banks and dry shoals in bays are dominated by thickets of manna grass (Glyceria maxima), narrowleaved sedge (C. acuta), and swamp horse-tail (Equisetum fluviatile). Periodically, there are growths of reed (Phragmites australis) and bulrush (Scirpus lacustris). In the river channel, pondgrasses (Potamogeton pectinatus, P. perfoliatus) prevail. Aquatic vegetation is more diverse in reaches of rivers and bays of reservoirs in the upper Volga. Here, Batrachium circinatum, Ceratophyllum demersum, Myriophyllum spicatum, Nuphar lutea, Nymphaea candida, P. lucens, and P. natans dominate. At some sites occur the North American introduced species Elodea canadensis. Overall, the flora of the upper Volga and its reservoirs is represented by 138 species of higher aquatic plants.

35

Chapter | 2 Volga River Basin

2.6.1.2 Algae On the basis of published (Yakovlev 2000) and unpublished data from 1953 to 2004, 1329 phytoplankton species or 1609 species, varieties and forms have been identified in the upper Volga. Green algae (571) and diatoms (340) are taxonomically the most diverse planktonic algae. The greatest diversity of algae (983 species) has been found in Rybinsk reservoir, it having a vast littoral zone. The total number of algal species in Gorky reservoir is 754, 672 in Ivankovo reservoir, and 412 in Uglich reservoir. Diatoms and blue-greens show major seasonal and longterm phytoplankton dynamics in the upper Volga reservoirs (Lyashenko 1999, 2000; Okhapkin et al. 1994; Kopylov 2001). Three peaks in diatom biomass occur during the open water season, that is spring, summer and autumn, with a maximum peak in spring. Major species include Aulacoseira islandica (O. M€ ull.) Sim., A. subarctica (O. M€ ull.) Haworth, A. ambigua (Grun.) Sim., A. granulata (Ehr.) Sim., Stephanodiscus hantzschii Grun., S. minutulus (K€ utz.) Cleve et M€ uller, S. neoastraea (Hak. et Hickel) emend. Casper, Scheffler et Augsten, Stephanodiscus binderanus (K€utz.) Krieg., S. invisitatus Hohn et Heller., Asterionella formosa Hass., Diatoma tenuis Agardh., Skeletonema subsalsum (A. Cl.) Bethge., and at times Fragilaria crotonensis Kitt., F. capucina Desm., Synedra ulna (Nitzsch.) Ehr., S. acus K€utz., and Melosira varians Ag. Small-celled algae typical of waters with high organic content such as genera Stephanodiscus: S. hantzschii and S. minutulus, as well as the brackish water species Skeletonema subsalsum were common in the 1960s. These species appeared along the entire Volga following completion of the main hydro-engineering works. S. subsalsum invaded the Volga from the south, and belongs to the Ponto-Caspian group. In the 1990s, the appearance of the brackish-water Actinocyclus normanii (Greg.) Hust. was registered in Rybinsk reservoir (Genkal & Yelizarova 1996). It entered from the Baltic and Caspian Sea basins. Since 2000, this species has been actively spreading in Rybinsk and Gorky reservoirs. In 2000, the diatoms Cyclotella radiosa (Grun.) Lemm. and Cyclostephanos dubius (Fricke) Round began to dominate phytoplankton of Ivankovo and Rybinsk reservoirs. These species are common algae in Sheksna reservoir located to the north. In the 1980s, Cyclotella meneghiniana K€ utz. was an important component of the phytoplankton community in Rybinsk Reservoir. From 1980 to 2000, Stephanodiscus binderanus disappeared as a dominant alga in Ivankovo and Uglich reservoirs. Cyanobacteria (blue-greens) develop mainly in summer. Summer blooms of Aphanizomenon flos-aquae (L.) Ralfs, Microcystis aeruginosa (K€ utz.) K€ utz., M. wesenbergii (Kom.) Kom., M. holsatica (Lemm.) Lemm and at times Anabaena species have been recorded. In the 1960s, nonheterocystous cyanobacteria Planktothrix agardhii (Gom.) Anag. et Kom. and mixotrophic cryptomonads were common in Ivankovo reservoir. The abundance of cryptomonads

(species Cryptomonas, Chroomomas acuta Uterm.) increased in the 1970s in Rybinsk reservoir, and during the 1990s these algae began to dominate Gorky reservoir. In Uglich reservoir in the 1990s, P. agardhii became common in phytoplankton samples. The green algae Coelastrum, Pediastrum, Scenedesmus, Sphaerocystis, Schroederia, Mougeotia, Chlamydomonas, Carteria and Pandorina morum (O. M€ull.) Bory generally prevail in summer phytoplankton communities. The greatest diversity of green algae is noted for Rybinsk reservoir. In 2000, development of motile species of the genera Chlamydomonas, Carteria and P. morum increased here. Mean annual phytoplankton biomass during the ice-free period of 1954–2001 increased from 0.5 to 3.4 g/m3. Maximal values were recorded in the 1970s in the highly eutrophic Ivankovo reservoir, and highest biomasses were recorded in summer and in spring.

2.6.1.3 Zooplankton Zooplankton in the upper Volga consists of about 400 species, mainly Cladocera, Copepoda and Rotifera. The last group dominates the community, making up >60% of the total species number (Butorin & Mordukhai-Boltovskoy 1979; Kopylov 2001). Two seasonal maxima in zooplankton can be observed. Cladocera make up 60–70% of the total biomass in June, while the Copepoda (up to 80% of biomass) prevail more often during late summer in August. The most abundant and wide spread are the Crustacea Bosmina longispina Leydig, B. coregoni (Baird), B. longirostris (O.F. M€uller), Daphnia galeata Sars, D. cucullata Sars, D. cristata Sars, Chydorus sphaericus (O.F. M€uller), Mesocyclops leuckarti Claus, Thermocyclops oithonoides (Sars), Cyclops kolensis Lilljeborg, C. vicinus Uljanin, Eudiaptomus gracilis Sars, Heterocope appendiculata Sars, Leptodora kindtii (Focke), Bythotrephes longimanus Leydig, and Rotifera Asplanchna priodonta Gosse, Conochilus hippocrepis (Schrank) and C. unicornis Rousselet. Since the 1980s, larvae (veliger) of the mollusk Dreissena polymorpha Pallas were common in Ivankovo and Uglich reservoirs, making up 1.3–1.5 million organisms/m3 in the mid-1990s (Stolbunova 1999). The dominating complex of zooplankton is quite variable, changing every 10–20 years. At present, two groups can be distinguished among nonnative species. The first group includes northern lacustrine forms Heterocope appendiculata, Eudiaptomus gracilis, E. graciloides Lilljeborg, Cyclops kolensis, Limnosida frontosa Sars, Daphnia longiremis Sars, D. cristata, Bosmina longispina, Bythotrephes longimanus that entered the upper Volga from lakes Volgo, Peno, Vselug and Sterzh, and Lake Beloye on the river Sheksna even before regulation. These species presently make up the main part of the total species number. The second group includes species recently introduced in the Volga. The northern species Arctodiaptomus laticeps Sars appeared in Rybinsk reservoir in 2004 probably from Lake Beloye and is still rare.

36

PART | I Rivers of Europe

Southern species such as Asplanchna henrietta Langhaus, Diaphanosoma orghidani Negrea and Acanthocyclops americanus (Marsh) moved into the upper Volga in the 1980s. The number of A. americanus has sharply increased since the early 1990s. An expansion of Asplanchna henrietta and Diaphanosoma orghidani has begun since 2003–2004, and now they are common forms of plankton. However, high numbers (3–15 000 organisms/m3) are found only occasionally (Stolbunova 1999; Kopylov 2001; Gusakov 2001). Zooplankton abundance differs significantly between different sites in the catchment. Mean seasonal (May– October) abundance is 350–400 000 organisms/m3 in Ivankovo and Uglich reservoirs (Stolbunova 1999). In Rybinsk and Gorky reservoirs, abundances do not exceed 4– 116 000 organisms/m3. Mean zooplankton biomass varies from <1 to 6 g/m3 (Mineeva 2000; Kopylov 2001; Shurganova et al. 2005) (Figure 2.6). Long-term fluctuations in zooplankton abundance occur at about 10-year intervals for numbers and about 20-year intervals for biomass.

2.6.1.4 Zoobenthos

Phytoplankton (g/m 3)

Freshwater zoobenthos is the most diverse group of animals in the Volga River, including 8 types and 17 classes (Butorin & Mordukhai-Boltovskoy 1979). At present, more than 800 species of macroinvertebrates have been found in the benthic fauna of the upper Volga (Kopylov 2001; Shilova & Zelentsov 2003). The majority, 273 species, belongs to Chironomidae;

heterotopic organisms that spend most of their life cycle in the aquatic environment. Oligochaetes and mollusks are the most numerous among homotopic animals, comprising 71–85% of the total species number in different areas of the Volga. In total, 170 benthic species had been found in flooded channels of the Volga. Among them, six Oligochaete species (Tubifex newaensis (Mich.), T. tubifex (M€uller), Limnodrilus claparadeanus Ratzel, L. hoffmeisteri Claparede. Potamothrix hammoniensis (Mich.), P. moldaviensis (Vejd. et Mr.), two chironomids (Chironomus plumosus (L.) and Procladius choreus (Mg.)) and two mollusks (Dreissena polymorpha (Pallas) and D. bugensis (Andrusov) form >90% of zoobenthic numbers in deep water reaches. The larvae of Chironomidae (Chironomus muratensis Ryser et al., Lipiniella araenicola Shil., Stictochironomus crassiforceps (K.), Polypedilum bicrenatum K., Cladotanytarsus mancus (Walk.) as well as the oligochaete T. newaensis and amphipod Gmelinoides fasciatus (Stebb.) dominate shallow waters. Five macroinvertebrates including two Coleoptera species (Ditiscus latissimus L. and Graphoderus bilineatus (Deg.), Odonata (Leucorrhinia pectoralis (Charp.), and two mollusks (Anisus vorticulus Troschel and Unio crasus Philips) are under danger of extinction. Several Ponto-Caspian introductions (non-indigenous benthic species) inhabit the upper Volga at present. They are the mollusks Dreissena polymorpha, D. bugensis, and Lithoglyphus naticoides Pfeiffer, polychaetes Hypania invalida Grube, oligochaetes Potamothrix heusheri (Bret.) and FIGURE 2.6 Changes in the biomass of phytoplankton (A), zooplankton (B), and zoobenthos (C) from the source to the mouth in the Volga.

20

10

A

0

Zooplankton (g/m 3)

5.0

2.5

B

0

Zoobenthos (g/m 2)

60

40

20

C

0 3000

2000

1000

Distance from mouth (km)

0

37

Chapter | 2 Volga River Basin

P. vejdovsky Hrabe, Baikal amphipods Gmelinoides fasciatus (Kopylov 2001; Pavlov et al. 2003), gammarids Dikerogammarus haemobaphes (Eichw.) (Bakanov 2003), and Chinese crab Eriocheir sinensis Edwards. Macrozoobenthos biomass in the deepwater zone of upper Volga reservoirs depends considerably on the thickness of silt sediments and the current regime. Minimal biomass values (0.1–0.5 g/m2) were found in riverine areas of Rybinsk and Gorky reservoirs, while maximal biomass was found near Rybinsk reservoir dam (Figure 2.6). Average biomass within the sunken Volga River channel and in the reservoirs varies little, from 13.0 1.8 g/m2 (Uglich Reservoir) to 19.4 3.7 g/m2 (Rybinsk Reservoir).

2.6.1.5 Fish Ichthyofauna of the Volga River is represented by 23 families with the most diverse being cyprinids (36 species), percids (9 species) and salmonids (8 species) (Berg 1948, 1949a, 1949b). Prior to regulation, there were up to 69 fish species comprising 5 groups. 1. Species living all along the river such as sterled sturgeon, roach, dace, chub, ide, redeye, zherekh, belica, undermouth, bleak, bystranka, silver bream, bream, white-eye bream, blue bream, sabrefish, sazan, sheatfish, pike, burbot, pikeperch, Volga pikeperch, and perch. 2. Species inhabiting separate sites of the basin or tributaries such as river lamprey, trout, taimen, grayling, and minnow. 3. Species of brackish waters of the delta such as Caspian kilka, stickleback, needle-fish, and some sculpins. 4. Anadromous species such as beluga, sturgeon, stellate sturgeon, ship, Volga and black-backed shad, lamprey, sheefish, and Caspian salmon. Representatives of the group fattened in the Caspian Sea, went upstream in the river to spawn, and then migrated downstream back to the sea with fry. Sturgeons reached the town of Rzhev, blackbacked shad arrived at the Oka and Kama Rivers, and Ponto-caspian alosa (Alosa caspia) arrived at Yaroslavl. 5. Semi-anadromous fish inhabiting the desalinated part of the Caspian Sea and spawn in the delta at a distance of 600 km, including sterled sturgeon, bream, vobla (Rutilus rutilus caspicus), pikeperch, Volga pikeperch, sheatfish, three species of clupeids, kilka, rearl roach, barbel, shemaya and vimba. Regulation of the Volga resulted in the disappearance of a distinctive ichthyofauna in the upper, middle, and lower Volga. Before filling of reservoirs, ichthyofauna of the upper Volga consisted of 38 species of residential fish and 6 species of anadromous fish, that is Caspian lamprey, Russian sturgeon, beluga, stellate sturgeon, sheefish (Caspian migrants), and eel (Baltic migrant). From the source up to the Sheksna confluence, grayling dwelled in the main channel, while trout inhabited some tributaries. Ecological composition of ichthyofauna in the Volga and tributaries did not strongly

differ and consisted of the same reophilous elements typical of the entire catchment (Yakovlev 2000). After filling the reservoirs, Caspian anadromous fish disappeared. At present, grayling, Volga undermouth, and chub form small local populations in tributaries and in the Volga upstream of the town of Tver. Twenty-five mainly limnophilous species can be found in Verkhnevolzhskoe reservoir, although eutrophication resulted in the gradual disappearance of vendace, a valuble coregonid fish (Ivanov & Pechnikov 2004). There is no reliable information on selfreproducing populations of trout. The only residential species of sturgeon in the upper Volga basin, sterled sturgeon, which was among the earlier trade fish can be found as a small self-reproducing population in Gorky reservoir. Relic populations are found in Lake Beloye, and vendace and smelt settle in the upper Volga and along the Volga cascade. Dominating fish species are bream, roach, blue bream, silver bream, sabrefish, perch, and pikeperch, all limnophilous fishes. At present, the annual catch is about 300 tons in Ivankovo reservoir, 200 tons in Uglich reservoir, 1500 tons in Rybinsk reservoir, and 350 tons in Gorky reservoir. Catches consist mainly of bream, roach, blue bream and pikeperch (Kopylov 2001; Ivanov & Pechnikov 2004). Since the 1930s, attempts of acclimation and breeding of a number of species have been undertaken. However, only sazan and peled formed small self-reproducing populations, and the occasional acclimation of Amur sleeper and guppy. Since the 1980s, self-reproducing species of Baltic and White Sea basins (nine-spined stickleback) and euryhaline Ponto-Caspian species (Ponto-Caspian tyulka, southern ninespine stickleback, round goby, Caspian bighead goby, stellate tadpole-goby) are present. Self-reproducing populations are formed also by round goby, kilka and bitterling. Altogether, there are self-reproducing populations of 14 nonnative species in the upper Volga.

2.6.2. Middle Volga 2.6.2.1 Plants The middle Volga lies within forest, forest-steppe and steppe biomes. In the north it lies in the zone of spruce and northern broad-leaf forests, in the zone of herb-feather grass steppe in the south, and within meadow steppe mixed with broad-leaf and pine forests in the center (Isachenko & Lavrenko 1980). After construction of Cheboksary and Kuibyshev reservoirs, virtually no floodplain vegetation was preserved in the middle Volga. The banks of the middle Volga reservoirs are mostly open meadow or meadow-steppe. On the banks of islands in forest-steppe and, especially, in forest zones, osier thickets (Salix triandra, S. viminalis etc.) are found. Aquatic vegetation is rich and diverse (95 associations 43 formations). The greatest area is occupied by narrow-leaved cattail (Typha angustifolia), reed (Phragmites australis), manna grass (Glyceria maxima), bulrush (Scirpus lacustris), pondweed (Potamogeton

38

pectinatus, P. perfoliatus, P. lucens, P. natans), and hornwort (Ceratophyllum demersum). Aquatic flora are represented by 142 species of macrophytes, including 61 genera and 38 families. Most diverse are the pondgrasses (Potamogeton) at 21 species and 14 hybrids. High diversity is found in the flora of damp sandy and rubble shoals in Kuibyshev reservoir, where the boundaries of many southern, western and eastern species overlap. Introduced plants are abundant. The most widely spread are Elodea canadensis and Bidens frondosa.

2.6.2.2 Algae During 1957–1995, the number of phytoplankton taxa in the middle Volga reservoirs (Yakovlev 2000; Trifonova 2003) accounted for 1335 species (1628 species, varieties and forms) and was similar to that in the upper Volga. The greatest phytoplankton diversity was found in Kuibishev reservoir (1166 species). In Cheboksary reservoir, the number of taxa is equal to that in Gorky reservoir located upstream. Algal flora of the middle Volga and especially in Kuibishev reservoir is characterized by a high diversity of euglenoids. The diatom spring bloom is dominated by Stephanodiscus hantzschii, S. minutulus, S. binderanus, Aulacoseira islandica, Asterionella formosa, M. varians, and at times species of the genus Synedra, S. ulna, S. acus. In summer, the complex is replaced by a combination of diatoms, cyanobacteria and green algae. Among them the most typical are the diatoms Aulacoseira granulata, A. ambigua, A. subarctica, Cyclotella meneghiniana, Skeletonema subsalsum, Stephanodiscus invisitatus, S. neoastraea, Fragilaria crotonensis, Diatoma tenuis; cyanobacteria Aphanizomenon flos-aquae, Microcystis aeruginosa, M. wesenbergii, M. pulverea (Wood) Forti emend. Elenk., species of genus Anabaena; chlorophytes Pediastrum, Coelastrum, Chlamydomonas, Oocystis, Scenedesmus, Monoraphidium, Planctococcus, and Pandorina morum. At times, euglenoids (Euglena, Trachelomonas, Phacus) dominate in Cheboksary reservoir in summer. Diatoms form a significant part of the algal community in autumn (Okhapkin 1994; Trifonova 2003). Since the 1980s, cryptomonads (Cryptomonas, Chroomonas) became an important component of the late spring and autumn phytoplankton community (Okhapkin 1994; Pautova & Nomokonova 2001). The invasive diatom species, Actinocyclus normanii began dominating since the 1980s in Kuibishev reservoir in summer and autumn (Genkal et al. 1992). Mean annual phytoplankton biomass during the ice-free period of 1956–1992 increased from 1.6 to 16.3 g/m and reached maximal values in the 1970s in Kuibishev reservoir.

2.6.2.3 Zooplankton Zooplankton of the middle Volga consists of over 200 species of the same large taxa, that is Cladocera, Copepoda, and Rotifera, as the upper Volga. Among them, the

PART | I Rivers of Europe

Rotifera (>50% of total species number) and Cladocera (>30%) prevail. The most abundant are Crustacea. Copepods make up >60% of the total biomass in Cheboksary reservoir, while Cladocera dominate in Kuibyshev reservoir (Shurganova 1987; Timokhina 2000; Shurganova et al. 2005). Widespread and numerous taxa include Crustacea Chydorus sphaericus, Bosmina longirostris, B. longispina, B. coregoni, Daphnia galeata, D. cucullata, Mesocyclops leuckarti, Thermocyclops oithonoides, Cyclops kolensis, C. vicinus, Acanthocyclops vernalis (Fisch.), Heterocope caspia Sars, Eurytemora affinis (Poppe), Eudiaptomus gracilis, Leptodora kindtii, Bythotrephes longimanus, and Rotatifera Brachionus calyciflorus Pallas, B. angularis Gosse, Keratella quadrata (O.F. M€uller), Asplanchna priodonta, Conochilus unicornis. As with the upper Volga, two groups of non-native species can be distinguished. The first group consists of the northern lacustrine forms entering downstream from the upper basin: Heterocope appendiculata, Eudiaptomus gracilis, Cyclops kolensis, Eurytemora lacustris (Poppe), Limnosida frontosa, Daphnia cristata, Bosmina longispina, B. coregoni mixta (=B. coregoni kessleri (Uljanin), Bythotrephes longimanus. At present, most of them are basic components of the middle Volga. Introduction of southern species began before regulation of the Volga. Among them, Heterocope caspia, Eurytemora affinis were found in Kuibyshev reservoir in the 1960s, the last becoming numerous since 1984 (Timokhina 2000). Two southern species entered the middle Volga just recently. The Caspian Cornigerius maeoticus maeoticus (Pengo) appeared in 1993–1994 and formed high abundances in 2000, and a few individuals of another Caspian Crustacen, genus Cercopagis, have been found in 2002–2005 (Dgebuadze & Slyn’ko 2005). Seasonal (May–October) average zooplankton biomass decreases downstream and varies from 0.7–1.2 g/m3 in river reaches to 0.4–0.9 g/m3 in lentic habitats (Shurganova 1987; Timokhina 2000). Long-period zooplankton dynamics show an increase in the amplitude in annual biomass as well as tendency for a decrease overall. Major changes in zooplankton of Kuibyshev reservoir took place since 1982, when the number of Rotifera became much lower, and the number of Cladocera much higher after filling of Cheboksary reservoir.

2.6.2.4 Zoobenthos More than 600 zoobenthic species have been identified from the middle Volga. The richest in number are Chironomidae (200 species) and Mollusca (112 species). At present, oligochaetes, chironomides and mollusks make up the most in zoobenthic number and biomass. The Ponto-Caspian gammarides Dikerogammarus haemobaphes (Eichw.), Pontogammarus obesus (G. Sars) and P. robustoides (Grimm) also are abundant (Butorin & Mordukhai-Boltovskoy 1979;

39

Chapter | 2 Volga River Basin

Borodich & Lyakhov 1983; Bakanov 1988, 2005; Zinchenko 2002). The two mollusk species under danger of extinction, Anisus vorticulus and Unio crasus, inhabit the middle Volga. The non-native Ponto-Caspian mollusk Dreissena polymorpha, as well as amphipods Dikerogammarus haemobaphes, P. obesus, P. sarsi (Sowin.), Stenogammarus dzjubani (M.Bolt. & Ljach.) and Corophium curvispinum G. Sars that are common today had been found in the basin before the Cheboksary and Kuibyshev reservoirs were filled. Following impoundment, some intentional introductions had taken place, including the Ponto-Caspian species of polychaetes Hypania invalida, and Manayunkia sp., mollusks Monodacna colorata (Eichw.), Dreissena bugensis, Lithoglyphus naticoides, Teodoxus pallasi Lind., and Borysthenia naticina (Menke), amphipods Corophium sowinskyi Martyn., Paramysis ullskyi Czern., P. intermedia (Czern.), Schizorinchus bilamellatus (G. Sars), Gammarus pulex (L.), Dikerogammarus caspius (Pallas) and Pterocuma sowinskyi (G. Sars), and leeches Archaeobdella esmonti Grimm (Butorin & Mordukhai-Boltovskoy 1979; Pirogov et al. 1990; Antonov 1993; Bakanov 2005; Dgebuadze & Slyn’ko 2005). In 2001, two Baikal gammarides Gmelinoides fasciatus and Micruropus possolskyi Sow. (Bakanov 2005) were intentionally introduced into Gorky reservoir (Yoffe 1968) as well as the Chinese crab Eriocheir sinensis and amphipoda Pontogammarus crassus Grimm, Corophium fluviatilis (Martynov) in Cheboksary reservoir. Initially after the Kuibyshev reservoir was in operation, average macrozoobenthos biomass in the channel was low at about 5 g/m2 (Butorin & Mordukhai-Boltovskoy 1979; Borodich & Lyakhov 1983). In 1985, average macrozoobenthos biomass within the Volga River and in Kuibyshev reservoir was 12.1 2.3 g/m2, and 5.6 2.1 g/m2 in Cheboksary reservoir, mainly oligochaetes (Bakanov 1988). As the Cheboksary reservoir bottom became siltier, macrozoobenthos biomass within the channel increased and in 2001 was 9.7 2.1 g/m2.

2.6.2.5 Fish There are 19 fish species in Cheboksary reservoir and only 11 (vendace, smelt, guppy, nine-spined stickleback, Amur sleeper, stellate tadpole-goby, monkey goby, Caspian bighead goby, round goby, tubenose goby) have self-reproducing populations. Most non-native species first appeared from 1950–1960, including five salmonids and four cyprinids, while six percids appeared in the mid-1990s. Cyprinid species were observed at a single time in the reservoir, and among salmonids only vendace and smelt formed self-reproducing stocks. Percids, in general, can be found everywhere. The single representative clupeid, the tyulka, is highly abundant (Dgebuadze & Slyn’ko 2005). Before filling the Kuibyshev reservoir, 47 fish species inhabited this reach of the Volga. After the reservoir had been filled in 1956, the number of species increased

(Dgebuadze & Slyn’ko 2005), most of them represented by typical limnophilous cyprinids and percids. Self-reproducing fish include two species of silver carp, Asian carp, peled, buffalo, some occasional mysids (i.e. Ponto-Caspian needle-fish, round goby, stellate tadpole-goby), non-native fish from the north (i.e. vendace, European smelt), and some fishes from the south (i.e. Ponto-Caspian tyulka). Altogether, 9 species are self-reproducing and 12 species belong to occasional non-native ichthyofauna. Species such as round goby, Amur sleeper and pipefish reproduce successfully and shown increases in number. More recently, grayling and common undermouth have been found, and paddlefish and channel catfish are self-reproducing. Amur bitterling, Siberian loach and guppy have been found but their distribution is still unknown, and individuals of Siberian sturgeon and bester (beluga sterled) also may be encountered. Few invasive species have self-reproducing populations in the middle Volga, and they are mostly insignificant in number. More valuable fish introduced by direct efforts are rare and do not have self-reproducing populations. The basic fishery consists of limnophilous species, mainly cyprinids and percids that are typical of the present Volga. Presently, the annual catch is about 2000 tons in Kuibyshev reservoir and 200 tons in Cheboksary reservoir, consisting mainly of bream, roach, silver bream, and blue bream (Ivanov & Pechnikov 2004).

2.6.3. Lower Volga 2.6.3.1 Plants The lower Volga flows through herb-feather grass, fescuefeather grass and deserted wormwood-fescue-feather grass steppes (Lipatova 1980). Remnants of floodplain vegetation in the lower Volga are preserved on islands in Saratov and Volgograd reservoirs and within the Volga-Akhtyubinsk floodplain, being represented by osiers (Salix acutifolia, S. triandra, S. viminalis), white willow (S. alba), black poplar (Populus nigra), elm (Ulmus laevis) and oak (Quercus robur) forests, fescue (Festuca valesiaca) and herb-fescue steppes, and coach grass (Elytrigia repens) and herb-coach grass halophyte meadows turning into sedge and boggy meadows of Carex acuta, Sparganium erectum, Alisma plantago-aquatica, and Butomus umbellatus in depressions (Lipatova 1980). Aquatic vegetation is less diverse than in the upper and middle Volga. Here the main vegetation in shallows is semi-submersed species dominated by reed Phragmites australis and narrow-leaved cattail Typha angustifolia. Submersed plants are dominated by pondweed Potamogeton perfoliatus. In lower reaches of the river, Phragmites australis is replaced by P. altissimus, developing sprouts 4–6 m high. On the whole, the aquatic flora in the lower Volga is represented by 135 species of vascular plants.

40

2.6.3.2 Algae From 1968–2002, 1003 species (1179 species, varieties and forms) of phytoplankton had been recorded in the lower Volga reservoirs (Yakovlev 2000; Trifonova 2003). Phytoplankton of Saratov reservoir is the most diverse. Diatoms and green algae are the richest in terms of species diversity in the lower Volga, although the number of taxa is lower (1179) than found in the upper and middle Volga. Diatoms and cyanobacteria are the most important members of the lower Volga phytoplankton community. Diatoms Stephanodiscus hantzschii, S. binderanus, Aulacoseira islandica, Asterionella formosa, Diatoma tenuis, Melosira varians, and Skeletonema subsalsum are most often dominant in spring. In summer, diatoms S. subsalsum, A. granulata and cyanobacteria Aphanizomenon flos-aquae, Microcystis aeruginosa, M. wesenbergii, M. pulverea and species of genus Anabaena form an important part of the phytoplankton community. Chlorophytes (species of genus Pediastrum, Scenedesmus, Monoraphidium, Coelastrum, Actinastrum, Chlamydomonas and Pandorina morum) are also abundant at this time (Gerasimova 1996; Daletchina & Silnikova 2001; Pautova & Nomokonova 2001; Poptchenko 2001; Trifonova 2003). The invasive diatom Actinocyclus normanii became a significant component of the summer-fall phytoplankton in the lower Volga since 1980. From 1980 to 1990, the proportion of non-heterocystous cyanobacteria of genus Oscillatoria, Phormidium, Lyngbya, Aphanothece, and Synechocystis increased. In the 1990s, cryptomonads became an important part of the phytoplankton community. Spring and summer complexes of algae continue to develop in autumn. The number of algae taxa in the unregulated section of the lower Volga is even less than in the Saratov and Volgograd reservoirs. In 1964–1969, richness totalled only 287 species, varieties and forms (Voloshko 1971), increasing to 390 in 1984–1991 (Labunskaya 1995). According to Labunskaya (1995) and our unpublished data (1989–1991), diatoms dominate during the ice-free period. The spring complex consists of Stephanodiscus hantzschii and Aulacoseira islandica, while in summer it includes A. granulata, Skeletonema subsalsum, Actinocyclus normanii and blue-green algae Aphanizomenon flos-aquae and Microcystis aeruginosa. In 1997, 127 taxa of algae were found in this reach of the Volga. Together with the common diatoms and cyanobacteria, Oscillatoria (cyanobacteria) and Chroomonas (cryptomonads) were recorded as dominants (Trifonova 2003). Average annual phytoplankton biomass during the icefree period of 1984 to 1990 ranged from 0.6 to 7.6 g/m3 with maximal values in 1989 (Labunskaya 1995). In general, the species diversity of phytoplankton decreases from the upper to lower Volga. In recent years, the proportions of invasive brackish-water diatoms, non-heterocystous cyanobacteria and mixotrophic cryptomonads have increased in the Volga. Average annual phytoplankton biomass during the ice-free period of 1968 to 1993 increased from 0.7 to 14.5 g/m3 and

PART | I Rivers of Europe

reached maximal values in the 1970s in Volgograd reservoir. In Saratov reservoir, maximal biomass of phytoplankton reached 12.6 g/m3 in 1988 and 1989.

2.6.3.3 Zooplankton As well as in the other basins, the zooplankton community in the lower Volga consists of Cladocera, Copepoda, and Rotifera. There are more than 200 species found with a prevalence of Rotifera (>50% of the total) and Cladocera (>30%). The crustaceans Copepoda and Cladocera make up from 50% to 90% of the total biomass. The usual species among them are Daphnia galeata, Chydorus sphaericus, Bosmina longirostris, Mesocyclops leuckarti, Thermocyclops oithonoides, Cyclops kolensis, C. strenuus Fisch., Acanthocyclops vernalis, Heterocope caspia, Eurytemora affinis, Leptodora kindtii), Cornigerius maeoticus maeoticus. The prevalent Rotifera species are Keratella quadrata, Asplanchna priodonta, Synchaeta pectinata Ehrenb., Brachionus quadridentatus Herm., and Euchlanis triquetra Ehrenb. Like in the other two basins, two groups of non-native species can be distinguished. The first is formed by the northern lacustrine forms entering downstream from the upper Volga, including Heterocope appendiculata, Eudiaptomus gracilis, Cyclops kolensis, Eurytemora lacustris, Limnosida frontosa, Daphnia cristata, Bosmina longispina, B. coregoni kessleri, B. obtusirostris Sars, B. crassicornis P. E. M€uller, Bythotrephes longimanus. At present, species such as Cyclops kolensis and Bosmina longispina are the main planktonic taxa in the lower Volga. The second group consists of the southern Caspian species, and most of them began their invasion into the region after construction of the reservoirs. Among them, Calanipeda aquaedulcis Kritsch colonized first in the early 1970s in Volgograd reservoir and later, in 1982, it was found in Saratov reservoir. Cornigerius maeoticus maeoticus became numerous in Volgograd reservoir since 1970 and in 1996 it appeared in Saratov reservoir (Mordukhai-Boltovskoy & Dzuban 1976; Dgebuadze & Slyn’ko 2005). The non-native Cercopagis sp. had high abundances in the lower part of Volgograd reservoir in 2002 (Malinina et al. 2005), although Heterocope caspia had colonized the lower Volga even earlier before reservoir filling. Seasonal development in zooplankton is characterized with a summer peak. Zooplankton biomass is low, being on average <1 g/m3 in Saratov reservoir and about 1.2–1.5 g/m3 in Volgograd reservoir.

2.6.3.4 Zoobenthos Before the Volga was transformed into a system of reservoirs, the macroinvertebrate fauna in the lower Volga was quite similar to that in the middle Volga. The oligochaetes Tubifex newaensis and Caspian gammarids Pontogammarus sarsi dominated in biomass (Butorin & MordukhaiBoltovskoy 1979). After the two lower reservoirs were filled, a number of rheophilic Ponto-Caspian crustacean

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Chapter | 2 Volga River Basin

species disappeared. Nevertheless, the fauna of the submerged river channel in the middle and lower Volga remained similar until today. New findings of a number of Ponto-Caspian species in Kuibyshev and Saratov reservoirs support this idea (Pirogov et al. 1990; Pavlov et al. 2003; Dgebuadze & Slyn’ko 2005). The total species number of macrozoobenthos in the lower Volga is >500 taxa, and among them the Chironomidae (200 species) and mollusks (112 species) are the most diverse (Nechvalenko 1976; Butorin & Mordukhai-Boltovskoy 1979; Zinchenko 2002). The highest quantity and biomass is found in the same oligochaete, chironomid, and mollusk species as the ones dominating in the upper and middle Volga. Additionally, the Ponto-Caspian gammarids Dikerogammarus haemobaphes and Pontogammarus obesus are common (Nechvalenko 1976; Butorin & MordukhaiBoltovskoy 1979). Four inhabitants of the lower Volga benthic fauna are in danger of extinction: Odonata (Coenagrion ornatum Selys. and Leucorrhinia pectoralis) and mollusks (Anisus vorticulus and Unio crasus). At present, macrozoobenthos of the lower Volga contains a number of non-native species, among them include the Ponto-Caspian crustaceans Dikerogammarus haemobaphes, Pontogammarus abbreviatus (G. Sars), P. crassus, P. obesus, P. sarsi, Stenogammarus compressus (G. Sars), S. macrurus (G. Sars), Chaetogammarus ishnus (Stebb.), Pandorites platycheire (G. Sars), Corophium curvispinum G. Sars, Paramysis baeri (Czern.), P. ullskyi, P. intermedia, P. lacustris (Czern.) and Limnomisis benedeni Czern., polychaetes Hypania invalida, mollusks Monodacna colorata, Dreissena polymorpha, D. bugensis, Lithoglyphus naticoides, and Teodoxus pallasi, leeches Archaeobdella esmonti, and Chinese crab E. sinensis (Antonov 1993; Bakanov 1993; Nechvalenko 1976; Butorin & Mordukhai-Boltovskoy 1979; Dgebuadze & Slyn’ko 2005). Today, 15 Ponto-Caspian crustacean species are found in the lower Volga macrozoobenthos and 14 in the middle Volga macrozoobenthos, while only Dikerogammarus haemobaphes is found in the upper Volga. Due to higher current velocities, macrozoobenthos biomass in the main channel has not changed since reservoir construction and averages about 3 g/m2. During the first years after the Volgograd reservoir, macrozoobenthos biomass did not differ from that of Saratov reservoir. However, by 1985 it had increased by more than three times and reached 10.5 3.5 g/m2. Crustaceans, polychaetes and oligochaetes dominate the biomass here (Butorin & MordukhaiBoltovskoy 1979; Bakanov 1988).

sabrefish, sazan, crucian carp, tench, sheatfish, pike, burbot, pikeperch, Volga pikeperch, perch, and ruffe became common and dominate the fishery (Reshetnikov 1998). A total of 17 new species have appeared in the lower Volga. Non-native fishes in Saratov reservoir suggest that the species have a different origin (Dgebuadze & Slyn’ko 2005). Peled, vendace, smelt came in 1960 downstream from the upper basins. Species such as Amur sleeper, Caspian bighead goby, tubenose goby, stellate tadpole-goby, pipefish, and southern ninespine stickleback formed self-reproducing populations. As a result of direct introduction, Asian carp, white and spotted silver carp, smallmouth and black buffalo, and Siberian sturgeon appeared in the reservoir mainly during the 1980s. However, the introductions were not successful because of the small number of fish introduced, and none have been found in the fishery catch in recent times. New fishes appeared in the Volgograd reservoir since 1969, within 10 years after filling (Dgebuadze & Slyn’ko 2005), including the European vendace, smelt, and peled among them. However, only vimba, Amur sleeper, Caspian bighead goby, tubenose goby, stellate tadpole-goby, pipefish, and the southern ninespine stickleback that appeared in late 1990s have self-reproducing populations. A number of valuable species appeared as a result of direct introduction from 1967 to 1990, including white and spotted silver carp and Asian carp smallmouth and black buffalo, black carp, and vimba. These non-native fishes have little significance in the commercial fishery, making about 1% of the total catch. The small-sized Amur sleeper and sculpins are caught by fishermen. Today, the annual catch is about 700 tons in Saratov reservoir, and 1000 tons in Volgograd reservoir, consisting mainly of bream, roach, silver bream, and perch (Ivanov & Pechnikov 2004). The lower Volga had great fishery importance before building of the dam near Volgograd, with an annual output over 12 000 tons. At present, there is no commercial fishery in the lower basin. Regulation of the Volga resulted in the disappearance of a distinctive ichthyofauna in the upper, middle, and lower Volga. The fish population now consists mainly of typical limnophilous species that differ little along the river because of the invasion of non-native species. These species enter as a result of direct introduction of valuable fish as well as the occasional expansion and accidental intrusion. Non-native species originated from three faunistic groups, that is Ponto-Caspian, Arctic, and Chineselowland (plain) group, and the most significant being the Ponto-Caspian complex.

2.6.3.5 Fish

2.7. MANAGEMENT AND CONSERVATION

At present, ichthyofauna of the lower Volga consists of 62 species. After filling of Volgograd reservoir, anadromous fish as well as a number of rheophilous species at sites above the dam disappeared. Limnophilous fish such as roach, ide, bleak, silver bream, bream, white-eye bream, blue bream,

2.7.1. Economic Importance The geographic situation of the Volga and its large tributaries allowed for the development of trade relations between West-European countries and pre-Caspian countries of

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middle Asia by the 8th century. Russia was originally founded along the Volga, partly by Viking entrepreneurs using it as a road to the south from an entry point near Archangel. From the earliest times, the Volga was a great trade way. Cloth, metal fabrics, and precious stones were transported from Central Asia to the north. Furs, wax, honey and slaves were moved from Slavic and Bulgarian lands to Caspian countries. Trade declined in the 11th century following the fall of the Khazar Khaganate, and the Tatar invasion virtually eliminated economic activity in the middle and lower Volga regions since the 13th century. During this period, the river routes from northeast Russia to Veliki Novgorod played an important role in barter exchange with Europe. It has been only since the 14th century that trade has revived throughout the entire Volga with large market centres appearing along the Volga following liberation from Tatar control. The main tradeways moved to the west in the 18th century. Transportation increased into the Volga’s northern tributaries (rivers Tvertsa, Mologa, Sheksna), and their upper reaches were connected with rivers of the Baltic system by a network of man-made canals. Inland water transport was completed on the Volga by the middle of the 19th century. Today, the Volga is connected with the Baltic Sea by the Volga-Baltic water way, Vyshniy Volochek and Tikhvin systems, with the White Sea via the Northern Dvina system and the White Sea-Baltic Canal, and with the Sea of Azov and the Black Sea through the Volga-Don Canal. The construction of reservoirs resulted in an increase of guaranteed depth up to 4 m along the whole length of the river that, in turn, boosted freight turnover from 27.4 million tons in 1930 to 300 million tons in 1990. Some large reservoirs also included hydroelectric power stations in the 1930s with a current gross output of 11 098 thousand kilowatts and total energy generation of 3968 billion kilowatt-hours. The Volga catchment occupies more than a third of the European area of Russia and 8% of the total area of Russia. At present, it is the most populated region in the Russian Federation and 39 administrative units with a total population of some 60 million (40% of the country’s population) are located here. Around 45% of industrial and 40% of agricultural products are produced here. A total 426 of 1057 Russian cities, including 7 cities with a population of more than 1 million people and 10 with populations from 500 000 to 1 million, are situated in the region. The Volga and its tributaries account for 70% of the goods carried by river transport in Russia. More than half of all fish and 90% of all sturgeons from inland waterbodies are caught in the Volga catchment (Avakyan 1998). Vast woodlands are typical for the upper Volga basin. Large areas of the middle and some of the lower Volga basin are occupied by grain and technical crops, and melon farms and private garden plots are common. There are oil and gas fields in the Volga-Urals region, and major deposits of potassium salts are found

PART | I Rivers of Europe

near the city of Solikamsk. Table salt is mined in the lower Volga basin around lakes Baskunchak and Elton.

2.7.2. Conservation and Restoration In the Volga basin, the protected territories, i.e., preserves, forest reserves, national parks, recreational zones, etc., make an appreciable part of the catchment area (Table 2.1). A network of nature reserves covering more than 6000 km2 reside in the Volga catchment. Principal information on reserve activity, and their flora and fauna is summarized in: Sokolov and Syroechkovsky (1988, 1989), Sokolov (1988), Internet sites ‘Reserves’ (http://www.water.zapovednik.com/), ‘Reserves of Russia’ (http://www.sevin.ru/natreserves). The Darwin State Wildlife Biosphere Reserve, established in 1945 and included in the international network of biosphere reserves, is situated in the upper Volga basin within the territory of Vologda and Yaroslavl provinces. The reserve covers an area of 1400 km2 of which 450 km2 is occupied by Rybinsk reservoir. Around 19 species of fish, 7 species of amphibians, 5 species of reptiles, 194 species of birds, 37 species of mammals, 600 species of higher plants 37 of which are rare species, 70 species of mosses, >60 species of lichens, and 123 species of pileate fungi are found in the reserve. The area has a high abundance of brown bear Ursus arctos L., and until recently there was a wood grouse (Tetrao urogallus L.) farm. The Kerzhenskiy Reserve, 469 km2, was organized in 1993 in Nizhniy Novgorod province. It lies in the Kerzhenets River basin (the Volga’s left tributary) within the middle Volga. The reserve is included in the UNESCO network of biosphere reserves under the name ‘Nizhegorodskoye Zavolzhie’. Natural areas of southern taiga were restored in its territory. The Zhiguli State Wildlife Reserve established in 1996 in Samara province is situated in the middle Volga. It covers an area of 230 km2 of which 176 hectares is occupied by Volga waters. About 800 species of higher plants, 20 species of mosses, 20 species of lichens, and 30 species of pileate fungi are found in the reserve. About 240 species of vertebrates including 52 species of mammals, 155 bird species, 6 species of reptiles, 5 species of amphibians, and 19 fish species inhabit its territory. The Astrakhan State Wildlife Biosphere Reserve was founded in the Volga delta in 1919. Presently it occupies 680 km2, including 110 km2 of the Caspian Sea. These open-water areas and marshlands are of international importance (Ramsar Convention – the Volga Delta) and included in the international network of biosphere reserves. Approximately 300 species of higher plants are found here. Thirty species of mammals, 230 bird species and 50 fish species inhabit the area, and the Caspian Ornithological Station operates in the reserve. Measures are taken at each reserve to culture and preserve particularly valuable species of flora and fauna. The

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Chapter | 2 Volga River Basin

following plants of the Volga basin are included in the Red Book of Russia: (Cypripedium macranthon Sw., Cypripedium calceolus L., Cephalanthera rubra (L.) Rich., Koeleria sclerophylla P. Smirn., Schivereckia podolica (Bess). Andrz. ex DC, Globularia punctata Lapeyr., Trapa natans L., Nelumbo nucifera Gaertn. [incl. N. caspicum (DC) +Fisch., N. komarovii Grossh.]), mammalia (e.g. muskrat Desmana moschata L., European bison Bison bonasus bonasus L.), and birds (e.g. white well sweep Grus leucogeranus Pallas, golden eagle Aquilla chrysaetos L., buff-backed heron Bubulcus ibis (L.) Wagler, spoonbill Platalea leucordia L., bushy pelican Pelecanus Pelecanus Brush, bald eagle Haliaetus albicilla (L.), pinc pelican Pelecanus onocrotalus L., osprey Pandion haliaetus (L.), falcon Falco cherrug Gray, little bustard Tetrax tetrax L., flamingo Phoenicopterus roseus Pallas, black stork Cyconia nigra L., and hawk Circaetus gallicus Gmelin) (http://www.biodat.ru).

problems concerning environmental safety from industrial production and the formation of sustainable economic developments (Komarov 1997). Priority guidelines for major ecologically poor complexes include: Development of master non-waste technologies for re-equipment and reconstruction of ecologically unsound developments in the region; development of environmentally safe production of chemicals as well as process technologies that together ensure an increase in ecological-sound industry; realization of new technologies in industry; development of ecologically sound agriculture; rehabilitation of forests and prevention of their degradation, wildlife conservation, and development of wildlife reserves; creation of favourable conditions for development of the fishery; reclamation and use of industrial and municipal wastes; organization of environment monitoring systems and development of a geo-information system; improvement of ecological conditions in cities; and development of ecological education and professional training.

2.8. CONCLUSIONS AND PERSPECTIVES Transformations of the Volga have caused major changes in water circulation that affected the energy flow and massexchange such as water balance and exchange, variation in water levels, flow velocity, and thermal regime. The morphology of reservoirs is influenced by natural climatic factors (i.e. water quantity and quality) as well as human activities that regulate flow. Reservoirs represent unstable ecosystems; however they are integral parts of the Volga River. Together with positive aspects regarding economic development, the Volga transformation has had serious consequences such as flooding of productive lands, collapse of banks due to fluctuations in water level, and losses in the fishery. At present, a fish community resembling the one before regulation inhabits only two reaches of the river. Such rheophilous species such as dace, chub, undermouth, zherekh, loach, gudgeon, minnow, bystranka prevail in the headwaters of the Volga and all typical river fishes can be found within the reach from the river mouth to Volgograd dam. However, their numbers decrease upstream because of unfavorable changes in hydrological regime after regulation. Among the sturgeons, belugas are now rare and sheefish (Caspian salmon) are essentially extinct. Regulation of the Volga resulted in the disappearance of a distinctive ichthyofauna in the upper, middle, and lower Volga. The fish population consists mainly of the same typical limnophilous species along the river because of the invasion of non-native fishes. The high density of humans and extensive industrial development caused a strong anthropogenic impact on the river and its biota. Consequently, conservation actions and nature management should emphasize preservation and recovery of the Volga catchment. The realization of a special federal program ‘Revival of the Volga’ can help in this situation. This program aims at solving urgent

2.9. MAJOR TRIBUTARIES OF THE VOLGA RIVER 2.9.1. The River Kama 2.9.1.1 Introduction The Kama is the largest tributary of the Volga. Its name comes from the Udmurt ‘kam’, meaning ‘river’ or ‘current’. The Kama-Vyatka area was originally colonized by Fins before the end of the 11th century. The first Russian boats arrived on the Kama during this period and resulted in various Russian settlements. The river was a major link of communication between Asia and Europe. For instance, Yermak the Cossack ataman travelled to Siberia on the Kama in the mid-16th century, thereby connecting Siberia with Muscovite Russia. The natural riches of the Ural region caused intensive development of the Kama catchment. The Kama is the 5th longest river in Europe after the Volga, Danube, Ural and Dnieper (Shmidt 1928b).

2.9.1.2 Paleography The Kama valley is older than the Volga, being present already in the early Quaternary (Shklyaev 1964). The Kama and its major tributary Vishera flowed to the Caspian Sea, but presently flow in the upper basin drains to the north. Later glaciation reformed its hydrographic network. The geology as well as the relief of the catchment is diverse. The Ural highlands are situated between the Russian plain in the west and the Siberian plain in the east. The Russian plain and Ural Mountains are divided by an elongate pre-Ural marginal depression that forms the Yuryuzan-Slyvinskaya plain and Belskaya depression. The present-day Urals were formed by neogenic and quaternary vertical-block movements of

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ancient folded-fault massifs, erosive activity of rivers, and long-term weathering. Sedimentary rocks (sand, clay, sandstone, conglomerate, limestone, shale) make up much of the geology in the catchment. Rocks differing in age and composition stretch longitudinally in the catchment. The Eastern European plain is composed of mainly horizontal-beds of sedimentary rocks of Precambrian granite-gneiss of the Russian plain. The most widely distributed are deposits from the Upper Permian period. Among them, Tatar deposits (in the western and central parts of the region) are represented by multi-coloured clays and marls often alternating with limestone and sandstone bands. In the upper Kama and Vyatka basins, beds of Jurassic and Lower Cretaceous marls, clays and sands are superimposed on these deposits. In the Uval area of the Vyatsky basin, limestone and gypsum of the Kazan layer are interspersed among multi-coloured marls. Near the Kama river valley, Tatar deposits are replaced by Kazan deposits in which limestone and marl bands occur among red-coloured clays and sandstones. To the east on the left bank of the middle Kama and along the lower river Belaya, lower Permian Ufa deposits with bands of gypsum occur. Along the margins of the Russian plain are highly soluble lower Permian rocks causing extensive karstic formations. The pre-Ural depression is filled by weakly dislocated Permian sedimentary rocks including some typical salt-bearing sections near the city of Solikamsk, and deposits of gypsum and anhydrites. In the plain, Paleozoic rocks are mostly covered by thin Quaternary deposits of mainly loam soils, and clays and sands in some areas. In the northern Kama catchment, fluvio-glacial sands are underlain by clays. In tributary valleys of the Chusovaya, Sylva and Iren, karstic areas develop under river deposits and non-karstic and karstic rocks of carbonate, sulphate and halogenous composition alternate.

2.9.1.3 Physiography, Climate, and Land Use The relief of the catchment is distinguished by the Ural Mountains in the middle, north and south; and the Eastern European plain (along with the pre-Urals) to the east. Coniferous forests similar to Siberian taiga occur in the upper catchment and deciduous forests are found in the lower catchment, both in the forest-steppe and forest biomes. However, large areas of the catchment have been deforested and are used for agriculture or mining. The Ural Mountains are of moderate height (400– 600 m asl) and have a weathered but strongly irregular surface. Some peaks in the south and north can reach 1500– 1600 m asl. In the northern Urals, a system of parallel, gradually decreasing ridges are found to the west along with various forested plateaus at 400–500 m asl. The middle Urals (59 150 to 55 N) reach 500–600 m asl and consist of a rugged hilly plain with single irregularly spaced peaks, the highest being Sredniy Baseg at 994 m asl. Western foothills of the middle Urals are represented by low ranges rising

PART | I Rivers of Europe

within the plain, including among others Basegi (993 m asl), Belyi Spoi (568 m asl), Kirgishansky uval (555 m asl), and Bardymsky (681 m asl). The southern Urals (55 300 to 56 N) are highly mountainous and contain some of the highest ridges, most of these found in the Belaya river basin. The southern Urals extend for 150–200 km in width and include the Uraltau Divide, a wall-like range reaching up to 1000 m asl. The Eastern European plain has an undulating relief of elevated rugged inter-fluvial areas and wide gentle-terraced river valleys. In the upper Kama and Vyatka lies the flat upper Kama upland about 300 m asl and deeply incised by rivers. The middle Vyatka flows south-east through the distinctive Vyatskiy Uval, running north-south at 250– 280 m asl. In the southern pre-Urals, the Bugulma-Belebeevskaya peak rises up to 450–480 m asl and is connected to the west with Obshchiy Syrt. Climate of the region is defined as continental with large variations in annual and daily temperature. Humid air masses from the Atlantic Ocean exert a strong influence on climate. Features of the relief cause the presence of latitudinal zones in climate in the plain and vertical climate zones in the mountains. Severe snowy winters and short cool summers in the north and frosty winters with little snow and comparatively hot summers in the far south characterize the general climatic differences with latitude. In winter, a Siberian anticyclone causes stable but frosty weather with more snow in the pre-Urals and on mountain slopes. Frequent cold-air surges from the north and southern cyclones often bring sharp changes in weather. In summer, the area is influenced by low-pressure air masses from the Barents and Kara seas, while the air masses from the Azores bring hot dry weather. Average annual air temperature in lowland areas of the Kama vary from 0 to 3 C north to south. The coldest month is January, ranging from 17 to 14 C south to east. Lowest air temperatures occur between December and February, reaching 48 . Average daily temperatures 5 C usually occur by the third week in March, and >0 C in the first week in June. The hottest month is July, averaging 16–17 C in the north and about 19 C in the south. Temperatures decrease to around 5 C in late September early October. Winter thaws are rare and short, often lasting for only several hours. Annual precipitation varies widely but decreases north to south. In the north, annual precipitation reaches 1300– 1600 mm. In mountain valleys, annual precipitation is about 850–950 mm. Annual precipitation is 800–900 mm in the northern middle Urals and 600–700 mm in the south. Annual precipitation is 1200–1500 mm in the southern Urals and 500–600 mm in the pre-Urals plain. Precipitation during the year occurs unevenly and is 1.4–1.7 times higher in summer than in winter. Heavy showers are frequent in the middle Urals and pre-Urals, but drought can occur in the south. Snow cover can happen by September and is complete by late October early November. Spring thaw begins in mid-April in the south and late April in the north. In the mountains and in

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Chapter | 2 Volga River Basin

the northern foothills, spring thaw begins in May. In winter, southerly and southwesterly winds prevail. Wind direction is variable in summer, although northerly, northwesterly and westerly winds are most common. In the mountains, wind direction is affected by orography and mountain-valley winds are common. Annual average wind velocity can vary 2–5 m/s.

2.9.1.4 Geomorphology, Hydrology, and Biogeochemistry The Kama begins in the Ural Mountains, flows east in Udmurtia then south-west in Perm porvince before flowing again through Udmurtia into Tatarstan where it meets the Volga. The Kama flows into the Kuibyshev reservoir in the middle Volga. The length of the river is about 1800 km and its catchment area is about 517 000 km2. Before construction of the Kama reservoir system, its length was 2030 km (Butorin & Mordukhai-Boltovskoy 1979). The Kama main channel forms a large arch with only 445 km separating the river source and its mouth (Shmidt 1928a, 1928b). Around 74 000 rivers and streams totaling 252 000 km in length are found in the Kama catchment. Shallow streams <10 km in length comprise the majority (94.5% of all rivers). The Kama River network lies in the Caspian Sea basin. The most dense river network (0.7–0.8 km/km2) is in the northeastern mountains. River density decreases to 0.3–0.4 km/km2 in the southwest because of the different climatic conditions (Agapitova 1975; Balkov 1979). River density within the Ural Mountains decreases from north to south. Rivers of the Kama flowing through the Eastern European plain have well-developed valleys with wide floodplains and terraced slopes. The rivers have low gradients, many branches, and numerous islands and shoals. Current velocities are low. With relatively rapid changes in elevation, river valleys become narrow, floodplains disappear, current velocities increase and rapids appear. Rivers in the upper Kama flow through narrow valleys. The headwaters of many present-day rivers meander along relict ancient valleys in intermontane depressions. Over 200 rivers flow directly into the Kama. Most of the right and some left tributaries flow from the north and are large deep lowland rivers. The others, mainly from the left side, originate from the Ural Mountains and are rapid and cold. The flow regime of most Kama rivers is characterized by a distinct spring flood from snow melt, rain-caused floods in summer-autumn, and low constant flow (140–160 days) in winter (Kuzin 1960; Agapitova 1975; Balkov 1978; Komlev & Cernykch 1984). Highest discharge is observed during peaks in the spring flood, and averages 70–80 L s1 km2 in the north, 50–55 L s1 km2 in the south, and 85– 100 L s1 km2 in the far steppic south due to intensive snow melting. In mountainous areas of the catchment, peak discharge can reach 150–200 L s1 km2, except in karstic

areas. Low discharge is found in winter, and averages 3– 4 L s1 km2 in the north and 0.5–0.7 L s1 km2 in the south and southwest. Small streams in basins <100 km2 can be intermittent and go dry in winter. Numerous reservoirs and smaller impoundments regulate the runoff in most rivers in the Kama catchment. The largest reservoirs in the catchment are the Kamskoye, Votkinskoye, and Nizhnekamskoye on the Kama. Each of these has a high water exchange. The Kama comprises 48% of the flow of the Volga (Chernyaev 2000). The average annual discharge of the Kama and Volga is 3750 and 3800 m3/s, respectively. 2.9.1.4.1 Temperature The thermal regime of the Kama is seasonal and temperatures are highest in July, averaging 18.8–20.2 C in different parts of the river. Year-to-year fluctuations in temperature are normal, on average >8 C during spring and early autumn and from 4.5–7.8 C in mid-summer and late autumn. According to long-term records, ice cover along the river occurs around 3–5 November in the upper Kama and 21–26 November in the lower Kama, lasting 142 and 174 days, respectively. Ice breakup occurs between April 16–30 in the lower Kama and April 22–May 1 in the upper Kama. Thermal conditions in the large reservoirs depend on reservoir morphology and hydrodynamics. In shallow areas of reservoirs with slow water exchange, spring warming of the water is earlier, whereas warming lags about 6–8 days in deep areas of reservoirs with fast water exchange. Surface water temperatures during the ice-free period follow air temperatures in the reservoirs, being highest in late July or early August at 24–28 C. Because of atmospheric circulation, surface temperatures in reservoirs during high-water periods are 2–2.2 C lower than during low-water periods. Thermal stratification usually develops in deep areas of reservoirs during periods of heating with a temperature difference of 3–7 C. Cooling begins in mid-August and is most intensive in September-October. In the reservoirs, average date of temperature transition >4 C occurs between October 7 and October 29 and the average date of ice cover occurs between November 2 and November 23. The duration of the ice-cover period lasts from 125 to 171 days. 2.9.1.4.2 Current All the types of currents known for artificial water bodies can occur in reservoirs of the Kama. Discharge currents and wind-drift currents are the most frequent (Devyatkova & Trutnev 1983). Discharge currents occur throughout the year, whereas wind-drift currents are observed only during the icefree period. Discharge currents are most typical in the upper basin, while wind effects and long waves caused by the irregular discharge regime of hydroelectric power stations are common near dams. Inputs of the Kama and Vishera rivers as well as reservoir levels influence flow velocity in the upper Kamskoye reservoir. High velocity currents that occur during the spring

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flood in the upper reservoir range from 120 to 188 cm/s and are similar to those in the upstream river. Current velocity slows to 40–100 cm/s by the end of June and to 10–40 cm/s in late summer early autumn. However, velocity can increase to 60–100 cm/s during floods from rain. Two-ply currents often develop in the middle lake-like part of reservoir. Flow direction and velocity in the upper layer depends upon wind velocity and direction and rarely exceeds 16–18 cm/s. At the same time, currents in deeper layers are relatively stable. Near the dam, discharge currents vary from 45–50 cm/s in spring to 10–15 cm/s in summer and autumn. In Votkinskoye reservoir, flow velocity also decreases downstream. In spring, velocity is about 1 m/s in the upper reservoir, 0.2–0.5 cm/s in the middle part of the reservoir, and 0.1–0.15 cm/s in the lower reservoir. Velocities are 2–3 times lower in summer. In the lower Kama below the town of Chistopol’ in the Volzhsko-Kamsky reach of Kuybushev reservoir, discharge velocity depends on the reservoir level but typically decrease downstream from 15–30 to <5–10 cm/s (Znamensky & Chigirinsky 1978). 2.9.1.4.3 Bottom Sediments Using Kamskoe and Vokinskoye reservoirs as examples, bottom sediments from upper areas of each reservoir to the dam change from sands of different size to silt (Kuznetsova & Rassadnikova 1983). Dirty sands and erinaceous silts represent an intermediate type of bottom sediment. In the central and near dam parts of reservoirs, grey, brown, and peaty silts are common. Near the dam, these silts look dark grey and almost black because of oil pollution. The layer of deposited silt ranges from 15 cm in the upper reservoir to 30– 34 cm in central and near-dam areas. The deepest silt layer, that is 80–100 cm, is found in bottom depressions. No particles are larger than 1 mm and particles 0.5–0.2 mm are most common. The average size of silt particles is 0.005 mm. Silicon acid is a basic component of all sediments, varying from 91–97% in sands to 50–70% in smallsize silt particles. Organic matter makes up <3% in sands, 2–26% in grey and brown silts, and 60% in peaty silts. Discharge from catchment area along with material from bank processing form most of the suspended matter inputs into Kamskoye reservoir, while materials of bank processing dominate suspended matter in Votkinskoye reservoir. 2.9.1.4.4 Hydrochemistry The mineralization and chemical composition of the Kama is variable along its course because of different environmental conditions and degree of human activities in the catchment. Soil cover exerts the most significant influence on river chemistry. Thus, a change from podsolic soils absent of soluble salts to dark grey soils of chernozems increases mineralization from the upper catchment to the mouth. Locally thick deposits of Perm sediments that include soluble salts such as sodium chloride, gypsum, anhydrites strongly

PART | I Rivers of Europe

influence the chemical composition of the water. In general, the Kama has higher contents of alkaline metals and chlorides than the Volga (Bylinkina et al. 1982a). The upper tributaries Veslyana, Lupya, Southern Keltma, contribute hydrocarbonate waters with low mineralization and high Ca2+ content. A distinctive feature of these rivers is the presence of high amounts of iron and organic matter from bogs. Mineralization increases in the Kama below the confluence of the large tributary Vishera. The rivers Yayva and Kosva contribute sulphate–calcium waters to the Kama. The large tributaries Belaya and Chusovaya influenced water chemistry in the middle Kama up to 1954 before construction of Kamskoye reservoir. The Belaya still affects mineralization levels in the lower Kama by doubling the sulphate content. Waters of the upper Kama are soft and have low mineralization that changes during the year from 32 to 163 mg/L. It ranges from 323 to 120 mg/L during spring and from 120 to 160 mg/L during summer. Anion composition is dominated by HCO (28–47% equivalent) and SO4 (2–18% equivalent). Cations consist of mainly Ca (22–44% equivalent) and Mg (4–18% equivalent or 0.2–7.5 mg/L). Na and K content ranges from 1.2 to 6.2 mg/L (1.6–13% equivalent). Water colour and permanganate oxidation are relatively high because of the extensive waterlogged forest-cover in the catchment. Colour ranges from 130–170 Cr–Co degree during spring high water to 50–80 Cr–Co degree during summer low water. During summer and autumn floods it can increase to 110–230 Cr–Co degree. Permanganate oxidation varies within a year from 5 to 30 mg O/L. Oxygen content is 4– 8 mg/L at the end of the ice-cover period and increases to 9–10 mg/L in spring and autumn. Nitrate content can reach up to 1 mg/L. In the lower Kama, water mineralization and chemical composition are quite different. Ion concentration increases significantly and total mineralization increases from 170 up to 700 mg/L. Prevalence of HCO and Ca decreases as Cl, Na and K simultaneously increase. Total mineralization and water hardness are higher in the lower reach. The pH values change within a year 7.0–8.0 becoming slightly higher in summer and lower in at high discharge. Water colour decreases at 40–60 Cr–Co degree. Permanganate oxidation is 8–16 mg O/l and bichromate oxidation is 16–30 mg O/L. Suspended matter influencing water transparency is much higher in spring (on average 22.2 mg/L in the middle and lower Kama) than in summer (7.6 mg/L). Mean transparency values calculated for the same periods are 0.75 and 1.3 m, respectively (Bylinkina et al. 1982a). Total nitrogen in the middle and lower Kama ranges from 0.6 to 1.5 mg/L in spring to 0.6 to 1.2 mg/L in summer with mean values of 1.11 and 0.74 mg/L, respectively. Nitrate content in the winter low-water period and during passage of the peaks in high water vary from 0 up to 5 mg/L. Nitrate may go to zero in summer as a result of uptake by plants. A similar picture is observed for nitrite, values ranging from 0.01 to 0.54 mg/L during the annual cycle. Total phosphorus content varies from 22–104 mg/L in spring to 20–146 mg/L

47

Chapter | 2 Volga River Basin

in summer. Phosphate content varies during the year from 0.005 to 0.065 mg/L. In general, waters of the Kama are suitable for technical and domestic water-supply after treatment and disinfection.

2.9.1.5 Aquatic and Riparian Biodiversity The flora and fauna of the Kama River is characterized by taxa of bogs, lakes, ponds, and former riverbed waterbodies variously connected with the main river channel and consist of typical potamoplankton and rheophylic zoobenthos. 2.9.1.5.1 Plants The Kama River valley lies in the middle and southern taiga forest biomes that become forest-steppe in its lower reaches (Isachenko & Lavrenko 1980). Vegetation in the headwater floodplain is characterized by a combination of osiers (Salix viminalis, S. acutifolia), and dark coniferous (Picea abies P. obovata, Abies sibirica) and paludal (Alnus incana, Betula pubescens, S. myrsinifolia, P. abies P. obovata) forests. In the middle Kama, this vegetation also includes broad-leaf and mixed broad-leaf forests of Quercus robur and Tilia cordata. Osier-beds and oak forests dominate in the lower Kama, and black alder (A. glutinosa) forests are widespread in the near terrace floodplain. Meadows now inhabiting deforested areas in the upper Kama are dominated mostly by small gramineous communities of Festuca rubra and Agrostis tenuis. Meadows in the middle Kama are covered by gramineous communities of Alopecurus pratensis, Phleum pratense, Agrostis gigantea, Festuca pratensis. In the lower Kama, narrow-leaved sedge (Carex acuta) is most common (Lipatova 1980). Osier-beds are common along the riverbanks, and aquatic vegetation is most developed in the Kama reservoirs. In reservoir bays, both semi-submersed vegetation of mostly Phragmites australis, Typha angustifolia, T. latifolia, Glyceria maxima, Equisetum fluviatile, and submersed plants represented by communities of yellow pond-lilies (Nuphar lutea), water lilies (Nymphaea candida), different pondweeds (Potamogeton perfoliatus, P. pectinatus, P. lucens, P. natans) and other hydrophytes (Ceratophyllum demersum, Myriophyllum spicatum, Stratiotes aloides) are abundant. Aquatic flora in the lower Kama reservoir is represented by 93 species of macrophytes. 2.9.1.5.2 Algae Prior to regulation, phytoplankton of the Kama consisted of typical potamoplankton with abundant algal flora (Tauson 1947). Bacillariophyta made up 235 species, Chlorococcales 131 species, Cyanophyta 65 species, Chrysophyta 9, Dinophyta 9, Euglenophyta 8, and Volvocales 5 species. Rhodophyta consisted of a single species, Chantransia chalybea Fries. Melosira varians, Aulacoseira granulata, A. italica (Ehr.) Sim. and A. italica var. tenuissima (Grun.) Sim.,

Diatoma tenuis, Synedra ulna, Asterionella formosa, Cocconeis placentula Ehr., Navicula cryptocephala K€utz., and N. radiosa K€utz. were most common. Representatives of Aulacoseira, Asterionella, and Cyclotella caused major algal blooms. Species such as Cyclotella meneghiniana, Diatoma vulgaris Bory, Fragilaria crotonensis, F. capucina, Cocconeis pediculus Ehr., and Nitzschia acicularis W.Sm. were less abundant. The mean density of the diatoms during summer was 1.13–4.52 106 cells/L. Green algae consisted of the genus Gloeococcus, Pediastrum, Scenedesmus, Dyctiosphaerium, and Monoraphidium. The blue-greens Anabaena, Aphanizomenon, and Microcyctis were locally abundant in summer. Seven periods in phytoplankton development could be distinguished over the annual cycle (Shtina 1968). Phytoplankton were almost absent in winter. In early spring, diatoms begin developing and attain high abundance along with other taxa in late spring. Many bottom forms can be found in the plankton. All groups of algae reach high abundances in early summer, and a single peak of phytoplankton of 11– 13 106 cells/L can be observed in August. In early autumn diatoms again become common, and a decrease in phytoplankton can be observed later. Presently, 242 taxa of algae have been recorded in the reservoirs of the middle Kama, including Bacillariophyta with 88, Chlorophyta 96, Cyanophyta 31, Euglenophyta 10, Chrysophyta 8, and Cryptophyta and Dinophyta 9. The community structure of phytoplankton remains relatively similar over time, although dominant groups differ during the year as well as from year-to-year (Tretyakova 1989). Bacillariophyta, mostly Aulacoseira italica, comprising up to 107 cells/L are most abundant in spring and blue-greens, numbering 5 105 cells/L, are most common in autumn. Mean phytoplankton biomass during 1975–1982 ranged from 1.16 to 2.34 g/m3, being dominated by Bacillariophyta (72–92%), Cyanophyta (2–10%), and Cryptophyta and Dinophyta (4–8%). 2.9.1.5.3 Zooplankton Zooplankton of the Kama before regulation consisted of 186 species, >60% represented by the Rotifera (Tauson 1947). Species such as Asplanchna priodonta, Filinia longiseta (Ehrenberg), Polyarthra dolichoptera Idelson, and Keratella cochlearis (Gosse) were most common, although the cladoceran Bosmina longirostris and copepods Mesocyclops leuckarti, Thermocyclops oithonoides were also abundant. Unfortunately, there is no data on zooplankton abundance in the Kama before regulation, and only summer peaks in near-shore areas and bays were recorded. Presently, the zooplankton community consists of Cladocera, Copepoda, and Rotifera at 200 species. Among these, Rotifera comprise 40–50% and Cladocera 35–40% of the community (Kortunova 1983, 1985; Dementieva 1985). Zooplankton biomass is made up mostly of Rotifera (>60%) from May to June and Crustacea from July to

48

September. The most abundant are Chydorus sphaericus, Bosmina longirostris, B. obtusirostris, Daphnia longispina O.F. M€ uller, D. cucullata, Mesocyclops leuckarti, Eudiaptomus gracilis, Eurytemora velox Lill., Cyclops vicinus, C. strenuus, Heterocope appendiculata, Leptodora kindtii, Bythotrephes longimanus. Rotifera such as Euchlanis dilatata Ehrenb., Asplanchna priodonta, Polyarthra major Bruck., Synchaeta sp. and Keratella species are also common. After regulation, Crustacea became abundant not only in near-shore areas but also in the main river channel. Mean zooplankton biomass between May and October varies from 1.0 to 4.6 g/m3 (Kortunova 1985, Dementieva 1985). The abundance of zooplankton can reach up to 2.7 million/m3 and 25.5 g/m3 in July in shallow areas in the upper and middle reaches of the river. Long-term records in Sylva bay of Kamskoe reservoir showed increases in zooplankton biomass from 1.4 g/m3 in 1957 to 2.3 g/m3 in 1978. 2.9.1.5.4 Zoobenthos Before regulation, zoobenthos in the Kama was similar to that in the Volga and Oka Rivers. The first information on zoobenthos for the entire Kama under natural conditions and without any anthropogenic impact such as hydropower stations was in 1925 (Behning 1928). Later, 296 taxa were recorded (Tauson 1947): among them Spongia with 1 species, Coelenterata 1, Nematoda 67, Oligochaeta 25, Hirudinea 6, Mollusca 20, Ostracoda 15, Isopoda 1, Amphipoda 6, Mysidacea 1, Decapoda 1, Plecoptera 4, Ephemeroptera 28, Trichoptera 17, Hemiptera 2, Odonata 1, Hydracarina 10, Bryozoa 1, and Diptera 89 including 84 species of Chironomidae. The most frequent chironomids were Chironomus f.l. semireductus, Beckidia zabolozkyi Goetgh. Tanytarsus gr. gregarius, Polypedilum gr. nubeculosum, Procladius, and Ablabesmyia spp. (Gromov 1951). Nematods were the next most speciose, including the widespread species Dorylaimus stagnalis Dujar., D. chrysodorus Bast., Ironus tenuicaudatus de Man., and Plectus cirratus Bast, and were especially numerous in tributary mouths. The most common oligochaetes in the middle Kama included Nais behningi Mich., Propappus volki (Mich.), T. newaensis Mich., and Limnodrilus hoffmeisteri Clap. (Svetlov 1936). Before regulation, Caspian crustaceans, that is Amphipoda, inhabited the middle and lower reaches of the Kama (Behning 1928; Gromov 1954). D. haemobaphes Eich. and the highly abundant Corophium curvispinum Sars inhabited pebble substrates, while other species, for example Stenogammarus macrurus Sars and P. sarsi Sowin., inhabited sandy and sand-pebble areas. Numerous colonies of Metamysis strauchi (Czern.) (Mysidacea) were found in pure sand habitats. The Caspian mollusc D. polymorpha (Pallas) was quite abundant in the lower Kama, especially in stone and pebble habitats (Behning 1928), and later, in 1939, it also occurred in the middle Kama (Gromov 1951).

PART | I Rivers of Europe

Presently, macroinvertebrates in the Kama consist of 250 species and among them Chironomidae make up 50%. Three taxonomic groups, that is Oligochaeta, Mollusca, and Chironomidae, comprise the most zoobenthos in terms of number and biomass. The most numerous are Chironomidae Polypedilum scalaenum (Schrank), P. bicrenatum Kieffer, Cryptochironomus gr. defectus, Dicrotendipes nervosus (Staeger), C. plumosus, Procladius ferrugineus, and Tanytarsus gr. gregarius, Oligochaeta T. newaensis, T. tubifex, Limnodrilus hoffmeisteri, and P. hammoniensis, Mollusca Viviparus viviparus, Valvata piscinalis, Pisidium sp., and D. polymorpha. Several Ponto-Caspian introduced taxa inhabit the present Kama River, including the mollusk D. polymorpha, polychaete H. invalida, and three crustaceans D. haemobaphes, P. sarsi, and Corophium curvispinum. These taxa are also found in zoobenthos of the Volga. The abundance of D. polymorpha became significant since late 1980s with local biomasses of 200–370 g/m2. Although uncommon, H. invalida had been found in the lower Kama. The Chinese crab E. sinensis had been recorded in the upper Kamskoye reservoir in 2001. The total biomass of zoobenthos in the Kama varies from 5 to 31 g/m2, and without mollusks is 2–4 g/m2. High biomass values over 60 g/m2 typically occur in the upper Kama. Long-term observations showed increases in the abundance of the mollusks Viviparus viviparus and D. polymorpha. At the same time, Oligochaeta and Chironomidae decreased in biomass. Average zoobenthic biomass in Votkinskoye reservoir (2003) is 141 g/m2, while it was 12–24 g/m2 in the Kamskoye reservoir in 2002–2004. 2.9.1.5.5 Fish Studies of the fishes in the Kama River has been carried out for the last two centuries. The first faunistic descriptions did not contain complete information on fish species and differed greatly from modern taxonomy. However, 24–43 fish species were recorded from those times. Before filling of the Kamskoye reservoir in 1954, 42 fish species had been recorded in the middle Kama. After dam construction in the middle Volga and Kama River, anadromous fish such as lamprey, beluga, Russian sturgeon, two species and one subspecies of herring, sheefish, and Caspian salmon were lost from the fish community. Concomitantly, catfish disappeared and the natural habitat of brook trout was reduced. As a result, only 32 fish species were found in the middle Kama and its tributaries in the 1970s. Further modifications in the fish community were realized with the appearance of chub and Amur sleeper, by natural recolonization of catfish, and invasion of sardelle from the Volga basin. The white-finned gudgeon inhabits a number of lower reaches of tributaries, and brook trout, Volga zander, spine fish, and round bullhead can now be found in fish catches. Presently, there are 41 fish species in the upper and middle Kama. During the two centuries of observation, fish composition in the Kama changed little, although significant

49

Chapter | 2 Volga River Basin

modifications occurred in structure of communities. As in earlier times, the Ponto-Caspian freshwater species make up most of the species, being dominated by bream, whiteeye bream, blue bream, silver bream, rudd, asp, bleak, chub, sneep, sabrefish, belica, and chub. The boreal plains complex is made up of pike, golden and silver crucian, roach, ide, dace, gudgeon, lake minnow, tench, spined loach, perch, and ruff. The boreal sub-mountain complex consists of beeper, brook trout, grayling, riverine minnow, loach, and bullhead. The upper tertiary plain complex consists of starlet, sazan, catfish, loach, zander and Volga zander. The remaining fish taxa are represented by 1–3 species. The burbot comprises the freshwater Arctic group, sardelle, spine fish, and round bullhead form the Ponto-Caspian sea group, the Amur sleeper forms the Chinese plain group (Dgebuadze & Slyn’ko 2005).

2.9.1.6 Management and Conservation There are 12 administrative regions with a total population of over 29 million in the Kama catchment. Among them, >10 million (40%) inhabit the adjacent riverine floodplain. The catchment is rich in minerals and several thousand mines are active here. Ferrous and non-ferrous metallurgy, coal industry, oil processing, and engineering and chemical industries thrive in the catchment. Forests occupy about 14 million ha of the catchment area. Kama reservoirs, similar to the Volga reservoirs, had been built for multi-purpose goals of water supply, water transport, and timber rafting, among others. Industrial and municipal discharge from river-side cities are the main sources of pollution. Three reserves are found in the Kama catchment (Sokolov & Syroechkovsky 1988, http://www.sevin.ru/ natreserves/). The Volga-Kamsky Reserve founded in 1960 is located in Tatarstan and occupies 80 km2. The Basegi Reserve (1982, 190 km2) and the Vishera Reserve (1991, 2400 km2) are situated in the Perm’ oblast. Most of the Volga-Kamsky Reserve is covered by forests of taiga, oak, and steppe. Flora of the reserve consists of over 840 species of plants. Faunistically, about 200 species of birds, 55 species of mammals, 30 species of fish, and a number of amphibians and reptiles inhabit the reserve. Both flora and fauna include rare species registered in the Red Book of Russia.

2.9.2. The River Oka 2.9.2.1 Introduction The Oka is a relatively large river in Russia, and one of the two largest tributaries of the Volga. The origin of its name is not exactly known, although the most likely are the Lithuanian word ‘aka’ meaning ‘spring’ or Finnish word ‘joki’ meaning ‘river’. Before Slavic colonization, the upper Oka was inhabited by Baltic tribes (polekhi) and

the middle and lower Oka by Finnish tribes (meshchera, muroma). Sites of Stone Age man were discovered on the left bank of the Oka between the Dmitriyevy Mountains and Murom. In 15th–16th century the river acted as the defence line of the Moscow State against Tatars raids from the south.

2.9.2.2 Paleography of the Catchment The present Oka catchment was formed in the post-glacial period. The catchment occupies the central part of the Russian plain that is covered by a layer of sedimentary rocks. Within the Moscow syncline, this sedimentary layer exceeds 3000 m in depth. Lowlands, at <200 m asl, occupy a large part of the catchment. Devonian and Carboniferous deposits lying near the surface in the upper catchment strongly influence the chemistry of the Oka. Devonian deposits are composed of mainly limestone and dolomite, and inclusions of gypsum and anhydride in some places.

2.9.2.3 Physiography, Climate, and Land Use The source of the Oka is in the Central Russian upland at 226 m asl (Srednerusskaya Vozvyshennost’) and the lower river flows though the Oka-Don lowland. The Oka essentially flows through the geographical center of the European part of the Russian Federation. The river is 1500 km long with a catchment area of about 246 000 km2. The northwest part of the catchment lies in the subzone of mixed coniferous- broad-leaf forests and the southeast part along the boundary of the steppe and forest-steppe zones. Forests occupy 5–25% and agriculture >50% of the catchment area (Yablokova 1973). The climate of the catchment is continental-temperate and is similar to that of the middle Volga. Mean air temperature in January ranges from 11 C in the north to 9 C in the south; and from 17 to 20 C, respectively, in July. Annual rainfall averages 450–680 mm, decreasing from northwest to southeast.

2.9.2.4 Geomorphology, Hydrology, and Biogeochemistry The Oka flows from west to east. Headwaters of the river are in the forest-steppe black earth (chernozem) lands of the Kursk province. Headwaters are fed by underground springs from Devonian deposits. Banks of the upper Oka are steep, and its width up to Kaluga varies from 60 to 160 m. Its right bank is for the most part higher than the left. From its headwaters, the Oka enters an area of coal mining, changing its direction at right angles several times. In this section, together with its tributary Ugra, the river flows through the Central Russian upland and chernozem forest-steppe zone. Downstream from the confluence with the Moksha River, the Oka leaves the coal-mining area and enters a region of

50

Upper-Jurassic sandstones. Here the right bank, ‘Ryazan side’, is high and undercut, whereas the left bank, ‘Meshchera side’, is low, wooded and boggy. A wide bottomland of vast coniferous forests lies on the Meshchera side with a base of impervious Jurassic clays covered with layers of sand. The Ryazan side is forest-poor and incised with gullies that stretch to the Pronya confluence. The Oka then turns north and then acutely southeast. The middle Oka transverses the Kasimovskaya limestone ridge made up of carboniferous rocks. Downstream from its confluence with the Moksha, the river flows north and then northeast to its mouth. Here the left side is bounded by the Dmitriyevy and Bolotovy Mountains and the right by the historically significant, coniferous-forest lowlands of Murom. Downstream of the town of Murom, the left bank lowers and the right is composed of Permian marls and gypsums. Downstream from the town of Pavlov is the steep Gorbatovskaya bend where the tributary Klyazma enters from the left. Between the tributary and Gorbatovskaya bend, the Oka runs through a wide depression called Oka gate. Further downstream, the left bank is low, whereas the right-bank borders the Dyatlovy Mountains. At the confluence of the Oka and Volga sits a large industrial and cultural center, the city Nizhni Novgorod. The total number of rivers and streams in the catchment is >19 000, and about 1600 of these are >10 km (Yablokova 1973). Left-side tributaries drain mixed coniferous–deciduous forests of sod-podzolic soils of different grain sizes mixed with alluvial soils in floodplains and bog-podzolic soils in poorly drained areas. Right-side tributaries drain forest-steppe where soils are mostly grey forest soils and leached chernozems. Floodplains on the right side of the river are heavily tilled. The flow regime of the Oka has a pronounced spring flood, and summer and winter low flows with periodic floods from rain events. Spring runoff contributes on average 58% (April–May), winter 14% (January–March, December), and summer–autumn 28% (June–November) to annual discharge. Minimum discharge usually occurs in February (Yablokova 1973). Mean annual discharge is 39.3 km3, maximum 58.3 km3, and minimum 21.6 km3. Maximal mean monthly discharge in May is 12 500 m3/s, a minimum of 827 m3/s occurs at a mean annual discharge of 1240 m3/s. Average annual discharge ranges from 4.9 L s1 km2 in the upper Oka to 5.4 L s1 km2 in the lower river, or 0.98– 600 m3/s, respectively. Year-to-year fluctuations in discharge before the Volga was regulated showed irregular cycles of 3–5-year long high-water periods (i.e. 1905– 1909, 1915–1917, 1926–1929) and 3–11-year long lowwater periods (i.e. 1910–1914, 1918–1925, 1934–1945, and 1948–1950) (Yablokova 1973). 2.9.2.4.1 Temperature The highest water temperature in the river is in July, averaging 21 C and ranging from 18.5 to 24.6 C. The river begins to freeze-over in late November early December and lasts on

PART | I Rivers of Europe

average 125–140 days. Ice thickness varies on average 45– 60 cm but can reach 95 cm in some years. In the upper river near the city Orel, the Oka is ice-free on average 235 days (early April to late November) and 210 days in its lower reach between Murom and Nizhni Novgorod. 2.9.2.4.2 Biogeochemistry The lower Oka belongs to the hydrocarbonate–calcium group. Water mineralization is high due to direct contact of surface waters with carbonates and inputs of highly mineralized ground waters. Mineralization is 260–570 mg/L during most of the year, decreasing to 130–140 mg/L in spring during high flows (Alekin 1948). From the source to its mouth, mineralization continuously increases due to dissolution of surface Dyas deposits, transition of podzolic-sandy soils in the north to gray podzolic soils of forest-steppe and rich chernozems in the south, and a decrease in rainfall from north to south concomitant with an increase in evaporation rate. Mineral content is mainly from SO2 and Ca (Alekin 1948). A dominance of HCO is clearly pronounced in the anion composition of the water, representing from 40–45% equivalent in the upper river (by Orel) to 26–35% equivalent in the lower river (by Nizhni Novgorod). In contrast, sulphates increase from 5–8% equivalence in the upper river to 15–20% equivalence in the lower river. Water pH during the ice-free period is 6.2–8.1 and highest in summer. Average turbidity ranges from 1400 g/m3 in the upper river to 190 g/m3 in the low river (Yablokova 1973). Low water colour (15–25 Cr–Co degree) is observed during winter. Water oxidization changes from 2–8 mg/L in summer to 4–19 mg/L in spring due to organic matter inputs from melting snow. Dissolved oxygen varies significantly during the year. Total nitrogen content averages 1.49 mg/L (Alekin 1948; Zenin 1965). Total phosphorus content at the mouth varies from 0.208 to 0.304 mg/L, total nitrogen from 1.80 to 3.21 mg/L, and carbon from 5.7 to 11.8 mg/L. Bottom sediments are composed of mostly small particles <1 mm to 5–10 mm pebbles, although sands dominate (Yablokova 1973).

2.9.2.5 Aquatic and Riparian Biodiversity 2.9.2.5.1 Plants The Oka River valley lies in the broad-leaf forest biome (Isachenko & Lavrenko 1980). The floodplain is vegetated by a combination of osiers (Salix acutifolia, S. triandra, S. viminalis), black poplar (Populus nigra), white willow (S. alba), elm (Ulmus laevis), oak (Quercus robur) and black alder (Alnus glutinosa) mixed with meadows. Widely distributed are original Beckmannian (Beckmannia eruciformis) meadows (Isachenko & Lavrenko 1980). Riverbanks are covered by a prevalence of Salix triandra and S. viminalis. Aquatic vegetation is most diverse in the headwaters, although well-developed communities are found in

51

Chapter | 2 Volga River Basin

numerous former riverbeds in the lower river comprising semi-submersed plants (Phragmites australis, Typha angustifolia, Scirpus lacustris) and submersed plants (Nuphar lutea, Nymphaea candida, Potamogeton perfoliatus, P. pectinatus, P. lucens, P. natans, Ceratophyllum demersum, Myriophyllum spicatum). Water-chestnut (Trapa natans s. l.) of different forms also is widely distributed in these former riverbeds. 2.9.2.5.2 Algae Phytoplankton of the Oka has been studied since the 1920s (Pavlinova 1930; Yesyreva 1945, 1968; Mokeeva 1964; Kuzmin & Okhapkin 1975; Vodeneeva 2000), and includes 380 species, varieties and forms with a predominance of green algae (188 taxa), diatoms (80 taxa), and blue-green algae (38 taxa). Most common taxa include Scenedesmus, Trachelomonas, Nitzschia, Aulacoseira, Stephanodiscus, Dinobryon, Navicula, Phacus, Chlamydomonas and Kirchneriella. Taxonomic richness peaks in July–August during warm water temperatures with a pronounced increase in the diversity of green algae. Diversity is much lower in spring and autumn. Seasonally, phytoplankton biomass peaks in summer and at times in autumn. Diatoms dominate total biomass, ranging from 2.2 up to 28.2 g/m3 during 1971–1998 at the river mouth, when total biomass was 2.4–29.0 g/m3, respectively. Small-celled green algae, mainly Chlorococcales, also are common and can make up to 17% (usually 4–7%) of total biomass. Phytoplankton biomass can reach 50.0 g/m3 during algal blooms in spring and summer. A bloom of Stephanodiscus (S. hantzschii, S. minutulus, S. invisitatus, S. neoastraea) usually occurs in spring after ice-out. The alga Cyclotella meneghiniana as well as the diversity and biomass of Chlorococcales increases in July–August. Phytoplankton biomass decreases to 1–2 g/m3 or more in September–October and <1 g/m3 before the river freezes over. As a rule, an under the ice bloom is absent. In early records (ca. 1920s) with few anthropogenic impacts on the river, diatoms Melosira = Aulacoseira, Fragilaria, Asterionella together with Chlorococcales dominated the algal community and phytoplankton biomass was 1 g/m3. Although diatoms and Chlorococcales remain dominated in the river today, the composition of dominating species has changed to species of Stephanodiscus and Cyclotella meneghiniana that are indicators of eutrophic conditions. Phytoplankton biomass also increased 20-fold from 1926–1927 to 1970–1980s, and the river estuary changed from oligo-b- mesosaprobic to b-amesosaprobic. 2.9.2.5.3 Zooplankton Zooplankton in the river consists of about 60 species. Most of these are eupelagic and widespread in waters of the temperate zone. Nevertheless, a number of species, dominated by

Rotifera Brachionus calyciflorus, are typical representatives of running waters. A number of littoral inhabitants and phytophilic forms such as Platyas quadricornis (Ehrenberg), Graptoleberis testudinaria (Fisher), Chydorus ovalis Kurz, Pleuroxus aduncus (Jurine), Alona quarangularis (O.F. M€uller), together with the near-bottom Oxiurella tenuicaudis (Sars) usually can be found. Rotifera make up the largest number of zooplankton species, consisting mainly of the genus Brachionus. Among them, B. calyciflorus has several morphological forms (i.e. B. c. calyciflorus Pallas, B. c. dorcas Gosse, B. c. anuraeiformis Brehm, B. c. amphiceros Ehrenberg, and B. c. spinosus Wierzejski), B. angularis, B. diversicornis (Daday), B. qudridentatus, B. urceus (L.), B. leydigi Cohn., B. budapestiensis Daday. There also are some other widespread Rotifera such as Keratella cochlearis, K. quadrata, Filinia longiseta, Polyarthra minor Voigt, and Asplancha priodonta. Crustacea also have high species richness, and commonly include species such as Bosmina longirostris, Daphnia cucullata, Diaphanosoma brachyurum (Lievin), Ceriodaphnia pulchella Sars, C. sphaericus (O.F. M€ uller), Alona rectangula Sars, and Ceriodaphnia quadrangula (O. F. M€uller). Copepoda have the least number of species, and is mainly composed of Cyclops strenuus, Mesocyclops leuckarti, Thermocyclops oithonoides, Eudiaptomus gracilis and E. graciloides. Since 2000, major changes in zooplankton composition such as a reduction in the number brachionid species have taken place along with records of several new limnophilic species, that is Euchlanis dilatata, Bosmina coregoni, Leptodora kindtii, and Heterocope appendiculata. 2.9.2.5.4 Fish The Oka, being unregulated by dams, has a rheophilous complex of fish species. Icthyofauna are represented by 39 species, 9 of these typical rheophils. The river has a selfreproducing population of sterled sturgeon. Common fish species in the middle and upper Oka are gudgeon, ide, dace, rudd, Volga nase, minnow, bystranka, and zherekh. Today, the icthyofauna has changed due mainly to the disappearance of Caspian anadromous species and much lower abundances of valuable rheophilic species (sterled, large cyprinids and percids). The presence of the Amur sleeper in the Oka basin was first recorded in the 1970s and now this species can be caught in several sections of the river itself (e.g. around Kaluga). Monitoring catches also show the presence of Asian carp and silver carp in low numbers (<1% of the catch). However, there are no self-reproducing populations of these species in the river, and the main sources of these fish are two reservoirs (Lyudinovskoe and Brynskoe) on tributaries of the Oka where these fish are cultured. The expansion of crucian carp is notable, and is consistently in fish catches in the Oka. Its abundance in the region’s waterways is growing (Dgebuadze & Slyn’ko 2005).

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2.9.2.6 Management and Conservation The Oka catchment has a high population density. The river flows though 7 administrative units and 11 cities/towns are along its banks. Six of these towns have populations of 100– 500 000 and Nizhni Novgorod has over 1 298 000 inhabitants. Industrial and municipal discharge from the cities is the main source of water pollution. The Oka is navigable and is a part of the water network connecting Moscow with the Volga region. Water monitoring of the Oka is under regional control, and the water quality is satisfactory. However, its use for water supply is possible only after proper purification (Yablokova 1973). Three reserves lie within the Oka catchment. The Prioksky Terraced State Wildlife Biosphere Reserve was founded near Moscow in 1948 and occupies 50 km2. Around 130 bird species, 54 mammal species and >900 species of plants are registered in the reserve (Sokolov & Syroechkovsky 1989, http://www.zapovednik.com). Plants of different climatic zones from south taiga to steppe are found here, as well as the southern limit of fir. The reserve has a European bison farm. Oksky State Wildlife Biosphere Reserve was established in 1935. It occupies 557 km2 and is in southeast Meshera in the Ryazan province. The reserve is one of 14 world reserves labelled in UNESCO documents and awarded the diploma of Council of Europe (Sokolov & Syroechkovsky 1989; Belko 2004, http://www.zapovednik.com). More than 800 species of higher plants, about 500 species of mosses, and 150 species of lichens grow in the reserve. Around 57 species of mammals, about 260 bird species, 10 species of amphibians, 6 species of reptiles and 39 fish species live here. The first

PART | I Rivers of Europe

Russia Central Ornithological Station and farms for rare species of crane, rare birds of prey and pure-blooded European bison Bison bonasus bonasus L. were established in the reserve. Up to 1000 individuals of one of the rarest animal species, desman Desmana moschata L., are recorded from water bodies in the reserve. The Mordovia State Reserve, 321 km2, was established in 1935 in the Moksha River (left tributary of the Oka) catchment of the Mordovia Republic. Coniferous forests grow here with trees up to 350-years old. The flora are represented by more than 1000 species of plants (749 vascular plants, 77 mosses and 83 lichens), and 59 species of mammals and 194 bird species live in the reserve (Sokolov & Syroechkovsky 1989, http://www.zapovednik.com).

2.9.3. The River Sheksna 2.9.3.1 Introduction The Sheksna River (Photo 2.6), a tributary of the Volga, flows through Vologda province of Russia. Historically, the Sheksna was called Shekhsna, as mentioned in Nestor’s chronicle in 1071. The river has served as a water-way from the Volga to Onega, Ladoga and Velikiy Novgorod. Finnish tribes settled on its riverbanks. The Sheksna was part of the Marin system, and presently is included in the Volga-Baltic water-way and North-Dvina system. No large towns or major agricultural developments occur in the Sheksna catchment, thus anthropogenic impacts on the river are relatively small. Data presented in this chapter were based mainly on the book Modern State of Sheksna Reservoir Ecosystem (Litvinov PHOTO 2.6 Sheksna River near the village of Goritsy (Photo: V. Lazareva).

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Chapter | 2 Volga River Basin

2002) and Hydrometeorological regime of lakes and reservoirs in the USSR (Vikulina & Znamensky 1975).

2.9.3.2 Paleography of the Catchment Area The Sheksna catchment lies in the boreal biographic region, and was formed by the influence of glaciation, in particular the Valdai glaciation. However, the main features of the landscape were formed before the Ice Age from erosional processes. The influence of glaciation was manifest in grinding bedrocks from the surface, smoothing benches, and piling loose material in some areas. Young post-glacial formations have also developed as a result of processes associated with rivers and lakes.

2.9.3.3 Physiography, Climate, and Land Use The catchment is in the northwest part of the Russian plain with a crystalline foundation formed by Precambrian rocks to depths of 2 km covered by a layer of Paleozoic sedimentary rocks. Most of the catchment is covered by Middle and Upper Carboniferous sediments overlaid by friable Quaternary deposits (Pakhtusova 1969). The Quaternary deposits are represented mainly by glacial and water–glacial formations of different age. The catchment encompasses the Belozersk plain and is transected by two undulating ridges in the shape of arcs. One arc, Magersk-Andomskaya, separates the Belozersk plain from the adjacent Onega depression, whereas the other, Belozersk-Kirillovskaya, arcs around the Beloye Lake depression. South of Belozersk is the Andogsk ridge, formed just before the last glaciation. Altitudes here range from 111 to 304 m asl. The geographical location of the catchment favours intrusion of arctic, polar (of middle latitudes) and, at times, tropical air masses. Arctic air masses bring anti-cyclonic weather. In winter, air temperature drops sharply, and frosty sunny weather occurs. Frosts are common in spring and autumn (Adamenko & Malinina 1981). The average annual air temperature is 2–4 C. The coldest month is January (February in some years) with a monthly average temperature of 11.9 C, fluctuating from 4.4 to 20 C. In winter, minimum temperatures can reach 46 to 49 C, but thaws occur each year. Monthly average air temperature in July is 16.7 C. The lowest average temperature recorded in the past 50 years was 13.4 C (1956) and the highest was 20.8 C (1972), although daily values can exceed 30 C. Air temperature remained >0 C for the town of Belozersk for 205 days. The transition to >0 C average daily temperature occurs around April 8 and to <0 C around October 30. The frost-free period lasts from mid May to mid September, for 104–122 days. Mean annual rainfall is 632 mm, 422 mm of this between April and October and 210 mm during winter. Southerly and southwesterly winds prevail during the year (41% of the time), and northerly winds are more frequent during the warmer

months, especially May–June. The wet climate (50% evaporation rate) and flat relief promote bog development, mainly raised bogs, flat bogs and transition bogs. The area is mostly waterlogged, although unevenly distributed. On average, marshland accounts for 13% of the catchment, forests 81%, and lakes 10% (Vikulina & Znamensky 1975).

2.9.3.4 Geomorphology, Hydrology, and Biogeochemistry The Sheksna catchment is within the middle taiga zone of mostly coniferous forests with some broad-leaf trees. The Sheksna begins in Lake Beloye, flowing then into the Sheksna reach of Rybinsk reservoir. Most of its water originates from snowmelt. The catchment area is 20 755 km2, and lies mainly along the meridian line. The northern boundary is at latitude 60 550 N and the southern boundary is at 59 300 N, extending about 300 km from north to south and 180 km from west to east. The lower river is regulated by the dam of Sheksna Hydroelectric Power Station built in 1963. The resulting reservoir also influenced Lake Beloye 120 km upriver from the dam, and the length of the river decreased by about 300 km after Rybinsk reservoir was filled. Its major tributaries include the Kovzha from the west, and Siz’ma, Pid’ma, and Bolshoi Yug from the east. 2.9.3.4.1 Hydrology The catchment is in a zone of excessive moisture, with a mean annual discharge averaging 9 L s1 km2. Rivers in the catchment show significant variation in runoff over the year. On average, spring runoff from snowmelt contributes 50–70% to annual flow, summer–autumn runoff 20–32%, and winter runoff 5–12%. The volume of spring runoff decreases from April to May in rivers with a low ratio of lake surface to drainage area. Maximal spring runoff of rivers in the lacustrine-karst zone occurs in May. Two periods of low runoff, summer-autumn and winter, are typical for rivers in the catchment. Summer-autumn low-flows usually begin in July and ends in September–October, averaging 80–90 days. Winter low-water lasts from late November–early December to late March–early April, averaging 120–140 days. The lowest water is observed in February–March. From 1964 to 1992, average annual discharge at the Sheksna power station was 160 m3/s, with a maximum of 184 m3/s in 1990. A maximum average monthly discharge of 631 m3/s was recorded in May 1992 and a minimum of 22 m3/s occurred in March 1984. In free-flowing sections of the river, velocity can reach 30– 70 cm/s (Vikulina & Znamensky 1975). 2.9.3.4.2 Temperature Based on long-term data, ice breakup begins around April 17–27, but as early as March 10–April 5 and as late as April 29–May 7. The incremental increase in temperature in early May is 3.5 C with a maximal incremental increase of 3.6–

54

4.1 C in mid May. The inter-annual fluctuation in water temperature ranges from 2.3 to 14 C. The summer warming period lasts until late July when surface temperatures reach 19.6–19.9 C (maximum 22 C). The autumn cooling period begins in early August, decreasing by about 0.5 C over 10 days. The rate of cooling by late September is 3 C over 10 days. The average date of first ice appearance is November 20, but can be as early as October 26 and as late as January 6.

PART | I Rivers of Europe

are characterized by low total nitrogen and high total phosphorus values, although phosphates are low (Bylinkina et al. 1982b). The hydrochemistry of the Sheksna has not undergone considerable change since the 1970s (Litvinov 2000).

2.9.3.5 Aquatic and Riparian Biodiversity 2.9.3.5.1 Plants

2.9.3.4.3 Bottom sediments The filling of the reservoir for the Sheksna Hydroelectric Power Station turned lowland areas into swamps and drowned floodplain forests. A layer of sand deposits formed in the littoral zone up to 2-m water depth from bank and bottom erosion, and a layer of sand with peat particles formed in deeper areas. The peat was derived from flooded swamps of the Sheksna-Sizmensk lowland where floating mats of peat were commonly observed. The bottom of narrow sections is composed of sands, and pebbles, large boulders and clay outcroppings in some places. The sedimentation rate near the dam is 1.5 mm/year on average, varying from 0.6 in the littoral zone to 20 mm/year at deeper depths. Depending on the sediment type, organic matter content ranges from 1.0 to 1.5% in sand, 2.0–2.8% in siltsand, 5.5–10.4% in sand-silt, 9.5–15.3% in clay-silt, 30– 40% in silt-peat, and up to 60% in peat-silt. Sedimentation rate near the river source is 0.5–0.8 mm/year.

Much of the Sheksna floodplain is inundated by waters of the Sheksna and Rybinsk reservoirs. The banks of the reservoirs are mostly covered by meadows or osier-beds of Salix cinerea, S. triandra, and S. viminalis. Osiers also cover the banks of most islands, although low parts of islands and low banks are covered by Phalaroides arundinacea, Glyceria maxima, Carex acuta, and hygrophilous and marsh motley grass. Aquatic vegetation in running waters of the reservoirs is poor, mainly communities of clasping-leaf pondweed (Potamogeton perfoliatus) and reed (Phragmites australis). Vegetation in bays and shallows of the reservoirs is more diverse. Here dominate clasping-leaf pondweed and reed, but also swamp horse-tail (Equisetum fluviatile), broad-leaf cattail (Typha latifolia), star duckweed (Lemna trisulca), bur-reed (Sparganium emersum), manna-grass (Glyceria maxima), Old-World arrowhead (Sagittaria sagittifolia), and water milfoil (Myriophyllum spicatum) are common. Aquatic vegetation in the Sheksna reservoir is represented by only 97 macrophyte species (Litvinov 2002).

2.9.3.4.4 Hydrochemistry Hydrochemical conditions in the Sheksna are influenced by surface inflow from the forest zone containing low contents of soluble mineral compounds and high content of humic organic matter. River chemistry is mainly determined by water masses from Lake Beloye. The total salt content ranges from 77 to 135 mg/L in spring, 124– 170 mg/L in summer, and 128–173 mg/L in winter. The salt concentration increase is from carbonates and sulphates, as well as groundwater inputs and local tributaries during low flows. Hydrocarbonates dominate waters in the northwest part of the catchment, whereas groundwaters with sulphate, calcium, and magnesium are found in the southeast (Savinov & Filenko 1965). Suspended sediments originate from Lake Beloye where high mixing often occurs during the ice-free period. Sediment levels varied from 11 to 57 mg/L before regulation, and are similar today (Vikulina & Znamensky 1975). Suspended sediment levels decrease quickly downstream of the lake. Water transparency is about 1 m, reflecting changes in suspended sediments. COD values equal 34 mg O2/L, corresponding to 13 mg/L organic carbon. Dissolved oxygen reaches 92–98% saturation in spring and autumn, while super-saturation is observed in summer. Water colour varies from 25 to 185 Cr–Co degree, being 50–70 degree on average from the high concentrations of humics. Nutrients

2.9.3.5.2 Algae From 1955 to 1995, 923 species (1155 species, varieties and forms) of phytoplankton were recorded in the Sheksna reservoir. Diatoms show high seasonality in the reservoir (Litvinov 2002). In contrast to the Volga reservoir, a spring peak in phytoplankton biomass is less pronounced. In spring, Stephanodiscus minutulus S. neoastraea, Aulacoseira islandica, Asterionella formosa dominate. Total biomass increases in summer when diatoms and cyanobacteria (blue-greens) are predominant. The phytoplankton composition is mainly composed of Aulacoseira granulata, Aulacoseira subarctica, Cyclotella radiosa, Tabellaria fenestrata, Asterionella formosa, Stephanodiscus binderanus, S. neoastraea, Aphanizomenon flos-aquae, Microcystis aeruginosa, M. wesenbergii and species of genus Anabaena. In the summer of 1990, the abundance of non-heterocystus cyanobacteria Gloeotrichia echinulata (J.S. Smith) P. Richt, Microcystis holsatica, small-celled cryptomonads (Chroomonas acuta) and the euryhalyne diatom Actinocyclus normanii increased (Litvinov 2002). Of note is the presence of large-celled diatoms of Cymatopleura and Gyrosigma in Sheksna reservoir. The change in community structure of phytoplankton in Sheksna reservoir during the last few years is similar to those observed in the Volga reservoir. Average annual phytoplankton biomass during the ice-free period from 1955 to 1977 ranged from 0.8

55

Chapter | 2 Volga River Basin

to 4.9 g/m3 with maximal values in 1965 and 1976. In 1994– 1995, biomass did not exceed 4 g/m3. 2.9.3.5.3 Zooplankton Zooplankton consists mainly of Cladocera, Copepoda and Rotifera, with about 120 species. Crustacea make up 60% of the species and constitute >90% of the biomass. Bosmina coregoni gibbera (Schoedler), B. longispina, B. crassicornis, Daphnia galeata, D. cucullata, D. cristata, Diaphanosoma brachyurum, D. orghidani, Mesocyclops leuckarti, Thermocyclops oithonoides, Eudiaptomus gracilis, Heterocope appendiculata, Limnosida frontosa, Leptodora kindtii, Bythotrephes longimanus are most common. Small organisms, that is Conochilus unicornis, C. hippocrepis (Schrank), Keratella cochlearis, and Kellicottia longispina Kellicott are numerous Rotifera, making up to 50 000/m3. Non-native species of Cyclops scutifer Sars and Asplanchna herricki Guerne that belong to the northern lacustrine complex probably came from water bodies of the catchment from 1960 to 1980. The southern species, Diaphanosoma orghidani, found in 2005 likely came from the upper Volga, it numbers about 2000/m3. Average zooplankton abundance during May–October is 40 000/m3 and biomass is 0.7 g/m3. Highest values (156–235 000/m3 and 2.8–4.0 g/m3) are usually observed in June–July in the lower river. 2.9.3.5.4 Zoobenthos Presently, 170 species of macrozoobenthos have been found in the flooded channel of the Sheksna (Bakanov 2002). The majority, up to 83% of the total, is made up by chironomids (60 species), mollusks (40), and oligochaetes (37). Oligochaetes Tubifex newaensis, T. tubifex, Limnodrilus hoffmeisteri, L. udekemianus Claparede, Potamothrix hammoniensis, and P. moldaviensis, chironomids Chironomus plumosus, and Procladius choreus, mollusks D. polymorpha and large representatives of Pisidiidae, the genus Amesoda and Sphaerium dominate zoobenthos numbers and biomass. The highest biomass of macrozoobenthos at 145– 200 g/m2 was found near the dam at a depth of 18–22 m. The chironomid Chironomus plumosus and oligochaete Tubifex tubifex made up most of the biomass (about 75%). Only one species under danger of extinction, mollusk Anisus vorticulus, was not included in the fauna list of macroinvertebrates in the Sheksna. Along the entire river, the nonindigenous Baikal amphipod Gmelinoides fasciatus was the single representative of crustacean (Bakanov 2002). In 2005, average macrozoobenthos biomass in the Sheksna reservoir was about 6 g/m2, while upstream of Cherepovets, in the river with flowing water it was 0.5–3.6 g/m2. 2.9.3.5.5 Fish Ichthyofauna of the Sheksna traditionally was of a mixture of rheophilous species (pike, perch, roach, ide, ruffe, bleak, etc.) and limnophilous species coming from Lake

Beloye. The first marked decrease in the number of species and their composition was observed in 1896 after the dam that separated Lake Beloye from the upper Volga basin was built, leading to the disappearance of Russian sturgeon, beluga, sterled and sazan. In 1970s, the number of species was 29, 25 in the 1980s, and 22 species are presently observed in catches. The following species are no longer observed since 1970s: minnow, grayling, zanthe, wels catfish, chudskoi whitefish, ludoga whitefish, smelt and river lamprey. Tench, eel and peled were observed at single times. In the 1980s, these species along with belica and loach have disappeared, and elets, chub, crucian carp, spined loach and bullhead became rare. In the 1990s, these latter species became extinct and white-eye bream, rudd, gudgeon, ide and zherekh were counted as rare. Now the ichthyofauna is made up of limnophilous fish species (Dgebuadze & Slyn’ko 2005). Before Sheksna was regulated, commercial catches were about 5 tons, dominating species was pike. At present, the annual catch equals 100 tons and the dominating species is bream.

2.9.3.6 Management and Conservation Anthropogenic stressors in the Sheksna are few. There are a number of diffuse pollution sources along the banks, diffuse runoff, and navigation effects. Water quality is estimated as ‘pure’ according to microbiological tests, and the water is mesotrophic according to chlorophyll and b- or a–b mesosaprobic. Poor water quality is apparent only at local sites. The Sheksna is monitored by a regional ecological service net, and the water chemistry has not changed in the last 40 years.

REFERENCES Adamenko, V.N., and Malinina, T.I. (eds). 1981. Anthropogenic Influence on Large Lakes of the USSR Pt. 1: Nauka, Leningrad, (In Russian). Agapitova, N.E. (ed). 1975. Resources of the Surface Waters in the USSR. The Basic Hydrological Characteristics. Vol. 11, Pt 1. Hydrometeoizdat, Leningrad (In Russian). Alekin, O.A. 1948. Hydrochemistry of the Rivers in the USSR. Leningrad (In Russian). Antonov, P.I. 1993. About invasion of the bivalve mollusk Dreissena bugensis (Andr.) into the River Volga reservoirs. Ecological Problems of the Basins of the Large Rivers. Togliatti (In Russian). Avakyan, A.B. 1998. Volga in the Past, Present, and Future. Express-3M, Mocscow (In Russian). Avakyan, A.B., Saltankin, V.P., and Sharapov, V.A. 1987. Reservoirs Mysl’, Moscow (In Russian). Bakanov, A.I. 1988. The benthos of the channel parts of the Volga reservoirs. Biology of Inland Waters. Information Bulletin 79, (In Russian). Bakanov, A.I. 1993. About appearance of the leech Archaeobdella esmonti (Arhynchobdellea, Herpobdellidae) in the River Volga reservoirs. Zoological Journal 72, (In Russian).

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Bakanov, A.I. 2002. Taxonomic composition and abundance of benthos in the Sheksna Reservoir in the late 20th century. Biology of Inland Waters 1, (In Russian). Bakanov, A.I. 2003. The contemporary state of the benthos in the Upper Volga within the Yaroslavl Region. Biology of Inland Waters 1, (In Russian). Bakanov, A.I. 2005. Benthos in the Cheboksary reservoir: taxonomic composition and abundance. Biology of Inland Waters 1, (In Russian). Balkov, V.A. 1978. Water Resources of Bashkiria. Bashkiria Book Publisher, Ufa, (In Russian). Balkov, V.A. 1979. Influence of Karst on the Rivers Run-Off in European Territory of the USSR. Hydrometeoizdat, Leningrad, (In Russian). Belevsky, P.E. (ed). 1892. Volga. Encyclopedic Dictionary 7 Brokgause & Efron, SPb, (In Russian). Belko, N. 2004. Reserved Meshera. Logata, Moscow, (In Russian). Behning, A.L. 1928. Data on the hydrofauna of the River Kama. Proceedings of the Volga Biological Station 94–5, (In Russian). Berg, L.S. 1948. Freshwater Fishes of USSR and Adjacent Countries Vol. 1, AS USSR, Moscow-Leningrad, (In Russian). Berg, L.S. 1949a. Freshwater Fishes of USSR and Adjacent Countries Vol. 2, AS USSR, Moscow-Leningrad, (In Russian). Berg, L.S. 1949b. Freshwater Fishes of USSR and Adjacent Countries Vol. 3, AS USSR, Moscow-Leningrad, (In Russian). BioDat: Informational Resources (http://www.biodat.ru/). Borodich, N.D., and Lyakhov, S.M. 1983. Zoobenthos. Kuibyshev Reservoir. Nauka, Leningrad, (In Russian). Butorin, N.V., and Ekzertsev, V.A. (eds). 1978. Ivankovo Reservoir and its Life, Nauka, Leningrad, (In Russian). Butorin, N.V., and Mordukhai-Boltovskoy, P.D. (eds). 1979. The River Volga and its Life, Junk Publishers, The Hague. Bylinkina, A.A., Trifonova, N.A., Kudryavtseva, N.A., and Kalinina, L.A. 1982a. Select data on hydrochemistry of the Kama reservoirs. Hydrobiological Characteristics of the Volga Basin Reservoirs, Nauka, Leningrad, (In Russian). Bylinkina, A.A., Trifonova, N.A., Kudriavtseva, N.A., Kalinina, L.A., and Genkal, L.F. 1982b. Hydrochemical regime of Sheksna Reservoir and waterbodies of Northern-Dvina system. Ecological Study of Waterbodies of Volga-Baltic and Northern-Dvina Water Systems, Nauka, Leningrad, (In Russian). Chernyaev, A.M. (ed). 2000. Waters of the Russia, Aqua-Press, Ekaterinburg, (In Russian). Daletchina, I.N., and Silnikova, G.V. 2001. Characteristic of phytoplankton in the Volgograd Reservoir during 1999–2000. Fundamental and Applied Aspects of Water Ecosystems Functioning: Problems and Future Trends of Hydrobiology and Ichthyology in XX Century. Saratov State University, Saratov, (In Russian). Dementieva, A.A. 1985. Zooplankton in the Votkinsk reservoir. Biology of Waterbodies in the Western Urals, Permsky State University, Perm’, (In Russian). Devyatkova, T.P., and Trutnev, A.Y. 1983. Peculiarities of forming flow velocity and water discharge in Kamskoye reservoir. Integrated Investigations of Rivers and Reservoirs in the Urals, Permsky State University, Perm, (In Russian). Dgebuadze, Y.Y., and Slyn’ko, Y.V. (eds). 2005. Alien Species in Holarctic (Borok-2). Book of Abstracts. 2nd International Symposium Rybinsk – Borok, (In Russian). Genkal, S.I., Koroleva, N.L., Poptchenko, I.I., and Burkova, T.N. 1992. The first finding of Actinocyclus variabilis in the Volga River. Biology of Inland Waters. Information Bulletin 94, (In Russian). Genkal, S.I., and Yelizarova, V.A. 1996. Actinocyclus variabilis (Makar.) Makar., a new representative of Bacillariophyta in the Rybinsk Reservoir. Biology of Inland Waters 1, (In Russian).

PART | I Rivers of Europe

Gerasimova, N.A. 1996. Phytoplankton in Saratov and Volgograd reservoirs. Samara Science Centre, Togliatti, (In Russian). Gromov, V.V. 1951. Changes of bottom fauna in the Kama River under influence of waste waters. Izvestia of YeNI 13, (In Russian). Gusakov, V.A. 2001. The Effect of the Hydrological Regime in the Rybinsk Reservoir on the Distribution and Dynamics of Benthic Cyclops. Water Resources 28. Isachenko, T.I., and Lavrenko, Y.M. 1980. Botanial and geographical zoning. Vegetation in the European part of the USSR, Nauka, Leningrad, (In Russian). Ivanov, D.I., and Pechnikov, A.S. 2004. Contemporary State of Fisheries in Russian Inland Water Bodies. GosNIORKh, St. Petersburg, (In Russian). Klige, R.K., Kovalevsky, V.S., and Fedorchenko, E.A. 2000. Influence of the global climatic changes on the water resources of the Volga basin. Global Changes of the Environment, Scientific World, Moscow, (In Russian). Komarov, I.K. 1997. Revival of the Volga – a Step to Salvation of Russia. Ecology, Moscow, (In Russian). Komlev, A.M., and Cernykch, E.A. 1984. Rivers of the Perm’ Oblast. Permsky Book Publisher, Perm’, (In Russian). Kopylov, A.I. (ed). 2001. Ecological Problems of the Upper Volga, YSTU Press, Yaroslavl, (In Russian). Kortunova, T.A. 1983. Zooplankton and its production in the Kamskoe reservoir. Integrated Investigations of Rivers and Reservoirs in the Ural, Permsky State University, Perm’, (In Russian). Kortunova, T.A. 1985. Variations in zooplankton in the Kamskoe reservoir during vegetation season. Biology of Waterbodies in the Western Ural, Permsky State University, Perm, (In Russian). Kuzin, P.S. 1960. Classification of the Rivers and Hydrological Regions of the USSR. Hydrometeoizdat, Leningrad, (In Russian). Kuzmin, G.V., and Okhapkin, A.G. 1975. Phytoplankton of the River Volga at the route of building the Cheboksary Reservoir and prognosis of its algological regime. Anthropogenic Factors in the Life of Waterbody, Nauka, Leningrad, (In Russian). Kuznetsova, L.A., and Rassadnikova, G.I. 1983. Physical and mechanical characteristics of the bottom sediments in the Votkinsk reservoir. Integrated Investigations of Rivers and Reservoirs in the Urals, Permsky State University, Perm’, (In Russian). Labunskaya, E.N. 1995. The Phytoplankton of Lower Volga and Northern Caspian, its Significance in Estimation Water Quality. Dissertation. Moscow State University, Moscow, (In Russian). Lipatova, V.V. 1980. Vegetation in floodplains. Vegetation in the European part of the USSR, Nauka, Leningrad, (In Russian). Litvinov, A.S. (ed). 2002. Modern State of the Sheksna Reservoir Ecosystem, YSTU Press, Yaroslavl, (In Russian). Lukyanenko, V.I., Riv’er, I.K., Litvinov, A.S., and Kopylov, A.I. 1994. Ecology of the Upper Volga: Modern State, Problems and their Solution. Yaroslavl, (In Russian). Lyashenko, O.A. 1999. Phytoplankton and chlorophyll content as index of trophic status of Ivankovo Reservoir. Water Resources 26(1). Lyashenko, O.A. 2000. Seasonal dynamics and long-term changes of phytoplankton and chlorophyll content in the Uglich Reservoir. Biology of Inland Waters 3, (In Russian). Malinina, Yu.A., Dalechina, I.N., and Filinova, E.I. 2005. Hydrobiological estimation of the water quality in the Volgograd reservoir in a zone of influence of industrial center. Actual Problems of Efficient Use of Biological Resources of Reservoirs, Publisher House, Rybinsk, (In Russian). Mineeva, N.M. (ed). 2000. Modern Ecological Situation in the Rybinsk and Gorky Reservoirs: the State of Biological Communities and Perspectives of Fish Reproduction, YSTU Press, Yaroslavl, (In Russian).

Chapter | 2 Volga River Basin

Mineeva, N.M. 2004. Plant pigments in the water of the Volga river reservoirs. Nauka, Moscow, (In Russian). Mokeeva, N.P. 1964. Algae flora of the River Oka. Proceedings of Zoological Institute AS USSR 32, (In Russian). Mordukhai-Boltovskoy, P.D., and Dzuban, N.A. 1976. Variations in composition and distribution of the River Volga fauna under anthropogenic impact. Biological Production Processes in the River Volga Basin, Nauka, Leningrad, (In Russian). Nechvalenko, S.P. 1976. Bottom fauna in the Volgograd Reservoir. The Volgograd Reservoir, Privolzhckoye, Saratov, (In Russian). Obidientova, G.V. 1975. Forming of the River Systems in the Russian Plain. Moscow, (In Russian). Okhapkin, A.G. 1994. Phytoplankton in Cheboksary Reservoir. Samara Science Centre, Togliatti, (In Russian). Okhapkin, A.G., Mikulchik, I.A., Korneva, L.G., and Mineeva, N.M. 1994. Phytoplankton in Gorki Reservoir. Samara Science Centre, Togliatti, (In Russian). Pakhtusova, N.A. 1969. Geological structure. Hydrogeology of the USSR. V. 44. Arkhangelsk and Vologda oblast, Nedra, Moscow, (In Russian). Pautova, V.N., and Nomokonova, V.I. 2001. The Dynamics of Phytoplankton in the Lower Volga River – From the River to Reservoirs Cascade. Samara Science Centre, Togliatti, (In Russian). Pavlinova, R.M. 1930. Biological study of the River Volga within the site from Gorodets to Sobchinsky zaton in 1926 and 1927. Proceedings of the Institute of Constructions of the Central Committee of Water Protection 11, (In Russian). Pavlov, D.S., Dgebuadze, Y.Y., Korneva, L.G., and Slyn’ko, Y.V. (eds). 2003. Invasions of alien species in Holarctic. Proceedings of the US – Russian Workshop, 27–31 August 2001, Borok, (In Russian). Pirogov, V.V., Fil’chakov, V.A., Zinchenko, T.D.,Karpyuk, M.I., and Edsky, L.B. 1990. New elements in the composition of benthic fauna in the Volga-Kama reservoir cascade. Zoological Journal 69 (9), (In Russian). Pivovarova, Z.I., and Stadnik, V.V. 1988. Climatic Parameters of the Solar Radiation as Source of Energy at the USSR Territory. Hydrometeoizdat, Leningrad, (In Russian). Poptchenko, I.I. 2001. Species Composition and Dynamics of Phytoplankton in Saratov Reservoir. Samara Science Centre, Togliatti, (in Russian). Reserves (http://www.water.zapovednik.com/). Reserves of Russia (http://www.sevin.ru/natreserves). Reshetnikov, Y.S. 1998. Annotated Catalog of Cyclostomes and Fishes of the Continental part of Russia. Nauka, Moscow, (In Russian). Savinov, Y.A., and Filenko, R.A. 1965. Hydrogeological regions of the Vologda oblast. North-West of the European USSR. Pt 4 Leningrad, (In Russian). Shilova, A.I., and Zelentsov, N.I. 2003. Fauna of Chironomidae (Diptera, Chironomidae) in the Upper Volga basin. Biology of Inland Waters 2, (In Russian). Shklyaev, A.S. 1964. Patterns in Distribution of Precipitations and Drainage at the Northern and Southern Ural. Permsky State University, Perm’, (In Russian). Shmidt, O.Y. (ed). 1928a. The Volga. Grand Soviet Encyclopedia. Vol. 12. Soviet Encyclopedia, Moscow, (In Russian). Shmidt, O.Y. (ed). 1928b. The Kama. Grand Soviet Encyclopedia Vol. 30 Soviet Encyclopedia, Moscow, (In Russian). Shtina, E.A. 1968. Basic features of phytoplankton in the River Kama. Volga-1. Book of Abstracts. Togliatti, (In Russian). Shurganova, G.V. 1987. Dynamics of Species Structure of Zooplankton Community Under its Formation (by example of Cheboksary

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reservoir). Dissertation thesis, Moscow State University, Moscow, (In Russian). Shurganova, G.V., Cherepennikov, V.V., Krylov, A.V., and Artel’ny, E.V. 2005. Spatial distribution and peculiarities of basic zooplankton cenoses in Gorky reservoir. Biological Resources of Freshwaters: Invertebrates, Rybinsk Publisher House, Rybinsk, (In Russian). Sokolov, V.Y. (ed). 1988. Flora and Fauna in Reserves of the USSR, Nauka, Moscow, (In Russian). Sokolov, V.Y. and Syroechkovsky, Y.Y. (eds). 1988. Reserves of the European part of RSFSR Vol. 1. Mysl’, Moscow, (In Russian). Sokolov, V.Y. and Syroechkovsky, Y.Y. (eds). 1989. Reserves of the European part of RSFSR Vol. 2. Mysl’, Moscow, (In Russian). Stolbunova, V.N. 1999. Long-term variation in zooplankton communities in Ivankovo and Uglich reservoirs. Biology of Inland Waters 1, (In Russian). Svetlov, P.G., 1936. Oligochaeta found during the Kama expedition in 1935. Izvestia of Biological NII of Perm’ State University. 10, (In Russian). Tauson, A.O. 1947. Water Resources of Molotovskaya oblast. Molotov, (In Russian). Timokhina, A.F. 2000. Zooplankton as a Component of the Ecosystem of Kuibyshev Reservoir. Samara Science Centre, Togliatti, (In Russian). Tretyakova, S.A. 1989. Phytoplankton of the Kama reservoirs (Kamskoe and Votkinskoe). Hydrobiological Characteristics of Waterbodies in the Urals, Sverdlovsk, (In Russian). Trifonova, I.S. (ed). 2003. Lower Volga Phytoplankton. Reservoirs and Lower Reaches of the River, Nauka Press, St. Petersburg, (In Russian). Vikulina, Z.A. and Znamensky, V.A. (eds). 1975. Hydrometeorological Regime of Lakes and Reservoirs in the USSR. Reservoirs of the Upper Volga, Hydrometeoizdat, Leningrad, (In Russian). Vodeneeva, E.L. 2000. The state of the phytoplankton community in the estuarine zone of the River Oka in 1997–1998. Proceedings of the Biological Department of the N.I. Lobachevsky Nizhegorodsky State University Vol. 3. Nizhni Novgorod, (In Russian). Voloshko, L.N. 1971. Species composition of phytoplankton in the Lower Volga River and its Delta. Botanical Journal 56, (In Russian). Wikipedia – Open Encyclopedia (http://ru.wikipedia.org/). Yablokova, Y.Y. (ed). 1973. Resources of the surface waters in the USSR. The Upper Volga region Vol. 10, Pt 1. Hydrometeoizdat, Moscow, (In Russian). Yakovlev, V.N. (ed). 2000. Catalog of Plants and Animals of Volga River Basin Waterbodies, YSTU, Yaroslavl, (In Russian). Yesyreva, V.I. 1945. Algae flora of the River Volga from Rybinsk to Gorky. Proceedings of the Moscow State University Botanic Garden. 5 (82), (In Russian). Yesyreva, V.I. 1968. Phytoplankton of the River Oka. Abs. 1st Conf. on the Study of Water Bodies in the Volga Basin ‘Volga-1’,Togliatti, (In Russian). Yoffe, T.I. 1968. Review on realization of acclimation of the invertebrates for fish in reservoirs. Izvestiya GosNIORKh. 67, (In Russian). Zakonnov, V.V. 2005. Origin and transformation of bottom sediments in the Volga river reservoirs. Nature and Resources, Ecological, Social and Economic Problems of Environment in Large River Basins, MediaPress, Moscow, (In Russian). Zenin, A.A. 1965. Hydrochemistry of the River Volga and its reservoirs. Leningrad, (In Russian). Zinchenko, T.D. 2002. Chironomids of surface waters in the Middle and Lower Volga basins (Samara district). Ecological and Faunistic Review. Togliatti, (In Russian). Znamensky, V.A. and Chigirinsky, P.P. (eds). 1978. Hydrometeorological regime of the lakes and reservoirs in the USSR. Kuibyshev and Saratov Reservoirs Hydrometeoizdat Leningrad, (In Russian).

Chapter 3

The Danube River Basin Nike Sommerwerk

Christian Baumgartner

J€ urg Bloesch

Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), M€ uggelseedamm 310, 12587 Berlin, Germany

Donauauen National Park GmbH, 2304 Orth an der Donau, Schloss Orth, Austria

International Association for Danube Research (IAD), Stauffacherstrasse 159, 8004 Z€ urich, Switzerland Eawag, Swiss Federal Institute of Aquatic € Science and Technology, Uberlandstrasse 133, 8600 D€ ubendorf, Switzerland

Thomas Hein

Ana Ostojic

Momir Paunovic

University of Natural Resources and Applied Life Sciences, Vienna, Institute of Hydrobiology and Aquatic Ecosystem Management, Max – Emanuelstrasse 17, 1180 Vienna, Austria WasserCluster Lunz, Dr. Carl-KupelwieserProm. 5, 3293 Lunz/See, Austria

University of Zagreb, Faculty of Science, Division of Biology, Rooseveltov trg 6, 10000 Zagreb, Croatia

Institute for Biological Research, 142 Despota Stefana Boulevard, 11060 Belgrade, Serbia

Martin Schneider-Jacoby

Rosi Siber

Klement Tockner

EuroNatur – European Nature Heritage Fund, Konstanzer Str. 22, 78315 Radolfzell, Germany

Eawag, Swiss Federal Institute of Aquatic € Science and Technology, Uberlandstrasse 133, 8600 D€ ubendorf, Switzerland

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3.1. 3.2. 3.3. 3.4. 3.5. 3.6.

3.7.

Introduction Historical Aspects Palaeogeography and Geology Geomorphology Climate and Hydrology Biogeochemistry, Water Quality and Nutrients 3.6.1. General Characteristics 3.6.2. Water Quality Biodiversity 3.7.1. Riparian Vegetation 3.7.2. Vegetated Islands 3.7.3. Macrophytes 3.7.4. Macroinvertebrates 3.7.5. Fish 3.7.6. Avifauna 3.7.7. Wetland Mammals 3.7.8. Herpetofauna

Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

3.8. 3.9.

3.10.

Human Impacts, Conservation and Management Major Tributaries and the Danube delta 3.9.1. Inn 3.9.2. Morava 3.9.3. V ah 3.9.4. Drava 3.9.5. Tisza 3.9.6. Sava 3.9.7. Velika Morava 3.9.8. Olt 3.9.9. Siret 3.9.10. Prut 3.9.11. Danube delta Conclusion Acknowledgements References

59

60

FIGURE 3.1 Digital elevation model (upper panel) and drainage network (lower panel) of the Danube River Basin.

PART | I Rivers of Europe

61

Chapter | 3 The Danube River Basin

3.1. INTRODUCTION

3.2. HISTORICAL ASPECTS

It was July 10 in 1648 when Pope Innocent X approved the construction of the ‘Four-Rivers-Fountain’ at the Piazza Navona, probably the most beautiful square in Rome. He asked the famous sculptor Gian Lorenzo Bernini to finish the fountain by 1650, a Holy Year. The four rivers were the Nile of Africa, the Ganges of Asia, the Rio del la Plata of the Americas and the Danube of Europe (Weithmann 2000). The Danube is the European river par excellence; a river that most effectively defines and integrates Europe. It links more countries than any other river in the world. The Danube River Basin (DRB) collects waters from the territories of 19 nations and it forms the international boundaries for eight of these (Figure 3.1). The river’s largely eastward course has served as a corridor for both migration and trade, and a boundary strongly guarded for thousands of years. The river’s name changes from west to east from Donau, Dunaj, Duna, Dunav, Duna˘rea, to Dunay, respectively. The names of the river (Danube, as well as Don, Dnjeper and Dnjester) most likely originate from the Persian or Celtic word Danu, which literally means flowing. It also may stem from the Celtic ‘Don, Na,’ or ‘two rivers,’ because the Celts could not agree on the source of the Danube (cited in Wohl in press). In this chapter, we provide an overview of the DRB, including the three main sections (Upper, Middle, Lower Danube), the delta and 11 major tributaries (Figures 3.1 and 3.2, Table 3.1). This chapter builds upon several textbooks on the Danube, including Liepolt (1967) and Kinzelbach (1994) and, among many other sources, on information derived from the International Commission for the Protection of the Danube River (ICPDR).

In 1908, an 11.1-cm large statuette, the so-called ‘Venus of Willendorf’, was excavated by the archaeologist Szombathy near the village of Aggsbach (Austria, Wachau valley), dating back 25 000 years BC. North of this place, in Dolvi Vestonica, a large meeting place of mammoth hunters from the same period was discovered 1924–1952. These two examples demonstrate that the Danube valley has experienced a long history of human occupation and cultural development that started during the Paleolithic period. Between 8500 and 500 BC, permanent fishery and hunting settlements were erected in Lepinski Vir (Iron Gate Gorge) and Vinca (in the suburban sector of Belgrade) (Weithmann 2000). Starting >7000 years ago, farmers from Anatolia entered Europe and expanded throughout the continent. The Danube was most likely one of the major expansion pathways. There is evidence that a major flood that entered the Black Sea from the Mediterranean (i.e., the diluviam) probably forced the westward migration of these early farmers. Between 750 and 500 BC, the Celts occupied the entire Upper Danube valley. The best known place was the Heuneburg near Riedlingen where a large Celtic wall circled the entire hill. The Celts respected the Danube as a bringer of life and death and their sole connection to the outside world. They called it the Great Mother of Gods – Danu. The Celts were stimulated by Greek culture. The Greek poet Hesiod first mentioned the Danube in about 700 BC as the ‘beautifully flowing Istros’, the son of Tethys and Okeanos. Herodotus wrote in 450 BC that the (H)Istros is the largest river in the world, a river that ‘has its source in the country of the Celts near the city Pyrene, and runs through the middle of Europe, dividing it into two portions . . . before it empties itself into the Pontos Euxeinos’. During the war against the Scythes in 513/12 BC, Dareis, the great Persian king, sailed up the Danube to explore a suitable location for constructing a bridge for his army. The first European waterway was established during the Greek period and connected the Adriatic Sea with the Black Sea via the Ocra pass, the Sava River and the Lower Danube. Today, there exist plans to re-establish this ancient Danube–Adriatic waterway for navigation. The Danube was always both a migration corridor as well as a frontier. During the Roman Empire, the ‘Limes’ along the Danube as well as along the Olt River protected the Empire agains the ‘Barbarians’. The Romans erected fortifications along the Danube such as Castra Regina (Regensburg), Juvavum (Salzburg), Lentia (Linz), Vindobona/ Vindomana (Vienna) and Aquincum (Budapest), among many others. The Limes played an important role even long after the fall of the Roman Empire, for example, it was used as a fortification against the Mongolian invasion in 1241. The armies of Charlemagne also marched along the remnants of the Roman Limes, as did the Crusaders. The boundary between Orient and Occident is roughly just east of the

FIGURE 3.2 Longitudinal profile of the Danube River and its major

62

TABLE 3.1 General characterization of the Danube River Basin Upper Danube

Middle Lower Delta Inn Danube Danube Danube

Mean catchment 793 435 355 9 elevation (m) 104 932 473 214 218 387 4560 Catchment area (km2) 25.3 125.9 188 205 Mean annual discharge (km3) Mean annual 101.2 79.2 60.5 43.2 precipitation (cm) 6.7 8.8 9.2 10.7 Mean air temperature ( C) Number of ecological 4 8 7 1 regions Dominant (25%) 2; 70 52 9 55 ecological region(s) Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparse vegetation Wetland Freshwaterbodies Protected area (% of catchment)

1260

378

V ah

Drava

473

760

Tisza

Sava

350

Velika Morava

541

631

Iskar 655

Olt

Siret

621

Prut

485

267

26 128 27 267 19 660 40 087 156 087 95 793 37 571 8860 24 439 46 289 28 568 23.1 3.47 4.35 17.1 25.0 49.6 8.74 1.70 5.43 6.63 2.11 136.0

63.8 79.3

112.1

65.8

105.4

77.8

62.1

67.6

62.4

59.8

8.6 2

9.2 4

9.3 3

9.4 2

7.9 4

7.7 5

8.5 4

9; 58

9; 13

13; 22

13; 22; 28

4.6 2

8.1 7.5 4 2

7.3 3

2; 70

52; 70 13; 52

2; 52

52

27; 52

9

4.7 31.5 13.4 37.3 6.4 5.5 0.3 0.9

4.1 44.8 7.8 35.4 5.9 0.6 0.5 0.9

6.0 54.1 6.7 26.6 4.1 0.3 0.7 1.5

2.4 22.9 1.1 5.8 4.6 1.4 49.0 12.8

2.9 14.7 15.4 35.2 13.5 17.0 0.3 1.0

6.0 6.4 59.4 45.6 3.0 6.4 29.3 36.8 1.8 3.8 0.0 0.2 0.0 0.2 0.5 0.6

3.5 28.7 7.9 45.8 9.0 3.9 0.3 0.9

4.9 48.1 11.1 30.0 4.4 0.1 0.7 0.7

2.1 36.9 5.8 45.3 8.4 0.7 0.1 0.7

1.7 38.8 7.3 42.6 8.8 0.5 0.0 0.3

6.3 42.2 4.3 30.3 14.6 1.6 0.1 0.6

5.0 36.5 12.6 37.4 6.7 0.4 0.4 1.0

7.7 38.8 9.4 38.2 3.9 0.2 0.5 1.3

4.9 57.3 7.3 27.7 0.6 0.0 1.2 1.0

0.5

2.8

0.7

89.1

0.9

7.7 11.2

0.3

3.0

0.8

0.0

0.0

0.0

0.3

3.3

2.0 2.9 3 217

2.0 3.0 3 143

2.0 3.0 2 227

2.2 3.0 1 0

2.0 2.9 3 31

2.0 3.0 3 17

2.0 3.0 3 49

2.0 3.0 2 45

2.0 2.9 2 18

2.0 2.9 2 3

2.1 3.0 2 2

2.0 3.0 3 27

2.0 3.0 3 18

2.0 3.0 2 3

49 14 3 91

56 12 13 85

50 5 5 92

35 7 1 116

37 3 1 170

17 6 2 87

29 5 3 75

41 5 3 112

15 832

2876

3664

702

2763

2212

1703

943

2.0 3.0 3 46

59 13 7 140

72 12 23 95

70 7 18 101

70 4 0 34

15 2 2 84

45 7 2 129

37 n.d. 0 133

27 726

4886

1746

2145

31 317

8771

4342

Catchment boundaries: see Figure 3.1a. The Iskar River is not treated in detail in the text. n.d.: Not determined. For data sources and detailed explanation see Chapter 1.

PART | I Rivers of Europe

Water stress (1–3) 1995 2070 Fragmentation (1–3) Number of large dams (>15 m) Native fish species Nonnative fish species Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person)

Morava

Chapter | 3 The Danube River Basin

Iron Gate and south of Belgrade. The division into two parts has remained for most of its history, making the Danube ‘aqua contradictionalis’, the river of fatality as mentioned by Pope Innocent IV. The Roman Empire influenced the Danube region for >500 years, starting with the expansion of the empire toward the Danube during the regency of Octavianus Augustus. The Upper Danube, down to the Iron Gate, then changed its name from (H)Ister (Istros) to Danuvius (Danubis). The Romans established several provinces along the Danube, including Raetia, Pannonia, Dacia, Moesia and Scythia. Dacia was the only province north of the Danube, but it was given up by Emperor Aurelian in 270 AD. The retreat of the Romans from Dacia created a power-vacuum and contributed to a global political and military crisis at that time. In the context of the Roman Empire, the Danubian provinces were primarily of military interest and the people in Rome and the Mediterranean area considered these provinces as culturally undeveloped. The battle at Adrianopel (Edirne), 378 AD, marked the beginning of the end of the Roman Empire. An unstable period followed after the fall of the Empire and the subsequent invasion by the Barbarians. German tribes and later Turkic Avars (‘Huns’ is often used synonymously for Avars) entered the area and crossed the Danube; in particular during winter when the Middle and Lower Danube were frozen. The Goths left Pannonia at the end of 469 and crossed the frozen Danube north of Aquincum (Budapest). The Langobards replaced the Goths in Pannonia, remaining for >100 years. Moesia was the only Romanian province along the Danube that remained for longer periods under the control of Constantinople, the capital of the Eastern Roman Empire. The Avars, a steppic tribe that forced the Langobards to leave the area (the Langobards settled in northeast Italy), established their Khangat in the Danube–Tisza area. For short periods, they expanded their area to near Constantinople. In the 7th century, Slavs (Croatians and Serbians) originating from north of the Carpathian Mountains and nomades (Bulgarians) from the Volga area entered the Danube region and replaced the Avars in the Sava–Drava and Lower Danube, respectively. Later, the Avars disappeared from the Pannonian plain, and in 895 AD the Magyars, originating from the northeast Ural Mountains and western Sibiria, arrived in the Pannonian plain and established their regency. The Upper Danube was mainly under the control of the Bavarians. Up to 1050 AD, the Danube was primarily a migration corridor for warriers. During the 11th century, the river became an important route for pilgrims visiting the Holy Country and Jerusalem. However, the Crussards could not stop the loss of the Holy Country to the Ottoman Empire. The Ottoman Empire influenced the Danube region for 500 years. The ‘foreign’ rule by the Turks has often been blamed for the present state of under-development in the Middle and Lower Danube. Bulgaria was the first country under Ottoman control (1393–1878). In 1389, Serbia lost at the memorable battle of Kosovo polje against the Ottomans. Soon after,

63

the entire Danube downstream of Iron Gate became under Ottoman control. During the Ottoman Empire, the Danube was again a ‘Limes’ but this time to protect the northern parts against the threats entering from the south. Hungarians (King Sigismund), together with French, Burgundian and German armies, tried to re-occupy these areas but were defeated by Sultan Bayezid at Nikopolis in 1396 AD. This battle stabilized the Ottoman occupation in the area for the coming centuries, until the Balkan wars at the beginning of the 20th century. At the end of the 13th century, the Habsburg dynasty appeared for the first time in the Upper Danube valley after they had lost their stronghold in 1291 AD to the Swiss Federation. Until the 15th century, the Habsburg influence was restricted roughly to the area of present Austria. After the successful battle against the Ottomans in 1683 at Vienna, the Austrians, together with their allies, expanded their territories, re-occupied Budapest, freed Hungary and for a short period also Belgrade. The fight for the ‘golden apple’ Vienna was a historic benchmark event for all of Europe. Kara Mustafa moved 200 000 men, the largest army Europe ever saw, along the Danube, devastating whole areas. During these battles, galleys constructed by the Dutch were successfully used on the Danube. In 1867, the Austrio-Hungarian Monarchy was formed, which was known as the ‘DanubeMonarchy’ until the great political reconfiguration in 1918. Along the Lower Danube and delta, the Russians established their influence at the beginning of the 19th century. After World War II, the Iron Curtain again divided the Danube basin and increased the difference between the two parts. The Danube has served as a major waterway since the Greek period. In Vienna, the Romans already erected a pontoon bridge during the war against the Markomans. And at Drobeta Turnu–Severin (Serbian/Romanian border), the Emperor Trajan erected in 105 AD a 1000-m wide wooden bridge across the Danube (the famous Trajan bridge). The Tabula Trajana, a monument of the Roman frontier, marks a section of the Roman road along the Danube. The tablet honours Trajan for the construction of the road and bridge over the Danube. Along the Pannonian section of the Danube, the Classis Pannonica, the warship fleet of the Romans operated. These boats were 35-m long and 5-m wide, provided space for 120 people and reached a speed of 10 km/hr (Weithmann 2000; Landesausstellung 1994). In 1828, the ‘Donau-Dampfschiffahrtsgesellschaft’ (DDSG) was founded. It soon became the world’s largest inland shipping company, with a total length of navigable rivers and canals of 4100 km, a fleet of 1000 ships and 12 000 staff members. Early attempts to connect the Danube with the Main and Rhine Rivers date back to Charlemagne in 793, who tried to build a 2-km long canal between Altm€uhl and the Swabian Rezat, yet failed to complete it. In the following centuries, this idea was brought up several times but was never fully realised. The Bavarian King Ludwig I opened in 1845 a continuous waterway – the ‘Ludwig–Main–Danube–Canal’ – which was in operation until World War II, but never gained

64

importance because of limited capacity and the concurrent development of the railway network. Construction of the 177-km long Rhine–Main–Danube Canal started in 1960 and was completed in 1992. Early attempts to coordinate the use of the Danube River led to the 1856 Treaty of Paris. Based on negotiations that started in 1848 (Congress of Vienna), the Budapest Commission was created to coordinate navigation. A convention on fisheries was signed among the lower Danube countries, but it took 2500 years after Herodotus and the fall of the Iron Curtain for Europeans to agree on the protection and sustainable use of the river. Based on the Danube River Protection Convention signed in 1994, the International Commission for the Protection of the Danube River (ICPDR) was founded.

3.3. PALAEOGEOGRAPHY AND GEOLOGY Comprehensive introductions to the palaeogeography and geology of the Danube River Basin are given in Liepolt (1967); Hantke (1993); Bl€ uhberger (1996); Neppel et al. (1999); Domokos et al. (2000); Belz et al. (2004) and Kovac et al. (2006). The largest part of the basin belongs to the alpidic or neo-European geological macro-region in Europe. Smaller parts belong to the western and eastern Variscan subregions and to the pre-Palaeozoic Russian platform. In the tertiary, the basin was part of the Paratethys, a branch of the Tethys, the proto-Mediterranean Sea. During this period, the Alps, the Carpathian Mountains, the Dinarides and the Balkan Mountains started to fold via plate tectonics. In the Miocene and Pliocene, the nuclei of these mountain chains formed islands in the shallow Paratethys. The rivers that exist today appeared for the first time in the Middle Miocene. They emerged as coastal rivers from the surrounding mainland and as streams on the Paratethys islands. It is worth noting that the basin boundary of the former Paratethys is almost identical to the present boundary of the Danube basin. Since that time, only local exchanges between neighbouring basins took place. During the Pliocene, a strong uplift of the mountains occurred. Subsequently, massive debris and sediment erosion, conditioned by a sub-tropical climate, gradually filled the shallow Paratethys. A progressive subsidence of subbasins, the Pannonian basin in particular, followed. At the end of the Pleistocene, the Paratethys became brackish, then freshened and finally formed a network of lakes, swamps and watercourses. This fluvio-lacustrine system disappeared when the residual lake Geta silted up completely in the first half of the Pleistocene. Periodic cooling during the Pleistocene led to partial and complete (in the Alps) glaciation of the mountains that continued to rise. As a consequence, physical weathering generated vast amounts of solid material that filled the Danube basins to their present level. In piedmont zones, the rivers formed megafans and bedload ramps and the channels

PART | I Rivers of Europe

permanently shifted their course. In glaciation-free mountains, the rivers followed incised valleys. Geologically, the Upper Danube is much older than the Rhine. In the Pleistocene, the Rhine started at the southwestern tip of the Black Forest, while waters from the Alps that today feed the Rhine were carried east by the so-called Urdonau (original Danube). Parts of this ancient riverbed, which was much larger than the present Danube at this location, can still be found as submerged canyons in the Swabian Alb. After the Upper Rhine valley had descended, rivers draining the northern slopes of the Alps changed their direction towards the Rhine. Because the Swabian Alb consists of porous limestone and the valley bottom of the Rhine is much lower than the Upper Danube, water from the Danube still continues to feed the Rhine via subsurface pathways (the so-called ‘Donauversickerung’ or ‘loss of Danube’ near Immendingen). Most of this water resurfaces at Aachtopf, Germany’s most yielding spring with an average production of 8000 L/s, north of Lake Constance. In the Middle Danube, following the aggradation of the Vienna Basin, the river first followed the eastern margin of the Alps southwards, turned at the southern border of the Pannonian Basin eastwards, and finally reached the Iron Gate. At Visegrad Gate, it formed an immense alluvial fan that gradually filled the depression of the Great Hungarian Plain. In the Lower Danube, the river course is more stable. Due to climate-induced low flow, tributaries exiting the mountains immediately deposited coarse bedload material and only small amounts of sediments, mainly as suspended material, reached the Danube valley. The Danube River valley, structured by several terraces, stretched along the southern margin of the Romanian Lowland. During the past 15 000 years, the Romanian section of the Danube valley has been mainly shaped by tectonic activities. Between Bazias and Drobeta Turnu Severin, the Danube flows for 130 km through a deep valley that links the Pannonian depression with the Dacic Basin (‘Iron Gate’). The ongoing uplift of the Carpathian Mountains during the Pleistocene and Holocene resulted in intense erosion of the valley, which is <200 m wide. The evolution of the Danube floodplain in Romania is also strongly influenced by aeolian processes, which resulted in the formation of dunes. The thickness of the aeolian sands decreases progressively eastwards (Ghenea & Mihailescu 1991). One of the most significant changes in flow direction was experienced by the River Olt, which originally had been a tributary to the River Mure¸s/Maros (a present tributary of the Tisza). It was captured by a smaller, yet direct Danube tributary that had cut deeply into the southern Carpathian Mountains, so that it was diverted towards the Danube. In this way, the Transylvanian Basin, that was originally uniform in hydrographic terms, became divided into the basins of the River Tisza/Tisa and Danube. The Danube first entered the sea south of the Dobrogea region, but due to a tectonic uplift of this area in the second half of the Pleistocene, it was forced to follow the northern margins of the Dobrogea. The water level of the Black Sea fluctuated by 70–80 m, shifting the

Chapter | 3 The Danube River Basin

river mouth forwards and backwards. The ancient Danube bed can still be traced on the Black Sea bottom. At the beginning of the Holocene, the development of the present river system was nearly complete. Only three changes are notable. First, karstification of the Swabian Alb continued, with the consequence that a high proportion of the Danube flow entered the Rhine basin via subsurface sinks. This process will continue in the future and will lead to a further loss of Danubian headwaters. Second, a tectonic uplift of the northeast part of the Great Hungarian Plain forced the Tisza River to change its course. Third, the Black Sea transgressed into the debouchure area of the Danube valley up to the foreland of the Carpathian Mountains. This transgression, however, was limited in time, so that the Danube was then able to fill the embayment and to develop its present delta. The main mountain ranges in the west of the basin (Black Forest, Bavarian Forest and Bohemian Forest) mostly consist of crystalline metamorphic rock. Crystalline bedrock also predominates in the central Alps, the central chain of the Carpathians and parts of the Stara Planina (Belz et al. 2004). Flysch sedimentary rocks extend from the German Prealps to the northern and eastern scarp of the Carpathian arc and to the northern part of the Stara Planina Mountains. In the Dinarids, Mesozoic limestone and dolomite covers the northern and southern limestone Alps. Near-surface quarternary sediments, mostly of alluvial origin, prevail along the river valleys. Sediments of aeolian origin (mainly loess and sand) dominate the non-alluvial zones of the basin.

3.4. GEOMORPHOLOGY The Danube begins at the confluence of the Breg and Brigach Rivers in the Black Forest near Donaueschingen

65

(Germany). It flows for a distance of 2826 km and enters the Black Sea east of Izmail (Ukraine) and Tulcea (Romania). The Danube is the second largest river in Europe and drains an area of 801 093 km2. Published information on the size of the basin varies depending on the source and whether the Black Sea coastal waters and river basins are included. The basin drains parts of 19 countries with a total human population of 83 million (census in 2002). Albania, Italy, Macedonia and Poland together contribute <0.1% to the area and <0.1% to the total human population within the basin (ICPDR 2005). The highest points are Piz Bernina (4052 m asl) on the western edge and Peak Krivan (2496 m asl) in the northern part of the basin. The average altitude of the basin is 458 m. The Danube River Basin can be divided into three general sections and the delta (recently the Danube has been divided into up to 10 smaller zoogeographic sections, Birk & Sommerh€auser 2003). The Upper Danube extends from its source to the confluence with the Morava River near Bratislava (socalled ‘Porta Hungarica’) (Photo 3.1), the Middle Danube extends from Bratislava to the Iron Gate dams (border between Romania-Serbia) (Photo 3.2) and the Lower Danube is formed by the Romanian-Bulgarian lowlands (Photo 3.3). Finally, the Danube delta, the 6th largest delta in Europe (see Table 1.2, Chapter 1). A characteristic feature along the entire river is the alternation between flat basins and deep gorges (see Figure 3.8). The former floodplain width, before regulation, reached >10 km in the Upper Danube and >30 km in the Lower Danube. Slope decreases from 0.4‰ in the upper valley to 0.004‰ in the final 250 km before it enters the Black Sea (Figure 3.2). The Upper Danube, after the confluence of the Brigach and Breg Rivers, follows the fault gap of the German Alb. Major tributaries in the south (Iller, Lech, Isar, Inn, Salzach, Traun and Enns Rivers) drain Alpine PHOTO 3.1 Upper Danube at Hainburg. (Photo: ICPDR/Mello).

66

PART | I Rivers of Europe

PHOTO 3.2 Middle Danube at Kazan gorge, Serbia/ Romania. Mraconia Monastery at the Romanian Bank of the Danube (Rkm 967). (Photo: Christian Baumgartner, Austria).

PHOTO 3.3 Lower Danube near Orjahovo, Bulgaria. (Photo: Christian Baumgartner, Austria).

sub-basins increasing the discharge in the Danube substantially (Figure 3.3). The Morava River is the most important tributary from the north. The Upper Danube has an Alpine character with low water temperature, high velocity and coarse bed sediments. Immediately downstream of the Porta Hungarica, the Danube forms a vast internal delta, and the slope decreases to 0.08–0.03‰. The Middle Danube is the largest of the three sections. It traverses the Pannonian plain and enters the 117 km long Iron Gate gorge where it flows through the Balkan and Carpathian mountains. The main left-bank tributaries are the Vah and Hron in Slovakia and the Tisza

that enters the Danube in Serbia. The main right-bank tributaries include the Leitha, Raab, Drava, Sava and Velika Morava Rivers. The Lower Danube is a typical lowland river fringed by (formerly) wide floodplains. In the 1960s, major floodplain sections (5500 km2, or 72% of former floodplains) were cut off from the river and transformed into agricultural land, poplar plantations, and fish ponds (Table 3.4). The Olt, Siret and Prut are the main tributaries entering from north, while only smaller tributaries, such as the Iskar, enter from the south. Despite the loss of floodplains (‘balta’ area), the Lower Danube represents an ecologically highly valuable

67

Chapter | 3 The Danube River Basin

FIGURE 3.3 Average annual discharge (m3/s) of the Danube River and its main tributaries. Note that major tributaries are from the right side (in flowing direction), especially in the upper part (alpine origin). The Tisza River is the main tributary from the left side. Redrawn after Liepolt (1967).

section, with numerous islands, natural banks and floodplain remnants (Schneider 2002). The Danube delta, including adjacent oxbow lakes and lagoons, covers some 5640 km2 (about 20% in the Ukraine, 80% in Romania). Major changes took place between 1960 and 1989, when 1000 km2 were poldered in the Romanian part for agriculture, forestry and fish culture. The fluvial backwaters in the Ukraine have been isolated from the river for aquaculture since the 1960s, whereas the frontal marine lagoons in the Romanian and Ukraine parts were isolated from the sea and used as a reservoir for irrigation purposes after the 1970s. The total length of channels in the Romanian delta increased from 1743 km to 3496 km (G^as¸tescu et al. 1983). Discharge from the river to the delta wetlands increased from 167 m3/s before 1900 to 309 m3/s during 1921–1950; 358 m3/s during 1971–1980 and 620 m3/s during 1980–1989 (Bondar 1994). Despite these engineering measures, over 3000 km2 of the wetlands, including the Razim–Sinoe lagoon and the adjacent Ukrainian secondary delta (250 km2), remain connected to the river and represent the largest nearly undisturbed wetland in Europe. About 50%

of the area is permanently aquatic; the rest is seasonally flooded. The Danube basin fully or partially covers nine ecoregions (Alps, Dinaric Western Balkan, Hellenic Western Balkan, Eastern Balkan, Central Highlands, The Carpathians, Hungarian Lowlands, Pontic Province and Eastern Plains). For the transitional and Black Sea coastal waters, Romania and Bulgaria have proposed to define a new ecoregion: The Black Sea ecoregion.

3.5. CLIMATE AND HYDROLOGY Due to its large size, its distinct west–east orientation, and its diverse relief, the basin exhibits a large climatic heterogeneity. The Upper Danube is influenced by an Atlantic climate with high precipitation and mild winters, whereas the eastern regions are under a continental influence with low precipitation and dry and cold winters. Parts of the Drava and Sava Rivers are influenced by a Mediterranean climate. The heterogeneity of the relief, especially the

68

PART | I Rivers of Europe

differences in the extent of exposure to predominantly westerly winds, as well as the differences in altitude, diversify this general climate pattern. This effect leads to distinct landscape regions that exhibit major differences in climatic conditions. Precipitation ranges from <500 to >2000 mm. Average annual precipitation peaks in the highest parts of the Alps (3200 mm) but is as low as 350 mm in the Black Sea and delta regions. Snowcover between November and February/March is expected at an elevation >1500 m asl (cited in Belz et al. 2004). Average peak precipitation occurs in July in the western part of the basin, in May/June in the southeastern parts, and in autumn in the areas influenced by the Mediterranean. The highest average annual temperature (+11 to +12 C) occurs in the Middle and Lower Danube and in the lower Sava valley. Seasonal differences increase from west to east. In the Hungarian plains, the seasonal change in temperature (min./max.) can be as high as 74 C. Spatial and seasonal differences in precipitation have strong effects on the surface run-off and discharge regime of the Danube and its main tributaries (ICPDR 2005). For example, Austria (22% of total flow) and Romania (18%) contribute most to the total flow of the Danube, reflecting the high pecipitation in the Alps and Carpathian mountains. The average annual specific discharge decreases from 25 to 35 L/s/km2 in the Alpine headwaters to 19 L/s/km2 for the Sava, 6.3 L/s/km2 for the Tisza and to 2.8 L/s/km2 for the rivers draining the eastern slopes of the Carpathians (Belz et al. 2004). At its mouth at Ceatal Izmail (upstream end of the Danube delta), the mean annual discharge is 6480 m3/s, corresponding to an annual flow of 203.7 km3 (range: 134 km3 in 1990; 297.1 km3 in 1941) (Table 3.2).

In the Lower Danube, the flow regime has been modified by the Iron Gate dams as well as by the large water management schemes along the Olt, Arge¸s, Siret and Prut Rivers. The suspended sediment load decreased from 40 million tons/year (maximum of 106 million tons in 1940) to a low of 7.3 million tons/year today. The basin has experienced many disastrous floods. The flood in February 1342, associated with a big ice drift, caused the reported death of 6000 people. The largest flood during the past millenium was the memorable flood in August 1501. Peak discharge at Vienna was 14 000 m3/s, and flood marks can still be seen along the entire Danube. Since 1821, the water level has continuously been recorded at selected stations. The flood in 1862 stimulated the regulation of the main Danube (1869 to 1876, see Photo 3.4a, b and c), and the largest flood in the last century occured in 1954 (peak discharge at Vienna was 9600 m3/s).

3.6. BIOGEOCHEMISTRY, WATER QUALITY AND NUTRIENTS 3.6.1. General Characteristics Physico-chemical and selected biological parameters are regularly monitored by the International Commission for the Protection of the Danube River (ICPDR). These data for the Danube and its main tributaries are mostly derived from the TransNational Monitoring Network (TNMN; monitoring period: 1996–2005). The biogeochemistry of the Upper Danube is mainly influenced by the Alps. The major tributaries Sava, Drava and Tisza dominate the chemistry of the Middle Danube, where alluvial deposits predominate,

TABLE 3.2 Flow regime (in m3/s) of the Danube River and its tributaries (time period: 1931–1990) River

Station

A (km2)

NQ

MNQ

MQ

MHQ

HQ

MHQ/MNQ

Danube Danube Danube Danube Danube Danube Inn Morava V ah Drava Tisza Sava Velika Morava Olt Siret Prut

Berg Regensburg Vienna Bezdan Orsova Ceatal Izmail Passau-Ingling Moravsky Jan Sala Donij Miholjac Senta Sremska Mitrovica Ljubicevski Most Stoenesti Lungoci Cernicvi

4047 35 399 101 731 210 250 576 232 807 000 26 084 24 129 10 620 37 142 141 715 87 996 37 320 22 683 36 036 6890

4.6 107 504 505 1060 1790 195 7.7 0.5 166 80 194 17 15 16 1.5

12.9 198 832 992 2246 2901 267 29 22 234 179 401 55 48 52 10

38.5 444 1920 2372 5611 6486 732 110 138 541 792 1572 277 172 210 67

209 1468 5547 4788 10 604 10 889 2936 584 861 1359 2142 4154 1290 908 1294 1200

445 2531 9600 7689 14 813 15 540 6359 1573 1497 2281 3730 6638 2355 2320 2825 2170

16.2 7.4 5.5 4.8 4.7 3.8 11.0 20.1 39.1 5.8 12.0 10.4 23.5 18.9 24.9 120

A: Catchment area upstream of gauging station. NQ: lowest measured discharge. MNQ: arithmetic mean of the lowest measured annual discharge. MQ: arithmetic mean annual discharge. MHQ: arithmetic mean annual flood discharge. HQ: highest measured discharge (data: Belz et al. 2004).

Chapter | 3 The Danube River Basin

69

PHOTO 3.4 The Danube River at Vienna in 1848, 1888 and 1989 (from Mohilla & Michlmayr 1996; with kind permission from Oesterreichischer Kunst und Kulturverlag, Vienna).

whereas the Iron Gate reservoirs influence the biogeochemistry and material transport in the Lower Danube (Garnier et al. 2002; Teodoru & Wehrli 2005). Last, the flux of nutrients and transported material to the Black Sea is influenced by the Danube delta, one of the largest European wetlands and covered by vast reed beds (UNESCO-MAB Biosphere Reserves Directory – www.unesco.org). In general, the ion content increases along the course of the river. Calcium is the major cation, and carbonates, sulphates and chlorides are the main anions. Tributaries with the highest ion contents include the Prut and Siret, where elevated conductivity values result from high sulphate and chloride concentrations (Table 3.3). Suspended solid concentrations increase with drainage size and range

from 27 mg/L to over 40 mg/L. Suspended solid concentrations are positively related to discharge with maximum concentrations during the rising limb of the hydrograph that can exceed 1000 mg/L (Zessner et al. 2005). The Siret and Prut as well as the Inn and Tisza Rivers exhibit the highest mean concentrations of suspended solids. In the Austrian Danube section, suspended solids are dominated by silt (70%) and clay (25%), mainly composed of silicates and secondary limestones of Alpine origin (Nachtnebel et al. 1998). The discharge-weighted annual load of suspended solids ranges from 0.7 to 3.1 106 t/year in the Upper Danube and from 3.5 to 6.3 106 t/year in the Lower Danube (TNMN yearbook 2000–2004). The Inn and Tisza contribute most to the annual load of the river

70

TABLE 3.3 Physicochemical and biological parameters of the main Danube River sections and tributaries based on data from the TransNational Monitoring Network (TNMN) 1996–2005 Organic Ammonium Nitrate Nitrite Total Orthophos- Silicates Calcium Chloride Magnesium Sulphate Suspended TOC DOC Chlorophyll BOD(5) Total (SiO2) nitrogen nitrogen (NH4–N) (mg/L) (mg/L) a (mg/L) (NO3–N) (NO2–N) phosphorus phate (Ca2+) (Cl ) (Mg2+) (SO4 ) solids (mg/L) (mg/L) (mg/L) (PO4–P) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L)

Upper Min. Danube Mean Max. n

247 386 641 1489

3.7 10.9 28.0 1501

7.5 8.2 9.0 1490

1.0 2.6 5.2 293

0.6 2.3 5.3 1578

4.4 4.7 5.2 10

24.0 57.2 101.0 1190

7.0 17.6 53.0 1577

6.1 12.8 30.4 1190

Middle Min. Danube Mean Max. n

121 389 833 4279

n.d. 9.8 18.3 4451

6.2 8.0 9.0 4393

0.7 2.6 8.0 1037

0.2 6.8 25.0 1576

6.7 53.7 117.0 3322

2.0 20.6 46.0 3273

0.0 14.2 1067.0 3331

3.4 37.6 108.0 3243

0.4 4.6 15.2 1319

2.9 3.8 4.9 12

Lower Min. Danube Mean Max. n

219 397 793 1780

n.d. 8.6 16.5 1787

n.d. 7.9 9.0 1785

0.6 2.4 4.9 236

0.7 7.8 21.8 842

10.4 55.9 164.0 1623

Delta Min. Danube Mean Max. n

314 444 1353 1540

n.d. 8.6 14.5 1653

n.d. 7.8 8.7 1658

0.6 2.3 4.7 363

n.d. n.d. n.d. n.d.

0.1 1.6 9.0 1661

0.4 8.4 24.6 1404

9.2 53.1 84.1 1524

7.3 20.5 67.8 1523

1.0 36.1 405.0 1596

n.d. n.d. n.d. n.d.

n.d. n.d. n.d. n.d.

Inn

Min. Mean Max. n

131 245 474 257

8.1 11.2 15.9 257

7.3 8.2 8.6 257

0.6 0.8 1.2 7

n.d. n.d. n.d. n.d.

0.2 0.6 6.1 252

n.d. 3.4* n.d. 1

20.0 33.6 46.5 22

5.6 9.4 13.3 21

n.d. n.d. n.d. n.d.

n.d. n.d. n.d. n.d.

Morava

Min. Mean Max. n

271 484 693 119

6.2 11.4 14.8 119

7.5 8.1 8.8 119

1.9 3.3 5.1 11

n.d. 7.5* n.d. 1

31.3 60.3 100.0 119

9.7 27.8 47.9 119

3.6 10.8 24.9 119

35.0 73.0 102.4 119

1.0 35.9 619.0 119

2.0 6.2 32.6 107

1.6 4.4 10.4 119

Vah

Min. Mean Max. n

316 458 704 146

5.2 9.8 13.8 146

7.5 8.1 9.0 146

1.3 2.8 4.8 72

0.6 2.0 3.4 146

n.d. 3.1* n.d. 1

39.4 62.6 92.2 146

8.5 22.0 38.5 146

23.3 44.0 88.8 146

2.2 3.7 7.5 133

3.1 3.9 4.7 12

1.0 20.1 167.1 121

0.9 3.0 13.0 145

Drava

Min. Mean Max. n

22 293 585 798

6.1 10.4 16.4 824

6.2 7.9 8.8 824

2.1 6.3 8.7 60

12.0 44.2 72.0 672

1.3 8.8 27.6 660

2.0 11.9 26.2 659

5.0 29.0 56.0 620

1.0 18.1 172.5 706

0.6 2.3 8.5 186

0.8 1.5 4.6 11

PART | I Rivers of Europe

Conduc- Dissolved pH oxygen tivity (mS/cm) (mg/L)

Min. Mean Max. n

3.5 9.0 13.2 651

n.d. 7.8 8.5 644

0.7 1.6 2.9 174

10.0 38.5 92.0 524

3.6 10.3 89.0 523

4.6 49.2 102.0 524

2.8 6.8 24.4 233

3.0 3.9 5.5 9

Sava

Min. Mean Max. n

232 391 641 1176

3.3 9.4 17.3 1182

6.6 7.9 8.8 1160

0.5 1.9 5.6 633

0.1 1.3 4.2 1173

n.d. 4.7* n.d. 1

6.1 57.8 91.6 808

4.0 21.4 78.7 801

1.3 3.2 14.5 170

1.0 2.5 5.6 189

1.1 1.1 1.1 1

Velika Min. Morava Mean Max. n

266 431 670 93

7.9 11.3 15.2 95

6.9 7.7 8.8 79

1.5 2.8 6.0 57

0.5 1.6 4.6 93

0.01 0.10 0.26 91

n.d. 0.2* n.d. 1

42.1 52.7 74.0 39

3.5 9.7 15.4 32

7.0 18.2 32.2 39

11.7 23.7 49.0 33

1.5 2.5 3.8 10

n.d. n.d. n.d. n.d.

n.d. n.d. n.d. n.d.

0.5 3.3 6.7 72

Iskar

Min. Mean Max. n

297 453 737 71

4.8 8.9 14.8 70

6.9 7.9 9.0 71

n.d. n.d. n.d. n.d.

0.1 0.3 0.5 3

0.1 0.6 1.6 38

0.02 0.64 3.36 60

n.d. 3.5* n.d. 1

20.0 55.7 80.0 64

7.0 17.5 41.3 64

9.6 54.5 123.1 60

10.0 33.4 141.0 71

n.d. n.d. n.d. n.d.

n.d. n.d. n.d. n.d.

1.1 3.5 10.6 70

Siret

Min. Mean Max. n

410 660 1243 106

n.d. 8.3 13.5 109

6.7 7.9 8.8 109

0.8 2.9 5.8 23

n.d. n.d. n.d. n.d.

0.1 0.8 3.4 109

0.6 2.1 7.6 109

1.9 8.4 16.8 98

23.3 63.5 113.0 109

20.6 79.0 196.8 109

9.4 23.7 59.0 108

22.8 63.7 176.0 106

2.0 98.6 762.0 108

n.d. n.d. n.d. n.d.

n.d. n.d. n.d. n.d.

0.7 4.3 8.4 108

Prut

Min. Mean Max. n

298 672 1320 199

n.d. 8.6 15.4 277

n.d. 8.1 8.8 284

1.1 2.8 4.9 22

n.d. n.d. n.d. n.d.

1.2 7.4 16.6 96

19.4 64.4 153.2 279

14.2 41.1 186.7 279

4.9 21.4 65.6 278

31.0 105.9 270.0 276

n.d. n.d. n.d. n.d.

n.d. n.d. n.d. n.d.

Chapter | 3 The Danube River Basin

Tisza

Minimum, mean, maximum values and number of measurements (n) are shown.
71

72

with loads ranging from 0.7 to 2.5 106 t/year. The Iron Gate reservoirs cause a >50% reduction in suspended solids in the Lower Danube (Petschinov 1987; Friedl & W€ uest 2002; Teodoru & Wehrli 2005; Kalchev et al. 2008). Reduced sediment input, in concert with other human induced impacts along the river, has lead to a decrease in recent Danube delta development. This change follows a 12 000 year evolution characterized by active progradation (Panin & Jipa 2002).

3.6.2. Water Quality Over the last 50 years, water quality has become a key issue for the Danube and the coastal zone of the Black Sea (Schmidt 2001). The first attempt to map the water quality in the basin was made by Liepolt (1967). Between the 1950s and 1970s, water quality was particularly impacted downstream of cities and industrial areas in the Upper Danube. In addition, the self-purification capacity of the river suffered from toxic industrial wastewater inputs. In the early 1980s, construction of wastewater treatment plants (WWTP) led to a major reduction of biodegradable organic matter and improved the water quality in the Upper Danube (Wachs 1997). Water quality in the Middle and Lower Danube remained relatively high (class II) between 1950 and the 1970s (Russev 1979; Kalchev et al. 2008), but deteriorated afterwards due to rapid industrial development, poor pollution control, and inputs from heavily polluted tributaries. The total phosphorus (P) content, calculated using a model-based approach (MONERIS, see details in Kroiss et al. 2005), significantly decreased since the early 1980s due to the introduction of P-free detergents and P-precipitation in treatment plants in upstream countries. The economic breakdown in downstream countries also led to significant reductions from agricultural and industrial sources. In combination with the retention of P in the Iron Gate reservoirs, P loads decreased to levels found in the 1950s. The present total nitrogen (N) load into the river is still 2.2 times higher than in the 1950s, although inputs have slightly decreased since the peak in the 1980s. The total annual nutrient load in the river was estimated to be around 750 000 tons N/year and 68 000 tons P/y. For nitrogen, the main sources are groundwater (from agricultural inputs) and WWTPs (about 67% of all sources). For phosphorus, WWTPs and land erosion are the dominant sources (>80% of all sources), emphasizing the importance of point sources of phosphorus (Kroiss et al. 2005). The relative contribution of different countries and of different sub-catchments varies considerably for P and N. Todays total N and P loads are 10 times above natural background values. Silica loads have only increased by 10% due to human impacts. Long-term data demonstrated that during the past decades between 400 000 and 500 000 tons N/year, between

PART | I Rivers of Europe

15 000 and 20 000 tons P/year (Kroiss et al. 2005) and between 150 000 and 300 000 tons Si/year are exported by the Danube into the Black Sea (Humborg et al. 1997). Peak loads for N and P occurred in the 1980s and early 1990s. Differences between loads from the basin and fluxes into the Black Sea are 300 000 tons N/year and 50 000 tons P/year (Kroiss et al. 2005), and show the high retention and transformation capacity of the basin. In a recent study, Teodoru & Wehrli (2005) showed that the Iron Gate reservoirs are of relatively low importance in retaining sediments and nutrients. The numerous dams along tributaries and the mainstem upstream of the Iron Gate reservoirs may account for these differences, as well as the natural retention capacity of small tributaries. Friedl et al. (2004) showed that <4% of the dissolved silica in the river is retained in the Iron Gate reservoirs, pointing to the role of the large number of other reservoirs within the basin in nutrient retention. Regardless, the Iron Gate reservoirs still play an important role in the retention of suspended sediments and P. Nitrate is the main component of N transported in the river (>70% of total N), and nitrate concentration decreases with increasing river size (Table 3.3). Ammonia and nitrite contribute <10% to the total N load. Nitrate shows a distinct seasonal cycle with peak values in winter. Organic N and P are positively related to discharge. During low flow, phytoplankton comprise a dominant fraction of the organic N (Literathy et al. 2002). Phosphorus in transport is mainly bound to particles. In the Upper Danube, major floods (with a probability of once in 10 to 100 years) can transport between 25–65% of the total annual P-load (Zessner et al. 2005). Dissolved silica, another key nutrient important for algal growth in aquatic ecosystems, exhibits a mean concentration between 4.7 and 8.4 mg/L in the Danube and increases with river size (Table 3.3). The molar ratio of dissolved inorganic P to N indicates that the river is generally P-limited for primary production when light is not limiting primary producers (Turner et al. 2003). Today, the mainstem of the Danube has relatively good water quality (classes II to II–III). A few tributaries have water quality lower than class III for single nutrient parameters (e.g., Morava, Iskar, Siret and Prut Rivers). Since 2000, the organic carbon load (expressed as TOC) and the BOD5 (biological oxygen demand during 5 days) have been monitored in the Danube and its tributaries. The TOC load increases from 70 000 tons/year to 550 000 tons/year from the Upper to the Lower Danube. The Tisza and Sava are main contributors of TOC. Excessive organic pollution can still be observed in some Romanian and Bulgarian tributaries such as the Olt, Iskar and Prut (Schmid 2004; TNMN 2000–2005) (Table 3.3). Phytoplankton biomass and composition are included in the water quality assessment. Phytoplankton play an important role in the biogeochemistry and food webs of most large rivers (Thorp & Delong 2002). The highest phytoplankton biomass was found in the Middle Danube and in tributaries,

73

Chapter | 3 The Danube River Basin

FIGURE 3.4 Phytoplankton biomass and zooplankton density patterns along the Danube River (data: Literathy et al. 2002).

biomass is highest in the Morava (Table 3.3). During 2001, a significant chlorophyll a peak was detected in the Hungarian section of the river, followed by a peak in zooplankton some 300 km downstream of the peak (Literathy et al. 2002, Figure 3.4).

3.7. BIODIVERSITY The Danube River Basin is a ‘hot spot’ for European freshwater biodiversity based on traditional zoogeographic as well as recent phylogeographic studies. The Danube is rich in biodiversity because of its orientation and history. The predominantly east–west alignment of the basin made it a corridor for migration and recolonization, both before and after the ice ages as freshwater organisms moved between the Ponto-Caspian and central Asian biogeographic regions to the east and the Alpine and Mediterranean regions to the west. The mainstem of the Danube was unglaciated, and served as a ‘refuge’. As the ice sheets retreated, freshwater species expanded from this refuge to the rest of Europe. The Danube delta also is a meeting point of Palaearctic and Mediterranean biogeographic zones with a high number of wetland habitats and a rich biodiversity. Since sub-Mediterranean floristic and faunistic elements are common in northern Serbia and along the mainstem of the Danube up to the Iron Gates, it is assumed that the Vardar and Morava Rivers (the so-called ‘Vardar breach’) played a major role in connecting the Danube with the Mediterranean (Matvejev & Puncer 1989; Lopatin & Matvejev 1995; Stevanovic 1995).

3.7.1. Riparian Vegetation The riparian zone is a major part of most riverine systems, providing ecotones with high biodiversity. The main characteristic is the flow or floodpulse of the river and, hence, the periodic change from an aquatic to terrestrial ecosystem (Tockner et al. 2000). In particular, riparian vegetation features specific species adapted to such changes, and some root systems are interconnected to a variable groundwater table. Riparian vegetation also follows a natural

geographic gradient from alpine headwaters to lowland floodplains. Riparian zones provide many ecological functions and services. Riparian vegetation is a major source of allochthonous POC along the river continuum (Vannote et al. 1980). A major function of riparian vegetation is the adsorption and buffering of nutrients entering the river channel, especially from agricultural lands. Denitrification is promoted, mainly in floodplains, preventing excess nitrate in groundwater. The roots of trees and shrubs also stabilize river banks, hence, reducing erosion and sediment/soil transportation. Once partly eroded, roots and woody debris provide shelter and habitat for fish. In small streams, riparian vegetation provides shade and reduces irradiance, thereby ameliorating temperature extremes and preventing excessive macrophyte and algal growth. Riparian trees provide shelter for fish against predation and habitat to water birds for feeding, resting, hiding and breeding. Riparian vegetation along the river corridor can mitigate habitat fragmentation induced by man. While much riparian vegetation has been destroyed in the course of deforestation and river regulation, especially in the Upper Danube, significant amounts of riparian vegetation are still present in larger floodplain areas in the Middle and Lower Danube, such as the Gemenc floodplains (Hungary), the Kopacki rit (Drava confluence to the Danube), the Green Corridor and the delta. There are no detailed data available of how much riparian vegetation has been lost along the Danube and its tributaries. However, the loss of floodplains (including riparian vegetation) is significant, showing that only 5%, 25%, 28% and 70% of the original floodplains remain in the Upper, Middle, Lower Danube and delta, respectively (Schneider 2002). Rehabilitation of riparian vegetation in the course of river restoration projects requires space. Providing just a small strip of trees (‘green tubing’) may be aesthetic in terms of the landscape but is insufficient with regard to ecosystem function. River restoration needs botanical knowledge by choosing native species and fighting invasive species that can be a great nuisance (e.g., the Himalayan Balsam Impatiens glandulifera that presently ‘explodes’ and suppresses other flora in Danube floodplains downstream of Vienna).

3.7.2. Vegetated Islands Vegetated islands are key landscape elements along dynamic river corridors; at the same time they are among the first elements that disappear as a consequence of river regulation. Along the Danube corridor, a total of 349 islands occur of which 5 are >1000 ha, 63 are between 100 and 1000 ha, 117 between 10 and 100 ha, and 163 are <10 ha. Islands are particularly abundant in the Bulgarian/ Romanian section of the Danube (Rkm 400–700) and in the middle reach in Hungary (Rkm 1200–1600). The combined total area of all

74

FIGURE 3.5 Present distribution of vegetated islands (location and average area) along the Danube River (Tockner, unpublished data).

islands is 134 000 ha (Tockner, unpublished data). The average area per island increases along the corridor, (Figure 3.5) and the remaining islands have high conservation value. Islands provide important ecotonal habitats, and they are on average less disturbed than adjacent floodplain areas. As such, vegetated islands play important stepping stones for aquatic and terrestrial floodplain organisms along the river corridor. Along the Bulgarian stretch of the Danube, 75 islands with a total area of 10 700 ha provide habitat for 1100 animal species including 65 fish species and 160 bird species. Along the Romanian stretch, 111 islands cover an area of 11 063 ha (http://www.panda.org/index.cfm). Along the Austrian section of the Danube, about 2000 islands were present before regulation, but only a few remain (K. Tockner, unpublished data).

3.7.3. Macrophytes Liepolt (1967) and Kusel-Fetzmann et al. (1998) provide a comprehensive overview of the macrophyte flora in the basin. More recently, macrophytes were mapped along the entire Danube corridor, including selected floodplain waters in the frame of the Joint Danube Surveys (JDS1 in 2001 and JDS2 in 2007, Literathy et al. 2002; Liska et al. 2008) and of the Multifunctional Integrated Study of the Danube Corridor (www.midcc.at, Janauer & Wychera 2002; Janauer et al. 2003). During JDS1, a total of 49 aquatic macrophytes was identified, including 14 mosses, 16 spermatophytes – submerged rhizophyte species, 9 spermatophytes – floating leaf and free floating plants, 6 amphiphytes, 3 helophytes and 1 Characeae (Phycophyta). In the Upper Danube, bryophytes (mosses) dominate (67–89% cover). Higher plants (11–28%) are mostly restricted to impounded sections. Spermatophytes – floating leaf and free floating plants dominate downstream Danube sections where water transparency and flow velocity are low. Submerged rhizophytes are present along the entire corridor. A highly macrophyte rich section is the (former) inland delta downstream of Bratislava. In the impounded section of the Gabcıkovo hydropower plant, Potamogeton pectinatus,

PART | I Rivers of Europe

Zannichellia palustris and Potamogeton nodosus are dominant. Adjacent floodplain waters are primarily colonized by Elodea nuttallii, Potamogeton spp., Batrachium trichophyllum, Ceratophyllum demersum and Lemnaceae spp. The reed canary grass (Phalaris arundinacea) dominates littoral areas. Two seepage canals, built between 1979 and 1992, were rapidly overgrown by macrophytes (25 species in 2000), including several threatened species such as Apium repens, Groenlandia densa, Hippuris vulgaris and Chara spp. (Otahelova & Valachovic 2002; Janauer et al. 2003). In the ‘Gemenc’ floodplain area in Hungary (Rkm 1498– 1468), 21 species were documented in oxbow lakes, 27 species in canals and 12 species in the main channel.

3.7.4. Macroinvertebrates The aquatic macroinvertebrate fauna of the Danube mainstem, its floodplain waters and its main tributaries have been studied for a long period. Most studies have been conducted to assess the environmental status of the river (Birk & Hering 2002; Birk 2003). The macroinvertebrate fauna of the Danube is highly diverse (Russev 1998; Literathy et al. 2002; Slobodnık et al. 2005; Csanyi & Paunovic 2006). This is a consequence of strong longitudinal and lateral hydrogeomorphic gradients (Literathy et al. 2002; Sommerh€auser et al. 2003). Moreover, the headwater section upstream of the city of Kelheim (Rkm 2415) contains a macroinvertebrate community that significantly differs from all other river sections (Liska et al. 2008). Along the Austrian stretch, between 900 and 1289 macroinvertebrate taxa have been identified (Moog et al. 1994, 1995, 2000; Humpesch 1997). Most taxa have been found in floodplain waters (in total 683), compared to the free-flowing (306) and impounded sections (354). Diptera, Trichoptera and Mollusca are the most diverse groups along the main channel, while Coleoptera, Trichoptera, Mollusca and Odonata dominate floodplain waters. Most recently, three international expeditions, namely the Joint Danube Survey (JDS1 in 2001), the Joint Danube Survey 2 (JDS2 in 2007) and the AquaTerra Danube Survey (ADS in 2004) have been completed. During JDS1, 98 sites were sampled along the Danube (from Rkm 2581 to Rkm 12). In total, 268 species were recorded, including Trichoptera (42 taxa), Gastropoda (30), Ephemeroptera (27), Coleoptera (22), Bivalvia (20) and Crustacea (18). Diptera were not considered. A total of 441 invertebrate taxa were recorded during JDS2 (between Rkm 2600 and the delta); including Diptera and Oligochaeta. During the ADS, which mainly focused on impounded sections, a total of 89 taxa were recorded from 30 cross-sections between Klosterneuburg (Austria, Rkm 1942) and Vidin-Calafat (Bulgaria– Romania, Rkm 795) (Slobodnık et al. 2005; Csanyi & Paunovic 2006). Based on these recent surveys, two distinct patterns were identified: (i) Diptera, Mollusca, Oligochaeta, Amphipoda

75

Chapter | 3 The Danube River Basin

and Trichoptera dominate the macroinvertebrate community along the Danube and (ii) taxon richness decreases longitudinally from the headwaters to the mouth (Literathy et al. 2002; Slobodnık et al. 2005; Csanyi & Paunovic 2006; Liska et al. 2008). The longitudinal decline in taxon richness may be explained by decreasing sediment grain size and heterogeneity in concert with increasing pollution. The Gabcıkovo and Iron Gate reservoirs contain particularly poor macroinvertebrate communities. The Danube is under considerable pressure from the invasion of non-native species (Tittizer et al. 2000; Literathy et al. 2002; Slobodnık et al. 2005; Csanyi & Paunovic 2006; Liska et al. 2008). The opening of the Rhine–Main–Danube Canal in 1992 (also called Main–Danube Canal or Europa Canal) removed a natural barrier between the Rhine and the Danube; a bi-directional transfer of previously geographically isolated faunal elements and genetic potential followed. Today, the Danube serves as a ‘Southern Invasive Corridor’ (Galil et al. 2007) and is an important branch of the Main European Invasive Network (Arbaciauskas et al. 2008), linking the Black Sea basin with the North Sea basin via the Danube–Main–Rhine waterway. For the mainstem of the Danube, Arbaciauskas et al. (2008) reported 19 non-native macroinvertebrate species, mainly of Ponto-Caspian origin (14 species). The PontoCaspian invader Litoglyphus naticoides is today one of the most frequent and abundant species in the basin. In addition, species from New Zealand (mud-snail Potamopyrgus antipodarum) and Eastern Asia (Chinese pond mussel, Eastern Asiatic freshwater clam or swan-mussel – Anodonta woodiana, Corbicula fluminea, C. fluminalis and the tubificid worm Branchyura sowerbyi) have successfully established. Ponto-Caspian species like Dendrocoelum romanodanubiale (Turbellaria), Hypania invalida (Polychaeta) and Jaera istri (Crustacea) have rapidly spread into the Rhine–Main–Danube Canal and the Rhine basin. Dikerogammarus haemobaphes was found in the Main– Danube Canal just 1 year after its opening. Dikerogammarus villosus had already reached the Dutch Rhine by 1994/95 and arrived, via North-German canals, in the Elbe River in 1998. The mussel C. fluminea (93% of all investigated sites during JDS2) and the crustaceans Corophium curvispinum (90%) and D. villosus (69%) are the most frequent nonnative species within the basin (Liska et al. 2008). C. fluminea has recently immigrated into the middle reaches of the Danube via the Main–Donau Canal (Csanyi, 1998–99) and has been sampled down to the delta. In the Middle and Lower Danube, it locally dominates macroinvertebrate communities (Csanyi & Paunovic 2006; Liska et al. 2008). Puky & Schad (2006) reported Orconectes limosus (introduced in the 1950s for farming) to be abundant in the Hungarian Danube. The occurrence of this species in the Serbian part of the Danube in 2004 (Pavlovic et al. 2006) represents the most eastern habitat documented thus far. Eriocheir sinensis is known to occur in the Austrian, Hungarian and Serbian

Danube sections. Moreover, it has been recorded in terrestrial habitats during its migration (Puky & Schad 2006). The Zebra mussel (Dreissena polymorpha), native to estuaries and coastal waters of the Ponto-Caspian and Aral Sea basins, is abundant within the entire basin, while the Guagga mussel (D. rostriformis bugensis), native to the Dnieper and Bug Limans (North Black Sea) is limited still to the Lower Danube (Liska et al. 2008; Arbaciauskas et al. 2008). Today, about 40% of all documented species along the Danube are non-native, underlining their potential impact on native biodiversity and ecosystem functioning (Liska et al. 2008). In numbers, non-native species represent up to 90% of all macroinvertebrates in the Upper Danube valley and even up to 100% in the middle section. For example, C. curvispinum can reach densities of 450 000 individuals/m2 and biomass can be as high as 450 g/m2.

3.7.5. Fish The Danube is the most species-rich European basin. About 20% of the European freshwater fish fauna, that is, 115 native species, occur in the basin (Kottelat & Freyhof 2007). For comparison, about 60 native species are reported in the Rhine basin. Diversity is also high at the local scale because of distinct longitudinal and lateral environmental gradients. For example, more than 45 species occur in the alluvial section between Vienna and Bratislava and 74 species are found in the delta (O¸tel, 2007). The Danube fish fauna was already studied in the 18th and 19th centuries (Marsilius 1726; Heckel & Kner 1858; Antipa 1912). More recent summaries are provided by Banarescu (1964), Balon (1964), Schiemer et al. (2004) and through the JDS2 (Liska et al. 2008). Records of Danube fisheries date back to 335 BC when Greek traders commercialized the fishery in the Lower Danube. The oldest domesticated fish is Cyprinus carpio, which was exploited by Romans in the Pannonian area already 2000 years ago (Balon 2004). Cultivated stocks are assumed to be derived from the wild population in the Danube. Balon (1964) reviewed the longitudinal distribution of Danubian fishes. The number of species increases longitudinally. High diversity is reported in the Hungarian section, the transition zone between foothills and lowlands, with up to 55 native species. Further downstream, the species number remains constant but peaks again in the downstream sections of the Lower Danube and delta. During JDS2 (Liska et al. 2008), Alburnus alburnus was the only species caught along the entire corridor (65 sampling sites) and accounted for almost 50% of all fish captured. Eurytopic species predominated in impounded sections. There are about 30 fish species in the basin, including Hucho hucho, Zingel streber, Sabanejewia bulgarica, S. romanica, Coregonus austriacus, Eudontomyzon danfordi, Gobio carpathicus and Romanogobio vladykovi. Some

76

endemics are restricted to single rivers or single lagoons (Romanichthys valsanicola, Scardinius racovitzai, Cottus transsilvaniae, C. haemusi and Knipowitschia cameliae) (Kottelat & Freyhof 2007). Salvelinus umbla is restricted to Alpine and sub-alpine lakes. The ecological status of the Danube and its fisheries is influenced by river regulation schemes that commenced in the 19th and early 20th centuries. Today, 18 major dams intersect the navigable Danube from Kelheim to the Black Sea. At only two dams (Melk and Wien-Freudenau), fish migration facilities are in operation (Liska et al. 2008). Hydromorphological alterations, in concert with pollution, land reclamation, navigation as well as the introduction of non-native species, have affected the Danube fish fauna. Out of 13 European freshwater fish and lamprey species that have gone extinct since 1700, two species were from the Lower Danube (Alburnus danubicus, Romanogobio antipai), one was endemic to the sub-alpine lake area (Salmo schiefermuelleri) and one occurred in a coastal lake near the delta (Gasterosteus creonobiontus) (Kottelat & Freyhof 2007). About 25 species native in the basin are globally threatened (www.iucnredlist.org), including all sturgeons and the endemic Hucho hucho, Coregonus bavaricus, Umbra krameri, Alburnus sarmaticus and Scardinius racovitzai (Kottelat & Freyhof 2007). About 30 fish species have been introduced during the past century in the basin. Four established non-native species are frequent: Pseudorasbora parva, Ameiursus nebulosus, Carassius gibelio and Lepomis gibbosus. Other established non-native species like Oncorhynchus mykiss, Micropterus salmonides and Perccottus glenii are frequent in certain regions (Kottelat & Freyhof 2007). In many cases, introduction took place via the aquaculture trade; that is, decoupled from waterway transport (Copp et al. 2005). From the 1970s onwards, the invasion of several Ponto-Caspian gobies (Proterorhinus semilunaris, Neogobius melanostomus, N. fluviatilis and N. kesslerii) into Danube stretches upstream of the Iron Gates and thus beyond their native Danubian distribution limit have been reported, coinciding with the general change in the character of the Danube. Moreover, N. kesslerii, N. melanostomus and P. semilunaris have invaded the Rhine and subsequently the North Sea basin through the Rhine–Main–Danube Canal. Since the opening of this canal in 1992, a natural barrier between the Danube and Rhine has been removed and a bi-directional transfer of previously geographically isolated faunal elements and genetic potential followed. Thus the Danube serves as a ‘South Invasive Corridor’ for fish just as for Ponto-Caspian invertebrates (Arbaciauskas et al. 2008). It is a dispersal corridor with Gasterosteus gymnurus invading the Upper Danube and Syngnathus abaster invading the Danube mainstem and reaches on the Romanian-Hungarian border (Kottelat & Freyhof 2007). Today, approximately 30 000 tons of fish are caught each year by commercial and sport fishermen (cited by Wohl in press). Thirty species native to the basin are commercially

PART | I Rivers of Europe

TABLE 3.4 Flood plain loss in the Danube River Basin River stretch

Morphological floodplain (km2)

Recent floodplain (km2)

Loss

Upper Danube Middle/Central Danube Lower Danube Danube delta

1762 8161 7862 5402

95 2002 2200 3799

95% 75% 72% 30%

In total cf. River Rhine

23 187 8000

8096 1200

65% 85%

Data from Schneider (2002).

important. The Danube catch yield has undergone serious regional cutbacks. Construction of the Gabcıkovo River Barrage System near Bratislava, opened in 1992, led to a decline in the annual fish catch by >80% already in 1993 compared to the pre-dam period (1961–1979) (Holcik 1995). Many phytophilous spawners lost their spawning, nursery and wintering grounds. Economically important species such as Cyprinus carpio, Esox lucius, Sander lucioperca, S. volgensis, Aspius aspius, Tinca tinca and Silurus glanis decreased in numbers. In the Lower Danube, the strongest cutback in fishery occurred during the 1960s. Some 72% of the former floodplains downstream of Iron Gate II and upstream of the delta have disappeared or became functionally extinct (Table 3.4). These floodplains served as key habitats for semi-migratory species like C. carpio, Leuciscus idus, Sander lucioperca and Silurus glanis. Moreover, strong declines have been reported for the delta in response to the (i) transformation of connected backwaters into isolated ponds for aquaculture (Ukraine) since the 1960s, (ii) isolation of the frontal marine lagoons from the sea for irrigation purposes from 1970 onwards (Romanian and Ukrainian parts of the delta) and (iii) poldering of about 1000 km2 of the Romanian part of the delta (Schiemer et al. 2004). No description of the Danubian fish fauna would be complete without highlighting the importance of the Danube as one of the last refugia for anadromous sturgeons (family Acipenseridae). The river provides access to almost the last spawning habitats in the Black Sea basin (Reinartz 2002; Reinartz et al. 2003). Two Danube sturgeons are resident species and four species migrate to the river for spawning. However, five out of six sturgeon species native to the basin are critically threatened by extinction and one species, the Atlantic sturgeon, Acipenser sturio, is already extirpated in the basin. The ship sturgeon, A. nudiventris, is on the verge of extinction in its natural range and is only occasionally reported in the Lower Danube. All other sturgeons still have self-sustaining populations in the river. A. ruthenus has undergone a massive decline and anadromous populations have been extirpated. It has self-sustaining populations in the Lower and Middle Danube as well as large tributaries such

Chapter | 3 The Danube River Basin

as the Tisza. It is stocked mostly in the Upper Danube. The spawning success of Huso huso is mostly a result of the relatively uninterrupted Lower Danube stretch (863 km from the mouth to the Iron Gate II) (Lenhardt et al. 2006). A. gueldenstaedtii and A. stellatus are extirpated upstream of the Iron Gates. Overfishing in the Danube and at sea is predicted to lead to extinction of natural populations in the near future (Kottelat & Freyhof 2007). In the Lower Danube, sturgeons were already exploited by ancient Greek colonies in the 5th and 6th century BC for meat and caviar (Reinartz 2002). A decline of Huso huso (beluga) and disputes between upstream and downstream parties about the share of these valuable resources date back as early as the 16th century. During the 18th century, the fishing of migratory sturgeons collapsed in Austria. At the beginning of the 19th century, H. huso was already rare in the Middle and Upper Danube. The construction of the Iron Gate hydropower stations (1972, 1984) had a great impact on sturgeon populations in the Middle Danube (Figure 3.6). Further, over-exploitation at the end of the last century has led to a dramatic decline in sturgeon catch. Although poaching and unreported fishing (up to 90% of the total catch, Reinartz 2002) seems to have decreased lately in the Lower Danube, there is a remaining pressure due to the high commercial value of sturgeon products like meat and especially caviar (Reinartz et al. 2003). Unintentional escapes (e.g., during floods) of exotic sturgeons from hatcheries have been frequently reported. Hybridisation of native sturgeons with escapees can cause serious threats to native populations, as recently demonstrated in the uppermost population of the sterlet (Acipenser ruthenus) which hybridises frequently with introduced Siberian sturgeon (A. baerii) (Ludwig et al. 2008). Recently, single paddlefishes (Polyodon spp., living in North America and China) have been spotted in the Danube reach of Serbia. Since 1998, all sturgeons have been included in the Convention on International Trade of Threatened Species (www.cites.org), which regulates the trade of endangered species and has been signed by all countries in the Lower Danube. In April 2006, Romania banned commercial fishing and the trade of all wild sturgeon products for a 10-year period. In the same year, an Action Plan for the conservation of Danube sturgeons was agreed (AP 2006; Bloesch et al. 2006). It aims to secure viable populations of all Danube sturgeons by sustainable management and restoration of their natural habitats and migratory corridors. Hopefully, it will succeed to preserve at least the ‘Danubian’ Ponto-Caspian sturgeons.

3.7.6. Avifauna The Danube forms one of the most important bird migration corridors in Europe. In addition, the corridor and its adjacent near-natural areas provide resting and breeding sites to 330 bird species. In the Upper Danube, the 100 km2 large Alluvial Zone National Park east of Vienna and the 550 km2 floodplains along the Lower Morava (March) and Dyje

77

(Thaya) Rivers form transboundary wetlands of international importance. The adjacent Lake Neusiedl and Fert€o-Hansag National Parks (Austria and Hungary) contain extensive reed belts, small lakes and traditional pastures and thus provide resting sites for countless migrating birds. Common kingfishers (Alcedo atthis), little ringed plovers (Charadrius dubius), black tailed godwits (Limosa limosa), common sandpipers (Actitis hypoleucos), purple herons (Ardea purpurea), great egrets (Casmerodius albus), black kites (Milvus migrans), white tailed eagles (Haliaeetus albicilla), great bustards (Otis tarda), corn crakes (Crex crex), little bitterns (Ixobrychus minutes), black-headed gulls (Larus ridibundus), common terns (Sterna hirundo) and tufted ducks (Aythya fuligula) are among the birds that occur in these areas. Many of these birds are classified as rare in the Upper Danube due to the massive conversion of wetlands into cropland. For example, only a few little ringed plovers remain in Donauauen National Park, although they had been very common at the beginning of the 20th century (www.donauauen. at). Many of the above mentioned rare birds are still abundant in the downstream sections of the Danube. In the Middle Danube, the Kopacki Rit Nature Park in NE Croatia, the Gornje Podunavlje reservat in NW Serbia and the Gemenc (Photo 3.5) and Beda-Karapancsa areas of the Duna–Drava National Park in Hungary form an alluvial wetland complex of 650 km2. Some areas lack adequate protection status. The area hosts almost 300 bird species, including 140 breeding species. Little egrets, grey-, purpleand night herons (Areidae), whiskered terns (Chlidonias hybridus) and cormorants (Phalacrocorax) breed in large colonies in these wetlands. Moreover, birds that are endangered at both European or even global levels, like whitetailed eagles (Haliaeetus albicilla), black storks (Ciconia nigra), ferruginous ducks (Aythya nyroca), lesser spotted eagles (Aquila pomarina) and saker falcons (Falco cherrug), are reported in this area. Additional particularities are the montagu’s harrier (Circus pygargus) in the cultural landscape and sand martins (Riparia riparia) along the natural banks of the river. Islands in the Lower Danube host intact floodplain forests, sand bars, marshes and natural river channels. They provide habitats for numerous plant and animal species, including pelicans (Pelecanidae) that breed in the delta but use the islands as well as fish ponds to feed and rest when migrating. The Danube delta has a tremendous variety of terrestrial and aquatic habitats. Mediterranean, Eurasian and Black Sea palearctic faunal elements meet in the delta. About 330 bird species have been inventoried. The delta is a nesting place for white pelicans (Pelecanus onocrotalus); about 3500 breeding pairs have been reported in 2001/2002, which is a large share of the western Palearctic population. The Dalmatian pelican (Pelecanus crispus) was represented by about 100 pairs in the 1980s and about 450 pairs in 2001/2002. The latter equals the majority of the European and about 10–15% of the global population of this species. Moreover, about 1/3

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PART | I Rivers of Europe

FIGURE 3.6 Past and present spatial distribution of huchen (Hucho hucho) (a) and sturgeon (Acipenseridae) (b) within the Danube River Basin, after Holcık et al. (1989) and Reinartz (2002). Maps produced by D. Tonolla.

of the world population of pygmy cormorant (Phalacrocorax pygmeus, 9000 breeding pairs) is known to occur in the delta (RIZA 2004). There are also important colonies of spoonbill (Platalea leucorodia) and several breeding pairs of the white-tailed eagle (Haliaeetus albicilla). For millions of

birds, especially ducks, white storks (Ciconia ciconia) and numerous predators the delta is a major stopping place during spring and autumn migration. During winter, the region hosts huge flocks of swans and geese, including the globally threatened red-breasted goose (Branta ruficollis) with

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Chapter | 3 The Danube River Basin

PHOTO 3.5 Duna–Drava National Park at Gemenc in Hungary. (Photo: Christian Baumgartner, Austria).

almost 95% of its world wintering population (http://www. ddbra.ro/en/). Piscivorous birds of the delta have been heavily reduced by fishermen during the 1950s and 1960s. The eutrophication of waterbodies has increased fish food availability and has led, together with protection measures, to a major increase in piscivorous birds since the late 1980s (RIZA 2004).

3.7.7. Wetland Mammals In 1879, the Archduke Rudolf, ornithologist and Crown Prince of Austria, reported dense populations of the Eurasian otter (Lutra lutra) in the floodplains of the Danube east of Vienna (Lobau). Today, this species is extirpated in this area, although the large floodplains could serve as important habitats for otter. Extirpation of the otter was a result of habitat loss as well as dispersion of synthetic pesticides DDT/DDE that decrease fertility. Due to the ban of DDTs and conservation actions, otter populations are recovering across most of Europe (IUCN 2007). Red fox (Vulpes vulpes), wild boar (Sus scrofa) and red deer (Cervus elaphus) are common along the entire Danube. European beaver (Castor fiber) were intensely hunted for their fur and castoreum oil in the past. In the Danube, this key species was extinct for over a century. Reintroductions have enabled its return to much of the former range. Since the 1970s, beaver have been reported in the Austrian Donauauen National Park since 1991 in the Middle Danubian Szigetk€oz area, a 375 km2 wetland between Slovakia and Hungary, and

since 1996 in the southern Hungarian sections of the Duna– Drava National Park. Recently, a beaver dam blocked the famous fish by-pass of the hydropower plant Freudenau near Vienna. The occurrence of beaver is reported for the Kopacki Rit Nature Park since 2002. Beaver are being reintroduced to the Gornje Podunavlje Special Nature Reserve along the Serbian Danube (Rkm 1366 to 1433) by a joint BavarianSerbian programme. The Danube floodplains are important habitats for 12 bat species (Microchiroptera) such as the pond bat (Myotis dasycneme). European pine martin (Martes martes), stone marten (Martes fiona), root vole (Microtus oeconomus), wildcat (Felis silvestris), red deer (Cervus elaphus) and otter (Lutra lutra) are reported to occur in protected areas along the Middle Danube. Golden jackals (Canis aureus) are among the most recent colonialists (Ramsar 2007). About 40 mammal species, including marbled polecat (Vormela peregusna), European ground squirrel (Spermophilus citellus), Romanian hamster (Mesocricetus newtoni), Eurasian harvest mouse (Micromys minutes), Southern birch mouse (Sicista subtilis), steppe polecat (Mustella eversmanni) and least weasel (Mustela nivalis) have been reported on the Ibisha and Belene Islands in the Lower Danube. The delta supports a diverse mammal fauna (42 species), including species of high conservation value such as the otter (L. lutra) and European mink (Mustela lutreola). Since 1850, the European mink has undergone a dramatic decline. It is now extinct in most European countries, occupying <20% of its original range. The most viable population in Western Europe is in the Danube delta, although it is also rapidly

80

declining here. In 2006, only one individual was caught per 250 trap nights compared to one individual per 20 trap nights in 2003 (IUCN 2007). The non-native American mink (Neovison vison) and raccoon dog (Nyctereutes procyonoides) are reported to compete with the European mink. Poaching of otters (L. lutra) has recently increased in the delta (IUCN 2007), and the muskrat (Ondatra zibethicus) and wild boar (Sus scrofa) are commercially important species (fur and hunting). Other predatory mammals in the delta are the ermine (Mustela erminea), fox (Vulpes vulpes) and wild cat (Felis silvestris).

3.7.8. Herpetofauna About 27 amphibian and 37 reptile species are recorded in the basin (Mezzena & Dolce 1977; Engelmann et al. 1986; N€ollert & N€ ollert 1992; G€ unther 1996; Gasc et al. 1997; Cabela et al. 2001; Kwet 2006, http://www.amphibiaweb. org, http://www.globalamphibians.org, http://www.tigr.org/ reptiles/search.php). Two thirds of the amphibians and 1/3 of the reptiles prefer riverine landscape elements; the remaining species occur in adjacent hillslope and upland areas. Only three reptiles are truly aquatic: Natrix natrix, N. tessellata and Emys orbicularis. Vipera ursinii prefers steppic landscapes with moist areas and waters. Salamandra atra can live independent from water, while Salamandra salamandra and Alytes obstetricans are dependent on water in the larval life stages. The amphibians Lissotriton (Triturus) vulgaris, Hyla arborea, Bufo bufo, Bufo viridis and Rana kl. esculenta (Pelophylax kl. esculentus) and reptiles such as Lacerta agilis, Natrix natrix, Coronella austriaca and Anguis fragilis are widespread in the entire basin. Triturus dobrogicus is the only endemic amphibian in the basin, and inhabits valleys and floodplains below 300 m asl. Considering the total size of the basin, it is surprising that no reptile species are endemic. Along small rivers, a distinct sequence of alpine, mountainous and planar species occurs. The main Danube corridor crosses several deep gorges (e.g., near Vienna, Iron Gate). Hence, mountainous species such as Rana temporaria and Bombina variegata are common along some sections of the river corridor. The close link of mountains with lowlands leads to the separation of geographic ranges of lowland species like Triturus dobrogicus and Bombina bombina. Reptile richness peaks in the hilly regions in the southeast of the basin. Along the Croatian, Serbian, Bulgarian and Romanian Danube sections, 20–31 reptile species occur; compared to 7–15 species in the other sections. In contrast, amphibian richness does not change considerably along the entire corridor, remaining at 12 species. Hybridisation is a widespread phenomenon and occurs in half of the Danube basin amphibians; that is, Lissotriton vulgaris L. montandoni, L. vulgaris L. helveticus, Triturus carnifex T. cristatus T. dobrogicus, Bombina bombina B. variegata, Bufo bufo B. viridis B. calamita, and the well-known hybrid complex with Rana

PART | I Rivers of Europe

(pelophylax) lessonae, R. (P.) ridibunda and R. (P.) kl. esculenta with different levels of polyploidy. The closely related species B. bombina (yellow-bellied toad) and B. variegata (fire-bellied toad) hybridise in overlapping areas in Austria, Hungary, Bulgaria and western Ukraine. The high proportion of hybrids, although often not abundant, demonstrates the ongoing speciation process in the basin. Despite the enormous interest in keeping exotic amphibians and reptilians as pets, which can result in abandoned or escaped animals, no introduced alien species have established reproducing populations in the basin until now. Nevertheless, there are problems with the ongoing introduction of Trachemys scripta elegans and other pond turtles, especially in Germany and Austria, because they most likely compete with the native turtle Emys orbicularis. Most amphibians and reptiles are listed in Appendix II of the Convention on the Conservation of European Wildlife and Natural Habitats (Convention of Bern, 1979, http:// www.lcie.org/res_legal.htm) and in the IUCN red list (http://www.iucnredlist.org/). Many species are protected also by national laws (e.g., Puky et al. 2005). Destruction of wetlands is the most serious threat to amphibian populations. Even common species like Lissotriton vulgaris is locally threatened due to drainage, pollution, and destruction of breeding ponds and adjacent terrestrial habitats. In recent years, Triturus dobricus populations suffered from lower spring rains in the south, probably as a result of climate change (IUCN 2006).

3.8. HUMAN IMPACTS, CONSERVATION AND MANAGEMENT Rivers are the ‘veins’ of the landscape and as such they shape landscapes even more prominently than lakes. Rivers have long been used by man as ways of migration and transportation (shipping), collectors of waste, sources of drinking water and food (fish) and hydropower. Conversely, running waters have impacted humans through catastrophic floods and as carriers of disease. Lepenski Vir in the Iron Gates gorge in Serbia, a historical site with tracks of the earliest settlers in Europe (20 000 BC), illustrates the importance of the Danube River for humans. While poets and painters have glorified riverine landscapes as lovely places of nature, only in the last century has river protection become an important social endeavour, mainly initiated by severe pollution and subsequent health and aesthetic issues, and later triggered by water abstraction and morphological changes from impoundments and damming. Recently, droughts (2003) and floods (2002, 2005, 2007) became a priority in the Danube basin, especially since peak flows need space used traditionally for agricultural and urban development. Since the 1990s, limnological concepts have incorporated a catchment approach to better understand the function of aquatic ecosystems, the ultimate foundation of sound river basin management for the implementation of

Chapter | 3 The Danube River Basin

sustainable use of running waters (Bloesch 2005a). Today, river and wetland conservation and management have become standardized and scientifically founded actions (Boon et al. 2000; Bobbink et al. 2008). In the Danube River Basin, they are implemented by the European Water Framework Directive (WFD) with the overall goal to achieve ‘good ecological status’ by 2015 (EC 2000), and in various Directives and Conventions such as the EC Birds Directive 1979 (http://eur-lex.europa.eu/LexUriServ/ site/en/consleg/1979/L/01979L0409-20070101-en.pdf), the EC Habitats Directive for Flora and Fauna 1992 (http:// eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX: 31992L0043:EN:HTML), the UNESCO World Heritage Convention 1972 (http://whc.unesco.org/en/ conventiontext/), and the Ramsar Convention on Wetlands 1971 (http://www. ramsar.org/). The latter two Directives formed the basis for the creation of the Natura 2000 Networking Programme on behalf of the European Commission (http://www.natura. org/). Basic elements of river basin management include the ecoregion, the river type and reference state, and biodiversity (ICPDR 2005). In respect to the general framework for conservation and management, the Danube River is an interesting and special case study for several reasons. First, the basin officially encompasses 19 countries, of which four have only small areas of headwaters (Albania, Macedonia, Italy and Poland). This is by far the largest number at the global scale, featuring a great variety of cultures and mentalities. The multi-cultural setting makes transboundary issues extremely difficult and challenging, although people in the basin have developed a kind of solidarity as ‘Danubian countries’. Whether country borders are along the river (>800 km between Romania and Bulgaria) or across the river (creating the well-known upstream downstream situation) make a significant difference for management. For example, a meandering river does not respect political borders established in the middle of the channel because the channel often shifts from one country to another (e.g., the lower Mura/Drava floodplains). Fortunately, some of these problems are being solved at the political level by bilateral border commissions and governmental mapping agencies. Since 1998, the International Commission for the Protection of the Danube River (ICPDR, www.icpdr.org) is the official forum where issues of water protection and conservation are treated. Using its expert groups, the ICPDR jointly prepares projects and documents for ratification and implementation by national governments. It fosters public participation programmes and is actively supported by many NGOs that have observer status. Through the ICPDR, the WFD is being implemented in the Danube basin. The Espoo Convention 1991 on Environmental Impact Assessment (http://www.unece.org/env/eia/ documents/conventiontextenglish.pdf) also may help to solve environmental problems across political borders. Second, the basin lies in the historical ‘political fault’ between the East and West, reflecting the battles between Asian and Turkish empires and European states, and finally

81

represented by the ‘Iron Curtain’ between capitalist and communist countries. The different political systems have greatly influenced social behaviours, technical developments, as well as water use and protection. Today, this history is illustrated by the situation in the Upper Danube (former West) where mostly ‘clean water flows through heavily modified channels’, while in the Middle and Lower Danube (former East) polluted water flows in more intact channels’ (Bloesch 1999). Third, as a consequence of recent political developments, the Middle and Lower Danube countries in transition have become or are gradually becoming members of the European Union. Hence, economic pressure in these countries will dramatically increase. Subsequent development may severely impact near natural stretches and floodplains of the Danube River and its major tributaries (Sava, Drava, Tisza). Last, the Danube River is the geographical/biological border between east and west, and Ponto-Caspian relicts are still an important part of the natural fauna. However, invasive neozoans and neophytes that threaten native species are prominent, as the trans-European waterway network links the Danube with the Rhine and promotes the exchange of plants, zoobenthos and fish across river basins (Bloesch & Sieber 2003). The Danube pressures and stressors reflect the present state of the Danube River and its tributaries. To initiate and promote conservation and restoration, human impacts must be analyzed to identify ecological deficits. The ICPDR has made an inventory of physical, chemical and biological data, and compiled and described the pressures and stressors in the so-called ‘Roof Report 2004’ (ICPDR 2005). Following a steady increase since the 1950s, nutrient concentrations have decreased since the 1990s due to new wastewater treatment plants in the Upper Danube (by Germany and Austria) and the economic breakdown in the Lower Danube countries (Schreiber et al. 2005; Behrendt et al. 2005). Since dilution of pollution by high discharge plays an important role in the Lower Danube, nutrient concentrations are relatively low and a biological assessment indicates moderate pollution. Some major tributaries are still heavily polluted (Schmid 2004). The high nutrient concentration in the Danube, combined with the loss of 400 000 ha of wetlands along the Lower Danube (drained for agricultural purposes before the 1990s), caused strong eutrophication in the Danube delta lakes after 1980 and a drastic decrease in biodiversity (Va˘dineanu et al. 2001). The recent decrease in N and P load by 18% and 38%, respectively, has improved the situation along the Black Sea coast, but more efforts are needed to lower pollution. Apart from pollution by nutrients and other substances, hydromorphological alterations for hydropower and navigation, and dykes (flood protection) are the main pressures today (WWF 2002; ICPDR 2007a). In total, about 600 major hydraulic structures (dams and weirs >15 m) including 156 hydropower dams have been built along the Danube and in the catchments of its major tributaries, not including the countless smaller dams (Reinartz 2002; Bloesch 2003; ICPDR 2005, Table 3.1).

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FIGURE 3.7 Historical development of the Marchland floodplain in Upper Austria (Rkm 2094–2098): age (average, minimum, maximum) development of the active zone from 1817 to 1991 based on weighted average ages of different habitat types (after Hohensinner et al. 2005). Depending on the modelling method, the age values generally represent maximum values calculated based on the maximum possible cell ages. Minimum and maximum values refer to the range of the potential start age of raster cells that are older than 1715 AD in the habitat age model.

Along the mainstem of the Danube, 69 dams have been built and 30% of its total length is impounded. Upstream of Bratislava, only about 15% (Straubing-Vilshofen: 69 km, Wachau: 28 km, Vienna-Bratislava: 45 km) out of 1000 Rkm remain free-flowing (Figure 3.7). Further, there are 34 dams along the Lech River, Austria/Germany (encompassing 90% of its total length). In contrast, the Isar River (tributary in Bavaria, Germany) represents one of the last natural alpine rivers in Europe. The largest dams are Iron Gate dams I and II at Rkm 943 and Rkm 842 (opened 1972 and 1984, respectively). Each dam is equipped with two navigation locks, an earthen nonoutflow dam, two hydroelectric power plants, and an overflow concrete gravity dam, among other facilities. The reservoir of Iron Gate II extends to the upstream Iron Gate I dam. During low water, Iron Gate I has a backwater zone of 312 km on the Danube mainstem (up to the city of Novi Sad), 102 km on the Sava, 65 km on the Tisza and 20 km on the Serbian Morava. Together with Gabcıkovo dam (built in the 1980s, diversion channel at Rkm 1835 to 1811), the Iron Gate dams disrupted fish migration in the Lower and Middle Danube and significantly changed sediment transportation and the groundwater regime (Zinke 1999; Klaver et al. 2007). The Danube is navigable up to the city of Ulm. From Kelheim (Rkm 2411) to the delta, it serves as an international waterway (87% of the total river length) and navigation is of international importance. In the Upper Danube, navigable tributaries are the Morava (30% of its total length), Raba (29 km at the mouth) and Vah (74 km, 20% of its river length). The Drava is navigable along 20% of its length. The Tisza River serves as a waterway from the UkrainianHungarian border to the confluence with the Danube, about 70% of its total river length. On the Sava, navigation is possible on >50% of the river from Croatia (Kupa confluence) to its mouth in Serbia (see Chapter 3.9.6.4).

PART | I Rivers of Europe

Additional man-made waterways were built along the Danube for transport purposes, including the Main–Danube Canal in Germany that links the Rhine and the North Sea, the Danube–Tisza–Danube Canal System in Serbia, and the Danube–Black Sea Canal in Romania. Presently, a major controversy for the Danube is the European Union’s plan to develop the Trans-European Networks for Transport (TEN-T) Corridor VII along the Danube. The project aims to remove navigation bottlenecks along the Romanian-Bulgarian section, the entire 379 riverkm from Mohacs to Palkovicoko in Hungary, the 48 km freeflowing section east of Vienna in Austria, and the 80 km free-flowing section between Vilshofen and Straubing. Another goal is to improve navigation between eastern and western Europe through the construction of hydraulic modifications and canals. The proposed Danube–Odra–Elbe Canal is another threat to the Danube. If realized, it would affect 46 000 ha of 38 protected areas, including two national parks, six Ramsar sites and two biosphere reserves (Baltzer 2004). Other major projects are the Bystroe Channel in the Ukrainian part of the Danube delta for navigation (Bloesch 2005b), the Braila–Calarasi section in the Green Corridor for navigation, the Drava and Sava floodplains for hydropower, navigation and gravel extraction and the construction of a Danube–Adria waterway through the Sava River (http:// www.euronatur.org/Sava.sava.0.html). Further plans intend to connect the Vardar River (Macedonia) with the Danube. It is a great political challenge to protect ‘vaste’ land against all these economic pressures. An estimation of the total floodplain area in the Danube basin is 60 000 km2 (7.5% of the total area). Historically, this area would have been affected by regular and periodic inundation in the absence of flood defences. About 65% of the former floodplains have been lost or are now functionally extinct (Figure 3.8, Table 3.4). Canalization of the Danube has also truncated the natural balance between succession and rejuvenation processes. Before regulation, the average age of different floodplain habitats in the Upper Danube was 50–60 years and remained relatively constant over time. Following regulation, habitat age has increased and there has been a loss of early succession habitats (Hohensinner et al. 2005). Some 6% of the total human population in the basin lives in areas below flood level. An even higher share of national assets and infrastructure can be affected by floods or is protected by flood defences (ICPDR 2004). The total length of flood embankments exceeds 13 000 km. Deterioration of morphological structure and riverine habitats, the longitudinal disruption of fish migration, the lateral disconnection of floodplains and wetlands, as well as navigation effects have reduced the abundance and biodiversity of biota (Schneider 2002; Schneider-Jacoby 2005). In particular, the endangered Danube sturgeon is near extinction, and 72 actions for their conservation have been proposed in the Sturgeon Action Plan in the framework of the Bern Convention (AP 2006; Bloesch et al. 2006). In comparison with other large

Chapter | 3 The Danube River Basin

83

FIGURE 3.8 Extension of former inundation areas along the Danube River (area shaded in light blue)(from Ulm, Germany, downstream to the mouth). Dark blue band marks the average width of the main river channel based on Laszloffy (1967) and modified after Tockner et al. (1998).

European rivers such as the Rhine, the Danube still has comparatively larger near natural sections with intact ecological functions (Bloesch & Sieber 2003). Major actions and measures are needed to protect and properly manage the Danube River and its tributaries. The big question is which comes first: conservation or restoration? From the ecological deficits identified above, measures for remediation can be derived. Mapping the hydromorphological structures according to CEN-Standards provides a

powerful tool for managers (Schwarz 2007). The scaling within the river basin must be used to define the appropriate goals and to implement concrete actions (sensu Frissell et al. 1986). Pollution problems are shifting from nutrients to ‘priority substances’ such as persistent organic compounds (PAHs and PCBs) and hormone active substances (endocrine disruptors). Heavy metals are accumulating in the sediments and mercury (Hg) is subject to bio-accumulation through the food chain. A principally ‘sustainable’ approach is to tackle

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the causes or sources of pollution rather than the effects (known as ‘end-of-pipe-solutions’). It is clear that modern technology must play a major role in solving these problems (see also WFD recommending the combined approach of rigid Environmental Quality Standards, Emission Limit Values and Best Available Techniques). Low-tech solutions using wetlands as a purification step can be an effective and cost-efficient alternative. Former and future hydrological and morphological alterations require an even stronger use of management measures as they include the riparian areas and ecotones along the aquatic–terrestrial interface, both hotspots for biodiversity. Numerous ecological restoration projects, mainly in the Upper Danube, illustrate the success of interdisciplinary measures (e.g., Donau–Auen-National Park, Vienna). An innovative approach was presented for Nature Park Lonjsko Polje (Sava River) by Schneider-Jacoby (2007) using riverine floodplains not only for flood protection, but also for sustainable forestry and agriculture. Boon (2005) discussed the strategic problem whether conservation of what is left from technical impacts has priority over restoration of what has been morphologically altered and destroyed. In the long-term, both from an ecological and economic point of view, conservation has a much better cost-benefit ratio than restoration. Hence, the few large lowland floodplains in the Danube and larger tributaries like Sava, Drava and Tisza, must be conserved and used in a strictly sustainable way. This is ‘soft’ eco-tourism that shows goods and services of nature reserves, restricted fishing, moderate shipping, flood protection by using the retention potential of natural floodplains (as recommended by the EU Flood Directive – Directive 2007/60/EC on the assessment and management of flood risks, 26 November 2007 – and the EU Floods Action Programme), and a strong political regulation for proper landscape planning. Where the river has already been altered by damming and impoundment, restoration should be performed by creating new habitats, giving more space to the river, and reconnecting floodplains in particular. A good conservation example is the UNESCO Biosphere Reserve in the Danube delta where outdated management practices such as the capture fishery period (1903–1960), the reed exploitation period (1960s), the fish culture period (1971–1980), and the agriculture-polder period (1983– 1989) have been replaced by more sustainable uses (G^as¸tescu & S¸ tiuca˘ 2006, see section on the Danube delta). Core areas and restoration zones represent only 9% and 3%, respectively, of the total delta area (4560 km2), while buffer zones cover 39% and economic zones 53% (Baboianu 2002). S¸ tiuca˘ et al. (2002) showed that hydrological and ecological restoration is beneficial for the economy. For instance, restoration costs of flushing the Babina and Cernovca polders (3680 ha) amounted to 100 000 USD and yielded an annual benefit of 140 000 USD via lower labour costs. The importance of integrated management measures at the catchment scale has been emphasized by the adoption of River Basin Management Plans at the EU level. Increasing

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attention is being given to wetlands because their multiple ecological functions are regarded invaluable (e.g., water storage, connectivity of surface and ground waters, biochemical cycling of nutrients, retention of suspended and dissolved materials, and hotspots of biodiversity). An ultimate goal of river conservation and restoration is to ensure ecosystem functioning and to maintain naturally high biodiversity. This is in general contradiction to the often irreversible ecological damage caused by flood protection, navigation and hydropower development. When applying an open discussion and using clever strategies, a paradigm change can yield acceptable solutions, as shown in a recent restoration project on the Danube near Vienna (Reckendorfer et al. 2005). Size matters in the Lower Danube, where the negative impact of technical measures may be recognized only after a long period such as in Gabcıkovo where the floodplain forest is changing over time due to lost flood dynamics and a lower groundwater table. Similar long-term effects occur along the Green Corridor where the floodplains were disconnected by longitudinal damming by Romania. Sustainable river management theoretically provides the balance between use and protection. Use and protection (conservation) are the focus of most conflicts of interest and need to be balanced in river management. While sustainable use is propagated by almost all politicians, the real problem is its implementation (Bloesch 2005a). The definition of this term is still far from being clear and our society is still far from behaving in a sustainable way (Jucker 2002). Implementation is made further difficult because not only methods and strategies but also legal aspects need to be harmonized among the Danube countries (Bogdanovic 2005). Besides those legal documents for Danube protection listed earlier, we mention the Danube River Protection Convention, the Danube Navigation Convention and the Danube Sub-Basin Commissions on the Sava and Tisza. Danube River Basin management is an ongoing and dynamic process that must be based on sound scientific knowledge and must be implemented pragmatically.

3.9. MAJOR TRIBUTARIES AND THE DANUBE DELTA 3.9.1. Inn River The Inn River (En in Romansch; Oenus or Enus in Latin) has a catchment of 26 128 km2, is 515 km long, and drains parts of Austria, Switzerland and Germany (some 254 km2 is in Italy) (Photo 3.6). In Passau, at its mouth (Danube Rkm 2225), the Inn carries for the most part of the year more water than the Danube River; during snowmelt the discharge of the Danube might exceed the discharge of the Inn. The Salzach River is the main tributary of the Inn. Around 35% of the basin is covered with forests, 15% is arable land (Table 3.1), and the remaining area mainly consists of alpine grasslands and bare rock. The Inn basin

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PHOTO 3.6 Inn River in Kuftsein. (Photo: Hydrographic Service Tyrol, Austria).

contains >800 glaciers with a total area of 395 km2 (Tirol 2006); all are receding due to global warming. The Inn has been an important floatway for timber to Innsbruck and even Vienna. Today, navigation is of limited importance (Inn 2002). The basin is inhabited by 2.2 million people. The largest cities along the Inn/Salzach are Salzburg and Innsbruck (150 000 and 120 000 inhabitants, respectively).

3.9.1.1 Geomorphology The Inn starts as the outlet of Lake Lughino in the Swiss Alps near St. Moritz (2484 m asl), runs northeast through the lake chain in the Engadin valley as it passes over crystalline, schist and quartz phyllite units. In Austria down to Innsbruck (570 m asl), the Inn valley forms the border between the northern limestone and the central crystalline Alps. The slope of the upper Inn ranges between 2 and 11‰ (Inn 2002). Geology of the western Salzach valley mainly consists of quartz phyllite, crystalline and wacken. Downstream of Innsbruck, the Inn flows through a wide valley before it traverses the alpine belt at Kufstein, enters the alpine foothills, and crosses the Bavarian plateau. Here the slope decreases to 1‰. After the confluence with the Salzach, the Inn forms the border between Bavaria and Austria. Its morphology has been heavily regulated with most banks fortified with riprap and short groynes. Natural riverbanks are restricted to short gorge stretches in the upper Inn and

natural bedrock sections (Inn 2002). Less than 20% of the total length of the mainstem is free-flowing and in a nearnatural state (ICPDR 2005), although some man-made floodplains have been established in the lower Inn.

3.9.1.2 Climate, Hydrology and Biogeochemistry The average annual air temperature in the catchment is 4.6 C (Table 3.1). The average water temperature is 7.3 C (1991–2005). The hydrology is mainly influenced by a high alpine character and exhibits a nivo-glacial regime. Peak flows occur in early summer when heavy rain falls on snow. Some 80% of the upper and middle catchment is in the dry central Alps (‘Inner valleys’ such as the Engadine valley), and 20% is in the precipitation rich northern limestone Alps (Inn 2002). At Innsbruck, average discharge from December to March is 50 m3/s and increases to 130 m3/s by July (Tirol 2008). The average discharge at its mouth is 732 m3/s, and peak discharge (1% probability of occurrence) is 5600 m3/s (Table 3.2, ICPDR 2004). Starting in 1920, the mainstem was converted into a chain of 19 hydropower plants. The tributaries are intensely trained as well; along the Ziller and Sill tributaries there are, for example, 40 power stations (Inn 2002). Especially in the upstream sections, hydropeaking through pulse releases causes daily water level fluctuations of up to 1.4 m. In Innsbruck, the fluctuations are still up to 0.75 m. Bedload

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transport decreased from 540 000 tons/year before the 1920s to 180 000 tons/year in 1960, and is near zero today (ICPDR 2005). Snow-water from tributaries delivers glacier silt and mud, causing a high load of suspended matter and a milky, green water colour in the Inn. Thus, at its confluence with the Danube, the algal content (chlorophyll a levels) of the Danube is reduced by almost 50% (Bergfeld et al. 2001). The average dissolved oxygen concentration is 10.5 mg/L, and BOD5 3 mg/L. Nitrate–nitrogen (NO3– N) is as low as 1 mg/L. Total P is around 0.15 mg/L. Low nutrient and organic matter levels in the Inn (and Upper Danube) are the result of high elimination efficiency by municipal and industrial wastewater treatment plants (ICPDR 2005).

3.9.1.3 Biodiversity Along the Austrian Inn, >50% of the former fish fauna (35 species) have disappeared mostly due to habitat loss and hydropeaking. Many of the remaining 17 species are restricted to small sections, although grayling (Thymallus thymallus) and brown trout (Salmo trutta) still occur along the entire section. After construction of the first hydropower plant at Jettenbach in 1921, the commercial fishery collapsed (ICPDR 2005). In 2000 fish biomass averaged 54 kg/ha, which is a rather low value for a river of this size. Downstream of Innsbruck, fish biomass was as low as 10 kg/ha (Inn 2002). Without stocking, fish abundance and biomass would even be lower because natural reproduction is limited. Spindler et al. (Inn 2002) examined the hydro-morphological status of 116 tributaries of the Inn. Only five are considered as near natural, and 14 have undergone only minor anthropogenic impacts. Twenty-six (22.4%) are classified as considerably degraded and 11 are strongly altered. The majority of tributaries (60 equaling 51.7%) are classified as non-natural, their integrity has been permanently altered along their entire length. More than 35% of all tributary junctions are impassable for fish, and inaccessible for spawning fish. In tributaries with fish, rainbow trout and brown trout are most common. Graylings, once very common, account for only 3% of the total fish biomass. Minnows (Phoxinus phoxinus), another former common species in smaller tributaries, are rare. Quantitative fishing in 47 tributaries of the Inn revealed that 11 are without any fish. Almost 50% of the catch yield can be assigned to small brooks along meadows, as they serve as important breeding habitats (Inn 2002). Along the lower Inn in Austria and Germany, two contiguous Ramsar sites with an area of 2865 ha were designated in 1976 and 1982. This 25 km long stretch of the Inn comprises four storage lakes, sediment banks, riverine forests, muddy banks, successional vegetation of various ages, a series of islands and extensive reedbeds that support a wide variety of rare plants, the reintroduced European beaver, as well as the re-immigrating European otter (www.ramsar.

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org). The lower Inn reservoirs and floodplains are important areas for resident and migrating birds. In autumn and spring, up to 25 000 limicolae, other shorebirds, and birds from the high-arctic tundra are present.

3.9.1.4 Human Impacts and Management Regulation of the Inn started as early as in the 15th century. The aim was to gain agricultural land in the river valley and to facilitate navigation. Up to 1940, over 700 groynes were constructed (often along both banks). In the late 1960s and early 1970s, the course of the river was partially moved to allow the construction of motorways. In 1855, floodplains covered about 1600 ha, today only 210 ha remain as altered floodplain forests (Bloesch & Frauenlob 1997). Beginning in the 1920s, many tributaries were used to generate hydropower. Reservoirs are flushed about two times per year and clogging (colmation) of bed sediments is an issue for benthic communities and fish spawning. River restoration has been implemented in the upper Inn in Switzerland (4 km stretch from Celerina to Bever and 6.5 km from La Punt Chamues-ch to S-chanf). Along a 31km stretch between M€uhldorf and Waldkraiburg in Bavaria, restoration works were started in 2003 and should be finished in 2014. Further mitigation measures include the installation of retention reservoirs to lower the negative effects of hydropeaking, and additional fish passes are necessary to enhance the migration for rheophilic species such as the barbel (Barbus barbus) and nase (Chondrostoma nasus). Riverbed widening and an active management of the bedload are required to restore spawning habitats (Inn 2002).

3.9.2. Morava River The 354-km long Morava River (German: March, Latin: Marus) is a Central European lowland river that originates in the Kralicky Sneznık mountains at 1275 m asl in the northwestern corner of Moravia, near the border between the Czech Republic and Poland (Photo 3.7). It drains an area of 27 267 km2. In the lower section, the river forms the border between the Czech Republic and Slovakia and between Austria and Slovakia. The Morava enters the Danube near Bratislava at Devın. The Thaya River (in German) or Dyje (in Czech), forming the border between lower Austria and Moravia, is by far the largest tributary of the Morava River (area: 13 400 km2, length: 305 km, discharge at mouth: 43 m3/s). Brno, an industrial and trade town (390 000 inhabitants), and the historic town of Olomouc (160 000 inhabitants) are the main cities in the basin. The Morava River basin has a human population of 3.5 million. The Morava forms an important natural corridor in Central Europe, allowing migrations of both animals and humans between the Danube valley and the northern European Plains. As such, it has a long history of human occupation and influence. The village Stillfried, along the Austrian Morava,

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PHOTO 3.7 Morava River in the protected area Osypane brehy (Broken Down Banks) near the city of Straznice in the Czech Republic. (Photo: Jirı Wenzl, Czech Republic).

has been occupied by humans for 30 000 years. Agriculture expanded into the area 7000 years ago and the first fortified settlements were founded during the Neolithicum. Since the 8th century BC, the area has seen a continuous turnover of tribes and cultures: Celts, Marcomanns, Quads, other German tribes and Slavs, among many others.

3.9.2.1 Geomorphology The Morava is a lowland river with an average slope of 1.8‰ that enters the Upper Danube (slope: 4‰ at the confluence). Plains cover 51% of the basin, highlands 35% and mountains 7%. The upper valley belongs to the Western Carpathians and is predominantly montane pasture. The basin geology mainly consists of crystalline bedrock (Bohemian Massif) and flysch. The lower Morava traverses the Neogene sedimentary Vienna Basin. Fluvisols predominate along alluvial sections of the Morava.

reservoirs within the Dyje River basin (total storage capacity: 540 million m3), whereas only few reservoirs exist along the tributaries of the Morava (total storage capacity: 56 million m3). Due to a highly developed industry and agriculture in the Czech part, rivers of the basin serve as recipients of both urban and industrial wastewater effluents. Today, >80% of the human population is connected to wastewater treatment plants. Agriculture is the largest source of nutrients and contributes >65% of the total nitrogen load and 30% of the total nutrient load in the river. During low flows, this imposes higher requirements on the quality of discharged wastewater and, consequently, the whole basin has been declared a sensitive area. Nevertheless, water quality in the Morava has improved during the past decades. Once it was one of the most polluted tributaries along the Danube with oxygen concentrations frequently dropping to <1 mg/L and fish kills often occurring.

3.9.2.2 Climate, Hydrology and Biogeochemistry The Morava River basin has a temperate continental (upper basin) climate with a pannonian influence in the lower section. Average annual temperature is 8.1 C. The average annual precipitation in the Czech part of the basin is 635 mm, with up to 1200 mm in the mountainous parts. The average annual discharge at the mouth is 110 m3/s. Flow peaks in early spring (March/April) and can last for weeks to even months. In the downstream section, a second flooding period occurs in early summer when the Danube River impounds back into the lower Morava (up to 35 km). The Vranov reservoir (length: 39 km, depth: up to >50 m), at the Czech-Austrian border, is the largest out of >20

3.9.2.3 Biodiversity The Morava floodplains are among the most diverse ecosystems in Europe. With an estimated 12 000 animal and plant species, it ranks 2nd after the Danube delta. In the Slovakian floodplains, 118 nesting bird species, 48 fish species (out of 52 for the entire basin, Lusk et al. 2004) and 850 higher plant species have been recorded. Hohausova & Jurajda (1997) identified 22 fish species from the upper river. Gobio obtusirostris, Barbatula barbatula and Carassius carassius were the most common species. In the lower section, Abramis brama and Alburnus alburnus dominate assemblages (Umweltbundesamt 1999).

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However, seven fish species are non-native and 5 species have disappeared in the basin. Beran (2000) found 43 species of aquatic mollusca (28 gastropods, 15 bivalves) in the Litovelske Pomaravı Reserve, near Olomouc, including endangered species such as Anisus vorticulus and Spaerium rivicola. Hasler et al. (2007) recorded 542 phytoplankton species along the Morava and Dyje Rivers. In the lower Morava, both cold- and warm-water adapted species co-occur because of the bimodal flooding regime from the Morava and Danube Rivers. For example, 12 out of 16 large branchiopods (Anastraca, Notostraca, Chonchostraca) known for Austria occur in this area, making it an international priority area for these ‘living fossils’ (Eder et al. 1997). During inundation, floodplains are used by several fish species for spawning and feeding grounds (Reimer 1991). During the dry phase, these wetlands are colonized by a diverse terrestrial arthropod community, many of them listed as endangered (Zulka 1991).

3.9.2.4 Human Impacts and Management Downstream of Litovel, the river has been regulated from the 1930s to 1960s. Along the lower Morava, 17 meanders have been cut off, the length of the mainstem has been shortened by 11 km (14% of this section), and the slope has increased from 0.15 to 0.19‰. Lateral embankments have led to a reduction in the inundation area by 80%. Similarly, the Dyje River has been channelized during the 1970s and the natural flooding regime was lost because of upstream flow regulation.

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The central Morava, near Olomouc, has maintained its natural character for considerable stretches. An important floodplain area is the Litovelske Pomaravı Landscape Reserve, which covers an area of 9600 ha (57% forests, 36% periodically wet fields, 7% permanent wet fields) (Kostkan & Lehky 1997). A transboundary national park has been established along the Dyje River, and floodplains along the lower Morava are protected by the Ramsar Convention. Recently, major plans exist to reconnect meanders along the Morava. The Morava floodplains contain the largest semi-natural alluvial meadows in Central Europe (in Slovakia: 20 000 ha; Cnidion vegetation type predominates) (Ruzickova et al. 2004). These wetlands are under threat by land use change, flow modification, recreational fishery and gravel mining. Several important measures have already been implemented to improve the situation: rehabilitating watercourses, increasing protection of existing waterbodies and wetlands, and terminating unfavourable agricultural practices (http://www.icpdr. org/icpdr-pages/czech_republic.htm).

3.9.3. V ah River The 378 km (360–410 km, depending on source) long Vah River (Hungarian V ag/W agh, German Waag, Polish Wag) is a left-side tributary of the Danube that flows entirely in Slovakia (Photo 3.8). It drains an area of 19 660 km2 (38% of the total territory of Slovakia). The largest cities in the basin are Nitra, Zilina, Trencın, Povazska Bystrica and Komarno (Komarom) (86 000, 85 000, 57 000, 42 000 and 36 000 inhabitants, respectively). PHOTO 3.8 Vah River (abstraction channel and old riverbed) from Povazsky hrad castle 50 km north of Trencin. (Photo: Jan Hanusin, Slovakia).

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3.9.3.1 Geomorphology The Vah rises in the Carpathian Mountains as the Cierny Vah beneath the Kralova hola peak in the lower Tatra Mountains (1948 m asl) and as the Biely Vah beneath Kriva n peak in the higher Tatra Mountains (2026 m asl). The catchment is characterised by long and narrow river valleys. The Vah and its tributary Orava flow partially through the Pieniny Klippen Belt (PKB). The PKB is composed of several layers of limestone covering a time-span from Early Jurassic to Paleogenic (Oszczypko et al. 2004). It represents the topographic contact zone of the External Western (Flysch) and the Central Western Carpathians. The Central Western Carpathians consist of Alpine crustal-scale basement and cover sheets (Tatric, Veporic and Gemeric superunits, comprising preAlpine amphibolite to greenschist facies basement, granitoids and Late-Paleozoic and Mesozoic sedimentary cover sequences) topped by several superficial nappes (Faryad 1999; Plasienka 2001; Kovac et al. 2002). Along its course, the Vah takes up 11 large tributaries before it enters the Danube in the Western Hungarian Plain (Danube Rkm 1766): Rev uca, Turiec, Rajcanka and Nitra Rivers from the left and Biely Vah, Bela, Orava, Kysuca, Biela voda, Vlara and Mal y Dunaj Rivers from the right (Banas et al. 1996). The Nitra is the largest tributary (catchment area: 4084 km2) and drains Central Slovakia. The Nitra meets the Vah twice, via a channel some 30 km before and within its natural riverbed at the confluence of the Vah with the Danube. The Mal y Dunaj (Small Danube) is a former natural branch of the Danube that separates from the Danube downstream of Bratislava. In the first 15 km, it flows in an artificial channel, and undulates for 120 km parallel to the Danube before it enters the Vah at Kolarovo (25 km upstream of the Vah–Danube confluence). The Small Danube contains numerous vegetated islands. Together with the y ostrov (‘Rye Danube main channel, it forms the area Zitn Island’) that spans 1890 km2 and is an important agricultural and drinking water abstraction region.

3.9.3.2 Climate, Hydrology and Biogeochemistry The Vah River basin ranges from cold mountainous to warm dry climates with moderate winters. Long-term average annual air temperature varies from 0 to 9 C. Long-term average annual precipitation in the upper Vah is 2000 mm and decreases to 550–600 mm in the lower Vah (WFD Report 2004). Average discharge of the Vah, including Nitra and Mal y Dunaj tributaries, is 138 km2 (ICPDR 2007b), and peak discharge (1% probability of occurrence) is 2000 m3/s (ICPDR 2004). Due to some storage lakes in the Tatra Mountains, the Vah has a flashy flow regime (maximum discharge range is 62:1; SAZP 2000). Discharge peaks in March and April during snowmelt, while minimum discharge occurs at the end of summer, in autumn and in winter. The most important industrial areas in Slovakia are in the Vah and Nitra valleys (predominantly machine, food and

chemical industries). In addition, the Nitra basin is an important agricultural region. The average annual BOD5 at the mouth of the Vah has decreased by 50% between 1985 and 1998 to about 2.8 mg O2/L). Similarly, NH4–N emissions from wastewater treatment plants have decreased from 1990 onwards (SAZP 1997, 2003), but the lower Vah and Nitra are still seriously polluted. Average phosphorus values range between 0.24 and 0.26 mg/L and NH4–N averages 0.63 mg/L at the mouth of the Vah. The Nitra is classified as very polluted to extremely polluted (SAZP 2003), and chlorobenzenes and chloroform are reported to occur (DPRP 1998). At only 10.4%, the municipalities in the Nitra region have the lowest connection to wastewater sewage systems throughout Slovakia (OPBI 2003), and point sources account for about 2/3 of the total organic matter, phosphorus and nitrogen emissions to the river. Diffuse inputs from agriculture are less significant despite being an important land use (IIASA 1996), and there are some local effects from using chromium (Cr3+) contaminated sludge as fertilizer (DPRP 1998).

3.9.3.3 Biodiversity Information about aquatic biodiversity of the river is mostly absent. However, the upper tributaries Turiec (66-km long, catchment area: 934 km2), Bela (22-km long, catchment area: 244 km2) and Orava (60-km long, catchment area: 1992 km2) have been intensively studied during the past decades (Ertl 1983; Krno et al. 1996; Ramsar 1998; Ramsar 2006). Channel conditions, the hydrological regime and vegetation of the Turiec are near-natural. Adjacent wetlands have been designated as a Ramsar site in 1998, and were even enlarged in area in 2006 (area: 750 ha) (Ramsar 2006). The wetlands contain a large number of rare or endangered plants, including Sesleria uliginosa and the orchid Dactylorhiza maculata transsilvanica. The site is also important for algae, fungi and mosses, as well as for 170 bird species (e.g., the yellow wagtail Motacilla flava) and mammals such as the Eurasian otter Lutra lutra and the Northern birch mouse Sicista betulina. Benthic communities of the Turiec basin were studied from 1986 to 1990 (Krno et al. 1996). In total, 616 benthic invertebrate taxa have been recorded (442 macroinvertebrates), including 40 for Oligochaeta, 7 for Hirudinea, 54 for Ephemeroptera, 64 for Plecoptera (i.e., 2/3 of the stonefly fauna of Slovakia), 62 for Trichoptera, 48 for Coleoptera, 102 for Chironomidae, and 58 for other Diptera (excluding Chironomidae and Simuliidae) – among them are 54 species not found elsewhere in Slovakia. The Turiec and its tributaries support important populations of indigenous lamprey (Eudontomyzon vladykovi) and native fishes such as Hucho hucho, Thymallus thymallus, Cobitis elongatiodes, Alburnoides bipunctatus, Chondrostoma nasus, Leuciscus leuciscus, Lota lota, Phoxinus phoxinus, Cottus gobio, Cottus poecilopus and Zingel streber. For the Bela River, 14 Oligochaeta species, 28 Ephemeroptera species, 58 Plecoptera

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species, 56 Chironomidae species and 12 fish species (brown trout, rainbow trout and grayling are the most important species) have been recorded (Ertl 1983). The Orava River exhibits a near-natural state. Large forested peatlands, meadows, lakes, marshes, swamp forests and open bogs occur in the basin. This area contains a rich terrestrial fauna and flora. For example, 37 fish species have been recorded, including Phoxinus phoxinus, Cobitis elongatiodes, Lota lota, Hucho hucho and the Ukrainian brook lamprey Eudontomyzon vladykovi (Ramsar 1998). All four Newt species of Slovakia occur in the Orava basin (Triturus alpestris, T. cristatus, Lissotriton vulgaris, L. montandoni). The Orava is along a major bird migration route, including species of rare migratory species such as white-tailed eagles (Haliaeetus albicilla), fish eagles/osprey (Pandion haliaetus), black tailed godwits (Limosa limosa), black-throated divers (Gavia arctica), long tailed ducks (Clangula hyemalis), great egret (Casmerodius albus) and Eurasian cranes (Grus grus). Black storks (Ciconia nigra), common kingfisher (Alcedo atthis), common tern (Sterna hirundo), blackheaded gull (Larus ridibundus), common redshank (Tringa totanus) and yellow wagtail (Motacilla flava) breed within the basin. There are good populations of the Eurasian otter (Lutra lutra) and water shrews (Neomys fodiens and Neomys anomalus) and in 1995 the European beaver (Castor fiber) was reintroduced into the tributary Jeles na. The mouse Alces alces and the bat Myotis daubentoni also have viable populations. Since 1998, the Orava River and its tributaries have been designated as a Ramsar site (Ramsar 1998).

3.9.3.4 Human Impacts and Management Twelve major dams (>15 m) are located along the mainstem of the Vah (17 in the whole basin, Table 3.1). Hydroelectric development on the Vah and its tributaries (Orava River, in particular) accounts for 48% of Slovakia’s hydroelectric power potential. The most important hydropower plants are Cierny Vah in the upper Vah and Liptovska Mara forming the Besenova reservoir (Rkm 336–345; total storage capacity is 360 million m3). The nuclear power plant ‘Bohunice’, which uses river water for cooling, is in the lower Vah. To protect the middle and lower sections against floods, the building of dams commenced in the 1930s and intensified in the 1950s onwards. Today, the Vah and Nitra are regulated along 60-80% of their total length (ICPDR 2007b). Reservoirs on the Vah effectively reduce peak discharges of extreme floods through temporal storage/retention. However, during concomitant floods on the Danube and Vah, the discharge of the Vah escalates flood conditions in the Danube (ICPDR 2004). In former times, timber floating and rafting of mining products from central Slovakia were common on the Vah. Today, commercial navigation is restricted to the lower Nitra and lower Vah (for 74 km, up to the city of Sered) and mainly during higher water levels. Proposals exist (Project ‘Vah waterway’) to make the Vah (European

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waterway E81) navigable up to Zilina (Rkm 242) and to eventually connect it with the Odra River (via the Kysuca River and various canals) and thus to the Baltic Sea (UNECE 2006). These plans would allow convoys carrying up to 6000 tons and a 22.8 m beam, and require the construction of new locks and the reconfiguration of existing ones.

3.9.4. Drava River The 719-km long Drava River (German: Drau, Hungarian: Dr ava, Slovenian, Croatian: Drava, Latin: Dravus) drains an area of 40 087 km2. It is the 4th largest and 4th longest Danube tributary, and is shared by Italy, Austria, Slovenia, Croatia and Hungary. Its main tributaries are the Isel, M€ oll, Lieser and Gurk Rivers in Austria, as well as the Mura (German: Mur) River that joins the Drava River at the Croatian-Hungarian border. The Drava enters the Danube east of Osijek (Rkm 1382), and the basin is inhabited by 3,6 million people (Schwarz 2007). About 30% of the basin is agricultural area and 46% is forested (Table 3.1). Graz, Osijek and Maribor are the largest cities (253 000, 121 000 and 116 000 inhabitants, respectively). Navigation is restricted to the lower Drava (20% of its total length).

3.9.4.1 Geomorphology The Drava originates in the Southern Alps in Italy near Dobbiaco (Toblach) on the Austrian border at about 1200 m asl. Within its first few kilometres, the Drava drops 400 meters in altitude. After entering Austria, it flows eastwards through Eastern Tyrol (Tirol) and Carinthia (K€arnten), thereby separating the central Alps from the limestone Alps. The Drava basin (Drautal) is the longest longitudinal valley in the entire Alps. Downstream of the city of Lavam€ und, the Drava flows through northeast Slovenia, there the city of Maribor, and enters Croatia. Upstream of its confluence with the Mura, 23 hydropower plants are in operation along the mainstem (12 in Austria, 8 in Slovenia and 3 in Croatia). Along the Mura, 26 hydropower dams have been built (Reeder et al. 2006). Downstream of the confluence, the Drava is a typical lowland river and unsuitable for effective hydropower production. Here, the Drava forms the border between Hungary and Croatia (for 145 km) before again entering Croatia and finally joining the Danube at 80 m asl (Rkm 1382). The lower Mura and Drava constitute a 380 km free-flowing and relatively natural watercourse. The confluence area of the Drava and Danube forms the internationally important Kopacki Rit Nature Park (Photo 3.9). The Drava crosses several ecoregions ranging from high Alpine mountains (Grossglockner is the highest peak at 3800 m asl), Alpine basins, a Piedmont section, to finally the Pannonian-Illyrian plain. The river changes longitudinally from a straight to a braided and then to a meandering channel. In the lower reaches, sand and gravel bars as well as vegetated

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Chapter | 3 The Danube River Basin

PHOTO 3.9 Nature Park Kopacki Rit in Croatia. (Photo: Christian Baumgartner, Austria).

islands are still abundant (Schwarz 2007). The Drava basin consists of two terraces and a recent floodplain. The terrace sediments were deposited during the Upper Pleistocene and Holocene and consist of gravel and sands (Halamic et al. 2003), and its course follows geological basin fracture lines (e.g. high banks in Hungary) (Schwarz 2007). The southern Drava basin (and the Drava ‘Graben’) forms the Drava–Sava interfluve, the southwestern edge of the Carpathian region north of the area of the Dinarids (F€ oldvary 1988).

3.9.4.2 Climate, Hydrology and Biogeochemistry The Drava basin has a mild-continental and partly humid climate with an average annual temperature of 10.9 C and an average rainfall of 600–750 mm/year. The Drava River has a glacial-nival flow regime with lowest flow in January and February and highest flow in May and June (Alpine snowmelt period). A second flow peak occurs in late autumn due to precipitation maxima in the Southern Alps (Mediterranean influence in the middle and lower course). Due to high precipitation rates in the upper basin, the Drava exhibits a high flood risk in the upper reach. Today, the construction of dams, reservoirs and lateral levees prevent the flooding of former floodplains. The downstream section, the Kopacki Rit Nature Park area in particular, experiences long-lasting (100 days of the year) floods. The natural water level fluctuation ranges between 5 and 6 meters in this lower section. Average discharge of the Drava is 541 m3/s, and peak discharge (1% probability) is 2573 m3/s (ICPDR 2004). The Danube–Drava National Park in southwest Hungary is strongly influenced by the high natural water level fluctua-

tions that are increased by hydropower peaking. Thus, the water level of the Drava near the dam fluctuates by about 1– 1.5 m several times a day. Oscillations of a few centimetres are still observed in even Osijek, near the Drava–Danube confluence (Schwarz & Bloesch 2004). The hydromorphology also is affected by reduced sediment transport, canalization of the river course and sediment excavation, which lead to an incision of the riverbed by 2.5 cm/year. Erosion accounts for a large share of the phosphorus load (1479 tons/year in 2004) of the Drava to the Danube (6% of the total load of the Danube). The nitrogen load of the Drava was 35 688 tons/year in 2004 (8% of the total load of the Danube) (Behrendt 2008). Many cities (e.g. Osijek) and industrial areas discharge untreated wastewater into the Drava (Schwarz 2007). The heavy metal content in the topsoil of alluvial deposits exhibit elevated values of arsenic (As: mean value 12 mg/kg) and mercury (Hg: mean value 77 mg/kg) for the Croatian Drava. Elevated values of As and Hg are mostly a result of intense agricultural practices, fossil fuel combustion and traffic in urban areas. Elevated values for lead, zinc and cadmium (mean values for Pb: 76 mg/kg, Zn: 194 mg/kg, Cd: 0.8 mg/kg) are most likely due to former mining, smelting and floatation activities in the Slovenian and Austrian sections of the river (Halamic et al. 2003).

3.9.4.3 Biodiversity The WWF-DCP Drava Inventory Project (Reeder et al. 2006) recorded 66 aquatic macrophytes in the Drava basin. In addition, 54 Odonata species, 27 amphibian and reptile

92

species and 67 mammal species were recorded (SchneiderJacoby 1994). In the Hungarian part of the Drava River, 113 caddisfly species were recorded, among them the strictly protected Platyphylax frauenfeldi which has locally stable populations (Uherkovich & N ogradi 2005). A total of 63 fish species have been registered for the Drava basin (Sallai & Mrakovcic 2007). Most fishes are reophilic such as the abundant Chondrostoma nasus, Alburnoides bipunctatus and Barbus barbus. Other rheophilic species are less abundant and protected, including Rutilus virgo, Romanogobio uranoscopus and Zingel zingel. Eurytopic fish like Alburnus alburnus, Rutilus rutilus and Carassius gibelio also were reported. In oxbows and backwaters, stagnophilic fish like Scardinius erythophtalmus, Tinca tinca and Carassius carassius occur (Sallai 2002, 2003). About 14 fish species have been introduced, of which the Prussian carp (C. gibelio) and Grass carp (Ctenopharyngodon idella) cause major impacts to native fauna. Nine species in the basin are endemic (Rutilus virgo, Romanogobio uranoscopus, R. kessleri, Hucho hucho, Umbra krameri, Gymnocephalus baloni, Gymnocephalus schraetser, Zingel zingel and Zingel streber). A total of 24 species are protected and five fish species are listed as (critically) endangered (Eudontomyzon vladykovi, Hucho hucho, Umbra krameri, Zingel zingel and Z. streber) (Sallai 2002, 2003). Four species, all sturgeons, are regionally extinct. A total of 291 bird species are reported, 25% are listed as protected and include the little tern (Sternula albifrons, http://www.sterna-albifrons.net). It has been a characteristic breeding bird of the Drava in Slovenia, Croatia and Hungary, but has become nearly extinct due to the loss of gravel and sand banks as a consequence of hydropower dam construction in the 1970s and 1980s. Only 15 pairs remain in the lower free-flowing course of the Drava. The common tern (Sterna hirundo), common sandpiper (Actitis hypoleucos) and the little ringed plover (Charadius dubius) require similar habitats. Seventy-nine colonies of sand martins (Riparia riparia riparia) and 36 colonies of bee-eaters (Merops apiaster) found along the free-flowing Drava indicate active lateral erosion (Reeder et al. 2006).

3.9.4.4 Human Impacts and Management Numerous groundwater well-fields for public water supply and hydro-technical melioration systems have been built in the Drava River basin. Human activities, which are often weakly controlled and poorly coordinated, have resulted in significant changes in the hydrological regime of the river. The Drava was regulated and dammed during the past century with a few semi-natural sections remaining in the lower part. In the upper part, intermittent hydropower generation (hydropeaking) causes major water level changes and impacts the aquatic fauna. In the Austrian part, a reduction of 50% of the fish stock and 80% of the benthic invertebrate community has been attributed to hydropeaking operations in the M€ oll and Malta tributaries (ICPDR 2005).

PART | I Rivers of Europe

The lower Drava in Hungary has been protected as a National Park since 1991. In 2007, the lower section of the Mura was designated as a protected landscape, and Croatia has recently (March 2008) decided to establish the Regional Park Drava (total area: 1500 km2). Its aim is to achieve transboundary protection status to allow for the implementation of joint monitoring programs, and to have this area included into the UNSECO Man and Biosphere (MAB) reserve network (Schneider-Jacoby 1996; SIFNP 2005). However, the park management is faced with a strong lobby of hydropower and navigation stakeholders.

3.9.5. Tisza River The Tisza River (German: Theiß, Romanian, Slovakian, Serbian: Tisa, Ukrainian: Tysa) is in the geographic centre of Europe and drains parts of five countries (Ukraine, Romania, Slovakia, Hungary and Serbia) (Photo 3.10). It is the longest (965 km) tributary with the largest catchment (catchment area: 156 087 km2 (Table 3.1)) in the Danube basin. Mean annual discharge is 792 m3/s, and it contributes 13% to the total runoff of the Danube. The Tisza basin is home to 14 million people, and is mainly used for agriculture and grazing. Arable land covers 48% and forests cover 30% of the basin, mainly restricted to the north and east. Forestry is an important economic sector in the upper basin, particularly in Ukraine and Romania (ICPDR 2008). The largest cities in the basin are Cluj-Napoca, Timisoara and Kosice (320 000, 300 000 and 235 000 inhabitants, respectively). Some 3% of the basin is under legal protection.

3.9.5.1 Geomorphology The basin is fringed by the ridges of the Carpathian Mountains (highest peaks in the Rodna Mountains at 2300 m asl and in the Retezat Mountains, Mures sub-basin at 2506 m asl) in the northwest to southeast. The eastern catchment is partly in the Transylvanian basin. The Tisza River network can be divided into three main parts: The mountainous upper Tisza extends to the confluence with the Szamos/ Sume¸s. The two headwaters, the Black and the White Tisza, originate in the Ukrainian Carpathian Mountains at 1700 m asl. The slope in this section is 20–50‰. As a wild mountain river, the Tisza flows west through a sequence of alluvial and constrained sections, partly forming the Ukrainian-Romanian border. In this section, it receives the Viso/Vi¸seu and Iza tributaries, and the river changes to a braided style with numerous vegetated islands and extensive gravel areas. The slope declines to about 2‰. Before it enters the Hungarian Plain, the Tisza receives the Tarac/Tereszva, Talabor/Tereblja, Nagyag/Rika, Borsa/Borszava and T ur (in Hungary) tributaries. The channel changes from a gravel-bed to a sand-bed river. Along the first 260 km, from the source to the confluence with the Szamos/Sume¸s, the Tisza has already dropped by 1600 m in elevation.

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Chapter | 3 The Danube River Basin

PHOTO 3.10 Tisza River in Ukraine at the Khust Gate. (Photo: Alexei Iarochevitch, Ukraine).

The middle Tisza extends to the confluence with the Mure¸s/Maros River which features an outstanding nearnatural hydromorphology (Sandu & Bloesch 2008). The Bodrog and Saj o/Slana Rivers are the largest tributaries in this section, and their catchments are in the Slovakian and Ukrainian Carpathian Mountains. The other large tributaries K€ or€ os/Cri¸sul and Maros/Mure¸s drain parts of Transylvania in Romania. The smallest tributary of the middle Tisza is the Zagyva, which drains the Matra and Cserhat Mountains in northern Hungary. In the middle Tisza, the slope is about 0.09‰. In the upper Hungarian plain, the Tisza forms a great northward loop (the ‘Zahony bend’) towards the Slovak-Hungarian border (Timar et al. 2005). The middle Tisza channel has an average width of 200 m, and the silt and clay proportion increases due to the fast loss in sediment transport capacity (average slope: 0.025‰). The section downstream of the mouth of the Maros/ Mure¸s River forms the lower Tisza. In this section, the Tisza receives the Bega/Begej, the Aranka and numerous smaller tributaries via the Danube–Tisza–Danube Canal System. The Tisza finally enters the Danube River in central Vojvodina, Serbia. In the Great Hungarian Plain, the Tisza is a typical lowland river with a meandering planform. The proportion of mountain areas in the Tisza catchment is about 1%, the area below 200 m is 46% (Szab o 2007; Zsuffa 2002). The Tisza is, together with the Inn River, the greatest supplier of loess sediments to the Danube. The loess is mainly composed of quartz silt and primarily originates from weathering of flysch bedrock in the Carpathian Mountains and aeolian loess that is derived from fringing floodplains (Smalley & Leach 1978).

3.9.5.2 Climate, Hydrology, Biogeochemistry The Tisza basin exhibits a temperate continental climate. Mean annual temperature is 6–9 C in the mountainous sections, 8–9 C in the Transylvanian basin, and 10–11 C in the lowland catchment. Seasonal temperature ranges from 32 to 41 C (Szabo 2007). Overall, the Tisza drains a relatively dry area. While precipitation exceeds 1700 mm in the high Carpathian Mountains (the Maramaros Alps), it decreases to <500 mm in the Great Hungarian Plain (Zsuffa 2002). Due to predominant northwest winds, the southeast slopes of mountains and basins behind are particularly dry (i.e., Zagyva catchment and the area east of the Bihar Mountains, where the K€or€os and Maros River catchments meet). About 25% of the annual precipitation falls in May/June, followed by dry summers. A second peak of precipitation occurs in October/November. The Tisza exhibits a nival–pluvial flow regime with highest discharge in March/April and low flows in summer and early autumn. Discharge decreases rapidly at the end of the snowmelt period. Mean annual discharge at the mouth is 792 m3/s (Tables 3.1 and 3.2) with a maximum of 3730 m3/s and a minimum of 80 m3/s. The Tisza and, in particular, tributaries such as the Bodrog and K€or€ os, exhibit flashy flow regimes because of the lack of natural lakes functioning as retention basins, the predominance of fine soils, and deforestation in the headwaters. During the past 30 years, the river has experienced >100 major floods. The rate of occurrence and the magnitude of floods have shown an increasing trend, most likely in line with global warming. In 1998 and 2001, two devastating floods occurred in the Tisza basin (Szabo 2007).

94

There is a lack of municipal wastewater treatment facilities throughout the basin; in some areas <50% of the urban population is connected to the public sewerage system. Septic tanks are common. As a result, raw or only partially treated sewage is released into tributaries and the Tisza itself. Moreover, runoff from stockyards and animal wastes increase the organic load and microbial contamination in recipient waters. In 2004, the Tisza basin contributed 72 330 tons N (16%) and 4340 tons P (19%) to the total load of the Danube River (Behrendt 2008). Throughout the basin, the legal limits for nitrate concentrations in groundwater are often exceeded. Major contamination of surface and ground waters by heavy metals (i.e., copper, iron, manganese, zinc, lead, cadmium) and other toxic substances such as cyanide from inadequately treated industrial discharges from mining and metal processing industries is prevalent in the upper basin. The Maramures mining region in Romania is the main risk spot in the basin. Recent major accidental spills in the basin have been the Baia Mare cyanide and heavy metal spill in January 2000 (release of about 100 000 m3 wastewater containing up to 120 tons of cyanide within 11 h), the Baia Borsa heavy metal spill in March 2000 (release of 100 000 m3 sludge with about 20 000 tons of solid tailings containing elevated amounts of heavy metals), and the oil pipeline incident on the Latorica River in September 2003 (resulted in a 5-km slick of oil).

3.9.5.3 Biodiversity The Baia Mare spill (see above) reached the Black Sea through downstream neighbouring countries within two months and caused a massive fish kill. Recovery was fast and after 1 year fish biomass was almost as high as before the accident. More than 95% of the killed fish belonged to non-native species Ctenopharyngodon idella (Chinese grass carp). In this respect, the disaster could be regarded as an ecological benefit for the indigenous fauna if the exotic carps would not have been restocked. There are still chronic consequences due to the accumulation of heavy metals in deposited sediments with potential long-term effects on biota and humans. The Tisza River shows a high biodiversity, higher than most Western European rivers, mainly due to extensive natural or semi-natural floodplains along the mainstem and tributaries (>300 riparian wetlands are found in the catchment). Moreover, the Carpathian Mountains remain relatively unaffected from intensive agriculture and forestry. Thus, large carnivores including the brown bear (Ursus arctos), lynx (Lynx lynx), wolf (Canis lupus) and otter (Lutra lutra) are still abundant. About 60% of the total European brown bear population lives in the Romanian part of the catchment. Many vulnerable, threatened and critically endangered species such as the Corn crake (Crex crex), Geoffroy‘s bat (Myotis emarginatus), European ground squirrel (Spermophilus citellus) and Russian sturgeon (Acipenser gueldenstaedtii) can be found.

PART | I Rivers of Europe

The basin also contains the mayfly Palingenia longicauda, the largest European mayfly that shows spectacular synchronized mass emergence events. This species has been abundant in the middle and lower sections of larger lowland rivers up to the beginning of the 20th century. It has disappeared from Western Europe and has undergone a serious decline in Central Europe. Today, this species is only reported for the Tisza and some tributaries (e.g., Szamos, K€or€os) (Tittizer et al. 2008). The upper Tisza Basin is an important migration route for fish, notably nase (Chondrostoma nasus), barbel (Barbus barbus) and sterlet (Acipenser ruthenus). This river stretch supports a rich dragonfly fauna as well as many nesting water birds, including all 8 European herons (Ardea cinerea, A. purpurea, Ixobrychus minutus, Botaurus stellaris, Egretta garzetta, Nycticorax nycticorax, Ardeola ralloides and Bubulcus ibis).

3.9.5.4 Human Impacts and Management The present geomorphology and hydrology of the Tisza are the result of major human interventions, mainly between 1845 and 1910. The former extensive floodplains were drained or embanked to enable constant agricultural and industrial practices as well as to aid navigation and transport. Concurrently, the mainstem of the Tisza was shortened by 30–40%, while the channel slope increased from 0.02–0.04 to 0.04–0.08‰ in the Great Hungarian Plain (Laszl offy 1982). Today, <1000 km2 of the former 25 900 km2 floodplains in the Hungarian Tisza basin remain, corresponding to a total reduction of 96% (UNEP 2004). In Hungary, 500 000 people, or 5% of the country’s population, inhabit land reclaimed from the Tisza (ICPDR 2008). A total of 167 larger and numerous small oxbow lakes are now disconnected, except during major floods. In the lowland section, the river traverses a 1400–1800 m wide corridor fringed by lateral embankments, and the riverbed is 200 m wide (Szabo 2007). As a consequence of intense regulation and exploitation, the groundwater table along the Tisza has decreased, salinisation has increased, and soil-incrustination in the western area is prevalent. Following the strong droughts in the 1930s, construction of lowland reservoirs began in the K€or€os/Cri¸sul River. Moreover, two large irrigation channels (98 and 70 km long, 10–30 m wide and 3–4 m deep) that branch off of the Tisza in northern Hungary were finished in the late 1950s. These channels have considerably enlarged the agricultural area and dampen floods. Due to their high water quality, they supply the second largest Hungarian city Debrecen as well as smaller cities with drinking water. These channels provide habitats for about 42 fish species. Today, more than 60 reservoirs exist in the basin with a ore Restotal reservoir capacity of 2.7 billion m3. The Kisk€ ervoir (finished in 1974), so-called ‘Lake Tisza’, is the largest artificial lake in Hungary with a storage volume of about 106 million m3. It provides recreational facilities and acts as a nature conservation site. A total of 37 hydropower stations

Chapter | 3 The Danube River Basin

(35 with an installed capacity >10 MW) have been built in the basin. The Tisza is used for 70% of its length, up to the Ukrainian border, for navigation (ICPDR 2008). However, the Tisza has lost its importance as a shipping route due to the decline in production and export of agricultural goods and building materials in Hungary. The water level of the Tisza still undergoes large fluctuations with low water levels of only 20–30 cm in fords along free-flowing sections between Kisk€ ore and Csongrad during summer. Existing locks do not allow the passage of large vessels and the Tisza does not belong to the EU waterways of importance (Marton 2008). Some tributaries are navigable on shorter sections: Bodrog (Hungarian stretch and 15 km into Slovakia), Mure¸s (25 km, corresponding to <5% of its total length), K€ or€ os (115 km in Hungary) and Bega (117 km in Romania, Serbia and Montenegro, >48% of the total river length). Land use changes in the upper Tisza catchment have increased runoff, soil erosion and diffuse nutrient inputs. As a consequence, floods, landslides and droughts (particularly in Hungary and Serbia) are more common today (ICPDR 2008). Efforts to reduce flood impacts by constructing higher dykes and continued riverbed regulation have led to the siltation of the main riverbed, which has inadvertently increased flood risks. The projected total annual water demand for the Tisza basin in 2015 is estimated to be 1.5 billion m3, or about 6% of the total annual runoff. Irrigation also is predicted to increase in all Tisza basin countries, which will add pressures on already threatened aquatic ecosystems; particularly during low water periods (ICPDR 2008). In Slovakia, major conservation areas exist along the Slana River (50 000 ha) and a wetland is found along the Latorica River (10 000 ha). In Romania and Ukraine, protected areas total 195 000 ha. Along the middle and lower Tisza, five national parks (total area: 935 000 ha) and several protected areas exist.

3.9.6. Sava River The 945-km long Sava River (Save in German, Sz ava in Hungarian) is the largest tributary of the Danube by volume (average discharge: 1572 m3/s) and the second largest, after the Tisza, by catchment area (95 793 km2). Today, the Sava basin is an international basin: 40% is in Bosnia and Herzegovina, 26% in Croatia, 15.4% in Serbia, 11% in Slovenia, 7.5% in Montenegro and 0.1% in Albania. Several tributaries such as the Kolpa/Kupa, Una and Drina Rivers cross international boundaries. About 8.8 million people live in the basin. Belgrade, Zagreb, Sarajevo, Ljubljana and Banja Luka are the largest cities (1.6 million, 780 000, 304 000, 280 000 and 225 000 inhabitants, respectively). Some 37% of the basin is arable land, and 45% is forested (Table 3.1).

3.9.6.1 Geomorphology The Sava River is formed by the headwaters of the Dolinka Sava originating at the Italian-Slovenian border at 870 m asl

95

and the Bohinjka Sava from Lake Bohinj (Bohinjsko jezero) in the Julian Alps. In Slovenia, the Sava is a gravel-bed river with an average slope of >0.7‰. The Sava and its tributaries have carved deep gorges into the cretaceous limestone. Eocene flysch forms the bedrock in northwest Slovenia. In Croatia, downstream of Zagreb, the Sava meanders through a wide valley covered with fertile soils and fringed by wetlands (average slope: 0.04‰) (Brilly et al. 2000). The Sava passes by the valley of the Kupa River and for 311 km the Sava constitutes the border between Croatia and Bosnia and Herzegovina (from the confluence of the tributary Una almost to the confluence of the Drina). In Serbia, it remains a typical lowland river with a channel width of up to 1000 m before it enters the Danube in Belgrade (Rkm 1170). In the downstream section, alluvial sediments and igneous rocks with Neogene marls and shale prevail. The Sava drains the southeastern fringe of the Alps and the northeastern Dinaric Mountains as well as the southern Pannonian lowland (Pandzic & Trninic 1998). Although most of the catchment is in the Alps and Dinarids, the river traverses a wide lowland valley. Most major tributaries enter from the right side. About 25% of the basin is karstic. Caves and underground rivers are common in the upper basin (Brilly et al. 2000).

3.9.6.2 Climate, Hydrology and Biogeochemistry The Sava basin exhibits a mixture of Alpine and Mediterranean climates. Average annual air temperature is 9.2 C and average annual precipitation is 1000 mm. Maximum precipitation is 3800 mm in the Julian Alps and in the upper Kupa region (ICPDR 2004), and minimum precipitation is 600– 700 mm in the Pannonian Plain. The Sava has a nival-pluvial flow regime with a spring peak caused by snowmelt in the Alps and a second peak in autumn caused by heavy rainfall. The ratio of the highest to lowest monthly average discharge is 10:1 (Brilly et al. 2000). Average annual discharge of the river is 1572 m3/s at its mouth, with an annual peak discharge of 6400 m3/s (1% probability of occurrence, ICPDR 2004). The Drina River is the largest tributary with an average discharge of 370 m3/s (ICPDR 2004). The Sava contributes about 25% of the total Danube discharge (15% of the Danube basin). Together with the Tisza, the Sava dominates the discharge regime in the Lower Danube, causing two distinct seasonal maxima. The impounded section of the Iron Gate I and II dams extends 100 km upstream into the lower Sava (ICPDR 2005). Until the 1990s the Sava was affected by heavy pollution from metallurgical, chemical, leather, textile, food, cellulose and paper industries (Jovicic et al. 1989), as well as from agricultural activities (agrochemicals, pesticides and pollution from pig and poultry farms). These activities reduced during the war in the 1990s, but have been resumed since 2000. The Sava is the main recipient of wastewater from many cities, including Zagreb (Croatia) (Bosnir et al. 2003) and is impacted by polluted water of the tributaries

96

Kupa and Bosna as well as smaller tributaries in the Zagreb region (Brilly et al. 2000). Thermal pollution from conventional powerplants and a nuclear powerplant (Krsko in Slovenia) occurs along the Slovenian Sava sections. Today, the specific organic pollution in the basin is above Danube average (ICPDR 2005). The basin contributes 102 362 tons N (23% of the Danube basin) and 9829 tons P (43% of the Danube basin) to the total annual load of the Danube River (Behrendt 2008). In the lower Sava, the concentration of atrazine is 0.78 mg/L (ICPDR 2005). Downstream of the Sava confluence, the Danube exhibits elevated concentrations of Al, As, Cd, Cu, Fe, Mn, Ni and Zn.

3.9.6.3 Biodiversity For the Serbian river section, 62 macroinvertebrate species have been recorded (Paunovic et al. 2008). Molluscsa (Gastropoda: 12 species, Bivalvia: 11 species) and Oligochaeta (16 species) dominate assemblages, and the community structure indicates habitat degradation and organic pollution. Five non-native species are reported to occur. The bivalve Corbicula fluminea (Asian clam) and oligochaete Branchiura sowerbyi show high frequencies, while the bivalve Anodonta (Sinanodonta) woodiana exhibits high abundances (Paunovic et al. 2008). About 55 fish species, including the sterlet (Acipenser ruthenus), are found in the Sava River (Mrakovcic et al. 2006). The Nature Park ‘Lonjsko Polje’ in the middle Sava forms the largest remaining inundation area in the entire Danube basin (510 km2). There, floodplain waters contain at least 35 fish species. This area is an important spawning area for wild carp (Cyprinus carpio). Further, 43 dragonfly species have been identified during a seasonal survey. The Nature Park provides breeding habitats for 22 bird species of special conservation concern in Europe, among them are rare birds such as the ferruginous duck (Aythya nyroca), white tailed eagle (Haliaeetus albicilla) and corncrake (Crex crex) (SchneiderJacoby 1994).

3.9.6.4 Human Impacts and Management Major sections of the river still exhibit a relatively natural geomorphic structure and hydrological regime and are fringed by large protected wetlands. The mainstem is navigable for almost 600 km (from the mouth up to the city of Sisak, 60 km downstream of Zagreb) for small vessels and for 377 km (up to Slavonski Brod) for large vessels. In the 18th century, the river was an important transportation route for crops. During the communist era, the Sava became the main transportation and shipping route of former Yugoslavia. The mainstem has been canalised for flood protection only in a very few and short sections (e.g. in Zagreb). In the central basin only about 40% of the alluvial wetlands were converted into arable land or drained. Large parts of the city of Zagreb were built on the former floodplain. In the 1960s,

PART | I Rivers of Europe

the city expanded to the southern banks of the Sava and floods became an increasing threat. Regulation of high water by the central Posavina flood control system is carried out via three relief canals protecting the towns Zagreb (Odra Canal), Karlovac (Kupa-Kupa Canal) and Sisak (Lonja-Strug Canal), 15 distribution facilities and large alluvial retention areas for storage. This system has proven effective since its design in 1972, and the channels and facilities have been integrated into the existing limited flow river network. This is a system that, with the necessary retention and expansion areas in the lower central basin, and governed by the criteria established for the regulation of the water masses, ensures an unaltered water regime in the Mackovac exit control profile (maximum: 3000 m3/s) toward the lower Sava valley (Brundic et al. 2001). Only in the central basin around Zagreb 116 000 ha of floodplains have been preserved as retention areas and unique natural sites. Two Ramsar sites – Lonjsko Polje and Crna Mlaka - and three important bird areas – Sava Wetlands, Odransko Polje and the Pokupsko depression – form a unique blend of natural landscape elements and European riverine lowlands. Further, large retention areas and alluvial wetlands are situated on the left Sava bank in the Spacva–Bosut depression at the border with Serbia (Schneider-Jacoby 2005). Along the Serbian section, a former large inundation area is separated by a 771-km long flood control dike (Brilly et al. 2000). In Slovenia, four large and several small hydropower plants are in operation along the mainstem, and nine are planned or already under construction. A chain of hydropower reservoirs is planned to be built in the Croatian section upstream of Zagreb, and additional multi-purpose reservoirs are foreseen. In Bosnia and Herzegovina, 12 hydropower plants are in operation along mountainous tributaries, greatly reducing sediment transport. Sediment management remains a key issue in the entire basin. Increasing anthropogenic activities in the headwaters of the Sava and main tributaries, such as urbanisation, industrial development and agricultural monoculture, have increased the impact by organic, inorganic and hazardous pollutants. Bosnir et al. (2003) reported elevated mercury concentrations in fish caught in the Sava near Zagreb. The main economic industries in the basin are metal, chemical and food production as well as small family estates with extensive agriculture. During the dry season, water supply systems are sometimes unable to meet the water demands of consumers due to management and capacity problems. Today, most people are connected to the public water supply (e.g. 84% in Slovenia in 1991), but few are connected to wastewater treatment systems (e.g. 16% in Slovenia in 1991; negligible in Bosnia and Herzegovina) and urban sewage is directly discharged into the river. In Zagreb, a wastewater treatment plant has been in operation since late 2007, and another is planned for the Karlovac Province. In Serbia and Bosnia and Herzegovina, unprotected landfills along the river remain a permanent risk (http://www.inweb.gr/workshops/ sub_basins/1_sava.html). Industrial pollution (leather, paper,

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oil and food industries) and pollution from agriculture cause major transboundary challenges for some city water supplies (e.g. Zagreb and Belgrade). With its large alluvial wetlands and undisturbed lowland forests, the basin provides a major environmental resource. Four Ramsar sites have been designated: Cerknisko jezero (intermittent karstic lake, 7250 ha, Slovenia), Lonjsko Polje (500 ha, Croatia), Bardaca (3500 ha, Bosnia and Herzegovina) and Obedska Bara (30 000 ha, Serbia). The headwaters of the Sava are in Triglav National Park and Plitvice Lakes National Park (UNESCO World Heritage site since 1979), and Croatian tributaries are found along the Risnjak National Park. Numerous important hotspots of biodiversity and Natura 2000 sites exist in the basin. Currently, flood protection in most parts of the middle and lower basin relies on flood-protection dikes as well as on natural retention areas in some parts. In particular, the Nature Park Lonjsko Polje in Croatia serves as a natural retention area and is a good example of how to link flood control measures with the conservation of natural and cultural landscapes of national and international importance (ICPDR 2005). The Tourism Masterplan for the Posavina is proposing an intergrated development for the whole central basin (http://www.euronatur.org/fileadmin/docs/projekte/Save/ Save_bulletin_EN_KR.pdf). The Nature Park Lonjsko Polje is an outstanding place for tourism development for inland Croatia (Komatina & Groselj 2008). During the past two decades, pollution has decreased due to reduced industrial production and a weak economy. The riparian states of the Sava are presently in a post-war recovery period and pollution levels are slightly increasing (Brilly et al. 2000). The International Sava River Basin Commission (ISRBC) was established in late 2002 and held its constitutional session in mid 2005. The general objectives of the ISRBC are to strengthen transboundary cooperation for sustainable development of the region. Its specific goals are (i) the establishment of an international navigation regime along the Sava and its navigable tributaries, (ii) the implementation of a sustainable water management scheme and (iii) to undertake measures to reduce the risks of flooding, ice jams, droughts and pollution accidents (http://www.savacommission.org). The ISRBC works in close cooperation with the International Commission for the Protection of the Danube River (ICPDR). Currently the preparation of the Sava Basin Management Plan (in accordance with the EU WFD) and a Flood Risk Management Plan (in accordance with the EU Flood Directive) are under preparation (Komatina & Groselj 2008). Unfortunately, there are plans to canalise the remaining near-natural meandering section in the middle Sava, and a navigation channel between the Sava and Danube Rivers in Croatia is under consideration. But there is hope as Croatia has proposed the Nature Park Lonjsko Polje as a Natural and Cultural World Heritage Site in 2008 (http://www.pplonjsko-polje.hr/). The ecological value of the alluvial forests and retention areas impacted by the proposed navigation channel would be much higher, if the application will be

successful, and help to preserve the natural riverbed and its floodplains (Schneider-Jacoby 2005).

3.9.7. Velika Morava River Two Morava Rivers are found in the Danube basin. The ‘Slovak’ Morava is a left-hand tributary that enters the Danube east of Vienna (see Chapter 3.9.2). The Velika Morava (‘Great Morava’) corresponds to the lower section of the Morava basin in Serbia. The Serbian Morava is the lowermost large right-bank tributary of the Danube upstream of Iron Gate. The Latin sources refer to the ‘Slovak’ Morava as Marus and to the Serb Morava as Margus (Sinor 1997). The Serbian Morava drains 40% of the entire country, in total an area of approximately 38 000 km2. Small parts of the catchment are in Bulgaria (3%) as well as in Macedonia and Montenegro (<0.5% each). The basin is inhabited by 4.5 million people and the catchment consists of 39% arable land and 43% forested area (Table 3.1).

3.9.7.1 Geomorphology The Morava catchment has three sub-basins: (i) the catchment of the Velika Morava that extends from the confluence of the Juzna (Southern) and Zapadna (Western) Morava near the city of Stalac (130 m asl) to its confluence with the Danube, (ii) the catchment of the Juzna Morava and (iii) the catchment of the Zapadna Morava. The Velika Morava crosses densely populated and cultivated areas for 180 km. It receives 32 tributaries before it enters the Danube near the city of Smederevo (Rkm 1105). The Velika Morava valley contains among the most fertile soils in Serbia and is therefore important for crop production (SEPA 2007). Alluvial terraces and marshy bogs fringe the mainstem. The alluvial sediments consist of a mixture of Quaternary loess, Neogene lacustrine sediments, Mesozoic flysch sediments and Paleozoic schists. Pockets of volcanic and plutonic igneous rocks also occur (Jakovljevic et al. 1997). The Velika Morava has an average channel width of 140 m (maximum: 325 m) and a water depth (surface to bottom) of 1–4 m. Height of the river banks (from bank edge to thalweg or water surface) is 3–16 m. The 230-km long Juzna (Southern) Morava drains southeastern Serbia (catchment area: 15 446 km2). Its two major headwaters originate from the Macedonian-Serbian and Rilo–Rhodope Mountains and merge near the city of Bujanovac at 400 m asl. The most important tributary is the Nisava River (length 218 km; area 4068 km2, 25% is in Bulgaria) that originates on the southern slopes of the Stara Planina Mountains in Bulgaria and enters the Juzna Morava near the city of Nis. Although the Juzna Morava is considered a lowland river, it crosses a series of alluvial plains separated by constrained sections. Several of its tributaries are relatively natural with densely forested catchments and clear waters.

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The 308-km long Zapadna Morava River drains southwestern Serbia (catchment area: 15 567 km2). Its headwaters are ramified, originating in the Golija (1350 m asl), Mucanj and Tara Mountains in the Dinaric Alps (western Serbia). Its headwaters merge near the village Leposavic at 302 m asl. The largest tributary is the Ibar River (catchment area: 7500 km2, length: 272 km). It originates in eastern Montenegro at 1360 m asl, flows eastwards to Mitrovica (Kosovo), then north until it meets the Zapadna Morava near the city of Kraljevo.

3.9.7.2 Climate, Hydrology and Biogeochemistry The Morava River basin has a predominantly continental climate with an average annual temperature of 11–12 C (January: 1 to +1 C, June: 22–23 C). Precipitation is highest in May and June and lowest in February and October. In the alluvial plains, average annual precipitation ranges between 600 and 700 mm. Precipitation increases to 800– 1300 mm with increasing altitude. The Juzna Morava flows through a dry valley with an average precipitation of <600 mm (SEPA 2007). The average discharge of the Morava is 277 m3/s (average low flow: 50 m3/s; peak flow with 1% probability of occurrence: 2464 m3/s; ICPDR 2004, Table 3.2). Discharge peaks during the short snowmelt period in spring. Major floods occur when snow melting and heavy rains coincide, and its tributaries exhibit a torrential character with frequent flash floods associated with landslides. Erosion is prevalent in the entire basin, in particular in the almost completely deforested Juzna Morava sub-basin (UNECE 2007). High sediment yields reduce the flow capacity in the downstream Velika Morava River and increase flood risks. Flood protection embankments and chains of reservoirs have been constructed to reduce flood risks. All major cities as well as many industrial facilities and waste disposal sites are found in flood prone areas (ICPDR 2006). About 60% of the phosphorus (P) input originates from point sources such as industrial areas, wastewater treatment plants, as well as through the prevalent use of P in detergents. Less than 10% of the rural population and 30% of the urban population is connected to public sewerage systems (UNEP 2003; SEPA 2007). About 20% of the P-input originates from erosion, in particular from fertile arable lands (Schreiber et al. 2003). The annual load of P from the basin is 1841 tons/year (in 2004) and contributes 8% to the total P load of the Danube (Behrendt 2008). Dominant pathways for nitrogen input are groundwaters (40%) and point sources (i.e. urban areas; 25%). Topsoils in the basin have a high N-content resulting in an annual load of 28 246 tons/ year (in 2004), 6% of the Danube basin (Behrendt 2008). Based on the saprobic index, the Morava River is classified as ‘critically polluted’ at its mouth (ICPDR 2005), and BOD5 values are considerably higher compared to most Danube tributaries. Downstream of the confluence with the Velika

PART | I Rivers of Europe

Morava, Danube river sediments (bed and suspended sediments) contain elevated lead (Pb) concentrations (52– 70 mg/kg, Klaver et al. 2007) and increased levels of faecal coliforms. Recent changes in the Serbian economy have resulted in a significant reduction of pollutants. The economic decline and transformation to private ownership have resulted in a significant change in industrial production from 1998 to 2002 (ICPDR 2006). BOD5 and ammonium (NH4–N) concentrations show decreasing trends. Today, BOD5 is as low as <4 mg O2/L and NH4–N has stabilised to 500 mg/L. Nitrate and orthophosphate concentrations range between 1.5 and 2 mg/L and <400 mg/L, respectively (SEPA 2007). The Zapadna Morava and its tributary Ibar are the most polluted rivers in the catchment as well as in Serbia. They receive large volumes of untreated wastewater that contain phenols, lead, zinc and nickel from non-sustainable industrial complexes such as lignite mines, power plants and sawmills (UNEP 2003; Spasojevic et al. 2005).

3.9.7.3 Biodiversity In a recent survey, 42 fish species have been recorded for the Velika Morava River (MEP 2003). Cyprinidae predominate and Salmonidae, Esocidae, Cobitidae, Balitoridae, Siluridae, Ictaluridae and Percidae are also abundant. In the headwaters, cold-stenotherm invertebrates dominate the macroinvertebrate community, especially Plecoptera, Ephemeroptera, Trichoptera and Amphipods (mainly Gammarus spp.). Artifical ponds and reservoirs are mostly eutrophic and their benthic communities are represented by Oligochaeta (family Tubificidae, genera like Limnodrilus, Potamotrix, Tubifex) and Diptera (family Chironomidae, Chaboridae) (MEP 2003). Since 2005, the Chinese pond mussel (Anodonta (Sinanodonta) woodina) has been reported in the lower Velika Morava. Its abundance exceeds the native mussel Unio pictorum by a factor of 5, and is now spreading into other tributaries of the Danube such as the Sava (Paunovic et al. 2006). The non-indigenous tubificid worm Branchiura sowerbyi has a scattered distribution in the basin (Paunovic et al. 2005).

3.9.7.4 Human Impacts and Management Between 1960 and 1995, the Morava basin has undergone major hydro-engineering activities. The Velika, Zapadna, Juzna Morava Rivers as well as some of their tributaries have been regulated, meanders have been cut off, and the river courses shortened. Marshlands have been transformed into fish ponds (today 4000 ha), and comprehensive drainage systems have been put in place to increase the proportion of arable land (Jakovljevic et al. 1997). Extensive flood embankments (total length ranges between 1181 and 2015 km, depending on source) disconnect the floodplains from the river. Several multipurpose dams and reservoirs have been constructed that are used for flood protection,

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irrigation, municipal water supply (e.g. Prvonek, Barje, Gruza dams), and hydropower generation (e.g. Mepuvrsje, Gazivode reservoirs; volume: >10 million m3). Moreover, dredging of sand and gravel has impacted the hydromorphology of the rivers, and predicted increase in industrial activities could further degrade water quality.

3.9.8. Olt River The 615-km long Olt River in central and southern Romania drains a catchment of 24 439 km2 and enters the Danube at Rkm 604. The human population within the basin is 2.13 million, of which 53% are living in urban areas (population density: 87 inhabitants/km2, Table 3.1, Olt RD 2007). The largest cities along the river are Bra¸sov and R^amnicu V^alcea (285 000 and 110 000 inhabitants, repsectively).

3.9.8.1 Geomorphology The source (1800 m asl) of the Olt is near the headwaters of the Mure¸s River (tributary of the Tisza River) in the eastern Carpathian Mountains. The upper Olt crosses the intramontane basin between the eastern Carpathians and the volcanic Ca˘limani–Gurghiu–Harghita Mountains, flowing through Miocene and Quaternary sedimentary bedrocks. Further south, the Olt drains the Gheorgheni–Ciuc basin (700 m asl). There, bedrock consists of fluvial-lacustrine clastic deposits intermixed with volcano-sedimentary deposits derived from adjacent volcanic complexes. Then, the river flows through the Bra¸sov Basin filled with fluvial-lacustrine clastics intermixed with lignite, carbonates–diatomites and alluvial fan deposits, as well as with volcanic clastics and extrusive volcanic rocks. The river makes a northern bend around the Per¸sani Mountains, flows through the Fa˘ga˘ra¸s depression (400 m asl) that is filled with 100–150 m thick deposits of Pleistocene alluvial sediments derived from the southern Carpathians, and leaves the Transylvanian basin by cutting across the southern Carpathians in a steep gorge called ‘Pas Turnul Ro¸su’ (350 m asl). Until this location, the Olt follows the main Carpathian divide. It is the only river of the Carpathian basin that crosses the Carpathian Mountains and discharges directly into the Danube. The lower section of the Olt passes the pericarpathian front as well as the outer limits of the foreland basin before it reaches the Moesian plain (Precambrian metamorphic rocks), and then enters the Danube (Sandulescu 1994; Fielitz & Seghedi 2005). The Olt basin mainly consists of siliceous bedrock. In the upper region (Ca˘limani–Gurghiu–Harghita Mountains, Gheorgheni–Ciuc and Bra¸sov basins), small outcrops of calcareous bedrock occur.

3.9.8.2 Hydrology, Climate and Biogeochemistry The average discharge is 172 m3/s and maximum discharge (1% occurrence probability) is 3400 m3/s (Table 3.1, ICPDR

2004). The total length of the river network is 9872 km; and 15% are temporary streams (Olt RD 2007). Starting in the 1970s, the hydrology of the Olt has been fundamentally altered by the construction of >30 reservoirs and 650-km lateral embankments that disconnect former floodplains from the mainstem. Hydromorphological alterations affect 74 out of 622 rivers in the catchment. In the lower 310 km (Fa˘ga˘ra¸s to Islaz), the river has been transformed into a cascade of 25 large reservoirs. These reservoirs, together with hydropower plants along the Lotru and Cibin tributaries, provide a hydroelectric potential of 4.44 TWh/year. The Olt and Siret Rivers account for 30% of the total Romanian electrical production (Zinke 1999; Nistreanu et al. 2002). Many reservoirs in the basin receive high sediment inputs and siltation is an important issue (areas with high sediment yields: >250 tons km2/year; R~adoane & R~adoane 2005). Average annual air temperature ranges from 0 to 4 C in the upper, 6–8 C in the middle and 10–11 C in the lower river. Annual precipitation ranges from 700 to 1100 mm in mountainous regions (upper Olt, tributaries of the Bra¸sov section, and the gorge crossing the southern Carpathians), averages 600 mm in the middle hilly sections, and decreases to 400 mm in the lower section. The inner Gheorgheni– Ciuc and Bra¸sov basins exhibit low precipitation rates as well. Nitrate concentrations are elevated along the entire mainstem and peak in the reservoirs of Racovita (influenced by the city Sibiu) and Gura Lotrului (maximum: 19–22 mg/L NO3–N). In the Fa˘ga˘ra¸s basin, NO2–N concentrations reach 1–2 mg/L and NH4–N concentrations are 3.4 mg/L. NH4– N is also high near the city of R^amnicu V^alcea (2.2 mg/L) (Nistreanu et al. 2002). Microbial water quality at the confluence with the Danube is moderate, only faecal streptococci show high concentrations (Literathy et al. 2002). The lower section exhibits high organic pollution. Preda et al. (2005) reported heavy metal concentrations for the R^amnicu V^alcea valley that were <0.08 mg/L for copper, <0.13 mg/L for chromium, 0.213–0.69 mg/L for iron, 0.044–0.498 mg/L for manganese and <0.06 mg/L for zinc. Bravo et al. (2007) reported high contamination of reservoir sediments from mercury (Hg) with values of 44.5 mg/g in 1987, 30.3 mg/g in 1991 and 8–10 mg/g in more recent sediments.

3.9.8.3 Biodiversity In the upper Olt, Banyasz (2005) identified 124 (in 2002) and 91 (in 2003) diatom taxa, respectively. The most abundant species were Nitzschia dissipata, Navicula lanceolata, N. radiosa, Meridion circulare and Fragillaria construens. Mara et al. (1999) reported 15 amphibian and 12 reptile species from the upper and middle Olt. In the middle Olt, grey willow Salix elaeagnos and along the lower Olt ash (Fraxinus holotricha) and oak (Quercus pedunculiflora) dominate riparian vegetation (WWF 1999). Banarescu (1964) reported 46 fish species, including 3 non-natives (Oncorhynchus mykiss, Carassius gibelio and Ameiurus nebulosus), in the basin. The upper and middle sections

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exhibit richer fish diversity than the lower river (36 vs 29 species). A recent survey (2005–2007) at 10 sites along the mainstem of the river reported four species as non-native to the Olt basin: Oncorhynchus mykiss, Carassius gibelio, Pseudorasbora parva and Lepomis gibbosus (AR Olt 2007) and only 17 fishes as native, that is, 50% of the richness before the construction of hydropower plants. Ameiurus nebulosus most likely still occurs. High organic pollution and potentially toxic substances result in a low diversity of macroinvertebrates at the river mouth (Literathy et al. 2002).

3.9.8.4 Human Impacts and Management The Olt has a long history of human impacts. In particular during the last seven decades, the river has been dammed and embanked, floodplains and marshes have been drained, meanders have been cut off, tributaries diverted and banks reshaped. The river channel itself has been cleaned of riparian trees and bushes. Water abstraction, in combination with sporadic droughts, creates additional impacts on instream and riparian habitats. Domestic and industrial pollutants as well as accidental and continuous releases of hazardous substances from inactive and active waste disposal sites remain a key problem (Curtean-Ba˘na˘duc et al. 2007). Only a few wastewater treatment plants are in operation and illegal waste deposits impact remaining wetlands (NSAPBC 1996). Extensive gravel exploitation leads to a significant bedload deficit. In the course of the implementation of the WFD, it is aimed to apply new river restoration concepts that not only account for flood protection but also promote biodiversity through improving instream and riparian habitat quality (Olt RD 2007).

3.9.9. Siret River The 599-km long Siret River (Szeret in Hungarian, Seret in Ukrainian) is the 3rd longest tributary of the Danube and drains a catchment area of 46 289 km2 (Ukraine: 10%, Romania: 90%). Its major tributaries are the Suceava, Moldova, Bistri¸ta, Trotu¸s, R^amnicul Sarat, Birlad and Buza˘u Rivers. The Siret enters the Danube east of Gala¸ti at Rkm 155. The basin is inhabited by 3.5 million people with about 40% living in urban areas. The main cities in the basin are Suceava, Piatra Neam¸t and Baca˘u (106 000, 110 000, 176 000 inhabitants, respectively). In medieval times, the Baltic Sea–Black Sea transportation route followed the Siret valley, and today it forms the main road/railway artery from Bucharest to Moscov via Kiev.

3.9.9.1 Geomorphology The Siret originates in the Ukrainian part of the Bukovina region in the northeast Carpathian Mountains (1250 m asl). Dominating bedrock in the headwaters is Paleogene flysch

PART | I Rivers of Europe

and the headwaters form typical mountain valleys. The Siret flows first north-eastward before entering the Moldavian Plateau. It reaches Romania and flows southward crossing the eastern Romanian plains until its confluence with the Danube. In the middle river, well-developed and fertile alluvial terraces occur (Ungureanu 2006). The lower river exhibits a meandering style with numerous backwaters and oxbow lakes. All major tributaries of the Siret originate from the eastern Carpathian Mountains that are dominated by flysch bedrock. Two tributaries, the Bistri¸ta and the Moldova, originate from inner crystalline and volcanic bedrock. The Birlad River originates in the Moldavian Plateau and is a main left-bank tributary. It exhibits a semi-permanent flow regime. Despite the fact that the Siret flows through a hillylowland area over most of its length, it exhibits a strong Carpathian character in regard to its stream bed dynamics, longitudinal profile and thick alluvial deposits (Ichim & Radoane 1990). Agricultural area covers about 65% and forest 34% of the basin (Table 3.1).

3.9.9.2 Climate, Hydrology and Biogeochemistry The Siret basin has a temperate climate with continental influence. The mean annual temperature is 2 C in the mountainous part, 8 C in the hilly section and 10 C in the downstream plains. Mean annual precipitation ranges from 1200 mm (mountainous area) to 450 mm (Romanian lowlands). Precipitation peaks in May/June. Mean annual discharge is 210 m3/s, and peak discharge (1% probability of occurrence) is 3950 m3/s (Table 3.1, ICPDR 2004). The Siret and its tributaries exhibit flashy flow regimes with lowest rates from late summer until winter (lowest recorded discharge: 16 m3/s at the mouth, Ungureanu 2006). Ice cover lasts from mid-December to mid-March. Snowmelt-induced spring floods are common, although rainfall-induced floods (such as the disastrous flood in July 2005 in the sub-basin of the tributary Trotu¸s) can exceed spring floods and cause major devastation. At its mouth, biodegradable organic matter (BOD5) averages 7 mg O2/L and chemical oxygen demand (COD-Cr) averages 45 mg O2/L (1996–2000). These values are well above the ICPDR-TNMN target values of 5 mg O2/L and 25 mg O2/L, respectively (ICPDR 2005). Saprobic values show critical organic pollution at the mouth of the Siret (ICPDR 2005). However, during the past decade, BOD5 has shown a decreasing trend. Formerly, the Siret was among the most polluted Danube tributaries in respect to organic pollution (UNECE 2007). Because the basin is intensively used for agriculture, nitrogen through leaching and diffuse phosphorus emissions via erosion are prevalent (Schreiber et al. 2003). Only 30% of the population is connected to wastewater treatment plants (75% in urban areas, 3.3% in rural areas) (DAS 2004). In 2004, the basin contributed some 6996 tons N (2%) and 251 tons P (1.1%) to the total load of the Danube (Behrendt 2008). The Siret has one of the highest suspended sediment loads of all Carpathian rivers, corresponding to a total

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annual load of 10 million tons. Almost 50% of the total load originates from the Putna and R^amnicul Sa˘rat Rivers. The suspended solids of the Siret contain the highest DDT (0.05 mg/kg) and HBC (0.0069 mg/kg) contents of all Danube tributaries (ICPDR 2005). The Siret is exploited for hydropower and irrigation. In addition, the mining industry, primarily for copper, zinc, lead, coal and uranium, is a pressure in the upper basins of some of its tributaries. Cyanide spills from abandoned industrial sites were reported in January 2001 and March 2004 in the tributary S¸ omuzul Mare with cyanide concentrations temporary up to 4.0 mg/L (EU limit is 0.05 mg/L (EC 1998). Nowadays, some projects for ecological rehabilitation of abandoned sites are underway.

3.9.9.3 Biodiversity The Siret basin has experienced a profound change in its morphology and water quality, especially downstream of urban and industrial areas. The present fish richness (34 species) is lower compared to the 1960s (42 species). Five non-native species (Ctenopharyngodon idella, Hypophthalmichthys molitrix, H. nobilis, Oncorhynchus mykiss and Salvelinus namaycus) and three invasive species (Pseudorasbora parva, Lepomis gibbosus and Perccottus glenii) are new since the 1960s (Battes et al. 2005). Unfortunately, further internationally published information on other organism groups is unknown at this time.

3.9.9.4 Human Impacts and Management The most important hydromorphological pressures in the basin are caused by the construction of 30 reservoirs, the building of extensive lateral embankments, as well as water diversions and abstractions. The Izvoru Muntelui reservoir (Lake Bicaz) on the Bistri¸ta tributary is the largest reservoir within the basin (total volume: 1230 million m3). During the last 50 years, most wetlands fringing the river have been disconnected by dikes or have been drained (DAS 2004). Uncontrolled deforestation, erosion and siltation of reservoirs increase the flood risk in the basin. In addition, river banks are often impaired by illegal gravel excavation. Regulatory monitoring is underway. Today, there have been common undertakings among Slovakia, Hungary, Ukraine and Romania to inventory Accidental Risk Spots (ARS). The next steps agreed are (i) to assess the actual risk of accidents and (ii) to install an accident emergency warning system. The inventory of old contaminated sites in potentially flooded areas needs to be completed as well as the inventory of protected areas (GTZ 2007). Currently there are 30 areas designated as conservation sites to protect specific habitats or species (total area 102 300 ha or 4% of the basin area). The entire basin is designated as a nutrient-sensitive area. The perimeter of 54 localities within the basin has been designated as a ‘nitrate vulnerable area’ due to agricultural activities (DAS 2004).

3.9.10. Prut River The 953-km long Prut, or Pruth, originates in the Chernogora Mountains in the southwestern Ukrainian Carpathians at 1600 m asl. It drains an area of 28 568 km2 before discharging into the Danube just upstream of the Danube delta, east of Gala¸ti (Danube Rkm 132). It is the second longest tributary of the Danube. It flows for the first 211 km eastwards in the Ukraine, then forms the border between Ukraine and Romania (31 km) and the border between Romania and Moldova (711 km) while flowing south-southeast. Its main tributaries are the Ceremosh, Derelui, Volovat, Baseu, Corogea, Jijia, Chineja, Ciugur and Lapusna Rivers; most of them are regulated by reservoirs (ICPDR 2004, UNECE 2007). The largest city along its banks is Chernivtsi (Western Ukraine, 240 000 inhabitants), and the main industrial complex is at Ia¸si, Romania. The total human population in the basin is 3,2 million (Teodosiu et al. 2003).

3.9.10.1 Geomorphology The Prut basin can be divided into three sections: (i) a mountainous section (20% of the basin), (ii) a piedmont section (12%) and (iii) lowland plains (68%) (Zeryukov & Pavlov 1968). The mountainous part consists of limestone rock and Paleocene flysch. The piedmont is covered by Miocene deposits of clay intermixed with argillite, conglomerate and sand as well as Torton and Sarmate bedrock. The lowland basin is filled with sedimentary and alluvial sediments. The basin drains three ecoregions according to Illies (1978), namely the Carpathians, Eastern plains and the Pontic Province. Formerly, the lower Prut was fringed by vast floodplains (total area: 1665 km2), but 75% have been lost or are now functionally extinct (WWF 1999).

3.9.10.2 Climate, Hydrology and Biogeochemistry The Prut Basin has a moderate mild continental climate in the upper section and a harsher continental climate in the lower section. Average annual precipitation ranges from 1400 mm (upper section) to 600–440 mm (lowland plains). The average annual air temperature increases from 2 C to 9 C from the headwaters to the mouth, and ice cover lasts for 60–65 days. Snowmelt starts in March and lasts on average for only 10–15 days (DAP 2004). The average discharge at the mouth is 67 m3/s and maximum discharge (1% occurrence probability) is 2940 m3/s (Table 3.1, ICPDR 2004). The upper section and tributaries exhibit a flashy flow regime, and flooding is an important issue in the basin. Major floods often occur in March when snowmelt and heavy rain coincide, although floods may occur at any time of the year. The catchment of the Prut is intensively used for agriculture and vineyards, and is a major source of diffuse nutrients. In addition, 98 000 ha of irrigated land (mainly in Romania;

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Teodosiu et al. 2003) contribute to the prevalent soil erosion and nutrient inputs. Although nitrate, nitrite and phosphate concentrations are lower today compared to the 1980–1990s, tributaries of the Prut as well as the upper and middle sections are still affected by urban wastewater discharge, waste disposal, and outdated industrial production modes. Chemical Oxygen Demand (COD-Cr; up to 40mg O2/L) and organic pollution remain high at the mouth and in the downstream Danube section (period 1996–2000; ICPDR 2005).

3.9.10.3 Biodiversity Information on the biodiversity of the Prut is rather scarce. Usat^ai (2004) has studied the composition of the fish fauna of the middle (Moldavian) and of the lower Prut and its main tributaries between 1996 and 2002. Between 24 and 30 fish species are reported for the middle Prut. Cyprinidae and Percidae are the dominant families; in total six families occur. About 35% of the species are of economic interest like Aspius aspius, Vimba vimba, Esox lucius, Hypophthalmichthys molitrix, Cyprinus carpio and Stizostedion lucioperca. Their relative abundance, however, ranges from only 12–19%. Zingel zingel and Z. streber occur in the middle Prut, and they are listed in the Red Book of Moldova and are protected. Some 37 fish species are documented in the lower Prut. Leuciscus idus occurs as a third protected species, and Umbra krameri, Abramis brama and Carassius carassius are species of high conservation value (Usat^ai 2004). In summer 2007 Moldavian and Romanian scientists conducted a common survey of the fish fauna of the Prut River. They report the occurrence of 46 species (41 native, 5 nonnative) (Davideanu et al. 2008 and personal communication).

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In the lower Prut valley, 189 bird species, including 123 breeding species, are reported (Biodiversity Office MD 2007). The spreading of willows into the reed belts has created favourable conditions for some nesting birds such as Ardeola raloides, Egretta garzetta, Ardea cinerea, Nycticorax nycticorax, Platalea leucorodia, Plegadis falcinellus, Casmerodius albus, Phalacrocorax carbo, P. pygmaeus and Ardea purpurea. The water chestnut (Trapa natans) still occurs along the lower Prut; due to water eutrophication it has dramatically decreased (WWF 1999). The lower Prut floodplain lakes Beleu and Manta are the largest natural lakes in Moldova and have been designated as a Ramsar site since 2000 (www.wetlands.org). The Beleu Lake serves as habitat for 27 fish species. Economically valuable species include Abramus brama, Rutilus rutilus, Cyprinus carpio, Sander lucioperca, Silurus glanus, Alosa immaculata and Esox lucius. Hucho hucho and Umbra umbra are protected by Moldavian law. The ecological capacity of Beleu Lake for the reproduction of fish and for the development of sturgeon caviar has been strongly reduced during the past decades. The main reasons are the siltation of the Manolescu channel, construction of access roads to oil boreholes and water pollution caused by oil products (Biodiversity Office MD 2007).

3.9.10.4 Human Impacts and Management Starting in the 1960s, the Prut and its tributaries have undergone major hydromorphological changes. More than 30 reservoirs have been built within the basin. The largest is the hydropower station of Stanca–Costesti in the upper Prut (total volume: 735 million m3), jointly operated by Romania PHOTO 3.11 Prut River downstream of Stanca–Costesti dam and reservoir. (Photo: Dan Ba˘da˘ra˘u, Romania).

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and Moldova (UNECE 2007) (Photo 3.11). The lower Prut remains mostly free-flowing, although lateral embankments have disconnected the formerly vast floodplain from the main channel. Large alluvial areas in the lower section, near the Danube, have been drained. As a consequence, Lake Brate¸s (Romania’s largest freshwater lake) has substantially decreased in area. The Ramsar site ‘Lower Prut Lakes’ covers an area of 19 150 ha including 14 400 ha of wetlands. The lower Prut does not meander strongly. The floodplain is up to 6 km wide and includes wet meadows and riparian forests. Aquatic biodiversity is high in Lake Beleu (area: 1700 ha) and Manta floodplain lakes (a complex of interconnected lakes) (Ramsar 2000).

3.9.11. Danube delta The Danube delta is located on the coast of the Black Sea and includes the area between the three main Danube branches Chilia, Sulina and Sf. Gheorghe (Photo 3.12). It covers an area of 4560 km2 (Table 3.1); 82% is located in Romania, 18% in Ukraine. The delta starts at the first bifurcation of the Danube (Rkm 116) where the northern Chilia branch splits off, forming the boundary between Romania and Ukraine. The highly canalised middle branch Sulina serves as the navigation channel to the Black Sea (80-m wide, a minimum depth of 7.3-m is secured via dredging). The reported population of the Romanian part of the delta amounts to about 15 000 (RIZA 2000). The majority lives in rural settlements (64%) and one third in the port-town of Sulina. Fishing and agriculture are major sources of income. About 10 000 people are reported for the Ukrainian part of the delta and 110 000 people inhabit the cities Izmail and Vilkovo at the northern edge of the delta in Ukraine. The city of Tulcea at

the entrance of the delta in Romania has about 90 000 inhabitants and is not included in the calculations of human population density (Table 3.1). Deviant indications of the size of the delta (4127 to 8800 km2) result from different delimitations, i.e. whether the Ukrainian part but as well whether lakes and lagoons, which are geologically and ecologically attached to the delta are accounted for. An area of about 6800 km2 is under legal protection including floodplains, the Razim-Sinoe lacustrine system and marine areas.

3.9.11.1 Geomorphology Deltaic conditions were initiated during the early Upper Pleistocene, when the Danube started to discharge into the Black Sea. It was a fluvial-dominated delta in an embayment of the Black Sea, which was sheltered by a barrier (initial cordon) in the late Pleistocene/early Holocene (Panin et al. 1983; Giosan et al. 2006). Subsequent clogging led to the successive formation of the Danube delta branches and its north- and southward expansion. The evolution of the delta occurred in five main phases: (i) the formation of the Initial Letea–Caraorman Spit (11 700–7500 years BC), (ii) the St. George I Delta (9000–7200 years BC), (iii) the Sulina Delta (I and II) (7200–2000 years BC), (iv) the St. George II and Kilia Deltas (2800 years BC to present) and (v) the Cosna– Sinoe Delta (3500–1500 years BC) (Panin et al. 1983). The delta is formed on a sequence of up to 400 m thick detrital deposits that accumulated mainly during the Upper Pleistocene and Holocene (Panin et al. 2004). Histosols (27%), gley soils (22%), limnosols (17%), psammosols and sands (16%) and alluvial soils (13%) predominate. Smaller areas are covered by solonchaks, kastonozems and anthrosols (Munteanu 1996). PHOTO 3.12 Danube delta, St. Georges arm near the mouth. (Photo: Christian Baumgartner, Austria).

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The delta consists of (i) a fluvial zone characterised by large sandy levees and small densely vegetated lakes and (ii) a fluvio-marine zone that includes marine levees as well as important lacustrine complexes and undergoes morphohydrographic changes at its contact zone with the Black Sea (RIZA 2000). The marine delta plain covers 1800 km2 and the delta-front unit 1300 km2 (delta-front platform: 800 km2, delta-front slope: 500 km2). The maximum altitudinal difference in the delta is 15 m ( 3 m to +12 m), although about 50% is at 0–1 m asl. The level difference between the apex and the Black Sea is 3.6 m (RIZA 2000). Since the northern part of the delta is slowly sinking, the discharge of the northern Chilia branch has increased (UNEP-WCMC 1991). The Danube delta is still expanding seaward at a rate of 24–30 m annually (http://www.icpdr.org/ icpdr-pages/danube_delta.htm). Between the river branches, four lake complexes can be distinguished: Sontea-Fortuna (3705 ha), Gorgova-Uzlina (6848 ha), Matita-Merhei (5701 ha) and Rosu-Puiu (6519 ha) (RIZA 2000).

3.9.11.2 Climate, Hydrology and Biogeochemistry The climate in the delta is temperate continental with some maritime influence. It experiences short, mild winters and hot, dry summers. The average annual air temperature is 11 C (January: 9 to 5 C; June: 22–23 C). Minimum air temperature is 25 C, maximum is 37 C, and temperature slightly increases from west to east. The number of frost days (Tmin <0 C) ranges between 84 (western part) and 57 (eastern part). Long periods of ice cover are rare. Total precipitation is 300–400 mm, evaporation 800–1000 mm (RIZA 2000, 2002). The proximity to the sea and the humidity originating from numerous lakes and secondary branches influences precipitation patterns (UNEP-WCMC 1991). Air humidity is 80% (up to 90% in winter). Due to the high average discharge of the Danube (6486 m3/s) at the delta entrance, aquatic environments prevail. Discharge peaks in summer (33% of the total annual discharge) and is low in autumn and winter. The total Danube discharge entering the delta splits into Chilia Branch (about 53– 57%), Sulina Branch (about 19–22%) and Sf. Gheorghe Branch (about 23%). Major channelization of Sulina Branch has significantly altered the natural discharge pattern in the Danube delta: while the discharge of the Tulcea arm (Sulina and Sf. Gheorghe Branch) increased by 17% that of Chilia Branch diminished by 17% and now suffers from strong siltation due to reduced flow (Bloesch 2005b). The total annual suspended sediment load carried by the Danube at the mouth has decreased from 67.5 million tons (1921– 1960) to 29.2 million tons (1981–1990) (RIZA 2000). The Danube delta acts mainly as a sink of nitrogen (denitrification in reed beds) but is a source of phosphorus (Suciu et al. 2002). In general, the delta has a low retention capacity and is mainly a by-pass for nutrients which is enhanced in wet years of high discharge and less pronounced in

PART | I Rivers of Europe

dry years. Reconnecting wetlands will enhance retention capacity. The canalization has diminished the ability of the delta to retain nutrients; more nutrient-rich water flows through the main canals rather than being distributed through the wetlands and reed beds. The average concentration of dissolved nutrients is 1–4 mg DIN/L and 0.1–0.3 mg TP/L (1996–2003). The concentrations of iron, cadmium and lead are elevated in the Danube branches as well as in the Delta lakes (ICPDR 2005). A significant eutrophication of the Delta lakes in the 1950s–1990s has drastically reduced biodiversity (Va˘dineanu et al. 2001). This has been recently stopped due to reduced nutrient inputs and loads.

3.9.11.3 Biodiversity The Danube delta comprises 23 natural and 7 man-made ecosystem types (G^as¸tescu et al. 1999). Extensive species lists of flora and fauna are found in Tudorancea and Tudorancea (2006), and a comprehensive fish atlas is presented in O¸tel (2007). The Danube delta forms among the largest reed bed zone worldwide. The delta is a major hotspot of biodiversity where boreal species and species typical for Central and Western Europe co-occur. A total of 1460 vascular plants and 3500 animal species, including 473 vertebrates (74 fish, 9 amphibians, 12 reptiles and 325 birds), have been reported. Since forests and forest-steppe habitats are decreasing, many of these species are included in the Red List of the Danube delta Biosphere Reserve (RIZA 2002). Today, >1/3 of the vascular plants are included in the Red List of the Danube delta Biosphere Reserve. The delta provides habitat for 60% of the world population of Pygmy cormorant, 5% of the Palaearctic population of White pelican and 90% of the world population of the Red-breasted goose (RIZA 2000 and references therein). The five Danube sturgeons (Huso huso, Acipenser gueldenstaedtii, A. nudiventris, A. stellatus and A. ruthenus) are highly endangered, and A. sturio is already extirpated (AP 2006; Bloesch et al. 2006). The threat for sturgeons is not only poor water and habitat quality, but also over-exploitation and poaching due to the economic value of caviar. Other fish listed as threatened include Umbra krameri, Misgurnus fossilis and Carassius carassius (O¸tel (2007)). Within the Razim–Sinoe lacustrine system, Sander lucioperca is the only predator fish that has been able to adapt to the eutrophication conditions. Cyprinidae like A. brama increased in the lacustrine system along with the increased phosphorus content of the water. Moreover, the numbers of Carassius auratus, an exotic and invasive species, increased. C. auratus, together with extensive embankments of floodplain areas, impede the reproductive success of carp (ICPDR 2005).

3.9.11.4 Conservation and Management The delta is impacted by catchment and local processes. An altered sediment regime, embanked floodplains and increased pollution are major catchment factors that affect

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Chapter | 3 The Danube River Basin

FIGURE 3.9 Total yield (dashed line; right axis) and relative proportion of species (left axis) of the commercial freshwater fishery in the lakes of the Danube delta (1960–1998; redrawn from Navodaru et al. 2002).

the delta. Within the delta, an area of 1000 km2 was embanked, drained and converted for agriculture, forestry and aquaculture between 1960 and 1989. It decreased the connectivity between the river and its wetlands. For example, 235 km2 of the transitional Razim–Sinoe lake system has been embanked and disconnected from the influence of the Black Sea. The natural channel network has been artificially extended from 1743 km to 3496 km in the period 1920–1990 (G^as¸tescu et al. 1983). Despite these multiple human impacts, >3000 km2 of wetlands and the adjacent Ukrainian secondary delta (250 km2) remain connected to the river and represent the largest almost undisturbed wetlands in Europe. Although near-natural in large parts, some ecosystem functions are still reduced due to former mismanagement, overfishing and polder constructions (G^as¸tescu & S¸ tiuca˘ 2006). About 6800 km2 are designated as a transboundary UNESCO Biosphere Reserve, shared by Romania and Ukraine. The area includes floodplain forests, coastal biotopes, sand dunes and >600 natural lakes. The core area (3100 km2) was declared both as a World Natural Heritage Site and Ramsar site in 1991. Current restoration in the framework of the Biosphere Reserve may partly improve the situation while new impacts of navigation may disturb the system again (TEN-T, Bystroe channel). Between 1994 and 2003, 15% of disconnected areas have been re-connected in the delta (ICPDR 2004). Fish farming was introduced in the Danube delta in 1961. Cultured species are the common carp (Cyprinus carpio), silver carp (Hypophthalmichthys molitrix), bighead carp (Aspiorhynchus laticeps) and gras carp (Ctenopharyngodon idella). Today, production costs in the often-oversized ponds (50–1000 ha) nearly exceed production values. The total catch of fish in the delta has declined during the past decades and shifted from piscivorous to less profitable non-piscivorous species due to changes in abiotic and biotic conditions (Figure 3.9). The commercial catch of migratory anadromous sturgeons (Huso huso, Acipenser g€ uldenstaedti and A. stellatus) collapsed from 1000 tons/year at the beginning

of 20th century to 10 tons/year in 1990 (Navodaru 1998). It is assumed that today’s smaller nutrient loads in the Danube may counteract the eutrophication problems in the delta. Increasing attention for the restoration of wetlands should have a positive effect on the water quality of the delta via an intensification of hydrological contact zones (ICPDR 2004).

3.10. CONCLUSION The Danube is the river that most effectively integrates and defines Europe. Culturally and biologically, the river has always been a separator as well as a connector. It served as a migration corridor for organisms and cultures, and has been an area of dispute as well as a major melting pot of cultures. It also is listed as one of the world’s top 10 rivers at risk (Wong et al. 2007). The development of the Trans-European Network for Transport, the ongoing construction of smalland medium-sized hydropower plants along its tributaries, bed incision, truncation of sediment transport and rapid landuse change within the basin pose major threats. Nevertheless, the governments of Bulgaria, Romania, Ukraine and Moldova agreed in 2000 to establish the Lower Danube Green Corridor. The agreement, which was facilitated by WWF, is one of the most ambitious wetland protection and restoration projects in Europe, with 1 000 000 ha new and existing protected areas, and 224 000 ha of floodplains to be restored to their near-natural state.

Acknowledgements This chapter would not have been possible without the kind assistance of numerous scientists, members of administrations, international organisations and NGOs. Our sincere thanks go to (sorted alphabetically): Naida Andelic (PE ‘Water area of the Sava River Basin’, BiH), Kestas Arbaciauskas (Vilnius University, LT), Jasmine Bachmann

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(ICPDR, AT), Dorottya Banyasz (RO), Darko Barbalic (Hrvatske Vode, HR), Sanja Barbalic (Hrvatske Vode, HR), Klaus W. Battes (Bacau University, RO), Horst Behrendt (IGB, Berlin), Danko Biondic (Hrvatske Vode, HR), Ales Bizjak (Institute for Water of the Republic of Slovenia, SLO), Nina Bogutskaya (Russian Acedemy of Sciences, RUS), Elisabeth Bondar-Kunze (WasserCluster Lunz, AT, Oana Boingeanu (RO), Mitja Brilly (University of Ljubljana, SLO), Jan Cernecky (State Nature Conservancy of the Slovak Republic, SK), Bela Csanyi (VITUKI, HU), Tzvetanka Dimitrova (Danube River Basin Directorate, BG), Dumitru Drumea (Institute of Ecology and Geography, MD), Andreea Galie (National Administration ‘Apele Romane’, RO), Miroslav Folt yn (PE ‘Povodi’, CZ), J€ org Freyhof (IGB, Berlin), Katarina Holubova (Slovak Water Research Institute (VUVH), SK), Alexei Iarochevitch (Ukrainian Centre for Water and Environmental Projects, UA), Georg Janauer (University of Vienna, AT), J€ org Lohmann (IUCN, Programme Office for South Eastern Europe, SRB), Peter Lengyel (RO), Dr. Jarmila Makovinska (Slovak Water Research Institute (VUVH), SK), Petruta Moisi (Eco Counselling Europe (CCEG), RO), Jovana Nastasijevic (German-Serbian WFD Twinning Project, SRB), Vladimir Muzik (Slovak Environment Agnecy (SEA), SK), Martin Neuner (Section Hydrography and Hydrology, Department of the Tyrol State Government, AT), Dragana Ninkovic (Jaroslav Cerni Institute for the Development of Water Services, SRB), Ion Navodaru (Danube delta National Institute for R&D, RO), Dusan Ognjanovic (Ministry of Science and Environmental Protection of the Republic of Serbia, SRB), Viktor Oroszi (Danube Enviornmental Forum (DEF), HU), Daniela Popescu (Water Directorate Olt, RO), Anca Savin (Water Directorate Prut, RO), Ursula Schmedtje (Regierung Oberbayern, D), Ferdinand Sporka (Slovak Academy of Sciences, SK), Zoran Stojanovic (Hydrometeorological Service of Serbia, SRB), Dr. Alexander Sukhodolov (IGB, D), Thomas Tittizer (D), Manuela Toma (Water Directorate Siret, RO), Lubomira Vavrova (IUCN, Programme Office for South Eastern Europe, SRB), Birgit Vogel (ICPDR, AT), Izabela Windischova (Ministry of the environment, SK), Harald Wintersberger (AT), Johannes Wolf (Distelverein, AT), Matthias Zessner (Vienna University of Technology, Institute for Water Quality, Resources and Waste Management, AT), Alexander Zinke (Zinke Environment Consulting, AT).

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PART | I Rivers of Europe

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Chapter | 3 The Danube River Basin

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Tirol 2008. Data with the courtesy of the Amt der Tiroler Landesregierung, Abteilung Hydrographie und Hydrologie. Mai 2008. Tittizer, T., Sch€ oll, F., Banning, M., Haybach, A., and Schleuter, M. 2000. Aquatische Neozoen im Makrozoobenthos der Binnenwasserstrassen Deutschlands. Lauterbornia 391–17, Dinkelscherben. Tittizer, T., Fey, D., Sommerh€auser, M., Malnas, K. and Andrikovics, S. 2008. Versuche zur Wiederansiedlung der Eintagsfliegenart Palingenia longicauda (Olivier) in der Lippe. Recolonization experiments of mayfly Palingenia longicauda (Olivier, 1791) in the Lippe River in Germany. Lauterbornia 63: Dinkelscherben, 2008. Thorp, J.H., and Delong, A.D. 2002. Dominance of autochthonous autotrophic carbon in food webs of heterotrophic rivers. Oikos 9: 543–550. TNMN 1996 ff (1996 – 2005). Water Quality in the Danube Basin, TNMN Yearbooks 1996 ff., International Comission for the Protection of the Danube River, ICPDR, Vienna. Tockner, K., Schiemer, F., and Ward, J.V. 1998. Conservation by restoration: the management concept for a river-floodplain system on the Danube River in Austria. Aquatic Conservation: marine and Freshwater Ecosystems 8: 71–86. Tockner, K., Malard, F., and Ward, J.V. 2000. An extension of the flood pulse concept. Hydrological Processes 14: 2861–2883. Tudorancea, C. and Tudorancea, M.M. (eds). 2006. Danube delta, Genesis and Biodiversity, Backhuys Publishers, Leiden, 444 pp. Turner, R.E., Rabalais, N.N., Justic, D., and Dortch, Q. 2003. Global patterns of dissolved N, P and Si in large rivers. Biogeochemistry 64: 297–317. and Nogradi, S. 2005. Middle-term changes in caddisfly Uherkovich, A., (Trichoptera) communities of the Hungarian part of the Drava river during the years 1992–2004. Natura Somogyiensis 7: 49–62. Umweltbundesamt 1999. Fliessende Grenzen. Lebensraum March-ThayaAuen. Distelverein. UNECE 2006. Inventory of main standards and parameters of the E waterway network (“Blue Book”. United Nations Economic Commission for Europe – Inland Transport Committee, UNECE, Geneva, 2006. UNECE 2007. Assessment of the status of transboundary waters in the UNECE region - preliminary assessment of transboundary waters in the Black Sea region. UNECE, Economic Commission for Europe. ECE/MP.WAT/WG.2/2007/9., http://www.unece.org/env/water/publications/assessment/assessmentweb_full.pdf (accessed 08.05.2008). UNEP 2004. Rapid Environmental Assessment of the Tisza River Basin. United Nations Environment Programme, UNEP/Regional Office for Europe and UNEP/DEWA/GRIDEurope, 66 pp. http://www.grid. unep.ch/product/publication/download/tisza.pdf (accessed 06.05.2008). UNEP 2003. Phenol spills in the Sitnaca and Ibar River System. UNEP/ OCHA Assessment Mission, UNEP, Geneva 2003. http://www.reliefweb.int/ochaunep/edr/Kosovo.pdf (accessed 06.05.2008). UNEP-WCMC 1991. United Nations Environment Programme, World Conservation Monitoring Centre. Description of the Danube delta Biosphere Reserve, March 1991. http://www.unep-wcmc.org/sites/wh/ danubed.html (accessed 21.05.2008). Ungureanu, A., 2006. Siret (Fluss). Alpen-Adria Universit€at Klagenfurt. http://eeo.uni-klu.ac.at/index.php/Siret_(Fluss) (accessed 08.05.2008). Usat^ai, M. 2004. Diversity of fish fauna in the catchment area of the Prut River in Republic of Moldova. Analele S¸ tiin¸tifice ale Universita˘t¸ii “Al. I.Cuza” Ia¸si, s. Biologie animala˘, Tom L, pp. 9. Va˘dineanu, A., Cristofor, S., and Iordache, V. 2001. Lower Danube River System biodiversity changes. In: Gopal, B., Junk, W.J., Davis, J. (eds). Biodiversity in Wetlands: Assessment, Function and Conservation, Backhuys Publishers, pp. 29–63. Vannote, R.L., Minshall, G.W., Cummins, K.W., Sedell, J.R., and Cushing, C.E. 1980. The river continuum concept. Canadian Journal of Fisheries and Aquatic Sciences 37: 103–137.

PART | I Rivers of Europe

Wachs, B. 1997. Zustand und Qualit€at der Donau. Verantwortung f€ur einen europ€aischen Strom. Schriftenreihe des Bundesamtes f€ ur Wasserwirtschaft 4: 28–51. Weithmann, M.W. 2000. Die Donau. Ein Europ€aischer Fluss und seine 3000 j€ahrige Geschichte. Styria, Graz. Austria. 534 pp. WFD Report 2004. Report of the Slovak Republic processed for the European Commission in line with Water Framework Directive, Article 3 and Annex I. Ministry of the Environment of the Slovak Republic, Water Research Institute, Slovak Hydrometeorological Institute, Slovak Environmental Agency, June 2004. Wohl, E. in press. A World of Rivers. Yale University Press. Wong, C.M., Williams, C.E., Pittock, J., Collier, U., and Schelle, P. 2007. World’s Top 10 Rivers at Risk. WWF International, Galnd, Switzerland, 53 pp. WWF 1999. Evaluation of wetlands and floodplain areas in the Danube River Basin. Danube Pollution Reduction Programme. Programme Coordination Unit UNDP/GEF Assistance prepared by WWF DanubeCarpathian-Programme and WWF-Auen-Institut (Germany). Final Report, 75 pp. http://www.icpdr.org/wim07-mysql/search.php?tpl=icpdrsearchresult&siteid=2&q=evaluation+wetlands+floodplain+area +danube (accessed 09.08.2008). WWF 2002. Waterway Transport on Europe’s Lifeline the Danube. WWFEigenverlag, Vienna, 134 pp. http://assets.panda.org/downloads/DanubeReport.pdf (accessed 08.08.2008). Zeryukov, V.I., and Pavlov, E.F. 1968. Proposed complex utilization of water resources in the Prut River basin. Power Technology and Engineering (formerly Hydrotechnical Construction) Vol. 2, Number 1: 8–11, January 1968. Zessner, M., Postolache, C., Clement, A., Kovacs, A., and Strauss, P. 2005. Considerations on the influence of extreme events on the phosphorus transport from river catchments to the sea. Water Science and Technology 51(11): 193–204. Zinke, A. 1999. Dams and the Danube: Lessons from the Environmental Impact. Presentation at the first World Commission of Dams Forum Meeting, March 25–26, Prague, Czech Republic. Zsuffa, I. 2002. Internal document of the “Tisza River project” (www.tiszariver.com) by the courtesy of Istvan Zsuffa and Geza Jolankai. € Zulka, K.P. 1991. Uberflutung als €okologischer Faktor: Verteilung, Ph€anologie und Anpassungen der Diplopoda, Lithobiomorpha und Isopoda in den Flußauen der March. PhD Thesis. University of Vienna, Vienna.

RELEVANT WEBSITES BSC – Commission on the Protection of the Black Sea against Pollution. www.blacksea-commission.org Danube–Black Sea Strategic Partnership. www.blacksea-environment.org DEF – Danube Environmental Forum, http://def.distelverein.at/ daNubs-Project, http://danubs.tuwien.ac.at/ IAWD – International Association for Water Works in the Danube Basin, http://www.iawd.at ICPDR – International Commission for the Protection of the Danube River. www.icpdr.org IAD – International Association of Danube Research, www.iad.gs MIDCC – Multifunctional Integrated Study – Danube River Corridor and Catchment http://www.midcc.at/ International Sava River Commission, www.savacommission.org UNDP/GEP – Danube Regional Project, www.undp-drp.org WWF – Danube-Carpathian Programme Office (Vienna), www.panda.org/ dcpo/

Chapter 4

The Iberian Rivers Sergi Sabater

Maria Jo~ao Feio

Manuel A.S. Gra¸ca

Institute of Aquatic Ecology, University of Girona, Campus Montilivi 17071, Girona, Spain Catalan Institute for Water Research (ICRA), Girona, Spain

IMAR and Department of Zoology, University of Coimbra, 3004-517 Coimbra, Portugal

IMAR and Department of Zoology, University of Coimbra, 3004-517 Coimbra, Portugal

Isabel Mun˜oz

Anna M. Romanı

Department of Ecology, Faculty of Biology, University of Barcelona, Avenue Diagonal 645, 08028 Barcelona, Spain

Institute of Aquatic Ecology, University of Girona, Campus Montilivi 17071, Girona, Spain

4.1. 4.2.

4.3.

4.4.

4.5.

Introduction The Guadiana 4.2.1. Historic Changes and Human Impacts 4.2.2. Biogeographic Setting 4.2.3. Physiography, Climate, and Land Use 4.2.4. Geomorphology, Hydrology, and Biogeochemistry 4.2.5. Aquatic and Riparian Biodiversity 4.2.6. Management and Conservation The Guadalquivir 4.3.1. Historic Changes 4.3.2. Biogeographic Setting 4.3.3. Physiography, Climate, and Land Use 4.3.4. Geomorphology, Hydrology, and Biogeochemistry 4.3.5. Aquatic and Riparian Biodiversity 4.3.6. Management The Duero 4.4.1. Historic Changes and Human Impacts 4.4.2. Biogeographic Setting 4.4.3. Physiography, Climate, and Land Use 4.4.4. Geomorphology, Hydrology, and Biogeochemistry 4.4.5. Aquatic and Riparian Biodiversity 4.4.6. Management and Conservation The Ebro 4.5.1. Historical Perspective 4.5.2. Biogeographic Setting 4.5.3. Physiography, Climate, and Land Use 4.5.4. Geomorphology, Hydrology, and Biogeochemistry

Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

4.6.

4.7.

4.5.5. Aquatic and Riparian Biodiversity 4.5.6. Management and Conservation The Tagus 4.6.1. Historical Perspective 4.6.2. Biogeographical Setting 4.6.3. Physiography, Climate, and Land Use 4.6.4. Geomorphology, Hydrology, and Biochemistry 4.6.5. Aquatic and Riparian Biodiversity 4.6.6. Management and Conservation Additional Rivers 4.7.1. The Ag€ uera 4.7.2. The J ucar 4.7.3. The Mondego 4.7.4. The Segura 4.7.5. The Ter 4.7.6. Conclusions and Perspectives Acknowledgements References

4.1. INTRODUCTION The Iberian Peninsula encompasses a variety of climatic influences within a relatively small geographical space. There is a 4 C difference between the annual average temperature in the septentrional and the meridional coasts of the Iberian Peninsula. The complex orography causes large variations in climate at local and regional scales. For example, summer temperatures in the Guadalquivir river basin may reach 47 C, while winter temperatures may reach 20 C in the 113

114

PART | I Rivers of Europe

at >30%. Rainfall can be intense in the Mediterranean area (50 mm in 1 h), in particular at the end of summer and autumn that causes Horton runoff. Rainfalls of 400–600 mm in a single episode are common in the Mediterranean and, at times, in the Atlanticarea (Martın-Vide & Olcina 2001). However, extended dry periods up to 160 days are also common in some areas. Consequently, runoff coefficients range from 16% in some Mediterranean areas to >50% in the Atlantic region. Rivers of the Iberian Peninsula can be separated by those flowing to the Atlantic and those flowing to the Mediterranean. The separation between these two large basins is asymmetrical with the Mediterranean basin encompassing 182 661 km2 (31% of the total surface area) and the Atlantic 400 839 km2 (69% of the surface area) (Teran & Sole Sabarıs 1978). The largest rivers flow to the Atlantic and include the Duero, Tagus, Guadiana, and Guadalquivir. The Ebro is the only large river in the Iberian Peninsula that flows into the Mediterranean (Figure 4.1, Table 4.1).

Central Plateau (Mesetas). There is also large spatial variation in rainfall, which decreases from north to south and from west to east. Therefore, the Iberian Peninsula can be divided into arid, humid, and semi-desert areas. The division between the humid and arid areas is established at the precipitation isoline between 600 and 800 mm/year, while that between the arid and semi-desert area is 300–350 mm/year (Martın-Vide & Olcina 2001). The humid area (1000–2000 mm/year) not only occupies the north, but also includes many mountain ranges within the Iberian Peninsula. The arid area is the largest, as it includes the Meseta, Ebro and Guadalquivir depressions as well as the Mediterranean littoral area. The semi-desert zone is small and constrained to the southeast. Interannual variability in rainfall is high, being most pronounced in the arid and semi-desert areas. This variability is >20% inthe Mediterranean front and upto40% in the southeast of the Peninsula (Martın-Vide & Olcina 2001). Those basins showingthe highest variability are the Seguraand Guadalquivir TABLE 4.1 General characterization of the Iberian Rivers

Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature (C) Number of ecological regions Dominant (25%) ecological regions Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparce vegetation Wetland Freshwater bodies Protected area (% of catchment) Water stress (1–3) 1995 2070

Ter

Ebro

J ucar

659

770

817

Segura Guadalquivir Guadiana Tagus 644

566

3010 85362 21208 19182 57527 0.83 13.41 0.81 0.82 7.22

504

599

Mondego Duero

Ag€ uera

391

358

874

67048 80600 6670 6.18 9.93 3.10

97290 13.56

145 0.10

78.6

67.2

44.8

39.8

52.1

53.2

59.9

93.7

66.5

106.0

11.7 2

11.4 6

13.1 3

14.4 3

15.5 3

15.2 4

13.8 4

14.4 3

11.4 4

11.7 1

48

37

37

37

37; 66

37

37

12; 50; 66

37; 50

12

2.6 30.0 1.1 50.3 14.3 1.1 0.0 0.6

0.6 47.1 1.9 22.3 25.5 2.7 0.1 0.6

0.7 51.6 0.0 17.2 29.8 0.3 0.0 0.4

1.7 53.4 0.0 14.6 24.9 4.9 0.2 0.3

1.1 62.0 0.0 12.8 20.9 1.6 0.8 0.8

0.6 68.4 0.1 7.8 21.8 0.2 0.2 0.9

1.7 45.6 0.3 21.5 28.8 0.8 0.0 1.0

1.9 33.4 0.1 38.2 23.9 1.8 0.2 0.5

0.7 55.1 1.0 17.5 23.5 1.8 0.0 0.4

0.2 7.3 14.6 48.8 24.4 4.7 0.0 0.0

2.0

3.2

0.1

4.9

15.8

3.5

2.2

10.8

1.2

0.0

1.7 2.3

2.9 2.9

3.0 3.0

3.0 3.0

3.0 3.0

2.9 2.9

2.9 3.0

1.5 1.6

2.0 2.9

2.0 2.0

Fragmentation (1–3) 3 Number of large dams (>15 m) 3 Native fish species 6 Nonnative fish species 9 Large cities (>100 000) 0 108 Human population density (people/km2) Annual gross domestic 20 387 product ($ per person)

3 70 27 20 5 34

3 13 19 11 1 207

3 15 3 4 1 78

3 55 22 7 3 69

3 87 29 13 0 24

3 72 23 10 2 136

3 3 12 7 0 96

3 75 21 13 5 37

2 0 4 ? 0 36

19 587

14 873

13 782

12 994

12 303

13 818

8550

15 058

19 055

For data sources and detailed explanation see Chapter 1.

Chapter | 4 The Iberian Rivers

FIGURE 4.1 Digital elevation model (upper panel) and drainage network (lower panel) of the Iberian Rivers.

115

116

This apparent asymmetry is caused by the structure and geology of the Iberian Peninsula. The central plateau (Meseta) is tilted to the west and the Iberian Range delimits its east border. As a consequence, waters flowing to the Atlantic follow the tilted plain of the Meseta: Duero to the north, Tagus and Guadiana to the south. The orography of the Meseta determines the length and fluvial character of the rivers, with the Atlantic rivers being longer and lower gradient than the Mediterranean rivers. These rivers tend to be torrential and irregular, producing devastating floods in autumn and droughts in summer. Rivers flowing from the Cantabric Range are quite short, but transport large amounts of water because of high rainfall. Water from the Pyrenees feeds the large river Ebro, while those of the Bethic Mountains feed the Guadalquivir. The variation in orography and climate also influences the different flow regimes of Iberian rivers. Rivers of the Pyrenees have a nival regime with a maximum in spring and a relatively constant flow in summer. Mediterranean rivers have a rainfall-based flow regime with maxima in spring and autumn and a minimum in summer. Rainfall-fed Atlantic rivers have much higher inputs with a slight decrease in summer flow. Because of the length and complexity of the landscape, flow regimes of some rivers also can vary. For example, headwaters of the Ebro are in the karstic area of Fontibre with an Atlantic influence. Downstream in the Ebro Depression, the flow regime progressively shifts to a Mediterranean type. The lower Ebro has a pluvio-nival flow regime after rivers from the Pyrenees enter the system. The geology of the Iberian Peninsula is complex and affects the biogeochemistry of its waters. In general, the west is siliceous and the east is sedimentary and calcareous. Armengol et al. (1991a) characterized four types of waters based on total dissolved solids (TDS) and ionic composition. Western water bodies draining igneous geology have low TDS and high levels of sodium and potassium relative to calcium and magnesium. Eastern waters, for example systems in the Ebro and Duero catchments, have moderate TDS and are high in bicarbonates. A small group of waters in the southeast in the J ucar and Segura basins are high in sulphates and TDS. Finally, a small number of waters in the southwest have the highest TDS values and high chloride concentrations. Human influence on water ecosystems has a long history in the Iberian Peninsula; for example there are remnants of hydraulic structures built by the Romans and the Arabs. In recent times, water scarcity in systems with irregular flow regimes has resulted in the construction of dams and canals, resulting in the regulation of many Iberian rivers. Over 1000 reservoirs have been built along most of the large rivers. Large rivers in the northwest, however, are less regulated. Some rivers have been interconnected, allowing interbasin transfer of biota and endangerment of sensitive species. Many rivers, especially those in the arid region, are dependent on groundwater. This has particular relevance in future climate scenarios that predict base flows to decrease and the number of temporary systems to increase (Alvarez Cobelas et al. 2005).

PART | I Rivers of Europe

4.2. THE GUADIANA The Guadiana derives its name from the Roman Anas or Ana with the addition of the prefix Guadı (river) by the Arabs. Although the Guadiana is the smallest of the large rivers in the Iberian Peninsula, it is remarkable for the nature of its drainage network and flow regime. Because of the porosity of its substrate and a moderate rainfall in the catchment, groundwater plays an important role in river flow. The catchment also has high human impacts that influence its flow regime, water chemistry, riparian vegetation, and biological communities (Photo 4.3). The Guadiana catchment is wide and flat, and its flow is derived only from rainfall. Most of its headwaters are in the Meseta and are of low gradient. The Guadiana catchment covers 67 048 km2 and most lies in the driest area of the Meseta. Because of the high permeability of the limestone bedrock, rainwaters disappear quickly from the surface and form large underground aquifers. The river has a highly variable flow regime. Where the chalk and limestone are interrupted by an impervious layer, springs originate and are characteristic of the Guadiana hydrography. The river is unconstrained for most of its 818 km, being constrained partly in the Campos de Calatrava and later when entering Portugal. The river drops by only 1 km from the headwaters to the mouth. The Guadiana originates from a diffuse number of tributaries, and thus the primary source is still under discussion. The main headwater tributaries include the Zancara, Gig€uela (or Cig€uela), Jabalon and Zujar. The lower tributaries, Bullaque and Estena, drain the Toledo mountain range and originate in Cabaneros National Park. They are some of the best conserved in the entire Guadiana basin. The Gig€ uela contributes the most flow in the upper Guadiana, while the Zujar has the highest flow in the catchment. The lower Guadiana has a number of short streams with highly unpredictable flows. Particularly important is the Vasc~ao because of its good condition in an area where most flowing waters have been seriously altered by humans. Human impacts in the catchment are mostly related to agricultural practices that use a large number of wells and reservoirs. The Guadiana catchment holds the largest man-made lake in Europe, the Alqueva reservoir in Portugal, with water storage of 4.15 km3. The catchment has a high water deficit, indicating a scarcity of water for aquatic biota.

4.2.1. Historic Changes and Human Impacts By the end of bronze era, the southwest Iberian Penınsula had its own identity with several fortified villages along the lower Guadiana. Here, the Tartessos kingdom was the first political entity of Iberia. This area was later occupied by Phoenicians (7th century BC), Greeks (6th BC) and then by Carthaginians and Romans because of its high metal abundance. For example, San Domingos mine has been in use intermittently for >2000 years. Mertola, several km upstream of the Guadiana

117

Chapter | 4 The Iberian Rivers

PHOTO 4.1 Guadiana at Pulo-do-Lobo (Photo: Manuel Gra¸ca).

mouth, was an important port during the Arabic period with evidence of Greek and Jewish merchants and Berber warriors. Badajoz, with 3000–5000 habitants, was an important Arab city in the 10th–11th century, replacing Merida as one of the most important cities in the south.

4.2.2. Biogeographic Setting The Guadiana mostly flows through the Meseta highlands (600 m asl on average), an area of primary materials partly covered by tertiary sediments (Teran & Sole Sabarıs 1978). The southern Meseta geology consists of: (1) the original primary materials in the west, (2) the Toledo Mountains in the north, (3) an interior depression, later filled by Tertiary deposits, limestones and gypsum, and (4) the northeast Iberian Range made up of Mesozoic materials.

The Meseta was formed by Alpine foldings that created mountain ranges on each side and caused its western tilt. During this Alpine forcing, Tertiary depressions were separated from the sea and erosion of the surrounding ranges contributed sediment materials to the depression. Most of this process was completed during the Miocene. The sediment layer is 300 m on average; the lower layers are sands and silts and the upper layers are gypsum and limestones. Finer materials were deposited in the centre of the depression, whereas more gypsum, limestones, and halites are found in the east.

4.2.3. Physiography, Climate, and Land Use Schists, gneisses and granites constitute the Paleozoic bedrock of the upper Guadiana basin. There are a series of

118

Triassic, Jurassic, Cretaceous and Tertiary detrital and carbonate materials covering the bedrock. In Portugal, deposits of alkaline meta-sedimentary and meta-volcanic sediments occur along with acidic areas of Cenozoic sediments. Climate in most of the Guadiana basin is Continental Mediterranean with cold winters, low rainfall, and long dry summers. Low winter temperatures may last for nearly two months, an unusual phenomenon for a Mediterranean climate. Summer temperatures are high but humidity is low. The annual range in air temperature can be nearly 50 C, and diel temperature variation in summer can be 20 C. Mean annual rainfall is 400 mm, mostly occurring during winter and spring. The catchment is mostly dedicated to agriculture, which is highly dependent on irrigation. In 2002, there were >350 000 ha irrigated in the catchment with 57% relying on phreatic waters. Irrigation has decreased the phreatic level in recent times, surpassing the renewal capacity of these waters by 300 Hm3 per year. There are over 60 847 wells being used in the catchment. Most of the catchment in Portugal is covered by cork-oak forest and Mediterranean shrubland, and has a low human density (230 000 inhabitants; 20 inhabitants/km2). Industry is scarce with some olive processing plants and pig farms.

4.2.4. Geomorphology, Hydrology, and Biogeochemistry The total drainage network of the Guadiana equals 33 707 km with an annual discharge of 6168 Mm3. Regardless, many sections of the river, the upper catchment in particular, are intermittent, especially in summer. Rivers in the upper catchment are closely interconnected with underground aquifers. The combination of low rainfall and high evaporation causes flows to be typically low. In fact, most waters in the upper catchment infiltrate as groundwater and form four large aquifers (Fornes et al. 2000). The largest (5500 km2 surface area) is the West Mancha aquifer (Number 23). Formerly, the outflow from this aquifer was the ‘Ojos del Guadiana’ (Guadiana’s Eyes) in the La Mancha plain (608 m asl). Here a number of diffuse springs emerged that were considered the ‘real’ Guadiana headwaters, but which vanished >30 years ago. Today, surface waters of the Guadiana originate from karst formations in the Montiel range. These waters form the Ruidera lakes (15 in total) and have a high carbonate load. Water levels in the lakes are associated with rainfall in the upper mountains, having a delay time of 4–6 months. These small lakes are interconnected by a series of small waterfalls and by subsurface flow. The first lake in the series is La Blanca (White Lake after the white-coloured carbonate precipitates). Colgada is the largest lake (100 ha surface area), while the others range from 12 to 38 ha. Water depths in the lakes range from 8 to 19 m. The lower lakes become progressively shallower and are covered by emergent macrophytes. The Penarroya reservoir collects

PART | I Rivers of Europe

the waters from Ruidera, but water infiltrates and the river disappears for the first time. Fifty kilometres downstream are found the Tablas de Daimiel, a group of large shallow ponds and swamps that is susceptible to flooding because of the low gradient. This wetland covers an area of 1712 ha, is rectangular in shape, and consists of small lacustrine openings with islands and palustrian vegetation of fens, reeds and rushes. Although originally fed by the Gig€uela and aquifer 23, the wetland now obtains water from other watersheds because of aquifer depletion. From the Tablas, the Guadiana flows west and then south through La Mancha plains, penetrating the Toledo range. Downstream, the Guadiana is dammed, forming Cıjara reservoir. It is the first of three reservoirs (Cıjara, Garcıa de Sola and Orellana) that are later joined by Zujar reservoir on the tributary Zujar. Further downstream, the Guadiana enters the Alto Alentejo in Portugal with a hercinic substrate partially covered by quarternary and tertiary deposits. The river alternates between waterfalls (e.g. the 16 m high Pulo do Lobo waterfall) and unconstrained reaches with slopes <5%. The Guadiana at Merida has an average discharge of 157.4 m3/s, but ranges between 2.2 and 463 m3/s. The Guadiana mouth forms a small delta in the estuary, where small islands alternate with sandbars. Because of the low elevation, tidewaters can reach Mertola about 70 km upstream from the mouth. Brackish waters dominate only from Alcoutim to the mouth, and there are several marshes. Tributaries are commonly dry during summer and some even in winter. The Gig€uela at Tablas de Daimiel has an average discharge of 57.1 Mm3/year (1995–2001), with maxima in February and minima in winter and summer (CH Guadiana 2002). The Zancara has a maximum flow of 2.4 m3/s, whereas the Zujar is regulated and discharge ranges between 2.9 and 66.5 m3/s. Water transparency is high in the Guadiana headwaters, in particular in the upper ponds of Ruidera. Suspended solids in this area reach 4.8 mg/L, but quickly increase downstream because of inputs of sediments, treated wastewaters, and agricultural and urban runoff. Reservoirs reduce suspended solids in the river. Pools are frequent along the river and often have dense phytoplankton communities, including cyanobacteria, which increase water turbidity. At the mouth, the concentration of suspended solids is 38 mg/L, but can reach 84.6 mg/L at Sanlucar de Guadiana. Water conductivity is high (1000 mS/cm) in the headwaters as well as in Zancara and Zujar because of the calcareous substrate. Conductivity of the Gig€uela and the Tablas is also high (1400–2400 mS/cm, locally reaching 8000 mS/cm). In the Zancara and Gig€uela, conductivity can reach 3000 mS/ cm. Water conductivity decreases downstream because of inputs from poorly mineralised springs and chemical changes in the reservoirs (CH Guadiana 2002). Conductivity values of 490–550 mS/cm have been recorded in the Alqueva reservoir, and the tributaries Xevora, Vasc~ao, Ardila and Degebe in Portugal have conductivities of 350–400 mS/cm.

Chapter | 4 The Iberian Rivers

Pollution, indicated by high ammonia levels, is occasionally detected below wastewater treatment plants and from direct inputs of wastewater. Dissolved phosphorus is high in some areas downstream of large cities. Nitrate is higher in winter as a result of increased runoff; whereas ammonia and phosphate have higher values during summer during low flows. Organic and inorganic contaminants are rarely recorded in the Guadiana (CH Guadiana 2002), their occurrence being related to the agricultural land use. Tributaries flowing through villages, farms and agricultural lands in the lower Guadiana (i.e. Olivenza, Ardila and Asseca) receive high pollution loads. In summer, the combination of low flow, high temperature and high nutrients, particularly phosphates, results in periodic blooms of Cyanobacteria or Azolla. Cyanobacteria blooms usually occur in the estuary at the end of summer, and the sediment load into the estuary ranges between 58 and104 m3/year.

4.2.5. Aquatic and Riparian Biodiversity Planktonic development in the Guadiana mostly occurs during low-flow periods in the main channel as well as in several reservoirs in the basin. Blooms of the Cyanobacteria Microcystis aeruginosa, Aphanizomenon flos-aquae, Oscillatoria spp. and Anabaena spp. have been recorded during summer and early autumn in the river. Recent construction of the Alqueva dam has modified the hydrology of this river reach, causing more Cyanobacteria blooms (Sobrino et al. 2005). Before construction (1996–1998), phytoplankton in the river was dominated by chlorophytes (e.g. Pediastrum spp.), diatoms (Aulacoseira granulata, Melosira spp.) and cyanobacteria (Chroococcus spp. and Microcystis spp.). The lacustrine environment of Tablas de Daimiel and Ruidera lakes causes a well-developed planktonic community. In Ruidera lakes, the most common taxa were Cyclotella ocellata, C. kuetzingiana, Rhodomonas minuta, Cryptomonas erosa and Peridinium umbonatum (Bort et al. 2005). Planktonic chlorophyll-a concentrations ranged from 1 to 8 mg/L in the lakes. In the Tablas, massive growths of the cyanobacterium Planktothrix agardhii occur in summer, the diatom Cyclotella meneghiniana in spring, and the chrysophycea Ochromonas in winter (Lionard et al. 2005). Benthic diatoms are distributed according to the physiography and water chemistry of the Guadiana (Urrea & Sabater 2008). In calcareous tributaries, the diatom community is dominated by Cymbella taxa (C. affinis, C. microcephala, C. cymbiformis, C. minuta). In tributaries with siliceous substrata, the diatom community is dominated by Tabellaria flocculosa and Anomoeoneis vitrea. In eutrophic waters, the diatoms Navicula atomus var. permitis, Nitzschia acicularis, N. capitellata and N. umbonata dominate. Aquatic vegetation (submergent and emergent) is highly abundant in several areas, and especially in Ruidera and Tablas. In the upper Ruidera lakes with transparent, good quality waters, occurs an abundance of submergent vegeta-

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tion. In the lower lakes, the water is less transparent because of sediment inputs and mostly emergent macrophytes are found. In Tablas de Daimiel, shallow and littoral areas are inhabited by several charophytes as well as other macrophytes. Cladium mariscus has an extensive development in the Tablas, probably more than in all of Occidental Europe. Riparian forests in saline soils of the Tablas are dominated by Tamarix canariensis, while Populus alba develops in less saline areas. In the river where water flow is low, helophytes such as Phragmites sp., Typha sp. and Arundo donax are common. In the estuarine zone, aquatic vegetation is mostly dominated by the invasive Arundo donax. Nerium oleander is a characteristic plant in extreme dry channels with stone substrate that are subject to floods. In headwaters of the Gig€uela, there are a few populations of the native crayfish Austropotamobius pallipes. Plecoptera, Ephemeroptera and Trichoptera, which are normally associated with running waters, are relatively less abundant in the Guadiana than in the other large Iberian Rivers. Even so, four groups of Ephemeroptera are locally abundant in the Guadiana and its tributaries (Baetis sp., Cloeon sp., Choroterpes sp., and Caenis sp.) along with Chironomidae, Simulidae and Hydropsyche sp., and the shrimp Athyaephyra desmarestii all feeding on fine particulate organic matter. The fish fauna in the lower basin is dominated by Leuciscus alburnoides and Barbus steindachneri. Some 85 km upstream from the mouth, there is a natural barrier that impedes fish migration, apart from eels (Anguilla anguilla), except during high flows. In this section, three other migratory fish also are found: Alosa alosa, A. fallax and Petromyzon marinus. The sturgeon Acipenser sturio was once present in the Guadiana, but the last specimen was caught in the early 1980s and it is now considered extinct. The Guadiana River holds the largest number of Iberian endemic fish in the Iberian Peninsula (13 out of 42 species, including introduced fishes). Some areas of the Guadiana, in particular the Tablas and streams of Cabaneros National Park, have a high diversity of fishes. The endemic Jarabugo, Anaecypris hispanica, is a small ciprinid (<6 cm in length) restricted to the Guadiana and Guadalquivir. Its habitat is limited to small slow streams with abundant submerged vegetation. Other notable endemics in the Guadiana include the Iberian barbel Barbus comiza (also present in the Tagus), Barbus microcephalus, the Pyrenean chub Leuciscus pyrenaicus, and the Iberian nase Rutilus lemmingii. Tropidophoxinellus alburnoides (Calandino), found in the Bullaque and Estena rivers in Cabaneros, is a hybrid between L. pyrenaicus and another extinct species. In fact, all T. alburnoides are females and they require the sperm of the Pyrenean chub to reproduce. Other endemics found in the upper and middle Guadiana include Chondrostoma lemmingii, Squalius alburnoides, Squalius pyrenaicus, and Cobitis paludica. A total of 15 species of reptiles and amphibians have been described from the lower Guadiana catchment. The most remarkable species are the water lizard, Lacerta scheibreri, water snakes (Natrix natrix and N. maura) and the

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tortoise Emys orbicularis, which have some of the largest populations in the western Iberian Peninsula. The Guadiana hosts a large number of palustrian birds, especially in the less-disturbed lakes of the Ruidera and Tablas, and also in the middle Guadiana and the estuary. The Tablas is an important nesting area for the red-crested pochard. The otter is now common in Ruidera as well as in some sections in the lower river and tributaries.

4.2.6. Management and Conservation Management problems in the Guadiana catchment are mostly related to the scarcity of water in the face of high water demands. The better-protected areas are in constrained sections in Portugal and in the upper Guadiana (Ruidera and Tablas de Daimiel) along with streams having poor access. The upper Guadiana suffers from water resource exploitation. A progressively greater water abstraction in the 60s and 70s caused aquifer 23 to level off at <35 m (Bromley et al. 2001), and a pumping rate >2/3 of the maximum historical rate (400 Mm3/year) was found unsustainable (Fornes et al. 2000). Aquifer 23 was officially declared overexploited in 1994, and complete recovery would require the total cessation of water extraction for 5–15 years or at least the implementation of sustainable irrigation practices (Bromley et al. 2001). Regulations are difficult to enforce because of resistance by farmers that use irrigation for crops. Other impacts to the river are related to water extraction (Fornes et al. 2000). For example, groundwater depletion has sharply decreased surface flows in the Guadiana, Zancara and Gig€ uela over the last 30 years (Alvarez Cobelas 2006). This is particularly noticeable during dry periods in the upper Guadiana. The drying of several km of the upper Guadiana over 15 years caused severe damage to riparian forests. Here the water table was lowered by 30– 40 m below the river channel, the river flowing only in a wet period in 1995/1996. Historically, wetlands covered 250 km2 of the catchment, but only 70 km2 remain today. Most wetlands were drained for agricultural lands. Some wetlands are now on the RAMSAR list or have been classified as National or Regional Parks. In 1981, UNESCO designated the Tablas de Daimiel wetlands as a Biosphere Reserve due to its ecological importance. The Tablas de Daimiel is now a National Park and is an area of special concern under RAMSAR and ZEPA agreements. The declaration of Tablas de Daimiel as a National Park forced an emergency resolution to conserve its aquatic habitats, in which 30 Mm3 per year is diverted from Tagus-Segura to Guadiana-Gig€ uela and, therefore, to the Tablas. In the middle and lower Guadiana, human impacts are expressed in the poor state of river habitat and riparian vegetation. A river survey evaluating riparian vegetation, estimated that about 80% in the Gig€ uela, 94% in the Zancara, 8% in the Z ujar and 15% in the Guadiana were in a poor or degraded condition (CH Guadiana 2002). In many areas,

PART | I Rivers of Europe

especially in arid lands, riparian vegetation practically does not exist because land use extends to the riverbanks. In the lower river, the ‘Castro Marim’ salt marsh is a Natural Reserve encompassing 2090 ha of tidal influenced land. It is an important nursery area for fish, molluscs and crustaceans and habitat for large birds including storks and flamingos. The Guadiana is a highly regulated river. In Spain, the Guadiana has 86 reservoirs >1 Mm3, with an overall retention capacity of 9114 Mm3 (CH Guadiana 2002). In Portugal, 13 dams have been built on the Guadiana basin, the largest being Alqueva. When completely filled, the Alqueva will be the largest reservoir in Europe, covering an area of 250 km2 and (among other consequences) will threaten the habitat of the few remaining Iberian lynxs.

4.3. THE GUADALQUIVIR The Guadalquivir derives its name from the Arabic word wadi al-Kabir (‘large river’), whereas the Romans named it Betis. The catchment area of the Guadalquivir is 57 527 km2. The catchment includes a well-defined geographical depression, bounded by the Sierra Morena range in the north, the Bethic range in the south, and the Atlantic Ocean in the southwest. Most of the Guadalquivir network (90.2%) drains through Andalucia, with smaller tributaries draining parts of Castilla-La Mancha, Murcia and Extremadura. The Guadalquivir has a complex catchment, resulting from the orography and configuration of the depression and surrounding mountain ranges. The Guadalquivir headwaters are in the Canada de las Fuentes at 1350 m asl in the Cazorla range. The river flows southwest, merging with the Aguascebas on the left and further downstream with its largest tributary Guadiana Menor (area 7251 km2), and then Guadalbullon. The Genil enters the lower river and has a catchment 8278 km2. The headwaters of the Genil are in Sierra Nevada and it later flows through the city of Granada. After Guadiana Menor, the Guadalimar enters from the right, and further downstream enter Jandula, Yeguas and Genil from the left and Bembezar from the right. In the lower river, Guadiamar and Arroyo de la Rocina (from Donana National Park) enter from the right and Corbones, Rivera de Huelva and Guadaira from the left. The middle and lower Guadalquivir flow through large cities such as Cordoba and Sevilla, and is navigable to the mouth. In the estuary, the river divides into several arms and forms a marsh called Marismas del Guadalquivir with Donana National Park to the west. The Guadalquivir enters the Atlantic Ocean by the city of Sanlucar de Barrameda, a historical trade harbour between Spain and America.

4.3.1. Historic Changes Agriculture, forestry and mining have a long history in the catchment. Early signs of mining (silver and copper) date back to 3000 BC. Mining was intense during the Phoenician

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Chapter | 4 The Iberian Rivers

PHOTO 4.2 Guadalquivir River at Cordoba (Photo: Sergi Sabater).

and Roman periods, and again in the 19th century. Copper and silver attracted the Romans, who also tended olives and vineyards. Humans have caused major alterations in vegetation and land use; especially visible in the landscape of Jaen and Cordoba. A former landscape of evergreen oaks (Quercus rotundifolia Lam.) is now replaced by olive trees and other extensive crops. The natural vegetation has been reduced to small areas.

4.3.2. Biogeographic Setting Although variable, a Mediterranean climate influences the entire catchment. Well-preserved patches of evergreen oak forest are found in Sierra Morena, in protected areas of Sierra de Aracena and Picos de Aroche (Huelva), Sierra Norte in Sevilla and Sierra de Hornachuelos (Cordoba). On siliceous and more humid soils grow cork oak Quercus suber, forming a dense forest, especially in the GuadaleteBarbate, Sierra Morena and Aljibe ranges. In drier areas, pines (Pinus halepensis) grow, especially in lowlands of the Bethic range and in the Guadiana Menor basin. Climate variation in the catchment is also evident by the presence of Andalusian fir (Abies pinsapo), an endemic species that thrives in a few humid areas having shade and moderate temperatures.

4.3.3. Physiography, Climate and Land Use The Guadalquivir catchment has three main physiographical units: the Sierra Morena range, the Bethic range, and the Guadalquivir valley. The northern Sierra Morena is 400 km long and has an east–west formation that abutts the Meseta bedrock. Paleozoic bedrock rises in the north with some mountains >1000 m asl (Sierra Madrona; 1323 m asl; Almaden; 1107 m asl, Aracena; 912 m asl). The southern part of the range determines the flow direction of rivers with constrained channels in a saw-like landscape. The Cambric carbonates of Cazorla and Sierra Morena have important subterranean aquifers. In this area, cattle predominate because of limited agricultural soils and low human density (18 inhabitants/km2). The area has a high annual rainfall that gradually decreases towards the east. The catchment contains a number of small lakes and wetlands (Guerrero et al. 2006). The Bethic range in southeast of the catchment is one of the largest geologic structures on the Iberian Peninsula. Orogenic activity caused deep limestones and marls to be folded in two parallel ranges (the Prebethic and Subbethic ranges) with an intermediate depression (the Penibethic Depression) in between. The same activity formed the Guadalquivir Depression. The Guadalquivir has its headwaters in the Prebethic range. The headwaters of the Genil and the Guadiana

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Menor are in the Penibethic Depression. High erodibility and estepary vegetation in this region allow gully-type watercourses in the Genil and Guadiana Menor watersheds. These rivers drain the widest and better-preserved badland landscape of the Iberian Peninsula (Teran & Sole Sabarıs 1978). The Guadalquivir Depression is a wide triangular plain (150 m asl on average, 330-km long, 200-km wide in its lower part) with an Atlantic influence. The Depression was formed after the Alpine foldings and later filled with Tertiary marine sediments. Gentle hills are the predominant landform in the Guadalquivir Depression. Most of the Guadalquivir catchment is characterised by a warm temperate (Mediterranean) climate with mild temperatures (annual average 16.8 C) and a relative paucity in rainfall (annual average 630 mm). In the Guadalquivir Depression, maximum summer temperatures may reach 50 C (average is 40 C) and is one of the warmest areas of the Iberian Peninsula. In the north, the Sierra Morena has average annual temperatures between 14.5 and 16.5 C, while air temperatures range between 11.5 and 14 C in the Cazorla range. Lowest temperatures occur on north slopes of the Sierra Nevada and in the Genil headwaters, which are snow-covered during winter. Frost is rare, except in the Bethic range, and day light totals 2500–3000 h per year. A characteristic of the Guadalquivir climate is dry summers (rainfall <10 mm), and wet winters. The openness of the catchment to the Atlantic Ocean allows the influence of western storms that create a southwest/northeast gradient in rainfall with highest rainfall in the mountains (up to 1700 mm in Aracena and Cazorla). Rains are highly irregular and usually torrential, typical of the Mediterranean regime. High rainfall also occurs in mountains of the Sierra Nevada that are exposed to the Mediterranean. This Ocean influence causes more rainfall in Guadalquivir than in the nearby J ucar and Segura catchments. Minimum rainfall, around 300 mm annually, occurs in the Bethic highlands.

PART | I Rivers of Europe

the Genil, flows range from 0.0 to 3342 m3/s. The usual low flow in summer can also extend into other periods of the year such as in 1990–1991 when flow was nil for most of the year (Figure 4.2). The middle and lower Guadalquivir have conductivities between 700 and 1400 mS/cm with values decreasing in summer (May-September). The Genil and Guadaira have the highest conductivity of the Guadalquivir tributaries (CH Guadalquivir data), averaging 2163 670 mS/cm in Guadaira from 1994 to 2005. The Guadaira is saline in its headwaters because of high evaporation. In the estuary, water conductivity is highest in May–September because of a marine influence. Freshwater inflow in the lower river is strongly regulated by the Alcala del Rıo dam about 110 km from the river mouth. In this section of the river, water temperature is >22 C from May to October and can reach 26 C in July. Minimum average temperatures are 12 C in December–January. Water quality of the Donana marshs is influenced by sediment deposition, eutrophication and heavy metal pollution. In particular, the eastern Donana is affected by low quality incoming water and a general increase in nitrate has been detected in the marsh (Serrano et al. 2006).

4.3.4. Geomorphology, Hydrology and Biogeochemistry The floodplains of most rivers in the Guadalquivir catchment have been transformed into agricultural land. Lateral arms, meanders and wetlands have been channelized or drained and converted into agricultural land such as rice fields and orchards. Just recently, an extensive riparian corridor has been restored in the catchment (Marın Cabrera & Garcıa Novo 2005). The Guadalquivir has a highly variable flow regime. Runoff coefficients range from 15% in the Guadiana Menor and Jandula to 24% in the Genil and 29% in the Corbones. Annual discharge in the Guadalquivir is 7230 Mm3 (229 m3/s). The Genil and Guadiana Menor contribute 29.4 and 15.7 m3/s, respectively. Discharge in the lower Guadalquivir ranges from 0.09 to 1640 m3/s. At the confluence with

FIGURE 4.2 Long-term discharge patterns of selected Iberian Rivers.

Chapter | 4 The Iberian Rivers

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Some tributaries transport large concentrations of suspended solids associated with the high erosion and aseasonal runoff. This effect is particularly evident in rivers draining the left side of the catchment and those of the Sierra Morena. For example, average suspended solids in Guadiana Menor were 1064 6046 mg/L in 1994–2005, with maximum values >50 000 mg/L in spring and fall. Lowest suspended solids occur in the tributaries from the right side of the catchment and those in Sierra Nevada. In the main river, TDS range between 60 and 800 mg/L, but values may reach 3600 mg/L in certain areas and times of the year. Some areas in the Guadalquivir catchment contribute major inputs of industrial and, especially, urban effluents. The most effected tributaries and reaches are the Guadiel (at Bailen), Guadalbullon (receiving the waters from Jaen), Guadaira, Genil (downstream of Granada), Guadalete (at Jerez), and Guadalquivir (downstream of Cordoba and Sevilla). For example, the Genil had average values of 4.24 6 mg/L PO4 from 1994 to 2005. In areas with intensive agriculture and farming (irrigated crops and livestock), high nitrate concentrations (from 20 to 67 mg NO3 L 1) characterize surface and ground waters (Figure 4.3). Olive pressing produces a residue called alpechin that constitutes one of the major organic pollutants in the catchment. Alpechines cause high levels of nitrate, ammonia and phosphate in receiving waters. The effluents of alpechin in Andalusia in the past were equivalent to 6.3 million inhabitants, but this presently has been reduced with the introduction of novel environmentally friendly technologies.

4.3.5. Aquatic and Riparian Biodiversity The Donana marshes are distinct from the estuary and could be considered as an interior delta. The marshes are a wide, open area, covering 27 000 ha with an impermeable clay substrate that retains rainwater. The hydrology of the system is complex, with a 6-month receiving/storage period, followed by 2 months water retention from flooding, then a dry period in summer (Garcıa Novo et al. 2007). The hydrology influences the water chemistry of the various water bodies over time (Montes et al. 1982). A marine influence is limited to small areas. The area also is geomorphologically diverse with permanent waters (lucios or round ponds), river channels and inundated shallow but temporary marshes. The marshes retain a high biodiversity. The Donana host a cosmopolitan flora of diatom and filamentous algae. Planktonic communities are made up of nanoplankton, in which flagellates and euglenales are most common. Also common are iron-fixing taxa such as Tribonema, Trachelomonas, Oedogonium and Bulbochaete (Margalef 1977). The presence of Anabaenopsis is related to nitrogen-limited waters. Salinity is associated with the presence of Nodularia (Cyanobacteria), and Cylindrotheca, Nitzschia, Chaetoceros and Campylodiscus (Bacillariophyta). Crustaceans are the most abundant

zooplankton (Marın Cabrera & Garcıa Novo 2005) with Diaptomida at 13 taxa, Cladocera at 50, and Rotifera at 80 taxa. Zooplankton communities are, in general, made up of circum-mediaterranean taxa, some of them with a North African distribution (Diaptomus kenitraensis, Copidiaptomus numidicus, Hemidiaptomus maroccanus). The diaptomid Dussartius baeticus and rotifer Lecane donyanensis are local endemics (Marın Cabrera & Garcıa Novo 2005). The isopod Asellus coxalis and ostracod Isocypris beauchampi are particularly special taxa to these waters. The estuary is also an important breeding and nursery ground for many marine species.

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PART | I Rivers of Europe

The rivers Tinto, Odiel, and Guadiamar contribute high levels of heavy metals to the estuary and its sediments (Cabrera et al. 1987) that directly influence its flora and fauna. These rivers drain a major part of the Iberian pyrite belt, a massive sulfide deposit in southern Spain and Portugal (van Geen et al. 1999). The estuary is inhabited by iron-oxidizing bacteria, sulphur-oxidizing bacteria and filamentous fungi (Lopez-Archilla & Amils 1999). Their activity causes high concentrations of iron, copper, zinc and lead in the water. In spite of the acidity of the waters, a luxurious algal community and various animals inhabit the river (Sabater et al. 2003). Riparian vegetation along permanent channels of the Guadalquivir is somewhat independent of the local climate, providing a higher humidity even in dry areas. Willows (Salix atrocinerea, S. alba) and aspens (Populus nigra), as well as other deciduous trees, are common riparian vegetation. A large number of Ephemeroptera taxa is found in the upper Guadalquivir, (Alba-Tercedor et al. 1992). In the headwaters of the Genil, Coleoptera, Trichoptera and Ephemeroptera are common. In seasonally dry rivers with permanent flowing sections, there is an even balanced assemblage of Ephemeroptera, Coleoptera, Trichoptera, Odonata and Heteroptera. In periodically dry rivers, the channel comprises a series of ponds (such as those occurring in the Guadaira), and lentic species of Coleoptera are most common (Alba-Tercedor et al. 1992). Small streams, particularly in the Sierra Morena and Bethic ranges, are open-canopied and temporary, causing initial heterotrophic conditions to shift to autotrophy (Molla et al. 1994). Flow regulation can affect the life cycles of macroinvertebrates in the Guadalquivir. For instance, significant changes in the diet of the mayfly Rhyacophila nevada were related to changes in flow hydrology that altered resource availability (Bello & Alba-Tercedor 2004). The red-swamp crayfish (Procambarus clarkii) was introduced to Guadalquivir marshes in 1973 for commercial reasons, and is now a common invader in Iberian waterbodies, especially in the south. The increase of this invader coincided with a decline in the native white-clawed crayfish (A. pallipes). It was observed that P. clarkii inhabits the lower and middle reaches of rivers up to 820 m asl, whereas the native whiteclawed crayfish inhabits the upper reaches and may persist following invasion (Gil-Sanchez & Alba-Tercedor 2002). There are 29 fish species in the freshwater reaches of the Guadalquivir, and the Iberian chub (S. pyrenaicus) is an Iberian endemic. This species is found in central and southern catchments of the Iberian Peninsula (Doadrio 2001), inhabiting all kinds of flowing waters. S. pyrenaicus is an omnivore (Blanco-Garrido et al. 2003), a characteristic feeding habit in seasonal environments (Magalh~aes 1993). In the estuary, the number of fish species increases to 70 (Drake et al. 2002).

resources within the basin are 3357 Mm3/year and the total water demands equal 3598 Mm3/year. The water demand is high and leads to water scarcity when rainfalls are low. River regulation affects the main river and all large tributaries. There are 55 dams in the basin (one every 160 km), with a potential water storage of 7109 Mm3. The regulated water volume equals 51% of the surface water resources and 55% when groundwater resources are included (CH Guadalquivir, unpublished report). The Guadalquivir marshes are the most severely impacted area in the catchment because of agricultural and urban activities. The marshes covered 136 000 ha into the 1950s, but after much of the marshland were converted to farm and agricultural lands. The marsh system is controlled by a series of dikes and drainage canals, and the marshes are now under restoration and monitoring (Gallego Fernandez & Garcıa Novo 2002). Pollution is a major problem in many parts of tributaries and the main river. Water treatment is still limited to larger urban areas, and smaller cities and villages still add untreated sewage waters directly to adjacent watercourses. Other pollution sources are related to industry and mining. In the Jandula, some pollution is associated with hydrocarbons from oil processing. Mining activities have also caused significant impacts in the watershed. A retaining dike of a mine tailings reservoir failed in Apri1 1998 in the Guadiamar catchment that released 5 Mm3 of toxic sediments and water into the river near Donana National Park. The released sludge contained 0.6% arsenic, 1.2% lead and 0.8% zinc dry weight (Pain et al. 1998), and cumulated as a several centimetre thick layer along 40 km of the river (Grimalt et al. 1999). Mine tailing residue was found in periphyton (Sabater 2000, Martın et al. 2004), macroinvertebrates (Sola et al. 2004), fishes and waterfowl, as well as in water and sediment. An immediate cleaning of the entire area, including riparian and agricultural land and stream sediments, probably reduced the effect and allowed a quick recovery of the system (Montes 2002). The present heavy metals situation for aquatic systems of the Guadiamar is good with no observed systems being contaminated (Sola et al. 2004). Indeed, the mining accident and its follow-up triggered major programs of monitoring and recovery for the Guadiamar and Donana marshes. The Spanish administration developed the Donana 2005 Project as well as Green Corridor of the Guadiamar (Garcıa Novo et al. 2007). Both aim to restore the ecology of the affected areas and facilitate the biological connectivity between the Donana and Sierra Morena.

4.3.6. Management

The Duero (Douro in Portuguese) is in the northwest Iberian Peninsula. It is the 3rd largest river (after the Tagus and Ebro) in length (927 km, 597 in Spain and 330 in Portugal) and the largest in catchment area (97 290 km2, 80% in Spain and 20% in Portugal). The river originates in the Iberic range

Water regulation has always been viewed as the only possibility to improve the management of the Guadalquivir River because of its overall water deficit. The available water

4.4. THE DUERO

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Chapter | 4 The Iberian Rivers

PHOTO 4.3 Duero at Soria (Photo: Sergi Sabater).

at Picos de Urbion (2140 m asl) and flows west towards Portugal, reaching the Atlantic Ocean at the city of Oporto. The Spanish part of the Duero catchment drains the Cantabric Mountains in the north, the Iberian Mountains in the east, and the Carpetovetonic Mountains in the south. The river flows through the cities of Soria and Zamora. At the border of Spain and Portugal, the Duero flows through a deep valley and enters the Atlantic via a simple estuary with a sedimentary deposit along the south margin that forms Cabed^elo do Douro. Major tributaries include the Pisuerga and Esla on the right and the Eresma and Tormes on the left. The Tormes flows through the cities Avila and Salamanca. Downriver in Portugal, the Duero receives the T^amega, Sabor, Tua, Agueda and Coa. The right-side tributaries in Portugal are larger than the left-side tributaries.

4.4.1. Historic Changes and Human Impacts Paleolithic remains are evident on the Duero and Pisuerga floodplains as well as on the banks of the Coa. The first fortified settlements in the coastal Duero area are from the 10th century BC (e.g. Cit^ania de S.Juli~ao). The Celts colonized the Meseta along the river network 900 BC. Paleobotanical records show a decrease in forest cover for agriculture and livestock use already in the 10th century BC. During the Roman period, urban development, mining, agriculture and road construction caused major effects on the natural environment. By 430 AC, the Sueves had established themselves in the Douro basin in Portugal. In the Middle Ages, cavalry development was responsible for the desert fields such as Tierras de Toro y Campo near Zamora. Remains of Roman architecture are evident in the Duero catchment, with many churches from the 12th–13th century.

During the 15th–17th centuries, livestock were intensively used on the catchment. In the 20th century, rural population sharply decreased and moved into urban areas. Today, the area around the river mouth has a high human density (1462 inhabitants/km2) and a high density of small industries.

4.4.2. Biogeographic Setting The Duero catchment has Atlantic, Mediterranean and Alpine influences and lies in the Ibero-macaronesian ecoregion. About 17% of its surface area is forest and 25% is thicket. The most common tree in the catchment is Quercus ilex, the subspecies ilex in the northeast and rotundifolia elsewhere. Quercus pyrenaica is also abundant, especially in the Cantabrica range where it inhabits montane areas and other high elevation areas of the central plain. Pine forests cover the central plain of the Duero catchment where Quercus forests have decreased. The Mediterranean Juniperus thurifera grows on carbonate soils. The Euro-Atlantic oaks Quercus robur and Quercus petraea are found on the Cordillera Cantabrica, mixed with Fagus sylvatica, Castanea sativa and Pinus sylvestris. Fagus sylvatica dominates forests on acidic soils and temperate slopes at 1200–1700 m asl. Castanea sativa forests are found along Sanabria Lake and southwest of Leon. Thickets of Erica australis and Sarothamnion scoparia occur in the Iberic and Central ranges following deforestation. Riparian forests consist of Populus sp., Alnus glutinosa, Ulmus sp., Fraxinus sp. and Salix sp. The present configuration of the Duero catchment is a result of historic geological processes. The amphitheatre defined by the mountains surrounding the catchment, contains sediments from the ancient lake formed in the Tertiary.

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Quaternary glaciers covered most headwaters of the Esla, Duerma, Eria and Tera. The glacier in the Tera valley was the largest, being 5 km long. Today, several moraines are evident near Sanabria lake. The upper Pisuerga and Carrion also show effects of glaciation. Towards the Atlantic, the Hercinian massif formed the Zamora and Salamanca highlands as well as mountain ranges in north Portugal. Most of the catchment is in the northern Meseta, mostly above 800 m asl, and the highest in the Iberian Peninsula. The Duero catchment has had a progressive lowering of its surface since the Miocene, causing the loss of some former tributaries to the rivers Ebro, Sil and Tagus, and a reduction in its area.

4.4.3. Physiography, Climate, and Land Use In the headwaters, the Duero flows over Cretacic materials, later replaced by Tertiary materials as the river flows through Soria. After Zamora, sediment deposits are composed of slates, siluric quarcites and granites. The lower river flows over granitic, metamorphic and paleozoic rocks. In Portugal, the catchment is in the Hesperic Massif, mainly made up of granites and schists. The Pisuerga and Esla flow over a diverse lithology. Their headwaters originate on carbonate and devonic soils, later flowing over cretacic and liasic soils, and finally over quaternary soils with miocenic deposits. The lower Esla and the Tera flow over siluric, crystalline and granitic soils, which form the basin of the glacial Sanabria Lake. In the central Duero basin and left bank of the river, soils have a sandy texture. Here the substrate is sandstones, conglomerates and detritic limestones, in addition to fluvial deposits of conglomerate, gravel and sand. The Duero catchment has a Mediterranean climate, although in the most eastern part the climate is more continental. Near the Portuguese border, the climate becomes milder because of Atlantic influences. Winters are long and cold, especially in septentrional Meseta where average temperatures are 2 C and frost occurs for 120 days per year. In the west, winters are milder (mean January temperature is 4 C and on average 80 frost days per year). Intense cold waves (from 13 to 20 C) are associated with invasions of continental polar air from the northeast. Summer maximum temperatures (July) occasionally reach 30 C, but in the north reach only 20 C. Highest rainfall occurs in the upper Tera (>1800 mm year) and Porma (1500 mm/year). Annual precipitation decreases to 800–1000 mm in the Central and Iberian ranges, and even more so in the plains (400– 550 mm). Rainfall is irregularly distributed in the year, but mostly occurring from autumn to spring and being nearly absent in July and August. Interannual variability is even more extreme with average annual rainfalls ranging from 350 to >800 mm. Average evapotranspiration ranges between 675 and 730 mm per year. There is a strong gradient in precipitation from the Spain/Portugal border to the Ocean. The mean annual evapotranspiration and precipitation are

PART | I Rivers of Europe

<400 mm near the border, but evapotranspiration increases to >800 mm and precipitation up to 2000 mm per year on the coast. The population in the catchment is mostly in mediumsized cities (Leon, Burgos, Valladolid). There are many villages with <1000 inhabitants and few have 50 000. Most of the catchment is covered by forest and agriculture. The central region (700–800 m asl) has undergone an intensive process of agricultural exploitation over time with a predominance dry farming such as cereals (wheat, oats and barley) and vineyards. The little forest cover is composed of Q. ilex var ballota and Pinus pinea. In Portugal, vineyards are especially important (Porto wine) in the catchment. Recently, agriculture has become less important and many agricultural fields have been abandoned, whereas industrial activity of chemicals and metals as well as production of electricity has increased.

4.4.4. Geomorphology, Hydrology, and Biogeochemistry The main river channel is 572 km long. The first 72 km flows through steep valleys in the Iberic range with an overall slope of 14. The remaining 500 km of the river meanders through an open valley over soft tertiary sediments (slope 1). At the border (rkm 112), the river has a canyon shape (Canones de Arribes) with a mean slope of 3. The 402 m drop in height has been used to produce hydroelectrical power via several hydroelectric dams in both countries. From the confluence with the Agueda River to the mouth at the ocean (213 km), the river flows through narrow valleys and has a low gradient (0.6 m/km). The upper reaches have a nivopluvial flow regime with an oceanic influence. However, there is a strong relationship between rainfall and hydrology of the river. Maximal discharge occurs in spring and minimum in summer, but differences are not extreme. Major floods can occur in the Duero due to intense winter rains, although floods can also occur at late summer because of heavy storms. High discharge periods, such as in January 2006, are usually correlated with peaks in suspended solids. Discharge in the middle reach averages 101.2 m3/s (Duero at Zamora, 12 year average). Among the tributaries, the Esla and Pisuerga have the highest discharge and the Adaja has a mean discharge of 11 m3/s. Mean flow near the river mouth is 903 m3/s (Figure 4.2). The mean water temperature ranges from 11.2 C in the headwaters to 14 C at Toro and in the lower Tormes (12 year average). Minimum temperatures range from 0 to 2.8 C (in Pisuerga headwaters and Duero at Toro and Tormes). Maximum water temperature ranges from 21 (headwaters) to 28 (at Adaja river). The geology of the catchment causes a low mineralization of its waters. The Pisuerga has the highest conductivity, while the Esla and Tormes the lowest. Conductivity increases along the main channel (from 128 mS/cm at Garray to 582 mS/cm at Toro) due to water from the Pisuerga (562 mS/cm). Most headwaters in the catchment have a

Chapter | 4 The Iberian Rivers

low nutrient content (Fernandez-Alaez et al. 1986, Escudero Berian et al. 1986) and increased nutrient concentrations in rivers are related to human activities (urbanization and agriculture). Low nutrient concentrations and conductivities characterize the upper Tormes and Eresma (10–16 mg/L N–NH4, 15–23 mg/L P–PO4, 700–800 mg/L N–NO3, and 16.2–67.5 mS/cm). In the alluvial aquifer of the Pisuerga, irrigation and industry have degraded groundwater quality as well as the seasonal recharging of the aquifer (Helena et al. 2000). Waters in most tributaries and the main channel have high nitrate levels (2.5–2.6 mg/L) and relatively low phosphates (Figure 4.3). There is a trend of decreasing phosphate and ammonium levels, but not nitrate, in the last 12 years. Reservoir outflows have caused significant increases in nutrient concentrations and in benthic algal biomass (Camargo et al. 2005). Contamination episodes in the Duero have been related to timber industries in the catchment. Most of the chemicals used to improve wood properties produce toxic effects on aquatic fauna. However, dissolved oxygen values <6 mg/L have not been recorded recently, and nearly 75% of the rivers are classified in good condition using biotic indices. The trophic analysis of lakes and reservoirs on the Duero (CH Duero 2004) indicate that Sanabria Lake and several reservoirs are oligotrophic. Lake Sanabria has low chlorophyll values (1.9 mg/L) with a phytoplankton dominance of cryptophytes and small chlorophytes (Negro et al. 2000). Most oligotrophic or oligo-mesotrophic reservoirs are in the north Duero catchment, especially in the upper Pisuerga, Carrion, Esla and Orbigo. These reservoirs also have low chlorophyll (<4 mg/L), phosphorus and nitrogen contents. The most eutrophic and hypertrophic reservoirs are in the south Duero catchment, and are typically small and affected by urban inputs. Reservoirs on the main channel are also eutrophic, and 70% of the reservoirs can be classified as mesotrophic. In several reservoirs (13 of the 40 monitored by the CHD), a significant growth of cyanobacteria was evident. In Portugal, diffuse pollution is moderate and the pollution load is limited to some agricultural industries.

4.4.5. Aquatic And Riparian Biodiversity Riparian vegetation in the catchment has diverse distributions. In areas where phreatic levels are high but rarely inundated, willows (Salix spp., Salix alba), oaks (Quercus pyrenaica), elms (Ulmus minor), and spiny plants (Rubus ulmifolius, Crataegus monogyna, Lonicera spp., Prunus spona and Rosa spp.) dominate. In upper mountain areas, riparian vegetation is dominated by Betula pendula, Prunus lusitanica, Reseda gredensis and Biscutella gredensis. In torrential siliceous streams that dry in summer, buckhorns (Flueggea tinctoria) may be present. Boxwood (Buxus sempervivens) is dominant on the stony substrate in the Sabor River, the largest unregulated tributary of the Duero in Portugal. In many human impacted areas, the riparian forest is

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dominated by rapidly growing trees such as poplar, and in the middle reach of the Duero, riparian vegetation is scarce due to the agricultural use of river margins (Photo 4.1). Benthic chlorophyll values are low in the upper Tormes and Eresma (5–11 mg/m2), but increase significantly below deep release reservoirs (52–126 mg/m2) (Camargo et al. 2005). Scrapers and collector-gatherers also increase below the dams (Camargo et al. 2005). Macrophytes are quite diverse in the Duero catchment. Macrophytes in the Tormes are characterized by Juncus acutiflorus and Carex hirta at open sites, and Oenanthe crocata, Myosotis scorpioides and Epilobium obscurum at shaded sites (Escudero Berian et al. 1986). The most abundant submerged species are Ranunculus trichophyllus, O. crocata, Apium nodiflorum, and M. scorpioides; depending on current velocity (Escudero Berian et al. 1986). In the headwaters of the Bernesga, macrophytes are dominated by Carex acuta var. broteriana, Agrostis stolonifera and Mentha longifolia, also depending on current velocity (Fernandez-Alaez et al. 1986). Macroinvertebrate richness and biodiversity in the Duero in 1980 showed good quality in most low-order reaches. The index of biological quality decreased after the city of Soria and even more so after the Pisuerga confluence by Valladolid. Biological quality in the middle Duero slightly recovered after Zamora and the inflow from Esla and Tormes (Gonzalez del Tanago & Garcıa de Jalon 1984). In the right-side tributaries in Portugal, the mayflies Habroflebia, Caenis and Baetis, the stoneflies Leuctra spp., chironomids and oligochaeta occur frequently or in large numbers (Gra¸ca et al. 2004). There is a large diversity of caddisflies, including Limnephilidae (e.g. Allogamus ligonifer, Limnephilus guadarramicus, Potamophylax rotundipennis, Chaetopteryx lusitanica), Leptoceridae (e.g. Setodes argentipunctellus, Athripsodes braueri/tavaresi), Hydropsychidae (Hydropsyche siltalai), Philopotamidae, Calamoceratidae, and Sericostomatidae. Stoneflies account for 7 families and 17 species (e.g. Leuctridae, Nemouridae, Capniidae, Perlidae) in two examined streams (Cortes et al. 1998). Two endemic macroinvertebrates are found in the Duero catchment. One is the native crayfish (A. pallipes), and the other is the river mother-of-pearl (Margaritifera margaritifera). This endangered bivalve has been found in some areas in the Tera and Negro (Esla tributary) having low mineralization and cold oligotrophic waters (Morales et al. 2004). Three introduced invertebrate species are important in terms of biomass: the clam Corbicula fluminea, the Louisiana red crayfish P. clarkii and the introduced signal crayfish Pacifastacus leniusculus. The most common fish species in the Duero are Chondrostoma arcasii (living in mountain lakes and rivers associated with Salmo trutta), C. lemmingii (found in rivers in the southeast), Squalius carolitertii, Barbus bocagei (in the entire basin but currently decreasing in abundance), Chondrostoma duriense (endemic Duero fish found in high current rivers and reservoirs), and Cobitis calderoni. In the lower river, the endemic ruivaco Rutilus macrolepidotus, and the

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endangered, vulnerable or rare P. marinus, Alosa alosa, A. falax, S. trutta, B. bocagei and Chondrostoma polylepis are present (Moreira et al. 2002). These Iberian fishes are threatened by the introduction of exotic species such as sunfish, American perch, carp, red fish and gambusia. Reservoirs also impede fish migrations and create unsuitable habitat conditions for riverine fish. Other abundant fishes are trout, pike, tench and Gobio gobio. Trout (S. trutta fario L.) show two genetically divergent groups in the catchment (north and south) that suggest successive colonizations after the Pleistocene glaciations (Bouza et al. 2001). Sixteen species of amphibians and reptiles have been recorded in the catchment. Particularly important is the Lusitanic salamander Chioglossa lusitanica in areas with precipitation >1000 mm. Other endemic species are Triturus boscaii, Discoglossus galganoi, Alytes cisternasii and Rana iberica. The cliffs of Duero International Park along the border with Spain (Arribes del Duero) are an important nesting area for the griffon vulture, Egyptian vulture, peregrine falcon, golden eagle, black kite and hen harrier. The white stork, black stork and Chough also are frequent in this area. In fast flowing waters of mountain streams, water birds are uncommon except for the dipper. An interesting mammal of the Duero in Portugal is the water mole; an Iberian endemic found only in unpolluted flowing waters.

4.4.6. Management and Conservation The largest reservoir in the catchment is La Almeda on the Tormes with a storage capacity of 2586 Mm3. The most important water use in the catchment is irrigation that requires >3603 Mm3/year, whereas urban supply uses 214 Mm3/year and industry 43 Mm3/year. Nearly 10% of the water demands are met by groundwater. The hydrological plan of the Duero basin (1998) assigned 645 Mm3/year downstream to the main reservoirs for environmental objectives. Many shallow lakes are found along the main channel, especially in the central region. These lakes are classified as ‘natural spaces for special protection’, and include Isoba and Ausente lakes (in Leon), Laguna Negra (a glaciar lake in Soria), Lagunas de Villafafila (in Zamora), and Fuentes Carrionas (in Palencia). The last two are also wildlife reserves. The Natural Park of Lago de Sanabria and its surroundings include the largest glacial lake of the Iberian Peninsula (369 ha) and many dispersed lagoons hosting patches of Sphagnum, as well as glacial canyons and valleys. This Natural Park is included in the Natura 2000 network. The Natural Park of Arribes del Duero includes the canyon of the river Tormes and its surroundings. This area has been declared a special protection zone for birds (ZEPA) since 1990. Montesinho Natural Park is at the source of one of the most important and best preserved tributaries of the Duero, the Sabor. Lastly, Alv~ao Park is an area aimed to protect several endangered mammals and its rivers are probably some of the best studied in terms of aquatic invertebrates and fish. The

PART | I Rivers of Europe

Duero river basin authority in Spain is the Hydrogrologic Basin Authority of the Duero (CHD). It was created in 1927 to administer the use of water for irrigation and hydroelectric power, and currently manages water planning, water quality, flood prevention, environmental issues and water rights. Spain and Portugal have an agreement (Convenio de Albufeira signed in 1998) created to manage all river basins shared between the two countries.

4.5. THE EBRO The Ebro catchment is in northeast Iberian Peninsula and covers 85,362 km2. Most of the catchment is in Spain with some of it in Andorra and France (445 and 502 km2, respectively). The Ebro is the largest Iberian river flowing into the Mediterranean Sea and is the largest catchment in Spain, encompassing 17.3% of its surface area. The catchment is delimited by the Cantabric Mountains and Pyrenees in the north, the Iberian range in the southeast, and the Coastal Catalan Mountains in the east. Historically, the river originated at Fontibre (from the latin Fontes Iberis, Springs of Iberia) at 880 m asl near Reinosa in Cantabria. Today, the river source is at 1980 m asl in Penalara (27 km upstream from Reinosa). The main river is 910 km long and flows northwest to southeast from the Cantabrian Mountains to its delta at the Mediterranean Sea. Major tributaries include the Aragon, Gallego, and Cinca-Segre from the Pyrenees and Cantabrian Mountains and the Oja, Iregua, Jalon, Huerva, and Guadalope from the Iberian range. The total drainage network equals 12 000 km. The main channel flows near the Iberian range. The Ebro catchment includes one of the largest depressions on the Iberian Peninsula besides the central Meseta. The delta covers 330 km2, 20% of it being a natural protected area and the rest being urban and agricultural land. Rice is the most significant crop. The catchment contains several small lakes, mainly in the Pyrenees, including the karstic lake of Montcortes. Several endorheic lakes are also scattered (Sarinena, the brackish lakes of Chiprana and Gallocanta) in the middle and lower basin. Both freshwater and brackish lakes are significant in the delta region. The Ebro is subject to regulation by many reservoirs. The most important reservoirs are in the lower catchment (Flix, Mequinenza and Ribaroja) that reduce sediment transport to the delta (Photo 4.4).

4.5.1. Historical Perspective The Ebro flows through the regions of Cantabria, Castilla, Leon, Rioja, Navarra, Aragon and Catalonia. The most significant cities, historically, along the Ebro are Miranda de Ebro, Haro, Logrono, Tudela, Alagon, Zaragoza, Caspe and Tortosa. The catchment was inhabited since the Paleolithic. Prehistoric records are evident in the Pyrenees and prePyrenees with remnants of dolmens and megalithic graves,

Chapter | 4 The Iberian Rivers

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PHOTO 4.4 Upper part of the river Ebro River in Haro (Photo: Sergi Sabater).

as well as in the Iberian range in the Guadalope basin. Ibers and celts inhabited the catchment from 15th to 3rd century BC. About 200 BC, the romans colonized from the south, settling in cities such as Zaragoza, Huesca and Teruel. The Arabs arrived on the Peninsula in 711 AC, settling in the cities Zaragoza and Tortosa that were connected by the Ebro. Irrigation ditches were dug and iron and copper industries were developed at this time. The Arabs also settled at Tudela, Calatayud, Huesca and Barbastro. The Aragon Kingdom, which occupied most of the catchment, began 1000 AC. During its history, the Ebro played an important role as a frontier line and also as a communication link. The Ebro catchment was the scene of many bloody battles, such as those in the lower basin in the Spanish Civil War (1936– 1939). River hydrology played a military role during this battle, with sudden floods from upstream reservoirs to interrupt infantry crossings. Agricultural development and navigation needs resulted in infrastructure construction after 1400 AC. The Canal Imperial was completed in 1446 and Pignatelli dam was finished in 1789 by the Conde de Arana, Minister of Charles III of Spain. The Canal Imperial was constructed to connect the Cantabric and Mediterranean Seas. While this project was never finished, the channel flows 108 km along the main river from El Bocal (Navarra) to Fuentes de Ebro (Zaragoza).

4.5.2. Biogeographic Setting A broad spectrum of landscapes make up the Ebro catchment, including boreal-alpine coniferous forests, mixed decideuous forests, Mediterranean evergreen and mixed for-

est and shrubs, and semi-arid treeless formations. Paleartic and cosmopolitan species are characteristic along the river valley in the riparian zone. Some species typically found in the headwaters, such as Cornus sanguinea and Brachypodium sylvaticum, are also found along the river corridor. In the floodplain are species of Mediterranean and iranoturanian, iberonorth African, and endemic species typical of arid gypsum substrate. Water availability allows for the close proximity of typical upland species within the depression with those in the riparian zone. Although vegetation in the Ebro catchment is less altered than in other Iberian catchments, forests represent only 3.1% of the potential forested area (Molina Holgado 2002). The Ebro catchment had a long period as a closed intramountain drainage basin resulting from tectonic topography in the Pyrenees, Iberian range, and Catalan Coastal range. In the late Oligocene, a dry climate probably lowered the lake level and prolonged this endorheic basin stage. The Ebro gradually opened to the Mediterranean in the Miocene between 13 and 8.5 Ma. Groundwater flow was important for the formation and evolution of evaporitic lacustrine facies in the Iberian range and Ebro catchment. The hydrogeology of the basin today is similar to that during the Miocene, allowing groundwater and dissolved salts to cumulate in large areas of diffuse discharge and creating lakes where the evaporites would precipitate. Weathering of underlying evaporitic formations caused the catchment to subside during the Tertiary and Quaternary (Benito et al. 1998). Lake sediment analysis (geochemistry and pollen analysis) from the central basin indicates that some areas experienced a more positive water balance than today. These data suggest that the Ice-Age climate in the

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western Mediterranean region was characterized by cold winters with relatively high humidity.

4.5.3. Physiography, Climate, and Land Use The Ebro catchment has a triangular shape with the larger sides being the Iberian range and the Pyrenees. These two ranges converge in the northeast. The internal Ebro depression increases in width from west to east. The topography causes a Mediterranean climate with continental characteristics in most of the catchment, which becomes semi-arid in the center of the depression. The western side (Pyrenees and Iberian mountains) has an oceanic climate. Mean annual precipitation in the catchment is 622 mm (mean from 1920 to 2000) with high monthly and annual variability. Long periods of low precipitation are typical in late autumn and winter, and higher rainfall occurs in spring and autumn. The rainfall is irregularly distributed in the catchment, ranging from 900 mm in the Atlantic headwaters to 500 mm in the southern Mediterranean zone. Extreme values of 3000 mm/ year in the Pyrenees and <100 mm/year in the central plain have been recorded. Long-term records (1916–2000) show no clear trend in rainfall decrease in the catchment, except for a slight decrease south of Zaragoza (CH Ebro 2005). Stromatolithic microbial mats at the delta revealed long-term effects of El Nino Southern Oscillation events (SanchezCabeza et al. 1999), as did sediment records in an endorheic saline lake (Rodo et al. 2002). Air temperatures range from mild in the more oceanic western area to high temperatures in summer and intense cold and fog in winter in the central depression. A northwest-southeast cold and dry wind (cierzo) is characteristic in the central depression, and can lead to soil erosion and salt transport (Sterk et al. 1999). A mild warm wind sometimes occurs, especially in summer, in the opposite direction (southeast–northwest). Nearly half of the population resides in the cities Zaragoza, Vitoria, Logrono, Pamplona, Huesca and Lleida in the center of the catchment. The Pyrenees and Iberian range have low population densities (most areas with <2000 inhabitants). Altogether, 40% of the catchment has a population density <5 inhabitants/km2. Land use has been traditionally agriculture (vineyards, orchards and corn), although a progressive abandonment of rural activities has lead to the regeneration of woodland and forest cover (Gallart & Llorens 2002). Today, industry is an important activity in the basin with hydroelectric production using 8297 m3/s from 340 hydroelectric plants within the catchment.

4.5.4. Geomorphology, Hydrology, and Biogeochemistry In the first 240 km, the river meanders and flows through rocky canyons at high current velocity. Downstream to rkm 510, the river flows through the plain and has many meanders. In the middle reach, tributaries from the Pyrenees are

PART | I Rivers of Europe

larger than those from the right margin. The main tributary from the right is the river Jalon; and those from the left are the Aragon, Gallego, and Cinca-Segre. Tributaries from the Cantabric Mountains and the western Pyrenees have a pluvial oceanic flow regime. Snow retention in the central and eastern Pyrenees causes a nivopluvial flow regime in those streams. The Segre is the longest tributary of the Ebro, and drains the Pyrenees. The Cinca merges with the Segre just before its confluence with the Ebro. Near the reservoir of Mequinenza, the Valcuerna, Guadalope and Matarranya enter the Ebro. The hydrological regime is more continental in the east, while the southeast has a stronger Mediterranean and continental character with no snow. The Mediterranean pluvial regime dominates streams in the Guadalope and Matarranya catchments. The lower Ebro flows through 120 km of canyon meanders and is quite deep. The river widens at Mora d’Ebre and crosses the Catalan Range before reaching the sea as the Ebro Delta. The Ebro itself shows the lowest interanual variation in flow than other Iberian rivers. Groundwater inputs further smooth its flow regime. A groundwater influence is especially notable in the Jalon up to the Matarranya on the right side and the Ega, Arga, Irati and Alcanadre from the left. High discharge occurs on average from October to March because of the oceanic climate, and into May downstream because of snowmelt from the Pyrenees. Low discharge occurs from July to October. Historical flow records at the mouth (mean annual runoff 13 408 Mm3) show a decrease of nearly 40% in mean annual flow in the last 50 years, resulting from a decrease in precipitation and increase in water consumption for irrigation. An increase in forest cover in the headwaters and the associated increase in evapotranspiration may also be related to the lower discharge (Gallart & Llorens 2004). Regulation of the Ebro in the 1960s caused a major change in the discharge pattern by altering flow timing and, particularly, flood peaks (Lopez-Moreno et al. 2002) (Figure 4.2). Batalla et al. (2004) analyzed flow records from 22 rivers before and after dam construction to determine the effects of reservoirs on flow regime. Variability in mean daily flow was reduced in most cases due to water storage in winter and increased flow in summer (related to irrigation). Water temperature ranges from on average 13 C in the headwaters to 17 C in the lower reach, and with a clear seasonal pattern. A slight decrease in temperature occurs in summer in the lower reach due to thermal inertia of water in the reservoirs (Val et al. 2003). An inverse effect is found in autumn and winter. The Ebro has high conductivity because of its geology. An abundance of gypsum is responsible for the high salinity of waters in the Zaragoza area. Conductivity increases from the headwaters (200 mS/cm) downstream to Zaragoza (2500 mS/cm). The Gallego also contributes waters with high conductivity (1600 mS/cm) probably due to gypsum in its lower watershed. In contrast, conductivity is much lower in the Aragon and Segre (450 and 550 mS/cm, respectively). Conductivity decreases below the

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Chapter | 4 The Iberian Rivers

reservoirs (<900 mS/cm), being related to the input of Segre waters and internal processes. The Ebro at Tortosa transports 13 mg/L of suspended solids with peaks reaching 40– 100 mg/L. High levels of suspended solids (3500 mg/L in the Aragon, 14 000 in the Gallego) can occur at times. Transport of suspended solids in the headwaters is mainly related to discharge, while in the middle Ebro upstream of the reservoirs it is regulated by sediment availability (Roura 2004). Dams in the lower Ebro retain >95% of the suspended fine sediment in the river and alter its quality (Vericat & Batalla 2005). In 1998–1999, the organic fraction before dam operation was 9% of the total suspended matter and had a C:N ratio of 13:52, but was 56% of the total suspended matter with a C:N ratio of 6:11 after the dams because of high plankton abundance (Roura 2004). Average phosphate concentrations ranged from 0.08 to 0.27 mg/L P–PO4 in 1980–2004, and decreased to 0.02– 0.06 mg/L (in Tortosa) in 2004–2005 because of the construction of water treatment plants. No significant changes have been observed for nitrate (Figure 4.3). Nutrient loads are high during high flows, but dilution causes NO3 and DOC concentrations to be relatively low and oxygen content relatively high. During low flows, the river receives considerable nutrient loads from point and non-point sources. The lower dilution capacity causes higher concentrations of nitrate and DOC as well as phosphate. Nutrient pollution is a concern in the middle and lower reaches of the river, both related to industrial activities and non-point sources. Nonpoint sources contribute annual nitrate loads of 25 Tm NO3/ day (Torrecilla et al. 2005). Non-point agricultural sources account for 64% of the nitrate loads in this area of the river, while urban and industrial point sources are responsible for 88% of the phosphate and 71% of the DOC loads (Torrecilla et al. 2005). Other sources of pollution are mines in the north, mercury pollution from the chloro-alkali industry, production and use of solvents and chlorinated pesticides, and flame retardants in auto and electrical plants in the middle-lower reaches. Organic compounds on sediments such as polycyclic aromatic hydrocarbons, alkylphenols and polybrominated diphenyl ethers have been detected along the entire river, and DDT and chlorobenzene have been detected at several sites (Lacorte et al. 2006). Bioaccumulation of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD) in fish and sediments was detected below the heavily industrialized city of Monzon (Eljarrat et al. 2005). In the lower Ebro, high concentrations (20–225 ng/ L) of atrazine and other pesticides have been recorded, while endocrine–disruptors have been detected at some hot spots in the middle and lower reaches (Lavado et al. 2004). The marine salt wedge in the Ebro delta reaches 25 km upstream, especially in summer, and disappears during high flows in spring. Today, flow regulation favours the persistence of the saline wedge (Ibanez et al. 1999), leading to a decrease in oxygen content and even anoxia (Munoz & Prat 1994). The lower sediment input affects the physical struc-

ture of delta sediments, and is associated with the current regression of the delta.

4.5.5. Aquatic and Riparian Biodiversity Planktonic (riverine) chlorophyll levels range between 10 and 17 mg/L from the headwaters to Zaragoza, and then increase up to 60 mg/L in the meander plain. Below the large reservoirs, river plankton chlorophyll decreases to <10 mg/L (Sabater et al. 2008). The presence of zebra mussels, the abundance of macrophytes and a certain decrease of phosphorus may be the reason for that decrease in chlorophyll relative to historical values. Chlorophyll concentrations in the lower Ebro in the 1990s ranged from 5 to 46 mg/L, with maximum values in spring and summer (20– 45 mg/L) and lowest values in winter (5–12 mg/L) (Sabater & Munoz 1990). Phytoplankton communities in the lower Ebro (last 60 km) were dominated by diatoms and greenalgae (especially in summer), while Cyanobacteria were frequent in autumn (Sabater & Munoz 1990). Asterionella formosa was most common in winter, while centric diatoms such as A. granulata, Cyclotella sp., Skeletonema potamos and Stephanodiscus sp. were dominant in autumn, spring and early summer, and Scenedesmus sp., Coelastrum sp. and Pediastrum sp. were most abundant in summer. Benthic chlorophyll in the main channel is on average 266 mg/m2 in summer and 196 mg/m2 in autumn (Sabater et al. 2008). In summer, floating algae and macrophytes are present in the lower river, at times covering >40% of the water surface. Epilithic diatoms in the upper Segre are dominated by Achnanthidium subatomus, Diatoma mesodon, Cymbella silesiaca, Fragilaria arcus, F. capucina, Gomphonema pumilum, Meridion circulare and Nitzschia pura (Goma et al. 2005). In temporary saline lakes, the phototrophic community is composed of planktonic (Dunaliella sp., Aphanothece sp.) and benthic organisms (Hantzschia amphyoxis) (Comin 1999). The permanent Lake Salada de Chiprana (78 g/L salinity on average) is covered by microbial mats of Microcoleus chthonoplastes (300 mg Chl a/m2) and the charophyte Lamprothamnium papulosum (de Wit et al. 2005). Microbial mats at the Ebro delta are composed of three pigmented layers of phototrophic organisms: an upper brown layer of Lyngbya aestuarii and diatoms, an intermediate green layer of the cyanobacterium Microcoleus chthonoplastes, and an underlying pink layer of purple sulphur bacteria (Sole et al. 2003). A new amoeba species, Vannella ebro, has been isolated from microbial mats from the Ebro delta (Smirnov 2001). Macrophytes are common in the lower river below the reservoirs. The most abundant macrophytes are Potamogeton pectinatus, P. crispus, P. densus, Ceratophyllum demersum, Myriophyllum spicatum and Lemna gibba (Molina Holgado 2002). At the delta, Potamogeton pectinatus is mainly found in freshwater areas, while Ruppia cirrhosa inhabits transitional zones between freshwater and seawater.

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Mixed stands of Zostera noltii, R. cirrhosa and the floating macroalga Chaetomorpha linum develop in saline areas (Menendez et al. 2002). Healthy riparian forests are still found along the Aragon, Arga, Irati, Cinca, Segre and Gallego, as well as in some sections of the Ebro. Riparian species having rapid growth and being well adapted to water level fluctuations are widespread (S. alba, P. alba, P. nigra, Tamarix africana, Tamarix gallica). Forests of Alnus glutinosa only occur in small areas in the northern catchment. Floodplains are colonized by Polygonum lapathifolium, P. persicaria, Xanthium echinatum and Paspalum paspalodes. In Mediterranean tributaries, the macroinvertebrate genera Ecdyonurus, Physella acuta, and Baetis, and Hydropsychidae are abundant. The Mediterranean influence on these systems is reflected by macroinvertebrate taxa (Perla marginata, Hydroptila insubrica and Hydropsyche instabilis) adapted to avoid the impact of floods (Argerich et al. 2004). Macroinvertebrate communities in the lower river comprise an abundance of filter feeders (Hydropsyche, Ephoron virgo). Where light reaches the river bottom, stones and boulders are covered by grazers such as the gastropods Melanopsis sp. and Theodoxus fluviatilis (Munoz & Prat 1994). Euryhaline species such as the polychaete Ficopotamus and the trichopteran Ecnomus are abundant near the delta (Munoz & Prat 1994). The giant European freshwater pearl mussel (Margaritifera auricularia) present in the lower part of the river has declined dramatically in abundance since the early 20th century (Araujo & Ramos 2000). The introduced zebra mussel, Dreissena polymorpha, was first detected in Ribaroja reservoir in summer 2001, while the helminth Phyllodistomum folium that infects zebra mussels and the Asian bivalve C. fluminea have been recently recorded in the lower Ebro. The fish community of the Ebro is composed of species introduced before 1900 and those introduced after 1900. Most of these fish are vulnerable (such as A. anguilla, P. marinus, C. calderoni and C. paludica), while others are threatened (Aphanius iberus, Valencia hispanica, Gasterosteus gymnurus, Salaria fluviatilis, A. sturio) (CH Ebro 2005). The Ebro catchment encompasses a biogeographic zone where southern and northern fishes occur, making assemblages vulnerable to be introduced and invasive species such as Micropterus salmoides, Sander lucioperca, Gambusia holbrooki, Esox lucius, Ameiurus melas and the large Silurus glanis (CH Ebro 2005). The introduced Asian cyprinid Pseudorasbora parva has recently been recorded in the delta (Caiola & Sostoa 2002). Dam construction also causes an increase in fish density, especially the smaller species.

4.5.6. Management and Conservation The economic use of water for irrigation and reservoir construction is the main environmental disturbance in the Ebro catchment, and has altered the flow regime except in upper tributaries. The Ebro has 187 reservoirs

PART | I Rivers of Europe

impounding 57% of the mean annual runoff. All dams were constructed during the 20th century with 67% of the reservoir capacity built between 1950 and 1975. Three reservoirs have >500 Mm3 in capacity (Ebro, Mequinenza and Canyelles). The Hydrologic Basin Authority (est. 1926) of the Ebro (CH Ebro 2005) was the first organization for managing Spanish rivers. The first objective was to organize irrigation for agriculture. Today, it is responsible for the control of catchment master plans based on the Water Framework Directive. A recent bioassessment indicates ‘good’ and ‘very good’ status of 70– 77% of the examined rivers (CH Ebro 2005). The Spanish National Hydrologic Plan (2001) proposed a water transfer from the lower river (maximum of 1050 Mm3/ year) to the Segura and Jucar in the southeast. The plan also included the construction of 100 new dams and infrastructure for new irrigation areas, as well as for water treatment plants and river channelization. Fortunately the plan was rejected because of environmental concerns (Biswas & Tortajada 2003; Getches 2003). The Ebro headwaters host two National Parks, the National Park of Ordesa and Monte Perdido, and the National Park of Aig€uestortes and Sant Maurici. At the delta, the Natural Park of the Delta de l’Ebre is an important wetland, especially for migrating birds. Apart from these areas, many ZEPAs and LICs (included in Net Natura 2000) occur in the Ebro catchment, mostly in the headwaters (CH Ebro 2005).

4.6. THE TAGUS The Tagus (Tajo in Spanish, Tejo in Portuguese) is one of the largest Iberian rivers, covering a drainage area of 80 600 km2 in Spain (70%) and Portugal (30%). The river runs for 1007 km from east-central Spain in the Sierra de Albarracın (1590 m asl) to the Atlantic Ocean at the estuary at Lisbon, the largest of Europe. It is the longest river on the Iberian Peninsula and third in respect to surface area and discharge. Its name (Tajo = Cut, in Greek) reflects the abrupt fracture that the river forms on the landscape. The main tributaries are the Jarama, Alberche, Tietar, Alagon, Guadelia, Almonte and Salor in Spain, and the Erges, Ponsul, Z^ezere and Sorraia in Portugal (Photo 4.5). The Tagus defines the political border between Spain and Portugal just downstream of Alcantara reservoir. The river flows through Lisbon in Portugal and Toledo and Aranjuez in Spain. The Tagus is navigable for 160 km upstream from its mouth, although several large dams retain water for irrigation and hydroelectric power. The catchment supports the water needs of the largest population (11 million people) in the Iberian Peninsula, including those of two European capitals (Madrid and Lisbon). Some of the Tagus is diverted to the Segura basin, supplying water for another 1.5 million people in southern Spain and supporting the existence of the Tablas de Daimiel ecosystem in the La Mancha Natural Reserve.

Chapter | 4 The Iberian Rivers

PHOTO 4.5 Tagus River at Toledo in 1958 (A) and today (B).

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4.6.1. Historical Perspective Human history in the Tagus originates in the Bronze Age (10th century BC), when inhabitants in the central basin (Spanish and Portuguese Extremadura) engraved stones and erected monoliths along the river, particularly around the city of Caceres. The founding of Lisbon may be related to a Phoenician settlement since recovered objects date from 1200 BC. The Tagus was the central axis of the Roman province of Lusitania in the second-century BC, with the colony of Iulia Augusta Emerita (the present city of Merida) as the capital. During the Arabic domain (11th century), Lisbon was one of the most important cities of Al Andalus with >20 000 Christian, Jewish and Islamic inhabitants.

4.6.2. Biogeographical Setting The creation of the Tagus catchment can be traced back to the late Permian, when an extensive tectonic regime prevailed across the eastern half of the Iberian plate. The Tagus is biogeographically within the Mediterranean region. Mild conditions are expressed by average air temperatures that range from 13 to 17 C with a minimum in the coldest months from 1 to 5 C. The potential vegetation is made up of Q. rotundifolia and Q. ilex, which changes to thickets of Quercus coccifera and Quercus faginea under human pressure.

4.6.3. Physiography, Climate and Land Use The Tagus catchment is delimited by the Iberian Central Range in the north, the Toledo Mountains and Sierra of Montanchez in the south, and the Iberian Mountains (Serranıa de Cuenca and Sierra de Albarracın) in the east. The highest mountains are in the Central Range (2000 m asl), while the Iberian Mountains are <1800 m asl and the Toledo Mountains are <1600 m asl. The river has a relatively steep gradient profile, flowing through deep gorges with waterfalls. Along the Portuguese–Spanish border, the valley side-slopes are steep, but then the river enters into a low hill area and finally onto a flat plain. The Tagus catchment is bordered to the north and west by Precambrian and Palaeozoic mountains of igneous rocks, slates and quartzites, and to the south and east by relatively low lying hills of Mesozoic carbonates. The river runs mainly over schist-greywacke rocks from the pre-Ordovician along the border, although granites are scattered through the areas of Salvaterra do Extremo and Segura. The remaining areas are covered by Tertiary detritic deposits. The Tagus first flows northwest, but later flows west. The tributaries are distributed asymmetrically within the catchment, and the most important (Gallo, Jarama, Guadarrama, Alberche, Tietar and Alagon) enter from the right side. Left tributaries are generally shorter and with less discharge. In Portugal, tributaries originate from the mountains of Serra da Estrela,

PART | I Rivers of Europe

A¸cor and Lous~a. The main tributaries here are the Erges, Ponsul, Ocreza and Z^ezere from the right side, and the Sever and Sorraia from the left side. The Z^ezere and Sorraia together cover 50% of the surface area of the Tagus in Portugal. Mean annual precipitation in the Tagus catchment is 670 mm, and ranges from 500 to 1000 mm. Highest rain fall occurs in the Tietar, Alagon and Arrago basins, where microclimatic conditions allow rich cultures of tobacco, pepper, and apple and cherry trees. Lowest precipitation occurs along the left side of the middle Tagus. In the upper Tagus, winter temperatures are cold and summer temperatures do not exceed 20 C. In the middle and lower catchment, annual mean temperature ranges between 4 and 10 C in the mountains and 14–17 C in the valleys. Precipitation also differs, being 1300 mm and 500 mm, respectively. Nearly 80% of the precipitation falls during the three winter months. The average evapotranspiration ranges from 400 to 720 mm. Steep slopes, as well as hot dry summers, restrict agriculture to near the Portuguese–Spanish border, although other areas are intensively cultured by humans. In the case of the Jarama basin (Vizcaıno et al. 2003), the area occupied by agriculture increased by 5% and industrial use by 26% from 1950 to 1990, whereas riparian forest areas decreased by 31%. In the Sorraia, a system of irrigation channels was built between 1935 and 1965, allowing the transformation of the fertile alluvium to rice plantations.

4.6.4. Geomorphology, Hydrology and Biochemistry The present morphology of the Tagus is a consequence of dam construction throughout the basin. The dams and their regulation have decreased the frequency of high flows and associated sedimentation rates (Martin-Vide et al. 2003). Construction of levees along the river has caused changes in the river channel, especially with respect to riparian vegetation and the formation of sedimentation bars. The floodplain of the Jarama decreased in area from 1750 ha in 1956 to 580 ha in 1999 (Vizcaıno et al. 2003). While meanders and palaeochannels were evident in the floodplain up to the 1950s, there was an obvious reduction by the 1990s because of restrained lateral expansion by the river, as well as a decrease in river width by 50%. The Tagus flow regime shows high seasonality and interannual variability. Discharge is maximal from February to March and minimal in August. The outflow into the Tagus estuary is 315 m3/s, and monthly averages range from 30 to 2050 m3/s. Floods occur mainly in December and January, and can have peak discharges up to 45 times the average. Historical records show a similar pattern in flood distribution (Benito et al. 1998). From 1942 to 1949 and 1971 until today, only two floods exceeded 1500 m3/s, while four surpassed 1000 m3/s. The highest recorded flood was in March 1947, and was estimated between 2500 and 3700 m3/s (Benito et al.

Chapter | 4 The Iberian Rivers

1998; Martin-Vide et al. 2003). Analysis of slackwater deposits suggests that floods of similar magnitude have occurred at least nine times in the past millennia (Benito et al. 1998). The Tagus drains a basin mainly composed of siliceous rocks, as reflected in moderate conductivity values of 650 mS/cm in the upper river and 300 mS/cm downstream of Alcantara reservoir. Major tributaries also have low conductivities (Alberche, 130 mS/cm; Tietar, 135 mS/cm), except for the Jarama at 1300 mS/cm because of heavy industrialization in the catchment. Water conductivity in the Tagus below its confluence with the Jarama is 1800 mS/cm. Mean annual temperature in the main river is 14 C in the upper reach and 18 C downstream of Alcantara reservoir. The Jarama is the most polluted of the main tributaries. This river has high average nutrient concentrations (10.8 mg NO3/L, 12.5 mg NH4/L, 2.18 mg P/L; averaged over the last 10 years). The Alberche (3.86 mg NO3/L, 0.13 mg NH4/L, 0.23 mg P/L) and Tietar (4.04 mg NO3/L, 0.35 mg NH4/L, 0.44 mg P/L) contribute lower levels of nutrients. Around 80% of the basin aquifers show nitrate contamination problems, with the Ocana, Tietar and Alcarria having values >100 mg/L (ITGE 1998). In irrigation channels in the lower Tagus, aquatic macrophytes and algal mats (up to 1 kg fresh mass/m2) are abundant and can cause serious environmental problems (Ferreira et al. 1999). Nutrients have increased significantly in the last 11 years in the middle Tagus. Ammonia is 100 higher in the Toledo (6.41 mg NH4/L) than in the Trillo (0.08 mg NH4/L) and nitrates increase from 3.3 mg NO3/L in the Trillo to 15 mg NO3/L in the Toledo. Mining activities are important in the catchment. Lithic industries are common in the main valley and northern tributaries. Major deposits of sepiolite are found in the Tajo basin and actively mined. Total chromium concentrations in the Jarama (mainly in its hexavalent form) reach 0.05–0.10 mg/L. Levels of this metal in sediments (9–5128 mg/kg DW) and interstitial waters (0.03– 0.75 mg/L) are high as well (Arauzo et al. 2003). The river between the Jarama and Tagus rivers to the Toledo is the most polluted, also from chemicals such as anionic surfactants and arsenic. At the Tagus estuary, there is a large input of industrial pollutants. Arsenic emissions from industrial complexes have been estimated at 1000– 2000 tons/year (Andreae et al. 1983).

4.6.5. Aquatic and Riparian Biodiversity The irrigation channels in the lower Tagus and Sorraia create conditions for algal proliferation. Filamentous algae are common, dominated by Cladophora glomerata and diatoms such as Fragilaria construens, Achnanthes subhudsoni and Navicula goeppertiana. Macrophytes in slow-water areas include Digitaria sanguinalis, Echinochloa crus-galli and Cyperus diformis. Degraded, nutrient rich areas are typically invaded by giant reed, reeds and cattails. Riparian areas

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along the Tagus are frequently vegetated by willows, white poplar, and elms. In torrential reaches subject to summer low water, tamarix (T. africana) and rose bays (Nerium oleander) are common. Large gray willows were quite common in the lower Tagus, their disappearance being related to rice cultivation. Exotic invaders (Eichhornia crassipes, Myriophyllum aquaticum) show high local densities and may outcompete the native Potamogeton crispus, Ceratophyllum demerson and M. spicatum (Ferreira & Moreira 1999). Small streams in the flat-lands of the southern Tagus are inhabited by mayflies of the genera Baetis, Caenis, Paraleptophlebia, and Ephemerella, stoneflies such as Isoperla, and the Coleoptera Oulimnius. In the north at Serra da Malcata, small streams have a higher diversity of macroinvertebrates than streams in the south. Taxa include caddiflies such as Atripsodes (Lepidostomatidae) and Tinodes (Pychomyiidae), dragonflies (Chalcolestes), Notonectidae (Notonecta), coleopterans (Oulimnius, Helophorus, Laccobius, Anacaena, Dytiscus), stoneflies and mayflies (Caenis, Choroterpes, Cloeon), and common dipterans (Chironomidae, Tipula) (INAG, unpublished data). Among the introduced invertebrates, four species are relevant in terms of biomass, numbers, potential impact or their geographic distribution: the freshwater asiatic clam C. fluminea, the Chinese mitten crab Eriocheir sinensis, the Louisiana red crayfish P. clarkii, and the snail Potamopyrgus jenkinsi. M. auricularia was once abundant in the Tagus basin (Araujo & Ramos 2000). The rice fields are important habitats for a large variety of invertebrates including P. clarkii, Gastropods, Oligochaetes, Daphnia, Siphlonurus, Lestidae, Gerridae, Anisops, Dytiscidae, Hydrophilidae, Coelostoma, Tipulidae, Culicidae and Chironomidae. The Tagus catchment is transitional between the north containing some central European fishes and the south inhabited by endemic species. It forms the southern limit for B. bocagei, Rutilus arcasii, Leuciscus carolitertii and C. calderoni, and the northern limit for Barbus comizo, B. microcephalus and Rutilus lemmingii. The subspecies of C. polylepis also have their distribution limits in the Tagus basin (Doadrio et al. 1991). Today, three native Iberian Peninsula fish (B. bocagei, C. polylepis and L. pyrenaicus) can be found in the Tagus basin, in particular in the rivers Ambroz, Guadiela, Jarama, Lozoya, Sorbe, Tajuna and upper Tagus (Martınez Capel & Gracıa de Jalon 1999). In Portugal, native fishes include the barbel Barbus comiza, the endemic cyprinid Chondrostoma lusitanicum, and the endemic R. macrolepidotus and R. alburnoides. Good populations of brown trout (Salmo truta fario) can be found in the headwaters of some tributaries (Mayo-Rustarazo et al. 1995). Carmona et al. (1999) highlighted the distinctive fish community in the Alagon River, where the local endemic Cobitis vettonica is found. C. polylepis, B. bocagei and Tropidophoxinellus alburnoides have a wide distribution throughout the lower Tagus. C. paludica, L. pyrenaicus and R. lemmingii usually prefer lowland reaches with slow currents. Non-native fish species in the Manzanares comprise 80% of the fish

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community (Morillo Gonzalez del Tanago et al. 1999). Migratory fish species (such as P. marinus and Lampreta fluviatilis) can only move upriver until Alcantara dam. At least six species of amphibians and reptiles inhabit the Tagus estuary, including the Iberian or Portuguese Painted Frog (D. galganoi), the Common Tree Frog (Hyla arborea), the Mediterranean Pond Turtle (Mauremys leprosa) and the Iberian Spadefoot Toad (Pelobates cultripes). The geomorphology of the upper Tagus provides habitats for several birds of prey (Aquila chrysaetos, Neoprhon percnopterus, Hieraetus fasciatus, Bubo bubo and Gyps fulvus). The Tagus wetlands are highly important for wintering populations of avocet, black-tailed godwit, redshank, grey plover, shoveler and lesser black-backed gull (Moreira 1999). Other species that appear seasonally in the estuary are Egretta garzetta, Charadrius alexandrinus, Charadrius hiaticula, Calidris alba, Limosa limosa, Arenaria interpres, Anas crecca, Anas lypeata, Recurvirostra avosetta, Limosa lapponica, Numenius arquata, Tringa totanus, Larus ridibundus, Larus fuscus, Pluvialis squatarola, Calidris canutus, Calidris alpine, and Anas platyrhynchos (Moreira 1999). Migratory birds and birds of prey use the Natural Park of Tejo International as refuge and for nesting, including the Egyptian vulture, Short-toed eagle, Bonelli’s eagle and the Black stork. In the alluvial sediments and fluvial islands in the middle river are found Circus aeruginosus, Ciconia nigra, Falco peregrinus and numerous limnetic birds like Nycticorax nycticorax, Egretta garzetta and Bubulcus ibis. In the Natural Park of Tejo International, some protected species are found, including the otter, the small spotted Genet, the wild cat, elk, and the Egyptian mongoose. Water moles are present in pollution-free mountain streams. The Eurasian otter and the European polecat have been recorded in the estuary.

4.6.6. Management and Conservation Management of the Tagus catchment is strongly influenced by water needs for irrigation. The total irrigated land increased from 9340 to 230 720 ha since 1940. Reservoir capacity in the upper and middle Tagus is 12 000 Mm3 and in the overall catchment is 14 500 Mm3, corresponding to 74% of the average annual runoff. River flow is strongly regulated. The Tagus is also used to transfer water from the Entrepenas-Buendıa reservoir in central Spain to the Segura basin (so-called Tagus-Segura Transfer), being in operation since 1979 to meet the needs for human consumption and irrigation in the Segura basin. Part of the flow (<5%) is redirected to the Guadiana basin for the maintenance of the Natural Reserve of Tablas de Daimiel. The Tagus–Segura Transfer has caused severe impacts in both river basins. The UNEP (2003) report indicates that the water demand in the catchment has doubled in the last 24 years to 500 Mm3 because of irrigation and tourism. Water no longer flows in some places in summer, and the legal minimum flow of 6.0 m3/s is sometimes not enforced.

PART | I Rivers of Europe

The Natural reserve of the upper Tagus comprises the headwaters of the Tagus and the main tributaries of Hoz Seca, Tajuelo, Cabrillas, Gallo, Bullones, Arandilla and Ablanquejo. There are two fluvial karstic systems in the south, The Barranco of the Dulce River and the Salado river valley. The Henares River has an excellent riparian forest and special geomorphology. Several reaches with Atlantic riparian forest are proposed as LICs on the Canamares, the Tajuna, Valfermoso de Tajuna and Brihuega rivers. Other important riparian areas considered as LICs are along the Alberche and middle Tagus (Tagus in Castrejon, Barrancas of Talavera). The Tagus estuary encompasses 18.2 km2 of marshland covered with halophytic vegetation and is periodically flooded with saline water. In the upper estuary, the saltmarshes have been a Nature reserve since 1976 (Reserva Natural do Estuario do Tejo). In the lower Tagus, the marsh ‘Paul do Boquilobo’ is a Biosphere reserve. The Tagus basin is managed by the Hydrologic Basin Authority of the Tagus (CHT) in Spain and by the National Institute for Water (INAG) in Portugal. Preliminary studies had to be completed by December 2004 by each river basin district, including the identification, delimitation and characterisation of water bodies, research into the anthropogenic pressures, and the selection of potential reference sites. A large study on the biological and chemical quality of the river, classified 30% of the catchment as being in a very good ecological state, and 30% to be strongly polluted (Moreira et al. 2002). The environmental problems are mainly related to industry in the estuary, the presence of dams, river abstraction for irrigation, and levees. As a consequence, riparian areas have decreased nearly 52% in the Tagus basin and 88% in the Jarama due to changes in land use (mainly agricultural activities in the floodplain) and changes in the hydrological regime (Molina Holgado 2002). Several reservoirs are eutrophic, and some even hyper-eutrophic (Pena-Martınez & Serrano-Perez 1994; Bai~ao & Boavida 2005).

4.7. ADDITIONAL RIVERS €era 4.7.1. The Agu The Ag€uera drains 145 km2 in the Cantabric region in north Spain, between the Basque Country and Cantabria. It has a typical Atlantic-influenced flow regime (Atlantic ecoregion) with a humid oceanic climate and high discharge relative to its size. Most streams like the Ag€uera also have high gradients. The Ag€uera is one of the most natural rivers in the region and one of the best studied in the Iberian Peninsula, especially from a functional viewpoint. The Ag€uera flows through Cretaceous materials, especially sandstones. Limestones dominate its middle catchment and the infiltration water here forms springs and diffuse groundwater sources to surface waters. The Ag€uera receives 1500 mm precipitation annually, and rains are regularly distributed throughout

Chapter | 4 The Iberian Rivers

the year. The average annual temperature is 14.3 C, ranging from 9.8 C in January to 18.5 C in August (Photo 4.6). There is a low human density in the catchment with larger villages having 2000 people, although the coastal area is becoming increasingly populated in recent years. Primary activities in the catchment include forestry, livestock and agriculture. Nearly 50% of the catchment is covered by tree plantations, in particular Eucalyptus globulus and Pinus radiata, especially in the lower basin. The remaining landscape is occupied by meadows and grasslands, and 17% by native oak and evergreen oak forests. Interesting saltmarshes and sand dunes form at the mouth of the Ag€ uera. This basin was formed by Pyrenean orogeny that caused several foldings and faults, and the north-northwest flow of the main channel. The river originates at 450 m asl and is 30 km long. Channels are mostly straight and incised, and disconnected from the floodplains. The annual average discharge of the Ag€uera ranges between 2 and 4.5 m3/s at the mouth, and interannual variability is low. The steep gradient causes torrential flows at any time in response to rains. The Ag€ uera has relatively clear, moderately mineralised waters. The longitudinal variability of its chemistry reflects the local geology as well as land use and sewage inputs. The upper river is low in mineralization, which later increases in the middle reach because of calcareous geology, especially during low flows. Nutrient content increases with the increase in conductivity. Nitrate values are moderate, rarely

PHOTO 4.6 Ag€ uera River in its middle section (Photo: Sergi Sabater).

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exceeding 1.2 mg/L, and decrease in the middle and lower sections under low flows. Phosphates are low in the headwaters and middle sections of the river, except downstream of villages. In the lower river, nutrients increase because of the influence of towns and lack of water treatment plants. This situation has improved somewhat in the last few years. Oxygen levels can be low in tributaries receiving dairy sewage, and phosphorus concentrations are 10-fold higher than in the main river (Elosegui et al. 1995). Algal biomass is low in the Ag€uera headwaters, being dominated by diatom assemblages. Downstream, when the shade is reduced, filamentous algal communities dominated by Cladophora are abundant. Algal biomass is higher during stable flow periods, although light availability limits biomass in shaded reaches of the river (Elosegi et al. 2006). Macrophytes other than mosses or liverworths are rare in the Ag€uera. Riparian forests are generally present and in a good state along the Ag€uera, and consist of mixed forests of alder, ash and oak, as well as plantations of London pine. In moist areas, rare ferns like Woodwardia radicans or Trichomanes speciosum can be found. Macroinvertebrates are diverse in the middle and lower reaches of the Ag€uera, dominated by collectors and generalist invertebrates (Riano et al. 1993). The most abundant groups are Oligochaeta, mayflies, chironomids and elmid beetles. Filterers (Simuliidae and Hydropsychidae) occur below pollution inputs, and shredders (Echinogammarus

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and several stoneflies) are abundant in the forested headwaters. Shredders make up >25% of the macroinvertebrate biomass in the headwaters. The life cycle of most shredders is asynchronised with the period of leaf fall (Basaguren et al. 1996). Nutrient pollution based on the BMWP bioassessment index seems to have little effect on the macroinvertebrate community, except for some areas in the middle and lower river. Fish communities are relatively diverse, although densities seem to have decreased during the last few years. Brown trout (S. trutta) and minnow (Phoxinus phoxinus) are the main species found along most of the river. Salmon (Salmo salar) reproduces in some sections, and Chondrostoma toxostoma is found in slow waters. The metabolism and functioning of the river is tightly related with the dynamics of organic matter entering and decomposing in the system (Elosegi et al. 2006). The replacement of native forest by eucalyptus plantations has reduced nutrient levels, increased inputs of oils and phenolics, and changed the timing of leaf fall (being more evenly distributed during the year). These changes certainly influence the macroinvertebrate fauna, although the high retention of organic matter in the Ag€ uera may reduce the effect on consumers (Pozo et al. 1997). The Ag€ uera has a large volume of large woody debris (Diez et al. 2000). Extensive knowledge of the river made possible to detect the effects of drought as well as that of severe clear-cuts in the basin. Water quality is an issue below the two largest villages (Trucios and Guriezo) as well as in some small tributaries. Promising is that some wastewater treatment plants will begin operating in the near future and should improve the nutrient situation and assist the self-purification capacity of the stream (Elosegui et al. 1995). Intensive forestry operations on eucalyptus plantations are a serious problem in the catchment. Parts of the headwaters, middle and lower sections are Natura 2000 sites, and part of the catchment also will be included in the Natural Park of Armanon, to be created in 2007.

car 4.7.2. The Ju The J ucar catchment is in the eastern Iberian Peninsula and ucar has nine major covers an area of 21 208 km2. The J tributaries (Cenia, Mijares, Palancia, T uria, J ucar, Serpis, Marina Alta, Marina Baja and Vinalopo). The basin has a diverse and irregular hydrology, common to most Mediterranean rivers. The J ucar is densely populated (4.4 million inhabitants in 2001), plus 1.5 million in tourists. The hydrological resources of the J ucar are estimated at 3400 Mm3/year and the total water demand of the basin is 3650 Mm3/year, mostly for agricultural use, creating a large water deficit. Agricultural water demand is high because 22% of the 1.8 million ha of agricultural land is irrigated (Photo 4.7). Geographic differences cause climatic irregularities between the north and south, and the east and west regions of the basin. The average annual rainfall is 500 mm, ranging

PART | I Rivers of Europe

from 250 mm in the south to 900 mm in the north. The headwaters have the lowest mean temperatures and the highest precipitation in the basin (Una: 5 C, 929 mm). In the La Mancha plain (southwest), mean annual temperature is 15 C, but differences between minimum and maximum temperatures can approach 20 C due to the Mediterranean continental climate. The Jucar discharge shows high seasonality (maximum in autumn and winter, and minimum in summer) and interannual variability. In littoral areas, rainfall is dominated by humid easterly winds that can lead to local intense rains at the end of summer. The climate causes frequent floods at the end of summer and autumn, although these are mostly attenuated by reservoirs. In October 1982, a flash flood caused the breach of Tous dam in the lower Jucar that claimed 12 casualties. Average river discharge at El Picazo (1952–2006; CHJ) is 82.7 Mm3, ranging from a maximum of 295 Mm3 and minimum of 12 Mm3. Discharge has decreased between the period 1952–1983 (100 Mm3) and the period 1984–2006 (58 Mm3). The intensive use of water has resulted in deep morphological alterations in the catchment. A total of 43 reservoirs are presently found in the basin, used mainly for irrigation and energy generation. Of these, 18 are on the Jucar, 11 on the Mijares, and 4 on the Turia. Small dams for irrigation are also distributed along the drainage network. Mean water temperature in the middle and lower river is 16.2 C (ranging from 7.2 to 24.6 C), and conductivity is 800 mS/cm. The mean ammonia concentration is 0.07 mg/ L (maximum = 0.36 mg/L) and nitrate reaches 10 mg/L. Total phosphorus concentration is 0.07 mg/L with maximum values of 0.64 mg/L. A total of 128 species of macrophytes, 266 species of diatoms and 390 species of macroinvertebrates were listed for the Jucar catchment. Notably, the endemic crustacean Dugastella valentine is found in the natural reserve of Pego-Oliva. The macroinvertebrate comunity indicates that reaches with good ecological status are mostly in the high altitudes, while those at middles altitudes (800–200 m asl) are regulated but have good or acceptable ecological quality. Reaches in the lowlands (<200 m asl) have poor or bad quality (Martınez Mas et al. 2004). The Jucar basin has a diverse fish community. Trout (S. trutta) is common in the headwaters and Barbus and L. pyrenaicus in the middle and lower reaches. The presence of non-native species is low in the headwaters of the J ucar, Turia and Mijares, but in the middle and lower reaches there is a higher presence of cyprinids. Blennies (S. fluviatilis) have been observed in the Jucar as well as in the tributaries Cabriel and Escalona, and in several irrigation channels (Hernandez et al. 2000). V. hispanica and A. iberus are two endemic fishes found in fresh and brackish water areas, as well as in channels and ponds along the littoral. These species have disappeared from the main lagoons due to G. holbrooki that was introduced in the Albufera 80 years ago to fight paludism. It uses the same habitats as A. ibericus and V. hispanica (Soria 2006).

Chapter | 4 The Iberian Rivers

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PHOTO 4.7 J ucar River at Alcala de Jucar (Photo: Sergi Sabater).

There are numerous valuable wetlands with protective status in the catchment, and four of these are included under the RAMSAR agreement. The L’Albufera de Valencia is a natural park that includes the coastal line between the Turia River and Cullera Mountains, the Albufera lake, and the rice fields around the lake up to the Jucar River. Salinity of the Albufera lake is near 2 g/L. The lake area is visited by >250 species of birds and some 90 of these nest in the area. The other three RAMSAR sites are the Prat de Cabanes-Torreblanca, the Marjal de Pego-Oliva, and the Santa Pola Saline. Besides these, another 48 wetlands have been inventoried in the basin (Nebot 1997). Proposed protected areas include the Hoces del Cabriel and Hoces of the J ucar. The Jucar River basin was selected as The Pilot River Basin of the WFD in Spain in 2002 as part of the European Water Framework Directive as managed by the Jucar Water Authority (CH J ucar 2000).

4.7.3. The Mondego The Mondego is entirely in Portugal with a total length of 237 km and drainage area of 6670 km2. It originates at Serra da Estrela, the highest mountain range in Portugal. The river is traditionally divided into three sections. The upper Mondego is 31 km long with a mean slope of 2.5%

and lies partly within a glacial valley. The middle sector is the largest at 168 km with a slope of 0.4–0.1%. This sector is constrained by a steep and closed valley. The final sector of 38 km flows from the city of Coimbra where a narrow valley opens to a wide alluvial plain with low slope (0.05%). Here, it flows over Meso-Cenozoic limestone. The Mondego lies in a transition area of Atlantic and Mediterranean climate with an average basin temperature of 13 C and annual precipitation of 1130 mm, 70% of which occurs from October to March. Nearly half a million people currently live in the Mondego catchment. Agricultural activities are intense in the lower Mondego valley, whereas wood extraction for pulp production is important in the remaining basin (Photo 4.8). Mean annual discharge of the Mondego is 88 m3/s, and the flow is highly seasonal and rainfall dominated. Measured runoff at Coimbra before construction of Aguieira dam ranged from 1 to 3000 m3/s (Pardal et al. 2002). Highland tributaries are acidic (pH values occasionally <5) and poorly mineralised (conductivity <50 mS/cm, alkalinity <20 mg/L). In the lower section, the geology typically causes water pH >7, conductivity >200 mS/cm and alkalinity >100 mg/L (Feio 2004). There are 25 reservoirs along the Mondego and its main tributaries that are used for energy production and irrigation purposes. The Aguieira is the main reservoir producing electricity and regulating flows. Before reservoir construction, in particular the Aguieira, Raiva and Ponte-A¸cude, the river

140

PART | I Rivers of Europe

PHOTO 4.8 Mondego at Serra de Estrela (Photo: Manuel Gra¸ca).

transported large amounts of sediments that even elevated the riverbed. A total of 388 taxa of phytoplankton were recorded in the basin, 232 of them being diatoms (Santos et al. 2002). Aquatic plants include the curly pondweed, the pond water-crowfoot, the pond water-starwort, water milfoils and the introduced parrot feather. Widely spread riparian trees include ash, black-poplar, willows and alder. Over 200 invertebrate taxa were cited in recent studies of the river (Feio 2004). Due to low pH, crustaceans and gastropods are rare in the upper basin, whereas stoneflies (e.g. Leuctra sp., Nemoura sp., Perla sp.) and caddisflies (e.g. Sericostoma sp., Hydropsyche spp., Lepidostoma hirtum, and Rhyacophila spp.) are common. In the middle and low sections, these species are replaced by mayflies (Habroflebia, Habroleptoides, Ephmerella sp. Serratella sp., Caenis sp.), other caddisflies (Chimarra marginata, Cheumatopsyche lepida, Lype auripilis) and some gastropods (e.g. Ancylus fluviatilis, Potamopyrgus spp., Physa sp. and Lymnae sp.) (Gra¸ca et al. 2004, Feio 2004). In the lowlands, the shrimp Athyaephyra desmarestii and the introduced Louisiana crayfish P. clarkii are widespread. A total of 19 fish species were identified in the basin (Pardal et al. 2002). Taxon richness is highest in the lower section. Important native species include the ruivaco (R. macrolepidotus), escalo (L. carolitertii), Iberian barbel (B. bocagei) and Iberian nase (C. polylepis). Common intro-

duced fish include the goldfish, carp, gudgeon, rainbow trout and mosquito fish. The Mondego is one of the most important rivers in Portugal for four commercially important diadromous fish, the sea lampre, allids shad, twaite shad, and eel. Sixteen species of amphibians are found in the basin, with high densities in the lowland section because of the freshwater marshes. One distinctive species is the goldstriped salamander (C. lusitanica). Two aquatic reptiles occur in the Modengo basin, the water lizard Lacerta scheibreri and the freshwater tortoise M. leprosa. Nearly 70% of the Mondego basin is classified as being in good biological and chemical condition. Critical conditions are only found in the lowland section (Moreira et al. 2002). The lower Mondego has been straightened and the banks reinforced for flood control. Due to agricultural activities, the area is heavily impacted from runoff of nutrients and pesticides, which end up in the estuary. The connectivity between the river and its floodplain was lost because of bank reinforcements that facilitated plant invasions in the lower Mondego. Today, nearly 10% of the recorded 212 riparian species are invasive species (Aguiar et al. 2001), and the dominant taxa are exotic. Other environmental problems include the invasion of the lower Mondego by the Louisina red crayfish. The 25 reservoirs along the river also block fish migration (mainly eels and lampreys). Lastly, large-scale Eucalyptus plantations have been associated with a lower diversity of aquatic hyphomycetes in some streams (Gra¸ca et al. 2002).

Chapter | 4 The Iberian Rivers

The Mondego catchment contains a wide variety of habitats for birds, particularly in the marshlands and estuary, where 137 species have been recorded. Many of these are winter visitors, including the wader (Dulin calidris), the lundin (Calidris alpina), and the avocet (Recurvirostra avoseta). Summer visitors include the black-winged stilt (Himantopus himantopus) and kentish plover (C. alexandrinus). Aquatic mammals in the river are represented by two main species: the otter (Lutra lutra) and the water mole (Galemys pyrenaicus).

4.7.4. The Segura The Segura basin is in the southeast Iberian Peninsula, covering an area of 19182km2. The Segura is 325 km long. The romans called the river Thader and the arabians WarAlabiat, which means ‘white river’. The term ‘white’ might be due to the presence of carbonate and sulfate deposits in some areas from gypsum marls and the arid and semi-arid conditions of the basin. The river originates in the Segura Mountains (1413 m asl) near the Guadalquivir source. The river flows from the Bethic Mountains to the east and into the Mediterranean Sea. The basin is delimited by the Bethic Mountains to the north and west (separating the Guadalquivir basin), the Prelitoral Murcian range to the southwest, and the Carche range to the east. The Segura is separated from the J ucar basin in the north by the Pinilla and Alcaraz ranges (Photo 4.2). The Segura is in the most arid zone of the Iberian Peninsula. Rainfall is irregularly distributed in the year and large floods can occur that affect human settlements throughout the drainage. In spite of this, a diversity of climates and hydrologies are found within the basin, being related to the basins diverse geography. Most of its water is collected in the upper river in the Segura, Mundo and, later on, the Guadalentın River. The middle reach has an arid landscape, with highlands and dry hills. A few green ‘oases’ make up the riparian zone along the river channels. The most important tributaries with permanent flow are the Madera, Tus and Mundo from the left side and the Zumeta, Taibilla and Guadalentın flowing from the right. Agriculture in basin is based on an irrigation system that has greatly altered surface flows. The Romans had already developed the Murcia’s orchard, still one of the most productive areas on the Iberian Peninsula. Orihuela was an important city during the Muslim occupation of the basin. Most people live in cities (such as Cartagena and Lorca) with <50 000 inhabitants. The largest city is Murcia with nearly 400 000 people. The basin has a large number of reservoirs that strongly regulate the flow of the river. High water demand has also resulted in overexploitation of subterranean aquifers in some areas. Today, land use in the basin is mainly agriculture (52%), the remaining landscape comprising forest or seminatural areas (42%) and urbanized areas 2.1% (CH Segura 2005). Agriculture is mostly developed in the

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main valleys of the Segura, Guadalentın and Campo de Cartagena. The Segura basin is within the Mediterranean climatic region. There is evidence that the basin was a refuge for thermophilous plants during the last glacial period (Carrion et al. 2003). Vegetation is sparse in many areas of the Segura river basin today. In the Chıcamo catchment, the vegetation is degraded and includes mostly slow-growing shrubs of Stipa tenaccissima, Thymus hyemalis and Rosmarinus officinalis. The vegetation in the Guadalentın valley is Mediterranean xerophytic scrub plants associated with limestone (Pistacia lentiscus, Olea sylvestris). Bedrock in the lower basin is composed of limestones and marls of Triassic to Cretaceous age, while the sedimentary alluvium comprises materials from the Upper Miocene to contemporary materials (conglomerates, sandstones, marls and gypsums). During the lower Pliocene, the Bajo Segura fault underwent significant activity that raised the southern part of the basin. Since then, sedimentation has been continental (alluvial and fluvial) except in the east where there is a transition to marine deposits. The complex geology of the catchment is responsible for a complex aquifer system that maintains flowing water in the river. In central areas of the basin, soils are poorly developed and highly erodible (Martınez-Mena et al. 1998). The basin exhibits high seasonality in climate with frequent drought, intensive rainfall and floods, periods of high temperatures and periods with low temperatures. Mountains (Segura, Alcaraz, Taibilla) in the upper catchment are oriented northwest to southeast, intercepting the Atlantic fronts from the west that causes rainfall to drastically diminish from northwest to southeast. Precipitation near the coast is <300 mm/year. Temperature ranges from 10 C in the Segura range to 18 C near the coast. The lowest temperatures occur in December and February, while the highest occur in July and August. In summer, winds from North Africa are common and can increase temperatures to 40– 45 C. In contrast, dry polar winds produce low temperatures and freezing conditions. Potential evapotranspiration increases from 600 to 700 mm in the upper basin to 950 mm in the middle and lower areas and 850 mm on the coast (at Mar Menor). The water deficit is high in the middle and lower reaches of the Segura, where demands are twice the resources available. The Segura captures most of water it transports from the upper catchment (Segura and Mundo Rivers). The river has a nivopluvial regime in the upper catchment and a Mediterranean fluvial regime downstream with major floods in autumn. Downstream, mainly intermittent tributaries, called ramblas, of low discharge and torrential regime enter the river. For example, the Chıcamo River drains a watershed of 502 km2 and is 60 km long, but it has stretches of flowing water separated by several discontinuous reaches in which surface flow is restricted to rainy periods. The Rambla del Moro is a more extreme intermittent tributary of the Segura, as 90% of the drainage network carries water only after

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heavy rainfall. Ramblas in southeast Spain include habitats with high biodiversity and various endemic species that are vulnerable to a range of human impacts (Gomez et al. 2005). Rain intensity in the basin causes the flow to be mostly Horton runoff, resulting in the formation of gully channels (Vandekerckhove et al. 2000). Salinity and conductivity in the Segura are among the highest of Iberian rivers. High values (ranging from 1 to 10 mS/cm; Toro et al. 2002) are due to the high solubility of the marl substrate as well as to high evaporation and low precipitation. The large variation in discharge is responsible for seasonal variation in water salinity and nutrient content. Conductivity and oxygen also show major changes from the headwaters to the mouth. For instance, the mean conductivity of the Segura is 400 mS/cm at the city Elche, while at Orihuela it reaches 2634 mS/cm (25 year record). In the headwaters, nutrients average 1.2 mg/L nitrate, 0.12 mg/L ammonium and 0.02 mg/L phosphate, whereas values increase to 2.5 mg/L nitrate, 2.5 mg/L ammonium and 0.64 mg/L phosphate downstream at Orihuela. The Mundo River has the lowest nutrient content in the catchment. Suspended solids are typically 100 mg/L with peaks from floods reaching 4400 mg/L (Elche) to 14 000 mg/L (Orihuela). High salinity and nitrates are related to the nitrogen-rich content of the sedimentary marl substratum (Vidal-Abarca et al. 2000). In ramblas, a marked increase in nutrient content (nitrate and phosphate), alkalinity and suspended solids occur after floods, while conductivity decreases due to the dilution effect of high discharge (Ortega et al. 1988). Aquatic and riparian biodiversity in the Segura is related to the different flow regimes in the different rivers and streams in the catchment. Salix sp., Populus sp. and U. minor are the most representative species in permanent waterbodies, and Tamarix sp. and N. oleander may also occur. The most abundant macrophytes in permanent waters are Typha domingensis, Phragmites australis and Juncus sp. Along most rivers on the left side, shrubs are the natural vegetation and much land is dedicated to citrus and horticultural crops. Riparian vegetation is sparse because of frequent floods, with pockets of P. australis, T. canariensis and Juncus maritimus being found. Primary production and respiration in the Segura is high due to its aridity and extreme Mediterranean character (Suarez & Vidal-Abarca 2000, Velasco et al. 2003). Aquatic primary producers found in the Chıcamo include the macrophyte Chara vulgaris (mean annual biomass of 25 gC/m2) and diatoms on fine sediments (Nitzschia, Amphora, Navicula, Gyrosigma and Pleurosigma; mean annual biomass of 5 gC/m2). In comparison with other Mediterranean rivers, the Segura shows a strong gradient in salinity and temperature that can be selective for certain groups of macroinvertebrates such as Plecoptera, Ephemeroptera and Trichoptera. Invertebrate assemblages show adaptations to the fluctuating flow regime of ramblas (high floods, drought). Life cycles of macroinvertebrate are adapted to temporary waters (high P/B ratios, multivoltine life cycles and asynchronous recruit-

PART | I Rivers of Europe

ment) (Peran et al. 1999). The macroinvertebrate community of the upper Segura affected by regulation has a lower diversity than in the unregulated Mundo (Torralva et al. 1996). In the upper Segura and Mundo, salmonids, especially trout, are the main fish. Native salmonids are currently being replaced by introduced rainbow trout. Barbus sclateri is an abundant endemic fish in the mid-southern Iberian Peninsula, including the Guadiana, Guadalquivir and Segura Rivers (Elvira 1995, Doadrio 2001). Fishes in the middle reach of the Segura are characterized by the barbel, coexisting with C. polylepis, G. gobio, S. pyrenaicus and Oncorhynchus mykiss (Oliva-Paterna et al. 2003). Streams with intermittent flows have the lowest fish condition values, while sites with permanent flow have the highest (Oliva-Paterna et al. 2003). The Natural Park of Sierra del Segura, Cazorla y Las Villas (Biosphere Reserve) lies in the headwaters, and the Spanish Ibex Capra pyrenaica is found here. Sensitive areas to nitrate contamination are Laguna del Hondo, Salinas de la Mata, Salinas de Torrevieja, and Mar Menor. The Hydrologic Basin Authority of the Segura (CHS) is responsible for the water management of the catchment and has developed a hydrology plan for the basin. The needs and uses of water was a primary objective in the hydrologic plan due to water scarcity in the region.

4.7.5. The Ter The Ter drains about 3010 km2 in northeastern Spain. Its headwaters are at 2500 m asl in the Pyrenees and it flows 208 km to its mouth in the Mediterranean Sea. The main tributary in the upper catchment is the 30 km long Freser River. In the middle reach, the Ter receives small tributaries such as the Gurri and Major. In this reach are three reservoirs (Sau, Susqueda and El Pasteral; total capacity of 402 Mm3) that strongly influence flow and water quality in the lower river. In the lower river, the main tributary is the Onyar with a Mediterranean flow regime. Here is located Lake Banyoles, a mid-altitude lake and one of the largest in Spain. It has a karstic origin and is fed mainly by groundwater. The Ter is a 5th order river at its mouth. Headwaters and some tributaries in the upper catchment flow over granite and slate, while others drain areas rich in gypsum. The middle and lower river, including many tributaries, drain calcareous and marl areas. Climate differs between the headwaters and the middle and lower parts of the catchment. Headwaters have an alpine influence with cold winters and mild summers, and annual rains ranging from 1000 to 1500 mm. In upland sub-basins, the climate is milder but with abundant rain. In the lowlands and near the mouth, the climate is Mediterranean, with dry summers and mild winters and a rainfall between 700 and 800 mm (Sabater et al. 1995). The Ter basin is strongly influenced by human activity. The first human settlements date from 120 000 to 90 000 years BC, but the first important changes began in the Middle

Chapter | 4 The Iberian Rivers

Ages with the development of wool mills and iron forges that caused major deforestation over large areas. With the Industrial Revolution in the 19th century, human activity and transformation of the river catchment progressively increased. Along the river are a large number of small dams and bypass channels for the generation of water power that has prevailed until today. Regulation of the river was complete by the 1950s with the construction of three large reservoirs in the middle reach. This reservoir system is used for hydroelectric production and water supply for the city of Barcelona and surroundings (700 million litres per day). Agricultural and farming activities are common in the basin. While higher rainfall makes irrigation unnecessary in the upper basin, irrigation is common in the middle and lower parts and is controlled by a series of channels. Farming has caused pollution of both surface and ground waters. Presently, the Ter has only some 1st and 2nd order tributaries that remain undisturbed, whereas the remaining network has been subject to intensive and extensive human pressure that significantly reduced the quality and quantity of the river and riparian habitats. Flow patterns differ between the upper and lower sections of the river. The headwaters have a nivopluvial regime with low flows in winter and higher discharge in spring from snow melt. In the middle and lower parts of the river, discharge is mainly determined by rainfall but regulated by the reservoirs. In these sections, the flow regime is Mediterranean. Flow increases after autumn rains often result in floods. Precipitation is scarce in summer and discharge can decrease substantially in the lower Ter. The average annual discharge of the Ter is 840 Mm3, but there is large interannual variation. Annual water flows from 1955 to 1988 (Armengol et al. 1991b) show two periods of maximum water flow in May (28.6 Mm3) and November (17.6 Mm3); and two minima in August (11.4 Mm3) and February (14.2 Mm3). Water chemistry of the Ter is influenced by the complexity of the catchment and the variability in discharge. In the headwaters, the bedrock is siliceous and the human density is low. Here the concentration of dissolved solids (TDS) are <20 mg/L. Upstream of the reservoirs, the TDS concentration is 50 mg/L and is even higher in polluted tributaries (>50 mg/L in the Gurri). The reservoirs cause a reduction downstream with TDS at 20 mg/L (2000–2005; ACA data base). The chemistry of the Ter waters shows a continuous downstream trend from highly bicarbonate-dominated to chloride-dominated waters (Sabater et al. 1995). Conductivity increases from <100 mS/cm in the headwaters to 600 mS/cm in the lower river (2000–2005; ACA data base), being related to the increase of rock weathering and to higher human activity in the middle and lower river. Nutrient concentrations are related to land use activities and hydrology. The influence of lithology on water chemistry is significant only in the headwaters, while factors related to human activities are more important downstream (Sabater et al. 1990). The N:P ratio (N as dissolved inorganic nitrogen

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and P as reactive soluble phosphorus) is high in the headwaters but decreases downstream, in particular during summer. Values of N:P <30 occur in areas influenced by human activities. Phosphorus inputs from the river (at Roda de Ter) into Sau reservoir increased from 1968 to 1992 due to the increase of industrial and human activities in the basin (Armengol et al. 1999). This pattern shifted during the 1990s because of the completion of wastewater treatment plants. Dissolved inorganic nitrogen (DIN; mainly ammonium) behaved quite differently during that period until the treatment plants began biological treatment. Diatoms are the most widespread algae in the river (Sabater et al. 1995). Siliceous headwaters are characterized by Hydrurus foetidus and Ulotrix zonata ; in the mineralized middle stretches Gomphonema spp., Navicula spp. and Nitzschia spp. are dominant; below the reservoirs the community shifts to a dominance of Achnanthes lanceolata, Amphora pediculus, Melosira varians, Nitzschia dissipata and Fragilaria ulna; in calcareous streams encrusting Cyanobacteria and zygnematales are dominant; and at the mouth and in some polluted areas the diatoms C. meneghiniana, Gomphonema parvulum, Navicula gregaria, Nitzschia palea and N. umbonata are most abundant. Macrophytes are important primary producers in some sections of the river. Below the reservoirs, the macrophytic community is dominated by Myriophyllum verticillatum, P. crispus and P. nodosus. Myriophyllum spicatum and P. pectinatus develop in polluted reaches in the lower river. Bryophytes are mainly found in the headwaters, and Hygrohypnum spp., Philonotis spp., Barbula ehrenbergii, Cratoneuron commutatum, Fissidens rufulus, Fontinalis antipyretica, Cinclidotus fontinaloides, and Leptodictyum riparium are also common at times (Penuelas & Sabater 1987). Headwaters and some tributaries have a diverse macroinvertebrate community (Sabater et al. 1995). Gatherer-collectors, shredders and predators are dominant in the headwaters. Filter-collectors are common in those headwaters influenced by anthropogenic activities. Macroinvertebrates inhabiting the middle river are mainly grazers and filter-feeders, while the collector-gatherers less common in comparison with the upper catchment. The reservoirs affect macroinvertebrate distribution with filtering-collectors being abundant downstream. A pollution-tolerant community is common in the lower river and near the mouth. Two notable invertebrates in the basin are the mussel Unio sp. and the freshwater crayfish A. pallipes-lusitanicus, although both species are becoming less common due to pollution and catchment transformation. In the headwaters thrive the amphibians Euproctus asper and Rana temporaria, while in clean mountain tributaries the salamander (Salamandra salamandra) and the amphibians (Bufo bufo, Alytes obstetricans) are common. Otters (L. lutra) were common in the Ter up to 1950, but since then they have been practically eliminated due to habitat destruction and hunting. Today, the otter has been replaced in some areas by the non-native American mink (Mustela vison).

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The most common fish in the Ter headwaters and mountain tributaries are trout (S. trutta) and barbel (Barbus meridionalis). Downstream, in slower and more temperate waters, the chub (Leuciscus cephalus), barbel and some introduced fishes (B. graellsii, Cyprinus carpio, Tinca tinca) dominate. In the lower reach and near the mouth, some estuary fishes are present (Sostoa 1990). Up to 26% of the fish species have disappeared in the Ter basin from 1940 to 1993 (Camprodon et al. 1995), 33% of them being native. The main causes for the decline include pollution, dam construction, sand extraction and intensive fishing. There are several protected areas in the basin under local management. The Guilleries-Savassona reserve includes a part of the upper Ter as well as that of one main tributary, the Riera Major. It is characterized by its singular geology (Cingles de Tavertet and Montorer). Its riparian habitat hosts several amphibian species (such as Triturus marmoratus, S. salamandra, B. bufo, Rana perezi) and birds (Ardea cinerea, Phalacrocorax carbo, Larus cachinnans). The Montesquiu reserve area is in the middle-upper basin and comprises an important calcareous area with remarkable slab-bottom streams. In the lower Ter, there is a small protected area that includes valuable wetlands and the estuary (Ter Vell). A marine reserve (Medes Islands) is directly affected by the Ter’s water plume. Several areas distributed along the basin are trying to achieve special protection to maintain the Ter basin as a natural green corridor. The Water Framework Directive is progressively being implemented in the Ter basin by the Catalan water authority (ACA; Agencia Catalana de l’Aigua).

4.7.6. Conclusions and Perspectives The Iberian Peninsula has a variety of climates and geological settings that are expressed in a diversity of fluvial regimes, geochemistry and biological diversity. The human influence in the Iberian Peninsula has existed for many centuries, well before the Romans conquered the Peninsula. These two factors need to be taken together to understand the present situation that defines the Iberian rivers. Most of the Iberian Peninsula is semi-arid in terms of rainfall. Although the Mediterranean basin is smaller than the Atlantic basin, there is a northeast to southwest gradient in aridity that affects both. This effect causes some Iberian rivers to have lower water flows than similar systems throughout Europe, and is extreme in the southernmost Mediterranean streams that can be intermittent during the summer. In these streams, rains are concentrated in short periods of time and can cause catastrophic floods. The natural shortage of water and the irregularity of flow in the rivers have influenced the historical relationship between the rivers and humans. Hydraulic infrastructures were already implemented by the Romans and Arabs, and reached a construction peak during the 20th century with the construction of hundreds of medium and large reservoirs. Agri-

PART | I Rivers of Europe

cultural use and protection against floods promoted the construction of large dams in the Iberian Peninsula. The magnitude of infrastructure and its associated management have had lasting and irreversible effects in the geomorphology of many rivers of the Iberian Peninsula. Presently, the Iberian Peninsula watercourses are highly regulated, possibly among the highest in Europe. Additional effects beyond flow regulation include a reduction in floodplain areas, a reduction in meanders and the loss of riparian zones, as well as a lowering of the water table in several basins. In the Tagus, up to 55% of the original riparian zone is gone and nearly 90% in some of its tributaries. In the Guadiana, a decrease in the water table is threatening unique ecosystems such as the Tablas de Daimiel. Its restoration is difficult because it would demand a complete reappraisal of current agricultural practices. The natural water scarcity along with intense water use cause poor water quality in several stretches of most Iberian rivers. Water purification has been implemented in only a few basins, while, in others, it is limited to large cities and results in high inputs of organic matter and dissolved nutrients from smaller communities. This may be especially problematic during summer low flows. Although the progressive implementation of the WFD throughout Iberia is a hope to ameliorate this situation, the effects are still noticable in several systems and periods during the year. Eutrophication affects a large number of rivers in the Iberian Peninsula. A recent official report (Spanish Ministry of Environment 2005) stated that nearly 50% of the water stored in reservoirs is affected by eutrophication, in particular in the Tagus, Guadiana and Guadalquivir catchments. The percentage of subterranean waters affected by nitrate contamination in the Iberian Peninsula ranges between 15% and 19%. Iberian rivers are naturally rich in terms of their biota. Biogeographically, the Peninsula has taxa from Europe in the north and North Africa in the south. This boundary has historically influenced the high diversity of the inland waters in the Iberian Peninsula. The Guadiana basin holds up to 15 endemic fish. The high richness is true for Crustacea to fishes, and also algae and macrophytes (Margalef 1983). The Donana marshes in the Guadalquivir host an enormous biological diversity in a rather patchy aquatic environment. The biological richness in Iberian inland waters is currently under threat because of the high number of biological invasions. For example, the river Ebro has recently been invaded by the molluscs D. polymorpha and C. fluminea, but also by the fishes S. glanis and Ictalurus melas in its lower course. These invasions have resulted in a decrease in habitat diversity and in the number of native species. Water transfer between basins is a constant issue in the different hydrological plans that the governments develop to satisfy the high water demands (Plan Hidrologico Nacional 2001), and which would increase the possibility for species invasion. The management of rivers and their associated disturbance regimes has a cultural or societal component. The human presence and management of watercourses may have

Chapter | 4 The Iberian Rivers

very different affects depending on the cultural perception of rivers. People in arid and semi-arid regions have the least respect towards rivers since the rivers are often dry or have catastrophic floods, and are therefore viewed more as a danger than as a natural resource to be preserved. Moreover, there is a well-rooted perception that any water that reaches the sea is wasted. This perception being difficult to change, the progressive implementation of the WFD in the different basins will hopefully force a change in attitude towards the rivers, as well as the required administrative steps to secure their conservation and sound management.

Acknowledgements Most of the data shown in this chapter have been patiently collected by the staff of the different Hydrologic Basin Authorities (Spain) and INAG (Portugal), to whom we are extremely grateful. Arturo Elosegi read and corrected the section on the Ag€ uera River. Gemma Vidal assessed of the references. The writing of this chapter benefited from funding by the Commission of the European Community (Modelkey, Contract-No. 511237, GOCE).

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Sabater, F., Sabater, S., and Armengol, J. 1990. Chemical characteristics of a Mediterranean river as influenced by land uses in the watershed. Water Research 24: 143–155. Sabater, F., Guasch, H., Martı, E., Armengol, J., and Sabater, S. 1995. The Ter: a Mediterranean river case-study in Spain. In: Cushing, C.E., Cummins, K.W., Minshall, G.W. (eds). River Ecosystems of the World, Elsevier, Amsterdam, pp. 419–438. Sabater, S. 2000. Diatom communities as indicators of environmental stress in the Guadiamar River, S-W. Spain, following a major mine tailings spill. Journal of Applied Phycology 12: 113–124. Sabater, S., and Munoz, I. 1990. Successional dynamics of the phytoplankton in the lower part of the river Ebro. Journal of Plankton Research 12: 573–592. Sabater, S., Buchaca, T., Cambra, J., Catalan, J., Guasch, H., Ivorra, N., Munoz, I., Navarro, E., Real, M., and Romani, A. 2003. Structure and function of benthic algal communities in an extremely acid river. Journal of Phycology 39: 481–489. Sabater, S., Artigas, J., Duran, C., Pardos, M., Romanı, A.M., Tornes, E., and Ylla, E. 2008. Longitudinal variation of sestonic chlorophyll and phytoplankton assemblages in the Ebro River. The Science of the Total Environment 404: 196–206. Sanchez-Cabeza, J.A., Masque, P., Martinez-Alonso, M., Mir, J., and Esteve, I. 1999. Pb-210 atmospheric flux and growth rates of a microbial mat from the northwestern Mediterranean Sea (Ebro River Delta). Environmental Science and Technology 33: 3711–3715. Santos, L.M.A., Santos, M.F., Gil, M.C., and Pereira, M.J. 2002. Diversity of Freshwater Algae. Universidade de Coimbra, Coimbra. Serrano, L., Reina, M., Martın, G., Reyes, I., Arechederra, A., Leon, D., and Toja, J. 2006. The aquatic systems of Donana (SW Spain): watersheds and frontiers. Limnetica 25: 11–32. Smirnov, A.V. 2001. Vannella ebro n. sp (Lobosea, Gymnamoebia), isolated from cyanobacterial mats in Spain. European Journal of Protistology 37: 147–153. Sobrino, C., Matthiensen, A., Vidal, S., and Galv~ao, H. 2005. Occurrence of microcystins in the Guadiana estuary. Limnetica 23: 133–144. Sola, C., Burgos, M., Plazuelo, A., Toja, J., Plans, M., and Prat, N. 2004. Heavy metal bioaccumulation and macroinvertebrate community changes in a Mediterranean stream affected by acid mine drainage and an accidental spill (Guadiamar River, SW Spain). Science of the Total Environment 333: 109–126. Sole, A., Gaju, N., and Esteve, I. 2003. The biomass dynamics of cyanobacteria in an annual cycle determined by confocal laser scanning microscopy. Scanning 25: 1–7. Soria, J.M. 2006. Past, present and future of the Albufera of Valencia Natural Park. Limnetica 25: 135–142. Sostoa, A. 1990. Historia Natural del Paisos Catalans Vol. 11: Fundacio Enciclopedia Catalana, Barcelona, , 487 pp. Spanish Ministry of Environment. 2005. Perfil Ambiental de Espana. http:// www.mma.es/portal/secciones/info_estadistica_ambiental/estadisticas_info/perfil_ambiental_2005/. Sterk, G., Lopez, M.V., and Arrue, J.L. 1999. Saltation transport on a silt loam soil in Northeast Spain. Land Degradation and Development 10: 545–554. Suarez, M.L., and Vidal-Abarca, M.R. 2000. Aplicacion del ındice de calidad del bosque de ribera, QBR (Munne et al., 1998) a los cauces fluviales de la cuenca del rıo Segura. Tecnologıa del Agua 201: 33–45. Teran, M., and Sole Sabarıs, L. 1978. Geografıa general de Espana. Ariel, Barcelona, 549 pp. Toro, M., Robles, S., Aviles, J., Nuno, C., Vivas, S., Bonada, N., Prat, N., Alba-Tercedor, J., Casas, J., Guerrero, C., Jaimez-Cuellar, P., Moreno, J. L., Moya, G., Ramon, G., Suarez, M.L., Vidal-Abarca, M.R., Alvarez,

PART | I Rivers of Europe

M., and Pardo, I. 2002. Calidad de las aguas de los rıos mediterraneos del proyecto GUADALMED. Caracterısticas fısico-quımicas. Limnetica 21: 63–75. Torralva, M., Oliva, F.J., Ubero-Pascal, N.A., Malo, J., and Puig, M.A. 1996. Efectos de la regulacion sobre los macroinvertebrados en el rıo Segura (S. E. Espana). Limnetica 11: 49–56. Torrecilla, N.J., Galve, J.P., Zaera, L.G., Retarnar, J.F., and Alvarez, A.N.A. 2005. Nutrient sources and dynamics in a mediterranean fluvial regime (Ebro river, NE Spain) and their implications for water management. Journal of Hydrology 304: 166–182. UNEP. 2003. Freshwater in Europe. Facts, Figures and Maps. Early Warning and Assessment Reports. Urrea, G., and Sabater, S. 2008. Epilithic diatom assemblages and their relationship to environmental characteristics in an agricultural watershed (Guadiana River, SW Spain). Ecological Indicators. Val, R., Ninerola, D., Armengol, J., and Dolz, J. 2003. Incidencia de los embalses en el regimen termico del rıo. El caso del tramo final del rıo Ebro. Limnetica 22: 85–92. van Geen, A., Takesue, R., and Chase, Z. 1999. Acid mine tailings in southern Spain. Science of the Total Environment 242: 221–229. Vandekerckhove, L., Poesen, J., Wijdenes, D.O., Gyssels, G., Beuselinck, L., and De Luna, E. 2000. Characteristics and controlling factors of bank gullies in two semi-arid mediterranean environments. Geomorphology 33: 37–58. Velasco, J., Millan, A., Vidal-Abarca, M.R., Suarez, M.L., Guerrero, C., and Ortega, M. 2003. Macrophytic, epipelic and epilithic primary production in a semiarid Mediterranean stream. Freshwater Biology 48: 1408–1420. Vericat, D., and Batalla, R.J. 2005. Sediment transport in a highly regulated fluvial system during two consecutive floods (lower Ebro River, NE Iberian Peninsula). Earth Surface Processes and Landforms 30: 385–402. Vidal-Abarca, M.R., Suarez, M.L., Moreno, J.L., Gomez, R., and Sanchez, I. 2000. Hydrochemical characteristics of a river in a semi-arid climate (Rio Chicamo; Marcia). Spatial-temporal analysis. Limnetica 18. Vizcaıno, P., Magdaleno, F., Seves, A., Merino, S., Gonzalez del Tanago, M., and Garcıa de Jalon, D. 2003. Los cambios geomorfologicos del rıo Jarama como base para su restauracion. Limnetica 22: 1–8.

FURTHER READING ICONA, 1991. Peces continentales espanoles. Inventario y clasificacion de zonas fluviales., Madrid, 221 pp.

RELEVANT WEBSITES http://www.spea.pt/IBA: Sociedade Portuguesa para o Estudo das Aves. Important Bird Areas. http://www.mma.es/portal/secciones/acm/aguas_continent_zonas_asoc/: Spanish Environment Ministry, general information on inland waters. http://www.mma.es/secciones/biodiversidad/rednatura2000/rednatura_espana/: Natura 2000 network in Spain http://www.gencat.net/aca: Catalan Water Agency. Information about the internal water bodies of Catalonia (Ter and others). http://www.chtajo.es/: Confederacion Hidrografica del Tajo. Data, Maps and reports of the Tagus catchment http://www.chj.es/: Confederacion Hidrografica del Jucar. Data, Maps and reports of the Jucar catchment

Chapter | 4 The Iberian Rivers

http://ec.europa.eu/environment/water/index_en.htm. http://viso.ei.jrc.it/wfd_prb/index.html. The Jucar River basin as a pilot project of the European WFD. http://www.chebro.es/: Confederacion Hidrografica del Ebro. Data, Maps and reports of the Ebro catchment. http://www.chsegura.es/: Confederacion Hidrografica del Segura. Data, Maps and reports of the Segura catchment.

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http://www.chduero.es/: Confederacion Hidrografica del Duero. Data, Maps and reports of the Duero catchment. www.chguadalquivir.es Confederacion Hidrografica del Guadalquivir. Data, Maps and reports of the Guadalquivir catchment. http://www.chguadiana.es/: Confederacion Hidrografica del Guadiana. Data, Maps and reports of the Guadiana catchment.

Chapter 5

Continental Atlantic Rivers Jean-Pierre Descy Research Unit in Organismal Biology (URBO), University of Namur, Rue de Bruxelles 61, B-5000 Namur, Belgium

Introduction 5.1. The Meuse River Basin 5.1.1. Introduction 5.1.2. Historical Perspective 5.1.3. Biogeographic Setting 5.1.4. Physiography and Climate 5.1.5. Hydrology and Biogeochemistry 5.1.6. Aquatic Biodiversity 5.1.7. Management and Water Use 5.1.8. Conservation and Restoration 5.1.9. Protected Areas 5.1.10. Ecosystem Function 5.1.11. Conclusion and Perspectives Acknowledgements References 5.2. The Loire Basin 5.2.1. Introduction 5.2.2. Biogeographic Setting 5.2.3. Historical Setting 5.2.4. Physiography, Climate, and Land Use 5.2.5. Geomorphic Development of the Main Corridor 5.2.6. Hydrology and Temperature 5.2.7. Biogeochemistry 5.2.8. Aquatic and Riparian Biodiversity 5.2.9. Management and Conservation 5.2.10. Conclusions and Perspectives Acknowledgements References 5.3. The Adour–Garonne Basin 5.3.1. Introduction 5.3.2. Historical Perspective 5.3.3. Biogeographic Setting 5.3.4. Physiography, Climate and Land Use 5.3.5. Geomorphology, Hydrology and Biochemistry 5.3.6. Aquatic and Riparian Biodiversity Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

5.3.7.

Management and Conservation References

INTRODUCTION Atlantic rivers drain the western front of Europe, which is delineated by the Atlantic Ocean in the west; the English Channel in the north, the Hercynian massifs of the Ardennes and the Central massif in the northeast and east, and the high mountain range of the Pyrenees in the south (Figure 5.1a). The area includes the Aquitaine basin in the south and the Parisian basin in the north. A temperate marine climate characterizes this area. From northeast to southwest, mean temperatures range from 1 to 8 C in winter and from 17 to 21 C in summer. Annual precipitation is evenly distributed over the annual cycle. Mean annual precipitation varies from 530 mm in the central Parisian basin to 2000 mm in mountain ranges. The area of the western front contains parts of three biogeographic regions – Alpine (Pyrenees), Continental and Atlantic – and five ecoregions – conifer and mixed forests of the Pyrenees, Cantabrian mixed forests, western European broadleaf forests, and the northern and southern temperate Atlantic region. The Cantabrian mixed forest and the northern temperate Atlantic region include only marginal areas along the southern and northern border of the western front, respectively. Flow regimes of Continental Atlantic Rivers are characterized by low flow during late summer and high flow in January/February (pluvio–nival discharge regime). The four largest rivers in this area are the Rivers Loire, Garonne, Seine, and Meuse. The focus of this chapter is on the Rivers Meuse, Loire, Garonne and Adour (Figure 5.1a and b, Table 5.1). Despite belonging to the same region at the European scale, these rivers differ markedly from each other. While the R. Meuse in a typical lowland river is most of its course, which has been heavily regulated for navigation in large sections, the rivers Loire, Garonne and Adour, which flow entirely in the French territory, have retained more ‘natural’ 151

152

FIGURE 5.1 Digital elevation model (upper panel) and drainage network (lower panel) of Continental Atlantic Rivers.

PART | I Rivers of Europe

153

Chapter | 5 Continental Atlantic Rivers

TABLE 5.1 General characterization of the Continental Atlantic Rivers

Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25%) ecological regions Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparce vegetation Wetland Freshwater bodies Protected area (% of catchment) Water stress (1–3) 1995 2070 Fragmentation (1–3) Number of large dams (>15 m)a Number of large dams (>15 m) (basin) Native fish species Non-native fish species Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person)

Meuse

Loire

Garonne

Dordogne

Adour

Charente

215 34 548 10 89.3 9.3 2 6; 70

286 1 17 054 27 76.5 10.5 3 6; 70

478 56 232 20 84.1 11.3 4 6; 70

359 23 869 14 85.8 11.1 2 6; 70

415 16 927 5 97.8 11.7 3 6

102 9512 n.d. 80.0 12.0 2 6

11.4 38.7 18.1 28.7 1.7 0.1 0.4 0.9 0.2

3.4 44.6 28.5 21.2 1.6 0.0 0.1 0.6 1.5

2.0 34.4 19.4 39.1 4.3 0.0 0.1 0.7 3.5

2.6 46.6 12.2 28.6 7.9 1.6 0.0 0.5 0.2

2.8 39.5 9.2 33.3 10.8 4.0 0.1 0.3 13.3

3.5 68.6 9.4 18.0 0.4 0.0 0.0 0.1 0.1

2.9 2.9 2 0 10 36 16 8 255 23 345

1.1 1.1 2 1 36 26 31 5 67.6 22 196

1.1 1.1 3 5 39 27 17 2 72.6 21 952

1.0 1.0 3 9 14 27 17 0 43.3 21 722

1.2 1.2 2 1 13 26 17 2 68.7 22 468

1 1 n.d. n.d. n.d. n.d. n.d. 0 57 20 788

n.d. No data. a Large dams along the main stem. For data sources and detailed explanation see Chapter 1.

features. They also have their source at relatively high elevation: the R. Loire, with its important tributary Allier, rises in the Massif Central, while the Rivers Garonne and Adour flow from the Pyrenees in the South–West of France. This has important implications on hydrology, but also on the diversity of habitats, generally associated with increased biodiversity, as they vary along the longitudinal gradient. However, even though the R. Loire, for instance, may seem ‘wild’ at first sight, its middle and lower course have been affected by anthropogenic impacts for centuries, related to commerce, industry, agriculture, and wastewater discharge from small and large cities. Therefore, similar water quality problems have affected rivers as different as the Meuse, the Charente and the Loire, which have been submitted to rather intense eutrophication, translating into phytoplankton blooms, which may develop where and when river morphology, meteorological and hydrological conditions enable development of suspended microorganisms. Moreover, reservoirs, hydroelectric dams, and diverse hydraulic works, which may further favour eutrophication effects, are widespread in the Loire and Adour–Garonne basins. In the R. Garonne, however, a relatively shallow channel, swift current and short water retention time do not allow development

of plankton, but of periphyton, which are the main primary producers in this river, while planktonic production takes place mainly in reservoirs. Even though some Atlantic rivers retain significant fish populations in transition waters, as well as of various amphihaline species, obstacles to fish circulation are also a common characteristic of the three basins, and have been a major cause of reduction in migratory fish species and stocks. By contrast, increased connectivity between basins due to navigation channels has probably been a key factor for the spreading of several exotic plants, invertebrate and vertebrate species. In these basins, water managers have to deal with potentially conflicting issues, such as control of nutrients and toxicants inputs, monitoring of water quality, study and management of natural and exotic fauna and flora, maintenance of ecosystem function, the need to meet the water demand from agriculture, industry and household, management of extreme flows. Nevertheless, with increased public awareness of the need for integrated water resource management, the prospects for river restoration are good, even though great efforts remain to be done in different domains. This chapter on Atlantic rivers essentially addresses these issues, and emphasizes in particular the biodiversity aspects.

Chapter 5.1

The Meuse River Basin Jean-Pierre Descy

Gis ele Verniers

Laurent Viroux

Research Unit in Organismal Biology (URBO), University of Namur, Rue de Bruxelles 61, B-5000 Namur, Belgium

Research Unit in Organismal Biology (URBO), University of Namur, Rue de Bruxelles 61, B-5000 Namur, Belgium

Research Unit in Organismal Biology (URBO), University of Namur, Rue de Bruxelles 61, B-5000 Namur, Belgium

Patrick Kestemont

Philippe Usseglio-Polatera

Jean-Nicolas Beisel

Research Unit in Organismal Biology (URBO), University of Namur, Rue de Bruxelles 61, B-5000 Namur, Belgium

Laboratory “Ecotoxicity-BiodiversityEcosystem Interactions” (LIEBE), University Paul Verlaine, IIe du Saulcy, BP 80794, 57012 Metz, France

Laboratory “Ecotoxicity-BiodiversityEcosystem Interactions” (LIEBE), University Paul Verlaine, IIe du Saulcy, BP 80794, 57012 Metz, France

Etienne Everbecq

rard Pierre Ge

Joseph Smitz

Aquap^ ole, University of Li ege, Sart Tilman B53, B-4000 Li ege, Belgium

Research Center for Nature, Forest and Wood (CRNFB), Minist ere de la R egion Wallonne, Avenue Mar echal Juin, 23, B5030 Gembloux, Belgium

Aquap^ ole, University of Li ege, Sart Tilman B53, B-4000 Li ege, Belgium

The Meuse is an international river that has been used by man for centuries, and it is still the main source of drinking water for large cities in Belgium and The Netherlands. In fact, water quantity and quality have been a major issue between the various riparian countries and political regions. Many kinds of data have been generated in the past decades on various aspects of the river: (a) hydrology, for the need of predicting and controlling floods; (b) water chemistry, in the context of water pollution assessment and control; and (c) biology and ecology, for water quality assessment and studies on aquatic biodiversity, community dynamics, and ecosystem function. The synthesis of these data has been facilitated by the research undertaken by the countries and regions involved in the International Meuse Commission, which produced the numerous reports used for writing this section.

5.1.1. INTRODUCTION In contrast with the other rivers of this chapter, and despite its relatively short length (905 km), the Meuse is a transboundary river that flows through several countries and regions, mainly France, Wallonia, Flanders, and The Netherlands. The total catchment area is 34 548 km2, with nearly 9 million inhabitants. This fact already suggests that the river experiences impacts from human activities and that water and river management are key issues that must be dealt with Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

at international levels. To achieve the necessary coordination, an international commission for the protection of the river (ICPM, International Commission for the Protection of the Meuse) was created in 1995, and redefined in 2000 as the International Commission for the Meuse (ICM) in the context of the implementation of the EC Water Framework Directive (WFD). These international agreements created the International River Basin District (IRBD) of the Meuse (Table 5.2). A particular feature of the hydrography of the Meuse watershed is that all major tributaries (Semois, Lesse, Sambre, Ourthe) are located mostly in the Walloon Region, so that nearly 36% of the watershed is in this region (Figure 5.1b). The French watershed is comparatively smaller (ca. 26%), although it contains more than half of the entire main river. Besides landscape and ecosystem values, the Meuse fulfils diverse functions and undergoes several kinds of pressures. Its surface waters are treated for the drinking water supply for around 6 million people, mainly in large cities (e.g. Brussels, Antwerp and Rotterdam). The river is regulated by weirs and navigation dams that allow navigation between the ports of Rotterdam and Antwerp (through the ‘Canal Albert’) and the industrial centres of Wallonia and the southern Netherlands. It provides cooling water for industries and powerplants (including two nuclear powerplants) and receives thermal discharges. Production of hydroelectricity is carried out by turbines at most dams. In addition, a major part of the land in the watershed is used intensively for 154

Chapter | 5.1 The Meuse River Basin

TABLE 5.2 Surface area and number of inhabitants for each state or region of the International River Basin District Meuse

France Luxemburg Belgium (Walloon Region) Belgium (Flemish Region) The Netherlands Germany Total

Area (km2)

Number of inhabitants (1000)

8919 65 12 300 1596 7700 3968 34 548

671 43 2189 411 3500 1994 6814 (1000)

agriculture, which implies problems of erosion and diffuse inputs of fertilisers and pesticides to surface and ground waters. These pressures on the river and its water quality, however, do not limit various recreational activities such as angling and boating in some sections.

5.1.2. HISTORICAL PERSPECTIVE The progressive changes that profoundly affected river morphology and hydraulics began some 200 years ago when the first large-scale works for improving navigation on the river were undertaken. Micha and Borlee (1989) provide a detailed account of the history of the canalization of the Belgian stretch of the Meuse, which occurred in various steps throughout the 19th century. At the same time, encroachment of the floodplain by construction of roads and railways, and by human occupation in towns and villages along the river, also occurred (Photos 5.1 and 5.2). Further regulation hap-

155

pened as industries were developed in the beginning of the 20th century, and a major phase of riverbed alteration followed the 1926 catastrophic flood via the construction of new roads and railways, and increased human occupation along the river. Since then, the navigable channel has been deepened to further improve navigation and lower risks from flooding. Today, only a few patchy macrophyte stands exist along the Belgian stretch of the river (Descy 1987a, 1987b). Among the consequences of this intense regulation and land use change, the suspended load dramatically increased for river discharges over 100 m3/s, and regular dredging to remove sediment deposits from the channel became necessary. Throughout the 20th century, the flow downstream of Liege declined significantly because of water abstraction and exploitation of groundwater. The French stretch of the river was less affected by regulation, and several parts of the river have retained their ecological function and biological potential (Grevilliot et al. 1998). The most natural reach lies in the middle of the French stretch (Photo 5.3) where the channel was not regulated and periodically inundated grassland still exists. In The Netherlands, the physical situation of the Meuse is comparable to that in Belgium, having patchy sites with more natural ecological and biological characteristics, here, the wide river valley offers greater potential for restoration, with important projects aimed at reconciling the conflicting objectives of navigation, flood control and sustainable ecological function. These projects focus on restoring habitat diversity and floodplain structure where possible. The ecological status of Meuse tributaries varies by country and region. For instance, most tributaries (ca. 85%) in the French and Belgian part of the basin have a natural morphology and hydrological functioning, with the exception of a few large dams and local structural changes for flood control. PHOTO 5.1 The Meuse River at Namur, in Belgium, at the confluence with the R. Sambre (rkm 530) (Photo: ÓMRW-DIRCOM – Jean Louis Carpentier).

156

PART | I Rivers of Europe

PHOTO 5.2 The Meuse River at Monsin, downstream of Liege, upstream of the border Belgium – Netherlands (rkm 600) (Photo ÓMRW-DIRCOM – Jean Louis Carpentier).

Relatively few reservoirs were built in the Meuse River basin: most are located in the Walloon Region and used for drinking water supply, flow regulation, electricity production and recreation. Canals and highly modified tributaries are found in Flanders and The Netherlands. Overall, 62% of the rivers and 12% of the 150 lakes in the Meuse basin can be considered more or less natural.

5.1.3. BIOGEOGRAPHIC SETTING Symoens (1957) summarized the biogeographic features of the region. The basin is found in the Baltico–Rhenan sector of the Medio-European domain and has a mostly continental

climate. Local contrasts occur in the Ardennes highlands with cold winters and in the Lorraine region with hot summers. The influence of the Atlantic domain in the west also is relatively strong and attenuates thermal variations. Precipitation can be locally high, allowing the development of typical Atlantic plant associations. Seven different ecoregions occur in the basin (ICM 2005): (1) calcareous regions of tertiary calcareous formations of Trias and Jura in Lorraine and the Eiffel, (2) Famenne of Devonian slate plateau formation adjacent to the Ardennes mountainous region, with fast-flowing calcareous rivers, (3) siliceous mountainous bedrock formations of the Ardennes and the Eiffel, (4) hilly regions of Condroz with low areas of chalky massifs and river moraines and terraces with mixed sediments and PHOTO 5.3 The Meuse River at Bannoncourt, in France (River rkm 194.5) (Photo: G. Thiebaut).

157

Chapter | 5.1 The Meuse River Basin

rivers with intermediate flow velocities, somewhat alkaline and high sediment loads, (5) eolic loam region of quaternary loamy plateaus with incised watercourses with fine sediments and high alkalinity, (6) sandy areas in the Campine region having Miocene sands and quaternary lowland regions with streams having sandy riverbeds, and (7) organic peat and clay valleys and moorlands that are drained by small watercourses with high dissolved organic matter.

5.1.4. PHYSIOGRAPHY AND CLIMATE The Meuse basin has three major geomorphological areas that correspond to the Upper, Middle and Lower Meuse. The Upper Meuse stretches from the source on the Langres Plateau to immediately downstream of Charleville–Mezieres in France. The Middle Meuse starts downstream of Charleville–Mezieres and ends after Liege in Belgium. It covers a large part of the Ardennes Plateau and Walloon part of the basin. The Lower Meuse begins at Liege and ends in the deltaic region of The Netherlands where the Meuse flows into the North Sea. This section covers the German, Flemish and The Netherlands parts of the basin. The main river flows over calcareous rocks in the upper basin, which strongly influences its chemistry. The main river has been divided into 10 water bodies in which the three upstream ones are in the Western Highlands and the remaining ones are in the Western Plains (Table 5.3). The climate of the basin is a temperate oceanic type, although a continental influence often causes hot dry summers and cold dry winters. An oceanic regime dominates most of the time, resulting in humid weather in all seasons. The average annual rainfall is 700–1400 mm, with the highest amount in the high Ardennes. Despite large interannual variation, long-term changes in rainfall have occurred that are associated with climate. For instance, there has been an increase in maximal winter rainfall since the early 1980s, parallel to an increase in maximal winter discharge (Tu et al. 2005).

5.1.5. HYDROLOGY AND BIOGEOCHEMISTRY The Meuse is a rain-fed river with considerable fluctuations between seasons and years. Major areas of the watershed are hilly with an impermeable sub-soil. In these areas, surface run-off is common, often resulting in flash floods in tributaries and the main river. Low water retention in the middle basin causes low flows during dry periods. High flows generally occur in winter and spring. Variations in flow can be abrupt, resulting in floods that last from a few days to several weeks. This was the case, for example, in 1993 when a maximum flow of 3100 m3/s was measured in Eijsden between Wallonia and The Netherlands. Summer and autumn are mainly characterized by long periods of low flow that

range from 10 to 40 m3/s in Eijsden. Long-term records (since 1970) of discharge at three sites on the river show a trend in increasing mean annual flow over the last three decades (Figure 5.2). Long-term water temperature data shows that mean annual temperature has increased 0.16–0.89 C over the past three decades (Figure 5.3). A similar trend is observed for annual temperature minima and maxima. The Meuse is an alkaline river, dominated by calcium and bicarbonate ions, with high conductivity (400–600 mS/cm) and a pH between 7.5 and 8.0. Conductivity is highest in the upper river (up to 900 mS/cm) (ICM 2005), quickly decreasing downstream and remaining constant to the delta, where saline intrusions occur. A detailed characterization of the geochemical properties of the river and tributaries can be found in Descy and Empain (1984). They describe five water types, ranging from acid streams with low conductivity (<50 mS/cm) to alkaline calcareous streams with conductivities reaching 600 mS/cm. Suspended sediments are relatively low in the Meuse, typically ranging between 10 and 15 mg/L. Longitudinally, highest concentrations are in the middle reach, possibly due to sediment resuspension by boats. Long-term records indicate an increase in suspended sediments during the 1980s with a subsequent decline since then (Figure 5.4). The increase in the 1980s was associated with the changes in flow at that time.

5.1.5.1. Pollution in the River The level of wastewater treatment varies among the different parts of the basin, and most of these are for treating domestic sewage. Some untreated wastes do enter the river and the effects are evident in some areas, such as between Liege and Eijsden. In this section, dissolved oxygen minima <4 mg/L (60% saturation) are lower than elsewhere along the Meuse. High phytoplankton biomass also adds significant amounts of organic matter to the system that is eventually biodegraded. Inputs of nitrogen and phosphorus are high in the middle Meuse (Figure 5.5), causing high standing stocks of algae. The high nitrogen loads are mainly from agriculture (69%), whereas most P inputs are from domestic wastewater with industrial sources contributing locally (ICM 2005). Chlorophyll a concentrations in the river can exceed 100 mg/L, amounting to 4 mg C/L. Several studies have examined temporal and longitudinal dynamics of algae in the river (Descy 1992; Descy et al. 1987, 1994; Reynolds & Descy 1996; Everbecq et al. 2001). They showed that where nutrient availability is in excess of algal demand, controlling factors on algae are mainly discharge, incident light, water transparency and temperature, interacting with river morphology and hydraulics. Long-term data in chlorophyll a levels show major changes in the river over the past three decades that are unrelated to changes in nutrients. This suggests that phytoplankton biomass in the river is mostly

TABLE 5.3 Typology of the River Meuse as defined by the International Meuse Commission (2005) Sub-ecoregions

Meuse sections

Ecoregion and altitude category

Global geology

River type

State/regionsa

Haute- Marne Plateau de Langres

4. French/Belgian border – Borgharen

Kempisch plateau – Limburg hill country Kempen

5. Borgharen – Maasbracht Grensmas (Border Meuse) 6. Maasbracht – Lith (Zandmaas en Bedijkte Maas) Sandmeuse and Diked 7. Lith – Waalwijk (Benedenmaas) (Lower Meuse) 8. Waalwijk – Haringvlietdam (Bergsche Maas, Biesbosch, Amer-Hollands Diep-Harlingvliet 9. Krammer Volkerak

Western plains <200 m asl Western plains <200 m asl Western plains <200 m asl Western plains <200 m asl

Siliceous

Small river on chalk and marl, with mostly calm and cold water Large River on chalk and marl, with mostly calm and temperate water Large siliceous river of the Ardennes massif, wide stream with cold and temperate water Very large river of the Condroz with small slope (canalized river). Slow flowing river on sand/clay (NL) Rapidly flowing large river on gravel

F

Condroz

Western highlands 200–800 m asl Western highlands 200–800 m asl Western highlands 200–800 m asl Western plains <200 m asl

Calcareous

Ardennes

1. Le Ch^atelet-sur-Meuse – Neufch^ateau (confluence of the Mouzon) 2. Neufch^ateau – Nouzonville (confluence of the Gutelle) 3. Nouzonville – French/Belgian border

B/VL – NL

Siliceous

Slowly flowing lower course on sand/clay

NL

Siliceous

Fresh intertidal water on sand/clay

NL

Siliceous

Fresh intertidal water on sand/clay

NL

Siliceous

Medium sized, deep buffer lake

NL

Siliceous

Transitional waters/estuary

NL

Land van Maas en Waal Biesbosch – Rhine-Meuse delta

Biesbosch – Rhine-Meuse delta Coast a

10. Haringvlietdam – 12-miles zone (Northern delta coast)

F = France, B/WL = Belgium Wallonia, B/VL = Belgium Flanders, NL = The Netherlands.

Western plains <200 m asl Western plains <200 m asl

Calcareous Siliceous Calcareous

F F B/WL – NL

159

Discharge (m3/s)

400

Eijsden

Ham-s-Meuse

Inor

300

1.90

200 1.37

100 0.53

0 1970

[m3/y]

1980

1990

Suspended matter (mg/L)

Chapter | 5.1 The Meuse River Basin

50 Eijsden Keizersveer

40 30 20 10 0 1970

2000

1980

1990

2000

FIGURE 5.2 Time series of annual mean discharge at Inor (France, upper Meuse section), Ham-sur Meuse (France, middle Meuse section), and Eijsden (The Netherlands, lower Meuse section).

FIGURE 5.4 Time series of suspended matter (annual mean) at Eijsden (lower Meuse section) and Keizersveer (about 70 km from the sea).

under physical control, possibly in relation to light limitation from the suspended sediments. For instance, recent chlorophyll a peaks, as well as maximal mean annual concentrations, correspond to a decrease in suspended sediments. The recent decline in chlorophyll a in the river may be related to the recent invasion by the filter-feeding Asian clam, Corbicula sp. Several heavy metals (Cr, Cu, Zn, Pb, Cd) have been measured in the Meuse, sometimes at significant concentrations. The contamination of bed sediments by heavy metals is a serious problem, especially between Liege and Kinrooi where the highest industrial activity is found. The level of heavy metal pollution in the river has steadily decreased in the past decades. Organic micropollutants have also been detected in the river, notably PAHs and various pesticides. Many of these pollutants are widely used herbicides (diuron, isoproturon, atrazine, simazine and their derivatives) and cause concern for drinking water supplies.

knowledge of the river and of the organisms living in it. Due to the lack of earlier surveys, it is still difficult to quantify the ecological changes that have occurred in the river as a consequence of environmental change.

Studies of the aquatic flora and fauna of the Meuse were relatively sparse before the 1970s. Then a strong interest developed for the river biota, largely triggered by the need to assess the impact of pollution, including thermal pollution and radioactive contamination from power plants, on the river. Several surveys and detailed studies of the flora and fauna have been conducted in the last decades, giving a better

Temperature (°C)

30

Maximum

20 Average

y = 0.048x − 80.6 R 2 = 0.19

Minimum

y = 0.064x − 123.3 R 2 = 0.13

10

0 1970

1980

1990

2000

FIGURE 5.3 Time series of annual temperatures (mean, maximum, minimum) at Monsin (lower Meuse section).

In the Meuse basin, benthic algae, especially diatoms, have been examined several times since the early synthesis of Symoens (1957). Because of the wide range in physical– chemical conditions of the river and its tributaries, algal assemblages are quite diverse in the less polluted streams in the catchment. Diatom assemblages were recently classified at the European scale (Gosselain et al. 2005) and at least four assemblage types of low-impacted streams were identified in the basin. In the main river, typical diatoms are Navicula tripunctata, N. menisculus, N. capitatoradiata, Gyrosigma nodiferum, Fallacia subhamulata, Amphora copulata, Encyonopsis microcephala, and Amphora ovalis. Macroscopic benthic algae comprise different taxa, some of them widespread (Cladophora glomerata, Vaucheria spp., colonial cyanobacteria) and others limited to fast-flowing reaches downstream of weirs or in fish passes (the red algae Lemanea fluviatilis, Audouinella sp. and Bangia atropurpurea). Filamentous algae often have epiphytic diatoms such as Cocconeis spp., Rhoicosphenia abbreviata and Gomphonema spp. Descy and Ector (1999) provided a water quality profile of the entire river, based on diatoms.

Orthophosphate (mg P/L)

5.1.6. AQUATIC BIODIVERSITY

5.1.6.1. Algae

0.8 Eijsden Keizersveer Inor

0.6 0.4 0.2 0.0 1970

1980

1990

2000

FIGURE 5.5 Time series of orthophosphate concentrations at three stations along the Meuse.

160

Diatoms are a dominant component of the phytoplankton in the river, and centric species are most common. Rojo et al. (1994) and Reynolds and Descy (1996) gave lists of potamoplankton taxa commonly found in the river. Green algae belonging mainly to Chlorococcales are often an important group in the phytoplankton (Descy, 1987a, 1987b). Excluding tychoplanktonic forms (i.e. taxa of benthic origin that have detached and remain in suspension), about 150 taxa are common in the river (Descy 1987a, 1987b; Descy & Gosselain 1994; Gosselain 1998). Green algae represent more than 51% of these taxa, while diatoms contribute 28%. Other planktonic algae are most often secondary, although chrysophytes, cryptophytes, cyanobacteria, dinoflagellates and euglenophytes can reach high levels locally or during particular periods. Diatoms common in eutrophic stretches typically have large populations all year round or in some seasons, and include Stephanodiscus hantzschii, S. minutulus, S. invisitatus, Cyclotella meneghiniana, C. pseudostelligera, C. atomus, Cyclostephanos dubius, Aulacoseira granulata, and A. ambigua. Seasonal variation in discharge with high flows in winter and spring and low flows in summer causes temporal variation in phytoplankton abundance. There is a typical spring bloom largely dominated by small Stephanodiscus, followed in summer by other diatom taxa and Chlorococcales. Less light and lower temperatures in autumn favour small Stephanodiscus again until rainfall caused increases in discharge suppress phytoplankton development. Seasonal variation in phytoplankton biomass and composition were simulated with a non-stationary simulation model (Everbecq et al. 2001), which has also been used for testing the impact of benthic filter-feeders (Descy et al. 2003) and powerplants on phytoplankton assemblages in the river. Longitudinally, an increase and then decrease in phytoplankton abundance occurs along the river. After an upper stretch almost devoid of phytoplankton, algal growth occurs in the main river in the French sector with maximal biomass being reached after Rkm 400 where the river enters Belgium. Downstream, as the river deepens and receives large tributaries, a progressive decline in phytoplankton biomass occurs. Simulations showed a species change also takes place along the river, as physical conditions, including river morphology and water transparency, change downstream (Everbecq et al. 2001). Depending largely on hydrology, maximum phytoplankton biomass is attained further upstream or downstream, but is most pronounced in the upper river in Belgium.

5.1.6.2. Aquatic Plants In France, the Meuse has retained most of its natural features, and has a diverse vegetation of helophytes and hydrophytes. Various reed stands, typically rushes (Scirpus lacustris), are well developed in the French sector. Meadows and grasslands are found in the floodplain (Duvigneaud & SaintenoySimon 1995). Yellow water-lilies (Nuphar lutea) colonise

PART | I Rivers of Europe

stagnant waters and slow-flowing reaches, whereas Ranunculus fluitans and Myriophyllum spicatum develop in fastflowing reaches. The riparian zone is occupied in several areas by the cut-grass Leersia oryzoides, sedges (Carex acuta) and great-water dock (Rumex hydrolapathum). A variety of helophytes develop in the shallow littoral, including Acorus calamus, Butomus umbellatus, Sagittaria sagittifolia, and Iris pseudacorus (Duvigneaud & Saintenoy-Simon 1995). The common reed, Phragmites australis, also colonises the littoral zone, whereas Glyceria maxima occupies only relatively small areas. The canary-grass, Phalaris arundinacea, is common on open gravels, along with many wetland species such as Thalictrum flavum, Calystegia sepium, Lycopus europaeus, Lythrum salicaria, Eupatorium cannabinum, Lysimachia vulgaris, Stachys palustris, and Achillea ptarmica. The situation is different in the Walloon sector, where 11 riparian types are found in the upper part of the sector (GIREA 2004). These vegetation types include hydrophilic species typical of damp meadows, such as meadow-sweet (Filipendula ulmaria), hemp agrimony (E. cannabinum), great hairy willow herb (Epilobium hirsutum), purple loosestrife (L. salicaria), wild angelica (Angelica sylvestris), water betony (Scrophularia auriculata), valerian (Valeriana repens), and yellow loosestrife (L. vulgaris). Some reed stands have persisted here, including species such as P. australis, Typha latifolia, P. arundinacea, I. pseudacorus, G. maxima, Mentha aquatica, Juncus effusus, R. hydrolapathum, Myosotis scorpioides, and Carex acutiformis. Further downstream, most hydrophytes have completely disappeared in the Walloon Meuse (GIREA 1996). Several species of aquatic and semi-aquatic mosses have been recorded in the main river channel, where most species grow essentially in fast-flowing reaches downstream of weirs and in fish ladders (Empain 1977). Common plants in these habitats are Cinclidotus nigricans and C. danubicus, commonly known for relatively large, alkaline rivers. Other species, inhabiting slower current areas are the common river mosses Platyhypnidium riparioides and Fontinalis antipyretica. Several factors, including hydraulic works, eutrophication, and increased flow variation, have contributed to the loss or decline of aquatic vegetation in the Meuse downstream of the French-Belgian border. The aquatic vegetation in the French sector is quite abundant and diverse, and contrasts strikingly with that of the Belgian Meuse. The French Meuse has retained its habitat heterogeneity, and has been little altered by the management of the riverbanks and bottom (Micha & Pilette 1988). In most reaches, the river is not used for navigation, which takes place in adjacent canals. In the Belgian sector, the reduction of shallow, slow-flowing zones, as a result of deepening and widening the navigation channel, limits plant colonization. Most banks also have been stabilized, further constraining plant development. The decrease in water transparency from eutrophication and excess algal growth suppresses the growth of submerged

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Chapter | 5.1 The Meuse River Basin

macrophytes. Lastly, sediment resuspension by boat traffic and flow variation limits macrophyte development in the littoral zone.

5.1.6.3. Zooplankton Plankton in the Meuse comprises representatives from the three major groups found in freshwater environments, euplankton, phytoplankton, and zooplankton, with flow regime playing a pivotal role. Short residence time of water favours small, prolific organisms like rotifers that numerically dominate the few euplanktonic species found in the river. Five species, all from Brachionidae, make up the bulk of this assemblage: Brachionus calyciflorus, B. angularis B. urceolaris, Keratella cochlearis and K. quadrata. The Synchaetidae are also well represented, containing several species from the genera Synchaeta and Polyarthra. This community comprises a combination of opportunistic, largely algivorous/omnivorous filter-feeders (e.g. various Brachionus), detritivores (Keratella), and more selective, ‘raptorial’ feeders (Synchaeta, Polyarthra). Some bacterivorous species (Anuraeopsis fissa, Filinia) are also found at low densities and the large predator Asplanchna is commonly recorded. A total of 44 taxa have been listed for the river. Following a spring peak, population density usually decreases in June and increases again in late summer. Species diversity is maximal in spring and slowly decreases during the year. Longitudinally, plankton abundances are maximal downstream. Densities are usually <500 ind./L, but can reach peaks above 4000 ind./L (Viroux 2000). Cladocerans found in the river are mostly euplanktonic species. Small Bosmina are the most abundant, especially downstream where they can reach up to 50 ind./L. Larger species like Moina, Ceriodaphnia, Diaphanosoma, and even Daphnia cucullata are less common. These taxa typically peak in late summer when flow conditions are most favourable (Viroux 2002). The less abundant families Chydoridae and Macrothricidae are also found in samples. Copepod dynamics resemble those of cladocerans, with maximal population density (up to 60 ind./L) in late summer. Taxa are represented by planktonic and benthic species. Cyclopoids are found only in the river in Belgium, and calanoids have been observed in The Netherlands. Zooplankton can exert a significant grazing pressure on algae, and account for a substantial part of phytoplankton losses when rotifers and small cladocerans are abundant (Gosselain et al. 1998; Viroux 2000). A comparative survey of autotrophic and heterotrophic plankton was carried out in the upper part of the Belgian Meuse in 2001. This stretch of river was shown to be autotrophic in previous studies (Descy et al. 1994; Servais et al. 2000). Biomass estimates showed that phytoplankton dominated potamoplankton biomass (1–4 mg C/L) during the growing season (Servais et al. 2000; Joaquim-Justo et al.

2006). Heterotrophic bacteria were also important, with biomass at 0.1–0.3 mg C/L). Other plankton (rotifers, heterotrophic nanoflagellates and ciliates) had a combined biomass <0.1 mg C/L.

5.1.6.4. Benthic Invertebrates Data on bottom-dwelling microinvertebrates, a largely neglected component of aquatic food webs, are available for the Meuse (Capieaux 2004). Benthic cladocerans are common in plankton samples, with 10 species of Chydoridae and one of Macrothricidae (Macrothrix hirsuticornis) being identified from sediment samples. Their presence in the plankton is associated with increases in discharge (Viroux 2002) and, except for Chydorus sphaericus, their capacity to survive in the plankton is doubtful. Much data exist on macroinvertebrates in the Meuse basin (see Stroot 1989), but for the main river, the data are mostly restricted to some river stretches (see Usseglio-Polatera & Beisel 2003). A monitoring framework for bioassessment of the river was applied between 1998 and 2001 at 16 sites, ranging from the most upstream sites in France to downstream sections in The Netherlands. Insects dominated the French sites in taxonomic richness as well as abundance, and were progressively replaced by crustaceans downriver, especially in the Walloon sector and The Netherlands. Oligochaetes, achaetes, polychaetes, turbellarians, gastropods and bivalves were abundant in the Walloon and The Netherlands sites. French stations had many taxa with preferences for fastflowing reaches such as stoneflies (Leuctra sp., Euleuctra geniculata), caddisflies (Rhyacophila sp., Hyporhyacophila sp., Brachycentrus subnubilus, Psychomyia pusilla, Lepidostoma hirtum, Cheumatopsyche lepida), mayflies (Habrophlebia sp., Ephemera spp., Heptagenia sp., Ephemerella ignita), coleopterans (Limnius sp., Macronychus sp., Esolus sp., Stenelmis sp.) and dipterans (Simuliidae). Some slowflowing reaches had several species of dragonflies. Further downstream, modifications of the river channel for navigation results in major disturbance of the benthic invertebrates, with the loss of many insects and a decrease in biodiversity. Water pollution by industrial and domestic sewage, which occurs downstream in the Belgian Meuse, further degrades the benthic community. Some habitat improvement occurs around the Belgian–Dutch border and in the ‘Border Meuse’, evidenced by the recovery of aquatic insects such as caddisflies. Several exotic species considered as recent invaders increase in numbers downstream, and include Jaera istri, Atyaephyra desmarestii, Dikerogammarus villosus, Chelicorophium curvispinum, Hemimysis anomala, Limnomysis benedeni, Orchestia cavimana (crustaceans), Musculium lacustre, Corbicula fluminea (Bivalvia) and Hypania invalida (Polychaeta). They contribute up to 60% of the total abundance at some sites.

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PART | I Rivers of Europe

5.1.6.5. Fish

5.1.6.5.2 Introduced and Invasive Species

The fish fauna comprises 52 species of which 36 are native. Several migratory fishes have disappeared, while exotic fishes represent up to 50% of the assemblage in some parts of the main river (Kestemont et al. 2002). Water pollution and habitat alteration are the major causes for the low fish diversity in the river. Rheophilic species have relatively high populations in the French Meuse and in the unregulated Border Meuse, whereas limnophilic species are well represented in all sectors.

The number of exotic species is relatively high in the Meuse. Most of these exotics have been voluntarily or accidentally introduced for various reasons (recreational fisheries, restocking, aquaculture), whereas others have migrated from other European river basins through various interbasin canals. An improvement in water quality in the lower river has benefited the movement of some fish as well, such as the recent presence of the asp Aspius aspius since 2000. The origin of exotic fishes is mainly from central Europe (e.g. Danube basin), although species from North America and Asia have also been introduced. Some tropical fishes such as tilapia Oreochromis aureus and O. niloticus, African catfish Clarias gariepinus and pacu Colossoma macropomum are found in some limited areas, usually near the heated effluent waters of nuclear powerplants; their survival during winter is doubtful. Despite the large number of exotic fishes, no species is considered as invasive in the Meuse. Several species have reproducing populations, including the common carp, zander, goldfish, channel catfish and pumpkinseed. Other stocked fish such as rainbow trout, brook trout, common whitefish, and peled were introduced many decades ago in streams and reservoirs, but they do not have reproducing populations. The Danube bleak and stone moroko were probably introduced accidentally through the restocking of the Belgian Meuse with various cyprinids (mainly roach) from central Europe. They have been recorded recently, but their abundances are low and, up to now, do not show potential for invasion. The status of European wells catfish is unclear. Paleontological data reveal the presence of wells among the ichthyofauna of the Meuse, but the species probably disappeared during the last glaciation. Some fossils have been recently discovered in archaeological sites of the Roman and Middle-Age periods, but the origin of this fish is still a matter of debate. Its recent expansion in the lower Meuse is probably due to escapees from fish farms.

5.1.6.5.1 Migratory Fish and the Reintroduction of the Atlantic Salmon Migratory fishes have attracted the attention of both authorities and scientists, notably because of a BENELUX decision which aims at ensuring free movement of fish in rivers. In the Meuse, large migratory species such as Atlantic salmon and sea trout are of special emphasis. These are anadromous fish that reproduce in freshwater and mature in the sea. Although not documented, many rivers in the Meuse network were inhabited by salmon in the 1800s. Due to canalization, weirs, locks, and lack of connection with the sea, the Atlantic salmon had disappeared from the Meuse basin around 1935. The situation is less critical for sea trout, as they occur in the basin and may be 10 times more abundant than the salmon. The main management actions at the international level consist of identifying the main obstacles to fish migration. Several programs also have been conducted for reintroducing the Atlantic salmon in the Meuse (‘Meuse saumon 2000’ in the Walloon Region and ‘Zalm terug in onze rivieren’ in The Netherlands). The presence of adequate breeding sites for adults and nursing areas for juvenile salmon are important for sustaining salmon populations. As such, several restoration measures for salmon were taken in the past 20 years in different areas of the river. These measures also improved habitat conditions for resident trout. Regardless, these restored sites may still be inaccessible to salmon and sea trout because of physical barriers from dams, dykes and powerplants. These barriers also hamper downstream migration of juveniles and can result in high mortality rates during passage through powerplant turbines. Fish passes are notably the most common management measure undertaken at dams, and are used by other species besides salmon and sea trout. In the Walloon Region, stocking young fish (eggs, larvae, juveniles) from non-native strains to sustain populations has been common since 1980. These stocks are from adults originating from rivers that flow into the Atlantic Ocean or North Sea, and exclude rivers flowing into the Baltic Sea. Since 1999, some adult salmon caught in the lower Dutch Meuse have been used for stocking purposes. Since 2002, adult salmon have been recorded in the Lixhe fish ladder, some 300 km from the sea, giving some hope that the restoration of salmon and sea trout is possible.

5.1.6.5.3 Endangered Fishes Seven fishes of the Meuse are extinct, including Atlantic salmon, Allis shad, Twaite shad, European sturgeon, houting, sea lamprey and river lamprey. Flounder, burbot and spiny loach are probably extinct in most parts of the Meuse basin since they have not been captured in the last decade. Some of these species are present, although rare, in the Dutch part of the Meuse. Causes of extinction or endangerment include the building of weirs for navigation (reducing fish migration), industrial and, to a lesser extent, domestic pollution, commercial overfishing, and the destruction of spawning and nursery habitats. Only a few species are considered endangered, such as the eel, and many species are classified as vulnerable, including the European brook lamprey, bullhead, and several salmonids and cyprinids.

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Chapter | 5.1 The Meuse River Basin

5.1.7. MANAGEMENT AND WATER USE The major economic use of the Meuse is for drinking water supply. Both surface and ground waters are used because almost the entire population of the basin is connected to a public water supply. The total amount of water abstracted for drinking water equals 964 million cubic meters per year, of which 64% is extracted from groundwater. In the Dutch, German, and Walloon areas, between 30 and 46% of the drinking water comes from surface waters. Although groundwater is the major source of drinking water throughout the Meuse basin, relatively few underground water bodies (10%) are considered at risk of not achieving good status in 2015. Water abstraction for agriculture is relatively low in the basin, although industry usage, cooling water for powerplants in particular, can be locally important. Most powerplants are upstream of the French-Belgian border (Chooz powerplant) and downstream in Belgium (Tihange powerplant). Commercial navigation is important on the Belgian Meuse. Most boat traffic takes place to and from the Albert Canal, with a total transport of 30 000– 35 000 tons/year. Between 8000 and 12 000 tons/year are transported in the sector between Liege and the tributary Sambre. Small hydropower plants are installed on most navigation dams, and flood control has always been a major issue in the basin.

5.1.8. CONSERVATION AND RESTORATION Many restoration measures have been conducted on the river in the French sector. From 1994 to 1997, measures for restoring ecologically important wetlands were carried out, including environmentally friendly agricultural practices. The objective of these operations was to preserve the status of key sites for maintaining hydrological functions that took into account groundwater recharge, self-purification processes, and flood management. These actions have also helped protect the habitat of wetland plants and birds such as the curlew (Numenius arquata), crane (Grus grus) and corncrake (Crex crex). Several restoration projects have been initiated to restore the natural course of the river by connecting side arms (some 20 between 1994 and 1999) and replanting riparian vegetation along the fluvial corridor. In Wallonia, where hydrologic management has been more extensive, fewer opportunities are available for ecological restoration. Some projects are underway that include the connection of the main channel with side arms to improve habitat for fishes. Islands, which often retain some natural features, have been classified as natural reserves and thereby protect the habitat for flora and fauna, most notably bird nesting sites for kingfisher and the great crested grebe. Various projects are now under way for restoring reed stands by replanting semi-aquatic plants in shallow areas. The most successful plants are I. pseudacorus, A. calamus, Glyceria fluitans, P. australis, and C. acuta, while others such as S.

lacustris and Typha latifolia are more sensitive to wave action. Recently, some riparian zones have been designated as Natura 2000 sites. In the Flemish stretch of the river, the ‘Border Meuse’, an important international restoration project is taking place in collaboration with The Netherlands. The project ‘Levende Grensmaas’ consists of allowing more space for the river by lowering the riverbanks. Acquisition of land along the river allowed the integration of flood protection measures and ecological restoration of the river. In The Netherlands, a similar approach was adopted in the project ‘De Maaswerken’, which includes extending the river channel by widening and deepening. Other conservation actions are the improvement or construction of fish passes, integration of the river as a core zone in primary ecological structure (‘Ecologische Hoofdstructuur’), restoration of the riparian zone (project ‘Natuurvriendelijke Oevers Maas’), and cleanup of the sediments in the lower Meuse.

5.1.9. PROTECTED AREAS International collaboration is needed for the best conservation of riverine species and habitats in the main river and tributaries (e.g. Semois, ‘Border’ Meuse, Rur, Schwalm and Niers), and for border zones that are often surrounded by large natural areas (Gaume, Hautes Fagnes, Maasduinen). In France, large stretches of the alluvial plain of the Meuse are included in the network of protected areas, that is the French Meuse and Vosges. Protected areas are also found along the tributaries Mouzon and Chiers. Large wetlands, lakes and swamps (e.g. Pagny-s-Meuse) are found in Lorraine. In March 2000, Wallonia designated 165 sites (ca. 21 000 ha) as protected areas that include several tributaries and large moorlands (e.g. Hautes Fagnes). In Flanders, eight ‘habitat’ areas are within the Meuse basin, mainly in tributary valleys and also along the floodplain of the Meuse. In The Netherlands, 16 of 79 protected areas under the ‘birds’ directive are in the Meuse basin and many are connected to the main river. Here, 39 of 141 ‘habitat’ areas also are in the Meuse basin. Seven large protected zones are both ‘bird’ and ‘habitat’ protection areas, including the Biesbosch, Groote Peel, Krammer–Volkerak, Meinweg, Haringvliet, Voordelta and Maasduinen. Lastly, there are 52 ‘habitat’ areas in the German river basin, of which the largest are the ‘Kermeter’ on the Rur, the ‘Krickenbecker lakes’ on the Nette and the ‘L€usekampniederung’ on the Schwalm. Further, the ‘MeuseNette-Platte’ region that includes the Grenzwald and Meinweg is of considerable importance at the international level.

5.1.10. ECOSYSTEM FUNCTION In the history of biological and ecological studies conducted on the Meuse, few have contributed more than those aimed at assessing and understanding the ecological

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impact of nuclear powerplants. Indeed, a first step towards understanding the ecosystem function of the river was the development of an ecological model simulating river temperature, discharge and dissolved oxygen as influenced by powerplants (Descy 1987a, 1987b). This ‘Meuse’ model highlighted the key role of biomass and metabolism of microorganisms (phytoplankton and bacterioplankton) for determining the water quality of the river, and the interaction between ‘planktonic eutrophication’ (i.e. excess phytoplankton biomass) and the functioning of powerplants. Later developments aimed at developing an integrated model for use in water quality management at the watershed scale (Smitz et al. 1997) and implementing the Meuse model for understanding ecological processes such as phytoplankton dynamics and production, grazing by zooplankton, and the impact of invasive filter-feeders (Descy et al. 1987, 2003; Everbecq et al. 2001). Other substantial contributions to the study of ecological processes in the Meuse were on bacterioplankton dynamics (Servais 1989a, 1989b; Servais & Billen 1989), trophic relationships among planktonic microorganisms (Gosselain et al. 1998; Servais et al. 2000; Joaquim-Justo et al. 2006), and phytoplankton and zooplankton dynamics (De Ruyter van Steveninck et al. 1990; Gosselain et al. 1994, 1998; Tubbing et al. 1995; Viroux 1997, 2000, 2002). Most knowledge gained on the ecological processes in the Meuse was from the POTAMON model (Everbecq et al. 2001). POTAMON is a unidimensional, non-stationary model, designed for simulating potamoplankton from headwaters to the mouth. The forcing variables are discharge, river morphology, water temperature, available light, and nutrient inputs. Given the inclusion of several algal categories, POTAMON allows the simulation of algal ‘successions’ at a particular site, as well as longitudinal changes in potamoplankton composition and biomass. The algal categories differ in their physiology, loss rates, and sensitivity to grazing by zooplankton. Two zooplankton categories were considered, Brachionus-like and Keratella-like, which differ by their clearance rate, incipient limiting level, selectivity towards phytoplankton, and growth yield. The model satisfactorily simulates the onset and magnitude of the phytoplankton spring bloom, the biomass decrease in early summer, and the autumn bloom in the Belgian Meuse. It also shows the major variations of algal assemblages along the river. The model confirms that the main driving variables of potamoplankton dynamics in a eutrophic river are discharge and related variables (e.g. retention time), light, and temperature. In addition, model simulations demonstrate that the zooplankton– phytoplankton interactions may result in phytoplankton biomass fluctuations and changes in composition. POTAMON is not only useful for exploring plankton dynamics and ecological processes in a large river, but it also is a tool to test various management measures for the river.

PART | I Rivers of Europe

5.1.11. CONCLUSION AND PERSPECTIVES In many aspects, the River Meuse is a typical regulated river of western Europe. It has been regulated for navigation and flood control for about a century over a large part of its course. River management has often been done without much consideration for the environment and aquatic biota, so that plant and animal biodiversity has decreased and floodplain functions are no longer operating The river also has many pressures from anthropogenic activities that affect water quality and sediments. Although large forested areas still exist in the basin, agriculture is a major land use in the catchment. The basin has a large human population that needs drinking water and produces waste, and various industrial and power plants use the river. Eutrophication is widespread in the Meuse, and organic pollution is still high in some stretches in which wastewater treatment plants are not yet operating. Thermal pollution may affect the oxygen budget locally and micropollutants contaminate the water and sediments in several places. In the last few years, many invasive species, mostly macroinvertebrates, have entered the river and several have successfully extended their range. There are signs that global warming is affecting the temperature of the river, with unknown consequences for aquatic organisms. Implementing the Water Framework Directive on such a river, and in particular achieving the objective of ‘good status’ or ‘good potential’ is not a simple task and necessarily involves coordination at an international level. This is the commitment of the ICM, which has identified several key issues and pressures to be addressed: - hydromorphologic alterations of the main river and of some tributaries; their impact is mainly local but they can affect biological and ecological processes over long stretches (for instance, navigation dams without fish passes affect migratory fish in the whole basin); - the inputs of organic matter and nutrients (from point and non-point sources) resulting from all human activities; these ‘classic’ pollutions affect the biocenosis of the river and the North Sea, and also water usage; - heavy metals and organic micropollutants, which also affect water and sediment quality, are harmful to the biocenosis and reduce water usage, particularly drinking water supply; - flood control, which needs to be carried out with a perspective of sustainable development, integrating protection of the river ecosystem and of wetlands; water shortage (low discharge) also needs specific management measures; - contamination of groundwater by nitrate and plant health products, and reducing the quantity of water in some aquifers. These issues will require coordination at the basin scale, but individual states and regions have already taken some measures to improve water quality and to mitigate problems

Chapter | 5.1 The Meuse River Basin

from water level fluctuations. A major decrease in orthophosphate concentration in the river has occurred since the early 1980s, although the decrease is still insufficient for controlling eutrophication. An effective effort for water quality improvement in the basin is the twofold greater wastewater treatment capacity in Wallonia. Another sign of recovery of the river and effectiveness of the actions taken over many years is the return of the Atlantic salmon. This is a good example how excellent results can be reached when restoration efforts are well-designed, supported by adequate scientific studies, coordinated among different countries and regions, and sustained over a long period of time.

Acknowledgements We thank the International Meuse Commission, and in particular to P. Racot, who provided various data from the ICM reports.

REFERENCES Capieaux, D. 2004. Diversite et dynamique des Cladoceres benthiques en Meuse. Memoire de Licence en Sciences Biologiques, FUNDP, 50 pp. De Ruyter van Steveninck, E.D., van Zanten, B., and Admiraal, W. 1990. Phases in the development of riverine plankton : examples from the rivers Rhine and Meuse. Hydrobiological Bulletin 24: 47–55. Descy, J.-P. 1987a. Etudes ecologiques de la Meuse en relation avec les rejets des centrales nucleaires. Annales de l’Association Belge de Radioprotection 12: 127–137. Descy, J.-P. 1987b. Phytoplankton composition and dynamics in the river Meuse (Belgium). Archiv f€ ur Hydrobiologie, Supplement 78, Algological Studies 47: 225–245. Descy, J.-P. 1992. Eutrophication in the River Meuse. In: Suttcliffe, D.W., Jones, J.G. (eds). Eutrophication: Research and Application to Water Supply, Freshwater Biological Association, Ambleside, UK, pp. 132–142. Descy, J.-P., and Ector, L. 1999. Use of diatoms for monitoring rivers in Belgium and Luxemburg. In: Prygiel, J., Whitton, B.A., Bukowska, J. (eds). Use of Algae for Monitoring Rivers III, Agence de l’Eau ArtoisPicardie, Douai, France, pp. 128–137. Descy, J.-P., and Empain, A. 1984. 1. Meuse. In: Whitton, B.A. (ed). Ecology of European Rivers, Blackwell Scientific Publications, Oxford, pp. 1–23. Descy, J.-P., and Gosselain, V. 1994. Development and ecological importance of phytoplankton in a large lowland river (River Meuse, Belgium). Hydrobiologia 289: 139–155. Descy, J.-P., Everbecq, E., Gosselain, V., Viroux, L., and Smitz, J.S. 2003. Modelling the impact of benthic filter-feeders composition and biomass of river plankton. Freshwater Biology 48: 404–417. Descy, J.-P., Reynolds, C.S., and Padisak, J. (eds). 1994. Phytoplankton in turbid environments: Rivers and shallow lakes. Developments in Hydrobiology, Vol. 100, Kluwer Academic Publishers, Dordrecht, 214 pp. Descy, J.-P., Servais, P., Smitz, J.S., Billen, G., and Everbecq, E. 1987. Phytoplankton biomass and production in the river Meuse (Belgium). Water Research 21: 1557–1566. Duvigneaud, J., and Saintenoy-Simon, J. 1995. Le meandre de la Meuse a Revin-Faliere. Adoxa 2: 26–28.

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Empain, A. 1977. Ecologie des populations bryophytiques aquatiques de la Meuse, de la Sambre et de la Somme. Relation avec la qualit e des eaux, ecophysiologie compar ee et etude de la contamination par m etaux lourds. PhD thesis, University of Liege. 179 pp. Everbecq, E., Gosselain, V., Viroux, L., and Descy, J.-P. 2001. POTAMON: a dynamic model for predicting phytoplankton composition and biomass in lowland rivers. Water Research 35: 901–912. GIREA, 1996. R eimplantation de v eg etations rivulaires en Meuse moyenne sup erieure. Rapport Region wallonne, Service de la P^eche.71 pp. + annexes. GIREA, 2004. Biodiversit e, gestion et entretien de la v eg etation des berges de la Meuse moyenne sup erieure. Rapport Region wallonne, Direction de la Nature. 102 pp. Gosselain, V. 1998 Phytoplancton de la Meuse et de la Moselle et impact du broutage par le zooplancton, Ph.D.thesis, University of Namur, Namur, Belgium, 459 pp. Gosselain, V., Campeau, S., Gevrey, M., Coste, M., Ector, L., Rimet, F., Tison, J., Delmas, F., Park, Y.-S., Lek, S., and Descy, J.-P. 2005. Diatom typology of low-impacted conditions at a multi-regional scale: combined results of multivariate analyses and SOM. In: Lek, S., Verdonschot, P.F.M., Descy, J.-P., Park, Y.S. (eds). Modelling Community Structure in Freshwater Ecosystems, Springer, pp. 317–342. Gosselain, V., Descy, J.-P., and Everbecq, E. 1994. The phytoplankton community of the River Meuse, Belgium: seasonal dynamics (year 1992) and the possible incidence of zooplankton grazing. Hydrobiologia 289: 179–191. Gosselain, V., Viroux, L., and Descy, J.-P. 1998. Can a community of smallbodied grazers control phytoplankton in rivers? Freshwater Biology 39: 9–24. Grevilliot, F., Broyer, J., and Muller, S. 1998. Phytogeographical and phenological comparison of the Meuse and the Sa^one valley meadows (France). Journal of Biogeography 25: 339–360. International Meuse Commission. 2005. International River Basin District Meuse. – Analysis, Roof Report. Secretariat de la Commission internationale de la Meuse, Liege, 104 pp. Joaquim-Justo, C., Pirlot, S., Viroux, L., Servais, P., Thome, J.-P., and Descy, J.-P. 2006. Trophic links in the lowland river Meuse (Belgium): assessing the role of bacteria and protozoans in planktonic food webs. Journal of Plankton Research 28: 857–870. Kestemont, P., Goffaux, D., Breine, J., Belpaire, C., De Vocht, A., Philippart, J.C., Baras, E., Roset, N., de Leeuw, J., and Gerard, P. 2002. Fishes of the River Meuse: Biodiversity, habitat influences and ecological indicators. Proceedings of the First Scientific Symposium on the River Meuse, International Meuse Commission (IMC), Maastricht, The Netherlands. Micha, J.-C., and Borlee, M.-C. 1989. Recent historical changes on the Belgian Meuse. In: Petts, G.E. (ed). Historical Change of Large Alluvial Rivers, Wiley & Sons, pp. 269–295. Micha, J.-C., Pilette, S. 1988. L’impact de l’homme sur l’ ecosyt eme Meuse. Presses Universitaires de Namur. University of Namur, Belgium, 140 pp. Reynolds, C.S., and Descy, J.-P. 1996. The production, biomass and structure of phytoplankton in large rivers. Archiv f€ ur Hydrobiologie, Beiheft 113, Large Rivers 10: 161–187. Rojo, C., Cobelas, M.A., and Arauzo, M. 1994. An elementary, structural analysis of river phytoplankton. Hydrobiologia 289: 43–55. Servais, P. 1989a. Bacterioplanktonic biomass and production in the River Meuse (Belgium). Hydrobiologia 174: 99–110.

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Servais, P. 1989b. Modelisation de la biomasse et de l’activite bacterienne dans la Meuse belge. Modelling bacterial biomass and activity in the River Meuse (Belgium). Revue des Sciences de l’Eau 2: 543–563. Servais, P., and Billen, G. 1989. Impact of a nuclear power plant on primary production and bacterial heterotrophic activity in the River Meuse at Tihange (Belgium). Archiv f€ ur Hydrobiologie 114: 415–429. Servais, P., Gosselain, V., Joaquim-Justo, C., Becquevort, S., Thome, J.-P., and Descy, J.-P. 2000. Trophic relationships between planktonic microorganisms in the river Meuse (Belgium): a carbon budget. Archiv f€ ur Hydrobiologie 149: 625–653. Smitz, J., Everbecq, E., Deliege, J.F., Descy, J.-P., Wollast, R., and Vanderborght, J.P. 1997. PEGASE, une methodologie et un outil de simulation previsionnelle pour la gestion de la qualite des eaux de surface. Tribune de l’Eau 588: 73–82. Stroot, Ph., 1989. Essai de valorisation de collections existantes de macroinvert ebr es a des fins de syn ecologie et de typologie des eaux courantes par utilisation d’analyses multivari ees: exemple des Trichopt eres du bassin mosan wallon. PhD thesis, University of Namur, 203 pp. Symoens, J.-J. 1957. Les eaux douces de l’Ardenne et des regions voisines: les milieux et leur vegetation algale. Bulletin de la Soci et e Royale de Botanique de Belgique 89: 111–314. Tu, M., Hall, M.J., de Laat, P.J.M., and de Wit, M.J.M. 2005. Extreme floods in the Meuse river over the past century: aggravated by land-use changes? Physics and Chemistry of the Earth 30: 267–276.

PART | I Rivers of Europe

Tubbing, D.M.J., De Zwart, D., and Burger-Wiersma, T. 1995. Phytoplankton dynamics in the River Meuse as affected by pollution. Netherlands Journal of Aquatic Ecology 29: 103–116. Usseglio-Polatera P., and Beisel, J.-N. 2003. Biomonitoring international de la Meuse: analyse spatio-temporelle des peuplements macroinvert ebr es benthiques sur la p eriode 1998–2001. Rapport final, Commission Internationale pour la Protection de la Meuse, LBFE, Universite de Metz, 133 pp. Viroux, L. 1997. Zooplankton development in two large lowland rivers, the Moselle (France) and the Meuse (Belgium), in 1993. Journal of Plankton Research 19: 1743–1762. etazooplancton en milieu fluvial. UniViroux L. 2000. Dynamique du m versite de Namur, Namur, 309 pp. Viroux, L. 2002. Seasonal and longitudinal aspects of microcrustacean (Cladocera, Copepoda) dynamics in a lowland river. Journal of Plankton Research 24: 281–292.

FURTHER READING Descy, J.-P., and Servais, P. 1988. La vegetation aquatique et le bacterioplancton. In: Micha, J.C., Pilette, S. (eds). L’impact de l’homme sur l’ ecosyst eme Meuse, Presses Universitaires de Namur, pp. 39–60.

Chapter 5.2

The Loire Basin Louis-Charles Oudin

Nicole Lair

Maria Leitao

Agence de l’eau Loire-Bretagne, 45063 Orl eans, France

Universit e Blaise Pascal, Laboratoire de G eographie Physique et Environnementale, UMR-6042 CNRS, Maison des Sciences de l’Homme, 63560 Clermont-Ferrand, France

Bi-Eau, 15, rue Lain e-Laroche, 49000 Angers, France

Patricia Reyes-Marchant

Jean-Fran¸cois Mignot

Pierre Steinbach

Asconit Consultants, agence CentreAuvergne, 24 rue du Sagnat, 63460 Jozerand

Agence de l’eau Loire-Bretagne, 45063 Orl eans, France

Conseil Sup erieur de la P^ eche, DIREN, BP 6407, 45064 Orl eans, France

Thibault Vigneron

Jean-Pierre Berton

Michel Bacchi

Conseil Sup erieur de la P^ eche, D el egation r egionale de Bretagne, 84 rue de Rennes, 35510 Cesson-S evign e, France

Universit e de Tours, UMR 6173, BP 60449, 37204 Tours, France

Bureau d’ etudes « RIVE », Rue Carnot, 37500 Chinon, France

Jean Emmanuel Roche

Jean-Pierre Descy

Laboratoire d’Ecologie, Universit e de Bourgogne, 6 Bd Gabriel, 21000 Dijon, France

Research Unit in Organismal Biology (URBO), University of Namur, Rue de Bruxelles 61, B-5000 Namur, Belgium

5.2.1. INTRODUCTION The 1012 km long Loire River (source at 1408 m asl) has a catchment of 117 054 km2 (20% of France) and an annual discharge of 868 m3/s (mean annual discharge for the period 1967–2008, data HYDRO, DIREN Pays-de-Loire). The river flows north from the central Hercynian Massif, then it turns west near the town of Orleans flowing over a sedimentary plain where it receives several tributaries from the western part of the Massif central (Figure 5.1a). Finally the river drains into the Atlantic Ocean after receiving tributaries from the Hercynian Massif armoricain. The Loire and its first large tributary Allier (source at 1423 m asl, 410 km length, catchment 14 310 km2) flow almost parallel from the heights of the Massif central south to their confluence downstream of the town of Nevers. The most important urban areas in this upper catchment are Saint–Etienne and Clermont–Ferrand. The Loire then flows for >300 km until merging with the next large tributary, the River Cher. More than 40% of the human population is concentrated in this valley and adjacent valleys of the Loire and Allier basins. Donwstream of Nevers, the river crosses the Val de Loire, the place of the world-famous castles and historic towns of Orleans, Blois, Tours, Saumur, etc. DownRivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

stream of Tours, there is still a quarter of the river course to go and the network which drains almost 60% (66 000 km2) of the Loire catchment becomes highly complex (Figure 5.1b). Here, within a distance of 100 km, the Loire adds waters from four major tributaries, thereby increasing the mean annual discharge more than twofold. First the Cher (source at 717 m asl, 367,5 km length, catchment 13 906 km2), then the Indre (source at 486 m asl, 287 km length, catchment 3000 km2) and the Vienne (source at 920 m asl, 372 km length, catchment 21 105 km2 ), coming from the west part of the Massif central (Millevaches plateau, Limousin tables) merge with the Loire. Here also several towns as Montlu¸con, Vierzon and Bourges on the Cher, Chateauroux on the Indre, Limoges and Chinon on the Vienne contribute to the anthropic pressure. The fourth tributary close to the town of Angers is the Maine (only 12 km length, but with a catchment of 22,194 km2) coming from the Massif armoricain. Within this part of the catchment, human activities, settlements, industry, and agriculture have been considerably developed along the main stem, and only about 10% of the population is found in respective sub-catchments of the Loire valley. Different entities can be distinguished along the Loire, including the upper basin (from the source to the confluence

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with the Allier), the middle Loire valley (from the ‘Bec d’Allier’ to the confluence with the Maine), the lower Loire valley (from the Maine to the estuary) and the estuary. There are a sequence of different natural habitats between the headwaters and the ocean. Gorges and ancient forests are found in the upper basin, and numerous islands, natural banks, riparian forests, braided reaches, meanders, and floodplains subject to flooding occur along the middle and lower Loire. In the upper basin, the river flows through a sparsely populated, narrow and incised valley. The alluvial plain increases in width in the intermediate section, which extends downstream from the first alluvial basin of the Massif central (including the plain of Forez on the Loire) to the basin of Issoire and the plain of Limagne on the Allier. Meandering reaches alternate with multi-channel reaches where sand banks or forested islands prevail. Fluvial dynamics are high in the unconstrained reaches near Roanne (Loire) and Vichy (Allier) up to the confluence with the Allier. Here, exceptional habitat and landscape richness has been well preserved. In the middle Loire valley, and particularly from Briare to Angers, the river is constrained by dikes built between the 12th and 19th century for protection against floods. Intensive agriculture and urbanization occur downstream of Briare. The channel is mostly straight with interspersed sand banks and islands, except for a stretch near Orleans where meanders occur. The river has been developed as a navigation channel in the lower Loire between Angers and Nantes, but large floodplains providing valuable habitat still exist. The estuary, in which the Atlantic Ocean forces the River to reverse its course, has important mud flats and reed stands. Finally, in the course of the river, ecologically important wetlands include fens and swamps at higher elevations, the plains of Forez and Sologne, the ponds of Brenne, without forgetting the banks of the shallow Lake Grand-Lieu close to Nantes (hydrologically connected to the Loire and its tributaries) which, depending on the water level, offers alternately floating forests, flooding meadows and marshes. Although the estuary has been severely affected by river engineering, large wetland areas have still been preserved in its area.

5.2.2. BIOGEOGRAPHIC SETTING Despite it has been civilized since the Antiquity, the large biodiversity of the natural areas of this ‘last wild European river’ has its roots in the long geological and human history and even if the pristine state has disappeared, the river illustrates the harmonious development of interactions between humans and their environment over two thousand years of history. The Loire runs partly through two continental ecoregions (Massif central and Bassin parisien south) and partly through two Atlantic ecoregions (south Atlantic and Bretagne). These interactive components are integrated in the six hydroecoregions, delineated by Wasson et al. (2004). These

PART | I Rivers of Europe

authors underlined that in the case of the Loire basin, the morphoregions show good agreement with the hydroecoregions. The settlement of numerous species, going from glacial relicts to warm areas species, was favoured by climate, and the habitats diversity maintained by the free hydrodynamic functioning that still occurs from highlands to ocean. Plants coming from far-off lands by the valleys are added to those typically mountainous, Mediterranean and Atlantic, increasing the floristic richness. The same goes for the fauna, in particular for terrestrial and aquatic invertebrates, which inhabit humid to dry areas, from ripisylve to banks, from gravel to sand beds. Birds, including the migratory species, as well as terrestrial and aquatic vertebrates, also exploit this great habitat diversity. To promote the protection of this remarkable biodiversity, the inter-regional ‘Plan Loire Grandeur Nature’ was implemented in 1994. The natural regional park Loire-Anjou Touraine situated between Tours and Angers was created in 1996 and the Val de Loire gained international recognition, thereby acknowledging the conservation efforts made at the level of the Loire basin. Since 2000, the Loire Valley between Maine and Sully-sur-Loire is included on the UNESCO list of World Heritage sites. It covers a distance of 280 km and an area of almost 800 km2. The European network ‘Natura 2000’ covers 25% of the surface area of the site, added with conservation organizations, such as the CORELA (Regional Conservation Centre for the banks of the Loire and its tributaries) etc. Several ZNIEFF (Natural Areas of Fauna, Flora and Ecological Interest) and ZICO (Important Areas for Bird Conservation) have also been delimited, underlining the interest for the biodiversity offered by the River and encouraging scientific research. Finally, as underlined in the ‘Loire Nature program’, because its exceptional ecological corridor and primordial wandering, the river Loire remains the stake in the European biodiversity.

5.2.3. HISTORICAL SETTING The Loire basin has probably been occupied by humans for 500 000 years. Numerous traces of the Bronze and Iron Ages occur along the river. Since prehistoric times, man has exploited aquatic life by fishing, hunting, and collecting aquatic vegetation. Historically, Etruscans and Greeks crossed the Loire basin, then the flat-bottomed ‘gabares’ and ‘toues’ (river barges) followed the prehistoric monoxylic pirogues, then the time of Loire navy ran until the 19th. Since the Gallo–Roman period, human activities (deforestation, agriculture, livestock farming, establishment of villages and towns, river traffic) had direct impacts on the river by increasing erosion and suspended sediments, straightening meanders, and isolating side arms (Bravard & Magny 2002). In the Middle Age, ‘turcies’ and then levees were built along 530 km of the river for protection against flooding. There was also intensive scattering of water-wheel mills, which

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Chapter | 5.2 The Loire Basin

succeeded water-boat mills of the 6th century that hung from bridges. Canals and aquaducts also were built (Surmely, in Bouchardy 2002; Burnouf et al. 2003; Courant & Cussonneau 2003). Historically, the river was largely navigable from the Massif central, evidenced by toll payments during the golden age of fluvial navigation, but which is presently limited to the estuary. This was the period when goods such as tiles moved upriver from Angers, when salt, hemp, then coal moved downriver from the upper Loire, and Auvergne wines were transported along the Allier. Nowadays, only some river transport of wine remains, from the famous vineyards of the Val de Loire. The Canals of Briare, Orleans, were abandoned at the end of the 19th century and rediscovered by the lovers of fluvial tourism. Over the course of time, the river has been transformed from human activities such as clearing the channel, burning trees, draining marshes, straightening meanders, and extracting sand from the river bed. Now the time has come in the way of sustainable development.

5.2.4. PHYSIOGRAPHY, CLIMATE, AND LAND USE The Loire originally flowed towards the English Channel before it changed direction towards the Atlantic Ocean. Tectonic deformations caused the new orientation of the river, thereby creating constrained valleys, the alluvial Loire valley, and a large part of the Atlantic beach that exists today (Cochet 2002). The present Loire basin crosses two geological domains: basement and sedimentary. The basement domain, with often siliceous rocks, metamorphic and fractured, contains underground water in deep cracks and in alternate impervious zones. In some cases granite or basalt outcrop and the Loire river flows upon the bedrock. The sedimentary domain refers to limestone tables with carbonaceous or siliceous rocks, and contains large aquifers. The two regions of the Massif central (the Loire–Allier basin, and the Limoges plateau), feature steep valley slopes and numerous gorges. In contrast, the levelling surfaces of the Massif armoricain region were cut into gorges and shallow wide valleys sit on the paleozoic sediments of the flattened erosional uplands. In general, land exploitation becomes more intense from upstream and east of the basin towards downstream and west. The human population is expected to increase in the middle and lower Loire and around urban centres, while large upstream regions should become less populated. In the upper Loire basin, the Loire and Allier flow alternately through gorges (in which several dams have been built) and small alluvial plains. This is a scattered habitat with volcanic and granitic areas favourable for livestock farming, which contrasts with the depressions of the tectonic basins, such the sediment filled Limagnes that favour agricultural activities. Several towns (Le Puy, Roanne, Digoin, Decize and Nevers on the Loire, and Clermont–Ferrand, Vichy and Moulins on the Allier) use water from the rivers.

Despite more industrialization than in the middle and oceanic Loire basins, this area is experiencing a decline in agriculture and population size, particularly in the highlands. From the Allier confluence downstream of Nevers, to the Cher tributary, the middle Loire flows over calcareous tables and sedimentary alluvial valleys with meandering stretches, gravel islands and sand banks. Here starts the Val de Loire in which the channel was developed for navigation, although little used today. The road of abbeys and that of the castles of the Kings of France, which end near the estuary, begin in this area. With several cities, three nuclear power plants and extensive agriculture, water uses were an important consideration here. In the central region, up to 70% of the territory is used for agriculture (cereals, sugar beet) which resulted in a loss of woodland elements (‘bocage’). Several forests and small lakes are in Sologne, and the vineyards of Loire extend over a large part of the river. Before reaching the granitic Massif armoricain, the Loire receives three tributaries (Rivers Cher, Indre and Vienne) over a distance of 30 km, then reaches Angers where it receives the R. Maine. The fourth power plant is located in this stretch of the river. Anthropogenic impacts remain more pronounced in the granitic Massif armoricain (dairy and livestock, pig breeding) than in the granitic Morvan or Limousin. The Loire basin, influenced by Mediterranean, Continental and Atlantic climates, imposes complex and highly variable weather conditions. It has between 1400 and 2200 h of sunshine each year, increasing from northwest to southeast. The upper Loire, largely influenced by the Massif central, differs from the upper part of the middle Loire, a plain without significant tributary inputs. The oceanic Loire, dominated by an Atlantic climate, starts approximately from the Cher area that remains influenced by the west of the Massif central and the Massif armoricain. Rare in summer, rainfall occurs essentially in early winter and early spring. A mild oceanic climate has promoted human activities for a long time in this area, allowing agriculture (cereals, garden products, vineyards) and cities (the Angers area is well known for its ‘mildness’). Silt and sands threaten the Loire estuary that extends from Nantes to Saint–Nazaire. Already heavily silted by the 17th century, the port of Nantes was abandoned in favour of the port of Saint–Nazaire built during this period.

5.2.5. GEOMORPHIC DEVELOPMENT OF THE MAIN CORRIDOR Different geomorphologic entities have been distinguished along the Loire, including the upper basin, an intermediate section, the middle Loire valley, the lower Loire valley, and the estuary (Vigneron, 2001, 2002). In the upper Loire, bank protection by riprap, gravel extractions and reservoir construction (Poutes (1941), Grangent (1956) and Villerest (1988) on the Loire, Naussac (1983) on the Allier), have induced physical changes in the couple Loire/Allier. From its source to the Grangent dam, the

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PHOTO 5.4 A typical riffle-pool succession in the upper Loire (km 46), in a granitic catchment (Photo: Aude Beauger).

Loire flows through deep gorges interspersed with small floodplains nested in tectonic basins (Photo 5.4). Fluvial dynamics here are reduced, although the geodynamic functioning of the river is near ‘natural’. Exceptions occur where small, urbanized basins have large extractions of alluvial gravels. Between Grangent and the Villerest dam, lies a 30-km long reservoir that strongly constrains fluvial processes. Massive exploitation of alluvial gravels in the low-flow channel for the city of Saint Etienne between 1950 and 1980 has resulted in deepening of the bed on average 1–2 m. The corresponding aquifer and main water source of the Forez basin has gone deeper as well, and may result in serious drinking water supply problems. Between Villerest and the Loire/Allier confluence are wide floodplains lying in deep tectonic troughs, alternating with more confined stretches through Bajocian limestone formations and the southern foothills of Morvan. Here, the river has more active fluvial dynamics, resulting in meandering in the Bourbonnais area. Spaces where geomorphological processes are most intense correspond to alluvial deposits. For instance, in the 68-km stretch between Diou and Imphy, the Loire has more or less

natural fluvial dynamics, with much bank erosion and vast alluvial deposits that are quickly colonized by vegetation and associated biota. Here, the Loire erodes 11 ha of land per year, 70% of this in the Bourbonnais area downstream of Diou. From the Allier confluence to the Maine confluence, the Loire flows through limestone plateaus of the south Parisian basin. It is almost completely bordered by levees from Nevers to Angers, with a width between dykes usually between 500 and 800 m. Because of the dykes, a mixed fluvial dynamic results, with braiding to anastomosis, with some channels and islands highly stabilized, whereas true braiding implies channel instability. The upper Allier River, from the source to VieilleBrioude, is mountainous with a flow that actively transports coarse materials that are then deposited as vast pebble banks. The removal of the Saint–Etienne-du-Vigan dam in 1998 added 18 000 m3 of sand, gravel and pebbles to the river, which are being transported downstream and creating alluvial environments in the main channel. From Vieille-Brioude to Pont-du-Ch^ateau, the ‘Limagne brivardoise’ reach flows through a rather mountainous area having a small tectonic

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ditch. The river is highly disturbed, notably from sediment extraction, but still maintains a dynamic flow regime. The Allier has a lower gradient in the lowlands, but undergoes greater anthropogenic impacts from large industrial developments in the valley. Up to Villeneuve, the 135-km stretch shows high morpho-dynamics with major ecological interest. The reach is interspersed with areas stabilized by various hydraulic management structures, notably around cities. Two dynamic areas are between Joze and Saint-Yorre, where active meandering occurs, and between Crechy and Moulins, where active lateral erosion occurs. Both are outstanding natural environments and partly classified as natural reserves. From Villeneuve down to the Loire confluence, the river has another fluvial character similar to braiding, which also has a high ecological and landscape interest. From the Allier confluence to the Maine confluence, the Loire flows through the limestone plateaus of the south of the ancient ‘Bassin parisien’ (Photo 5.5). It is almost completely bordered by levees from Nevers to Angers, with a 500– 800 m width between dykes. Because of the dykes a mixed fluvial dynamic results, ranging from braiding to anastomosing with some channels and islands highly stabilized and

others in braided channels being unstable. As in the upper Loire, gravel extractions have also dipped the riverbed by up to 3.5 m in the lower river, minored the low water level (and altered from place to place the alluvial forests). Three stretches are distinguished in this middle Loire sector: (1) alluvial banks between the Allier confluence and Bonny-surLoire are highly mobile with stable forested islands and numerous side channels, (2) large sand-clay deposits carried from the Massif central are found between Bonny-sur-Loire and Blois (Photo 5.6), and (3) along the last 90 km between Tours and Angers, a succession of islands and alluvial banks causes a ‘valley’ landscape. Despite gravel extractions, in the Cher valley, for example between Vierzon and Villefranchesur-Cher, the fluvial dynamics remains active, originating alluvial forests and open areas. Further, in the Loire-et-Cher department, several hectares are scattered of wooded islands, sandy shores, hydraulic annexes, secondary branches and ‘boires’, the local name of the little waters bodies dispersed close to the banks of the Loire. The lower Loire downstream of the Maine confluence flows through the southern Massif armoricain. The river retains an essentially fluvial character down to Cou€eron before becoming estuarine with some maritime influence. At low flows, the stage decreases by 1.5 m at the Maine/ Loire confluence and by 3.5 m at Nantes, and strongly influences river dynamics. A tidal influence is noticeable up to Ancenis about 90 km from the sea and estuary sediments now occur in the former fluvial zone. Despite being strongly altered by harbour development, the estuary still has nearly 20 000 ha of wetlands (Malavoi 2002).

5.2.6. HYDROLOGY AND TEMPERATURE

PHOTO 5.5 The meandering middle Loire and the nuclear power plant of Belleville-sur-Loire (km 500) (Photo: Jean Roche).

Throughout its geographical situation, the Loire climatic variations impose to the River a nival–pluvial regime. The climatic variations generate larges differences in temperature and cause a hydraulic regime very variable. In the higher drainage basin that gathered the waters coming from the mountain tops of the Massif central, the water level is controlled by several dams, listed above (Lair et al. 1996). After the Allier confluence the discharge is on average of 318 m3/ s. Mean monthly discharge of the Loire shows a general seasonal pattern characterized by peak flows in winter and low flows from July to October. Measured at Nantes-SaintFelix for the period 1967–2008, the maximum and minimum discharge were 1520 m3/s in January and 258 m3/s in August. Low flows have been regulated in the Allier since the Naussac reservoir became operational in 1983, which ensures a flow rate of 6 m3/s at Vieille-Brioude throughout the year. The hydrology of the Loire between Roanne and Nevers has been regulated since 1984 by the Villerest dam just upstream of Roanne. This dam limits flood peaks to 1000 m3/s and sustains low flows all year at around 8– 10 m3/s at Roanne and 60 m3/s at Gien for the functioning of power plants on the Loire downstream of Nevers.

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PHOTO 5.6 The sand banks of the Val de Loire (km 640) in the castels area (Photo: Patricia Reyes-Marchant).

Three major flood types can be identified in the Loire and Allier basins: ‘Cevenole’ floods, oceanic floods and mixed floods. ‘Cevenole’ floods are common at the end of summer and in autumn in higher elevations in the basin. In the Cevennes mountains, precipitation can reach 300–400 mm in a matter of days. The last major ‘Cevenole’ flood was in September 1980 in the higher watersheds of the Loire and Allier. Oceanic floods most often originate from left-bank tributaries that drain the west basin and are fed by oceanic perturbations. They are common in spring, autumn, and early winter and are rare in summer. Collapsing levees in various valleys reduced the peak flow at Tours. The Loire flood discharge is typically higher than that of the Allier with rare exceptions such as in 1790 when the Allier reached 5000 m3/ s at Le Veudre. The last major flood in the middle Loire was in October 1907 with a peak flow of 4200 m3/s at the Allier confluence. Mixed floods result from the combination of the two former types, and can have exceptionally high discharge. The 19th century has had three extreme mixed floods in 1854, 1856 and 1866. In 1856, the flood was 3500 m3/s in the Allier and 4000 m3/s in the Loire at Nevers, close to their confluence. It was 7000 m3/s after the mixing Loire–Allier and, despite absorptions in the valleys, it was still 6000 m3/s at Tours. The harshness of low flow periods is an important characteristic of the hydrological regime of the Loire river network. In July 1949, the flow was so low that one could walk across the Loire at Orleans. The ratio between summer low flows and maximal floods upstream of Roanne is 1:1600, and these low flows allow important sand and gravel banks to emerge between multiple channels. In 1976, <20 m3/s were flowing at Orleans. Long-term monitoring conducted by

Electricite de France from 1971 in this area illustrates the hydrologic regime of the middle Loire. On average, despite large variability from year to year, the large floods of February/March are usually more sudden than in autumn when flood waters tend to increase more slowly. Here, low flows often persist later in the season. The drought periods in recent years have resulted in very low water levels that have favoured the growth of algae and aquatic plants. Long-term records in temperature also can be derived from the long-term monitoring programs on the middle Loire by Electricite de France (Lair & Reyes-Marchant 2000). Since 1980, temperatures measured bi-monthly, from endJune to early-September between 11 and 15 h in the running water at Saint-Laurent-des-Eaux (Rkm 640) show little change over time. Another study derived from a continuous monitoring performed by EDF close to the bank, found that the average annual and summer temperatures of the Loire have risen by 0.8 C, especially since the 1980s, related to the low water levels (Moatar & Gailhard 2006).

5.2.7. BIOGEOCHEMISTRY Analyses completed from 1995 to 1996 at 30 stations in the Loire basin (Ivol-Rigaut 1998), showed that conductivity, pH, alkalinity and hardness differ across regions. The calcareous areas (carbonate, alkaline waters) contrast with the siliceous lands of the Massif central (acid waters), with the Sologne and granitic Massif armoricain being intermediate. Over the long-term, conductivity has progressively increased since 1980 (Lair & Reyes-Marchant 2000), (Figure 5.6). Concentrations of ammonium and phosphate are highest in

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0.6 y = 0.348x + 219.23

Phosphate (mg/L)

Conductivity (µS/cm)

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FIGURE 5.6 Time series of conductivity in the Loire at Saint-Laurentdes-Eaux (Rkm 640). Data source: Electricite de France.

the granitic Massif armoricain and Sologne area. Extensively used for agriculture, nitrates are often high in this Massif and the calcareous areas. Some fertilizers contain sulphides, and a correlation between sulphide and nitrate concentration in surface waters indicates sulphides originate from agricultural practices (Ivol-Rigaut 1998). Excess nutrients cause eutrophication and during the growing periods the middle Loire reached chlorophyll a values up to 250 mg/L. However chlorophyll a concentrations declined in recent years, which might be attributed to phosphorus removal from wastewaters (Figure 5.7). Indeed, since the year 2000 (data 2000–2007) at Dampierre-en-Burly (Rkm 550) and at Saint-Laurent-des-Eaux (Rkm 640), observations made during the growing season showed the phosphorus quantities become progressively lower, possibly limiting algal growth. In parallel the classical summer depletion in nitrates is largely attenuated. In contrast, at annual scale, compared performances of different algorithms estimate a recent decrease in average nitrate concentration (Moatar & Meybeck 2005). Suspended solids are transported mostly during high water periods from erosion of the crystalline rocks in the Massif central. They are much lower during low flows, whereas carbonate waters become prevalent (Grosbois 1998; Grosbois et al. 2001). Carbonates originate from the sedimentary basin at high flow and from carbonate precipitations at low flow. Carbonate precipitation results from the photosynthetic activity of the potamoplankton and can represent 11–33% of the total particulate flux downstream of Tours and up to 50% at the estuary. The rate of physical erosion appears constant in the basin, equalling 7 tons/km2/year. The flux of particulate transport increases with watershed surface area (Rodrigues et al. 2006).

5.2.8. AQUATIC AND RIPARIAN BIODIVERSITY 5.2.8.1. Phytoplankton Phytoplankton in the Loire has been studied since 1920, but early studies were qualitative and mostly done on the downstream stretch (Des Cilleuls 1928; Bioret 1931; Germain

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FIGURE 5.7 Time series of the phosphate concentration in the Loire at Saint-Laurent-des-Eaux (Rkm 640). Period end-June–early October. The year 2007 was characterized by exceptional high waters. Data source: Electricite de France.

1935). During the 1980s, large industrial plants were constructed, especially nuclear power plants, and phytoplankton monitoring was initiated in the middle Loire over a stretch of 250 km to assess the environmental impacts on the river (Lair & Sargos 1993; Lair & Reyes-Marchant 2000; Picard & Lair 2005). Further, the Loire-Bretagne Water Authority has included in the national network for water quality monitoring several sampling sites along the river. Based on a 10year dataset that included chlorophyll a measurements, an increase in eutrophication was noticed in 1990, with chlorophyll peaks reaching 210 mg/L. In 1991, phytoplankton samples were added to the monitoring program. The Loire has the highest phytoplankton diversity in France, and probably among other large European rivers (Rojo et al. 1994). During the growing season, at the Rkm 640 nuclear power plant, the algal richness ranges between 97 and 127 species, with 65– 79 blue-greens, 16–31 diatoms and 10–14 blue greens (optical microscopic observations from 1995 to 2007). Surveys carried out on the rivers Marne, Seine and Oise (Leitao & Rouquet 2002) reported much lower biomass and diversity than that found in the Loire. In the middle Loire, the most productive groups are diatoms and green algae. The greatest biomass of cyanobacteria occurs mainly in the downstream reaches. At high flow (>800 m3/s), phytoplankton is diluted and biomass low. When discharge decreases to 300 m3/s, unicellular centric diatoms become common, especially Cyclostephanos invisitatus, C. meneghiniana, S. hantzschii, and Thalassiosira pseudonana. At low flows (<100 m3/s) delicate multicellular forms appear such as Fragilaria crotonensis, Nitzschia fruticosa, and Skeletonema potamos, and are often mixed with green algae typical of summer assemblages. The green algae are either large colonial forms (Coelastrum microporum, C. reticulatum, Micractinium pusillum), cells connected by gelatinous threads (Dictyosphaerium pulchellum, D. tetrachotomum, Dichotomococcus curvatus, Westella botryoides), or star-shaped colonies (Actinastrum hantzschii, Ankistrodesmus fusiformis). Prostrate colonies, such as Scenedesmus, are regularly observed. The most frequent species are S. bicaudatus, S. intermedius, S. opoliensis, S. spinosus, and S. sempervirens. The average contribution of green algae

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Algal density (106 cell/L)

to total phytoplankton biomass is on average 15%, which corresponds to 1.3 mg C/L in the middle Loire. In the Loire at Orleans, taxa contributing to >5% of the mean annual biomass include only 2 green algae and 4 diatoms. The genus Stephanodiscus contributes <5%, but is present all year (as is Chlamydomonas). In contrast, taxonomic richness at this site is high (264 taxa recorded over 8 years, on average 34 taxa per sample), as is the Shannon’s diversity index (range: 3.32–4.62). Summer assemblages, in particular, often contain >50 taxa, not including a comprehensive list for diatoms. The nutrient-rich middle Loire has a diverse array of aquatic habitat types that may contribute to such high diversity in algae (Moatar & Gailhard 2006). Leitao and Lepr^etre (1998) documented the seasonal and longitudinal patterns of phytoplankton at 6 stations between Rkm 150 and Rkm 875 from 1991 to 1994. Samples from the upper Loire were characterized by diatoms, whereas green algae dominated the middle and lower river. Seasonally, diatoms dominated with low diversity at high flows, whereas green algae and cyanobacteria with high biomass were common in summer during low flows. The diatoms S. hantzschii and Cyclostephanos invisitatus made up most of the spring phytoplankton assemblage, as found in other French (Leit~ao and Rouquet 2001) and European rivers (Descy et al. 1994). Maximal phytoplankton biomass occurred in summer in the middle and lower river, and green algae dominated (multicellular forms such as Actinastrum, Coelastrum, Dictyosphaerium, Scenedesmus, Westella). The delicate diatom Skeletonema potamos and, in the lower river, cyanobacteria (Planktothrix agardhii, Limnothrix redekei) were also common. Phytoplankton decreased in late summer–autumn in the upper river and somewhat later in the middle Loire, when diatoms of the genera Cyclotella (C. meneghiniana, C. pseudostelligera) and small Thalassiosira (T. pseudonana) maintain populations. Tributaries affect the main river phytoplankton community either by adding species in spring or causing biomass decrease in autumn through dilution effects. Available data on total algal abundance in the middle Loire (1982–2007) showed that phytoplankton biomass has decreased in the last decade (Figure 5.8), as with a decrease in chlorophyll in recent years. Whether this trend is related to 200 150 100 50 0 1985

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FIGURE 5.8 Time series of the phytoplankton cell abundance in the Loire at Saint-Laurent-des-Eaux (Rkm 640). Period end-June–early October. The year 2007 was characterized by exceptional high waters. Data source: Electricite de France.

nutrient reduction efforts or to another factor (such as the expansion of the Asian clam Corbicula spp.) is not clear.

5.2.8.2. Macrophyte Communities Plant diversity along the river is mainly explained by the geographic extension and morphology of the hydrographic network as influenced by climate, the relatively natural hydrologic regime, the sedimentary, edaphic and geomorphologic characteristics that cause microclimatic variability, and the relatively low anthropogenic pressure compared to the majority of other European large rivers. The floodplains between the Forez plain and the upper estuary, excluding mountainous areas and the estuary itself, are home to over 1340 taxa of vascular plants, distributed within 475 genera and 119 families (Cornier 2002). The most common are herbaceous plants such as Asteraceae (155 taxa), Poaceae (138 taxa) and Fabaceae (92 taxa). Among the woody plants, Salicaceae are the most numerous (19 taxa). In general, the macrophyte communities are poorly developed because of high sediment mobility and reduction in light penetration related to phytoplankton development. River side-arms with low or no flow are colonized by different types of hydrophytes such as water-lilies, water-crowfoots, water milfoil. Lastly, various types of plant communities are unevenly distributed from the riverbank to the floodplain forests.

5.2.8.3. Heterotrophic Plankton Various data on bacterioplankton and protozooplankton are available for the middle Loire (Picard & Lair 2005). Heterotrophic bacteria (up to 14 109 cells/L) consisted of cocci (49% on average), rods (35% on average), colonies (12% on average), and filaments (4% on average). Algae were dominated by the small forms (0.8–1.2 mm). At densities up to 9 106 cells/L, heterotrophic flagellates, described according to shape (spherical or ovoid), size (1–18 mm) and number of flagella, comprised 22 morphotypes. Most were spherical and the >5 mm size-class was most abundant (88% on average). Five classes, 19 families and 22 genera of ciliates have been found in the river, and are dominated by Oligotrichs (Strobilidium, Strombidium) and Peritrichs (Vorticella). Depending on the year, Prostomatids (Urotricha), Hymenostomes (Cyclidium), Phascolodontes (Phascolodon) and Haptorides (Didinium, Mesidinium) were associated with a few Heterotrichs (Stentor) whose distribution varied along the river. Their densities can reach up to 51 103 cells/L and small sizes dominate. In 1999, the <50-mm size class represented on average 73% of the assemblage, that of 50– 100 mm accounted for 20%, and those >100 mm comprised the rest. These microorganisms (including autotrophic nanoplankton) provide high quality food for metazooplankton, mainly rotifers. Modelling using the bioenergetic model ECOPATH (Christensen & Pauly 1992) suggests there are

Chapter | 5.2 The Loire Basin

sufficient food resources to support up to 70 000 rotifers/L, a value 10 times higher than that found in the river. This indicates that other factors must regulate metazooplankton abundance in the river. A short generation time allows populations to persist in unstable habitats such are those in the middle Loire (Lair 2005, 2006). From 1995 to 2004, 61 species have been collected at Dampierre-en-Burly (Rkm 550) and Saint-Laurent-des-Eaux (Rkm 640). The community is dominated by Brachionidae (44% at Dampierre-enBurly and 34% at Saint-Laurent-des-Eaux) and Trichocercidae (13% and 16%, respectively). Depending on the year, Asplanchnidae (6% and 10%, respectively) can be quite abundant. Also occurring are Notommatidae (6% and 9%), Synchaetidae (7% and 10%), and Epiphanidae and Lecanidae (5% each at both sites). Some summers, the abundance of Flosculariidae (6% and 4%, respectively) is influenced by the invasion of the warm stenothermal Sinantherina socialis (Champ 1978). On account of geomorphological changes and chance dispersal, it is not surprising to collect a mixture of planktonic and epibenthic rotifers. Over 10 years, the dominant species sampled included Anuraeopsis fissa, Asplanchna priodonta, Brachionus angularis, B. calyciflorus, B. leydigi, B. quadridentatus, Cephalodella catellina, C. gibba, Epiphanes macroura, Keratella cochlearis, K. tecta, Lecane luna, Polyarthra dolichoptera, P. vulgaris, Rhinoglena frontalis, Sinantherina socialis, Trichocerca brachyura, T. pusilla and T. similis. Depending on the year, the density of the planktonic species fluctuated from 49 to 69% at Dampierre-en-Burly and from 41 to 74% at Saint-Laurent-desEaux, that of epibenthic species from 31 to 51% at Dampierre and from 26 to 59% at Saint-Laurent. Such results illustrate that rotifer numbers were directly affected by flow conditions in the river, with numbers decreasing at high flows.

5.2.8.4. Benthic Invertebrates The invertebrates of the Loire and its tributaries are quite diverse, partly explained by the particular biogeographic situation of the basin. For instance, some meridional species, which require particular microclimates such as sandy habitats that are heated during the day, are found in the basin, as Pseudoneureclipsis lusitanicus (Tachet et al. 2001). Further, the main channel has been modified for navigation purposes, but navigation was abandoned at the end of the 19th century and the channel has a near natural configuration today. This allowed the survival of rare species such as some dragonflies (Ophiogomphus cecilia and Gomphus flavipes) and molluscs (Pseudunio auricularius and Margaritifera margaritifera). A study of the macrobenthic communities based on the available literature (1978–1994) indicates the Loire still has high biological potential (Bacchi 2000). This author reported 138 taxa dominated by 5 insect orders (Plecoptera, Ephemeroptera, Trichoptera, Coleoptera and Odonata). Repre-

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sentatives of all groups can be found from the headwaters to the mouth, including the temperature sensitive Plecoptera. The general typology of the river follows the scheme proposed by Verneaux (1973), based on the decrease in macrobenthic pollution-sensitive taxa. The well-oxygenated headwaters of the upper Loire sheltered, in their granitic and volcanic coarse substrates, a wide diversity of Plecoptera and the most pollution-sensitive Ephemeroptera and Trichoptera. Taxa such as Arcynopteryx compacta, Brachycentrus subnubilus or Odontocerum albicorne were present, underlining the good quality of the water. Then, in the course of the couple Loire/Allier, major changes occurred. More tolerant species as Chimarra marginata, Cheumatopsyche lepida, Hydropsyche contubernalis, H. exocellata, O. oaculatum, Potamanthus luteus or Raptobaetopus tenellus (a new species in the Loire) illustrated both the natural gradient along the river continuum and the increase in anthropogenic pressure (Guinand et al. 1996; Beauger et al. 2006; Beauger 2008). Rheophilous taxa remain abundant. More downstream, the successive dams altered the bed load transport and the anthropogenic pressure that progressively increase in the course of the river, modified the macrobenthic community for which other species succeeded. Indeed, in the middle Loire also, the changes in water quality due to agricultural, domestic and industrial inputs has facilitated the colonization by new species, adapted to disturbed environments, that may replace other pollution-tolerant taxa. The macrobenthic fauna distribution largely depends on the hydro-ecoregions in which the opposition between granitic and calcareous areas is manifest, the predaceous Plecoptera missing in the calcareous tables of the middle Loire. In contrast with the Massif central, the pollution sensitive fauna of the Massif armoricain is present in lower proportions, conversely to the molluscs, which are more abundant. The lower taxa diversity of this area would be linked to the lower habitats diversity. However, the faunistic potential remains high: Chloropelidae, Perlidae, Perlodidae, Taeniopterygidae, Brachycentridae for example are still present in the lotic areas of the Massif armoricain (Ivol-Rigaut 1998). Corbicula fluminea, an Asiatic invasive bivalve species, was probably propagated by navigation, from the Loire estuary. The ‘Asian clams’ also reached the rivers Allier (2001) and Cher by canals, and in Auvergne it has been used as fishing bait (Brancotte & Vincent, 2002). It has high densities (>2000 individuals/m2) at some sites along the Loire and Vienne Rivers. Its occurrence may partly explain the dramatic decrease in phytoplankton and the progressive development of aquatic macrophytes at some sites. The taxonomic diversity of aquatic invertebrates, already high in the headwaters, is highest between the Allier/Loire confluence and the estuary. This stretch of the river had little channelization or regulation and has numerous peri-fluvial habitats also favouring taxa such as coleopterans, the number of which significantly increase from the source to the estuary.

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5.2.8.5. Amphibians Amphibians observed in the Loire basin are reported in Cochet et al. (2002). The fire salamander (Salamandra salamandra) is the most widespread species in the basin. Five new species occur in France, and include the great crested newt (Triturus cristatus), the marbeled newt (Triturus marmoratus), common newt (Triturus vulgaris), Alpine newt (Triturus alpestris) in the stagnant waters of the upper basin, and the palmate newt (Triturus helveticus). The common toad (Bufo bufo) is found in slow flow areas, the midwife toad (Alytes obstetricans) rarely occurs in the floodplain but is more frequently found in the uplands. The Natterjack toad (Bufo calamita) occurs in oxbows and gravel pits, the common spadefood (Pelobates fuscus) and the western spadefood (Pelobates cultripes) are occasionally found in the lower basin, and the Parsley frog (Pelodytes punctatus) is found in the entire basin except in some tributaries. The yellow-bellied toad (Bombina variegata) is relatively common in the upper basin, and the common tree frog (Hyla arborea) is found throughout the basin. The green frog (Rana temporaria) occurs in the entire Loire basin, and the agile frog (Rana dalmatina) is limited by altitude and found more in the lower basin. The edible frog (Rana esculenta) and Iberian green frog (Rana perezi) are found more in the south, the marsh frog (Rana ridibunda) more in the north, and the pool frog (Rana lessonae) is more frequent in stagnant waters in the floodplain.

5.2.8.6. Fishes The diversity of fish in the Loire basin is high, and includes 57 species from 20 families (Souchon 2002). A remarkable feature is that numerous migratory and anadromous fish still occur; 11 of these species use the Loire/Allier system to complete their life cycle that comprises both marine and freshwater stages. The Atlantic salmon (Salmo salar) forms the last wild European population migrating into a large river system. The sea trout (Salmo trutta) is recorded but lacks good population records. The shad (Alosa alosa) is common and is more frequent than the twaite shad (Alosa fallax). The sea lamprey (Petromyzon marinus), the European river lamprey (Lampetra fluviatilis) downstream, and the smelt (Osmerus eperlanus) spawn in freshwater habitats but stay in the estuary. The catadromous eel (Anguilla anguilla) is common in the upper Allier River. The flounder (Platichtys flesus), and two species of flathead mullet (Mugil ssp.) also forage in freshwater habitats near the mouth. The European sturgeon (Acipenser sturio) present until 1940 is the only native fish to have become extinct within the Loire basin. Except for a few species with a Mediterranean affinity or central European origin, the Loire basin comprises almost all the fish species found in the freshwaters of France. Species richness is highest (20–25 species) in sections where the channel is wide such as the Middle Loire, the lower Vienne, and the rivers Allier, Creuse and Cher. These reaches

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are less affected by river engineering and contain a mosaic of complex and diverse aquatic habitats (Vigneron 2001, 2002). Streams of the Auvergne, Sarthe and upper Mayenne host almost intact fish populations with species sensitive to pollution or habitat degradation such as brown trout (Salmo trutta), sculpin (Cottus gobio), and the European brook lamprey (Lampetra planeri). Near the Allier/Loire confluence, the canal between the Loire and Rhone (canal du Nivernais) opened an immigration route for species from the Rhone basin such as sander (Sander lucioperca), nase (Chondrostoma nasus), wels catfish (Siluris glanis), and some species potentially endangered like grayling (Thymallus thymallus), sofie (Chondrostoma toxostoma), burbot (Lota lota), and bitterling (Rhodeus sericeus). This gateway to the Rhone basin probably allowed the colonization of non-native species such as rock bass (Ambloplites rupestris). High species richness and the occurrence of endangered species with special ecological requirements occur here, including burbot, sofie, grayling and nase, which coincide with relatively high habitat diversity and minor human impacts. The ecologically and hydromorphologically intact area near the Allier/Loire confluence plays an important role with respect to the protection and biodiversity of the Loire basin (Persat & Keith 1997). However, the status of the fishery as characterized by a fish index (Oberdorff et al. 2002) decreases along the river due to pressures of intense agriculture, river engineering, and the discharge of urban and industrial effluents. These impacts increase towards the mouth of the basin where environmental conditions become prohibitive for fish during some periods in the estuary (Steinbach 2002). Accumulation of pollutants from diffuse sources and river channelization impose the most severe constraints on fish. In this respect, the estuary suffers particularly from channel excavation and lowering of the stage height. Characteristic fluvial fishes have disappeared in reaches affected by the tidal oscillation and changes in salinity. From the estuary to the gorges in the upper Loire, fish populations have been affected by the drainage of oxbows, secondary channels and floodplain swamps, mostly through the loss of primary spawning areas. Some of these floodplain habitats have become dry or isolated from the river because of channel incision. The pike (Esox lucius), which is at the top of the food chain, is the most sensitive fish with respect to the general degradation of fluvial habitats, particularly from the loss of aquatic vegetation used for spawning and nursery grounds for juveniles. For instance, pike use inundated meadows during the spring floods for spawning areas, and secondary channels and oxbows until flood recession for nurseries. The adults use aquatic vegetation along the main channel. Besides pike, the great majority of fishes in the river, such as eel, carp and rudd (Scardinius erythrophtalmus), also use these fluvial habitats during their life cycle as they are highly diverse and productive environments, especially if allowed to be inundated in spring. The estuary itself is impacted by blooms of microalgae that limit environmental conditions

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for fish during summer. Most affected fishes with a life cycle that includes relatively long periods in the transition zone between freshwater and marine water. The poor environmental status of the estuary presumably enhanced the decline of certain migratory fish such as the twaite shad as well as the extinction of the European sturgeon at the end of the 1940s. The most emblematic fish in the Loire is without doubt the great Loire salmon (Steinbach 2005), a subspecies of Atlantic salmon. Here occurs the last endemic population of large European river basins because some spawning grounds in the upper Allier and below the hydroelectric dam of Poutes Monistrol were not affected migration barriers. The Loire sustains the last strain of large-sized salmons capable of long migrations from areas in the sea near Greenland over 6000 km from the Loire mouth. They then migrate to the spawning grounds in the upper Allier more than 800 km from the sea. Unfortunately, the Loire population is decreasing. Under favourable hydroclimatic conditions, that is before dam construction in the 19th century, the annual salmon stock was estimated to equal about 100 000. In 1992/1993, there were only about 50 female salmons in the spawning areas of the upper Allier. After dam construction following the implementation of river regulation mandates in 1919, an important percentage of the spawning area was lost. Environmental conditions in the sea also contributed to the loss in the fishery (Thibault 2001), perhaps due to increased water temperatures in the northern Atlantic that have increased since 1987 (Merceron, 2005). The higher temperatures have resulted in a change in phytoplankton composition and an increase of the phytoplankton standing stocks. Further, Calanus finmarchicus, a small crustacean zooplankton and preferred prey of young salmons, declined in abundance. The decline in the fishery led to a total ban of salmon fishing within the Loire basin in 1984 and a reduction in the quota of the fish catch in the sea near Greenland. A restoration program and fish pass installation, allowing access to certain salmon streams in the Limousin, Auvergne and Morvan areas, started in 1976. In 1998, two migration barriers (old hydroelectric dams) were removed at the lower end of the Vienne basin (at Maison Rouges) and in the upper Allier (at St. Etienne de Vigan). A European protection program started in 2001 uses a large salmon hatchery at Chanteuges (upper Loire) to provide juvenile salmon for stocking. These efforts within the framework of ‘Plan Loire Grandeur Nature’ resulted in the return of 500 salmons in the river in 2005. This number represents only about 25% of the fish that can use the available upstream spawning areas, and is quite low relative to historical salmon runs. The length of the migration route within the Loire/Allier system makes it susceptible to human impacts. Pollutants accumulate along the main stem in parallel with phytoplankton blooms, and the sequence of dams cause migration delays and impede access by fish to the spawning areas. The restoration of rivers used for salmon migration is a long-term project. Beginning about 25 years ago, the main

focus was on the migration of salmon but now also includes other species such as shad, lamprey and eel. Shad stocks started to recover after major spawning areas became accessible during spring floods. However, besides these periodic exceptions, the shad population remains stagnant and at low levels compared to the natural potential of the river. Lampreys recently started to re-colonize the Creuse River. The eel, once very abundant, has declined in abundance. This decline is alarming because the Loire basin is one of the best potential habitats in the centre of the eel range. Tributaries of the Maine (Mayenne, Sarthe, Loir), directly accessible from the estuary, have received priority for restoring migratory conditions.

5.2.8.7. Avifauna Populations of nesting birds along the Loire have been monitored since the 1980s (Roche et al. 1993a, 1993b; Frochot et al. 2003). Three censuses (1989–1990, 1995–1996 and 2001–2002) that counted birds every 5 km gave information on species abundance and composition (Blondel et al. 1970). These observations revealed a high bird diversity that comprised 164 nesting species (64% of the species nesting in France) and showed a predominance of water birds (54 species) followed by species of managed forests (44 species) and more natural forests (41 species). In contrast, birds of open and rocky habitats only represented 13 and 12 species, respectively. All three surveys showed similar results, suggesting the Loire bird fauna having a high degree of stability in space and time. There did occur some changes with the appearance of new nesting birds such as the Mediterranean gull (Larus melanocephalus) and the streaked fantail warbler (Cisticola juncidis), and significant variations in the abundance of other species. For most of these species, the observations coincided with general trends observed in France or Europe (e.g. the expansion of the Mediterranean gull). For others, changes are more difficult to explain (e.g. the little ringed plover Charadrius dubius). Of the 17 species showing significant fluctuations in abundance, 5 show increasing and 4 decreasing trends in abundance, and the remaining 8 species show no trend. Most results indicate that the avifauna of the Loire basin has changed little in the last 12 years. Along the Allier River, two censuses were completed at 91 stations placed 5 km apart from the source to the confluence with the Loire (Roche et al. 1993a, 1993b; Faivre et al. 1998). Bird populations in the riparian zone of the Allier were apparently quite stable between 1991 and 1997 with 123 nesting species recorded in both years and including some rare species seen only in 1991 (5 species) and 1997 (8 species). The survey results suggested the Allier as being relatively good habitat for birds. The bird data were compared with descriptors of the riverine landscape based on satellite images, and showed strong correlations between bird populations and large-scale landscape

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features (ground/soil cover) along an upstream–downstream gradient. Along the Loire, birds are particularly sensitive to the morphological changes caused by fluvial dynamics that determine the longitudinal succession of bird species as found for other large European rivers. For instance, the dipper (Cinclus cinclus) occurs in upper torrential zones, the common sandpiper (Actitis hypoleucos) in braiding zones (Roche et d’Andurain 1995), tern (Onychoprion sp.) in anastomosing zones (Roche 1993), and shelducks (Tadorna sp.) in estuaries (Roche et al. 1993a, 1993b). Lastly, the bird fauna is rather impoverished upstream of the dam at Villerest due to the permanent inundation of the former braiding zone.

5.2.8.8. Aquatic Mammals Populations of the European beaver (Castor fiber) and Eurasian otter (Lutra lutra) are continuously expanding (Bouchardy, 1998). This expansion can be seen by the various damages caused be their activities, especially at the local scale. The southwestern water vole (Arvicola sapidus) also occur. This little-known species has been thought to be declining, but little study has been completed on the species. The European mink (Mustela lutreola) considered to be extinct in the Loire basin has also been recorded. Non-native species such as nutria (Myocastor coypus), originally native to temperate South America, and the muskrat (Ondatra zibethicus) are present in the Loire basin. European badger (Meles meles) may cause problems through its burrowing activity that can affect the stability of levees/dikes during floods. The American mink (Mustela vison), a direct competitor of the European mink, needs monitoring, in order to estimate the potential expansion of its population.

5.2.9. MANAGEMENT AND CONSERVATION Historically, the water quality of the Loire was quite good in the 18th century. Various references note that its waters were recommended for better health because of salt composition. A report in 1786 (Pellieux 1786) writes that a person of Orleans affected by early stages of chronic disease was told by a famous Parisian physician to ‘Promptly return to Orleans and for any remedy, made use of water of the Loire’. However, the Loire did not escape the degradations from the intense economic development of the 19th century, welldescribed for Britanny (Thibault 1996a, 1996b), which resulted in heavy pollution related to industrial activities (tannery, retting of plant fibres, paper mills, and mining). These activities declined finally at the beginning of the 20th century, resulting in improved water quality before 1950s, followed by further degradation by forms of pollution that appeared as a result of urban growth, intense agriculture, and the development of food industry.

PART | I Rivers of Europe

A study by Des Cilleuls (1928) showed that at the beginning of the 19th century the development of the phytoplankton in the Loire was poor, similar to other free-flowing rivers. Although phosphorus data before the 1980s are lacking to show the beginning of eutrophication, it was evident, already in 1960s, that nutrients inputs had considerably amplified phytoplankton growth. A study of the Loire in 1967 suggested that the river was experiencing eutrophication at that time, and river quality monitoring carried out since 1980 showed that phosphorus concentrations and chlorophyll a levels were very high. If phosphorus concentration and chlorophyll a tend to decrease nowadays, the river still suffers from eutrophication (Lair, 2001). Model simulations of phytoplankton development were used to explain these phenomena and to predict the potential efficiency of phosphorus reductions (Everbecq et al. 2005). Efforts to reduce urban, industrial and agricultural phosphorus inputs are reflected in the reduction in phosphorus concentrations in the river. In addition to this long-term degradation of the physicochemical water quality, the Loire had other problems that contributed to its deterioration. These included the construction of retention structures and migration obstacles for fish, other hydromorphological alterations particularly from hydraulic developments, and the discharge of toxic substances such as pesticides. Pesticides were found at most sampling sites, sometimes in concentrations thought to affect biological diversity. Estimates of the pesticide input from agricultural sources support these findings, although nonagricultural contributions may be also important. The migratory potential the Loire basin for fishes is limited by the distance from the sea as a natural constraint and the frequency of artificial migration obstacles such as dams and habitat degradation. The degree of environmental change can be characterized by the extent of water level regulation by dams. Rivers with low slopes such as the Mayenne, Sarthe and the Loir (Sarthe tributary) and numerous dams have been particularly affected. The cumulated impacts become especially manifest during the spawning season because dams retard migration and enhance mortality via the clogging of sediments. Channel excavation of the Loire disrupted lateral fluvial dynamics and caused an alarming decline in the pike population. Headwater catchments in the Massif central are less impacted because agricultural pressure is still relatively low (Vigneron, 2001, 2002). Some impacts result from the increase in the number of ponds in the Limousin area that are affecting water temperature, dissolved oxygen, and water quality in general, and the permeability of surface bed sediments by clogging. Hydraulic works in the 1970s and 1980s strongly modified the rivers as well, especially in the Massif central where the impacts on fish populations were statistically evident. The rivers in the Maine basin and the central region have also been remarkably transformed to a chain of impoundments. A reduction in river slope caused a simplification of the riverine habitat with a loss of fast-flowing zones and associated fishes such as barbel, common dace

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(Leuciscus leuciscus) and spirlin (Alburnoides bipunctatus). Regardless, the Loire, Allier and lower Vienne still contain a variety of riverine habitats and stretches of free-flowing and braided reaches. The action plan ‘Plan Loire grandeur nature’ initiated in 1976 led, in particular, to the restoration and establishment of fish passes. As mentioned above, a total ban on salmon fishing was implemented in 1994 and two dams were removed in 1998 within the plan framework. A LIFE program (a financial instrument of the European Community supporting environmental and nature conservation projects) initiated the ‘Loire Nature’ in 1992 that aimed to preserve free space along the Loire and Allier. The project focussed on 8 sites that were the most remarkable from an ecological perspective. Special protection zones have been designated within the framework of Natura 2000, an ecological network of the European Community to protect the most threatened habitats and species in the basin. In the context of mammals (Richier 2003), there now exist management plans of habitats for the European beaver and the Eurasian otter, restoration of fish migration pathways in the rivers, and control of non-native nutria and muskrat.

on the reduction of industrial and domestic pollution, and more recently on the control of pollution from diffuse sources, management is now aimed toward the functioning of aquatic environments. The primary goal of the WFD of reaching a good ecological status of aquatic environments in 2015 should enhance the restoration of aquatic environments, and in particular, a focus on river morphology and flow regimes. Much effort has been made to mobilize the public and stakeholders to assist in habitat improvements and assure financial funding. Much debate on the revision of the management and water master plans require the input from the public and stakeholders. Implementing the third phase of the “Plan Loire grandeur nature” will add to this discussion, although improving the ecological status of the Loire basin is the primary goal.

Acknowledgements The authors of the R. Loire chapters are indebted to several people who provided various and useful information for its completion. We wish in particular to acknowledge the inputs or studies from P. Reyes-Marchant, Th. Cornier, A. Beauger, L Maman, and Agence de l’Eau Loire-Bretagne.

5.2.10. CONCLUSIONS AND PERSPECTIVES Bordered by levees since the Middle Age downstream of the Loire/Allier confluence, an incised bed due to sediment extraction since the middle of the 20th century, inputs of pollutants, the Loire nevertheless has numerous reaches with active fluvial dynamics, and the River offers a remarkable biological diversity. This illustrates the capacity of resilience of this exceptional ecosystem. The present high biological diversity results from the large variety of geological and climatic features of the Mediterranean, continental and Atlantic regions. There exist areas such as the Loire/Allier confluence where high habitat diversity parallels that of biodiversity, in particular the high diversity of plants and birds. Although ignored for a long time, aquatic environments have seriously deteriorated due to sediment extraction, and the construction of sills and barrages that deeply modified aquatic habitats and biotic communities. The number of impounded reaches is high in many tributaries of the lower Loire basin, and although few exist in the Loire main stem, all are obstacles to fish migration. Fish populations have been affected by the deepening of the river bed, for example the status of the pike is questionable, and the ecological consequences are visible in the plant communities through accelerated growth of hardwood forests. The lateral dikes along the middle Loire also stabilized channels and islands. The pollution impacts cumulate in the estuarine zone where conditions for fish are poor during certain periods of the year. Now the time has come for sustainable development. While emphasizing the good ecological status of rivers, the Water Framework Directive (WFD) noticeably modified the priorities of European water policy. While once focussed

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PART | I Rivers of Europe

ical and chemical variables in relation to algal biomass. Hydro ecologie Appliqu ee 5: 1–27. Lair, N., Sargos, D., and Reyes-Marchant, P. 1996. Hydrological studies at the level of the Dampierre-en-Burly nuclear power plant in the course of the middle Loire (France). Hydro ecologie Appliqu ee 8: 35–84. Leitao, M., and Lepr^etre, A. 1998. The phytoplankton of the River Loire, France: a typological approach. Verhandlungen des Internationalen Vereins f€ ur Theoretische und Angewandte Limnologie 26: 1050–1056. Leitao, M., and Rouquet, V. 2002. Algal monitoring in the Seine and two tributaries near Paris. Verhandlungen des Internationalen Vereins f€ ur Theoretische und Angewandte Limnologie 28: 892–896. Malavoi, J.R. 2002. Hydrologie et geomorphologie fluviale. La Loire, vallees et vals du grand fleuve sauvage. Delachaux et Niestl e, pp. 11–99. Merceron, M. 2005. Pourquoi le saumon devient rare – une hypothese. Eaux et rivi eres de Bretagne 132: 6–7. Moatar, F., and Gailhard, J. 2006. Water temperature behaviour in the River Loire since 1976 and 1881. Comptes Rendus Geoscience 338: 319–328. Moatar, F., and Meybeck, M. 2005. Compared performances of different algorithms for estimating annual nutrient loads discharged by the eutrophic River Loire. Hydrological Processes 19: 429–444. Oberdorff, T., Pont, D., Hugueny, B., Beliard, J., Thomas, R.B.D., and Porcher, J.-P. 2002. Adaptation et validation d’un indice poisson pour l’evaluation de la qualite biologique des cours d’eau fran¸cais. Bulletin fran¸cais de p^ eche et de pisciculture 365–366: 405–433. Pellieux, J.N. 1786. Extrait d’un memoire sur les proprietes de l’eau en general, et la preference qu’on doit donner a celles de la Loire, sur celle des puits.15 pluviose an XI. Persat, H., and Keith, P. 1997. The geographic distribution of freshwater fishes in France: which are native and which are not ? Bulletin fran¸cais de p^ eche et de pisciculture 344–345: 15–32. Picard, V., and Lair, N. 2005. Spatio-temporal investigations on the planctonic organisms of the Middle Loire (France), during the low water period: biodiversity and community dynamics. Hydrobiologia 551: 69–86. Richier, S. 2003. Le bassin de la Loire et ses mammiferes. Etude pour la structuration d’un reseau de suivi. Note de synthese. ONCFS, Diren Centre, Equipe plan Loire. Roche, J. 1989. Distribution du chevalier guignette Actitis hypoleucos et de l’ombre commun Thymallus thymallus, le long des rivieres de France et d’Europe. Bulletin d’ ecologie 20: 231–236. Roche, J. 1993. The use of historical data in the ecological zonation of rivers: the case of the tern zone. Vie Milieu 43: 27–41. Roche, J., Constant, P., Daurat, B., Desbrosses, R., Eybert, M.C., Faivre, B., Godreau, V., Perret, F., and Frochot, B. 1993. Diversite et valeur patrimoniale des peuplements d’oiseaux nicheurs de la Loire sur l’ensemble du cours. De l’ecologie a la conservation. Universite de Bourgogne/ Ministere de l’environnement, 60 pp. Roche, J., Desbrosses, R., Faivre, B., Guelin, F., Lallemand, J.J., and Frochot, B. 1993. Diversite et valeur patrimoniale des peuplements d’oiseaux nicheurs de l’Allier sur l’ensemble du cours. Universite de Bourgogne/Ministere de l’environnement, 64 pp. Roche, J., and d’Andurain, P. 1995. Ecologie du cincle plongeur Cinclus cinclus et du chevalier guignette Tringa hypoleucos dans les gorges de la Loire et de l’Allier. Alauda 63: 51–66. Rodrigues, S., Breheret, J.G., Macaire, J.J., Moatar, F., Nistoran, D., and Juge, P. 2006. Flow and sediment dynamics in the vegetated secondary channels of an anabranching river: The Loire River (France). Sedimentary Geology 186: 89–109. Souchon, Y. 2002. Milieux aquatiques et poissons. La Loire, vallees et vals du grand fleuve sauvage. Delachaux et Niestl e, pp. 201–223. Steinbach, P. 2002. La Loire vue par les poisons. CSP Revue 303(75): 338–343.

Chapter | 5.2 The Loire Basin

Steinbach, P. 2005 - Contexte migratoire du bassin de la Loire - Rapport d’expertise de l’axe Loire-Allier et des conditions de migration des saumons. Delegation inter-regionale de l’ONEMA, Centre PoitouCharentes, Orleans, 46 pp. Tachet, H., Morse, J.C., and Berly, A. 2001. The larva and pupa of Pseudoneureclipsis lusitanicus Malicky, 1980 (Trichoptera: Hydropsychoidea): description, ecological data and taxonomical considerations. Aquatic Insects 23: 93–106. Thibault, M. 1996a. Ecohistoire du saumon atlantique (Salmo salar L.) en Bretagne. Institut National de la recherche agronomique. Thibault, M. 1996b. Le saumon atlantique entre methode experimentale et opinion. Penn ar Bed 163: 1–12.

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Thibault, M. 2001. Ecohistoire du saumon dans les bassins Loire et Allier – Association pour la promotion, l’etude et la protection des ecosystemes aquatiques de la Bretagne et des pays de la Loire. Verneaux, J. 1973. Cours d’eau de Franche-Comte (massif du Jura). Recherches ecologiques sur le bassin hydrographique du Doubs, essai de biotypologie. These universite de Besan¸con. 260 pp. Vigneron, T. 2001 et 2002. Reseau hydrobiologique et piscicole Loire Bretagne. Synthese des donnees 1999 et synthese des donnees 2000 – CSP. Wasson, J.G., Chandesris, A., Pella, H., and Blanc, L. 2004. Les Hydro-e coregions: une approche fonctionnelle de la typologie des rivieres pour la Directive Cadre Europeenne sur l’Eau. Ingenieries. Eau Agriculture Territoires 40: 3–10.

Chapter 5.3

The Adour–Garonne Basin Alain Dauta

R egis Cereghino

Alexandra Coynel

ECOLAB, Laboratoire d’ ecologie fonctionnelle, UMR 5245 (CNRS-UPSINPT), 29 rue Jeanne Marvig, 31055 Toulouse 4, France

ECOLAB, Laboratoire d’ ecologie fonctionnelle, UMR 5245 (CNRS-UPSINPT), 29 rue Jeanne Marvig, 31055 Toulouse 4, France

UMR-EPOC-5805, Universit e Bordeaux I, Avenue des facult es, 33405 Talence, France

Francis Dauba

Fran¸cois Delmas

Alain Dutartre

ECOLAB, Laboratoire d’ ecologie fonctionnelle, UMR 5245 (CNRS-UPSINPT), 29 rue Jeanne Marvig, 31055 Toulouse 4, France

Cemagref/Groupement de Bordeaux, 50, Avenue de Verdun, 33612 Cestas, France

Cemagref/Groupement de Bordeaux, 50, Avenue de Verdun, 33612 Cestas, France

Henri Etcheber

Paul Gonthier

Jean Joachim

UMR-EPOC-5805, Universit e Bordeaux I, Avenue des facult es, 33405 Talence, France

Cemagref/Groupement de Bordeaux, 50, Avenue de Verdun, 33612 Cestas, France

Institut National de la Recherche Agronomique – Comportement & Ecologie de la Faune Sauvage, Chemin de Borde Rouge, BP 52627, 31326 Castanet Tolosan, France

Puy Lim

Anne Probst

-Miguel Sanchez-Pe rez Jose

ECOLAB, Laboratoire d’ ecologie fonctionnelle, UMR 5245 (CNRS-UPSINPT), 29 rue Jeanne Marvig, 31055 Toulouse 4, France

ECOLAB, Laboratoire d’ ecologie fonctionnelle, UMR 5245 (CNRS-UPSINPT), 29 rue Jeanne Marvig, 31055 Toulouse 4, France

ECOLAB, Laboratoire d’ ecologie fonctionnelle, UMR 5245 (CNRS-UPSINPT), Avenue de l’Agrobiopole 31326 Castanet Tolosan, France

Sabine Sauvage

Fran¸cois Simonet

Eric Tabacchi

ECOLAB, Laboratoire d’ ecologie fonctionnelle, UMR 5245 (CNRS-UPSINPT), Avenue de l’Agrobiopole 31326 Castanet Tolosan, France

Agence de l’Eau Adour–Garonne, 90 rue du F er etra, 31078 Toulouse 4, France

ECOLAB, Laboratoire d’ ecologie fonctionnelle, UMR 5245 (CNRS-UPSINPT), 29 rue Jeanne Marvig, 31055 Toulouse 4, France

Philippe Vervier ECOLAB, Laboratoire d’ ecologie fonctionnelle, UMR 5245 (CNRS-UPSINPT), 29 rue Jeanne Marvig, 31055 Toulouse 4, France

5.3.1. INTRODUCTION The Adour–Garonne catchment covers 20% of the French territory (107 000 km2). Delimited by the Armorican, Central and Pyrenean Massif, it is largely open to the Atlantic coast. The catchment comprises the river networks of the Adour, Garonne, Dordogne and Charente as well as the coastal rivers Charentais and Aquitains (Figure 5.1a). Relatively low in terms of population size, it is home to about 10% of the French population at a density of 57 inhabitants/ Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

km2. It has two large cities (Toulouse and Bordeaux) with over 900 000 inhabitants each and three cities (Pau, Bayonne and Angoul^eme) with over 100 000 inhabitants. The Toulouse–Bordeaux axis is a major communication link between the Atlantic and the Mediterranean Sea, representing an economic corridor even before the Roman period. The catchment has a strong agricultural foundation, with major water needs for irrigation (40% of the total French irrigation needs). The fishery in the catchment has high economic value for both professional and recreational fishermen. The 182

Chapter | 5.3 The Adour–Garonne Basin

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PHOTO 5.7 The largest Pyrenean river Adour in the plain at Aire (Photo: Agence de l’Eau Adour-Garonne).

heterogeneity of the landscape, along with its coastal placement and nice rivers (e.g. Dordogne, Lot, Tarn), attracts many tourists. Many dams and reservoirs along with smaller man-made ponds have been constructed. The basin includes many groundwater drainages derived from alluvial karstic sources and deeply confined aquifers, which are a major source of drinking water. The Garonne is the major river in the basin and is the third largest French river. This chapter mainly discusses the Garonne with other examples from the rivers Adour, Charente and Dordogne.

5.3.1.1. Major Rivers and Tributaries The catchment drains through large valleys and a dense river network (>1.2 km/km2). The Garonne and Adour drain from the Pyrenees, and the Tarn, Lot, Dordogne and Charente originate from the Massif Central. The Garonne and its two major tributaries (Tarn, Lot) drain 50% of the catchment. The Adour is considered the largest Pyrenean river flowing through the plain to the Atlantic (Photo 5.7). The Adour derives 90% of its water from the western and central Pyrenees. Its flow doubles after it merges with the Gaves Reunis about 50 km upstream of its mouth. Initially running parallel with the sand dunes along the coast, its mouth has moved over 50 km south since the 15th century. The Charente is the smallest catchment of the Adour– Garonne basin and is characterized by a low altitude and flat topography. This relatively homogenous catchment lies between the Garonne and Loire basins. The alluvial aquifer in the catchment is shallow and responds quickly to rain events. Although there are two reservoirs along the river network, the characteristics of the catchment make the fluvial hydrosystem quite vulnerable to changes in water inputs.

The Dordogne headwaters consist of a dense stream network originating from the eruptive and crystalline formations of the Auvergne and Limousin, which then changes to tertiary sands as the river crosses the Causses du Quercy and Perigord (Photo 5.8). The Dordogne then flows through a calcareous valley about 3.5 km wide that contrasts with the 300–400 m wide upstream section. Further downriver, the channel has been altered by various geological and anthropogenic factors. A limestone thrust and volcanic massifs increased the river slope, causing quarternary glacial and fluvial erosion. Various glacial advances and retreats, along with changes in sea level, have modified the Dordogne profile over time, as evidenced by different aged terraces along the river. During interglacial periods, several meters of sediment were deposited over the middle and lower Dordogne plain. Originating in Spain, the Garonne first flows north before turning northwest to form the Aquitain basin (Photo 5.9). The Garonne drainage network is asymmetric (Figure 5.1b). The rivers Salat, Arize and Ariege flow from the Pyrenees Ariegeoises, and the Tarn and Lot Rivers are the major rightbank tributaries flowing parallel from the Central Massif with similar catchment areas (Tarn: 375 km long, catchment area 15 500 km2, Lot: 491 km long, catchment area 12 500 km2; Figure 5.9). From the left bank, the Garonne collects waters from the rivers of the Gascogne area (7390 km2), in particular the rivers Baise, Gers, Gimone and Save. The east–west oriented Lot basin has two major sub-catchments. The upper basin drained by the rivers Truyere and Lot has a pronounced gradient and dense drainage network. Further downstream, slopes are reduced and the drainage network is diffuse. The Tarn basin has three hydrographic sub-catchments: the Tarn (length 375 km, area 6700 km2), the Aveyron (length 292 km, area 5300 km2),

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PHOTO 5.8 Castle of Beynac (Perigord) on the river Dordogne (Photo: Alain Dauta).

and the Agout (length 193 km, area 3500 km2). Beginning in the Quaternary, the river has carved a canyon through the calcareous massif of the Grands Causses. The Tarn flows over the molassic plain upstream of Albi, where in the lower valley it merges with the Agout and with the Aveyron and at the end of the catchment.

The coastal rivers comprise 8% of the Adour–Garonne basin. The two most important coastal rivers are the Leyre and Seudre. The Leyre is 80 km long with a catchment area of 1700 km2 in the core of the Landes de Gascogne. It flows into the Arcachon lagoon with a mean annual discharge of 20.8 m3/s. Unconfined groundwater flows out of Pliocene

PHOTO 5.9 The river Garonne in Toulouse at the dam of Bazacles (Photo: Alain Dauta).

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Chapter | 5.3 The Adour–Garonne Basin

Distance from mouth (km)

400 Salat

300 Ariège 200

Tarn 100

Lot

0 0

2.5

5.0

7.5

10.0

12.5

15.0

17.5

Annual discharge (km3/yr) FIGURE 5.9 Longitudinal development of mean discharge along the Garonne River.

sands, and floods in the river are quite moderate (maximum flow of 150 m3/s) and slow because of the low gradient (maximum elevation in the watershed is 72 m). The river Seudre (source at St. Genis at 39 m asl) flows for 69 km before entering a large estuary used for shellfish farming (Marennes–Oleron oysters).

5.3.2. HISTORICAL PERSPECTIVE The first humans made use of the banks of the Dordogne and its major tributaries, Isle and Vezere, several hundred-thousand years ago. Part of the Vezere valley, encompassing the Lascaux and Eyzies plateaus, has been registered as a UNESCO site for human heritage. These plateaus, the Perigord valley, and the neighboring villages are important prehistoric sites that attracted tribes of Paleolithic hunters. During cold periods, these valleys were protected from icy winds, the calcareous cliffs were warmed by the sun, and the caves were inhabited by humans and game. The first humans in the lower Paleolithic that left traces in the Perigord were there before the Riss glaciation, 400 000–500 000 years ago. Numerous human traces in the middle (80 000–35 000 years BC) and younger (35 000–10 000 years BC) Paleolithic period are found in the Eyzies (Neanderthal man) and Lascaux (Cro-Magnon man) caves. Cro-Magnon man inhabited the Aquitain watershed. The Venus of Brassempouy statue, sculpted 23 000 years ago in mammoth ivory, is the oldest representation in the world of a human face. The upper Charente and its tributaries show much human evidence from the upper Paleolithic (Magdalenien, Solutreen) and Bronze Age. Paleolithic tribes (35 000– 10 000 BC) preceded the Mesolithic people of the Aziliens (10 000–7000 BC). After the Magdalenien (12 000 BC), the population increased, as attested by the large number of listed places, and humans fully used the river and its floodplain. After the Mesolithicum, an elementary agriculture appeared along with livestock production. The estimated human population of 10–20 000 inhabitants in the Mesolithic increased to 100–200 000 by the end of the Neolithicum.

The end of the Bronze Age is marked by cultural contributions from North Europe and the Mediterranean. In the 6–7th century BC, a wave of Hallstattiens people entered the basin and inhabited the south of Garonne. The riverbanks of the Garonne were used for agriculture, and wheat was cultivated around 4000 years BC. The Garonne also played a part in the tin route during the Bronze Age (1800–800 BC), which followed the Aquitainian isthmus to Marseille and Italy. Additional immigrants came with the Iron Age (750 years BC). In the 3rd century BC, natives from Franconia reached the rivers of the Garonne basin between 215–200 BC and occupied Toulouse. The Romans occupied Toulouse in 109–102 BC, and the city became a commercial crossroad in the 1st century BC. The city of Bordeaux was founded in the 3rd century BC by celtics, and its location on the estuary of the Gironde allowed control of tin transit from Britain. In the beginning of the 3rd century BC, celtic Petrocoriens settled near Vesone (Perigueux), leaving traces in the middle valley. After the Roman campaign 56–52 years BC, the Petrocoriens and Cadurques joined with Vercingetorix against the Romans but were later defeated and placed under Roman rule with a new political and social order. The vineyards from the Bordeaux region are a Gallo– Roman creation in the first century. The Roman period lead to the foundation of two main cities on the Charente: Saintes and Angoul^eme. The Gallo–Roman civilization assured a long period of prosperity until the invasions by the Francs and Alemans in 276 AD, Germanic tribes in 406 AD, and Visigoths in 408. In the 6th century, many villages of the Dordogne came under Francs authority. During the late 9th century, the Vikings launched many expeditions into the area. In the 12th century, the wars ended and the middle and lower Dordogne became major population areas. Economical development included an increase in the number of ports, bridges, and mills, and an enhanced fishery. Five rivers (Adour, Charente, Dordogne, Garonne, and Lot) constitute the axis around which life, transport, commerce and the first industries were organized. For example, at the end of the 12th century there were 60 permanent mills in operation in Toulouse. The Charente River, already navigable in the Iron Age, served for the transport of salt. The oldest harbours (Cognac, Jarnac) were operational in the Gallo–Roman period. The Adour River also was known from the Middle Ages as a major transport route for barges that brought products from the inner South–West to the Aquitaine. The hundred year war (ca. 1350–1450 AD) destroyed the economy of the Aquitaine, but after 1460 an economic renewal began. For three centuries, these rivers were major trade routes and sites for industry and manufacturing (black smith, oil and wheat mills, and after 1530 paper production). Two cities were of major importance in the 16th century: Bergerac (population 5000–7000) and Sarlat. River engineering on the Charente permitted navigation up to Angoul^eme in the 15th century, and river regulation intensified in the 17th century. At the end of the 19th century,

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shipping on these rivers essentially disappeared due to the development of national roads, railroads, and a lower population size. The first dams for electrical production appeared in the beginning of the 20th century; for example on the Dordogne River were built the dams of Tuiliere (1906), Mauzac (1918), Mareges and l’Aigle (1930–1945).

5.3.3. BIOGEOGRAPHIC SETTING 5.3.3.1. General Aspects The Adour–Garonne basin lies within the Aquitain catchment, being bordered by the Pyrenees in the south and the Central Massif in the east. Its diverse relief progressively climbs from the Atlantic coast at <50 m asl to hillside molasses with an average altitude of 30–50 m asl in the central part. Then a calcareous plateau at 300–500 m asl occurs, culminating near 1900 m asl in the east at Puy de Sancy and >3000 m asl in the Pyrenees. The ecological, orographic and climatic characteristics of the catchment reflect 9 hydro-ecoregions.

5.3.3.2. Paleogeography The Aquitain fossil catchment is a triangular-shaped sedimentary area bordered by the Massif Central and the Pyrenees. The high diversity of accumulated bed materials and soils, tectonic activities, and erosional processes caused a highly diverse landscape and conditions for human settlements. The landscape of the Garonne consists of plateaus, hills and valleys, particularly large valleys in the Middle Aquitaine. Fringed by the Pyrenees in the south, the Aquitaine landscape connects the Loire valley through the Poitou with the Mediterranean area through the Lauragais. It has an extended border with the Atlantic Ocean. In the north, the Massif Central inclines to the south where it forms the base of the shallow Aquitaine depression. In the south, the uplifted Pyrenean base is subject to active erosion that provides debris to the depression. From the Pyrenees to the latitude of Arcachon, the Triassic base has subsided and carbonate salts have accumulated. These tectonic contrasts between the north and south became more pronounced during the Mesozoic and Tertiary. In the North, the depressed margins became filled with marine, lacustrine and continental material. In the south, grabens became deeper or were partly filled with sediments. The uplift of the Pyrenees started in the Lutetien, bending and fragmenting the Mesozoic and Tertiary terrain of the foreland. By the end of the Tertiary, the Aquitain catchment was essentially formed. On the Perigord and Charente plateaus, like on the Pyrenean Piedmont and on the Landes plain between Garonne and Adour, vast aquifers occurred that etched the landscape and larger valleys. Waters from the Central Massif and Pyrenees drained into the Garonne.

PART | I Rivers of Europe

The Pyrenean foreland and the Adour area are characterized by deposition of glacier debris that accumulated in the foreland valleys. In the west, the Basque country and Bearn are the domain of Flysch (Cretaceous and Eocene) composed of a sequence of thin alternately hard (sandstone and calcareous rock) and soft (schistose clay) strata. From the east to the west, lakes near the sea became subsequently filled. The most depressed areas, for example the present Bordelais, remained inundated until the Quaternary. During the Villafranchien (Tertiary/Quaternary boundary), the climate of the Aquitain was relatively warm and arid, with periods of short but extreme precipitation events. These erosion events formed the deep valleys in the Perigord plateau and Pyrenees that ultimately produced the large alluvial fans along the Pyrenees northern front. After the Villafranchien, glaciation cycles affected Western Europe and a cold steppe or tundra vegetation became established. On the Landes plain, stormy winds resulted in scattered vegetation and moved large volumes of marine sands eastwards.

5.3.4. PHYSIOGRAPHY, CLIMATE AND LAND USE 5.3.4.1. Landforms, Geology The diverse relief of the Garonne extends from south to north incorporating such areas as the high Pyrenean glacial valleys and the Piedmont (500–>2000 m asl), hilly zones dominated by the Lannemezan Plateau (>1000 m asl), a Piedmont zone with cliffs and asymmetrical terraces (100–300 m asl), molasse hills (Aquitain hillside) that extend into the middle catchment and large floodplains downstream, and ‘sea’ zones near the estuary and the Bordeaux heaths. This scheme is similarly repeated in the Lot and Dordogne basins. These basins have an upstream zone with strong relief (average altitude >700 m asl) that includes mountains and incised valleys, followed by plateaus (Grands Causses, Causses Calcaires) rich in karstic systems, and then molasse and clay soils at relatively low altitude. The Tarn basin has three geological sectors, including an upstream section where the rivers cut deep canyons in the rocky calcareous tables of the Grand Causses plateaus (karstic zone), a middle section in the schistose and granite plateaus of the Central Massif, and a downstream section in the hillside molasse of the Aquitain catchment. The Dordogne basin includes four geological groups running east to west. In the north occur the crystalline plateaus of the South Limousin with low gradients dominated by impermeable granitic rocks. The hilly landscape is covered by degraded heaths and forests. The eastern part has landscape elements formed by volcanic and glacial activities and is strongly modified by erosion that created confined valleys, lakes and cirques, eroded hillsides and relatively moderate slopes. In the middle part occur karstic zones of the calcareous Causses plateau where upstream reaches have

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Chapter | 5.3 The Adour–Garonne Basin

deeply embanked valleys. Downstream, the valley expands laterally and the river has large meanders. The calcareous plateaus are covered by siliceous deposits and vegetated by oak and chestnut forests. The surface drainage system is poorly developed in contrast to the karstic drainage. In the lower section occurs the molasse hillside of the Aquitain basin where the few carbonic rocks prone to erosion have resulted in a more gentle relief. The Charente drains a sedimentary basin with a low altitudes and gentle topography (ca. 100–200 m asl). Large parts of the basin are composed of lands with thin strata of modified calcareous clay formations. The Adour catchment has three typical alluvial terraces separated by steep banks, often with rocky outcrops. Upstream, a synclinal at the fringe of the Pyrenees allowed the development of a deep aquifer (>30 m). The Adour tributaries emerge from debris cones that radiate from the Villafranchien Piedmont. These relatively dry valleys have an asymmetric profile with a gentle western hillside that has been subject to frost and snow action, and a steep eastern hillside. The Adour finally flows through a large 5–10 km wide plain of minor topographic contrast, excavated by glacial meltwaters and filled with sediments during the Riss and W€ urmian alluvial periods. These deposits are generally stony but also include layers of sand, silt, and clay.

5.3.4.2. Climate The Pyrenees and Massif Central are primary barriers encountered by atmospheric fronts coming from the Atlantic Ocean. The overall catchment has an oceanic dominated climate, mild and humid with some continental influence in the east. A Sub-mediterranean climate influence is drained through the Naurouse Pass, between the Montagne Noire and Pyrenees highlands in the southeast. Precipitation is significant near the ocean, being particularly pronounced in the Basque country (West), and in the southeast (>1400 mm/ year). It is low in the central area (600–700 mm/year), being the lowest in the Gascogne basin. Each basin in the catchment has its own climatic features. The climate of the Garonne drainage is principally oceanic, but the plains are subject to a Mediterranean influence with dry winds and lower precipitation. Humidity in the south is influenced by the Pyrenees (1500 mm/year), whereas the Gascogne area is relatively dry. Precipitation in the Lot basin averages 930 mm/yr, partly originating from the Mediterranean upstream. Precipitation of oceanic origin affects the entire watershed throughout the year, with a slight maximum in winter. In the Tarn basin, the oceanic influence is dominant with marked winter and spring rains (annual mean 760 mm/year). West winds prevail particularly in the north and temperatures are moderate (annual average = 13 C). The influence of mountains in the east is reflected by high precipitation (1410 mm/year) and lower temperatures (9.5 C).

The climate of the Dordogne basin is influenced by the ocean with moderate precipitation in the west (600–800 mm/ year) that increases towards the Massif Central. In the middle area, precipitation ranges 800 from 1200 mm/year and can exceed 2000 mm/year in the east. The Charente basin has a moderate climate with precipitation averaging 600–700 mm/ year along the coast and 900 mm/year in the east. In the Adour basin, the Pyrenean range enhances precipitation from the ocean. Average precipitation in the entire basin is near 1300 mm/year. Stream flow is controlled by precipitation and snowmelt in spring, drought in summer, and rains in autumn. The pluvial regime is influenced by the barrier of the Pyrenees with average precipitation ranging from 700 mm/year in the north to 1400 mm/year in the south.

5.3.4.3. Land Use Patterns Land use can be classified into three categories: urban and industrial zones (1.8%), forests and near-natural environments (38.6%), and agricultural lands (59.6%). Agriculture is the main activity in the Garonne valley. Stockbreeding associated with corn and sunflower production prevails in the upper valley. Cereal grains are grown upstream from Toulouse, fruits and vegetables in middle Garonne, orchards and greenhouse cultures in Agenais, and horticulture around cities. Prestigious wine-growing areas are found in the Bordeaux region, such as Ch^ateau Petrus (Pomerol), Ch^ateau Yquem (Sauternes), Medoc, Margaux, Mouton Rothschild (Pauillac), St-Estephe and St-Emilion. The Tarn basin is predominantly rural. Stockbreeding occurs in the arid zones of Grands Causses (sheep, cattle, milk, Roquefort cheese). Grain, which requires irrigation, is grown in the plain. The Gaillac vineyards are situated on the moraine hills. Agriculture occurs on 42% of the basin. Farmland covers 56% of the Lot basin. The upper watershed (80% is permanent grassland) is dominated by extensive stockbreeding (sheep and cattle). Cahors are situated on the Lot hillside. The lower valley is a polycultural zone, where the main products are grains (maize, oilseeds), specialized produce (melons, strawberries, tomatoes, tobacco), and arboriculture. The Dordogne basin has a dominant rural component. This basin is characterized by small farms and a highly diverse agriculture of grains, oilseed, vegetables, stockbreeding and wine. Agricultural lands represent 40% of the basin, and forestry is an important activity. The internal part of the Charente basin is rural, and the Charentais wine growing region (Cognac) represents 17% of the basin. Sugar beet production has been progressively abandoned in favour of more interesting crops like maize and oilseed. The water requirement for these news crops is higher and has led to a 20-fold increase in irrigation between 1970 and 2000. In the upper mountain part (25% of the basin area) of the Adour basin, human activities are concentrated in the valleys (stockbreeding, tourism). The agricultural industry is well

188

represented in the region (37% of all activities) and includes maize, vinyards and stockbreeding: ‘Foie gras’ industries, cheese and dairy, Armagnac distilleries and wineries. Forestry is an important activity and has promoted the implementation of wood transformation industries. Because of large beaches, lakes and forests, the main activity in the coastland area is tourism. Agriculture mainly consists of: stockbreeding (sheep, cattle, geese, ducks), viticulture in the Bordeaux wine area (Medoc, Graves, Blayais, Libournais, Entre-deux-mers), the Cognac production region, the Pineau Charente maritime, and forestry. The Aquitain forest is the third largest forest in France.

5.3.5. GEOMORPHOLOGY, HYDROLOGY AND BIOCHEMISTRY 5.3.5.1. Geomorphic Development of the Main Corridor The French course of the Garonne has many features that reflect erosional dynamics and human activities. From the headwaters to the ocean, the form of the Garonne riverbed changes as a function of hydrodynamic and geomorphological conditions. A substantial part of the Garonne course is characterized by relatively steep gradients. In the upper basin, the river slope is 7 m/km, decreasing to 2 m/km at Montrejeau, and slightly increasing (3.5 m/km) in the Piedmont until the Salat confluence. This is the section with the highest hydroelectric potential. The slope gradually decreases to 1 m/km at Toulouse and 0.7 m/km at the Tarn confluence. The river follows a sequence of deep reaches separated by fast shallow reaches. Valleys, especially those of the central Aquitain, are noteworthy because of the extensive river terraces. In the Pyrenean Piedmont area, the large valleys largely reflect fluvio–glacial influences. After the end of the glaciations, torrents and braided rivers transported enormous volumes of sediments that were deposited in the Piedmont area where the rivers and streams formed large alluvial plains. This kind of valley can be found at the level of the Adour tributaries. Valleys originating from the Massif Central are deeply incised in the Perigord and Charente plateau. In the centre of the Aquitain catchment, the rivers Garonne, Lot and Dordogne laterally expand and form extensive river terraces. The Garonne valley after the Toulouse plain expanded in the molasse, narrowing across the hard calcareous Agenais area, and expanding again in the Marmandais molasses where four terrace levels can be distinguished. In the upper Garonne where the river flows from the Pyrenees, the bed is deeply incised with pebble and molasse deposits originating from the erosion of the Pyrenees (‘molasses d’aquitaine’ and ‘molasses stampiennes’). These sediments were deposited mostly during the Oligocene (Battiau-Queney 1993). The molasses are sediment formations deposited in an orogenic zone at the end of tectonic

PART | I Rivers of Europe

transformations, and typically in discordance with underlying strata (Foucault & Raoult 1988). The river between Toulouse and the Tarn confluence is a geomorphologic transition zone. Here the slope is >1% and the river is confined by the W€urmian terrasses with a relatively narrow floodplain. With the confluence of the Tarn, the catchment size doubles and the slope decreases to <0.5%. Today, the Garonne, particularly in its middle course, exhibits a morphodynamic dysfunction characterized by an unbalanced state largely caused by human activities (Beaudelin 1989; Steiger et al. 1998, 2000). Before the minor riverbed regulation occurred, the Garonne had a dynamic active channel characterized by highly mobile meanders (Lambert 1989; Decamps et al. 1989). In the section between Toulouse and the Tarn confluence, programs to stabilize the riverbed became effective in the late 1950s, following the aftermath of the large flood of February 1952. The riverbed has been laterally stabilized by rip–rap in river bends and meander concavities, and in some sections with dikes. Meander cutting increased the slope and caused degradation of the channel. While significant dredging of the channel accelerated the exposition of resistant molassique banks, the supply of coarse sediment declined because of several dams and reservoirs upstream of Toulouse.

5.3.5.2. Sediment Load The Garonne and tributaries are representative for most southwest French rivers. The production of alluvial sediments is estimated to be about 32 million tons/year (7.5% of the French production) (Steiger et al. 2001; Steiger & Gurnell 2003). The transport of suspended material shows a distinct interannual variability, correlating with the annual hydrological regime. The specific sediment yield of the Garonne at la Reole (about 40 km upstream of Bordeaux) varies considerably between 11 and 70 tons/km2/yr depending on whether the year is dry (annual discharge 300 m3/s) or wet (annual discharge 850 m3/s) (Coynel 2005). The Garonne has a high sediment yield compared with the Adour (22– 61 tons/km2/year), Charente (5–15 tons/km2/year), Loire (10–20 tons/km2 year), and Seine (5–10 tons/km2/year). Most sediment transport occurs during floods. For example, the Pyrenean rivers contribute >80% of the years sediment balance in <10 days during high flows (Maneux et al. 1999). The sediment yield at the outlet of a catchment integrates the yield of the entire catchment, but preferential sediment output zones exist (Table 5.4). Among the principal tributaries (Tarn, Aveyron, Gascogne and Lot), the Tarn sediment yields are much higher than those of the others. The specific sediment yield of the Tarn tributary Dourdou equals 130 tons/km2/year. However, its sediment yield is low until it passes an area of a particular Permian lithology (corresponding to the ‘Rougiers de Camares’) where the sediment yield increases to 310 tons/km2/year (Coynel 2005). At the regional scale of southwest France, the spatial variation in

189

Chapter | 5.3 The Adour–Garonne Basin

TABLE 5.4 Sediment flux and sediment yield in selected catchments of the Adour–Garonne basin Watershed

Station

Area (km2)

Mean annual discharge (m3/s)

Sediment flux (103 tons/year)

Sediment yield (tons/km2/year)

Upper Garonne Tarn Dourdou Aveyron Baise Lot Lower Garonne Dordogne Adour Gaves

Castelsarrasin Montauban Saint Affrique Montauban Nerac Temple La Reole Pessac/Dordogne Port de Lanne Peyrehorade

13 730 9100 350 5170 1330 9170 51 500 1500 8000 5030

199 150 12 58 12 145 615 279 108 184

500 1200 46 98 87 475 1870 380 260 300

36 130 130 19 66 45 35 26 33 54

sediment yield correlates positively with the specific annual flows (L/s/km2) and the drainage coefficient of local lithology, and inversely with the soil protection index that depends on vegetation cover. The sediment yield will be generally higher following a dry year (Sch€afer et al. 2002). Flow management can also have a major impact on sediment yields. For instance, during a 50-year flood in the Lot in December 2003, about 43% of the total sediment yield (4 35 000 t) originated from transiently stored sediments that were mobilized when the floodgates of several dams had to be opened.

5.3.5.3. Hydrology The flow regime of the Garonne is highly variable (Figure 5.10). Flow variations in the river and its tributaries are high and include periodic fluctuations (annual, monthly, daily) depending on the size and features of the basins. Low flows are 4–5 times less than the annual average flow, equalling 609 m3/s at the lower gauging station. During floods, flow can increase 10–50-fold. Annually, the flow regime has an alternating period of low flow (winter and summer) and a period with strong flow with the presence of spring and autumn floods. Low flows occur regularly in winter and summer, most notably in summer because of the influence

Discharge (m3/s)

3000

2000

1000

0 1925

1950

1975

2000

FIGURE 5.10 Monthly discharge of the Garonne River at Tonneins (1913–2006). Data belong to DIREN (French Environmental Regional Agency).

of agricultural water use. Periods of high flows are more unpredictable from year to year and strongly depend on snowmelt. The Pyrenees influence flow patterns in the Garonne upstream of Toulouse. The nival flow regime is characterized by a winter flow minimum (snow as transient water storage) and a flow maximum during spring because of snowmelt and high precipitation. Glaciers within the watershed are small and have little influence on the flow regime. Between Plan d’Arem (Pont du Roy) and Valentine, the regime shifts from nival to nivo–pluvial, and in the piedmont region from a nivo–pluvial to a pluvio–nival regime. With distance from the Pyrenees, the influence of the oceanic climate becomes stronger (Lambert 1989). May is the month with the highest flows due to high precipitation. Because of low precipitation and high evapotranspiration rates, August and October typically have the lowest flow. Three flood types can be distinguished in the Garonne catchment. They include oceanic floods called ‘Pyrenean’ which are the most violent floods that impact the entire water course. These floods have a maximal frequency and magnitude during May–June. Oceanic floods, called ‘classic’: mostly occur between December and March. They are maximum in the west and southwest of the Massif Central, whereas the stage-height of the upper Garonne only weakly increases. Flooding typically begins at the Tarn confluence and increases further by the Lot River. Mediterranean floods caused by torrential showers that in autumn affect the western hillside of the Massif Central. Downpours also can occur on the upper Lot and Tarn basins. In June, atmospheric dryness prevails in the upper Garonne (upstream of the Tarn confluence), causing low flows in summer of <30 m3/s. The lowest flow recorded in Toulouse was 17.1 m3/s (18 July 1989). An accentuation of low flows is apparently related to surface and groundwater abstraction in the past decades. Low flows are less pronounced in winter than in summer. Simulations with a hydro-meteorological model (based on the SIM model: Habets et al. 1999; Etchevers 2000; Boe 2007), provided for the period 2020–2050 in the Garonne

190

5.3.5.4. Biogeochemistry In general, the water quality is high in rivers and streams of the mountain regions of the Pyrenees and Massif Central, but low in regions with high population density or with intensive agriculture. Domestic pollution is from 6 700 000 permanent and 3 000 000 seasonal inhabitants in the catchment. Simulations made by INSEE indicate an increase of 1 000 000 inhabitants in 2025 on the Garonne axis. Industrial wastes before purification are equivalent to 8 700 000 inhabitants (BOD5). About 1000 tons organic matter, 127 tons nitrogen, 31 tons phosphorus, 12 tons toxins, and 9 tons metals are generated every day by domestic and industrial activities. Agriculture (160 000 farms), responsible for diffuse nitrogen and phytosanitary pollution, uses 50% of the catchment surface. As a consequence of large cities and industrial sites, the Garonne and Adour catchments have the highest inputs of organic matter, while the Charente and Lot basins seem to be less affected. The pollution zones correspond to the most important agglomerations, those of the main agro-industrial zones (Cantal dairies, Lot and Garonne canneries, Bordeaux wine cellars, Charente and Gascony distilleries), paper industries (Adour, Garonne), and leather industries (Tarn).

5.3.5.5. Nitrogen and Phosphorus At the scale of the Garonne catchment, contamination from nitrate ranks before pollution from organic matter as a major factor limiting water quality (AEAG 2005). The most effected basins with 25–50 mg NO3/L are the Charente, Adour, the littoral rivers, and the majority of the Gasconne tributaries of the Garonne. Long-term records (1976–2006) show high variation in nitrate, ammonium, and phosphorus concentrations downstream of Toulouse. Data collected by the Agence de l’Eau Adour Garonne at 24 stations along the river during this period revealed no significant interannual variability in nitrate, ammonium and phosphorus concentrations. The influence of Toulouse (900 000 inhabitants) on nitrogen and phosphorus concentrations is obvious. Nitrate concentration increases from 1.3 mg NO3/L at the beginning of the watershed to a maximum of 12.7 mg NO3/L 50 km downstream of the city (Figure 5.11). Ammonium concentrations (0.13 mg NH4/L upstream) strongly increase after

10.0

1.25 Nitrate Ammonium

1.00

7.5

0.75

5.0

0.50

2.5

0.25

0.0 500

0.00 400

300

200

100

Ammonium (mg NH4/L)

12.5

Nitrate (mg NO3/L)

catchment estimated a scenario characterized by 25 10% decrease in low water flow, an approximate increase in monthly temperatures by 2 C in winter and 4 C in summer, increase in winter precipitation by 15%, and a decrease in summer precipitation by 20%. Precipitation and snow cover will also be highly affected, that is a nearly 50% reduction in snow depth and duration of snow cover until the end of this century. This will result in a reduction in the spring flow peak and the summer low flow period will begin one month earlier than today. The overall evaluation suggests a general decrease in flow during all seasons.

PART | I Rivers of Europe

0

Distance from mouth (km) FIGURE 5.11 Longitudinal change of nitrate and ammonium concentrations along the Garonne River. Data belong to National Network from Adour-Garonne Basin.

passing the city (1.31 mg NH4/L), but rapidly decline downstream to 0.18 mg NH4/L at the end of the catchment (Figure 5.11). Phosphate concentrations show a gradual increase between 0.06 mg PO4/L in the upstream part of the catchment to 0.5 mg PO4/L until 30 km downstream of the city and a moderate decline toward the end of the catchment (0.44 mg PO4/L).

5.3.5.6. Metals and Pesticides As a whole, waters are considered of good quality for rivers located in the mountainous areas (Pyrenees, Massif Central), whereas quality of waters is worst in the areas of high population density and agricultural activities. At the catchment scale, as an indication, toxic wastes produced by small and medium businesses represent around 70 000 tons/year. Concentrations of dissolved metals in the upper and middle Garonne and its tributaries impose no problems with respect to drinking water quality. Metals in the river network are of natural origin or linked to human activities such as mining, tanning, surface treatments and others diffuse pollutant sources (Loubet et al. 2003). Mining sites of lead, zinc and copper are numerous in the upper parts of the Lot, Tarn, Garonne, Ariege and Adour basins. Industries such as metallurgy and surface treatments contribute to the naturally occurring metals, particularly in the Lot, Tarn and Charente basins. In the upper and middle Garonne, some metals or metaloids are mainly associated to the dissolved fraction like As or Sb, or to the particulate fraction, like Pb. Some elements like As, Sb, Cu or Mo show concentration increases during floods (contents can exceed >20 times the usual content for freshwater 0.4 mg/L). The suspended particulate matter is more pronounced in the Ariege than in the Garonne for a similar discharge, but the concentration of metals in this water fraction is higher in the Garonne (up to 1.8 times more for Cd and Sb). The arsenic concentrations are eight times higher than the world river average, which is linked with a lithogenic origin in the middle Garonne (Probst et al. 2006). The impact of a significant Pb contribution from Toulouse city is hidden by a local

191

Chapter | 5.3 The Adour–Garonne Basin

acid industrial discharge, which enhances the transport of Pb into the Garonne sediments (Quilici 2003). Some metals are enriched in the fine sediment fractions of the Garonne tributaries, such as the Save (Cd and Pb), that is linked to agricultural activities and/or atmospheric fallouts, or in the suspended matter of the Aussonelle (Cd, Pb, Sb, and Cu), linked to the strong urbanization along this tributary (Probst et al. 2006). The Lot system is known for its long-term pollution by mining since the 19th century (Audry et al. 2004). According to Blanc et al. (1999), about half of the cadmium in the lower Garonne originates from the Lot (90% transported in the particulate fraction), where 85% of the cadmium is from anthropogenic activities. Indeed this pollution has decreased since the 1990s (Audry et al. 2004), but the remaining contamination is higher than in the Garonne and varies according to hydrological conditions. In wet years, there is a strong contribution of the Lot, whereas in dry years the contribution from the upper Garonne is more significant. Blanc and Sch€afer (2002) showed that Cd (and Zn) is not the only potential toxic metal transported to the bay of Gascogne by the rivers. When compared with the world river average concentrations, elements such as As, Sn, U, Cu and Ag occur in high concentrations and can reach the estuary. In the lower Garonne, intense agriculture also influences metal inputs (Zn and Cu) into the Gironde estuary, especially via the Isle River (Masson et al. 2006). Like in the middle Garonne, the highest As concentrations observed in the Isle river originate local bedrock (Masson et al. 2007). Moreover, as observed in the upper Garonne, where mining wastes or Toulouse city influence PHE concentrations (Baque, 2006); the role of hydrological events on the transport of trace metals is crucial. For example, during a major flood in the Lot River, 90% of the particulate Cd originated from resuspended reservoir sediments (Coynel 2005). Phytosanitary products can significantly pollute the Garonne basin rivers, particularly in spring with pesticides, among which herbicides are dominant. The phytosanitary quality of the rivers in the Garonne basin ranges from medium to good, but three basins are particularly influenced by these products, that is the Adour, the middle Garonne, and the Charente. Atrazine is the most often detected compound (31%). According to a report from ‘France Nature et Environnement (2006)’, the amount of phytosanitary products used by non-agricultural users in the Adour–Garonne basin were 130 tons/year glyphosate, 60 tons/year diuron and 50 tons/year aminotriazole. In comparison, 110 tons/year glyphosate, 92 tons/year diuron, 147 tons/year aminotriazole were applied to 227 000 ha of vineyards in the Adour–Garonne territory (Cemagref 1991; AEAG 2004). Measurements in the Adour–Garonne basin showed that 58% of the sampled sites were good, 32% medium, and 10% poor or very low quality (this evaluation is not exhaustive). Of 32 groundwater bodies, 20% of the sites were problematic with respect to pesticides (those exceeding the

limit of 0.1 mg/L per substance and 0.5 mg/L per total), and 16 of them revealed more than 50% of problematic sites. Like for metals, hydrological conditions are essential for pesticides transfer downstream and the sediment is a favourite river storage compartment, where degradation/remobilization might occur. Urban practices were shown to play a significant role on pesticide contamination downstream Toulouse, and to be a major contamination source in sediments particularly during winter (Devault et al. 2007).

5.3.6. AQUATIC AND RIPARIAN BIODIVERSITY The Garonne acts as a biological corridor connecting the Pyrenees and the Massif Central. In its middle section, the Garonne flows through a deforested area consisting of plains and cultivated hillslopes of the western Gers, the Garonne and Ariegeoise plains, and the Lauraguais. Many forest species (mammals, birds, amphibians, reptiles) are thereby missing or very rare. The Massif Central and the Pyrenees are important forested areas in the north and south of this open landscape. Between these two ranges an exchange of fauna occurs along the riparian corridor of the Garonne and its tributaries Tarn, Lot, Baise, Gers, Gimone, Save, Touch, Louge and Ariege. The riparian forest is highly fragmented with only small woodlots persisting on river banks that play an important role as ‘stepping stones’ for animals such as Parus palustris (Marsh Tit), Sylvia borin (Garden Warbler), Sciurus vulgaris (Red Squirrel) and Apodemus sylvaticus (Wood mouse). As a mainly Mediterranean environment, the 440-km long and 150-km wide humid mountain range of the Pyrenees represents a middle-European mountain island with a very rich fauna and flora, and high habitat diversity. The relatively large size of the range supports demographically important and stable populations. The geographical situation at the boundaries of middle-European, Atlantic, and Mediterranean areas add an additional dimension to the variety of mountain and boreal–alpine environments. Following glaciations, many species with boreal–arctic affinity found refuge along with the purely alpine species. Some species were isolated in the area and became endemic. There is a significant number of middle-European species, the Pyrenean populations of which are physically separated from their middle-European demographic reservoir by the deforested corridor of the Garonne plain and the Lauraguais.

5.3.6.1. Riparian Vegetation Most of the large rivers of the Garonne–Adour catchment were once enveloped by wide, diverse riparian forests. In the mountain zones, floodplain forests were narrow and dominated by European ash (Fraxinus excelsior), broad-leaf willow (Salix appendiculata), lime trees (Tilia sp div.),

192

mountain elm (Ulmus glabra) and maples (Acer pseudoplatanus, A. platanoides). Further downstream, they became wider and were differentiated into pioneer vegetation, mainly white willows (Salix alba, S. fragilis), black poplar (Populus nigra), alder (Alnus glutinosa), and mature stands of narrow-leaf ash (Fraxinus angustifolia), elm (Ulmus minor, U. laevis), and atlantic oak (Quercus robur). In the eastern part of the Garonne catchment, some submediterranean influence is evident in the occurrence of white poplar (Populus alba). After centuries of human influence (since the Middle Ages) on land-use and river dynamics, today’s riparian forests of most of large rivers have only remnant mature forests. Until very recently, the lower reaches of the Adour and mountain streams remained well preserved, having mature riparian forests and marshy habitats due to wide floodplain areas. Regional riparian floras remain species-rich (e.g. 2000 plant species along the 350-km long Adour corridor). High species richness is also observed at more local scales (e.g. 700 plant species on 15 ha or up to 100 plant species on 4-m2 along the middle Garonne River). However, former floras have been altered by the introduction of non-native species (about 900 non-native plants occur in the Adour–Garonne basin in 2005, representing 25% of the plant species on average) and by the invasion of nonriparian, ruderal species. Some non-native species such as box elder (Acer negundo), butterfly bush (Buddleja davidii) or Asian knotweeds (Fallopia japonica, Fallopia bohemica) can be highly invasive locally and may alter the functioning of riparian ecosystems. Further, most wetlands (dead arms, marshes) and ephemeral habitats (gravel bars, temporary ponds) have disappeared during the past 50 years, increasing the natural rarity of many specialized (endangered) species. Many riparian forests in the lowlands have been replaced by plantations (mainly poplar groves). In addition to land-use change, these introductions might contribute to changes in the genetic structure of local species (e.g. introgression of Populus nigra by P. deltoides). River alteration is probably responsible for the massive decrease by other keystone species such as white willow (Salix alba) observed along most rivers of the watershed. Anthropogenic influences have strongly altered the extent and biodiversity of riparian and aquatic vegetated areas along most of rivers in the Adour–Garonne catchment. Very recently, managers have recognized the importance of the ecological services (e.g. nutrient flow or sediment dynamics buffering) or of the ecological factors (biological invasions, eutrophication) linked to fluvial vegetation dynamics. Some direct (plantation, reserve areas) or indirect (restoration of fish spawning zones along dead arms) actions have been initiated to preserve or restore healthy vegetated areas. Many alterations still appear irreversible due to economic–social (agriculture, energy production) or natural (climate change) constraints. Therefore, strong qualitative changes in biodiversity and, most likely, in ecological functions are expected

PART | I Rivers of Europe

in the future among river plant communities in the Adour– Garonne catchment.

5.3.6.2. Phytobenthos and Phytoplankton The upper Garonne River, including the Ariege tributary, displays strong hydrodynamics that favours phytobenthic production. In this area, there is some concordance between discharge and benthic chlorophyll-a (Chl-a) levels (Ameziane et al. 2003). During low flows, mature phytobenthos communities slough or become senescent (Boul^etreau et al., 2006). In this area, mean values of Chl-a are low (4 mg/L) but during the flow peaks there is a scouring and high values of Chl-a occur during short periods. The reservoirs of Mancies and Labrioulette have some local influence, with occasional increases in true phytoplankton (up to 50% of Chl-a in the Garonne River) due to the increase in residence times during summer low flows. Downstream of Toulouse, some tributaries from the Gascogne hillside having intensive agriculture and from the alluvial plain of Garonne (e.g. rivers Touch, Save, Hers, Gimone) are eutrophic. Their contribution to the Garonne total flow is low and they do not act as significant sources of algal biomass. The Tarn is a main tributary of the Garonne, and delivers high values of Chl-a (mainly due to phytoplankton) during low flows in summer (20–30 mg/L). The Garonne and Tarn converge in the Malause reservoir (3.5 days average residence time). Phytoplankton production in the Tarn and in the reservoir increase Chl-a values downstream the dam (mean of 23 mg/L). In the lower Garonne, the Gers, Baise and Lot are eutrophic rivers and contribute in high loads of phytoplankton. Because of irrigation for agriculture, their summer flows are very low compared to the Garonne River budget and they do not significantly influence the algal composition (phytoplankton and phytobenthos) in the river. The Tarn, Lot, Gers and Baise are slow-flowing regulated rivers fragmented by dams. For example, the residence time is about 2 months for the river Lot (300 km) in summer. Eutrophication in the Garonne is generally low, and periphyton is the main primary producer with an average of 80 mg dry weight/m2 (Ameziane et al. 2002). The Dordogne tributary of the Garonne has high ecological quality upstream of the hydropower dam of Bort Les Orgues. The residence time in this large impoundment is long; about one year depending on hydropower production. In the reservoir, a significant summer phytoplanktonic production occurs and just downstream of the dam the water quality is altered by an ammonia increase. In the middle reach of the Dordogne, the water is clear and it becomes a mesotrophic river. Here, little or no phytoplankton occurs and the dominant primary producers are benthic algae and submersed macrophytes. In the downstream section between Bergerac and Libourne, the river becomes deeper and true phytoplankton biomass increases.

193

Chapter | 5.3 The Adour–Garonne Basin

Phosphate (mg /L)

2.0

1.5

1.0

0.5

0.0 '75

1980

'85

1990

'95

2000

'05

FIGURE 5.12 Time series of phosphate in the Garonne River at Gagnac (1975–2006). Data belong to National Network from Adour-Garonne Basin.

The Adour basin is characterized by fast-flowing rivers of Pyrenean Piedmont with high energy and coarse substrates. In the middle and lower river, irrigated agriculture is predominant and results in exceptional low flows and eutrophication in summer. Two flow-sustaining dams (Lavaud and Mas-Chaban) have been built on the Charente hydrographic network and mark the beginning of the eutrophic part of the basin. They have been specifically equipped with aerators to limit the negative impacts of eutrophication such as algal and cyanobacteria blooms. The main part the Charente basin is on calcareous bedrock, and the river is fragmented by many small dams and used for irrigation. The city of Angoul^eme, including its industrial zone, is an area of intensive pollution (e.g. the Frejeneuil sewage plant). From 1960 to 1980, the Charente downstream of Angoul^eme was highly eutrophic with low transparency and high levels of phytoplankton (30–50 mg Chl-a, summer average). Upgrading the sewage treatment facilities between 1990 and 1996 resulted in a reduction in nitrogen and phosphorus concentrations (Figure 5.12) that decreased phytoplankton levels and increased transparency. Primary production by periphyton and macrophytes subsequently increased in the river. The Leyre River drains the acidic sandy zone of the Landes and has relatively good water quality. Its basin is dominated by pine plantations that occupy 80–92% of land area. After the 1950s, some areas were cleared to prevent large forest fires, drained and irrigated (mostly corn and vegetable crops), increasing nutrient levels in the river. Primary production in the river is low and mostly done by aquatic macrophytes and periphyton.

5.3.6.3. Macrophytes The dominant macrophytes in most large rivers in the Adour–Garonne catchment are taxa also common in the French territory such as R. fluitans, Potamogeton nodosus, M. spicatum and Sparganium emersum in flowing habitats, and Ceratophyllum demersum, N. lutea, and Vallisneria spiralis in slow flowing areas. Other species like Potamogeton pectinatus and Najas marina are present in more eutrophic waterbodies (Rebillard 1999). In the Leyre River, where

mobile sands prevail, occur Callitriche spp. and Potamogeton polygonifolius. Because of the high instability of flow of the Garonne, significant colonization of macrophytes is limited to years with attenuated hydrodynamics and to reaches where the river is wide and shallow. The Dordogne river embeds various hydromorphological facies, with quite favourable habitats for macrophytes. It has been clearly demonstrated in Garonne and in Dordogne that, at a pluriannual time scale, macrophyte cover is inversely correlated with flood intensity (Breugnot et al. 2004a, 2004b). In the Charente, macrophytes growth is high because of reduced current velocities due to flow regulation by dams (Dutartre et al. 1994). River regulation altered the distribution of some taxa; Ranunculus spp., in particular, colonized the lower reaches of the Dordogne and Lot (CEER 1991; EPIDOR 2003). The prolific growth of R. fluitans in the river for over 20 years negatively impacted tourist activities (Rebillard et al. 2003). The Garonne–Adour catchment has also been invaded by non-native macrophytes such as Lagarosiphon major and Egeria densa, and amphiphytes like Ludwigia grandiflora, L. peploides, and Myriophyllum aquaticum. The two non-native species of Ludwigia are present at different sites along the middle and lower reaches of Garonne, Dordogne and Adour, and started to colonise the Charente in 2004.

5.3.6.4. Macroinvertebrates Macroinverterbrates in the drainge network consist of 1045 species (Cereghino et al. 1999) of which 78% are insects in 8 orders. Some 32% of the total species number are dipterans (Chironomidae), 9.5% are oligochaetes and 8% hydracarina (Cereghino et al. 2001). Most species can be considered ‘rare’, being found in <5% of the stations surveyed (Santoul et al. 2005). One example is Capnia bifrons (Plecoptera), which is found in the Garonne and Tarn-Aveyron basins at altitudes between 350 and 670 m asl. Also, Thraulus bellus (Ephemeroptera, Leptophlebiidae) was recorded only at one Adour station. About 34% of the species are ‘common’ and found in 6–20% of the stations surveyed. This is the case for Perla grandis (Plecoptera, Perlidae), frequently found in the Pyrenees between 500 and 1600 m asl. A few species (8%) are largely distributed (present in 20–50% of the stations). These often have a wide ecological spectrum and are found in various kinds of river habitat (Cayrou et al. 2000). For instance, Esolus parallelepidedus (Coleoptera, Elmidae), a species that inhabits waters between 140 and 1200 m asl, can be found in the Garonne, Adour, Lot, Tarn and Aveyron basins. Species richness, in general, may not be a good indicator of environmental conditions of rivers (Compin & Cereghino 2003). The Ephemeroptera, Plecoptera, Trichoptera, and Coleoptera (EPTC) are good estimators (surrogate taxa) of river conditions (Cereghino et al. 2001), whereas other groups provide poor assessments. For example, only 22 species of

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the 339 identified Chironomidae in the catchment provide good assessment information (Compin 1998). The EPTC are well known for their sensitivity to environmental changes and, in particular, to chemical and organic pollution. EPTC species richness seems to be particularly correlated to altitude and maximal water temperature (Cereghino et al. 2003). At the regional scale, richness values appear correlated to altitudinal and thermal variations and explain little in terms of local variation (Compin & Cereghino 2007).

5.3.6.5. Fishes The Garonne River poorly matches the classical longitudinal zonation river model of Huet (1959), because the barrier of the Massif Central impeded the dispersion of grayling (T. thymallus) in the basin. The river network of the Garonne has 920 artificial barriers, comprising 90 retention dams and 803 artificial waterfalls that constrain fish migration along the river. The lower Garonne, however, remains one of the least regulated of the French rivers. The Garonne has preserved some natural attributes due to various administrative protective regulations of the aquatic environment (biotope protection, control of effluent quality, rehabilitation and protection of wet zones). Fish communities in the Garonne catchment have been studied at the scale of local watersheds and ecoregions (Mastrorillo et al. 1998; Ibarra et al. 2005a, 2005b). At the reach scale, salmon dominate the piedmont (transition salmonids/cyprinids dominance) and cyprinids dominate the plain (Baran et al. 1995, 1996, 1997; Delacoste et al. 1995; Lagarrigue et al. 2001; Gouraud et al. 2001; Lim et al. 1985; Pouilly et al. 1996; Reyjol et al. 2001a, 2001b; Dauba et al. 1997). At the local scale, fluvial connectivity (Bengen et al. 1992), industrial pollution (Dauba et al. 1992; Hutagalung et al. 1997), the fish-lift of Golfech (Belaud et al. 1990; Belaud & Labat 1992) influence the migration and reproduction of allis-shad (Bengen et al. 1992; Bellariva & Belaud 1998; Dauba 2005, 2006). In the Garonne–Adour catchment, 44 fish species in 13 orders and 17 families have been found. Among these species, 19 are indigenous, 17 introduced, and 8 diadromous. Some 21 species of fish are omnivorous, 14 insectivorous, 5 piscivorous, 2 detrivorous, and 1 herbivorous. The majority of species are lithophilic (associated with gravel substrates) and phytophilic (associated with aquatic vegetation). The Garonne River is richer in fishes than the Ariege, Tarn, Lot, and Dordogne basins. However, fish diversity in the Garonne–Adour catchment is less than that of other large French catchments (Rhone 56, Loire 50) (Changeux 1994), probably because of its isolation from other large fluvial systems by the Massif Central and Pyrenees, and the large distance from the Danube, considered the cradle of European freshwater fishes (Persat & Keith 1997). Fish richness increases along the main axis of the catchment. Trout and bullhead dominate in the mountain zone and become progressively replaced in the piedmont zone by

PART | I Rivers of Europe

species such as stone loach, minnow and gudgeon, and subsequently by barbel, chub and dace. Roach, rudd, tench and pike appear in the floodplain channels (Bengen et al. 1992; Gozlan et al. 1998). The lower river is the place of transit and the reproduction zone of migratory species such as Atlantic salmon, shad and sea lamprey. It is also habitat for species resistant to turbidity and high temperatures such as eel, grey mullet, bream, catfish, pumpkinseed, pike-perch and wels. Features that characterize the Atlantic frontage of the Adour–Garonne catchment include estuaries such as the Gironde and the lower Garonne and Dordogne where a tidal influence reaches as far as 160 km upstream, and the smaller systems of the Adour and Charente that host a range of marine and estuarine species found in continental/oceanic transition zones such as anchovy, sand melt, sea-bass, herring, seahorse, whiting, rockling, garfish, ray, sole, sprat pipe fish and pout. Further, as the only western European district, most migratory species such as eel, flounder, mullet, sea lamprey, river lamprey, European sturgeon, Atlantic salmon, sea trout, smelt, Twaite shad, and Allis shad occur here. Several of these species are endangered and target species of restoration projects. The principal causes for the decline in the fish populations are river fragmentation, stabilization of river banks, pollution, over fishing, loss of spawning areas, mud deposition in impoundmented reaches, hydraulic management by locks, pumping of water that affects young fishes, low flow during dry periods aggravated by water abstraction, and increasing summer temperatures. Migratory fishes were able to resist the development of small dams, steps and mills, as well as traditional fishing activities during the medieval period. The revolutionary and imperial period (1790–1870) lead to a decrease of species sensitive to river fragmentation and pollution such as the Atlantic salmon. Hydroelectric facilities in the upper basin resulted already in the early 20th century to the extinction of the Atlantic salmon and a decline in shad, eel, sea lamprey and Atlantic sturgeon populations. After the Second World War to the 1980s, urban and industrial development increased the pressure on rivers, especially via gravel extraction that enhanced channel degradation, reduced the diversity and stability of habitats, and eliminated spawning areas. The growing efficiency of fishing and use of transparent nylon nets also reduced species abundances and brought the European sturgeon to the brink of extinction. Sturgeon catches dropped from several thousand in the 1960s to about 10 in the 1980s when the species became completely protected. A comprehensive restoration program (beginning in 1950) with respect to migratory fishes included the construction of fish passes, stocking, limits on catches and complete protection of some species in the Garonne, Dordogne and Adour basins. The construction of fish passes allowed the migration of large migratory fishes. In 2002, migration was possible in 75% of the priority 1 migratory axis (2170 km) and in 22% of the priority 2 axis (360 km). Satisfying results have been obtained in the Adour with an increase in the

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Chapter | 5.3 The Adour–Garonne Basin

TABLE 5.5 Professional fish catches (average 1999–2003, Cemagref 2006) Species

Shad

Sea lamprey

Glass eel

Eel

Shrimp

Other species

Catch (tons) Value in 1000 euros Percentage

408 1122 15

88 1277 17

26 4092 53

17 180 2

50 504 7

97 553 7

number of returning salmon (up to 8000 fish). Less satisfying is the situation in the Dordogne and Garonne, especially in warm years with early low flows. The twaite shad responded rapidly to the implementation of fish passes and the fish lifts of Golfech in the Garonne and of Tullieres in the Dordogne (200 000–350 000 shads annually in the past decade). The warm years of 2003 and 2006 impeded reproductive success. The small population size of the European Sturgeon (only a few thousands individuals) prevented recovery of the population because of low reproduction success (the last natural reproduction occurred in 1988 and 1995). The length of the life cycle with sexual maturity after 10 years (males) and 14 years (females) and accidental captures at the sea have caused further impediments to recovery. A stock of 80 fishes is held at Cemagref (public agricultural and environmental research institute) experimental station of St. Seurin sur l’Isle (near Bordeaux) to restock a part of sturgeon population and be able to the Garonne and later reintroduce the sturgeon in European river catchments where it is extinct. The professional fishery in the Adour–Garonne catchment is about 1200 tons/year with a value of about 14 million euros. Catches show a high inter-annual variability. In the Gironde estuary (the best monitored system with respect to fishery), the catch by 200 professional fishers was about 700 tons/year (about 8 million euros) from 1999 to 2003 (Table 5.5). Most of the catch is migratory fishes, especially glass eel, an endangered species in which the abundance has declined by 90% in 20 years. The attractiveness of the large rivers for recreation fishing, practiced by several thousand people in the Adour–Garonne catchment, is low.

5.3.6.6. Birds Large migrations of birds, linking central and eastern Siberia to tropical Africa, result in a WSW-ENE migration route. The French southwest, representing a bottleneck to this route, is therefore visited by thousands of migratory birds using the Atlantic, Mediterranean and Central migration routes through the Garonne. The Garonne valley includes many sites listed in the Z.N.I.E.F.F. (Zones Naturelles d’Inter^et Ecologique, Faunistique et Floristique) and I.C.O. (zones importantes pour la conservation des oiseaux) inventories, especially referring to the areas with heron (Ardeidae) colonies. Of the numerous birds that currently inhabit the Adour basin, the most notable species are often European birds with

the Pyrenees as the southern boundary of occurrence. These species (in the Pyrenean Piedmont) form populations separated from their principal European and Continental areas of occurence by unforested agricultural land of the Garonne– Lauraguais corridor. These include Wood Warbler (Phylloscopus sibilatrix), Garden Warbler (S. borin), Marsh Tit (P. palustris), Edge Sparrow or Dunnock (Prunella modularis), Bull Finch (Pyrrhula pyrrhula), Yellow Wagtail (Motacilla flava), Middle Spotted Woodpecker (Dendrocopos medius), and Black Woodpecker (Dryocopus martius), which include the most northern Pyrenean population. Other interesting birds are the Booted Eagle (Hieraaetus pennatus), reproducing in the woody massif and hunting in open terrain. The Grey Heron (Ardea cinerea) is present all year but with irregular reproduction. The rare Purple Heron (Ardea purpurea) reproduces in the reeds of dead arms and abandoned gravel pits. The most common heron is the Black-crowned Night Heron (Nycticorax nycticorax), with >3000 breeding pairs in 1990. The Adour–Garonne watershed houses over 2/ 3 of the French population of this heron.

5.3.7. MANAGEMENT AND CONSERVATION 5.3.7.1. Economic Importance In the Adour–Garonne catchment, the importance of agriculture is a major factor in water management and a major economic concern. Agricultural water use is dominant in summer (43% of the irrigated surfaces in France). About 700 hydroelectric plants produce 14.5 MWh (20% of the French hydroelectric production), representing 35% of the electrical consumption in the catchment. Two nuclear power plants are found within the catchment: Golfech (1.3 GW) on the Garonne downstream of Toulouse, and Blayais (3.8 GW) on the bank of the Gironde estuary. These rivers have lost their role in transport and now are centres of tourist travel with over three million visitors. The navigable network of the catchment is estimated at 850 km. Tourism is high in the littoral zone, Pyrenees, Dordogne, and to a lesser extent on the western fringe of the Massif Central. The Dordogne River and its banks offer a quasi-unlimited tourism potential. In summer, the valley population increases by 40%. The basin also holds 35 thermal resorts (1/3 of the French resorts). In 2001, over 2500 million m3 of water were abstracted from the rivers, artificial reserves and aquifers for irrigation (1000 million m3), industrial needs (750 million m3), and

196

drinking water (750 million m3). These water needs seem low if compared with the annual discharge of the catchment at about 45 billion m3. This view is misleading because during critical low water periods (summer and early autumn), the water balance is based on many factors and faces the problem of net consumption and the minimal flow necessary for a good ecological condition. The net consumption during low water periods (there are 6421 abstraction points in the catchment) reaches 700 million m3, of which 85% is for irrigation. This consumption is only in part compensated from low water support reserves (about 130 million m3). The pressure on deep groundwater is so high that it may impede its priority use for drinking water. These aquifers include the Bordeaux Eocene aquifer, the infra molassic sands of the southern basin, Jurassic aquifers (Dordogne, Lot, and Garonne), the Turoniens (Charente), and the infra Toarcien aquifers in Poitou Charente.

5.3.7.2. Protected Areas Protected areas include one National Park (Pyrenees, 60 000 ha) and six regional natural parks: Marais-Poitevin (68 000 ha), Perigord-Limousin (180 000 ha), Causses du Quercy (176 000 ha), Haut-Languedoc (260 000 ha), Grands Causses (347 000 ha), and Landes de Gascogne (315 000 ha). Presently, there is no Ramsar site in the catchment. The formation of the Natura 2000 network designated numerous special protection zones (bird directive) and special conservation zones (habitat directive) in the catchment: 114 in the Midi-Pyrenees sector, and 150 in the Aquitain sector. The special protection zones cover 1315 km2, being 1.1% of the catchment surface area.

5.3.7.3. The European Water Framework Directive (WFD) Of the 20 000 evaluated river km, only 18% were considered to be under low pressure and modification, whereas 37% were subject to very high pressure and modification. Modification of the flow regime (43%) and river fragmentation (50 %) are the most severe alterations. Morphologically affected watercourses comprise 24% evaluated systems, most strongly impacted are reaches linked to hydroelectric power production. Considering good ecological status, about 28% of the watercourses are presently classified as strongly modified (provisional classification) but are likely to reach a good state. Hydroelectric use, especially in the Pyrenees and Massif Central, flood protection, river training, former gravel extraction and dams have extremely changed the natural morphological characteristics of many rivers and have reduced their longitudinal, lateral and vertical connectivity. Implementation of the nitrate directive led to the designation of various vulnerable zones. In 2002, these covered >32 300 ha, where the surface and ground waters are contaminated. About 25% of the livestock farms

PART | I Rivers of Europe

are involved by contract in programs ensuring compliance with regulations. The enforcement of the 1992 French water law, a management and master development plan of water (SDAGE), was published in 1996. SDAGE will be revised by 2009 in response to the management plan demanded by new law for water and aquatic ecosystems (December 2006). SDAGE proposed for the Adour–Garonne catchment allows a greater consideration of the four goals set by the WFD that specify the political management of the catchment: (1) focus on reducing river pollution, (2) re-establishing the minimum low water flow in the most affected rivers, (3) protect and re-establish important aquatic and littoral environments, (4) open the water courses to large migrating fishes, (5) restore and preserve river functioning, (6) protect the quality of groundwater necessary for drinking water supply, (7) separate and make known to the public areas subject to inundation hazards, and (8) establish a balanced and global management of the catchment and its aquifer system.

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Chapter | 5.3 The Adour–Garonne Basin

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Compin, A., and Cereghino, R. 2007. Spatial patterns of macroinvertebrate functional feeding groups in streams in relation to physical variables and land-cover in southwestern France. Landscape Ecology 22: 1215–1225. Coynel, A. 2005. Erosion m ecanique des sols et transferts g eochimiques dans le bassin Adour–Garonne. These Universite Bordeaux I, 572 pp. + annexes. Dauba, F. 2005. Observations sur l’ichtyofaune de la Garonne a Golfech au cours de l’ann ee 2004. Rapport INP Toulouse/CNPE Golfech, 77 pp. Dauba, F. 2006. Observations sur l’ichtyofaune de la Garonne a Golfech au cours de l’ann ee 2005. Rapport INP Toulouse/CNPE Golfech, 72 pp. Dauba, F., Kugler, J., Belaud, A., and Labat, R. 1992. Recherche de signes de toxicite subletale de l’ammoniaque pour les truites en milieu naturel. Ichtyophysiologica Acta 15: 99–114. Dauba, F., Lek, S., Mastrorillo, S., and Copp, G.H. 1997. Long-term recovery of macrobenthos and fish assemblages after water pollution abatement measures in the river Petite Baise (France). Archives of Environmental Contamination and Toxicology 33: 277–285. Decamps, H., Fortune, M., and Gazelle, F. 1989. Historical changes of the Garonne River, Southern France. In: Petts, G.E. (ed). Historical Changes of Large Alluvial Rivers: Western Europe, J. Wiley and Sons, Chichester, pp. 249–267. Delacoste, M., Baran, P., Lascaux, J.M., Segura, G., and Belaud, A. 1995. Capacite de la methode des microhabitats a predire l’habitat de reproeche et de pisciculduction de la truite commune. Bulletin fran¸cais de p^ ture 337–339: 345–353. Devault, D.A., Merlina, G., Lim, P., Probst, J.L., and Pinelli, E. 2007. Multiresidues analysis of pre-emergence herbicides in fluvial sediments: application to the mid-Garonne river. Journal of Environmental Monitoring 9: 1009–1017. Dutartre, A., Codhant, H., Mary, N. 1994. Les vegetaux aquatiques et le transfert des nutriments dans le fleuve Charente: les macrophytes. Symposium Relations continent-zones c^ oti eres, La Rochelle, 13–15 Septembre 1994, 10 pp. EPIDOR, 2003. Evolution des herbiers de la Dordogne entre le barrage du Sablier et Castillon-la Bataille. Rapport, 25 pp. Etchevers, P. 2000. Modelisation du cycle continental de l’eau a l’echelle regionalo. Impact de la modelisation de la neige sur l’hydrologie du Rhone. PhD thesis, University Toulouse III, 361 pp. Foucault, A., and Raoult, J.F. 1988. Dictionnaire de G eologie. Masson, Paris 350 pp. Gouraud, V., Bagliniere, J.L., Baran, P., Sabaton, C., Lim, P., and Ombredane, D. 2001. Factors regulating brown trout populations in two french rivers: application of a dynamic population model. Regulated Rivers: Research and Management 17: 557–569. Gozlan, R.E., Mastrorillo, S., Dauba, F., Tourenq, J.N., and Copp, G.H. 1998. Multi-scale analysis of habitat use during late summer for 0+ fishes in the river Garonne (France). Aquatic Science 60: 99–117. Habets, F., Etchevers, P., Golaz, C., Leblemois, E., Ledoux, E., Martin, E., Noilhan, J., and Ottle, C. 1999. Simulation of the water budget and the river flows of the Rhone watershed. Journal of Geophysical Research 104: 31145–31172. Huet, M. 1959. Profiles and biology of western European streams as related to fish management. Transaction of the American Fisheries Society 88: 155–163. Hutagalung, R.A., Lim, P., Belaud, A., and Lagarriguet, T. 1997. Effets globaux d’une agglomeration sur la typologie ichtyenne d’un fleuve: cas de la Garonne a Toulouse. Annals de Limnologie – International Journal of Limnology 33: 263–279. Ibarra, A., Dauba, F., and Lim, P. 2005a. Influence of non-point source pollution on riverine fish assemblages in South–West France. Ecotoxicology 14: 573–588.

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Ibarra, A., Lim, P., and Lek, S. 2005b. Fish diversity conservation and river restoration in southwest France: a review. In: Lek, S., Scardi, M., Verdonschot, P.F.M., Descy, J.P., Park, Y.S. (eds). Modelling Community Structure in Freshwater Ecosystems, Springer, pp. 64–75. Lagarrigue, T., Baran, P., Lascaux, J.M., Delacoste, M., Abad, N., and Lim, P. 2001. Taille a 3 ans de la truite commune (Salmo trutta L.) dans les rivieres des Pyrenees fran¸caises: relations avec les caracteristiques mesologiques et l’influence des amenagements hydroelectriques. Bulletin fran¸cais de p^ eche et de pisciculture 357–360: 549–571. Lambert, R. 1989. A propos de la plaine de riviere: evolution geomorphologique et ressources en eau. Revue de G eographie des Pyr en ees et du Sud-Ouest 4: 549–553. Lim, P., Belaud, A., and Labat, R. 1985. Peuplement piscicole de la Garonne entre Saint-Gaudens et Agen. Ichtyophysiologica Acta 9: 187–2001. Loubet, M., Baque, D., Oliva, P., and Dupre, B. 2003. Metal content in the Garonne basin: evidences for a general non-point contamination of anthropogenic origin. Journal de Physique IV 107: 793–796. Maneux, E., Dumas, J., Clement, O., Etcheber, H., Charritton, X., Etchart, J., Veyssy, E., and Rimmelin, P. 1999. Assessment of suspended matter input into the oceans by small mountainous coastal rivers: the case of the Bay of Biscay. Comptes Rendus de l’Acad emie des Sciences Paris, Sciences de la Terre et des Plan etes/Earth & Planetary Sciences 329: 413–420. Masson, M., Blanc, G., and Sch€afer, J. 2006. Geochemical signals and source contributions to heavy metal (Cd, Zn, Pb, Cu) fluxes into the Gironde Estuary via its major tributaries. Science of the Total Environment 370: 133–146. Masson, M., Schafer, J., Blanc, G., and Anschutz, P. 2007. Seasonal Variations and Annual Fluxes of Arsenic in three contrasting watersheds: the Garonne, Dordogne and Isle Rivers. Science of the Total Environment 373: 196–207. Mastrorillo, S., Dauba, F., Oberdorff, T., Guegan, J.F., and Lek, S. 1998. Predicting local fish species richness in Garonne river watershed. Comptes Rendus de l’Acad emie des Sciences Paris, Sciences de la vie 321: 423–428. Pouilly, M., Souchon, Y., Lecoarer, Y., and Jouve, D. 1996. Methodology for fish assemblage habitat assessment in large rivers: application in the Garonne river (France). Proceedings of the 2nd Int. Symposium on Hydraulic Habitats Ecohydraulique 2000,, pp. 323–329. Probst, A., Aubert, D., Bouletreau, S., Dalger, D., Dauba, F., Delmas, F., Devault, D., Dubernet, J.F., Durbe, G., Henry, M., Julien, F., Lim, P., Merlina, G., Mohamadou, M., Pinelli, E., Probst, J.L., Sanchez-Perez, J. M., Sauvage, S., and Vervier, P. 2006. Transport de contaminants dans le continuum Garonne Moyenne en situations hydrologiques contrastees. Journee de restitution des travaux scientifiques du Programme ECO-

PART | I Rivers of Europe

BAG P2. “Circulation de l’eau, des mati eres et des esp eces au sein du Bassin Adour–Garonne relations amont aval et r^ ole des discontinuit es”, Bordeaux, 28/03/06. Quilici, H. 2003. Comportement chimique du plomb dans l’environnement – Cas du bassin du Strenbach (Vosges) – Cas de la Garonne a Toulouse. Th ese de doctorat, universit e Paul Sabatier (Toulouse III), 284 pp. Rebillard, J.P. 1999. Des rivieres en fleurs. Adour Garonne 75: 3–6. Rebillard, J.P., Roignant, F., Ferroni, J.M., and Dutartre, A. 2003. Travaux experimentaux sur l’herbier de renoncules aquatiques d’Entrayguessur-Truyere. Adour Garonne 86: 1–6. Reyjol, Y., Lim, P., Belaud, A., and Lek, S. 2001a. Modelling of microhabitat used by fish in natural and regulated flows in the river Garonne (France). Ecological Modelling 146: 131–142. Reyjol, Y., Lim, P., Dauba, F., Baran, P., and Belaud, A. 2001b. Role of temperature and flow regulation on the Salmoniform–Cypriniform transition. Archiv f€ ur Hydrobiologie 152: 567–582. Santoul, F., Figuerola, J., Mastrorillo, S., and Cereghino, R. 2005. Patterns of rare fish and aquatic insects in a southwestern French river catchment in relation to simple physical variables. Ecography 28: 307–314. Sch€afer, J., Blanc, G., Lapaquellerie, Y., Maillet, N., Maneux, E., and Etcheber, H. 2002. Ten-year-observation of the Gironde tributary fluvial system: fluxes of suspended matter, particulate organic carbon and cadmium. Marine Chemistry 79: 229–242. Steiger, J., and Gurnell, A.M. 2003. Spatial hydrogeomorphological influences on sediment and nutrient deposition in riparian zones: observations from the Garonne River, France. Geomorphology 49: 1–23. Steiger, J., Corenblit, D., and Vervier, P. 2000. Les ajustements morphologiques contemporains du lit mineur de la Garonne, France, et leurs effets sur l’hydrosysteme fluvial. Zeitschrift f€ ur Geomorphologie. Suppl. -Bd 122: 227–246. Steiger, J., Gurnell, A.M., Ergenzinger, P., and Snelder, D. 2001. Sedimentation in the riparian zone of an incising river. Earth Surface Processes and Landforms 26: 91–108. Steiger, J., James, M., and Gazelle, F. 1998. Channelization and consequences on floodplain system functioning on the Garonne River, SW France. Regulated Rivers: Research and Management 14: 13–23.

FURTHER READING Agence de l’Eau Adour–Garonne. 2004. L’ etat des ressources en eau du bassin Adour–Garonne. Adopt e par le Comit e de bassin Adour–Garonne en 2004. 132 pp. http://dce.eau-adourgaronne.fr/m_pages.asp? menu=135&page=233&cata=110.

Chapter 6

The Rhine River Basin Urs Uehlinger

Karl M. Wantzen

Rob S.E.W. Leuven

Department of Aquatic Ecology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), CH-8600 D€ ubendorf, Switzerland

Limnological Institute, University of Konstanz, ATIG-Aquatic-Terrestrial Interaction Group, D-78457 Konstanz, Germany

Department of Environmental Science, Institute for Water and Wetland Research (IWWR), Faculty of Science, Radboud University Nijmegen, NL-6500 GL Nijmegen, The Netherlands

Hartmut Arndt Institute for Zoology, University of Cologne, D-50931 K€ oln, Germany

6.1. 6.2. 6.3. 6.4.

6.5.

6.6.

6.7.

6.8.

Introduction 6.1.1. Historical Perspective Biogeographic Setting Palaeogeography Physiography, Climate and Land Use 6.4.1. Geological Structure and Relief 6.4.2. Climate 6.4.3. Land Use Geomorphology, Hydrology and Biogeochemistry 6.5.1. Geomorphology of the Main Corridor 6.5.2. Hydrology and Temperature 6.5.3. Biogeochemistry Aquatic and Riparian Biodiversity 6.6.1. Habitat Structure and Riparian Zone 6.6.2. Benthic Algae 6.6.3. Macrophytes and Bryophytes 6.6.4. Plankton 6.6.5. Benthic Invertebrates 6.6.6. Fish 6.6.7. Amphibia and Reptiles 6.6.8. Avifauna 6.6.9. Mammals Management and Conservation 6.7.1. Economic Aspects 6.7.2. Floods and Flood Defense 6.7.3. Conservation and River Rehabilitation 6.7.4. EU Water Framework Directive The Major Rhine Tributaries 6.8.1. Aare 6.8.2. Neckar

Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

6.8.3. Main 6.8.4. Moselle Acknowledgements References

6.1. INTRODUCTION Nine countries are in part or entirely situated within the Rhine catchment, namely Austria, Belgium, France, Germany, Italy (only 51 km2), Liechtenstein, Luxemburg, The Netherlands and Switzerland. With a total length of about 1250 km, a drainage area of about 185 260 km2 and an average discharge of about 2300 m3/s, the Rhine ranks 9th among Eurasian rivers. The Rhine is the primary artery of one of the most important economic regions of Europe (annual gross domestic product of 1750 billion US$). The human population of the basin equals 58 million, many of them crowded in large urban areas extending along the river between Rotterdam and Basel. The Rhine provides services for transportation, power generation, industrial production, urban sanitation, drinking water for 25 million people, agriculture and tourism, and is a classic example of a ‘multipurpose’ waterway (Cioc 2002). The Rhine has greatly influenced the history, culture, and economy of Europe over the last 2000 years. On the other hand, its ecological integrity and biodiversity have been severely affected by human activities, particularly in the last 200 years (Friedrich & M€uller 1984). In this chapter, we first give a general overview of the Rhine basin and subsequently portray different aspects of the six morphologically distinct river sections (Figure 6.1a, b, Table 6.1) (Lauterborn 1916) that developed during the 199

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genesis of the river. These are: (1) The Alpine Rhine (Alpenrhein) and its tributaries, that is, the reach between the Rhine source (Lake Toma) and Lake Constance, (2) the High Rhine (Hochrhein) that flows from lower Lake Constance to Basel, there merging with the Aare, a paramount tributary of the Rhine with respect to discharge, (3) the Upper Rhine (Oberrhein), flowing through the rift valley of the Rhine Graben that extends from Basel to Bingen with the Neckar and Main Rivers as major tributaries, (4) the Middle Rhine (Mittelrhein), flowing through a narrow valley deeply incised in the Rhenish Slate Mountains and picking up waters of the Mosel River at Koblenz, (5) the Lower Rhine (Niederrhein), extending from Bonn to Lobith with Ruhr, Emscher and Lippe Rivers as major tributaries and (6) the Delta Rhine, where the discharge is divided in three major branches called Nederrijn–Lek, Waal and IJssel.

6.1.1. Historical Perspective Early evidence of human presence in the Rhine catchment comprises the jaw bone of Homo heidelbergensis (400 000– 700 000 years BP) and bones of Homo neanderthalensis (42 000 years BP). About 35 000 years ago, modern man (Homo sapiens) spread out across Europe. The tracks left by hunters in the last Ice Age and early postglacial include tools, hunting gear and prey leftovers, which have been found at numerous sites within the Rhine basin. As a consequence of postglacial warming, tundra that originally extended between the ice shields of Scandinavia and the Alps was invaded by trees; about 7000 BP vast forest covered Europe between the Atlantic coast and western Russia (K€uster 1999). The loss of hunting grounds limited the size of the human population, except for the Neolithic culture that adopted agriculture from the Middle East to central and western Europe (6000–7000 years BP). After 800 BC, western and central Europe and the Alps were settled by the Celts, presumably originating from late Bronze Age cultures. Their heritage includes numerous archaeological artefacts such as weapons, fineries, tombs, fortresses, and the names of streams and rivers. The name of the Rhine is of Celtic origin (Renos), which means flowing water. The Rhine becomes part of written human history with the arrival of the Romans. Caesar crossed and bridged the Rhine in 55 and 53 BC, and also gave a first description of the Rhine in his commentaries on the Gallic War ‘The Rhine rises in the land of the Lepontii, who inhabit the Alps. In a long swift course, it flows through the territories of Nantuates, Helvetii, Sequani, Mediomatrices, Triboci and Treveri. On its approach to the Ocean it divides into several streams, forming many large islands, and then through many mouths it flows into the Ocean’ (cited in Cioc 2002). Plinius wrote about the dwelling places in the delta as ‘There throws the Ocean itself, two times a day, daily and nightly, in a tremendous stream over a wide country, so one is in doubt if the ground belongs to the land or to the sea. There is living a miserable people on the highest known level of the tide and at

PART | I Rivers of Europe

these they built their huts, living like sailors when the water covers their environment and like shipwrecked when the water has gone’ (Huisman et al. 1998). With the conquest of Gaul, the Rhine between the sea and Neuwied (Middle Rhine) became part of the northern frontier of the Roman Empire (12–9 BC). The Romans fortified the border (Limes) from Neuwied in a southeast direction to the Danube at Regensburg, thereby extending the empire across the right bank. The Roman legacy includes many cities along the Rhine such as Chur (Curia) on the Alpine Rhine, Basel (Basilea), Mainz (Mogontiacum), Koblenz (Castellum apud Confluentes), Cologne (Claudia Ara Agrippinensium) and Nijmegen (Ulpia Noviomagus Batavorum). In the 3rd century AD, Germanic tribes increasingly attacked the area on the left bank, which was finally abandoned about 260 AD, and the Rhine then became the empire border between Lake Constance and the North Sea. Roman rule in the Rhine basin ended about 400 AD with the invasion of Germanic tribes. After 500 AD, the Rhine was part of the Kingdom of the Franks and with the coronation of Charlemagne (800 AD) it became the central axis of the Holy Roman Empire. In the following centuries, the empire became increasingly fragmented into numerous duchies, ecclesiastical and knightly states, each pursuing their own policy with growing success. In 1581, the seven northern provinces of The Netherlands declared independence from Spain. At the end of the Thirty Years’ War (1618–1648), The Netherlands and the Swiss Confederation, territories that included the Delta Rhine and Rhine headwaters, left the Holy Roman Empire. The expansion policy of Louis XIV, king of France, ended with the annexation of Alsace (1681) by which the Upper Rhine became the border river between the Kingdom of France and the Holy Roman Empire. During the French Revolution and subsequent Napoleonic wars, the Rhine came completely under the influence of France. In 1806, the Holy Roman Empire was dissolved and the number of independent territorial units drastically reduced. The remaining duchies, principalities, and kingdoms joined together as the Confederation of the Rhine (except for Austria, Prussia, Holstein and Pomerania). France annexed the west bank of the Rhine, which became the northeast border of France between Basel and the Napoleonic Kingdom of The Netherlands, which was annexed by France in 1810. Although the Congress of Vienna (1815) redrew the political map of Europe, changes within the area right of the Rhine were small except for Prussia gaining major territories along the Lower and Middle Rhine that included Rhineland and Westfalia. After the Franco-German War (1870–1871), the unified German Empire annexed Alsace and Lorraine and the Rhine became entirely German between Basel and Lobith. At the end of World War I (1918), both territories returned to France. The administration of Alsace and Lorraine by the Government in Berlin during World War II was a short episode. Today, all countries in the Rhine basin are members of the European Community except for Switzerland and Principality of Liechtenstein.

Chapter | 6 The Rhine River Basin

FIGURE 6.1 Digital elevation model (upper panel) and drainage network (lower panel) of the Rhine River Basin.

201

202

TABLE 6.1 General characterization of the Rhine River Basin Alpine Rhine Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions (Chapter 1) Dominant (25%) ecological regions Land use (% of catchment) Urban Arable Pasture Forest Natural grassland sparsely vegetated Wetland Freshwater bodies

1764 6155 7.3a 192.6 2.7 2 2

High Rhine

Upper Rhine

Middle Rhine

Lower Rhine

Delta Rhine

Aare (High Rhine)

Neckar (Upper Rhine)

Main (Upper Rhine)

Moselle (Middle Rhine)

902 30 148 33.4a 134.9 6.8 2 2; 70

348 62 967 50.1a 73.5 8.6 1 70

336 41 810 64.4a 81.1 9.0 2 70

202 18 836 72.4a 79.7 9.0 2 6; 70

12 25 347 >72.4 76.4 9.2 1 6

1067 17 606 17.6a 148.9 6.1 2 2; 70

432 13 950 4.7b 75.7 8.6 1 70

345 27 251 7.1c 65.5 8.2 1 70

342 28 133 10.3d 84.1 9.1 1 70

1.9 2.5 8.6 22.6 37.4 26.3 0.1 0.5

4.4 20.7 19.9 31.8 11.5 6.7 0.3 4.7

8.9 43.7 7.1 38.4 1.2 0.0 0.0 0.5

6.8 36.0 16.4 38.5 1.3 0.0 0.0 0.6

18.3 38.4 12.7 27.9 0.5 0.0 0.0 1.0

11.5 31.5 34.8 8.6 1.8 0.2 1.0 10.2

3.2 17.7 18.5 28.1 16.6 11.2 0.1 4.6

10.2 44.2 8.4 35.8 1.2 0.0 0.0 0.1

6.9 46.3 7.3 38.1 0.8 0.0 0.0 0.3

6.7 36.6 17.7 36.5 1.3 0.0 0.1 0.7

Protected area (% of catchment)

0.0

0.4

0.2

0.3

1.0

0.9

0.4

0.0

0.0

0.5

Water stress (1–3) 1995 2070

2.0 2.1

1.9 2.0

2.0 2.1

2.0 2.0

2.0 2.0

2.1 2.2

1.9 1.9

2.0 2.1

2.0 2.1

2.0 2.0

3 3 n.d. n.d. 2 192 65 169

3 0 n.d. n.d. 3 380 30 780

3 0 n.d. n.d. 4 242 28 047

3 0 n.d. n.d. 3 150 23 915

Fragmentation (1–3) Number of large dams (>15 m)f Native fish speciesg Non-native fish speciesg Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person)

3 0 17 2 0 57 46 469

3 0 31 5 3 229 56 429

3 0 39 17 15 299 28 296

2 0 30 11 5 172 23 819

2 0 33 4 14 668 25 639

1e 0 35 11 13 492 25 185

Catchment boundaries see Figure 6.1a. n.d. = no data. a

PART | I Rivers of Europe

Mean 1931–2003. MUV BW (2005). c BSUFV 2004. d IKSMS (2005). e Of the three Delta Rhine distributaries only the connection Waal-Nieuwe Waterweg is not impeded by weirs or dams. f No large dams along the main stems of the Rhine an the major Rhine tributaries except from the Aare (3 dams in the uppermost 9 km of the headwater reach g IKSR (2002b). For data sources and detailed explanation see Chapter 1. b

Chapter | 6 The Rhine River Basin

Up to the early 19th century, the economy in the Rhine catchment was primarily based on agriculture and relatively small-scale manufacturing, including mining and metallurgy in mountainous areas. The impacts of theses activities were mostly local. This changed dramatically with development of the coal and iron industry, particularly in Rhineland– Westphalia. The chemical industry along the Rhine from Rhineland–Westphalia to Basel and the tributaries Wupper, Main and Neckar, and rapid urbanization that manifested in the Frankfurt–Wiesbaden, Ludwigshafen–Mannheim and Basel further increased human impacts in the catchment. In the German part of the Rhine catchment, the population increased between 1819 and 1970 from 5.4 to 32 million (Kalweit 1976). As a consequence, the Rhine became increasingly affected by domestic and industrial sewage. The first sewage treatment facility was established in 1887 in Frankfurt and more cities followed, but these efforts did not keep pace with the growing wastewater production. Moreover, authorities were hesitating in imposing restrictions believed to impede industrial growth (Cioc 2002). Until the early 20th century, the impact of pollution was locally limited in the High, Upper and Middle Rhine reaches. The entire Lower Rhine suffered from heavy pollution, primarily from sewage outfall from the industrial centres in the Ruhr district. Water quality continued to deteriorate until the mid 1970s, although a short recovery period after World War II resulted from the destruction of industrial and urban sanitary facilities. It also became increasingly difficult to withdraw drinking water from Rhine because of high salinity resulting from the Alsatian potash mines dumping wastes into the river. The need to handle general pollution issues lead in 1950 to the establishment of the International Commission for the Protection of the Rhine (ICPR) in which all riparian states were represented. The Bern Convention of 1963 became the legal foundation of the ICPR, to which the European Community became affiliated in 1976. The Convention on the Protection of the Rhine against Pollution (Bern 1999), replacing the conventions of 1963 and 1976 (Convention on the Protection of the Rhine against chemical pollution), also dealt with ecological issues and flood risk management. In 2001, the Conference of Rhine Ministers in Strasbourg adopted a program for sustainable development of the Rhine (‘Rhine 2020’). This program aimed to combine ecology with flood prevention, surface and groundwater protection, and comparably considers ecological, economic and social aspects. The International Commission for the Hydrology of the Rhine basin (CHR/IKHR) was founded in 1970 and aimed to expand knowledge on the hydrology in the Rhine basin, contribute to the solution of cross-border problems, and develop joint hydrological measures for sustainable development of the Rhine basin. Member states of the CHR are Austria, France, Germany, Luxembourg, The Netherlands, and Switzerland. On 1 November 1986 during a warehouse fire of the Sandoz company in Schweizerhalle near Basel, about 20 tons of pesticides, dyes, solvents, raw and intermediate chemicals

203

were flushed into the Rhine and, over a distance of 400 km, killed all fish and other organisms, and prompted a drinking water alert from the Swiss border to The Netherlands. This disaster led the ICPR to set up the Rhine action program with ambitious water goals such as reducing the discharge of noxious substances and restoring the rivers original flora and fauna. Many of these goals have been met. Noxious substances were cut by 70–100% and heavy metals were significantly reduced. Still problematic are nitrogen, pharmaceuticals, and hormone active substances, but within a period of 30 years the water quality of the Rhine experienced a significant improvement (see Section 6.5.3). Between 1970 and 1990, 40 billion Euros were spent for installation of new and efficient sewage treatment facilities. In the 19th and 20th centuries, river engineering driven by flood protection, agricultural land reclamation, and navigation transformed the Rhine from a morphological nearnatural state to a confined channelized river. This affected the Alpine Rhine as well as Upper, Lower and Delta Rhine. Before the 19th century, the impact of flood protection on river morphology was usually local, except for the Lower Rhine and Delta Rhine (Table 6.2). Land use in floodplains already resulted in the Middle Ages to the loss of floodplain forests along the Lower Rhine (Tittizer & Krebs 1996). Before the late 18th century, humans were highly effective in modifying vegetation, but lacked the technical and socioeconomic resources necessary for the realization of large river training projects (Vischer 2003). The Rhine was used for the transport of goods in prehistoric times, but during the Roman period it became an important trade route (B€ocking 1980). Initially, it was the Roman fleet operating on the Rhine during the wars against Germanic tribes. Later, ports and quays to unload goods from barges and rafts were established in prosperous towns along the Rhine. With the beginning of invasions by Germanic tribes, trade and navigation on the Rhine started to decline and presumably ended before it resumed during the Carolingian period. Until the 19th century, rapids and shifting gravel or sand bars imposed major physical restrictions on navigation. In addition, the patchwork of independent territories along the river severely hampered navigation through numerous and often arbitrary restrictions, duties and privileges. Imposing tolls and taxes on ships and cargo was a common practice along the entire river since the Romans. Several castles along the Middle Rhine are a testimony of the medieval toll-collecting practices. Navigation was dominated by downriver transport by rafts, barges and sailing boats. For upstream transport, barges had to be towed by horse- or manpower, which required the maintenance of towing paths along the river banks. In 1815, the principle of freedom of navigation on international waterways was established in the Final Act of the Congress of Vienna. To enforce common rules and communication between the riparian states (Prussia, Hesse, Nassau, Baden, Bavaria, The Netherlands and France), the Central Commission for the Navigation of the Rhine (CCNR) was constituted

204

PART | I Rivers of Europe

TABLE 6.2 Major human interventions in the Rhine Delta since the Middle Ages (Lenders 2003; Ten Brinke 2005) Period AD

Intervention

1150–1450 1570–1600 1595–1680 1639–1655 1600–1900 1700 1707 1727–1734 1775–1782

Construction of primary dikes Creation of connections between rivers Meuse and Waal Construction of groines at Rhine bifurcation points Meander cut-off in river Waal Construction of summer dikes Engineering work on Rhine branches Waal and IJssel Opening of Pannerdensch Kanaal Closing of Waal–Meuse connection at Heerwaarden and Voorn Meander cut-off in Waal, new bifurcation of Pannerdensch Kanaal into Nederrijn and IJssel and modification of bifurcation at Pannerdensche Kop Digging of the Nieuwe Merwede and opening Nieuwe Waterweg (Rotterdam) First river training at Bovenrijn, Waal, Pannerdensch Kanaal, Nederrijn, Lek and IJssel Modification of the IJssel river mouth Meander cut-off and correction of river bends in Nederrijn Second river training at Bovenrijn, Waal, Pannerdensch Kanaal, Nederrijn, Lek and IJssel Third river training at Bovenrijn, Waal, Pannerdensch Kanaal, Nederrijn, Lek and IJssel Digging of Meuse–Waal canal (Nijmegen) Construction of Amsterdam–Rijn Kanaal and modification of Pannerdensch Kanaal Construction of three weirs in the rivers Nederrijn–Lek Meander cut-off in the river IJssel Delta project with closure of former estuary Haringvliet and the storm-surge barriers in the Oosterschelde and Nieuwe Waterweg Large-scale sand and gravel excavations

1850–1870 1850–1885 1869–1885 1874–1906 1888–1890 1912–1934 1927 1952–1953 1954–1967 1954–1969 1961–1997 1900–2006

(1816). However, the prospect of an open Rhine was not generally appreciated because some players faced to lose their private privileges and transfer rights. After a partial solution to these conflicts (Mainz Acts 1831), the remaining issues were finally resolved in 1868 (Mannheim Acts) and free navigation on the Rhine became a reality. As part of the Versailles treaty of 1919, the CNNR was moved from Mannheim to Strasbourg, and Belgium, Italy and Switzerland became Committee members along with The Netherlands, Germany and France, which was excluded between 1871 (end of the Franco-German War) and 1918. Modern Rhine navigation began with the appearance of self-propelled ships. The first steamboat ‘Prince of Orange’ arrived from Rotterdam in Cologne in 1816, and the first steamboats reached Strassbourg in 1825 and Basel in 1832. Steam-powered tugs already towed barges around 1840. Diesel-powered freighters appearing in the 1920s displaced the tug-barge systems into the 1950s when the first push-tow units started to navigate on the river (B€ ocking 1980). Today the Rhine is navigable between the sea (Rkm 10331) and Rheinfelden (Rkm 147). All major natural obstacles impeding navigation have been removed, and the only temporary constraints on navigation are flow extremes. The wish to expand navigation routes across catchment boundaries led to the construction of navigation canals that

1. The kilometration (mileage) of the Rhine begins in Constance at the outflow of upper Lake Constance at Rkm 0.0 and ends in Hoek van Holland at Rkm 1032.8.

connected the Rhine with the rivers Scheldt (1832), Rh^ one (1833), Seine (1853), Elbe (1938) and Danube (1843 and 1992). The first attempt (793 AD) to overcome the divide between the Main River and the Danube failed (Fossa Carolina). In 1843, Bavaria finally completed a canal connecting the Main River with the upper Danube, but water shortage and numerous locks impeded navigation from the beginning. From 1960 to 1992, the connection of the Main and Danube was upgraded to a modern waterway. The 55-m wide and 4-m deep Main–Donau–Kanal is suitable for navigation with pushtow units. These navigation canals also opened immigration routes for aquatic organisms from different zoo-geographic provinces (Bij de Vaate et al. 2002; Leuven et al. 2009).

6.2. BIOGEOGRAPHIC SETTING The Rhine basin contains parts of three biogeographic regions – Alpine, Continental and Atlantic – and four ecoregions – conifer and mixed forests of the Alps, western European broadleaf forests, and the northern and southern temperate Atlantic region. The range of latitude extends from Atlantic climatic conditions in the Rhine delta to a moderate continental influence in the southeast Alpine forelands. It spans a fairly wide altitudinal range from sea level to the cryosphere of the high Alpine mountain range. At altitudes above 2000 m asl, alpine vegetation (grasslands) prevails. In the transition zone from alpine grasslands to timberline, vegetation is characterized by dwarf shrubs. Subalpine forests dominated by fir (Picea abies) extend between 1200 and 2000 m asl. Common trees in the forests of the

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FIGURE 6.2 The Cenozoic evolution of the Rhine drainage after Preusser (2005) and Quitzow (1976).

Alps, Black forest, Jura and Vosges (600–1600) include spruce (Picea abies), fir (Abies alba), beech (Fagus silvatica), sycamore (Acer pseudoplatnus) and ash (Fraxinus excelsior). Different types of beech forests and mixed beech forests prevail at lower elevations. Floodplain vegetation includes willow (Salix spp.) and poplar (Populus nigra, P. alba) forests in frequently inundated areas. In areas less influenced by inundation, floodplain forests include oak (Quercus robur), ash and elm (Ulmus spp.) (Schnitzler 1994).

6.3. PALAEOGEOGRAPHY The Rhine is the only large Alpine river flowing north to the sea, which resulted from a complex geological history. Over large parts, the river follows the European Cenozoic Rift System, which crosses different tectonic domains between the Mediterranean and North Sea (Preusser 2005). Crust movement (uplift, rift formation, large-scale tilting) and glaciation modified the Rhine course since the early Neogene (Figure 6.2). The uplift of the Black Forest and Vosges during early phases of the Alpine orogeny and subsequent rift valley formation (Upper Rhine Graben) founded the present Rhine system. The area that later became the Rhenish Mountains, rivers developed that drained north and south. As a consequence of rift formation and uplift, a precursor of the Rhine started to flow across the Rhenish Mountains, thereby directing the Moselle and Lahn Rivers to the north. With subsidence of the Upper Rhine Graben, Rhine headwaters moved east. In the late Pliocene, the Aare River, which was a Danube tributary, started to flow west along the depression between the Jura Mountains and Black Forest. The Main and Neckar Rivers increased their watershed size by capturing tributaries of the upper Danube. The loss of the upper Rh^ one catchment, which was part of the Aare drainage, presumably occurred during the Pleistocene. The period between the late Pliocene and late Pleistocene is characterized by 15 major glacial advances from the

Alps into the northern forelands (Schl€uchter 2004). The advancing Alpine glaciers of the Mindel Ice Age crossed the Rhine/Danube and directed meltwaters to the west. Subsequent eastward regressive erosion of the High Rhine and its tributaries finally tapped the Alpine Rhine, which earlier drained to the Danube. During the Riss Ice Age, a branch of the Meuse River originating in the Vosges was directed to the north and became the upper Moselle River. The capture of the most southern headwater river of the Danube by a High Rhine tributary (Wutach River) occurred after the maximum of the W€urm glacial stage (20 000 years BP). Glacio-fluvial erosion also opened the top of a large karstic system near the Danube/Rhine, and today 65% of the water of the upper Danube flows through a karstic drainage towards the Rhine. During the Pleistocene, 600 000–10 000 years BP, six major Ice Ages occurred in northwestern Europe (e.g., Berendsen & Stouthamer 2001). The sea level dropped 120 m and much of the continental margins became exposed. In the early Pleistocene, the Rhine followed a course to the northwest, through the present North Sea. During the socalled Elsterien glaciation (420 000 years BP), the northern part of the present North Sea was blocked by ice and a large lake developed that overflowed towards the English Channel. There is evidence that two catastrophic floods (with an estimated discharge of 0.2 106–1 106 m3/s and the largest on Earth) in 425 000 and 200 000 BP breached the Weald-Artois Anticline, which separated the North Sea from the English Channel, and finally reorganized the paleo-drainages of northwest Europe (Gupta et al. 2007). The last flood re-routed the Rhine–Thames river system through the English Channel, thereby forming the Channel River, one of Europe’s largest paleo-drainages during the quaternary low sea-level stands. The mouth of the Channel River, which included waters of the Seine River, was located near Brest (France). During interglacials, when sea level rose to approximately the present level, the Rhine developed a delta in what is now known as The Netherlands. During the last Ice Age (70 000– 10 000 years BP), at the end of the Pleistocene, the lower

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Rhine flowed roughly west through The Netherlands, then southwest through the English Channel, and finally to the Atlantic Ocean (Berendsen & Stouthamer 2001). The English and Irish Channels, the Baltic Sea and the North Sea were still dry land, mainly because the sea level was 120 m lower than today. At about 5000 BC, flooding and erosion began to open the English Channel. Most of the Delta Rhine was not under ice during the last Ice Age. Tundra with Ice Age flora and fauna stretched across middle Europe from Asia to the Atlantic Ocean. Such was the case during the Last Glacial Maximum, 22 000–14 000 years BP, when ice covered Scandinavia and the Baltics, Britain and the Alps, but left the space between as open tundra. Loess, or wind-blown dust, over that tundra settled throughout the Rhine valley, contributing to its current agricultural value. Meltwater to the ocean and land subsidence caused inundation of the former coast of Europe. Today, the sea level is still rising at a rate of 1–3 mm per year.

6.4. PHYSIOGRAPHY, CLIMATE AND LAND USE 6.4.1. Geological Structure and Relief The Rhine basin (average elevation 426 m asl), sloping from south to north, spans parts of three physiographic regions: (1) European highlands with the Alps, including their foothills and foreland, (2) the central upland and plateau regions, which includes the northeast Jura range, the Vosges, Black Forest, Rhenish mountains and South German Scarplands and (3) the northern lowland with the coastal plain. The Alps, including their northern foothills, contribute about 16 400 km2 (8%) to the Rhine catchment. The geologically young mountain range of the Alps is characterized by a rugged topography, steep slopes, and deeply incised valleys. Mountains exceeding 3000 m asl typically have snow or ice covered summits. The highest peak of the Rhine catchment is the Finsteraarhorn at 4274 m asl. Granitoids prevail in the headwaters of the Rhine and Aare, and limestone of the helvetic nappes in the northern front range. The adjacent northern Alpine foreland, a sedimentary basin simultaneously formed with the uplift of the Alps and filled with debris of the rising mountain range, extends to the southern fringes of the Swiss Jura and Suebian Alb. This area, shaped by several Pleistocene glacial cycles, is covered by moraines, gravels, sands and silt; Tertiary sediments still outcrop at several sites. The landscape is characterized by hills, wide valleys and lakes, the largest is Lake Constance. The South German Scarp land is made up of Triassic and Jurassic sediments slightly dipping east, with denudation surfaces, cuestas, escarpments, basins and valleys (Koster 2005a). Elevations range from 200 to 1000 m asl. Karstic features such as dry valleys, sinkholes or karst springs occur where limestone prevails.

PART | I Rivers of Europe

The Central European Uplands within the Rhine catchment include the rift and valley ranges of the Vosges, Black Forest, Odenwald, Rhenish Slate Mountains, and NaheSaar Uplands. Relief is characterized by planation surfaces, cuestas, hogbacks, basin and deeply incised valleys. Black Forest and Vosges consists of highly metamorphic and granitic rocks partly covered by Permian and Triassic sediments. At elevations over 1400 m asl, Vosges and Black Forest became partly glacierized during the Pleistocene. The Upper Rhine Graben is a 310-km long and 35-km wide spectacular subsidence zone within the European Cenozoic Rift system (Illies 1972). The rift valley is fringed on the right side by the Black Forest, Odenwald and on the left side by the Vosges and Palatinate uplands. The base of the Tertiary valley fill ranges from 2000 to 3000 m and Quaternary deposits reach up to 200 m. Landforms include Pleistocene river terraces and alluvial fans extending from the rift flanks. The Rhenanian Slate mountains are the remnants of the Hercynian Mountains, with predominantly Devonian and Carboniferous slates, greywackes and limestones (Koster 2005a). The folded and metamorphosed Paleozoic rocks form an extensive mountainous plateau deeply dissected by the Rhine and its tributaries. The Lower Rhine and Delta Rhine are part of the northern European Lowlands. The Lower Rhine embayment is currently one of the most active sectors of the European Cenozoic rift system (Sch€afer et al. 2005). Fault zones fragmenting tertiary sediments in horst and graben extend from southeast to northwest. Quaternary glacial and fluvial deposits cover tertiary sediments and respective landforms include river terraces (particularly in the southern part) and moraines. The area is relatively flat with a relief typically of a few ten meters.

6.4.2. Climate General climate of the Rhine basin is determined by its location in a temperate climate zone characterized by frequent weather changes. Precipitation occurs at any time of the year. From the sea to the east and southeast of the catchment, the climate gradually changes from maritime to more continental. General weather patterns during winter are primarily influenced by weather dynamics in the northern and eastern Atlantic, and in the North Sea. The Eurasian land mass also favours the formation of relatively persistent cold anticyclones over northeast Europe and western Russia, which temporarily reduce the influx of relatively warm humid air from the Atlanic. Temperature and precipitation vary considerably with altitude and local topography. The mean annual temperature of the Rhine basin is 8.3 C, 11.2 C in the thermally favoured valley of the Upper Rhine, and <0 C at elevations >3000 m asl. Precipitation in the basin averages

Chapter | 6 The Rhine River Basin

945 mm/year. The orographic effect of mountain ranges or uplands results in heterogeneous precipitation patterns at different spatial scales. In the upper (higher) basin (High Rhine and Alpine Rhine), yearly precipitation is 1500 mm. Precipitation is high on the west slopes of mountain ranges such as the Vosges (1500–2200 mm/ year) and Black Forest (1860–1960 mm/year) and peaks at the northern front range of the Alps at 2000–3500 mm (Hendl 1995; Schwarb et al. 2001). In contrast, the area in the rain shadow of the Vosges only receives 515–615 mm/ year. In the Alpine parts of the basin about 30% of the annual precipitation falls during summer (June-August); seasonal differences are slightly less pronounced in the lower basin.

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FIGURE 6.3 Longitudinal profile of the Rhine. Modified from Mangelsdorf et al. (1990).

6.4.3. Land Use About 50% of the Rhine basin area (185 263 km2) consists of agricultural area (pasture and arable land), followed by forests (31.7%), urban areas (8.8%) including 50 cities with >100 000 people, natural grasslands (4.1%), freshwater bodies (2.6%), sparsely vegetated areas (2%), and wetlands (0.2%) (Table 6.1). Forest cover is maximum in the Middle Rhine sub-basin (38.5%) and minimum in the Delta Rhine (8.6%). Agricultural areas range from 11.2% in the basin of the Alpine Rhine to 66.2% in the Delta Rhine. The urban area is maximum in the Lower Rhine basin with 18.3%.

6.5. GEOMORPHOLOGY, HYDROLOGY AND BIOGEOCHEMISTRY 6.5.1. Geomorphology of the Main Corridor The longitudinal profile of the Rhine is characterized by two additional base levels of erosion apart from the sea (Mangelsdorf et al. 1990). The first level is Lake Constance, where the Alpine Rhine deposits its sediment load, and the second is the quartzite reef at the beginning of the Middle Rhine section near the town of Bingen (Figure 6.3). Upstream of each base level, the river attempts to establish a concave equilibrium curve. Valley side-slopes confine major parts of Alpine headwaters, the High Rhine, and Middle Rhine. Before major river engineering works, the river was braiding or meandering in naturally unconfined reaches of the Alpine, Upper, Lower and Delta Rhine. The catchment area of the Alpine Rhine has an area of 6155 km2 with elevations ranging from 395 m (Lake Constance) to 3614 m asl (T€ odi). About 1.4% of the catchment is covered by glaciers, most of which are rapidly receding. The two major headwaters of the Rhine, Vorderrhein and Hinterrhein, lie on an old Oligocene relief (Keller 2006). The catchment of the Vorderrhein consists of granite, granodiorite and gneiss of the Gotthard massif, limestone, sandstone and marl of the Helvetic nappes that forms the northern boundary of the main valley, and gneiss, schist, quarzite

and sandstone of the Penninic nappes in the northeastern part of the valley. Granite, gneiss, granodiorite, schists and triassic-dolomite of the Penninic and East-Alpine nappes characterize the geology of the Hinterrhein catchment. The formation of the Alpine Rhine valley began at the end of the Miocene when a shear fault zone opened a new valley to the north (Handke 2006). With the retreat of the Rhine Glacier at the end of the last Ice Age (16 000 BP), Lake Constance extended about 80 km into the valley of the Alpine Rhine. The Rhine and its tributaries rapidly filled this lake with sediments. In Roman times, the lake-shore was only 1–2 km south of the present shore line (Keller 2006). The geology of the Alpine Rhine catchment is characterized by limestone, sandstone and marl of the Helvetic nappes, and granite, gneiss, granodiorite, schists and triassic-dolomite of the Penninic and East-Alpine nappes. Near Lake Constance, Tertiary molasse sediments (conglomerates, sandstone) prevail. The source of the 71.5 km long Vorderrhein is Lake Toma, a small lake at 2343 m asl on the east slope of the Gotthard massif in the central Swiss Alps, from where it flows east to the confluence with the Hinterrhein near Reichenau (583 m asl). Lake Toma is considered to be the source of the Rhine. After an initial steep descent, the Vorderhein flows through a relatively wide valley bordered by mountains with elevations >3000 m asl. Side-slopes and sediment deposition of tributaries naturally confine the river at many sites, but where the valley is wider the river braids. Between Illanz and Reichenau, the river has carved deep into the debris of a huge rockslide occurring 9487 years BP and mobilized 12 km3 of Jurassic calcareous rock matter (Photo 6.1) (Schneider et al. 2004; Wassmer et al. 2004). At many sites the Vorderrhein has been channelized to gain and protect land for housing, transportation and agriculture (pasture). This reduced the length of the original braided reaches from 23 to 6 km. The 57-km long Hinterrhein begins at the terminus of the Paradis Glacier (2400 m asl) of the Rheinwald massif (maximum elevation 3402 m asl) and flows east for about

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PHOTO 6.1 The Vorderrhein at Versam. The river is incised in the debris of prehistoric rockslide. (Photo U. Uehlinger).

30 km before turning north. Two steep gorges (Roffla and Via Mala) divide the river corridor in three sections with one or more channels. For the same reasons as in the Vorderrhein, major parts of braided reaches were lost (thalweg reduction from 28 to 11 km). Between Via Mala and the confluence, where the valley is relatively wide, river engineering in the 19th century forced the Hinterrhein into a straight narrow channel. Only the last 4.5 km, characterized by a widely natural morphology, are listed today in the Swiss inventory of floodplains of national importance. Near the town of Reichenau (582 m asl), Vorderrhein and Hinterrhein merge to become the Alpine Rhine, which flows into Lake Constance (396 m asl). In the upper 9 km of the 93 km long Alpine Rhine valley, the channel is deeply incised in the 1.5 km wide, valley floor (slope 3 m/km). The channel is about 60 m wide with coarse substrate prevailing (d90 = 20 cm). Between Reichenau and Lake Constance, the mean diameter of bed sediment particles decreases from about 10 to 2 cm. In the adjacent 71-km long reach, the Alpine Rhine was originally a braided river; at some locations the active channel width presumably exceeded 500 m. The tributaries Plessur (mean annual discharge (Qmean) 8 m3/s), Landquart (Qmean 25 m3/s1) and Ill (Qmean 66 m3/s) supply large amounts of sediments. The valley floor with slopes ranging from 1 to 3 m/km varies between 3 and 4 km. In the last reach before Lake Constance, the valley floor becomes up to 15 km wide and slope decreases to 0.6 m/km. Before regulation of this reach, channel patterns reflected the transition from a braided to a meandering river with channel widths originally ranging from 120 to 400 m. Today, channel morphology and plan view of the Alpine Rhine primarily reflects the comprehensive river engineering works of the 19–20th century aimed to provide flood protection for agricultural land and human settlements (Vischer 2003).

The channel has a trapezoidal profile (width at the base 100 m) with a boulder riprap protecting the base of flood embankments between the confluences Rhine–Landquart (20 km downstream of Reichenau) and Rhine/Ill River (66 km downstream of Reichenau). Alternating gravel bars with backwaters are a typical morphological feature of this reach (Photo 6.2). The only remnant of the original braided reach is the 2.5-km long Mastrilser Rheinaue. Downstream of the Ill confluence, the shape of the channel cross-section becomes a double-trapezoid. The width of the main channel decreases downstream from 80 to 40 m; distances between the flood embankments vary between 200 and 400 m. Alternating bars are lacking because of the reduction in slope, sediment caliber and channel width. The first river engineering works intended to enhance sediment transport but the channel aggraded, and as a consequence, increased the flood risk. Therefore, the channel was narrowed and gravel extracted. However, enhanced transport capacity and excessive gravel exploitation, in particular, (sediment transport was overestimated because the decrease in sediment caliber by abrasion proved to be smaller than assumed) resulted in channel erosion locally by several meters (Zarn et al. 1995). Efforts to stabilize the riverbed included the construction of boulder ramps and local channel-widening, in addition to a major reduction in gravel extraction. Today, the delta of the Alpine Rhine annually grows by 23 m into Lake Constance primarily due to the deposition of fine sediments since coarse sediments (gravel) are extracted near the river mouth. The separation of the Rhine by dikes from its former floodplain required the construction of side channels as recipients of side tributaries and groundwater. These channels drain parallel to the channelized river before they discharge into the Rhine or directly into Lake Constance.

Chapter | 6 The Rhine River Basin

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PHOTO 6.2 Middle section of the Alpine Rhine with alternating gravel bars. (Photo U. Uehlinger).

Between the delta of the Alpine Rhine and the beginning of the High Rhine, the continuum of the Rhine main stem is interrupted for about 60 km by Lake Constance. This large naturally formed lake consists of two basins, the upper and lower Lake Constance, connected by a short (4.4 km) Rhine reach called ‘Seerhein’. The respective volumes and surface areas of both lakes are 47.6 and 0.8 km3 and 472 and 62 km2, respectively. The High Rhine begins near the town Stein am Rhein as the outflow of lower Lake Constance and drains a catchment of 30 148 km2 that includes the Aare catchment and the catchments draining into Lake Constance (without the Alpine Rhine). Elevations range from 246 m asl in Basel

to 4274 m asl in the Aare catchment. The 142 km long High Rhine flows west from the lake (390 m asl, Rkm 22.9) to Basel (Rkm 165). The river is naturally confined by river terraces and the side-slopes of the Black Forest and Jura Mountains. Floodplains are lacking or restricted to narrow strips (Photo 6.3); the only significant floodplains originally existed at the Rhine–Thur and Rhine–Aare confluences. Right-hand tributaries drain the south slopes of the Black Forest and parts of the southwestern spurs of the Swabian Alb. Left-hand tributaries include the two major High Rhine tributaries, Aare (Qmean 559 m3/s) and Thur Rivers (Qmean 48 m3/s), and smaller rivers draining the northeast Swiss PHOTO 6.3 High Rhine reach at Rkm 38 upstream of Schaffhausen. (Photo U. Uehlinger).

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Plateau and parts of the Jura Mountains. Downstream of the town of Schaffhausen (Rkm 45), the river is incised in glacial river terraces. The channel form is typically straight except for a double meander partly incised into the bedrock at Rheinau (Rkm 56). Channel slopes range from 0.03% in the upper 21-km long lake outlet reach to 0.8–1.3% in downstream reaches. Channel width varies between 120 and 150 m upstream of the Rhine–Aare confluence and averages 200 m downstream. Near-natural channel morphology, and hydraulic conditions prevail in most parts of the free-flowing reaches. Substrate is dominated by gravel; bedrock outcrops (Jurassic limestone or Black Forest granite) at a few sites, resulting in the formation of the 21-m high Rhine Falls near Schaffhausen and rapids such as upstream of Waldshut at Rkm 98 and in Laufenburg at Rkm 122. The Laufenburg rapids once hosted a spectacular salmon run that was lost because of dam construction. The relatively steep and narrow High Rhine valley offers favourable conditions for the production of hydropower. The first run-of-river power plant was completed in 1866 in Schaffhausen. The energy produced was transmitted by steel cables (mechanical transmission) to factories that lined the river before the facility was upgraded with electric generators in 1898. Between 1898 and 1966, 10 additional hydroelectrical power plants were installed (the plant Albruck/ Dogern has a 3.5-km long diversion canal) producing today 4400 106 kWh per year. The once swift flowing river is now a chain of impoundments (Photo 6.4) with only three major free-flowing reaches that include the outlet of lower Lake Constance (12 km), a reach downstream of the power plant of Rheinau (5 km long), and a reach upstream of the Rhine–Aare confluence (11 km long). The sediment load of the High Rhine is naturally low because of the large lakes fringing the Alps retain sediments of the Rhine and

PART | I Rivers of Europe

its major tributary Aare. Bedload transport is influenced by the minor sediment supply and the reduced transport capacity due to the impounded reaches upstream of the 11 power plants. At Basel, the Rhine enters the Rhine Graben rift valley and flows now as the Upper Rhine north for 300 km. Downstream of Mainz, it turns west and after 33 km reaches the southern fringe of the Rhenanin Mountains at Bingen (Rkm 528.5). The area of the Upper Rhine catchment is 62 967 km2, including the catchments of the Neckar and Main Rivers. Elevations range from 1493 m asl (Black Forest) to 88 m asl (Bingen). The Rhein Graben rift valley is fringed on the right by the mountain ranges of the Black Forest and Odenwald and on the left by the Vosges Mountains and Palatinate plateau. From Basel to Mainz, the width of the rift valley ranges from 30 to 40 km (Figure 6.1a). Between Basel and Strassbourg (Rkm 294), the Rhine was originally a braided river within a 2–4 km wide floodplain (slope 0.1%) and 220-km long thalweg. The reduction in valley slope downstream of Strassbourg turned the river into a meandering system. The meandering reach extended from Karlsruhe (Rkm 362) to Mainz (Rkm 498) and included numerous island sandbars and oxbow lakes. The width of meanders ranged from 2 to 7 km and the valley slope averages 0.025%. Downstream of Mainz, where the valley is naturally confined by spurs of the Palatinate upland and Taunus range, the floodplain is only about 1 km wide and the straight channel includes islands and sand bars. River engineering works of the 19th and 20th centuries completely changed the morphology of the Upper Rhine. Over several centuries, the growing population in the floodplain took protective measures against the river, which constantly changed its course. Artificial meander cuts date since PHOTO 6.4 High Rhine (Rkm 106) near the nuclear power plant of Leibstadt. The river is impounded by the dam of the Albruck–Dogern hydropower plant. (Photo U. Uehlinger).

Chapter | 6 The Rhine River Basin

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PHOTO 6.5 Upper Rhine: The Grand Canal d’Alsace (Rkm 216) near Breisach. (Photo U. Uehlinger).

the 14th century, but the effect of such actions did not affect natural river dynamics. Settlements often had to be abandoned and rebuilt at safer locations (Musall 1982). Some of these problems disappeared with regulation of the Upper Rhine beginning in 1817 under the direction of the Badenese engineer Johann Gottfried Tulla (1770–1828) and continuing under his successors until the end of the 19th century. The primary goal of the project was floodplain reclamation, fixation of the international border between France and the Duchy of Baden, and improved flood protection of settlements. Channelization by cuts, excavations and embankments reduced the thalweg between Basel and Worms (Rkm 443) by 81 km (23% of the original length). More than 2000 islands disappeared and an area of about 100 km2 was reclaimed. The shortening of the river and narrowing of the channel to a width of 200–250 m enhanced vertical erosion. In the former braided reach, the river deeply cut into its bed, in the upper 30 km up to 7 m. At Istein (Rkm 178), it reached the bedrock of a cliff, thereby forming rapids and impeding navigation between Mannheim and Basel. With incision of the riverbed, the water table decreased and turned former wetlands in to arable land, which now require irrigation for agricultural productivity. The construction of the Grand Canal d’Alsace (1928–1959), a concrete canal parallel to the left bank of the Rhine (international border), was aimed to produce hydropower and improve navigation (Photo 6.5). The 130 m wide and 9 m deep canal extends from the Swiss border to Breisach (Rkm 226) and encompasses four hydropower plants. During baseflow, only 15– 20 m3/s remain in the old Rhine (IKHR 1993), which accelerated the lowering of the water table. In the 61-km long reach downstream of the Grand Canal, four additional power plants were completed between 1963 and 1970. The loop diversion design of these plants, which leaves the water in the

riverbed for most of the reach, was intended to mitigate the rapid loss in the water table. Continuing erosion problems resulted in the construction of two additional power plants (run-of-river plants without loop diversion) at Rkm 209 and 335. Downstream of the last power plant (Iffezheim), 180 000 m3 gravel must be added annually to the river to prevent further channel degradation (IKSR 1993). After 180 years of river engineering, the Upper Rhine is primarily a straight single-thread river with uniform crosssections, protected banks and dikes (Photo 6.6). All the islands except for a few large ones disappeared. Near power plants, dikes top over the adjacent former floodplain by >10 m. Bed sediments include gravel in the upper reaches, and fine gravel and sand in the former meandering reach. Channel widths range from 130 to 300 m between Basel and the last power plant, 250–300 between Karlsruhe and Mainz, and from 350 to 500 m between Mainz and Bingen. The width of the uniformly deep navigation channel within the channel varies between 100 and 450 m. The catchment of the Middle Rhine covers an area of 41 810 km2 with elevations ranging from 43 m asl near Bonn to 880 m asl in the Taunus Mountains. It includes the Rhenanian Slate Mountains, remnants of the Hercynian Mountains, with predominantly Devonian and Carboniferous slates, greywackes and limestones (Koster 2005a). Parts of the uplands are covered by volcanic deposits originating from Tertiary and Quaternary volcanic activity. The most recent eruption dated 11 000 years BP (Schmincke et al. 1999). The Rhenanian massif is dissected by the Rhine from south to north, the River Moselle from southwest to northeast, and River Lahn from northeast to southwest. The Middle Rhine begins at Bingen (Rkm 529), where the Rhine turns north and enters a canyon-like reach characterized by a relatively steep gradient (0.04%) and narrow

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PHOTO 6.6 Upper Rhine near Rastatt at Rkm 340. (Photo U. Uehlinger).

channel (200–300 m) (Photo 6.7). From continuous upland uplift and subsidence of marginal areas, the Rhine deepened its valley by 200 m. The riverbed mainly consists of bedrock (Devonic schist and quartzite), forming reefs and some islands apart from gravel bars (Photo 6.8; gravel is added by the Nahe River merging with the Rhine at Bingen). Only some of the bed sediments transported at Mainz (Rkm 498) reach the Middle Rhine (IKSR 2005). Mid and point bars occur where the gradient is low. About 30 000 m3 sediment must be annually removed from the river to keep the navigation channel open. Sediment supply from the tributaries Moselle and Lahn stopped with the regulation of both rivers. Downstream of Koblenz (Rkm 591.5), the Rhine flows unconstrained for about 22 km through the Neuwied basin, a relatively small tectonic depression. From Andernach (Rkm 613), the Rhine continues in a straight channel to Bonn (Rkm 655), thereby cutting through the volcanic field of the East Eifel. About 12 900 years BP, a disastrous Plininan eruption of the Lacher See Volcano (7 km west of the Rhine) deposited large amounts of fallout tephra that congested the outlet of the Neuwied basin and formed a lake of 140 km2. The collapse of the tephra dam during the late stage of the eruption caused a catastrophic flood; respective deposits can be found as far as 50 km downstream (Park & Schmincke 1997). In contrast to the Alpine Rhine, Upper, Lower and Delta Rhine, the plan view of the Middle Rhine course was little affected by humans. River engineering in the 19th and 20th centuries aimed to improve navigation by primarily modifying channel cross-sections by removing cliffs (IKSR 1993). Up to the 1980s, the width of the navigation channel has been excavated or blasted to a depth of 2.1 m at baseflow (Q345) and widened to 120–140 m. This included the quartzite reef at Bingen, once the most infamous navigation obstacle on the

river. In some reaches, groynes including lateral ones were used to maintain baseflow depths. Railroad tracks and roads isolate the river from adjacent uplands by walls, particularly along confined reaches. The Lower Rhine flows from Bonn (Rkm 655) to the Dutch–German border (Rkm 858). It drains a catchment of 18 836 km2, including parts of the M€unster Embayment in the northeast and the Rhenanian massif in the south and southeast. On the right of the Rhine between the M€ unster Embayment and the Rhenanian massif is the Ruhr basin with up to 3000 m thick Upper Carboniferous coal bearing sediments extending into the southern North Sea (Henningsen & Katzung 2002). The coal contained in >200 seams fuelled the development of the Ruhr area from a rural area in the early 19th century to the largest heavy-industry landscape in western Europe in the first half of the 20th century. The Lower Rhine basin, a marginal marine rift basin extends into the northern spurs of the Rhenish Massif forming an embayment. The sediment fill of the basin contains siliclastic sediments with intercalated lignite (brown coal) originating from peat bogs formed during the lower and middle Miocene when the sea-level was high (Sch€afer et al. 2004). Today, the up to 100 m thick lignite deposits are extracted by opencast mining 20–40 km west of Cologne. The Lower Rhine, which drains parallel to the main tectonic basin faults, is fringed on both sides by river terraces. The complex terrace system is the result of several Pleistocene glaciations. In the hinging area between the uplifting area in Germany and the subsiding North Sea basin, that is at the border of the Lower Rhine and Delta Rhine, terraces have been little preserved (Bridgeland 2000). The valley slope decreases from 0.023% at the beginning of the reach to 0.008% near the Dutch–German border. Between Bonn and Leverkusen (Rkm 700), the river channel is

Chapter | 6 The Rhine River Basin

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PHOTO 6.7 Middle Rhine at St. Goar (Rkm 556). (Photo Klaus Wendling, Mainz).

relatively straight with widths varying between 250 and 500 m. The prevailing substrate is gravel, sand occurs locally. Downstream of Leverkusen, the Rhine originally turned into single channel meandering river for 75 km. Further downstream, the meandering channel also included side channels and many islands. Dominant substrate was fine gravel and sand.

Flood protection and improvement for navigation have been an issue along the Lower Rhine since the late Middle Age (Von Looz-Corswarem 1996). Efforts included attempts to fix the channel location with groynes, local bank stabilization, dyke construction, and cutting of meanders. River engineering in the late 18th century was aimed to standardize plan view and cross-sections that also included PHOTO 6.8 Middle Rhine. Stabilzied gravel island at Rkm 534 (Clemensgrund). (Photo K.M. Wantzen).

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PHOTO 6.9 Lower Rhine near Krefeld Uerdingen (Rkm 760). (Photo Marcel Sowade, Moers, Germany).

a major loss of islands. Under the direction of a Central Rhine River Administration (Zentrale Rheinstromverwaltung) constituted in 1851 under the Prussian government, the Lower Rhine was finally transformed to a waterway of uniform depth and width (Photo 6.9). Artificial meander cutting in the 18–19th centuries shortened the length of the thalweg by 23 km (IKSR 1993). The increased sediment transport capacity resulted in vertical erosion (locally up to 2 m), which was aggravated by gravel extraction, reduced sediment supply by tributaries, subsidence of the riverbed following mining, and scouring by ship propeller wash (IKSR 1993). In the 20th century, coal and salt mining below the river lead to depressions of the riverbed, particularly between Duisburg (Rkm 775) and Xanten (Rkm 824). These areas of human-induced subsidence, trap sediments and enhance erosion in downstream areas despite additions of mining debris. Downstream of the subsidence area, vertical erosion rates reach up to 3 cm/y (IKSR 2005). Today, the river is between 300 and 600 m wide, with riprap protected banks and numerous groynes fixing the uniform navigation channel (depth at low flow 2.5–2.8 m) (Photo 6.10). About 640 km2 of the original floodplain area of 900 km2 are now protected by dikes. The Holocene development of the Rhine delta has been reconstructed by Berendsen & Stouthamer 2000, using a large number of lithological borehole descriptions, 14C dates, archaeological artefacts and gradients of palaeochannels (cited by Koster 2005b). During this period, avulsion was an important process, resulting in frequent shifts of areas of clastic sedimentation. Palaeogeographic evolution of the Rhine delta is mainly governed by complex interactions

among several factors such as (1) location and shape of the palaeo-valley, (2) sea level rise, which resulted in back-filling of the palaeo-valley, (3) peat formation, which was most extensive in the western part of the back-barrier area, especially between 4000 and 3000 years BP, that more or less fixed the river pattern at that time and resulted in few avulsions, (4) differential tectonic movements, especially from 4500 to 2800 years BP when the rate of sea level rise had decreased. After 2800 years BP, sea level rise further decreased, and tectonics still may have influenced avulsions, but from then on other factors became dominant. (5) Increased discharge, sediment load and/or within-channel sedimentation. After 2800 years BP, river meanders of the Rhine show remarkable increases in wavelength, interpreted as a result of increased bankfull discharge and sediment load. Increased discharge may initially have been caused by higher precipitation. Alternatively, decreasing gradients (as a result of sea level rise) may have caused increased within-channel sedimentation and channel-widening, which would also lead to increased meander wavelengths. Other factors included (6) composition of the river banks. Meandering river channels tend to adhere to the sandy margins of the palaeo-valley, and high channel sinuosity is found in areas where river banks consisted of sand, (7) marine ingressions, for example, the 1421 AD St. Elizabeth’s flood caused large-scale erosion and created a wide estuary in the southwestern part of the fluvial deltaic plain of the Rhine and Meuse, and (8) human influence dominating the palaeogeographic evolution since about 1100 AD. There is evidence that since the last Ice Age humans locally cleared the forested floodplains in the Rhine

Chapter | 6 The Rhine River Basin

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PHOTO 6.10 The boundary Lower Rhine/Delta Rhine. The bifurcation of the Rhine in the Waal branch (right) and the Pannerdensch Kanaal (left), at the Pannerdensche kop (Rkm 867.5). (Photo Rijkswaterstaat, The Netherlands).

basin and put them to use for agricultural purposes (Bos & Urz 2003). The first settlers in the ‘lowlands’ of the Rhine delta found themselves in a poorly drained flat delta and floodplains intersected by streams, tidal inlets and small and large river channels (Havinga & Smits 2000). In the Rhine delta, human occupation of high ridges and river dunes along the water course already existed 6500 years ago (Groenman-van Waateringe 1978). People lived by hunting and fishing, and small dikes and flumes were built to create appropriate conditions for agriculture activities locally. The Romans undertook the first large-scale river interventions. Generals Corbulo and Drusus connected the Rhine River with the Meuse and IJssel Rivers (Huisman et al. 1998). After 2000 years BP, both discharge and sediment load in the Rhine delta have increased as a result of human influence (Berendsen & Stouthamer 2000). From the Roman period onwards, many other river management measures in the Rhine delta have followed, resulting in a riverine landscape which is now completely different from the time when the Romans entered the Rhine basin (Table 6.2) (Huisman et al. 1998; Havinga & Smits 2000; Middelkoop et al. 2005; Ten Brinke 2005). In the Rhine delta, the gradual construction of high water-free dwelling zones and dikes along the various river branches resulted in a closed dike system by 1450 AD (Ten Brinke 2005). This restricted fluvial dynamics to narrow parts of the alluvial system between the dikes, leaving a 0.5–1.0 km wide zone of active floodplain along the river where erosion and sedimentation processes continued (Middelkoop et al. 2005). The decreased dynamics in the floodplain and but increased dynamics within the river channel had a devastating effect on biodiversity in river-floodplain ecosystems. During the 17–19th centuries, meanders were artificially cut-off, side channels were closed and the discharge

distribution over the various Rhine branches was adapted (Middelkoop et al. 2005; Ten Brinke 2005). Physical normalisation of the Rhine branches in The Netherlands in the 18–20th centuries, mainly aimed at increasing safety against flooding and opportunities for shipping, further diminished fluvial dynamics (Havinga & Smits 2000; Ten Brinke 2005). River bank reinforcements, groynes and longitudinal dikes along the riverbed were built to prevent erosion of the banks and to catch sediment to create farmland in the floodplain. These measures were intended to increase flow velocities in the main channel, thus preventing the formation of sandbanks. In winter, these shallows were prone to develop ice dams, which formed a serious threat to the dikes as the flowing water pushed them up. Later it was found that these measures also benefited navigation because they had deepened the main channel. In order to optimise navigation, several weirs (sluice-dams) were constructed and so-called ‘width normalisations’ were carried out since 1870. Width normalisation means that the low water bed is limited to one main channel with a constant (normal) width. Groynes were constructed at regular intervals, which confined the low water bed into a narrower channel and kept the water flow away from the erodible bank. In the 19th and 20th centuries, after many uncoordinated regulations, two large-scale width normalisations were carried out in the main Dutch Rhine branches. Moreover, discharge distribution over the various channels is today strictly controlled. Apart from agricultural land use, sand and gravel extractions in the 20th century also had massive impacts on the structural diversity of river floodplain ecosystems. Middelkoop & Van Haselen (1999) and Ten Brinke (2005) give detailed descriptions of the present situation of the Rhine delta. At the Dutch–German border, the so-called Bovenrijn is a single river channel. About 10 km downstream, the river

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PART | I Rivers of Europe

PHOTO 6.11 Delta Rhine. Meander of the river Waal west of Zaltbommel in the Netherlands (Rkm 933.5–938). The secondary channel (foreground) constructed in the forelands mitigates the effects of river engineering. (Photo B. Boekhoven, Rijkswaterstaat, The Netherlands).

changes to a system of Rhine branches. At the Pannerdensche Kop, the river bifurcates into the River Waal and Pannerdensche Kanaal (Photo 6.10). Around 10 km further downstream, the Pannerdensche Kanaal bifurcates into the Rivers Nederrijn and IJssel. Further downstream, the name of the Nederrijn changes to Lek, and the Lek and Waal merge through a number of water courses around the city of Rotterdam. This area is known as the northern part of the Rhine– Meuse estuary. In the south, this estuary is connected with the River Scheldt estuary. The IJssel flows into Lake Ketelmeer, which is in turn connected to Lake IJsselmeer. The weir at Driel divides the river water between the Nederrijn and IJssel and ensures that a sufficient proportion flows into the IJssel during low flow periods. The Waal is the largest of all Rhine branches and is a broad free-flowing river (Photo 6.11). The river’s main channels are bounded by dikes (relatively low embankments), protecting agricultural

areas in the floodplain from summer flooding. Primary river dikes prevent the floodplain from flooding during high flows. In total, the surface area of the Rhine channels in The Netherlands is 36 700 ha, including some 28 000 ha of floodplains. In addition, the northern Rhine–Meuse estuary covers some 60 000 ha of river and floodplains. Land use of the embanked floodplains along the Rhine branches varies remarkably (Table 6.3). The history of the Rhine–Meuse–Scheldt estuary in southwest Netherlands is marked by a continuous struggle between man and the sea. Since the year 1000, humans reclaimed salt-marsh areas and transformed them into agricultural land (Smits et al. 2006). But periodic storm-floods destroyed the seawalls and recaptured parts of the reclaimed land. Between 1900 and 1950, an area of 10 000 km2 had a large number of islands and peninsulas, deep and shallow tidal channels, extensive intertidal sand- and mudflats

TABLE 6.3 Land use (%) of embanked floodplains of Dutch Rhine branches (Middelkoop & Van Haselen 1999) Bovenrijn–Waal

Pannerdensch Canal–Nederrijn–Lek

IJssel

Floodplain forest (nature) Brush/marsh Grassland Water Production forest Arable land Grass production Buit-up area Other land use

4 5 1 19 0 4 61 5 1

1 2 5 11 1 4 69 5 1

1 1 3 11 1 8 72 3 1

Nature Non-nature

29 71

20 80

16 84

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Chapter | 6 The Rhine River Basin

PHOTO 6.12 Delta Rhine. Outflow of the Nieuwe Waterweg in the North Sea (top) with the heavily industrialized Maasvlakte and in the south (foreground) the large disposal site ‘Slufter’ for controlled storage of polluted river sediments. (Photo B. Boekhoven, Rijkswaterstaat, The Netherlands).

reaching up to 20 km from the coast, vegetated coastal plains, and salt and brackish marshes above mean high water. The most landward parts of the estuaries, where the Rivers Rhine, Meuse and Scheldt enter the delta, were characterized by freshwater tidal marshes and willow coppice. The need for continuous coastal construction has intensified over the years as a result of population growth, land subsidence and rising sea level. The potential threat of storm surges from the North Sea led to the closure of Brielse Meer in 1950. After a large storm flood in 1953, the so-called Delta project was conceived as an answer to the continuous risk of flooding. The core of this project was to maintain a safe coastline, and called for the closure of main tidal estuaries and inlets in the SW Netherlands, except for Westerschelde and Nieuwe Waterweg. The former (semi-)estuaries Veersche Gat and Grevelingen were isolated from the North Sea by high sea-walls in 1961 and 1971, respectively, and converted into non-tidal lakes or lagoons filled with brackish or saline water. The Haringvliet was closed in 1970 by the construction of large sluices, meant to function as an outlet for the Rhine and Meuse. Construction of primary sea-walls in the mouths of estuaries included the need to reduce tidalcurrent velocities in the estuaries by constructing secondary compartmental barriers (Zankreekdam, Grevelingendam and Volkerakdam). In 1986, after much debate about the ecological impacts of dams in the Rhine–Meuse estuary, a storm-surge barrier across the mouth of the Oosterschelde estuary was installed as a compromise (Nienhuis & Smaal 1994). On one hand, this barrier allows low tides to enter the estuary freely, thus safeguarding the ecology of the tidal ecosystem. On the other

hand, the barrier guarantees safety for the human population and their properties when large storm floods threaten the area. Along the Westerschelde, the existing dikes have been raised to maintain international shipping access to Antwerp. In the Nieuwe Waterweg (Photo 6.12), the shipping route to the mainport of Rotterdam, the Maesland kering, a moving barrier protecting Rotterdam from storm surges, was finished in 1997. This enterprise was considered to be the final phase of the Delta project.

6.5.2. Hydrology and Temperature From headwaters to the sea, monthly discharge patterns of the Rhine exhibit a remarkable shift that reflects changes in the contribution of runoff from hydrologically different areas. The hydrology of the Rhine shows the influence of the Alps and the low mountain ranges, hills and plains of the remaining catchment. Alpine Rhine and Aare provide on average 34% of the annual discharge at the Dutch–German border; during summer this percentage exceeds 50% (Viviroli & Weingartner 2004). The annual flow pulse from the Alps, primarily fed by the melting of snow and ice, arrives downstream when the water balance of low elevation catchments is negative. Therefore, the Lower Rhine and Delta Rhine exhibit moderate seasonal variation in the long-term mean monthly discharge (Figure 6.4). With distance from the Alps, monthly hydrographs exhibit increasingly stochastic variation that reflects the influence of the Oceanic climate and a less predictable rain-dominated precipitation (Figure 6.5). Specific discharge declines from 40 L/s/km2 in the Alpine catchments of the Rhine and Aare, to 17 L/s/km2 in

218

FIGURE 6.4 The average monthly discharge (1931–2003) of the Rhine between Diepoldsau (Alpine Rhine) and Rees (20 km upstream of the Dutch–German border). The gauging station of Kaub is 45 km upstream of the Rhine–Moselle River confluence.

the Upper Rhine catchment and 15 L/s/km2 in the Lower Rhine catchment. The discharge (Qmean) of Vorderrhein and Hinterrhein is 56 and 61 m3/s, respectively, at their confluence near Reichenau. From Reichenau to Lake Constance, Qmean increases from 117 to 242 m3/s. Flow regimes of the Alpine Rhine and its tributaries and headwaters range from glacial to nivopluival (Weingartner & Aschwanden 1986). The glacial influence is small because only 86 km2 (1.4%) of the catchment are glacierized. Only 450 km2 of the entire Rhine catchment are covered by glaciers, most of which are in the catchment of the Aare (80%). Snowmelt is the primary

FIGURE 6.5 Monthly discharge in the Alpine Rhine (Diepoldsau) and Lower Rhine (Rees).

Sources: Federal Office for the Environment, Berne, Switzerland, and Global Runoff Data Centre (GRDC), Koblenz, Germany.

PART | I Rivers of Europe

water source of the Alpine Rhine. Depending on altitude, snowmelt peaks between April and June. Major parts of the catchment are relatively high in altitude (55% > 2000 m asl). As a consequence, mean monthly discharge peaks in June at 460 m3/s and the minimum typically occurs in January at 128 m3/s. Rainfall induced flow peaks often are superimposed on the seasonal flow pulse, primarily between March and November. Observed minimum and maximum discharge was 49 m3/s (December 1985) and 2665 m3/s (July 1987). The hydrology of the Alpine Rhine and its tributaries has been seriously affected by the operation of hydroelectric power facilities such as storage and pumped storage power stations constructed from 1950 to 1980s. The water of the Rhine is already diverted for hydropower production <2 km downstream of Lake Toma. Water is abstracted at numerous sites, primarily in smaller tributaries but also in the main stems of the Vorderrhein and Hinterrhein. Most of this water is transiently stored in reservoirs and used on demand for power production. The results are substantial flow reductions between withdrawal and return sites, and hydropeaking downstream of return sites. Today, flow reductions of >60% affect 30% of the Hinterrhein and 70% of the Vorderrhein, and smaller tributaries fall temporarily dry downstream of withdrawal sites. The lower Vorderrhein and Hinterrhein and the entire Alpine Rhine are strongly affected by hydropeaking. About 13 km upstream of Lake Constance, daily flow variation still is 100 m3/s; this corresponds to stage variations in the range of 0.6 m during winter low flow. The combined maximum storage volume of reservoirs in the Alpine Rhine catchment is 773 106 m3, which approximates 10% of the average annual Alpine Rhine discharge. The operation of storage power plants has damped the annual flow pulse and augmented winter low flow (Figure 6.5). Between 1939 and 2003, the average monthly summer discharge decreased by 60 m3/s and the average monthly winter discharge increased by 50 m3/s. The only run-of-river power plant at Domat-Ems (3 km downstream of the confluence of the Vorderrhein and Hinterrhein) has no influence on the flow regime because the impounded reach is relatively short (3 km). The catchment draining into Lake Constance excluding the Alpine Rhine comprises an area of 4960 km2 and provides 140 m3/s to the annual discharge of the High Rhine. The lake loses on average 12 m3/s by evaporation (Baumgartner et al. 1983) and about 5.5 m3/s are withdrawn for drinking water. Annual discharge increases between the outlet of Lake Constance and the Aare–Rhine confluence from 368 to 442 m3/s, and reaches 1059 m3/s in Basel. Monthly flow of the upper High Rhine reach shows a similar annual pattern like the Alpine Rhine, but Lake Constance delays the annual maximum by 3 weeks (Naef 1989). Except for the Aare River, flow regimes of tributaries are flashy with maximum monthly flow in March/April and minimum in September/October. In the Thur River, unpredictable spates with peak flows >350 m3/s occur on average 3.7 times per year (Uehlinger 2006).

Chapter | 6 The Rhine River Basin

FIGURE 6.6 Average monthly discharge of the Rhine tributaries Aare, Neckar, Main, and Moselle (1964–2003).

The Aare is the paramount Alpine river of the entire Rhine basin with a flow regime similar to that of the Rhine (Figure 6.6). At the confluence, the annual discharge of the Aare exceeds (at 559 m3/s) that of the Rhine by 23%. Relatively large lakes with volumes ranging from 1.2 to 11.8 km3 moderate short-term flow variations of the Aare as well as its two major Alpine tributaries, Reuss River and Limmat River. The Alpine influence in the form of meltwater is still evident in the annual flow pulse along the entire High Rhine, but with distance from Lake Constance, particularly downstream of the Thur River confluence, the hydrograph has increasingly irregular flow peaks. Flow extremes were 104 m3/s (1909) and 1180 m3/s (1999) in the upper reach (outlet of Lake Constance), 120 m3/s (1910) and 2250 m3/s (1910) upstream of the Rhine–Aare confluence, and 357 m3/s (1921) and 5090 m3/s (1999) in Basel. From Basel to the end of the Upper Rhine reach, mean annual discharge increases from 1059 to 1588 m3/s with the two tributaries Neckar and Main contributing 149 and 225 m3/s. Smaller tributaries from the right bank are the Rivers Wiese (Qmean 11.4 m3/s), Kinzig (Qmean 23 m3/s) and Murg (Qmean 17 m3/s), and from the left bank the River Ill (Qmean 60 m3/s). The signature of the Alpine flow pulse in the hydrograph disappears at the end of the Upper Rhine, reflecting the growing influence of tributaries with pluvial–nival regimes (monthly flow maximum between February and April depending on altitude, and minimum monthly flow between August and October). Minimum and maximum flows recorded at Mainz were 460 m3/s (1947) and 7000 m3/s (1882), respectively. Along the Middle Rhine, annual discharge increases from 1588 to 2043 m3/s, primarily due to the contribution of the Moselle River (Qmean 328 m3/s). Two smaller tributaries provide 31 m3/s (Nahe) and 51 m3/s (Lahn). At the end of this reach, the monthly flow is maximal in February and minimal in October; a seasonal pattern prevailing to the Delta Rhine (Figure 6.4). Major tributaries of the Lower Rhine are the Ruhr (Qmean 70 m3/s) and Lippe River (Qmean 67 m3/s). Upstream of the channel splitting of the Delta Rhine, annual discharge averaged 2297 m3/s, and maximum and minimum discharges recorded were 12 600 and 574 m3/s. During the dry and hot summer of 2003, discharge was <800 m3/s. The average annual ratio of maximum to minimum discharge is about 15

219

(Ten Brinke 2005). Of the three Delta Rhine branches, the Waal, Neederijn–Lek, and IJssel receive on average 65, 23 and 12%, respectively, of the discharge of the Bovenrijn (Rhine main stem). Most global circulation models suggest higher winter and lower summer rainfall for the Rhine basin. Hydrological simulations predict a progressive shift of the Rhine from a rain-fed/meltwater-fed river into a mainly rain-fed river (Pfister et al. 2004). From the Middle Rhine to the sea, the difference between present-day high average discharge in winter and the low average discharge in autumn should increase in all scenarios. This trend is assumed to be largest in the Alpine part of the basin. According to Lenderink et al. (2007), mean annual discharge is expected to decline in summer by 40% and increase in winter by 30%. Flows with a return period of 100 years (today) are assumed to increase between 10% and 30%. Temperature regimes along the Rhine main stem are characterized by minimum temperatures in January and maximum temperatures in July and early August. Annual mean water temperatures range from <1 C at the terminus of Paradise Glacier (Hinterrhein) to almost 15 C in the northern part of the Upper Rhine. The respective seasonal amplitude ranges from a few degrees to about 20 C. In the Vorderhein at Illanz (693 m asl), monthly water temperatures vary between 1.8 (January) and 10.9 C (July), and daily mean temperatures between 0.2 and 13.8 C. At Diepoldsau (410 m asl) near the lower end of the Alpine Rhine, corresponding monthly means are 3.3 and 13.5 C and daily means are 1.1 and 17.6 C. Power plant operations in the Alpine reaches affect the diel temperature regimes; for example, up to 2 C during winter low flow at Illanz. Lake Constance causes a major thermal discontinuity within the main stem of the Rhine. Between the mouth of the Alpine Rhine and the upper High Rhine, mean annual temperature increases by 4 C. From the outflow of Lake Constance to Basel, temperatures slightly increase: mean annual temperatures from 12.0 to 12.7 C, minimum monthly means from 3.7 to 4.9 C, and maximum monthly means from 20.9 to 21.3 C. At Reckingen (Rkm 90.5), maximum daily temperatures varied from 23 (2002) to 26.1 C (2003). Daily temperatures of the Aare River at the confluence are almost identical with those of the Rhine. From Basel to Mainz, annual temperatures of the Upper Rhine increase from 12.7 to 14.8 C. At Mainz, water temperatures average 6.3 C in January and 24.1 C in July, and maximum daily temperatures recorded from 2002 to 2006 ranged from 24.5 to 28.7 C. High temperatures of the Upper Rhine reflect the warm climate of the Rhine Graben rift valley and thermal pollution from the discharge of cooling water from numerous power plants and industrial facilities. From Mainz to the end of the Lower Rhine, annual mean water temperatures decline by 0.7 C and the average temperatures in January and July by 1 and 1.5 C, respectively. From 1971 to 2003, annual temperatures increased by 0.5 C in the Alpine Rhine (Diepoldsau) and by 1.0 C along

220

FIGURE 6.7 Mean annual temperature at three stations along the Rhine. Sources: Data from the Dutch Ministry for Traffic and Public Works (Lobith) and the Swiss Federal Office for the Environment (Diepoldsau, Rheinfelden).

the High Rhine (Figure 6.7). Much of this warming abruptly occurred in 1987–1988 (Hari et al. 2006). Upstream of the Rhine–Aare confluence, the effect of thermal pollution can be neglected. The Aare is the recipient of cooling water of three nuclear power plants of which two are 7.5 km upstream of the confluence with the Rhine. Thermal dumps are maximal in the north Upper Rhine where cooling water discharges equal 14 700 MW (45% of permitted cooling water discharges of the entire Rhine catchment). At Lobith (Lower Rhine), annual mean water temperatures increased between 1908 and 1986 from 10.8 to 12.6 C, primarily reflecting the growing thermal pollution. The increase of 1.4 C between 1988 and 2004 may be attributed mostly to global warming (Figure 6.7).

6.5.3. Biogeochemistry Water chemistry along the Rhine reflects the changing influence of watershed characteristics, runoff patters, atmospheric inputs and anthropogenic sources such as agricultural runoff and effluent discharges from urban and industrial areas. The Rhine is a hardwater river (Golterman & Meyer 1985). Rhine water is neutral to slightly alkaline and the buffering capacity is high. Areas where siliceous crystalline rocks (granite, gneiss) prevail include minor parts of the Rhine drainage such as the headwaters in the Aare and Gotthard massif or Vosges and Black Forest, and parts of the Odenwald along the Upper Rhine. Calcareous mesozoic sediments dominate the northern front range of the Alps, and the Jura Mountains and south German Scarplands. Paleozoic and prepaleozoic sediments occur in the Rhenish massif. Large areas are covered by quaternary sediments such as the northern forelands of the Alps, Rhinegraben rift valley, lower Rhine Embayment and Rhine delta. Chemical composition of the Rhine reflects to some extent this geochemical background. Conductivity and concentrations of major cations (except from Mg2+) and anions distinctly increase between the Alps and Rhine delta (Table 6.4). Mean annual pH (1995–2004) varies between 7.9 and 8.3, and decreases from the Alps to the delta by about 0.3. Seasonal pH amplitudes range from 0.7 to 0.9.

PART | I Rivers of Europe

The meso-oligotrophic Lake Constance has a relatively minor influence on average concentrations of most biogeochemical parameters, but affects seasonal patterns in the upper High Rhine. The input of industrial and domestic sewage beginning in the 19th century increasingly impaired water quality, particularly in navigable Rhine sections (see Section 6.1). A number of parameters showed that pollution levels peaked between 1970 and 1975 (Figure 6.8). In the Lower Rhine, annual concentrations of dissolved oxygen decreased to 4 mg/L, and ammonia concentrations reached 2.7 mg/L. Since then, the water quality has significantly improved because of joint efforts of the riparian states that resulted in the upgrading and construction of new sewage treatment plants. Available water quality data for Alpine headwaters of the Rhine are scarce, but anthropogenic influences on water quality are local and small because of low population density; an assumption supported by diatom indices (IKGB 2004). Data from nine water quality monitoring stations show distinct gradients in nitrogen and phosphorus along the Rhine main stem (Table 6.4). In the Alpine Rhine, an average phosphate concentration of 0.003 mg P/L contrasts with total P concentrations of 0.108 mg P/L that are dominated by the particulate inorganic fraction originating from glacial and snowmelt fed tributaries. Most of the particulate P-load is retained in Lake Constance. Phosphate concentrations increase from 0.007 mg P/L in the outlet of Lake Constance to 0.077 mg P/L at Koblenz, and remain relatively constant along the entire Lower Rhine. Nitrate and total nitrogen concentrations showed similar longitudinal trends, but in contrast to phosphate, nitrate reached high values of 0.59 mg N/L and total nitrogen 0.68 mg N/L already in the Alpine Rhine. In the Alpine catchments, atmospheric nitrogen deposits range from 10 to 15 kg N/ha/year, which is about five times above baseline deposition in minimally impacted systems (Rihm 1996) and results in high NO3–N concentrations in otherwise little affected high Alpine headwaters (Robinson et al. 2001; Tockner et al. 2002). From Lake Constance to the Upper Rhine at Basel, average nitrate concentration increase from 0.76 to 1.46 mg N/L and finally to 3 mg N/L at the Dutch– German border. The annual input (1996/1997) of total phosphorus and nitrogen into streams and rivers of the Rhine catchment equalled 26 175 tons P and 419 854 tons N. About 70% of the nitrogen and 54% of the phosphorus originated from diffuse sources (IKSR 2005). Improved phosphate elimination and substitution of phosphate in detergents resulted in a significant decrease of phosphate and total phosphorus concentrations at all stations between Lake Constance and the Rhine Delta, primarily after 1975 (Figure 6.8), but concentrations remained relatively constant after 1995. Nitrate concentrations peaked around 1985 and have declined since, reflecting construction and improved performance of sewage treatment facilities. Ammonium concentrations are

Station

River section

D.f.s. km

Diepoldsau

AR

150

Stein am Rh.

HR

225

Reckingen

HR

293

Weil

HR/UR

373

Karlsruhe

UR

564

Mainz

UR

701

Koblenz

MR

794

Bad Honnef

LR/MR

841

Kleve Bimmen

LR

1067

Cond. (mS/cm)

NO3–N (mg/L)

PO4–P mg/L

TP (mg/L)

Cl (mg/L)

H2SiO4 mg/L

SO42 (mg/L)

Na+ (mg/L)

K+ (mg/L)

Ca2+ (mg/L)

Mg2+ (mg/L)

DOC (mg/L)

TSS (mg/L)

299 52 306 13 340 32 355 34 498 85 505 53 524

0.58 0.15 0.76 0.10 1.27 0.36 1.46 0.36 1.62 0.12 2.54 0.23 2.54

0.005 0.004 0.007 0.003 0.014 0.007 0.018 0.008 0.036 0.007 0.057 0.007 0.077

0.091 0.129 0.020*

5.5 0.6 3.3 0.5 4.4 1.2 4.7 1.3 6.2 0.3 n.d. 6.8

46.1 11.8 32.0 1.2 29.7 2.5 26.7 2.5 29.3 2.1 50.3 6.0 53.6

3.1 1.2 4.8 0.3 6.4 1.1 8.7 2.1 35.8 15.3 35.6 11.5 43.5

1.0 0.2 1.5 0.1 1.7 0.2 1.9 0.3 3.5 1.0 4.3 0.8 4.7

44.0 6.3 45.6 1.0 50.0 5.0 52.5 5.1 54.6 3.3 63.1 3.4 65.7

9.1 1.9 8.1 0.2 10.2 1.0 8.2 0.8 7.4 0.3 9.8 0.6 11.1

1.2 0.5 1.6 0.1 2.2 0.5 2.3 0.5 2.0 0.2 2.6 0.1 2.4

134.4 189.7 n.d.

0.040 0.023 0.047 0.020 0.061 0.012 0.092 0.010 0.179

3.0 1.4 5.9 0.4 7.8 1.6 10.3 2.5 52.9 23.4 53.6 17.1 n.d.

533 54 634 74

2.67 0.25 2.92 0.33

0.071 0.011 0.076 0.017

0.154 0.022 0.150 0.012

62.5 16.4 105.5 23.1

8.4 1.1 8.2 0.9

49.3 5.1 59.0 6.2

39.5 10.5 56.9 12.0

5.0 1.7 5.7 1.8

66.4 3.1 78.6 4.2

11.1 0.7 11.7 0.7

2.7 0.3 2.8 0.3

28.0 11.7 29.4 9.7

Chapter | 6 The Rhine River Basin

TABLE 6.4 Biogeochemical parameters at different stations along the main stem of the Rhine

16.1 23.5 13.5 16.4 16.3 8.2 21.4 7.9 23.3

Average (bold) and standard deviation (italics) (1995–2004). River sections: AR = Alpine Rhine, HR = High Rhine, UR = Upper Rhine, MR = Middle Rhine, LR = Lower Rhine. D.f.s. = distance from source. Data sources: International Commission for the Protection of the Rhine (ICPR), Deutsche Kommission zur Reinhaltung des Rheins (DKR) and NADUF (National Long-term Surveillance of Swiss Rivers). *

Average of 2004.

221

222

FIGURE 6.8 Annual average concentration of nitrate, orthophosphate, ammonia and dissolved oxygen at Kleve-Bimmen (river 865 km).

presently <0.3 mg NH4–N/L. The transition from saturation to limitation of phosphate has been reported to be 0.006– 0.015 mg P/L (Bothwell 1989; Newbold 1992), a threshold that is exceeded downsteam of the Rhine–Aare confluence. Concentrations of dissolved oxygen in the Rhine main stem are relatively high today. The 10%-percentile varies between 5.9 mg O2/L in Mainz to 9.2 mg O2/L in the outlet of Lake Constance (DKR 2001). Chloride concentrations increase from 3 mg/L in the Alpine Rhine to 106 mg/L at the Dutch–German border. Sources of chloride include domestic sewage, road salt (during winter), industrial effluents and mining. Exploitation of the Alsatian potash mines ended in 2003, but runoff from tailings still results in a major increase in chloride concentrations in the Upper Rhine. Chloride from potash mines in Lorraine enter the Rhine via the Moselle River. Drainage waters from active and abandoned coal mines substantially contribute to the high chloride concentrations in the Lower Rhine, including effluents of chemical plants (LUA NWR 2002). Concentrations of dissolved organic carbon (DOC), which today range from 1.2 mg C/L in the Alpine Rhine to 2.8 mg C/L at the Dutch–German border (Table 6.4), decreased from 1976 at 13–15 mg C/L in the Middle and Lower Rhine to 3–4 g C/L in 1985. In the Alpine Rhine, DOC showed no significant trend since 1977, and between Lake Constance and Karlsruhe, where concentrations were <3 mg C/L, the decrease was moderate. More than 10 000 organic compounds synthesized in relatively large amounts, many with toxic or mutagenic properties, enter the Rhine in low concentrations. Today, about 150 compounds are routinely analyzed. These organic micropollutants include anilines, chlorinated benzenes, herbicides and pesticides, phosphoric acid ester, and volatile and non-volatile organic compounds. Weak and moderate polar organic pollutants

PART | I Rivers of Europe

adsorb onto suspended solids and sediments that result in relatively high concentrations in sediments of impounded reaches (e.g., chlorinated–benzene up to 3 mg/kg). Bulk heavy metals are associated with suspended solids and fine sediments. Concentrations of dissolved heavy metals are often below detection limits (e.g., mercury and cadmium). Natural background concentrations in suspended solids are low, values for mercury, cadmium, copper and zinc are 0.2 mg Hg/kg, 0.3 mg Cd/kg, 20 mg Cu/kg and <200 mg Zn/kg. Actual concentrations usually exceed these background values about 2–4 times (DKR 2001). Concentrations of lead, cadmium, chromium, copper mercury and zinc, primarily originating from human activities, increase downstream (LUA NWR 2002). Sediments in rivers, canals and harbours in the Rhine– Meuse delta are moderately to heavily contaminated due to (trans)national and local water pollution. In the past nautic dredging sludge was deposited off shore. However, environmental laws and policy called for isolated and fully controlled storage of dredging sludge. Therfore, in 1986–1987 a large-scale storage facility for contaminated dredging sludge was constructed on the Maasvlakte, a part of the Port of Rotterdam located south of the Nieuwe Waterweg (Photo 6.12). The total surface area of the Slufter depot is 260 ha and the storage capacity is circa 150 million/m3. While 15 years ago about 50% of the dredging sludge was still so contaminated, it needed to be stored at the special Slufter depot, nowadays only 10% qualifies for storage. Due to continuous industrial, communal and agricultural discharges of pollutants and recurrent flooding, large amounts of particulate-bound toxic substances are deposited in floodplains along the Delta Rhine (Middelkoop 2002). A major problem that remains to be solved is the pollution that has been accumulated over the last century in river sediments and floodplain deposits. Floodplain soils keep the heritage and risks of earlier river pollution. Respectively, 65, 45 and 35% of soil samples from floodplains along the rivers Waal, Nederrijn and IJssel exceed environmental quality standards for one or more contaminants (mainly metals), resulting in high remediation costs and impediment of physical reconstruction and ecological rehabilitation projects (Leuven et al. 2005). Persistent organic substances and (heavy) metals are continuously redistributed and mixed or covered by cleaner sediments (Middelkoop 2002; Wijnhoven et al. 2006). Both natural processes (e.g., flooding) and human influences (e.g., excavation, agriculture, and construction of embankments) have been and are still resulting in large environmental heterogeneity. Soil concentrations can vary greatly, even over small distances. These potentially toxic substances can enter food chains via uptake in vegetation and soil-dwelling invertebrates. For instance, for Cd, Cu, Pb and Zn, significant relations were found between concentrations in soil and arthropods (Schipper et al. 2008). For several vulnerable vertebrate species foraging in floodplains, such as the common shrew (Sorex araneus), the badger (Meles meles) and the little owl (Athene noctua), this might lead to

Chapter | 6 The Rhine River Basin

toxicological risks resulting from exposure to contaminated food (e.g., Kooistra et al. 2001; Leuven & Poudevigne 2002).

6.6. AQUATIC AND RIPARIAN BIODIVERSITY 6.6.1. Habitat Structure and Riparian Zone The natural riparian vegetation of the Rhine has been largely modified, for example, along the Upper and Middle Rhine the prevailing tree today is poplar (Populus x canadensis). The fertile floodplain was reclaimed quite early, and many cities along the Rhine contributed to further floodplain deforestation. Traditionally, the left bank was kept free of vegetation for towing boats. In the Middle Ages, dense forests (so-called ‘Gehecke’) were planted to protect settlements in the north Middle Rhine. Rings of willow trees were planted upstream of settlements to protect the settlements from ice scouring during winter floods, and produce raw material for wattles. After water table lowering in the southern Upper Rhine valley, the former floodplain was colonized by species of terra firme plants (not adapted to inundation). The upper Rhine headwaters are steep with boulders or bedrock substrate, and patches of finer sediments. During early summer, snowmelt and spates exert hydraulic stress on benthic communities. During low water, water abstraction results in low residual flow (loss of habitats with high current velocity) and flow intermittency. Bank protection (walls or stone riprap) and uniform cross-sections also resulted in habitat loss. In the relatively few reaches not affected by river engineering, habitat diversity is relatively high, for example, the 18-km long gorge of the Vorderrhein and the braided floodplain of the Hinterrhein near the confluence. However, both reaches are strongly affected by hydropeaking. Upstream of the Ill confluence, alternating point bars with backwaters provide some habitat heterogeneity but more downstream these bars are missing. In addition to a poorly structured channel, the entire Alpine Rhine is subject to hydropeaking. Clear and macrophyte rich groundwaterfed side-canals provide a contrasting habitat but, apart from a few rehabilitated reaches, the morphology of these manmade streams is quite uniform. Riparian vegetation above treeline is characterized by alpine grassland vegetation. At lower elevations (1500 m asl), willow (Salix appendiculata) and green alder (Alnus viridis) occur, and on coarse substrate on banks grow macrophytes such as common butterbur (Petasites hybridus), Rumex alpinus, Epilobium angustifolium and Cirsium olearaceum (Roullier 2005). More downstream (1200 m asl), tree vegetation is dominated by grey alder (Alnus incana) and willow shrub (Salix daphnoides, Salix elaeagnos). On stable floodplain terraces fir (P. abies) and grey alder occur. In the Alpine Rhine, the riparian zone is characterized by boulder riprap, except for a short reach near

223

Mastrils, and relatively narrow strips of grassland. The scattered remnants of former floodplain forests are isolated from the river by high artificial embankments. Between the delta of the Alpine Rhine and the upper High Rhine, lentic habitat conditions prevail for 60 km, except for the short riverine passage (Seerhein) between upper and lower Lake Constance. The load of suspended solids is deposited near the deltaic river mouth and along the lacustrine subsurface flowpath of the Alpine Rhine. Erosional banks along the surf zone of Lake Constance provide appropriate conditions for some lotic invertebrates (Scheifhacken et al. 2007). The annually flooded littoral zone of the lake provides habitat for communities adapted to large stage variations (Wantzen & Rothaupt 2008). In the Seerhein (outlet of upper Lake Constance), conditions are favourable for filter-feeders, especially zebra mussel (Dreissena polymorpha) (Werner et al. 2005). In lower Lake Constance, extensive shallow areas are habitats for aquatic macrophytes. Large reed belts occur in lower Lake Constance. Unregulated reaches of the High Rhine are characterized by relatively high habitat diversity with respect to depth and current velocity. In the upper High Rhine, coarse gravel forms few point bars along the naturally confined channel. Lake plankton supports a typical lake outlet community. Local scour holes in the riverbed are important spawning and wintering habitats for grayling (Thymallus thymallus). In shallow runs, the gravel sediments are covered by D. polymorpha or macrophytes, both creating specific habitats for invertebrates. Counter currents below point bars, few snags (snags are usually removed) and pillars of bridges provide habitats for resting fish. Particularly downstream of the Rhine Fall, river banks in the relatively steep valley are narrow and floodplains are marginal. The riparian zone typically changes within a few meters from gravel banks or rock outcrops to upland forests. Today, rapids only occur in two short (<1.5 km long) reaches. Stone ripraps and concrete walls are not only typical along developed areas such as villages or towns but also are widely found outside of such areas. Downstream of Rhine Fall, substrate in fast-flowing stretches between the power plants is dominated by gravel, and bedrock occurs at few sites. Channel morphology is relatively uniform in impounded reaches and the lower High Rhine, which is open to navigation (Rkm 146.5–165). Deposition of fine sediments occurs in slow flowing areas upstream of power plants. Tree vegetation in a narrow zone subject to inundation primarily includes black alder (Alnus glutinosa) and various willows. The largest remnant floodplain (4.3 km2) is at the Thur–Rhine confluence, but bank stabilization stopped natural river dynamics. Stands of ash (Fraxinocenetum excelsioris) dominate the floodplain forest (Roullier 2005). Existing riparian forests along the High Rhine are managed, with beech and oak (Q. robur) prevailing. In the southern section of the Upper Rhine, habitat diversity is extremely low in the Grand Canal d’Alsace with its concrete walls (Rkm 170–226) and relatively high in the old

224

Rhine (Restrhein) that parallels the Grand Canal. Sediments in this near-natural river channel are subject to siltation or become locally anoxic at base flow (10–15 m3/s) (Becker 1994). The remaining floodplain channels have largely lost their hydro-geomorphic dynamics, but still persist because of episodic floods. Only 6% of the floodplain area between Basel and Iffezheim (Rkm 335), which existed in1800, escaped channelization and regulation (H€ ugin 1981). The few remnants of the original floodplain are today natural preserves such as Taubergiessen (near Rhinau at Rkm 256). Because of reduced fluvial dynamics, the diversity of newly formed habitats such as gravel bars or slumped banks are limited. Existing meanders, oxbow lakes and other functional floodplain features are static and subject to siltation. Nevertheless, the diversity of aquatic habitats is still impressive. A particular floodplain habitat is clear groundwater-fed streams (so-called Giessen) that exist because of regionally coarse and porous aquifers. Between Breisach and Strasbourg (Rkm 294), the old Rhine channel is paralleled by monotonous loop diversion canals from four power plants. Habitat conditions are similar to those described for the Restrhein and Grand Canal, but the old Rhine receives far more water. Below Strasbourg, where the river is one single channel, physical habitat is limited to the river channel and the few floodplain relicts are small, except for the cut-off meander K€ uhkopf (near Riedstadt at Rkm 468–474). Bed sediments consist of gravel (in the fast-flowing section between Karlsruhe and Mannheim) and coarse sand below Mannheim (Becker 1994). Rock outcrops are rare, for example, near Nackenheim (Rkm 488). In the sections where sand prevails, dynamic underwater dunes develop (Carling et al. 2000). Apart from sheet-pile walls along harbours, almost all banks are stabilized with riprap. The few islands occurring in the Upper Rhine are partly protected against erosion. Seven oblong islands between Eltville (Rkm 509) and Bingen (Rkm 528) are longitudinally connected by riprap dikes forming shallow waters between the islands. In this area, a 566 ha zone has been designated as a Ramsar Site (no. 88), serving as a resting and wintering area for waterfowl. The present floodplain forest is a mixture of remaining original vegetation, planted trees, and terra firme species invading rarely flooded areas. In remnants of the Alsacian floodplains, Carbiener (1974) identified the following phytosociological units on a floodplain of a regularly flooded island (Rhinau): (a) young (20 years) initial stages of pioneer vegetation (Salicetum eleagni, Salici albae–Populetum nigrae) on disturbed soils, (b) mature softwood floodplain forest (Salici–Populetum) of 50 years and older, (c) mixed softwood/hardwood floodplain forest with poplar, ash and elm trees (Fraxino–Populetum albae) developing from the pre-rectification period and (d) old hardwood forest (Querco–Ulmetum) as a climax stage of the floodplain forest with several gradient-specific subclasses. Recent studies have analyzed the successional status of the alluvial hardwood forests, and the influences of management and nutrient inputs on their vegetation structure.

PART | I Rivers of Europe

Under natural conditions, pioneer softwoods are generally replaced by hardwoods in <100 years, and the high diversity of the Upper Rhine alluvial forests is a result of regular flooding (Schnitzler 1994; Schnitzler et al. 2005). Floodplain forests seem to be more diverse than the surrounding terra firme forests, and the drying of former floodplain forests has led to a decrease in litter production, leaf N and P concentrations (Tremolieres et al. 1998). In the Middle Rhine between Bingen and Koblenz, high current velocities (6–7 km/h) keep fine sediments suspended. Poorly rounded bed sediments become visibly smaller in the upper Middle Rhine and bedrock outcrops occur at many sites. In coarser sediments, colonization of the hyporheic zone by epibenthic invertebrates may go as deep as 70 cm, for example, by larvae of the mayfly Ephoron virgo (Wantzen 1992). Dense beds of D. polymorpha and mud tubes of Chelicorophium curvispinum reduce bed porosity and the oxygen availability in interstices (Rajagopal et al. 1999). Hyporheic fauna in tributaries from the mid-Rhenanian Mountains and Rhine often mix, for example, stygal gammarids (genus Niphargus) frequently occurs in the hyporheic zone of the Rhine below tributary confluences (Wantzen 1992). Below thalweg crossings, central bars occur. Some of these bars recently became sparsely vegetated islands (‘Gr€unde’) because their banks have been protected (Photo 6.8). Alternating wet and dry conditions provide a special habitat for some biota (Wantzen 1992). Older islands are covered by dense woody vegetation typical of the lower end of the floodplain gradient. Groynes provide special habitats somewhat comparable to natural floodplains. Between groynes, large amounts of fine inorganic and organic particles can accumulate when protected by islands against the impact of waves from ship traffic. These accumulations provide habitats for mud-dwellers similar to slack water areas below islands. Woody vegetation in this section is generally restricted to islands. The gravel islands are irregularly flooded and have scarce vegetation from resprouting logs and branches of Populus and Salix. Salix is especially adapted to breakage of branches during hydraulic stress that drift downriver and serve as propagules for recolonization of pioneer habitats. Older islands with alluvial soils show a mixture of Populus x canadensis and native softwood forest species (P. nigra, Salix alba, S. viminalis, S. fragilis, Sambucus nigra, Corylus avellana, Rhamnus frangula, Viburnum lantana, Crataegus monogyna) that are often covered with lianas (Clematis vitalba). Some islands host vinyards or are used for horticulture because of high soil fertility. In the Lower Rhine below the widening of the Rhine valley near the cities of Brohl and Bonn (Rkm 620–656), gravel sediments locally disappear and sand dunes develop. Downstream of D€usseldorf, vertical erosion into the Tertiary and Devonian clay deposits regionally results in an impermeable river bottom. Outside of large cities, the river banks are almost completely stabilized by riprap. Lateral sand

Chapter | 6 The Rhine River Basin

bars occur occasionally. Flooding is restricted to the mostly managed zone between the dikes and river, which are generally used as meadows for cattle ranching. Several artificial lakes (sand pits) are directly or indirectly connected to the main channel and provide habitats that partially fulfill functions of former floodplain waterbodies. Groyn fields characterize the three Rhine branches in the Delta. Forelands occur between the summer and winter dikes. Waterbodies in the forelands have lost the lateral connectivity with the main channel, which is deeply incised. Shallow lotic habitats are widely lacking (Bij de Vaate et al. 2006). Groyns and training walls along the river provide habitats for lithophilous species (Raat 2001).

6.6.2. Benthic Algae Friedrich & M€ uller (1984) mentioned the lack of a comprehensive account of benthic algae along the Rhine. Early studies include that of Lauterborn (1910) on the Upper Rhine and in a section of the High Rhine (Rkm 20–74). The study of Jaag (1938), who carefully studied different habitats of the Rhine Falls, mentioned 338 algal species. In a more recent study, Zimmerli (1991) focused on benthic and suspended algae at 37 stations along the Rhine main stem from the Rhine source (Lake Toma) to Basel and in 19 tributaries. He identified 552 species of which 455 occurred in the Rhine. He found that local (reach) species richness increased from 40 in the Alpine headwaters to about 80 in Basel. The algal community was dominated by Bacillariophyceae (194 species), Chlorophyceae (72 species), Cyanobacteria (72 species), and Conjugatophyceae (46 species). An investigation of benthic diatoms in the High Rhine between Lake Constance and Basel by Swiss and German authorities recorded 226 taxa (BUWAL 1993). A periphyton census neglecting diatoms of the same High Rhine section in 1995 (LFU BW 1996) showed that crust-forming algae typical of lowland lake outlets such as Phormidium incrustatum and Homeothrix crustacea were abundant.

6.6.3. Macrophytes and Bryophytes Early studies on hydrophytes date back to Lauterborn (1910, 1916, 1917, 1921). The major part of the Rhine (Lake Constance to Cologne) was recently studied and the literature revised by Vanderpoorten & Klein (1999). They found five species clusters for both macrophytes and bryophytes, with the highest overlap of clusters in the southern Upper Rhine. Thermal and trophic conditions of floodplain waterbodies differ strongly between the southern Upper Rhine (stenothermic, oligotrophic groundwater-fed ‘Giessen’) and the northern Upper Rhine (eurythermic, eutrophic oxbow lakes), resulting in distinctly different macrophyte vegetation. In the main channel of the Rhine, growth of aquatic phanerogams is hindered by coarse and mobile substrates, whereas bank habitats exhibit a rich bryophyte diversity.

225

Macrophytes are mostly found in floodplain habitats and slow-flowing habitats of the main channel. River regulation has strongly influenced the hydrophytes. Rheophilic bryophytes that formerly only occurred in the upper, high-gradient section of the river were favoured by the occurrence of solid substrates, and several species are found today in the Lower Rhine. Characean algae that were formerly found as pioneer vegetation on mobile coarse sands in dynamic floodplain channels have been reduced, but now colonize the gravel-pit lakes, especially in the Upper Rhine. Phanerogamic macrophytes show a less distinct longitudinal pattern than bryophytes because of homogenous habitat structure resulting from river engineering. However, remnant floodplain habitats ranging from exclusively groundwater-fed (at low discharge) to Rhine-water fed (at high discharge) waterbodies result in a distinct lateral gradient in aquatic plant communities (Vanderpoorten & Klein 1999). In the Alpine Rhine and its headwaters, unstable sediments and turbidity impede the growth of macrophytes, but mosses such as Philonotis seriata and Hygrohypnum smithi are adapted to these conditions (Vanderpoorten & Klein 1999). Water plants show a luxurious growth in lower Lake Constance and upper High Rhine, where nutrient supply, light conditions (low turbidity) and moderate current velocities provide ideal environmental conditions. The diverse aquatic flora comprises Myriophyllum spicatum, Zannichelia palustris, Elodea canadensis, Ranunculus fluitans, Potamogeton perfoliatus and P. crispus. During the oligotrophication period of the lake (1978–1993), the diversity of the plant community increased (Schmieder & Lehmann 2004). Today, several macrophytes, for example, Potamogeton associations, are increasingly replaced by various Chara species, presumably because of ongoing oligotrophication. The macrophyte community is also influenced by aquatic herbivorous invertebrates (Gross et al. 2001) or seasonally by birds (Schmieder & Lehmann 2004). The High Rhine is habitat for many rheophilic plants, for example, bryophytes such as Cratoneuron filicinum and Fissidens crassipes, as well as macrophytes like Potamogeton friesii, Groenlandia densa, Berula erecta and Callitriche obtusangula (Vanderpoorten & Klein 1999). In the Upper Rhine, macrophyte colonization is largely limited to the Restrhein and remnant floodplain waterbodies. In the Taubergiessen area, undisturbed groundwater-fed ponds are characterized by a specific flora, for example, the red algae Batrachospermum sp. and Hildenbrandia rivularis, and in the lower sections, thick carpets of C. obtusangula. Robach et al. (1997) compared the macrophyte vegetation structure in several eutrophic channels of the former Alsacian floodplain that were either directly connected to the Rhine (conductivity 350–800 mS cm 1) and the Ill River, a more acidic and less ion-loaded tributary descending from the Vosges Mountains (conductivity 150–750 mS cm 1). The Rhineconnected habitats had higher species richness (43 versus 25 species), greater biomass, and a more complex structure (4–5 versus <3 strata) than the Ill-connected channels.

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According to Braun-Blanquet (1964), the prevailing macrophyte communites in the Rhine-connected habitats were Lemnetum gibbae, Ceratophylletum demersi, Potamogenetum perfoliati, Ranunculetum fluitantis and Callitrichetum obtusangulae. In the Middle Rhine, fast currents limit macrophyte growth. However, the reduction in nutrients and turbidity enhanced the growth of vascular aquatic macrophytes in all hydrologically suitable habitats (e.g., the area between groynes and in small stillwater interstices within riprap). In the last 5–10 years, meso-eutrophic species such as Butomus umbellatus, Ceratophyllum demersum and M. spicatum are increasingly spreading. In the Lower Rhine and Delta Rhine high salinity and turbidity influence the occurrence of several macrophytes. Mesocosm experiments by (Van den Brink & Van der Velde 1993) demonstrated a high sensitivity of Potamogeton lucens, P. perfoliatus and P. nodosus to increased salinity.

6.6.4. Plankton 6.6.4.1 Phytoplankton Early studies of the Rhine phytoplankton included investigations by Lauterborn (1905) and Kolkwitz (1912). Lakes fringing the Alps and standing waterbodies connected with the main stem such as oxbow lakes provided planktonic alge in low numbers. In the early 20th century, cell densities were generally low and it was debated whether autochtonous river plankton existed (Friedrich 1990). Most common plankton in the early 20th century were diatoms such as Cyclotella bodanica, Cyclotella spp., Asterionalla formosa, Fragilaria crotonenis, Diatoma elongatum, and different forms of Synedra acus, besides Chrysophycea such as Dinobryon sertularia and Spaerocystis schroederi and a few Cryptomonads. Seeler (1936) studied phytoplankton in 1933 between Strasbourg and Rotterdam. He found a coincidence of phytoplankton minima with the discharge of waste-water (phytoplankton cell numbers ranged from 240 to 6900 m/L). The occurrence of Cyanobacteria, Planktothrix rubescens, in Rhine samples reflect the increasing eutrophication of lakes in Alpine forelands (Czernin-Chudenitz 1958). In the 1970s, cell densities reached >10 106/L, and Tubbing et al. (1994) reported a maximum of >50 106/L, corresponding to 140 mg chlorophyll a, at the Dutch–German border. Recent observations of phytoplankton, mainly within the ‘Rhine Action Programme’, covered the entire stretch between Lake Constance and the sea (IKSR 2002c; Tubbing et al. 1994) or parts of it (Admiraal et al. 1994; De Ruyter van Steveninck et al. 1992; Ibelings et al. 1998). Annual concentrations of suspended chlorophyll a ranged in 2000 from 2.9 to 3.4 mg/L from the High Rhine to the beginning of the Lower Rhine, and reached 8.3 mg/L at the Dutch–German border (Rkm 863), and decreased to 3.8 mg/L in Massluis (Rkm 1019) (IKSR 2002c). Chlorophyll a concentrations

PART | I Rivers of Europe

peaked in April/early May, with maximum values of 43 mg/L at the Dutch–German border and 46 mg/L in Kampen (Ijssel, Rkm 995). The chlorophyll a record at Lobith (Rkm 863) showed a decline in average chlorophyll a concentrations from 26 5 mg/L (average 1977–1981) to 11 4 mg/L (average 2001–2005), which may be attributed to improved water quality. The decline in the Delta reach may be attributed to grazing and sedimentation loss by plankton and dense populations of sessile filter-feeders (Ibelings et al. 1998). Chlorophyll a concentrations typically peak in spring and usually to a minor extent in July/August (Tubbing et al. 1994). The study of De Ruyter van Steveninck et al. (1992) showed increasing bacterial numbers from the Upper Rhine to Maassluis (9 109 to about 13 109 cells/L) during the spring phytoplankton bloom in 1990. The census of 2000 (IKSR 2002c) showed that Cyanobacteria were maximum during winter and diatoms prevailed in spring and summer. More frequent during summer also were Chlorophyceae, Chrysophyceae, and Dynophyceae. The influence of Lake Constance is evident until the Upper Rhine (dominance of Planktothrix agardhii/rubescens). Further downstream the plankton composition is influenced by the export of alge from the major tributaries Neckar, Main and Moselle. Cryptomonads and diatoms were dominant in the High Rhine, where Cyanobacteria peaked in autumn. Frequent species in the southern Upper Rhine were Planktothrix agardhii/rubescens, Rhodomonas minuta, and tychoplanktonic taxa such as Diatoma vulgaris and Cocconeis sp. More downstream, the abundance of Planktothrix agardhii/rubescens declined and centric diatoms became more important. In the Middle Rhine, Planktothrix spp. dominated in winter and early spring and afterwards centric diatoms; cryptomonads and Rhodomonas minuta var. nannoplanctica became more important during summer. Near the Dutch–German border, the Cyclotella–Stephanodiscus–Cyclostephanos–Thalassiosira complex dominated; Planktothrix agardhii/rubescens reached high numbers in winter. The community in Maasluis was similar but Spermatozopsis sp., Rhodomonas spp., and unicellular chlorophytes reached high abundances in summer.

6.6.4.2 Zooplankton Investigations of zooplankton are less comprehensive and typically restricted to selected reaches or stations along the Rhine main stem. Low abundance and species richness characterized the zooplankton in 1933 (Seeler 1936). A study performed in 1986/87 on the Lower Rhine showed zooplankton maxima in spring (Friedrich 1990). Common species included the genera Brachionus, Keratella and Polyarthra. Rotifers reached maximum densities of 160 individuals/L, and crustaceans were scarce 1 individuals/L. Higher densities were reported by Tubbing et al. (1994). During spring, rotifers, mainly Brachionus calyciflorus, Kreatella

Chapter | 6 The Rhine River Basin

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cochlearis and K. quadrata, reached up to 100 individuals/L at Koblenz, >1000 individuals/L at the Dutch– German border and 500 individuals/L in Maassluis. Crustaceans (mainly nauplii) increased along the same stretch from 1 to 10 individuals/L, and up to 178 individuals/L in Maasluis. Cladocerans (Bosmina spp. and Daphnia spp.) were rare in the upper section (1–3 individuals/L), but increased downstream to 25 individuals/L. According to the IKSR census of 2000 (IKSR 2002c), the reported decrease in zooplankton density in this stretch since 1990 has continued, presumably due to the decline in phytoplankton biomass.

6.6.5. Benthic Invertebrates Macrozoobenthic communities of the Rhine originally exhibited a distinct longitudinal zonation that reflected recent ecological conditions and paleogeographic settings, particularly in the southern Upper Rhine once belonging to the Danube and Rh^ one drainage (Kinzelbach 1990). River engineering in the last two centuries and pollution are considered to be the main causes eliminating faunistic boundaries. Macrozoobenthic communities are increasingly affected by non-natives migrating into the Rhine catchment through the north German and eastern European system of waterways connecting the Dnieper and Bug with the Rhine, the French waterway system (Mediterranean species), and the Main–Danube–Canal (Bij de Vaate et al. 2002; BUWAL 2005; Leuven et al. 2009; Tittizer et al. 1994). The number of non-native species in the Delta Rhine increased exponentially during the last 200 years (Figure 6.9) (Leuven et al. 2009). An important gateway for non-natives is the port of Rotterdam, which is the terminus of Rhine navigation and Europe’s largest seaport (yearly discharge of 5 billion tons of ballast water harbouring many non-native species). Ongoing warming will affect a higher percentage of indigenous species than non-natives (Leuven et al. 2007). Compared to the Ponto-Caspian province, the benthic invertebrate richness of the fauna north of the Alps is reduced because the Alps form a barrier that impeded the accessibility of southern refuges during Pleistocene glaciations, which enhanced species extinction and impeded or delayed re-colonization from these refuges after the last glaciation.

FIGURE 6.10 Taxa richness of benthic macroinvertebrates between Basel (river 152 km) and the Dutch–German border (river 870 km) during the 20th century. Taxa levels adjusted to allow comparison between different periods. Modified from Tittizer et al. (1994) and IKSR (2002a).

Benthic invertebrates of the Rhine have been studied since the early 20th century (e.g., Lauterborn 1916, 1917, 1918) when the river was already affected by pollution and river engineering. During peak pollution in the 1970s, the number of taxa in the navigable Rhine sections was minimal but subsequently increased parallel to the increase in water quality (Figure 6.10). The Sandoz-disaster of 1986 gave rise to detailed assessments of the recovery of the biota. Results from this monitoring program indicated that the Rhine has basically re-gained the number of taxa reported by Lauterborn (LFU BW 2004; Marten 2001) but the community, once characterized by insects, is now dominated by crustaceans and molluscs. This shift in community structure reflects the loss of natural habitat diversity, the widespread occurrence of artificial substrates such as stone riprap or concrete walls, and the invasion of non-natives. Non-natives now contribute 18% to the taxa inventory and dominate in abundance and biomass by >90% (IKSR 2002a; Nehring 2003). The invasion of Ponto-Caspian species dramatically increased with the opening of the Main–Danube–Canal in 1992. The polychaete Hypania invalida arrived in the Rhine already in 1996 (IKSR 2002a). Amphipods such as Dikerogammarus villosus, D. haemobaphes and Echinogammarus berilloni successfully immigrated through the Main– Danube–Canal. D. villosus colonized the Rhine between Lake Constance and the sea within 10 years, thereby strongly reducing the abundances of most other benthic species (Haas et al. 2002; Van Riel et al. 2006). Chelicorophium curvispinum, another Ponto-Caspian amphipod, reached the Lower Rhine through the North German waterway system in the 1980s and spread out at an amazing speed along the Rhine and its major tributaries Moselle, Main, and Neckar before the ‘Danube’ population arrived through the Main–Danube Canal. It out-competes the native fauna by building extensive networks of mud-tubes on firm substrate, including mussel shells, leading to the decay of Dreissena populations. Since 2001, numbers of C. curvispinum have declined due increasing predation and parasite impacts (Van Riel et al. 2006).

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Asian clams Corbicula fluminea and C. fluminalis colonized the Rhine from the sea. Both species presumably arrived from North America with ballast water of ships (Rajagopal et al. 2000). The clams reach high densities (60 000–100 000 individuals/m2), but occasionally die back during low water periods in summer (IKSR 2002a). Recently, the PontoCaspian Quagga mussel (Dreissena rostriformis bugensis) was recorded in the Rhine basin (Van der Velde & Platvoet 2007). This species has expanded it geographical distribution in Europe at a slower rate than the zebra mussel. The Chinese mitten crab (Eriocheir sinensis), a large grapsid, migrated from the sea to Lake Constance. This large benthic omnivore affects the invertebrate community at different levels and can damage dikes by its burrowing activities. The most recent census (IKSR 2002a) reported 479 taxa along the Rhine main stem between Lake Constance and the sea with dipterans contributing 105 taxa, trichopterans 79, ephemeropterans 49, oligochaets (37), gastropods 33, large crustaceans 23, and lamellibranchiats 22. Plecopterans included 11 taxa typically occurring in low abundances. Only 26% of today’s taxa have been found by Lauterborn and others. The number of taxa declines from the non-navigable upper High Rhine reach to the Rhine Delta (Figure 6.11), reflecting changes in water quality and habitat structure. About 20% of the benthic invertebrates in the examined Rhine sections are considered to be endangered (IKSR 2002a). Lauterborn (1916) described the benthic communities of the Vorderrhein and Hinterrhein before the impact of hydropower plants but when most river engineering works had been completed. Information on today’s benthic invertebrates is widely lacking. Environmental conditions in the Alpine Rhine are impaired by hydropeaking, which encompasses fast and major stage variations, high turbidity, and bedload transport during the daily peak flow. Invertebrate sampling performed in autumn and late winter showed low abundances and biomass (Moritz & Pfister 2001). The

FIGURE 6.11 Taxa richness of macroinvertebrates along the Rhine between the lower Lake Constance and the sea. The same taxonomic level has been applied for all Rhine sections. HR1 = High Rhine between Lake Constance and Aare confluence. HR2 = High Rhine between Aare confluence and beginning of the navigable reach. HR3 = High Rhine navigable reach. UR1 = southern Upper Rhine: Grand Canal. UR2 = southern Upper Rhine: Restrhein. UR3 = northern Upper Rhine. MR = Middle Rhine. LR = Lower Rhine. DR = Delta Rhine. Modified from BUWAL (2002).

PART | I Rivers of Europe

number of taxa increases along the studied 55-km long reach from 35 to 50. The invertebrate community is dominated by chironomids, mainly Orthocladinae, Diamesa sp. and Eukiefferella sp. Most frequent species or taxa are Baetis alpinus and B. rhodani among the mayflies, Leuctra sp., Capnia sp. and Rhabdiopterix sp.among the stoneflies, and Allogamus sp. and Rhyacophila sp. among the caddisflies. Dominant among the blackflies were Simulium sp. Hydropeaking enhances the clogging of bed sediments, which negatively affects interstitial fauna. Small interstitial animals such as the chironomids Helenialla sp. or Parakiefferella sp. cannot use sand-clogged interstices. Allogamus auricollis flushed away during peak flows accumulates in low-current areas, where they reach high densities. The combined effects of hydropeaking and channel rectification shift the structure of the benthic community towards that of a torrential mountain river (Moritz & Pfister 2001). The benthic fauna of Lake Constance is well documented; historical records include studies by Lauterborn (1921) and Muckle (1942). The native fauna is highly habitat-specific and includes oligochaete and chironomid communities in deep sediments, wave-adapted species at erosional banks (Scheifhacken et al. 2007), and a segregation between the lower, the upper and uppermost section of the littoral zone that falls dry from autumn to spring (M€ortl 2004). Macrophyte-covered habitats of the lower Lake Constance harbour a specific fauna that includes several herbivorous species (e.g., the pyralid moth Acentria ephemerella, Gross & Kornijow 2002). Only recently, the invertebrate fauna of the limnetic-depositional and erosional habitats of the lake has been changed by non-natives. The most abundant gammarid species, Gammarus roeseli (probably an invader that replaced the native G. lacustris in large parts of the lake during the eutropication phase in the 1960–1970s) is currently being severely threatened by the invasive D. villosus (Hesselschwerdt et al., in press). The decapod fauna, once including large specimens of the crayfish Astacus astacus, has been replaced almost completely by non-native Astacus leptodactylus and Orconectes limosus. When writing this chapter, the Ponto-Caspian freshwater shrimp Limnomysis benedeni arrived in Lake Constance, where it started to form large swarms (Fritz et al. 2006). The invasion by D. polymorpha in 1965 had a major ecological impact (Siessegger 1969). Mass populations caused the clogging of water intakes of drinking water facilities and changed the sediment structure by masses of shells and byssus threads. The large native mussels Anodonta anatina and A. cygnea suffered from competition and physical stress because Dreissena colonized their shells (Bauer 2002). Dreissena also lead to an increase of waterfowl wintering on Lake Constance (Werner et al. 2005). In the Seerhein, which connects the upper and lower Lake Constance, >90% of the standing crop (9.9 kg fresh weight/m2 corresponding to 60 000 animals/m2) was consumed by wintering waterfowl, mainly tufted ducks (Aythya fuligula) and pochards (Aythya farina) (Cleven & Frenzel 1993). Currently, the Asian clam

Chapter | 6 The Rhine River Basin

C. fluminea is spreading in shallow zones of the lake. Because of its hard shell, it may probably be less integrated in the food web than Dreissena and change the structure of soft substrate habitats. The benthic community of the upper 26-km long High Rhine is typical for lake outlets with high densities of filterfeeders (D. polymorpha, Hydropsychidae, Simuliidae) (Caspers 1980). Low turbidity (plankton concentrations in the meso-oligotrophic Lake Constance are relatively small) and moderate nutrient contents favours benthic algal growth on stable gravel substrate, supporting benthic grazers such as the neretid snail Theodoxus fluviatilis. Rhithral taxa include Dugesia gonocephala, Gammarus fossarum, the mayflies Potamanthus luteus, Habroleptoides confusa, Rhithrogena semicolorata, Ecdyonurus sp., Baetis spp., stoneflies Perlodes sp., Leuctra sp., Nemoura sp., Amphinemura sp. and caddisflies Sericostoma, Glossosoma and Silo (IKSR 2002a). Tubificids and other pelophilic species reach high densities in impounded reaches upstream of power plants, where muddy sediments prevail. In free-flowing reaches between power plants, the composition of benthic invertebrates is similar to that in the lake outlet but with fewer filterfeeders. D. polymorpha occurs in the entire High Rhine. Densities decline with distance from Lake Constance. The navigable High Rhine stretch is characterized by high densities of non-natives (up to 95%) such as Chelicorophium curvispinum, D. villosus, H. invalida, Corbicula sp. and Jaera istri. In the southern Upper Rhine (Rkm 172–355), taxa richness is distinctly lower in the uniform Grand Canal d’Alsace and loop diversion channels of the run-of-river power plants than in the stretches with residual flow such as Restrhein and the old Rhine bed that parallel the four loop diversions (Figure 6.11). On the concrete walls of the Grand Canal, only a few species are abundant, e.g., Psychomya pusilla, that can cope with the green algae covering the concrete surface. The walls are nearly void of invertebrates during winter (IKSR 2002a). The occurrence of the mayfly P. luteus or caddisfly Cheumatopsyche lepida reflects the influence of the High Rhine fauna on community composition in residual stretches. In the nearly stagnant waters of residual stretches, limnetic species such as Lymnaea stagnalis and Caenis horaria can be found. In the northern Upper Rhine (Rkm 355–530), the number of taxa excluding Oligochaeta and Chiromomidae is 95 (IKSR 2002a). The crustaceans D. villosus, Echinogammarus ischnus and Corophium curvispinum reach high densities, as well as D. polymorpha and the snail Bithynia tenticulata. In oxbow lakes connected to the main stem and sections where islands reduce the ship-induced wave action, native mussels such as Unio pictorum, U. tumidus, A. anatina, A. cygnea and the non-native shrimp Athyaephyra desmaresti colonize mud and sand substrates (IKSR 2002a). The occurrence of species such as Baetis muticus, Heptagenia flava, Ephemera vulgata, Limnius perrisi and Macronychus quadrituberculatus indicate the improved wa-

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ter quality since 1995 (LFU BW 2004). However, many species, especially stoneflies, mayflies and caddisflies, found by early investigators are still missing (Marten 2001). Like in the northern Upper Rhine, invertebrate communities of the Middle Rhine and northern Lower Rhine are dominated by species common and frequent in large rivers with low demands regarding habitat conditions (IKSR 2002a). In the Middle Rhine, areas protected from waves provide habitat for epipotamal species like C. lepida and P. luteus but also for the Ponto-Caspian freshwater shrimps L. benedeni and Hemimysis anomala. Mayflies and caddisflies of the Lower Rhine include species characteristic of potamal reaches of large rivers such as Heptagenia sulfurea, E. virgo, Hydropsyche contubernalis, H. bulgaromanorum and P. pusilla. The dominant species with respect to biomass and abundance are non-natives such as J. istri, D. villosus and Corophium curvispinum. The large mussels Pseudoanodonta complanata and Unio crassus were found in small numbers within groyne fields. More frequent are U. pictorum, A. cygnea and the non-native C. fluminea. Sessile filter-feeders, mostly bryozoans (Fredericiella sultana, Paludicella articulata, Plumatella emarginata, Plumatella repens) and freshwater sponges (Spongilla), are important for the self-cleansing potential of the river (IKSR 2002a). Native species, which disappeared during the peak pollution period, re-colonized the river but only a few species have reached pre-pollution biomasses, for example, E. virgo (Marten 2001; IKSR 2002a). Larvae of this polymitarcid mayfly live in U-shaped burrows and in hyporheic sediments (Wantzen 1992; Kureck & Fontes 1996). In July 1991, a spectacular mass emergence of E. virgo caused car accidents and traffic jams on Rhine bridges illuminated by streetlamps. Recently re-found native species also include larvae of the gomphid dragonflies Gomphus vulgatissimus and G. flavipes in groyne fields. The change from gravel to sand coincides with the occurrence of species able to cope with the moving sand dunes such as the chironomids Kloosia pusilla and Robackia demeijeri, and the oligochaete Propappus volki (IKSR 2002a; Sch€oll & Haybach 2004). Invertebrates of the Delta Rhine, where sandy substrate prevails, is characterized by a diverse chironomid and Oligochaete fauna (IKSR 2002a). Like in the Lower Rhine, K. pusilla und R. demeijeri reach high densities in habitats with fast flow. Oligochaets (Enchytraeidae, P. volki) are dwellers of the navigation channel, where flow is high and sediments are moving. Tubificidae are frequent in low current areas. Sand also provides habitat for small mussels such as Pisidium henslowanum, Pisidium moitessierianum and Pisidium nitidum. Corophium curvispinum and the chironomid Dicrotendipes nervosus are frequent on solid substrates (groynes and bank riprap). The brackish water zone of the lower Delta Rhine hosts only a few euryhyaline species like Corophium multisetosum, C. volutator, the crab Rhithropanopeus harrisii and the shrimp Palaemon longirostris, both migrating upstream up to 150 km from the sea (IKSR 2002a).

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PART | I Rivers of Europe

6.6.6. Fish Ausonius, a latin poet of the 4th century, provided a culinary and aesthetic description of the fishes of the Moselle River and later Leonhard Baldner, a Strasbourg fisherman, wrote in 1666 AD the faunal study ‘Das Fisch-, Vogel- und Thierbuch’ that included much information on large and commercially interesting fish (Geus 1964; Lelek 1989). A first description of the distribution of fishes between Lake Toma and the sea was given in Lauterborn’s Rhine monograph (Lauterborn, 1916, 1917, 1918). The fish fauna of the Rhine have a heterogeneous longitudinal distribution, which is unusual compared to other European rivers and reflects the historical development of the Rhine drainage, including the Pleistocene glaciations (Kinzelbach 1990; Lelek & Buhse 1992). At the end of the ice ages, fishes north of the Alps almost became extinct. As a consequence, the diversity of today’s fauna is relatively low. Recolonization by fishes occurred from refuges located southwest and southeast of the Alps and Carpathians (Lelek & Buhse 1992). The indigenous fish fauna between Lake Constance and the Lower Rhine comprised about 44 species until 1880 (Lelek 1989). In the High, Upper and Middle Rhine, 19 species disappeared by 1950, and 3 species later. In the Lower Rhine, 42 species were lost by 1880, another 14 species by 1950, and 4 species later. Many of the remaining species also decreased in abundance. The decrease in diversity and abundance coincided with increasing pollution, habitat loss by river engineering, and construction of powerplants. The closure of Afsluitdijk (1935), which separated the Zuiderzee from the sea, and Haringvliet sluices (1970) limited migratory fishes from moving from the sea to freshwater spawning areas. The remaining open channel, the Nieuwe Waterweg, flows through a highly industrialized area with many harbours and intense ship traffic (Brenner et al. 2003). Populations of long-distance migrating fish such as Atlantic salmon (Salmo salar), allis shad (Alosa alosa), twait shad (Alosa fallax), Atlantic sturgeon (Acipenser sturio), sea trout (Salmo trutta trutta), sea lamprey (Petromyzon marinus) and eel (Anguilla anguilla) declined or became extinct (Lelek 1989; De Groot 2002). The Rhine was the European river with the largest salmon population. Salmon once migrated >1000 km to their spawning sites in the Aare and Upper Rhine tributaries before overfishing, chemical pollution, and migration barriers drove the population to extinction in the 1950s (Figure 6.12). The most recent census of IKSR indicate a substantial regeneration of fish communities: 43 of the original 44 indigenous species were present in the river, including an additional 20 non-native species (IKSR 2002b). Only the Atlantic sturgeon was not reported. The recurrence of Atlantic salmon in the Rhine reflects an improved water quality, restoration of spawning and nursery areas in tributaries and massive stocking (fingerlings of Irish, French, Scottish and Scandinavian populations) but today, the number of salmon is still small compared to their

FIGURE 6.12 Salmon catches in the Dutch part of the Rhine (1863– 1953). Modified from De Groot (2002).

abundance in 19th century. About 1000 individuals reached the Upper Rhine north of Strasbourg because of new fish passes at Iffezheim (Rkm 334) and Gambsheim (Rkm 309). Video records of the Iffezheim fish pass showed the passage of Atlantic salmon, sea lamprey, shad, sea trout and eel. Eight powerplants still obstruct the upstream migration to the Swiss border. The Rhine Minister Conference in 2007 adopted the masterplan ‘Migratory Fish’ that concerns an improvement of upstream migration of migratory fish by modifying the floodgates at Haringvliet and constructing a fish passage at Strasbourg by 2015 (IKSR 2007). Along the main stem of the Rhine, the number of species changes substantially (Figure 6.13). Investigations of the fish fauna in the Rhine headwaters are scarce. According to Lauterborn (1916), the fish of Vorderrhein and Hinterrhein included brown trout (Salmo trutta f. fario), migrating lake trout (Salmo trutta f. lacustris) that spawned in the Vorderrhein up to an elevation of 900 m asl, minnow (Phoxinus phoxinus) and bullhead (Cottus gobio). Today, the fish fauna of the Vorderrhein and Hinterrhein includes brown trout, lake trout, bullhead, grayling (T. thymallus), and sporadic brook trout (Salvelinus fontinalis) and rainbow trout (Oncorhynchus mykiss). Minnows form a small population in the lower Hinterrhein and stone loach (Barbatula barbatula) was recently found in the lower Vorderrhein.

FIGURE 6.13 Species richness of fish in the Rhine between the Alps and the sea. VHR = Vorderrhein and Hinterhein, AR = Alpine Rhine, LC = Lake Constance, HR = High Rhine, UR = Upper Rhine, MR = Middle Rhine, LR = Lower Rhine and DR = Delta Rhine.

Chapter | 6 The Rhine River Basin

Before regulation, the Alpine Rhine provided habitat for about 30 fish species (Schmutz & Eberstaller 1993). Channelization of the river resulted in a major loss of stagnophile species. Besides low habitat diversity, the impact of hydropeaking (high flow variation and turbidity, poor food resources) results in small populations (<50 individuals ha 1 and 10 kg ha 1). Today the fish population comprises 19 species, including introduced rainbow trout and zander. The non-native rainbow trout introduced in the late 19th century and stocked in Lake Constance and Binnenkan€alen successfully compete with brown trout and to a minor extent lake trout. Of the fishes still present in the Alpine Rhine, 12 species are considered threatened. Lake trout spawn in fast-flowing tributaries of Lake Constance, including the Alpine Rhine, Vorderrhein and Hinterrhein, Ill and Bregenzerach. Hydropeaking, migration barriers such as the powerplant of Domat/Ems (constructed 1959–62), and isolation of tributaries and side-canals, severely affected the lake trout population (Ruhle et al. 2005). In 2000, the powerplant had a vertical-slot fish pass installed. The side-canals provide habitat for 13 species most of which also occur in the Alpine Rhine. The more suitable habitat conditions (clear water and constant flow) in side-canals results in relatively high fish standing stocks. The highest species richness, 28 taxa including the non-native rainbow trout and zander (Sander lucioperca), was observed in the Alter Rhein (Old Rhine), reflecting the connectivity of this former main channel with Lake Constance (Schmutz & Eberstaller 1993). Lake Constance is inhabited by 33 fish species, about the same number as in the beginning of the 20th century (Fischer & Eckmann 1997; Eckmann & R€ osch 1998). Present species include introduced fishes such as pike perch (S. lucioperca), three-spined stickleback (Gasterosteus aculeatus), rainbow trout, sunfish (Lepomis gibbosus) and ruffe (Gymnocephalus cernuus). Ruffe, first recorded in 1987, became the dominant fish in shallow waters, feeding on benthic organisms but switching to whitefish eggs during the whitefish spawning period. Ruffe are a concern for fishery management since perch (Perca fluviatilis), which also feeds on benthic organisms, and whitefish are the most important catch by professional fishermen. Whitefish (Coregonus lavaretus, Coregonus macrophtalmus), lake trout, and charr (Salvelinus alpinus) are important pelagic species. In the littoral zone, chub (Leuciscus cephalus), dace (Leuciscus leuciscus), bream (Abramis brama) and percids (Gymnocephalus cernuus, P. fluviatilis) dominate during summer, whereas burbot (Lota lota) and stone loach (Barbatulus barbatulus) occur throughout the year (Fischer & Eckmann 1997). A declining fish catch, mainly perch and to a minor extent also whitefish, parallel the changing trophic state of the lake, a phenomenon observed in many lakes of the Alpine foreland under oligotrophication. The High Rhine provides habitat for about 36 species, including five introduced fishes. Construction of powerplants between Basel and the Rhine Falls imposed major obstacles for migrating fish. After completion of the power-

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plant Augst-Wyhlen (Rkm 155) in 1912, catches of Atlantic salmon decreased to zero upstream of the plant. Allis shad, a less potent swimmer, once migrating up to the rapids of Laufenburg (Rkm 121) became extinct, presumably due to increased current velocities in the Upper Rhine. In reaches impounded by powerplants, rheophilic species such as brown trout, grayling, rissle minnow (Alburnoides bipunctatus), varione (Leuciscus souffia agassizi) and nase (Chondrostoma nasus) disappeared and stagnophile species such as bream, pike (Esosx lucius) and roach (Rutilus rutilus) became abundant. The nase, once a highly abundant fish – during the spawning period, the plentiful catches were used as pork food or fertilizer – rarely occurs today (Gerster 1991). Clogging of gravel substrate with fine sediments in impounded sections decreases spawning habitats of lithophil fish such as brown trout and grayling (Zeh & D€ onni 1994). Relatively large grayling populations in the 10-km long freeflowing stretch downstream of lower Lake Constance and between the powerplant of Rheinau (Rkm 55) and the Thur River confluence (Rkm 65) are remnant populations once dominating the High Rhine. Channelization and powerplants are the most severe menaces to grayling populations. A new threat to fishes is global warming, for example, only 3% of the population between Lake Constance and the Rhine Falls survived the hot summer of 2003 (Walter 2006). The fish fauna of the Upper Rhine at 56 species is the most diverse of all Rhine sections. The 2000 census reports the highest species richness in the ‘Restrhein’ (southern Upper Rhine) side channels, at tributary confluences, and oxbow lakes with a surface connection to the river. Most common species are chub (L. cephalus), perch and eel. Pike and barbel (Barbus barbus) reach high abundances in stagnant and slow-flowing water. Common fishes in the northern Upper Rhine are roach, eel, perch, white bream (Blicca bjoerkna), asp (Aspius aspius), chub and bleak (Alburnus alburnus). The reach below the Main–Rhine confluence recently became inhabited by tubenose goby (Proterorhinus marmoratus), which immigrated through the Main–Danube canal. The fish fauna of the Middle Rhine includes about 40 species of which 25% are non-native. Although environmental conditions of the Middle Rhine are similar to those of the High Rhine, brown trout and grayling are lacking because of relatively high temperatures during summer. In the main stem, the fish community is dominated by roach. Masses of young roach and to a minor extent perch and asp have been observed in low current areas (IKSR 2002b). The number of fishes in the Lower Rhine is 37, of which four species are non-native. Common are roach, perch, bleak, chub, eel and bream (A. brama). The present fish fauna of the Delta Rhine is dominated by eurytopic cyprinids, whereas rheophilic species are decreasing (Raat 2001). The most abundant fishes in the Delta Rhine are roach and bream followed by eel, perch, pike perch, white bream (B. bjoerkna) and ruffe. Catches of anadromous species such river lamprey (Lampetra fluviatilis), sea lamprey, salmon,

232

shad, sea trout, common whitefish (C. lavaretus) and houting (Coregonus oxyrhynchus) have increased in the last few years (IKSR 2002b).

6.6.7. Amphibia and Reptiles Few amphibians use the main channel of the Rhine for spawning or foraging. Predation by fish and the high current make the main channel a hostile environment for amphibians. Only a few central European species are adapted to high current velocities. Larvae of the fire salamander (Salamandra salamandra) occur in rhithral sections of tributaries along the Upper and Middle Rhine. In Lake Constance, stagnant waters occur but predation is high from avian predators (herons, grebes, storks). Alpine newts (Triturus alpestris) are rarely observed in the lake. Green frogs (Rana esculenta complex), grass frogs (Rana temporaria) and toads (Bufo bufo) regularly oviposit in shallow, macrophyte-rich shores of Lake Constance, and along the High, Upper and Middle Rhine. Ringed snakes (Natrix natrix) occur in the same areas. Another waterbound snake, the dice snake (Natrix tesselata) is very rare and restricted to isolated areas on the Nahe and Lahn tributaries. The highest amphibian diversity is found in the floodplain areas and small waterbodies of the Upper and Middle Rhine. In recent gravel ponds, rare species such as Bombina variegata, Alytes obstetricans and Bufo calamita occur. Densely macrophyte-rich ponds harbour diverse newts (Triturus cristatus, Triturus helveticus in the southern Upper Rhine). The latter species is replaced by T. vulgaris in the northern Middle Rhine. In reed belts and willows of Lake Constance and floodplains of the Upper Rhine, tree frogs (Hyla arborea) can be heard during summer. Early studies reported populations of the European water turtle Emys orbicularis in floodplain ponds of the Rhine (Mertens 1947). Rare recent sightings of this species are due to the release of aquarium specimens. Several non-native reptiles (mostly the painted turtle Chrysemys picta and other turtles, but even caimans and alligators) are observed for the same reason; however they rarely find suitable wintering conditions to maintian populations. Loss of habitat due to river engineering and habitat fragmentation have led to a decline or local extinction of many amphibians and reptiles (Tittizer & Krebs 1996; Lippuner & Heusser 2005). Due to land-use changes and river regulation, many amphibian populations declined or gone extinct in floodplains along the Rhine tributaries in The Netherlands (Delta Rhine). However, several common amphibian species still occur, such as Triturus vulgaris, B. bufo, R. temporaria and R. esculenta complex. The frequencies of occurrence and densities are still rather low in comparison with pristine areas. B. calamita has higher frequencies of occurrence inside than outside floodplains. Species like H. arborea, Pelobates fuscus and T. cristatus

PART | I Rivers of Europe

are rare or even locally extinct (Bosman 1994; Creemers 1994; Dorenbosch et al. 1999). Suitability of waterbodies in floodplains is determined by water type (oxbow lake, pond, clay pits) and a combination of other factors (vegetation, water quality, and presence of fish) that are correlated with inundation frequency (Creemers 1994). Bosman et al. (1996) report on the selection of hibernation sites of toads in floodplains. B. bufo hibernate in meadows, thickets and bushes on sand or clay in the higher as well as lower parts of floodplains. B. calamita clearly prefer sandy habitats in the higher parts of floodplains. The ringed snake snake is still frequently observed in floodplains along the Nederrijn and IJssel (Creemers 1994).

6.6.8. Avifauna A short summary of the avifauna along the Rhine can be found in Tittizer & Krebs (1996). Results of the most recent waterbirds census have been recently published (Koffijberg et al. 2001). In Europe, the Rhine valley is one of the most important wintering areas for West-Palearctic waterbirds and many species use this area as a stop-over during autumn and spring migration. Lake Constance, IJsselmeer/Markermeer and the Randmeren2 are important resting places for a large number of waterbirds. The Rhine floodplains provide habitats for breeding, foraging and resting areas for migrating birds. Important in this respect are the four Ramsar wetlands of lower Lake Constance, the Restrhein (southern Upper Rhine), the reach between Eltville and Bingen (northern Upper Rhine), and the reach between Bislich and the beginning of the Delta Rhine. The loss of habitats from river engineering, elimination of floodplain forests and intense agricultural activities resulted in a loss of species, and favoured generalists and the immigration of new species. The loss of sand and gravel bars and islands, and bank stabilization by stone riprap and walls strongly affected plovers (Charadridae) and waders (Scolopacidae). Large predatory birds such as lesser spotted eagle (Aquila pomarina), osprey or fish eagle (Pandion haliaetus), short-toed eagle (Circaetus gallicus), hen harrier (Circus cyaneus), peregrine falcon (Falco peregrinus) disappeared around 1900 but osprey and peregrine falcon have been recently observed breeding in the Rhine valley. Populations of grey heron (Ardea cinerea), great crested grebe (Podiceps cristatus), mallard (Anas platyrhynchos), black kite (Milvus migrans), Montagu’s harrier (Circus pygargus), black woodpecker (Dryocopus martius), magpie (Pica pica), cormorant (Phalacrocorax carbo) and eurasian jay (Garrulus glan-

2. A chain of lakes created during the embankments in the 1950s and 60s separating the polders of Zuidelijk and Oostelijk Flevoland, and Noordoost polder from the provinces of Overijssel, Glederland, Utrecht and NoordHolland.

233

Chapter | 6 The Rhine River Basin

darius) are increasing; greylag goose (Anser anser), gadwall (Anas strepera), northern shoveler (Anas clypeata) are increasing. Common pochard (Aythya ferina), tufted duck (A. fuligula), red-crested pochard (Netta rufina), and black-tailed godwit (Limosa limosa) are relatively new birds along the Rhine (Tittizer & Krebs 1996). The zebra mussel is an important food source of benthivorous waterbirds. Lake Constance, IJsselmeer/Markermeer and Randmeren with their high mussel standing stocks are important resting areas for tufted duck, common pochard and greater scaup (Aythya marila).

6.6.9. Mammals The native mammals of the floodplains along the Rhine originally included the harvest mouse (Micromys minutus), root vole (Microtus oeconomus), garden dormouse (Eliomys quercinus), hazel dormouse (Muscardinus avellanarius), black rat (Rattus rattus), brown rat (R. norvegicus), urus (Bos primigenius), moose (Alces alces), red deer (Cervus elaphus), roe deer (Capreolus capreolus), wild boar (Sus scrofa), European badger (M. meles), wildcat (Felis silvestris), bats (Nyctalus noctula, Leucone daubentoni, Leucone dascyneme), Eurasian water shrew (Neomys fodiens), Miller’s water shrew (Neomys anomalus), European water vole (Arvicola amphibius), European beaver (Castor fiber), Eurasian otter (Lutra lutra), brown bear (Ursus arctos) and gray wolf (Canis lupus) (Tittizer & Krebs 1996). Wolf, bear and moose already went extinct in the Middle Age. Purely aquatic mammals occasionally make their way into the Rhine, for example the Beluga whale (Delphinapterus leucas) in the 1960s (Gewalt 1967) or the today rare harbour porpoise (Phocoena phocoena), which regularly occurred in the Lower and Delta Rhine before World War II. Apart from a few locations, most semi-aquatic mammals are now extinct. The European beaver, a riparian keystone species, was hunted almost to extinction in Europe for fur and castoreum. After re-introduction in France, Switzerland and the Lower and Delta Rhine, beaver populations have expanded along the Rhine. In 1988, beavers from the Middle Elbe region were re-introduced in the natural areas Biesbosch and Gelderse Poort (Nolet & Baveco 1996). The Eurasian otter (L. lutra) considered as a noxius fish predator was hunted to extinction in most parts of the Rhine. Habitat loss and pollution enhanced the decline of otter populations, even though the species became protected. Otter populations are still decreasing, mostly from habitat loss and reduced fertility induced by heavy metals, pesticides, and chlorinated biphenyls. Today, otter populations are only known in the Dutch part of the Rhine. After extinction of the otter in the Rhine Delta in 1988, measures were taken to restore otter habitat in lowland peat marshes in the north of the country, and reintroduction of otters began in 2002. The population remains vulnerable to ex-

tinction due to high mortality from traffic (Lammertsma et al. 2006). The muskrat (Ondatra zibethicus) is a large, stout, semi-aquatic rodent native to North America. In 1907, this species was introduced in Bohemia (near Prague) for their thick and water-resistant fur. Some animals inevitably escaped from fur farms and others were released on purpose (Hengeveld 1989). The dispersal of muskrats varies between 1 and 25 km/year (Andow et al. 1990). In 1930, muskrats also escaped from a fur farm near Belfort (France) and invaded the Rhine–Rh^one canal, the Ill River in northwest France and western Germany. Muskrats now inhabit the entire European continent, including the Rhine catchment. Water authorities in the Rhine Delta consider the muskrat to be a pest that must be exterminated. Its burrowing causes extensive damage to dikes and banks of drainage ditches, and they are trapped and hunted to keep the population low. From 1987 to 2006, the average trapping efficiency decreased from 0.83 to 0.46 animals per hour, indicating a decrease in the muskrat population in the Rhine Delta (LCMM 2007). Trees in the floodplain forest mainly along oxbows of the Upper Rhine provide excellent habitats for bats such as pipistell bats (Pipistrellus pygmaeus, Pipistrellus nathusii, Pipistrellus pipsitrellus, Plecotus auritus), Brandt’s bat (Myotis brandtii), Noctule bat (N. noctula), Leisler’s bat (Nyctlaus leisleri), Daubenton’s bat (Myotis daubentonii), Natterer’s bat (Myotis nattereri) (Fuhrmann et al. 2002). Large colonies of greater mouse-eared bat (Myotis myotis) using old use old buildings (churches) as roosting sites can be observed in the valley of the Middle Rhine, Moselle and Lahn River during summer.

6.7. MANAGEMENT AND CONSERVATION 6.7.1. Economic Aspects With a population of about 58 million, the Rhine basin is an important player for the economy of Europe. The Rhine basin has developed into one of the world largest areas in the chemical industry, historically profiting from the availability of energy (coal), raw materials (coal, salt, limestone) and transport facilities (Rhine navigation) (Hopp 1990). The industry is concentrated around Basel, the Rhine-Main area between Ludwigshafen and Frankfurt, the Lower Rhine between Cologne and D€usseldorf, and most recently Rotterdam. Rotterdam has the largest oil terminal in Europe and contains a huge petrochemical industry with numerous refineries of large international oil companies. About 50% of all inland navigation within the European Community takes place on the Rhine, with about 311 million tons of goods and 700 ships daily crossing the border between The Netherlands and Germany (Zentralkommission f€ur die Rheinschifffahrt 2003). ‘Duisport’ at Duisburg (Rkm 780), the largest inland port in the world, handles about 70 million tons of goods

234

annually. The transport of containers has increased remarkably from 450 000 twenty-feet equivalent units (TEU) in 1991 to 900 000 TEUs in 1997. Large-scale hydroelectrical power production along the Rhine started in the late 19th century. Between the Alpine Rhine and the sea, 24 run-of-river powerplants produce 7.3 TWh/year. Within the entire Rhine basin, more than 2000 hydroelctrical powerplants produce about 15–20 TWh/ year; most of these plants are in the upper tributaries. The Rhine basin also has 10 nuclear powerplants (with up to four reactors) with an installed electrical power of 19 GW for which the Rhine, and the rivers Aare, Moselle and Neckar, provide cooling water. The Rhine, its tributaries, and lakes, supply drinking water for around 25 million people. Under the umbrella of the International Association of Waterworks in the Rhine catchment area (IAWR), 120 waterworks annually provide 2.73 billion m3 of raw water (IAWR 2000). Because of the existing risk of accidental pollution, the International Commission for the Protecton of the Rhine maintains a warning alarm system. The Rhine Alarm Model has been developed to forecast concentrations of harmful substances in the river, thereby allowing waterworks to take necessary measures (Broer 1991). The system covers the Rhine from Lake Constance to the sea, including the tributaries Aare, Neckar, Main and Moselle. Seven international alarm stations are on the Rhine mainstem between Basel and Arnhem. Fishery, once an important activity along the Rhine, is today of minor economic importance. In Lake Constance, commerical fishermen caught on average (1996–2000) 1130 tons of fish (76% whitefish, 17% perch), yielding approximately 3 million Euro. In the High Rhine, only two commercial fishermen remain (Brenner et al. 2003). Traditional fishery is practiced by 80 fishermen in the southern Upper Rhine, and in the 640-km long stretch between Iffezheim and the Dutch–German border there are about 48 active, but part-time, fishermen. According to Raat (2001), only 10 fishermen are engaged in the fishery at the Rhine– Meuse delta. In contrast, recreational fishing is done by several hundred thousand people in the main stem of the river and adjacent floodplain waterbodies. Target species are roach, bream, ide, pikeperch and pike, and in the High Rhine also brown trout and grayling.

6.7.2. Floods and Flood Defense Extreme runoff from the Alpine region, including the Aare drainage and the three catchments of the Neckar, Main and Moselle, determines the occurrence of catastrophic Rhine floods (Disse & Engel 2001). According to the hydrological record of the last 1000 years, catastrophic floods did not occur simultaneously in all sub-basins. Because of different meteorological conditions and the respective hydrological response of the different catchments, Rhine floods show a regional pattern (IKHR 1999). In a large river system such as

PART | I Rivers of Europe

the Rhine, the frequency of flow extremes (floods and droughts) show decadal variability that reflect changes in atmospheric circulation modes (Jacobeit et al. 2003; Pfister et al. 2006). Floods in the Alpine area (including the forelands) that usually occur between spring and autumn have a minor impact in the Middle and Lower Rhine. Large lakes in the Alpine forelands have important retention volumes regarding flooding; for example, in 1999 these lakes retained 950 106 m3 within 5 days, corresponding to an additional discharge of 2200 m3/s in Rheinfelden (Rkm 148). Between the northern Upper Rhine and the sea, severe floods mainly occur during winter (major rainfall often associated with snowmelt in the central European uplands). Flood damage caused by drifting ice was frequent between the 16th and 19th century (Krabe 1997). Before the 19th century, flooding along the Rhine only affected the relatively small population living in the floodplains (Pinter et al. 2006). Since the Middle Ages, floodplain residents tried to protect settlements but these efforts were local and poorly coordinated. For example, the use of groyne-like structures in the Alpine Rhine directed flow to the opposite bank and caused enhanced erosion during floods. This and poor maintenance of flood protection structures resulted in conflicts between municipalities variously affected by floods. Even in the 19th century when the large regulatory project of the Upper Rhine was realized, concerns by Prussia and Rhine Hessen that flood hazards were shifted downstream led to discussions with the Grand Duchy of Baden (Bernhardt 1998). The regulation and harnessing of the fluvial hydrosystem in the last century have reduced the hydromorphological resilience of the Rhine river basin. For example, river engineering of the 20th century (Grand Canal d’Alscace, the construction of 10 powerplants) in the southern Upper Rhine resulted in the loss of 130 km2 (60%) of the existing retention areas. Today, inundation areas equal 450 km2, which corresponds to about 30% of the inundation area at the beginning of the 19th century (IKHR 1999). The increased channel depth accelerates flood waves and the loss of retention areas steepens flood hydrographs. The flood waves of the Neckar, once preceding that of the Rhine, now coincides with those of the Rhine and increase peak flows of a 50–60 year flood by 700–800 m3/s downstream of the confluence (Disse & Engel 2001). Because hydromorphodynamic processes can be controlled to a great extent, residents of riverine areas have lost their sense of the natural dynamics of river ecosystems. Further urbanization of areas prone to flooding took place without the potential risks of flooding being recognized, in particular in the lowlying polders in the Rhine Delta (Van Stokkom et al. 2005). Today, potential flood damage along the Rhine is estimated at 165 billion Euro, and flood magnitude and frequency have increased significantly during the 20th century (Pinter et al. 2006). The Rhine floods in the winters of 1993 and 1995 severely affected the stretch between the Middle Rhine

235

Chapter | 6 The Rhine River Basin

TABLE 6.5 Flood defense projects in the Rhine basin (Van Rooy & Van Wezel 2003) Project

Trans-national cooperation

Effect on water discharge

Effects on landscape quality

Public participation

Degree of innovation

Restoration of river confluences Kinzig and Schutter (G) Restoration of Rhine meanders and floodplains along the Rhine river section Kunheim and Marckolsheim (F) Infiltration of rainwater in urban area of Neuenberg am Rhein (G) Realization and management of retention areas along the Rems River (G) Infiltration of rainwater in rural area of Massenbachhausen (G) Dike relocation Worms-B€ urgerweide (G) Realization of retention areas along the Alzette River (L) Floodplain rehabilitation (Klompenwaard) with construction of side channels (NL) River dike relocation, creation of side channel and floodplain lowering location Bakenhof along Nederrijn River (NL)

+ +

+ +

++ ++

+ 0

+ ++

0

0*

+

++

0

+

+

+

++

+

+ ++ + +

+ ++ + ++

+ ++ ++ ++

+ + 0 +

++ + + +

+

+

++

+

+

F: France, G: Germany, L: Luxembourg, NL: The Netherlands. * Positive effects are expected after upscaling of the measures.

and the Delta. During the 1995 flood, about 250 000 people had to be evacuated in the Delta area; the economic damage reached about 1 billion US$ (Van Stokkom et al. 2005). These and similar events in several other large European rivers caused a considerable change in government policy, public awareness, and international cooperation in terms of sustainable flood protection (Smits et al. 2000). Riparian countries now aim to create more space for the river, combined with objectives from other policy areas, including improvement of spatial quality and ecological rehabilitation (IKSR 1998). Each riparian country was to select appropriate measures to restore the hydromorphological resilience of their relevant part of the river basin, from the perspective of the river basin as a whole. Up to now, riparian countries have made considerable progress in selecting and implementing the measures of the Rhine Action Plan on Flood Defense (ICPR, 1998). This plan aims to: (1) reduce risk damage by 10% by 2005 and 25% by 2010, (2) reduce peak flood stages by 30 cm by 2005 and 70 cm by 2010, (3) enhance the awareness of flood risk by the publication of risk maps and 4) improve the flood alarm system. In addition, a joint flood control program was completed within the framework of Interregional Rhine–Meuse Activities. Whenever the amount of water is reduced or retained before it reaches the main river, the peak flood level is diminished and the risk of flooding reduced. Relevant measures in the Rhine catchment are (www.irma-programme.org): (1) restoration of the natural course of tributaries and their overflow areas by restoring streams, creating and restoring of meanders, and restoring floodplain vegetation to retain water, (2) reduction of the discharge from residential and industrial areas by water infiltration and improving

the porosity and absorption of soil and (3) creating retention and overflow areas. Important measures in lowlands and the delta are, roughly ranked in order of decreasing efficiency (Van Stokkom et al. 2005): (1) moving dikes further inland, (2) constructing river bypasses, (3) lowering and restoring groynes, (4) dredging the riverbed in sections of the river where sedimentation occurs, (5) removing obstacles such as non-flooding areas in the floodplain, summer embankments and ferry ramps and (6) lowering floodplains, that is, by digging side channels, frequently combined with land-use changes from agriculture to habitat restoration and recreation. Moreover, polders can be created for temporary or emergency storage of river water in the floodplains. Table 6.5 gives examples of innovative flood management measures and evaluates the efficiency, transnational cooperation and public participation of some representative projects in various parts of the Rhine basin.

6.7.3. Conservation and River Rehabilitation The socio-economic development along the Rhine has profited enormously from the Rhine regulation, because it afforded a high level of flood protection, an efficient navigation route, and high agricultural yields. On the other hand, the regulation has led to large-scale river responses such as tilting of the riverbed through erosion, deterioration of riverine habitats and loss of the natural morphological dynamics. In face of the dramatic decline of biodiversity and the lacking recovery of extinct species despite of the significantly improved water quality indicate the need to improve riverine habitat quality. The IKSR program Rhine 2020 (IKSR 2002d) focus on the biological diversity of the Rhine system. Target species within this program is not only the Atlantic

236

salmon but also plants and animals of the riverine Rhine fauna. Measures to meet the high ecological demand of the salmon include habitat restoration, floodplain activation, removal of migration barriers and developing a habitat network. The need to establish retention areas to mitigate floods provide opportunities for local rehabilitation projects. However, the extent of human occupation and related human activities of the floodplains, navigation and hydropower production only allows a partial return natural conditions (see also EU Water Framework Directive). The execution of the Delta project, which followed centuries of smaller interventions, triggered several (unexpected) environmental problems (Lenders 2003). It can be concluded that the long-term hydromorphological and ecological effects of the interventions in the Rhine delta were not foreseen or at least underestimated (Nienhuis & Smaal 1994; Havinga & Smits 2000; Smits et al. 2000, 2006). The building of Delta dams disconnected the hydrology and ecology along the river, both at the sea as well as between the river and floodplains (Smits et al. 2006). Ecological landscape units, especially alluvial forests, natural levee pastures, marshy floodplain pastures and side channels, have almost disappeared from the landscape (Middelkoop et al. 2005). Furthermore, water pollution and the facilitation of invasive species by connecting several large European rivers via canals have had profound impacts on the diversity of native species in the Rhine delta (Van den Brink et al. 1994, 1996; Cals et al. 1998; Grift 2001). Recently, efforts have been made to reverse the trend in river regulation and deterioration of riverine ecosystems in the Rhine delta (Bij de Vaate 2003; Lenders 2003; Buijse et al. 2005). Efforts include improvements in water quality and rehabilitation of more natural patterns and processes akin to river-floodplain ecosystems. Rehabilitation measures include removal of summer dikes, displacement of winter dikes, (re)creation of side channels, excavation of polluted floodplain topsoils, and a management change from agricultural management to a strategy that includes the influence of river dynamics and low-density grazing by horses and cattle. These measures increase the surface area of riverine ecotopes, like natural levee pastures, river dunes and alluvial forests, which became rare. In the Rhine delta, the effects of environmental rehabilitation programs are promising but still limited by strong boundary conditions for safety and navigation (Nienhuis et al. 2002; Van der Molen & Buijse 2005; Van Stokkom et al. 2005). Although rehabilitation processes have been locally successful, the various projects did not significantly contribute yet to ecological recovery of the river at a coarser scale.

6.7.4. EU Water Framework Directive The EU Water Framework Directive (EU WFD, http://ec. europa.eu/environment/water/water-framework/index_en. html) implemented in October 2000 sets a common frame-

PART | I Rivers of Europe

work committing member states to protect and enhance all natural surface, ground, coastal and estuarine waters and aims to achieve a good qualitative and quantitative status in 15 years with regulated waterbodies to be developed to their ecological potential. The general approach is management by river basin similar to the initiatives taken earlier for the Meuse, Scheldt or Rhine basins by respective riparian states. The implementation of the EU WFD includes several steps such as identification of river basin districts and authorities (2003), characterization of river basins such as pressures, impacts and economic analysis, establishment of monitoring networks (2004), basin management plans including programs of measures (2006), and making operational programs of measures (2008). The implementation of the EU WFD is coordinated by a committee with representatives of the nine riparian states closely cooperating with International Commission for the Protection of the Rhine (ICPR). The report ‘Assessment of the status of the Rhine Basin’ has been submitted to the European commission in spring 2005 (http://www.iksr. org/index.php?id=102 and http://www.iksr.org/index.php? id=103). It documented the severe hydromorphological alteration of the Rhine and its tributaries. A large number of waterbodies fell in the categories artifical (e.g., channels, flooded gravel pits) or considerably modified (e.g., most of the Rhine mainstem and its major tributaries), where the probability of reaching WFD goals is low or unclear (Koordinierungskomitee 2005). The most frequent cause that waterbodies fell in the category ‘low probability reaching a good status’ was impacts affecting hydromorphological integrity. With respect to chemical status, it is expected that the WDF goals can be met upstream of Basel and in the Neckar River but more downstream these goals may not be reached. Monitoring programs for the Rhine basin have been ready since 2006; they include assessment of physico-chemical parameters and harmful chemical compounds at 20 stations along the main stem between Reichenau (Alpine Rhine) and the sea, hydromorphology, and biological quality (phytobenthos and plankton, benthic invertebrates, fish at 14 stations a long the main stem) (Koordinierungskomitee 2007).

6.8. THE MAJOR RHINE TRIBUTARIES 6.8.1. Aare The 295-km long Aare River drains a basin of 17 606 km2 that includes parts of the Alps, northern Alpine forelands (Swiss Plateau), and southern Jura Mountains. Elevations within the catchment range from 4274 m asl (Finsteraarhorn) to 311 m asl (confluence with the Rhine). About 2.1% (370 km2) of the catchment is glacierized, 28% are forested and 36% used for different agricultural activities (Table 6.1). Precipitation averages 1490 mm and runoff 1003 mm. The human population is 3.4 million (192

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Chapter | 6 The Rhine River Basin

people/km2) and mainly concentrated in the Swiss Plateau. Industrial activities within the Aare catchment were traditionally machine and the electrical equipment manufacturing particularly in the region of the Aare-Limmat-Reuss confluence. Banking, insurance, financial services, information and communication technologies make the metropolitan area of Zurich to the economic center of Switzerland significantly contributing to the high annual gross domestic product of about 65,000 US$ per person in the Aare basin (Table 6.1). Meltwater from the Upper (2430 m asl) and Lower Aare (1950 m asl) glaciers are the primary water source of the Aare River. The upper 20 km of the Aare valley are relatively steep (8%) and narrow. Between the relatively flat basin of Innertkrichen and the plain of Meiringen, the river cuts through a limestone ridge and forms a spectacular canyon (Aare gorge). About 40 km from the source, the Aare (Qmean 35 m3/s) flows into the turbid and oligotrophic Lake Brienz (564 m asl, volume 5.2 km3, area 29.7 km2), which is also the recipient of the L€ utschine River, a glacial river with a Qmean of 19 m3/s. After a 5.5-km long riverine stretch, the Aare then enters the oligo/mesotrophic Lake Thun (558 m asl, volume 6.5 km3, area 48 km2). The Kander River, a major alpine tributary (Qmean 32 m3/s) also flows into Lake Thun. The lowest stretch of the present Kander was the location of the first major river engineering project in Switzerland, which, however, lacked a serious evaluation of the potential consequences (Vischer 2003). The Kander originally joined the Aare downstream of Lake Thun. Sediment accumulation at the confluence resulted in frequent flooding of adjacent settlements. To mitigate this problem, the Kander was diverted through a tunnel into Lake Thun (1714 AD). The tunnel collapsed and a steep gorge was formed and the river started to build a delta. The increased discharge in Thun caused severe damage to the town at the lake outlet that required adjustments of the Aare bed downstream of Thun. From Thun, the Aare flows for 80 km northwards across the Swiss plateau towards Lake Biel (429 m asl, volume 1.24 km3, area 39.3 km2) at the fringe of the Jura Mountains. Here it picks up the waters of the Saane River (Qmean 54 m3/s). Incised meanders characterize the river near the city of Bern before the powerplant of M€ uhleberg forms a 12-km long narrow lake. Until the first Jura Correction Project (1868–1878), the Aare did not drain into Lake Biel but meandered eastward through a relatively flat area with extended wetlands, once part of prehistoric Lake Solothurn. The Aare was redirected into Lake Biel and from there through a new canal to the old river channel 12 km east of the Lake. Because flooding continued, a weir was installed to regulate lake levels (1939) and canal capacities were increased (1962–1973). From Lake Biel, the Aare flows in a wide valley in an east-northeast direction along the southern fringe of the Jura Mountains for about 90 km. The Emme, a flashy prealpine river (Qmean 19.2 m3/s) is the largest tributary of this Aare reach. Rapids occur near the

town of Olten where the river cuts through the most southern anticline of the Jura Mountains and in the town of Brugg where the bedrock channel narrows to 10 m. Downstream of Brugg, about 15 km before the confluence with the Rhine, the Aare gains the waters of two major Alpine tributaries, the Rivers Reuss (Qmean 140 m3/s) and Limmat (Qmean 102 m3/s). It then turns north and crosses the Jura Mountains through a wide valley. At the confluence, mean annual discharge (1931 to 2003) is 559 m3/s. Monthly discharge is maximum in June (826 m3/s) and minimum in January (407 m3/s) (Figure 6.6). A peak flow was recorded in May 1999 at 2620 m3/s. The Aare is strongly influenced by power production. A complex scheme of nine powerplants and seven reservoirs are found in the headwaters; the installed power equals 1062 MW. Residual flow below reservoirs and hydropeaking are typical events upstream of Lake Brienz. Reservoir storage (>190 million/m3) influences seasonal discharge patterns, that is, low flows during summer and enhanced flows during winter. Between Lake Biel and the confluence, a chain of 12 run-of-river powerplants (installed between 1882 and 1970) impound major parts of the river, and also provide cooling water for three nuclear power plants. An eco-morphological assessment of the Aare between Lake Brienz and the border showed that only 9% of the river was judged as natural or near-natural, whereas the percentage of strongly affected stretches was 75% (GBL 2006). Concentrations of nutrients measured before the confluence with the Reusss and Limmat were 1.72 mg NO3–N/L and 0.014 mg PO4–P/L. Corresponding values in the Reuss were 0.85 mg NO3–N/L and 0.007 mg PO4–P/L, and in the Limmat 1.19 mg NO3–N/L and 0.013 mg PO4–P/L. Phosphate concentrations distinctly declined since the 1980s in contrast to nitrate in which only a slight reduction was observed since the early 1990s. Concentrations of major nutrients are similar to those of the High Rhine upstream of the Aare confluence.

6.8.2. Neckar The Neckar basin covers an area of 13 950 km2 consisting of 53% agricultural land and 36% forest (Table 6.1). Precipitation averages 757 mm and runoff 337 mm. The population is about 5.3 million, corresponding to a population density of 380 inhabitants/km2. The 367-km long river originates as an outflow of a wetland (Schweninger Moos, 706 m asl) at the Danube–Rhine divide near the eastern fringe of the Black forest. From there it flows as a small stream northwards across the high plain of Baar. Downstream of the confluence with the Eschbach (Qmean 2.5 m3/s), the Neckar enters a narrow valley. After 20 km, the river turns northeast continuing its course between the spurs of the Black Forest and the heights of the Swabian Alb. At Plochingen (Qmean 46.4 m3/s), the river changes

238

its direction to northwest for about 140 km. The most important tributaries, Fils (Qmean 9.6 m3/s), Jagst (Qmean 17.0 m3/s), Enz (Qmean 20.9 m3 /s) and Kocher (Qmean 22.1 m3/s) enter the Neckar here. At Eberbach, the Neckar bends westward and flows through the Odenwald range before it merges with the Rhine in Mannheim (95 m asl). Mean annual discharge at the confluence is 149 m3/s (MUV BW 2005). Monthly flow is maximum in February and minimum in September (Figure 6.6). Flow variation is typically high; for example, the ratio of average base flow to average high flow is 1:210 at the gauging station Plochingen. The alternation between confined and unconfined reaches characterizes the Neckar valley. Confined reaches occur were the river has eroded through calcareous Triassic sediments and include features such as incised meanders and oxbows. In areas where soft sediments (marl, clay) prevail, the valley is wide with extensive floodplains. In the 203-km long stretch between Mannheim and Plochingen, the Neckar has been regulated as a federal waterway. Regulation included the construction of separate navigation canals and numerous weirs with locks. Beginning in 1921, the work continued until completion of the last lock near Plochingen in 1968. The depth of the navigation channel is maintained at a miniumum of 2.8 m using 27 weirs with locks (26 are used for hydroelectrical power production.). In 2007, the transport of goods on the river was 7.5 million tons and 8100 cargo ships passed the locks; the transport of containers was 32 500 TEU. The inland port of Heilbronn had a cargo throughput of 4.5 million tons in 2006. The Neckar also provides cooling water for the nuclear powerplant of Neckarwestheim (2235 MW). Parts of catchment are heavily industrialized, such as areas in Stuttgart, Sindelfingen, Neckarsulm, Heilbronn and Mannheim where population density reaches up to 910 people/km2. The manufacturing industry includes mechanical and electrical engineering, and automobile construction. Human activities strongly affect the Neckar and its tributaries, primarily through industrial activities, navigation and agriculture. The 27 weirs in the navigable reach and an additional 18 powerplants impound the river almost along its entire course. Moreover, connectivity between the Neckar and its major tributaries is severely impeded by sills. Water quality is affected by the outfall of treated sewage from industrial and urban facilities and by diffuse inputs from agricultural areas. In 2003, concentrations of nitrate and phosphorus averaged 4.5 mg N/L and 0.17 mg PO4–P/L at the confluence in Mannheim, exceeding by far the respective concentrations in the Rhine (see Table 6.4). Floods of the Neckar and tributaries caused severe damage in the range of 10 to >300 million Euros. The project IkoNE- ‘Integrating Conception of the Catchment Area of the Neckar River’ by the Water Resource Administation of the State of Baden-W€ urtemberg, with a budget of 200

PART | I Rivers of Europe

million Euros is focused on flood mitigation but also includes measures to improve the structure and quality of the river.

6.8.3. Main The catchment of the Main River (27 251 km2) is in the northern part of the south-German scrapland. Land use consists of 54 agricultural land and 38% forest (Table 6.1). The population is 6.6 million people, corresponding to an average population density of 242 individuals/km2. Precipitation averages 655 mm and runoff 255 mm. Headwaters of the 524-km long river are the Red Main originating in the Franconian Jura with a source at 580 m asl, and the White Main. The source of the White Main (878 m asl) is in the Fichtelgebirge, a mountain range in eastern Bavaria with elevations up to 1053 m asl. The Red and White Main merge at Kulmbach, where the Main then flows west. Uplands extending from north to south divide the catchment into several sub-basins, and results in the characteristic course of the river that includes large bends with amplitudes of 50 km. The most important Main tributary is the River Regnitz (Qmean 51 m3/s), which merges with the Main near the town of Bamberg. Annual discharge of the Main at Bamberg is 43.4 m3/s. Other tributaries such as Fr€ankische Saale (Qmean 16.7 m3/s), Tauber (Qmean 8.7 m3/s at Tauberbischofsheim) and Nidda (Qmean 10.7 m3/s) are relatively small. Monthly flow of the Main is maximum in March and minimum in September (Figure 6.6); mean annual discharge at the confluence is 225 m3/s (BSUFV 2004). The ratio of average low flow to average high flow is relatively high at 1:20. The river is characterized by winter floods caused by rainfall and snow melt. To feed the Main–Danube canal at the Rhine–Danube divide, and to increase the base flow of the Regnitz and upper Main, 150 million m3 water are annually pumped (corresponds to 4.75 m3/s) from the Altm€uhl (Danube catchment) to the Main drainage. The Main has been used for cargo navigation since Roman times. From the 1880s until 1962, the river was developped to a waterway for large cargo vessels. The 388-km long stretch between the confluence and Bamberg has been transformed into a chain of impoundments encompassing 34 weirs with locks and stabilized banks. The Main–Danube canal, 55-m wide and 4-m deep, begins at Bamberg and ends after 171 km in Kehlheim at the Danube. Sixteen locks are used to overcome the 175 m altitudinal difference between Bamberg and the Rhine/Danube divide and the 68 m altitudinal change between the divide and the Danube. In 2006, the transport of goods on the Main was 18.8 million tons and 22 316 cargo vessels passed first Main lock near the confluence. Transport of goods on the Main–Danube canal was 6.24 million tons. Main River water quality is affected by point sources such as sewage treatment plants that release 10 591 tons

239

Chapter | 6 The Rhine River Basin

total nitrogen and 729 tons total phosphorus, and diffuse agricultural inputs. Industrial discharge is substantial, particularly in the heavily industrialized lower Main but also along the Regnitz (industrialized areas of Nuremberg, F€ urth and Bamberg). Most Main stretches are judged as moderately polluted. Mass development of algae with subsequent oxygen depletion can occur in slow-flowing areas of impounded reaches. Overall, water quality has improved since the beginning of monitoring programs in 1960. Phosphorus and ammonia concentrations significantly declined but nitrate still remains high. Concentrations of phosphate and nitrate (average 2003–2004) at the confluence were 0.088 mg P/L and 4.7 mg N/L; concentrations in the Rhine at the confluence were 0.058 mg P/L and 2.41 mg N/L.

6.8.4. Moselle The Moselle River drains a catchment of 28 133 km2 that includes major parts of the Vosges, the Plateau Lorraine, and major parts of the Rhenanian Mountains. The catchment belongs to France (54%), Germany (34%), Luxemburg (9%) and Belgium (3%). Land use is dominated by agriculture (54%), and 37% of the catchment is forested. The population is 4.21 million people, corresponding to an average population density of 150 individuals/km2. Precipitation averages 841 mm and runoff is 365 mm. The source of the 544-km long Moselle is on the western slope of the Grand Ballon d’Alsace in the southern Vosges Mountains at an altitude of 715 m asl. From the source the river flows northeast to the town of Toul, where it flows near (12 km away) the Meuse River. This is the location where a Meuse tributary was captured by the Moselle during the Riss Ice Age to become the Upper Moselle. About 24 km downstream of Toul, the Moselle gains water from the Meurthe River (Qmean 40 m3/s), the largest tributary of the upper Moselle. Its headwaters also originate in the Vosges Mountains. The Saare River, originating in the northern Vosges and merging with the Moselle upstream of Trier, is the largest tributary of the Moselle (Qmean 80 m3/s). The Moselle flows from Trier through a narrow valley (200– 300 m wide), flanked by the Hunsr€ uck and Eifel Mountains in a northeast direction towards the confluence with the Rhine (59 m asl). This reach has many meanders incised in Devonian sediments. Long-term monthly discharge is maximum in January (572 m3/s) and minimum in August (212 m3/s) (Figure 6.6); mean annual discharge at the confluence is 328 m3/s (IKSMS 2005). In December 1993 and January 1995, Moselle peak flows (recorded at Cochem) reached 4164 and 3350 m3/s, respectively; these exteme flows substantially contributed to the devastating flood impact in the Lower and Delta Rhine. The Moselle is an important international waterway. In the Moselle Treaty of 1956, France, Gemany and Luxemburg agreed to develop the river as a waterway for

large cargo vessels. The agreement with Germany depended on the promise of France to abandon its plans of elongating the existing Grand Canal d’Alscace from Breisach to Strasbourg. By 1979, the river was developed to a length of 394 km, which required the construction of 28 weirs with locks. The navigation channel is 40-m wide and 3-m deep. Today, about 15–16 million tons of cargo are transported annually on the river. In the lower reach between the confluence and the French–German border, the waterway follows the main river channel. In upstream reaches, meanders are often bypassed by artifical sidecanals. Until the 1970s, industrial activities within the catchment were dominated by the coal and steel industries with centers at Thionville, Metz, and Sarbr€ ucken, but these have subsequently declined. Economic activities shifted to the car industry (Lorraine, Sarland) and service (Luxembourg, Saarland). Wastewater from coal and ore mining (Lorraine, Saarland, Luxembourg) are a still a source of pollution, despite declining mining activities. A soda industry and salt mining are located along the lower Meurthe. Chloride concentrations in the Moselle average 400 mg/L between Meurthe and Saar, and 200 mg/L between Saar and Rhine. The coal and steel industry left polluted areas that are a potential hazard for surface and ground waters. Input of nitrogen and phosphorus from agricultural areas, and to a minor extent from sewage treatment plants, result in excessive algal growth and oxygen depletion in slow-flowing areas of impounded reaches. At the confluence, concentrations of nitrate and phosphate averaged (2001–2005) 3.3 mg N/L and 0.124 mg P/L. The development of the Moselle and Saar Rivers to waterways for large vessel traffic severely affected river morphology, causing uniform cross-sections, stabilized banks, and loss of gravel bars. The numerous weirs also impede fish migration.

Acknowledgements We thank Leonie Bolwidt (Rijkswaterstaat Waterdienst, Arnhem) and Wilfried Ten Brinke (Blueland, Utrecht) for providing photos of the Delta Rhine, and the Dutch Ministerie van Verkeer and Waterstaat (Rijkswaterstaat) for permission to use temperature data. KMW received support by the Sonderforschungsbereich Bodenseelitoral (SFB 454) of the Deutsche Forschungsgemeinschaft. We thank the Global Runoff Data Centre (GRDC), Koblenz (Germany) and the Federal Office for the Environment for discharge data. The Federal Institute of Hydrology BfG in Koblenz (Dr. Fritz Kohmann), the Landesumweltamt f€ur NordrheinWestfalen, and the Landesamt f€ur Umwelt, Wasserwirtschaft und Gewerbeaufsicht Rheinland-Pfalz kindly provided water quality data. We also appreciate the helpful comments of Dr. J€org Lange (regioWASSER, Freiburg i./Br.).

240

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PART | I Rivers of Europe

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PART | I Rivers of Europe

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Chapter | 6 The Rhine River Basin

RELEVANT WEBSITES http://www.iksr.de/ International Commission for the Protection of the Rhine (ICPR/IKSR). http://www.dk-rhein.de/ Deutsche Kommission zur Reinhaltung des Rheins. http://www.chr-khr.org/ International Commission for the Hydrology of the Rhine basin (CHR). http://grdc.bafg.de/ Global Runoff Data Center

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http://www.bafg.de Federal Institute of Hydrology (Koblenz, Germany) http://www.rijkswaterstaat.nl/ Rijkswaterstaat - Waterdienst http://www.watermarkt.nl/ Watermarkt: Information about the Dutch National Monitoring. http://www.naduf.ch/ National Long-term Surveillance of Swiss Rivers’ (NADUF) programme http://www.hydrodaten.admin.ch/e/ Federal Office for the Environment. Hydrologcial foundations and data

Chapter 7

^ ne River Basin The Rho Jean-Michel Olivier

Georges Carrel

Nicolas Lamouroux

UMR CNRS 5023, Universit e Lyon 1, 43 Boulevard du 11 novembre 1918, F-69622 Villeurbanne Cedex, France

UR Hydrobiologie, Cemagref, 3275 Route C ezanne, CS 40061, F-13182 Aix-enProvence Cedex 5, France

UR Biologie des Ecosyst emes Aquatiques, 3 bis quai Chauveau, CP 220, F-69336 Lyon Cedex 09, France

Dole-Olivier Marie-Jose

Florian Malard

Jean-Paul Bravard

UMR CNRS 5023, Universit e Lyon 1, 43 Boulevard du 11 novembre 1918, F-69622 Villeurbanne Cedex, France

UMR CNRS 5023, Universit e Lyon 1, 43 Boulevard du 11 novembre 1918, F-69622 Villeurbanne Cedex, France

Universit e Lyon 2, Facult e de G eographie, Histoire, Histoire de l’art, Tourisme, 5 Avenue Pierre Mend es-France, 69676 Bron Cedex, France

Claude Amoros UMR CNRS 5023, Universit e Lyon 1, 43 Boulevard du 11 novembre 1918, F-69622 Villeurbanne Cedex, France

7.1. 7.2.

7.3.

7.4.

7.5.

Introduction Biogeographic Setting 7.2.1. General Aspects 7.2.2. Palaeogeography Physiography, Climate and Land Use 7.3.1. Landforms and Geology 7.3.2. Climate 7.3.3. Land-Use Patterns Geomorphology, Hydrology, and Biogeochemistry 7.4.1. Geomorphic Development of the Main Corridor 7.4.2. Hydrology and Temperature 7.4.3. Biogeochemistry 7.4.4. Bedload 7.4.5. Nutrients and Pollution 7.4.6. Heavy Metals and Organic Micropollutants 7.4.7. Pesticides 7.4.8. Priority Substances of the Water Framework Directive 7.4.9. Artificial Radionuclides Aquatic and Riparian Biodiversity 7.5.1. Algae 7.5.2. Macrophytes 7.5.3. Floodplain Forests 7.5.4. Aquatic Invertebrates 7.5.5. Non-native Species 7.5.6. Protected Species

Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

7.5.7.

7.6.

7.7.

7.8.

The Rh^ one Groundwater System and its Obligate Fauna (Stygobionts) 7.5.8. Fish 7.5.9. Fishes in the Swiss Upper Rh^ one 7.5.10. Fishes in Lake L eman 7.5.11. Fishes in the Downstream From Geneva and French Upper Rh^ one 7.5.12. Fishes in the French Lower Rh^ one 7.5.13. The Apron 7.5.14. Migratory Fishes in the Rh^ one 7.5.15. Amphibians 7.5.16. Reptiles 7.5.17. Birds 7.5.18. Mammals Management and Conservation 7.6.1. Economic Importance 7.6.2. Flood Control 7.6.3. Fishery 7.6.4. Conservation and Restoration 7.6.5. Restoration Activities and Potential 7.6.6. EU Water Framework Directive The Ain River 7.7.1. Geomorphology 7.7.2. Hydrology and Temperature 7.7.3. Biogeochemistry 7.7.4. Aquatic and Riparian Biodiversity 7.7.5. Management and Conservation ^ne River The Sao 7.8.1. Geomorphology 7.8.2. Hydrology and Temperature 247

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PART | I Rivers of Europe

7.9.

7.10.

7.8.3. Biogeochemistry 7.8.4. Aquatic and Riparian Biodiversity 7.8.5. Management and Conservation The Durance River 7.9.1. Geomorphology 7.9.2. Hydrology and Temperature 7.9.3. Biogeochemistry, Bedload and Sediment 7.9.4. Nutrients and Pollution 7.9.5. Aquatic and Riparian Biodiversity 7.9.6. Management and Conservation Conclusions and Perspectives Acknowledgements References

7.1. INTRODUCTION The Rh^ one links several valleys and rivers from the upper Alps with the Mediterranean Sea (Figure 7.1, Table 7.1). Although the same pre-Celtic name was given to the river upstream and downstream of Lake Leman, the present Sa^one River and Rh^ one downstream of Lyon were considered by the Greeks, Romans, and even recent historians as the main economic corridor between the Mediterranean Sea and North Sea (Braudel 1986). The Alps provided a strong economic and cultural unity to the Rh^ one throughout the last thousand years. One manifestation of this unity is the use of language since Roman Times; that being French around the Mont Blanc massif. Cities such as Sion, Martigny, Geneva, Yenne, Aoste, Lyon, Vienne, Valence, Orange, Avignon and Arles were founded by Romans or older groups and were politically and economically important to Rome. The Romans were still unified before the short Napoleonic period that allowed the conquest of Italy in the late 1790s. In modern times, Switzerland and France have distinguished the upper Rh^ one River between Lake Leman and the headwaters in the Valais region of Switzerland and the ‘French Upper Rh^ one’ between Lyon in France and Lake Leman. The distinction between these two entities on each side of Lake Leman was reinforced by the harsh topography, poor communication along the river, and difficult conditions for navigation (Photo 7.1). Since the late 19th century, embankment policies in Valais, hydropower developments in France, and a decrease in traditional navigation and fishery have decayed communication links even further. Today, the Rh^ one River is a highly regulated river, viewed as a large waterway for commerce. Forgotten is the fact that it represents about 60% of the freshwater inputs into the Western Mediterranean Sea. The Rh^ one is a major source of nutrients and particulate matter to the Mediterranean Sea (Alliot et al. 2003), and a major factor in sole fishery yields from the Gulf of Lyons (Salen-Picard et al. 2002). The public and politicians are increasingly aware of environmental problems and sociolo-

gists indicate a new interest towards integrating river environments in everyday life, so called ‘river re-appropriation by riverine people’. Recent floods also show that the Rh^ one, although regulated, can still overflow its banks and pose a risk hazard. Energy production, navigation, irrigation, tourism, habitat and biodiversity protection and cultural activities all must be taken into account by river managers and local decision-makers. The complex uses of the river have also caused new initiatives between Switzerland and France. In this chapter, we present the general physical, chemical and biological characteristics of the Rh^one River. All tributaries on the Swiss side are alpine rivers and have been used for water storage and hydroelectricity. Several tributaries from the French side play an important role in the Rh^ one discharge and are included in this chapter, the rivers Ain, Sa^one and Durance in particular. The Isere River also is an important tributary, but it was historically affected by regulation, channelization and industrialization and will not be discussed in detail. Lake Leman is an important feature of the river and its effects on the river downstream also are discussed in this chapter.

7.2. BIOGEOGRAPHIC SETTING 7.2.1. General Aspects The present morphology of the Rh^one valley is a result of the Riss and W€urm glaciations that deepened valleys in the Alps. The post-glacial colonization of the upper Rh^one above Lake Leman by aquatic organisms is still poorly documented, but a possible connection between the Upper Rh^one and Leman catchment and the Rhine catchment is believed to explain fish colonization in the Upper Rh^one. Today, the Rh^ one flows through three major ecoregions (Alps, Western Highlands and the Mediterranean part of the Western Plains) that encompass a large geographical gradient in altitude and latitude.

7.2.2. Palaeogeography The Upper Rh^one catchment lies inside the tectonic trench of Valais between the high mountains (>4000 m asl) of the crystalline Pennine Alps in the south and the northern sedimentary Bernese Alps. The folding of the Alpine Range and the Jura Mountains during the late Tertiary and Pliocene was from plate tectonics. The folds were pushed westward over the north–south tectonic trough of the Sa^one and Rh^ one, and abutted to the west by the tectonic margin of the Massif Central plateau from Hercynian folding of crystalline and metamorphic rocks. The geological history of the Rh^ one between Lake Leman and the Bas-Dauphine foreland is poorly documented. The present river cuts across anticlines through narrow trenches, following synclines before the southern Jura bend. To the west, the valley displays recent postglacial features. The former river may have flowed

Chapter | 7 The Rh^ one River Basin

FIGURE 7.1 Digital elevation model (upper panel) and drainage network (lower panel) of the Rh^one River Basin.

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PART | I Rivers of Europe

TABLE 7.1 General characterization of the Rh^ one River Basin Upper Rh^ one Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25%) ecological regions

1655 8018 5.77 162.4 4.3 2 2

Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparse vegetation Wetland Freshwater bodies

699 90 538 53.61 103.1 9.2 3 48; 70

Ain 669 3713 3.88 101.0 9.2 1 70

Sa^ one

Is ere

Durance

373 29 498 14.92 95.2 9.6 1 70

1463 11 865 10.63 130.6 6.5 3 2

1137 14 322 0.82 107.9 8.8 2 2; 48

3.6 10.6 5.2 23.6 16.8 32.5 0.1 7.6

4.3 30.1 10.7 36.7 10.7 6.0 0.6 0.9

3.6 16.7 20.0 53.8 4.0 0.1 0.5 1.3

4.9 38.0 20.3 34.4 1.4 0.0 0.1 0.9

2.9 13.6 6.2 34.4 19.3 22.9 0.0 0.7

1.3 20.5 1.7 38.0 23.9 14.1 0.0 0.5

1.4

9.5

1.1

0.4

31.9

12.2

1.2 1.2 3 0 17 5 2 190 26 721

1.1 1.1 3 6 35 16 1 98 24 262

1.0 1.0 3 5 27 11 0 61 23 298

1.1 1.1 3 0 30 11 2 94 24 410

1.0 1.0 3 2 21 9 1 82 25 506

1.0 1.0 3 9 27 16 0 32 22 787

Protected area (% of catchment) Water stress (1–3) 1995 2070 Fragmentation (1–3) Number of large dams (>15 m) Native fish species Non-native fish species Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person)

Rh^ one

For data sources and detailed explanation see Chapter 1.

PHOTO 7.1 Pfynwald in the Upper Rh^one valley in Switzerland (Photo: A. Peter). This is the largest dynamic section remaining along the Swiss Rh^one.

251

Chapter | 7 The Rh^ one River Basin

across the Jura Mountains or entered the Isere valley through the present Lake Bourget. The Sa^ one-Rh^ one trough was a tectonic rift in the early Tertiary, and was earlier connected to the Rhine rift. This rift shunted the Rhine River south towards Basel before creation of the present flow of the Rhine to the North Sea. The northern part of the Sa^ one-Rh^ one rift is presently drained by the Sa^ one River. The middle part of the rift, occupied by the Bas-Dauphine foreland between Lyon and Valence, is a large alluvial fan of sediments originating from the former Upper Rh^ one and Isere catchments. It was incorporated into the Alpine piedmont during the late Tertiary. The Rh^one then incised a course through the hard rocks of the Massif Central and the soft rocks of the Alpine piedmont, alternating between incised valleys and wide floodplain basins. The incision of the river also was influenced by the lowering of the Mediterranean Sea during the closure of Gibraltar Narrows, the so-called Messinian Crisis in the Pliocene between 5.3 and 5.9 million years ago (Gargani 2004). The re-connection of the Atlantic Ocean and Mediterranean Sea inundated the Rh^ one gorge and deposited Plaisancian clay up to Lyon (1.8– 4.9 million years ago). The level of the Mediterranean Sea decreased by about 120 m during the Quaternary glaciation, changing the longitudinal profile of the Rh^ one several times. The present lower Rh^ one, including the Camargue delta, was built up by sediments from tributaries and eroded fluvioglacial terraces of the W€ urm glacier that covered part of the Bas-Dauphine foreland.

7.3. PHYSIOGRAPHY, CLIMATE AND LAND USE 7.3.1. Landforms and Geology The Rh^ one is an 8th order 812 km long river, of which 512 km flows downstream from Lake Leman. Its catchment covers about 98 500 km2 with 90 500 km2 of this in France. It is mainly an Alpine river with 50% of the catchment above 500 m asl and 15% above 1500 m asl. The river originates from the Furka Glacier (2341 m asl), and drains the Valais region in Switzerland. Downstream from Lake Leman, it crosses the folded area between the Alps and Jura mountains, flowing north of the Bas-Dauphine alluvial fan. West of the Jura, the Rh^ one receives the Ain River, a right bank tributary. In Lyon (163 m asl), it receives the Sa^ one River that flows from the Vosges mountains and drains the Bresse and Dombes plains. Downstream of Lyon, the river flows southward to the Mediterranean Sea. Tributaries flowing from the Alps such as the Isere and Durance are longer relative to the short steep rivers flowing from the Massif Central. The longest western tributaries are the Ardeche and Gard in the southern catchment. Although the western rim of the former rift is made of acidic rocks, most of the catchment is composed of alkaline rocks of Jurassic and Cretaceous sediments and Tertiary and Quaternary deposits.

7.3.2. Climate The Rh^one catchment includes several climatic zones of mostly oceanic influence with moderate precipitation in all seasons. Northern areas and mountains receive the highest precipitation and altitude affects the duration and thickness of snow cover. Eastern areas have summer storms of continental influence, and cold winter temperatures occur in the Sa^one valley. The southern part has a Mediterranean climate with hot and dry summers and rainfall mostly in spring and autumn. Total precipitation is around 600 mm/year in the southern valley, but rainfall can be intense (>600 mm in days) in the Cevennes Range (1600 m asl) in the southeast of the catchment in September and October. This area is influenced by warm, low-pressure air masses that flow over the northern Mediterranean Sea. The Valais in Switzerland, some inner Alpine valleys such as the Upper Isere and Arc River, and the Rh^one valley south of Lyon have lower rainfall and are influenced by northern ‘Mistral’ wind.

7.3.3. Land-Use Patterns The Rh^one catchment has a long history of human influence with agriculture and livestock breeding being active 6000 years ago. Archaeological studies have documented several periods of land clearance and land abandonment in the middle Rh^one valley (Van Der Leeuw 2005) that are associated with periods of soil erosion and of soil and forest recovery. The Roman and Medieval periods had warmer climates with extensive agriculture use in valleys and higher altitudes. The Little Ice Age was a period of increasing population size with densities averaging 100 inhabitants per km2 in mountain areas. High population densities occurred from 1840 to 1870 before increased emigration to cities and lower populations after the First World War. Highest deforestation in the Alps and Massif Central occurred during this population maximum. Today, over 30% of the Rh^one basin is forested and 80% of the production is used for timber. The types of forest range from coniferous (Abies sp., Picea sp.), hardwood (Quercus sp., Fagus sylvatica), and poplar plantations in alluvial valleys to fire-prone Mediterranean forest (mostly Pinus halepensis) developing on abandoned agricultural lands (Web site: EUFIRELAB, Laboratory for Wildland Fire Sciences and Technologies in the Euro-Mediterranean Region) (Curt et al. 2004). Present land use in the catchment is diverse because of pedologic, climatic and geomorphologic differences. Marked regional differences are associated with specific economic features and irrigation in alluvial valleys, in particular around the Mediterranean area. Mountain areas have been used mostly for livestock breeding and dairy production, but have been widely reforested during the last century. World-renowned vineyards are common on well-exposed slopes (Dangreaux 2002). The plains and valleys are rich agricultural areas, producing corn and cereals. Orchards, mostly apricot, peach and cherry, also have increased

252

because of new irrigation practices, and often extend into floodplains. Perfume and medicinal plants are produced in the southern Rh^ one, and walnuts are grown in the Isere River valley (ACO ‘Noix de Grenoble’). Rice production occurs on the Camargue delta, and fodder is an important irrigation crop in the south (ACO of ‘La Crau’ fodder). The north– south orientation of the catchment influences irrigation demands with a threefold difference between the upper Sa^one basin and the Mediterranean area. Agriculture used 2.8 billion m3 of surface water and 196 million m3 of groundwater in 2001 (DIREN 2005).

7.4. GEOMORPHOLOGY, HYDROLOGY, AND BIOGEOCHEMISTRY 7.4.1. Geomorphic Development of the Main Corridor The Upper Rh^ one in Switzerland drains steep headwaters and eventually flows through a large alluvial plain that enters Lake Leman. The average slope between the source and Lake Leman (164 km) is 0.9%. After the 1860 and 1861 floods, high levees and spurs constricting the riverbed were installed along the Upper Rh^ one. Between 1928 and 1956, the river channel was reshaped to be narrower and deeper, and the alluvial plain was dredged and developed (Meile et al. 2006). Another plan in the early 1980s (the so-called Hydro-Rh^ one project) aimed at developing hydropower with a series of 10 dams, but it was not implemented. The last ‘Rh^ one correction’ was begun in 2000 after the large 1987 and 1993 floods that threatened the valley. The main purpose is to widen the river and increase channel capacity, secure levees, and improve environmental quality (HYDRONAT 2000). The Rh^ one contributes 68% of the total water and provides suspended sediments into Lake Leman (Web site: EUROLAKES, Integrated Water Resource Management for Important Deep European Lakes and their Catchment Areas). Lake Leman is a warm monomictic lake of glacial origin created by a moraine dam at its western end. It has two basins: the eastern ‘Grand Lac’ (499 km2, maximum depth 310 m) and the western ‘Petit Lac’ (81 km2, maximum depth 76 m) (Web site of the International Commission for the Protection of Lake Leman, CIPEL). In Geneva, the Arve River enters the Rh^ one from the French Alps, delivering 500 000 tons/year of suspended sediment. Downstream of Geneva, the Rh^ one flows through a gorge in the lower Savoy plateau, then it widens across a narrow alluvial plain built up by sediments from the Arve and Fier rivers and small tributaries from the Jura Mountains. Upstream of Lake Bourget, the Chautagne and Lavours marshes are large peaty swamps originating in the early Atlantic period. The Basses Terres area at the Rh^one bend near the southern Jura Mountains has several preserved meander scars dating back to 7000 years BP (Salvador 1999,

PART | I Rivers of Europe

Bravard et al. 2002b) and a meander belt dated from the late Roman period (4th century AD). During the Little Ice Age, the river morphology changed from meandering to braided in response to an increased bedload from the Alps and more intense floods. The river downstream of Basses Terres is stable, straight and has a low gradient up to the confluence with the Ain River. Downstream of the Ain, the Rh^one passes the area beyond the W€urmian front morain of 18 000 years ago. Here is a wide, steep alluvial plain (slope of the river = 0.1%) with low terraces dating back 10 000 years BP, Holocene meander scars, and the remnants of a large braided belt from the Little Ice Age. Archaeologists and geomorphologists have reconstructed the past history of the river near Lyon, recording a braided belt dated 2800–2400 BP, Roman and Medieval meander scars, and a period of increased flooding during the 1st and 2nd century AD (Salvador et al. 2002). Historically, the Upper Rh^one in France was developed because it was used for navigation, mostly for the transport of stone and wood. After 1830, steamboats carried passengers between Lyon and the thermal resort of Aix-les-Bains on the eastern shore of Lake Bourget. Before the first railways in 1848, this reach was further developed to improve navigation. Completion of low embankments was completed in 1886 and river traffic slowly vanished. Public interests mostly involved flood protection measures. The large floods of 1840 and 1856 destroyed parts of Lyon that were located in the alluvial plain. The alluvial plains and Lake Bourget were recognised in 1857 as important water storage areas, and in 1858 a law forbid any embankments upstream of large cities such as Lyon. Consequently, all floodplains upstream of Lyon are still flooded by high flows (285 km2), except areas affected by recent construction of hydropower schemes. The Rh^one upstream of Lyon has been developed for energy production periodically between the end of the 19th century up to the 1980s (Table 7.2). First, dams were built near large cities such as Geneva (1884) and upstream of Lyon (1899), with the largest diversion dam built in Europe at that time. Next, upstream gorges were dammed by the Chancy-Pougny (1925), Verbois (1943) and Genissiat (1948) dams. A nuclear power plant called Bugey was built in the 1970s. An experimental fast-breeder reactor was run in Creys-Malville after 1986 but it is being dismantled. Last, following the high energy demand after the 1973 oil crisis, the National Rh^one Company (CNR) built a series of hydropower developments: Chautagne (1981), Belley (1982), Bregnier-Cordon (1984) and Sault-Brenaz (1986). These include a diversion dam that raises the height of the river and a power plant that uses the diverted flow. The old riverbed is used to accommodate flood flows that exceed the maximum operating flow of the plant (Photo 7.2). These large dams have impacted the river in many ways, but especially in the amount of stored sediments that must be flushed through the system at periodic intervals (Roux 1984).

253

Chapter | 7 The Rh^ one River Basin

TABLE 7.2 Hydroelectric development scheme along the Rh^ one River Name

Year of completion

Fall (m)

Reservoir length (km)

Maximum discharge processed (m3/s)

Maximum hydropower capacity (MW)

Mean production/year (Gwh/year)

Chippis Lavey Seujet Verbois Chancy-Pougny G enissiat Seyssel Chautagne Belley Br egnier-Cordon Sault-Br enaz Cusset Pierre-B enite Vaugris P eage-de-Roussillon Saint-Vallier Bourg-l es-Valence Beauchastel Baix-Le-Logis-Neuf Mont elimar Donz ere-Mondragon Caderousse Avignon Vallabr egues

1911 1950 1995 1943 1925 1948 1951 1980 1982 1984 1986 1899 1966 1980 1977 1971 1968 1963 1960 1957 1952 1975 1973 1970

88 34–42 3 34 10.7 67 8.5 15 17 13.7 9.7 12.2 8 6.7 12.2 11.5 11.7 11.8 12 16.5 22.5 8.6 10 13.5

– – – 11.4 9 23 5 5 5 12 28 19 11.2 19.5 15.7 19.5 11.1 15 8.8 9 28 11.5 12 18

65 220 550 530 520 750 600 700 700 700 700 600 1380 1360 1600 1650 2300 2100 2260 1850 1970 2400 2400 2200

41 69 6 100 38 420 42 90 90 70 45 63 80 72 168 120 186 192 210 270 354 190 200 210

245 400 20 466 210 1700 165 454 449 324 245 410 535 335 850 700 1100 1200 1200 1600 2140 840 935 1300

Downstream of Lyon, the Rh^ one flows north and south towards the Mediterranean Sea. The geomorphic features are less complex along this reach because of no glacial influence except during the G€ unz glaciation. River slope averages

By-passed section length (km)

8.9 17.2 11.4 1.8 18 9.8 – 12 3.7 8.9 6.4 8 13 29 5 2.6 6.3

Lock

No No Yes No No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes

0.05% and is controlled partly by bedload transport, sediment inputs from tributaries such as the Isere, and bedrock outcrops. Donzere trough, south of Montelimar, is a narrow reach 1 km wide shaped during the Pliocenic Sea PHOTO 7.2 Rh^one River: BregnierCordon by-passed section (Photo: J.M. Olivier).

254

PART | I Rivers of Europe

PHOTO 7.3 Rh^one River: L^one de Brotalet (restored side arm at Chautagne) (Photo: J.M. Olivier).

regression. The Rh^ one becomes wider as it flows across the Valence and Orange plains. The geomorphology of the middle Rh^ one between Lyon and Donzere are poorly documented, and extensive economic development has strongly modified the river landscape. The alluvial plains still show some Holocene meander scars along their margins. Before major developments in the 19th century, the Rh^one was a braided river from Lyon to the sea and every tributary from the Massif Central or the Alps delivered large volumes of coarse sediments during floods. Erosion also was intense in the deforested watersheds. During the Little Ice Age, braiding also dominated the Grand Rh^ one along the Camargue delta to its outlet into the Mediterranean Sea (Arnaud-Fassetta and Provansal 1999), and deposited sediments were redistributed along the shoreline by storms. Bedload data for the river indicate a reduction from 22 to 30 Mt/year at the beginning of the 20th century to 7.4–9.6 Mt/year at the end of this century (Pont 1997; Pont et al. 2002; Antonelli & Provansal 2002). A decrease in annual flood frequency at the end of the Little Ice Age caused this bedload reduction, along with changes in land-use mentioned above. The Camargue delta is a vast alluvial plain of 1450 km2 with numerous ponds and lagoons (Pineau and Sinnassamy 2001). The substrate is a thick layer of silt-clay alluvium and sand covering a shingle base from the Pleistocene (2 million years). The delta is a naturally dynamic and relatively recent sedimentary construction (developed since the eustatic rise of the Mediterranean Sea ca. 7000–6000 BP). Between 1895 and 1944, the delta area increased by 3.9 km2, then it decreased by 1.7 km2 between 1944 and 1990, and it increased again by 0.2 km2 between 1990 and 2000. Changes of the littoral fringe are associated with seasonal

variation in sediment inputs from the river. The littoral advances during high flows with high sediment loads and retreats during low flows with low sediment loads (Sabatier & Suanez 2003). The construction of coastal protection structures in the 1980s has limited coastal erosion (Provansal 2003). Downstream of Lyon, the Rh^one has large fertile alluvial plains protected since the late 18th century in some places and since the early 19th century in most areas. Farms and adjacent lands have been protected from floods by earthen levees built on the margin of and in the braided belt itself, but this did not prevent flooding from downstream. Cities like Avignon were prone to flooding, despite thick city walls. The lower Rh^one was developed for navigation after 1840 using a complex set of low dykes that maintained constant depth at low flow. Henri Girardon was the most noted engineer. Some river transport still occurred in the 20th century despite competition by two railway lines. In the early 1950s, management of the river by the CNR changed to a ‘triple target’; that is navigation, energy production and irrigation (‘Rh^one Law’ of 1921). From 1952 to 1980, 12 hydropower schemes were built between Lyon and the Gard River, producing 12 500 GWh/year. Four other nuclear power plants were built from 1980 to 1987: Saint-Alban (two PWR units of 1300 MWE), Cruas-Meysse (four PWR units of 900 MWE) and Tricastin (four PWR units of 900 MWE) (Table 7.2). The various river impoundments modified the natural slope of the Rh^one (Figure 7.2). A system of low dykes constrained the width of the former braided Rh^one into a narrow channel, while floods deposited sand and silt on river margins (i.e. on the former braided belt) that then became

255

Chapter | 7 The Rh^ one River Basin

FIGURE 7.2 Longitudinal profile of the R^one River bed before and after the construction of a chain hydropower plants.

densely vegetated with willows, poplars and maples. Former river arms were affected by heavy siltation, causing a loss in ecological diversity, and the hydraulics of floods changed since the capacity of the river decreased. In the mid-1980s, the CNR started a program to restore the connectivity of the dead arms. This program was enlarged to include ecological aspects in 1994 when a 10-year master plan for hydraulic and ecological restoration of the Rh^ one was launched and financed by the Water Agency, the Ministry of Environment, and the CNR.

7.4.2. Hydrology and Temperature The Rh^ one has an annual mean discharge of 1720 m3/s at its mouth, contributing 40% (with the Po River) of the freshwater inputs into the Mediterranean Sea (Poussard and

Madrid 1999). The Rh^one flow regime and its specific discharge of 17.8 L/s/km2 result from continuous mixing of glacier-melt, snowmelt and rainfall (Vivian 1989). The catchment can be divided into four large hydrological watersheds. The Swiss watershed from the source to the Lake Leman is dominated by high mountains averaging 1630 m asl and a glaciated area of 9.4%. Around 50% of the annual precipitation comes as snow. The flow regime of the Swiss Upper Rh^one is characterized by low flows during winter from November to April and high flows in late spring and summer due to snowmelt (Table 7.3, Figure 7.3). The French Upper Rh^one between Lake Leman and the Sa^ one confluence (length 200 km, mean slope 0.1%) has four major tributaries: the Arve flows from the Mont-Blanc range and joins the Rh^one in Geneva; the Fier and the Guiers flow from the foothills of the Alps; and the Ain flows from Jura. Lake Leman mitigates flood discharges downstream of its outlet. For example, large floods from the Swiss Upper Rh^one can reach 1000 m3/s, whereas flow at the outlet would not exceed 700 m3/s. Tributaries from the French Alps and Jura have different flow regimes with high flows in spring (Fier and Guiers), summer (Arve River) and winter (Ain River). The middle Rh^one from the Sa^one River confluence (163 m asl) to the Eyrieux confluence (92 m asl) (length 120 km, mean slope 0.05%) has two main tributaries: the Sa^one and the Isere. The Sa^one, the only typical ‘lowland river’ among the Rh^one tributaries (mean slope 0.014%), flows from the north and has a typical oceanic pluvial regime with a high winter discharge and low discharge in summer.

TABLE 7.3 Flow regime (in m3/s) of the Rh^ one River and its main tributaries River

Station

Period

Data origin Altitude A

MQ

SpQ NQ

HQ

Q2

Q10

Rh^ one Rh^ one Rh^ one Rh^ one Rh^ one Rh^ one Rh^ one Rh^ one Rh^ one Ain Sa^ one Sa^ one Sa^ one Doubs Is ere Is ere Dr^ ome Durance Durance

Sion Porte-de-Scex Pougny Lagnieu Perrache Ternay Valence Viviers Beaucaire Chazey Sur Ain Monthureux-sur-Sa^ one Lech^ atelet M^ acon Neublans Moutiers Beaumont-Monteux Saillans L’Argentiere Meyrargues

1916–2003 1935–2003 1925–2005 1920–2005 1920–2005 1920–2006 1920–2005 1920–2005 1920–2005 1959–2006 1987–2006 1965–2006 1952–2006 1966–2006 1903–2006 1956–2002 1910–2006 1910–2006 1994–2006

1 1 2 2 2 2 2 2 2 3 3 3 3 3 3 2 3 4 4

112 183 336 457 598 1030 1410 1490 1700 123 3.25 158 403 175 27.6 337 18.1 27.6 26.1

33.4 35.1 32.6 29.9 29.5 20.4 21.2 21 17.6 33.8 14.2 13.6 15.7 24 30.5 28.6 15.8 28.1 2.2

910 1370 1440 2440 4250 4780 6700 7990 7800 1910 155 1650 2540 1760 236 2050 692 276 2800

461 629 990 1300 2100 3100 3000 4300 5900 920 77 830 1700 1100 160 1200 220 140 1000

639 808 867 1091 1300 1600 1900 2300 3000 3800 4500 5700 6000 8600 6100 7600 8300 10 000 1500 2000 140 110 1300 1700 2400 3000 1500 1800 310 440 1700 2200 380 520 210 260 2300 –

484 377 332 192 162 158 102 64 6 210 250 175 168 181 474 116 263 950 186

3349 5220 10 320 15 400 20 300 50 560 66 450 70 900 96 500 3630 228 11 660 25 690 7290 907 11 800 194 984 12 500

290 350 110 160 190 280 410 450 490 11 0.3 16 40 16 7.2 23 1.6 6.3 6.2

Q50

A: Catchment area upstream of gauging station. MQ: arithmetic mean annual discharge. SpQ: specific discharge (m3/s/km2). NQ: lowest measured discharge. HQ: highest measured discharge (instantaneous value). Q2: magnitude of a 2-year flood. Q10: magnitude of a 10-year flood. Q50: magnitude of a 50-year flood. Data origin: (1) Federal Office for Water and Geology (http://www.hydrodaten.admin.ch/), (2) Compagnie Nationale du Rh^ o ne, (3) Direction R e gionale de l’Environnement Rh^ o ne-Alpes, (4) Direction R e gionale de l’Environnement Provence-Alpes-C^ o te d’Azur (French data available at http://www.hydro.eaufrance. 3 fr/accueil.html) discharges are expressed in m /s.

256

FIGURE 7.3 Mean monthly discharge of the Rh^one River at seven gauging stations.

The Isere River has an alpine character with high spring and early summer discharge from snowmelt. This watershed is affected by water retention to meet peak energy demands during the cold season. The lower Rh^ one downstream from Valence has tributaries from the Cevennes Mountains that drain the eastern Massif Central (Eyrieux, Ardeche, Ceze and Gard) and from the Alps (Dr^ ome, Ouveze, Eygues and Durance). Watersheds of the southern tributaries have a Mediterranean climate with high discharge during fall and spring, the Durance River in particular. Most of the discharge in these southern tributaries comes as floods that occur mainly in September and October. The area specific discharge of the Rh^ one decreases along the Swiss Upper Rh^ one, is relatively uniform from Lake Leman to Lyon, decreases severely after the Sa^ one confluence, and is relatively stable to the delta (Figure 7.4). At the mouth, the Rh^ one shows a high seasonal and annual regularity in flow (see Figure 7.3). The oceanic and Mediterranean climate of the Rh^ one causes four main types of floods: (1) oceanic, (2) Mediterranean, (3) extensive Mediterranean, and (4) general floods. The first type of flood results from high oceanic rainfalls in Upper Rh^ one tributaries with relatively high probability of occurrence (40–60%).

FIGURE 7.4 Mean annual discharge (Q) and specific discharge (SpQ) along the Rh^ one River.

PART | I Rivers of Europe

The second type of floods are linked to Mediterranean rainfalls from the south–west (tributaries in the Cevennes area) or from Mediterranean tributaries. At times, Mediterranean rainfalls reach the Sa^one, Isere and Ain watersheds causing the third type of flood with low probability (10%). The fourth type of flood has intermediate probability (15–25%) and comes from oceanic and Mediterranean rainfall. Downstream from Valence, tributaries of the lower Rh^one often experience severe flash floods, the most destructive natural hazard in the western Mediterranean. Heavy rainfalls common in late summer and early fall are linked to the proximity of the Mediterranean Sea, and meteorological and relief attributes. The Cevennes-Vivarais region in the southern Massif Central is especially affected by extreme rainfalls that cause floods in the Ceze, Ardeche and Gard rivers (Delrieu et al. 2005). These rains, called ‘cevenoles’, can influence large regional areas as, for example, the flood in September 1890 in southern France on the Ardeche at 6500 m3/s at Vallon Pont d’Arc in the Ardeche gorges (Parde 1925). Mediterranean floods can extend far upstream as in November 1935, November 1951 and December 2003, and generate high discharges in the lower Rh^one as in October 1993 (9700 m3/s at Beaucaire, 25-year flood). General floods result from different combinations of high rains, such as those responsible for the floods at Beaucaire in October 1840 (13 000 m3/s), May 1856 (12 500 m3/s) and January 1994 (11 000 m3/s, 70-year flood). Hydropower plants on the Rh^one and high-head retention schemes in the catchment have greatly modified the flow regime of the river (Vivian 1989). On the Swiss Upper Rh^one, peak electricity demand increased winter flows by 20–150% and decreased summer flows by 15–30%. Flows now have a well-defined weekly cycle as well as sudden and frequent daily flow oscillations (Meile et al. 2006) that also influence water temperature (Meier et al. 2004) and suspended sediments (Loizeau and Dominik 2000). The level of Lake Leman and the Rh^one discharge at the outlet of the lake are regulated at Seujet dam in Geneva. Downstream of the Arve, discharge fluctuates according to the functioning (hydropeaking) of the Verbois, Chancy-Pougny and Genissiat dams. Discharge from Genissiat (gauging station at Surjoux) shows severe daily variations ranging from 0 to 700 m3/s, which are partly attenuated downstream by the Seyssel compensation dam. Upstream of Lake Leman, the annual mean temperature is 6.9 C at Sion (period 1974–2005, range 1.1 to 13.7 C) and 7.2 C at Porte-du-Scex (period 1971–2005, range 0.7– 14.1 C). The large volume and long residence time of Lake Leman warms surface waters to an annual mean temperature of 12.5 C at Geneva (period 2003–2005, range 2.8– 27.3 C). Sudden and short decreases in water temperature are recorded regularly at the outlet of Lake Leman, especially in summer with the renewal of water in the epilimnion in the ‘Petit Lac’ by seiches induced by strong winds (Guilbaud et al. 2004). Temperature decreases can reach 9 C and propagate downstream of Lyon.

257

Chapter | 7 The Rh^ one River Basin

Twelve measuring stations are distributed along the French Rh^ one from the French-Swiss border at Pougny to Aramon downstream of the Durance confluence. Three stations are on the Ain, Sa^ one and Isere. Long-term records show that the Rh^one temperature and air temperature are not balanced. Water temperature depends on five main factors: (1) the upstream-downstream transfer of temperature of water flowing from the epilimnion of Lake Leman, (2) meteorological conditions especially when significant gaps between air and water temperature occur, (3) main tributaries that modify the water temperature below the confluence, (4) nuclear power stations that typically increase temperatures downstream by 1–2 C, and (5) by-pass sections with low regulated discharge where water temperature increases faster than in artificial channels. From 1977 to 2005, the annual mean water temperature of the Rh^ one was 10.9 C at Pougny and 14.3 C at Aramon. Temperature increases on average 2.4 C in the Upper Rh^one between the Arve and Sa^ one and 1.2 C from the Isere to the Durance River. The mean daily range in temperature in the Rh^ one is 0.5 C. The Ain is a cold tributary in winter but a warm tributary in summer (annual mean 11.4 C, 1977– 2005). The Sa^ one is a warm tributary (annual mean 13.4 C, 1977–2005). The Isere is an alpine cold tributary (annual mean 10.5 C, 1977–2005) that decreases the annual mean temperature in the Rh^ one by 0.2–1 C during the warm season. Warmest temperatures occur in August and the lowest in January. From 1977 to 2005, water temperatures in the Rh^ one and tributaries have increased, ranging from 0.7 (Isere one River at Aramon) The French Upper River) to 1.8 C (Rh^ Rh^ one now experiences temperatures that were found in the lower Rh^ one in the past, although the temperature increase was higher in the lower Rh^ one. The temperature in Lake Leman (data CIPEL) has increased by 1 C at 5 m depth in the last 30 years, and temperatures below 100 m depth are now reaching 6 C. Climate change has increased temperatures during spring, summer and winter, shortening the cold season and lengthening the warm season. For instance, the temperature threshold of 18 C was reached 70 days earlier in 2003 than in 1978 at Bugey 40 km upstream of Lyon.

7.4.3. Biogeochemistry The geochemical characteristics of the Rh^ one were described by H.L. Golterman (1985a, 1985b, 1985c, 1985d). The Rh^ one has hard waters with increasing calcium concentration and a small decrease in pH from the source to the delta. It has high sulphate, chloride and phosphate concentrations (Table 7.4). The Rh^ one loses its glacial silt and some major changes occur in calcium-carbonate dynamics in Lake Leman. Lake Leman has a theoretical 11.4-year water residence time that has a clear buffering effect on major elements. The lake outlet contributes nonreactive ions such as sulphates or magnesium and shows

strong seasonal patterns in silica, bicarbonates and calcium. Downstream tributaries progressively modify these concentrations, depending on water origin and hydrological regimes. For instance, the Upper Rh^one hydrological regime is defined by alpine components that shift to a complex regime influenced by the pluvial-oceanic regime of the Sa^one. The Sa^one increases the inputs of calcium, sodium, bicarbonates, sulphates, chlorides and nitrates in the Rh^one (Table 7.4), despite the inflow of the Isere with more alpine characteristics. The Alpine mountain range in the eastern catchment drained by the Rh^one, Isere and Durance consists mainly of sedimentary rocks with some siliceous crystalline and metamorphic rocks in the inner Alps. The Jura and Vosges mountains in the north in the Sa^one watershed are mainly calcareous. Crystalline siliceous rocks dominate the southern Massif Central (Cevennes) in the south–west Rh^one basin (Gard, Ceze and Ardeche). The Rh^ one also is a large submontane alluvial river where upland/stream interactions are important, exemplified by: (1) a development of a lateral aquifer >15 m deep upstream of Lyon, (2) large floodplains with numerous side arms although reduced by regulation, and (3) coarse sediments with high permeability. This hydrogeological and geomorphological context contributes to the Rh^one nutrient budget, especially during low flows (Dahm et al. 1998). The natural chemical composition of each watershed (Meybeck 1986), mixed origin of waters, hydrological features in the basin, and major anthropogenic inputs explain the high local variability in water quality. For instance, the high chloride concentration in the Rh^one at Geneva is directly linked to the use of salt on roads during winter. Further, trace elements (As, Sb, Ni and Ba) in the Rh^one at Arles show increased concentrations during floods in the Gard and Ceze rivers that drain silicate mountains and old mine tailings (Ollivier et al. 2006).

7.4.4. Bedload The main tributaries that provide suspended and bedload sediments to the Rh^one are upstream of the Ardeche, except for the Durance. A total of 800 000–900 000 m3/year of sediments are poured into the Rh^one. The Arve, Ain, Isere and Durance provide 75% of this sediment load, and the sediment transport velocity is estimated at 2 km/year in the Rh^one. The mean long-term annual sediment load in the Rh^one at Arles from 1967–1996 was 7.4 Mt, although recent studies suggest that the annual mean value for the last 40 years could have been between 9 and 10.1 Mt (Antonelli & Provansal 2002; Pont et al. 2002). Annual values were highly variable, ranging from 1.2 Mt in a low flow year (Q = 1192 m3/s, 1973) to 19.7 Mt in a high flow year (Q = 2175 m3/s, 1994, 50 days of flooding). The highest estimated values during high flow years were 22 Mt (Surell 1847) and 30 Mt (Parde 1925). Present values are mainly due

258

TABLE 7.4 Average main chemical characteristics of the Rh^ one River from upstream to downstream and some of its major tributaries (1985–2004) River

Station

Altitude

W (km2)

(mS)

pH

Ca2+

Mg2+

Na+

K+

HCO

SO42

Cl

NO3

Rh^ one River

Porte-du-Scex Gen eve Chancy Pougny Murs-et-Geligneux St-Sorlin-en-Bugey Jons Chasse-sur-Rh^ one Saint-Vallier Charm es-sur-Rhone Donz ere Aramon Arles

377 369 347 342 218 193 180 150 120 103 58 16 4

5220 7987 10 294 10 300 13 960 15 400 20 300 51 080 54 650 66 450 70 900 88 600 96 500

288 287 308 302 318 325 337 400 415 428 422 418 426

8.05 7.98 8.06 8.10 8.07 8.09 8.09 8.03 7.98 7.98 7.99 8.03 7.93

41.1 42.8 47.4 47.3 51.3 52.7 58.3 66.3 68.9 71.8 69.8 69.3 69.6

5.8 6.1 6.5 6.0 5.8 5.8 5.2 4.9 5.0 6.3 6.1 5.9 6.3

6.6 4.9 5.7 5.4 5.4 5.3 5.1 11.0 12.1 11.9 11.4 11.2 11.4

1.5 1.4 1.6 1.6 1.5 1.5 1.4 2.0 2.0 1.8 1.8 1.9 1.9

87.5 119.3 113.8 131.8 137.3 158.8 175.1 174.1 167.9 166.4 163.8 166.4

53.2 46.0 45.6 45.8 40.3 36.7 32.0 33.3 38.9 53.9 49.7 48.2 48.3

8.9 6.6 7.9 7.6 7.9 8.1 7.5 18.7 20.2 20.7 18.5 18.1 18.9

2.64 1.72 2.77 2.29 2.80 3.16 3.92 6.11 6.88 6.41 6.60 6.45 6.57

St-Maurice-de-Gourdans Sauni eres Lyon Ch^ ateauneuf-sur-lsere Caumont-sur-Durance

191 175 167 128 39

3650 7500 29 900 11 800 14 400

394 432 510 469 502

8.13 8.12 7.98 7.96 8.14

74.0 75.2 77.5 79.4 83.2

2.8 3.3 4.6 9.7 12.8

2.8 7.5 29.4 11.7 15.1

1.0 1.9 3.7 1.1 2.0

227.0 216.2 203.3 152.2 204.7

4.0 19.2 29.2 100.7 86.4

6.4 16.4 41.0 18.5 24.1

4.17 7.47 9.70 3.83 3.25

Ain Doubs Sa^ one Is ere Durance

NH4+

PO43

BOD5

DOC

0.21 0.17 0.12 0.11 0.25 0.31 0.25 0.18 0.15 0.15

0.03 0.05 0.11 0.11 0.13 0.10 0.12 0.21 0.39 0.31 0.24 0.24 0.29

1.77 1.50 1.48 1.30 1.76 1.56 1.45 1.38 1.58 2.05

1.53 1.58 1.71 1.83 1.80 2.43 2.38 2.06 2.22 2.29 2.25

0.02 0.03 0.18 0.21 0.02

0.05 0.14 0.26 0.15 0.03

1.40 2.86 1.43 1.30 2.32

2.00 2.18 3.15 1.12 1.14

0.03

0.96

The Doubs River is a tributary of the Sa^ o ne River. Data from NADUF ‘ Nationale Daueruntersuchung der schweizerischen Fliessgew€asser’ (Porte-du-Scex, Chancy), from SECOE ‘ Service Cantonal de l’Ecologie de l’Eau & CIPEL ‘ Commission Internationale pour la Protection des Eaux du L e man (Gen e ve) and from Agence de l’Eau Rh^ o ne-M e diterran e e-Corse (other stations). Conductivity (mS/cm) at 25 C. Concentrations of cations and anions in mg/L. Biological Oxygen Demand (BOD5) in mg/L O2 and Dissolved Organic Carbon (DOC) in mg/L.

PART | I Rivers of Europe

259

Chapter | 7 The Rh^ one River Basin

to reduced sediment loads in the Ain, Isere and Durance, partly reflecting lower flows since the middle 19th century (Table 7.5). Sediment discharge of the Rh^ one has been altered because of anthropogenic activities. The upper river between Geneva and the Ain has seen a cessation in bedload transport due to gravel harvesting and retention in reservoirs. CNR canals still contribute some sediment to the river during floods. Bedload transport was estimated at 1 Mm3/year at the beginning of the 20th century but only 0.2 m3/year today. Around 12 Mm3 of fine sediments are stored in Genissiat reservoir. Presently, most suspended sediments now pass through the downstream reservoirs because of a new hydraulic geometry. Excluding fine sediments stored in Genissiat reservoir, the whole river has a sediment deficit of one has a surplus of about 3– 14 Mm3, the French Upper Rh^ one has a deficit of 17 Mm3 (Dou4 Mm3 and the lower Rh^ triaux 2006). The Ain River still provides a significant bedload that has been extracted upstream of Lyon, but the Sa^one provides little or no bedload due to intensive gravel harvesting and the construction of a staircase of navigable reaches by low dams. Downstream of Lyon, a chain of diversion dams reduces velocity and prevents any erosion of the riverbed, and tributaries are usually managed to prevent the input of bedload into reservoirs to decrease the risk of flooding. The Isere also has a chain of dams along its downstream course. The Dr^ ome and Durance rivers still deliver bedload, but gravel is retained upstream of the confluence with the Rh^ one and extracted. Bedload entering by-pass reaches from the Ardeche River is extracted, and the riverbed is incising downstream from the last dam at Vallabregues. Mountain reforestation and land abandonment have further reduced erosion in the uplands, but not in the same proportion as bedload.

7.4.5. Nutrients and Pollution Over the past 30 years, marked changes have occurred in the proportion of the population connected to wastewater treat-

ment as well as in wastewater treatment technology. In general, organic pollution has decreased in many European countries, as indicated in the improved water quality in the Sa^one, Doubs, Isere, Durance and Rh^one. For instance, concentrations of organic matter and ammonium have decreased dramatically compared to the 1970s at Saint-Vallier, a heavily polluted section in the Rh^one. The status of smaller rivers is more variable and can be critical when streams receive high pollution loads during low flow, especially wastewaters from wine producing enterprises, cheese factories, and tourist areas as in Alps in winter and Mediterranean region in summer. Concentrations of orthophosphate in the Rh^ one have been decreasing steadily over the past 20 years, following measures introduced by national and European legislation to reduce eutrophication (Glennie et al. 2002). The two main actions in the late 1980s and early 1990s were (1) a reduction in the amount of sodium tripolyphosphate (STPP) to ‘alternative’ non-phosphate based detergent builders such as Zeolite A, and (2) improving wastewater treatment through implementation of the Urban Wastewater Treatment Directive (UWWTD). In Switzerland, a general decrease in phosphate resulted from the implementation of phosphate removal in wastewater treatment plants and from a phosphate-ban initiated in 1986 (Jakob et al. 2002). Although efforts were made in France to reduce polyphosphate compounds in detergents to <0.2 mg/L by 1996, a phosphate-ban decree has not been adopted. In the lower Rh^one, elimination in 1992 of a large industrial effluent upstream of Saint-Vallier significantly lowered orthophosphate concentrations in the river (Poussard and Madrid 1999). Pollution by nitrate is highly variable in the Rh^ one catchment. Waters flowing from eastern mountains are of good to high quality while western tributaries show moderate to bad quality. Nitrate is a non-point source pollution from agriculture. Among large rivers, only the Sa^one and its tributaries are particularly affected, especially in Burgundy, and contribute >60% of the nitrate inputs to the Rh^one. Nitrate values are low in the Upper Rh^one and increase progressively to a maximum at Jons

TABLE 7.5 Evolution of bedloads inputs of major tributaries of the Rh^ one River Watershed area (km2)

Natural regime Bedload (m3/year)

Ain Sa^ one Is ere Dr^ ome Ard eche Durance

3713 29 498 11 865 1642 2430 14 322

100 000 0 100 000 40 000 15 000–40 000 300 000

Total

63 470

817–910 000

Present regime Suspended matter (Mt/year) 0.15–0.3 1.5–3 4.5 0.2 0.1–0.2 6 14.8–19.2

Bedload (m3/year)

Suspended matter (Mt/year)

60 000 0 0 30 000 10 000 0

0.1 1.5–3 3.5 0.2 0.1–0.2 1.8

170–180 000

9.5–14

E´tude globale pour une r e duction des crues dues au Rh^ o ne – Hydratec, Sogreah, Minea. E´tude du transport solide, synth e se de premi e re etape, 2001.

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due to inputs from intensive agriculture in the lower plain of the Ain River. There was a small decrease in nitrate concentrations during the 1990s. From 1994 to 1995, nutrient inputs by the Rh^ one into the Gulf of Lions were measured at Arles (Moutin et al. 1998). The authors estimated the total input of nitrogen at 115–127 kt/year and mainly as nitrate (92.3–96.1 kt/year), which significantly influences the nutrient balance and primary production of the western Mediterranean Sea.

7.4.6. Heavy Metals and Organic Micropollutants The most serious metals polluting the Rh^ one are mercury and arsenic, and to a lesser extent nickel and zinc. Small factories, sometimes concentrated in restricted geographical areas, are mainly responsible for metal pollution. Metal pollution problems exist for the Arve, some valleys in Alps, the Azergues (right bank tributary of the Sa^ one) and the Guier River. In the Rh^ one, high poly-metal contamination occurs between Lyon and the confluence of Isere River along the ‘chemical corridor’ (Chasse to SaintVallier in the lower Rh^ one). Mono-metal inputs occur at Pougny and downstream of the Ain River industrial plain (Santiago et al. 1994). Farm inputs clearly dominate most of the studied metals (animal farm breeding effluents – zinc – and soil amendments by chemical fertilizers). Copper is used as fungicide in arboriculture and viticulture, especially the lower Rh^ one River, Provence, Beaujolais and Burgundy.

7.4.7. Pesticides An environmental inventory of the Rh^ one (DIREN 2005) showed that pesticides are a real problem that may constrain the ambitious aims of the Water Framework Directive. Presently, the analytical assessment concerns >300 active substances. In 2003, 60 surface water sites were sampled each month and 96 groundwater sites were sampled each season. In groundwaters, 40 pesticides were identified. There were 116 pesticides found in surface waters composed of herbicides (47%), insecticides (27%) and fungicides (22%). Over two-thirds of surface water sites had 10 or more pesticides detected, and highly contaminated sites were distributed throughout the basin. For groundwater sites, contamination occurred mainly in agricultural areas such as the Burgundy foothills, the Sa^ one River valley, the Upper Sa^ one limestone plateau, and the Rhodanian corridor. In surface waters, glyphosate (N-phosphonomethyl glycine) and its metabolite aminomethylphosphonic acid (AMPA), amitrole (3-amino1,2,4-triazole) and diuron were in >90% of the sites. In groundwaters, the most frequent products were atrazine, terbuthylazine, their metabolites and simazine (>30% sites), then diuron (15%) and the fungicide oxadixyl

PART | I Rivers of Europe

(10%). Total concentrations of active substances >5 mg/L (the drinking water limit) were observed in the Ardieres, Meuzin, Azergues, Seille, Ceze and Isere Rivers, all downstream of vinyards and intensive agriculture areas. The Isere is affected by a pesticide factory on the Drac River. Seasonally, inputs show a progressive increase during spring, a decrease in summer, and a peak again in October from herbicides used for winter cereals. The last published survey indicated a general contamination of rivers in the Rh^one watershed by pesticides (Agence de l’Eau RM&C 2004).

7.4.8. Priority Substances of the Water Framework Directive About 90% of 200 high-hazard substances were found in river effluents, including mercury, nonylphenols, trichloromethane, DEHP [di(2-ethylhexyl)phthalate]. Others dangerous organic priority substances are found in effluents from the chemical industry, especially in the metropolitan areas of Lyon and Grenoble, and the heavily industrialized area along the lower Rh^one. Urban effluents also contribute; 90% of effluents from wastewater plants had at least one priority substance detected. Nonylphenols were found in >60% of the samples, and DEHP and pentachlorophenols in >30%. Polycyclic aromatic hydrocarbons (PAHs) are one of the most widespread organic pollutants in the Rh^one catchment. Other micro pollutants (excluding PAHs, Polychlorinated biphenyls (PCBs) and pesticides) originate from two industrial sites on the Drac River near Grenoble and the Durance River near Sisteron.

7.4.9. Artificial Radionuclides In France, electricity is mainly produced by nuclear means: 427 Twh, 78% of the electricity produced in 2004 (CEA 2005). There are 15 nuclear power units and one spent fuel reprocessing plant on the river, and the Rh^one valley has the highest concentration of nuclear plants in Europe. A 40-year survey of industrial radionuclide release in the Rh^one (Lambrechts & Foulquier 1987; Foulquier et al. 1991; Eyrolle et al. 2005) has been acquired by IRSN ‘Institut de Radioprotection et de Surete Nucleaire’ (see www.irsn.org). Radioactive isotopes originate from the atmospheric fallout from weapon tests between 1945 and 1980. Radionuclide contamination of the atmosphere is still detectable today. The plume of the Chernobyl meltdown on 24 April 1986 passed over eastern France in April and rainfalls in May deposited 1250– 40 000 Bq/m2 of additional 137Cs to the Rh^one catchment. After 20 years, the 137Cs terrestrial inputs are similar to the 137 Cs released by Marcoule reprocessing plant (Eyrolle et al. 2005). The Marcoule plant has been reprocessing spent military and industrial fuel since 1961. A change in the treatment process in 1990 and the start of a dismantlement plan in 1997 significantly decreased radioactive wastes from the

Chapter | 7 The Rh^ one River Basin

plant. Today, 238Pu industrial inputs are still 10 higher than those from global fallout, while 239+240Pu released by Marcoule equal the annual catchment contribution (Eyrolle et al. 2004). Recent research showed that floods caused contamination pulses generated by the reworking of antecedent contaminated sediments (Eyrolle et al. 2006). Liquid effluents from nuclear installations are responsible for the low-level presence of 60Co, 58Co, 110mAg, 54Mn, 137Cs and 134 Cs radionuclides. The 137Cs/134Cs activity ratio is a useful tool to describe the fate of radioactive sources reaching the Rh^ one. Today, 137Cs terrestrial inputs are estimated at 100 GBq/year, more than before the Chernobyl accident and higher than recent industrial inputs (Eyrolle et al. 2005).

7.5. AQUATIC AND RIPARIAN BIODIVERSITY 7.5.1. Algae Information about algal composition of phytoplankton or periphyton in the Rh^ one is scarce. The only available detailed data are those from a monitoring survey of the SaintAlban/Saint-Maurice-l’Exil nuclear power plant 45 km downstream of Lyon with 395 species identified (320 phytoplankton species, 361 periphyton species). Species of the genus Diatoma and Chlorophyta are the most numerous (41% and 39% of the phytoplankton species, 86% and 10% of the periphyton species, respectively). Cyanobacteria represent 9.7% of the phytoplankton species and 3.6% of the periphytion species. Other periphyton species belong to the Chrysophycea and Dinophycea (one species each). The mean species richness between 1985 and 2001 was 104 species and ranged from 71 to 160 species. The number of species has decreased continuously since 1992 (ARALEP 2003). In the by-pass section of the Pierre-Benite water scheme, the most abundant taxon was Cladophora, and other taxa were rare (Spirogyra, Enteropmorpha intestinalis and Cyanobacteria). In the by-pass sections of the Chautagne and Belley water schemes (data from 1994 to 1996), Cyanobacteria (Oscillatoria limosa) were most abundant at the end of winter (Barbe & Barthelemy 1994; Barbe 1997). Later, substrates were colonised by Hydrurus foetidus and the filamentous diatoma Melosira varians, and green algae (Spirogyra sp. and Cladophora sp.) in summer. In the same area, rocky weirs were colonised by bryophytes typical of eutrophic conditions: Fontinalis antipyretica, Amblystegium riparium, Pellia epiphylla, Cinclidotus aquaticus, Cinclidotus fontinaloides, Rhynchostegium riparioides, Brachythecium rivulare.

7.5.2. Macrophytes Aquatic plant diversity in the Rh^ one and tributaries results mostly from the high number of abandoned channels. These

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channels are shaped by river dynamics, and are consequently highly diverse in terms of sinuosity, hydraulic capacity, and distance from the river. This geomorphological complexity combined with hydrology dictates (1) the frequency and duration of floods, (2) the net effect of floods (erosion versus deposition), and (3) the discharge of groundwater exfiltrating in these channels (Bornette et al. 1998). The Upper Rh^ one and several of its tributaries (e.g. Ain, Doubs, Ardeche, Isere, Dr^ome) are piedmont rivers, characterized by a coarse bedload, and a relatively high slope. In such situations, flood duration is low (usually a few days), and floods cause increases in flow velocity that damage plant communities and erode fine sediment, particularly cut-off channels with low sinuosity and hydraulic capacity. In more sinuous channels, floods have no or a silting effect, depending on the frequency of connections between the river and the channels. Groundwater discharge is usually low in sinuous channels that are frequently clogged with fine sediment. Groundwater discharge can be quite high in others, depending on the channel slope and substrate grain-size. This groundwater comes either from nutrient-rich river seepage or from more nutrient-poor hillslope aquifers. Oligotrophic cut-off channels are abundant along the Ain and in some places along the Rh^one. In most situations, the high human activity in the catchment leads to fairly high (e.g. Upper Rh^one, Isere) or very high nutrient-content of the water (Sa^one, Doubs, lower Rh^one). Highest species richness is observed in cut-off channels with intermediate nutrient levels and the lowest species richness occurs in nutrient-rich cut-off channels. Oligotrophic communities have low richness but a high proportion of rare species. Among the most abundant species that occur in cut-off channels of the Rh^one river and its tributaries are eutrophic species (Lemna minor, Ceratophyllum demersum, Spirodela polyrhiza, Myriophyllum spicatum) and species intolerant to flood scouring (Phragmites australis, Nuphar lutea, Nymphea alba) (Bornette et al. 2001). Some relatively rare species mainly occur along the Sa^one (Stratiotes aloides, Hydrocharis morsus-ranae, Nymphoides peltata). A few species including Callitriche platycarpa, Elodea canadensis, Berula erecta, and Phalaris arundinacea occur in flood-disturbed cut-off channels (e.g. the Ain and French upper-Rh^one). Many species related to intermediate and low trophic levels occur along the Ain River (Potamogeton coloratus, Chara major, Luronium natans, Baldellia ranunculoides, Hydrocotyle vulgaris, Cladium mariscus, Schoenoplectus nigricans). In an exhaustive study of aquatic vegetation in all cut-off channels of the Rh^one from Lake Leman to the sea, Henry and Amoros (unpublished data, 1998) showed that species richness is high (67 strictly aquatic species and 46 helophyte species) but not uniformly distributed. Cut-off channels along the French Upper Rh^one have a relatively low proportion of eutrophic species due to oligotrophic groundwater from karstic origins and inputs from the Ain. From Lyon to the confluence with the Isere, aquatic species that colonize cut-off channels are mainly eutrophic. Downstream from the

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Isere confluence, the proportion of eutrophic species decreases slightly, and some channels have oligotrophic species. Species richness increases significantly below the confluence with the Drome River with a high proportion of oligotrophic species in cut-off channels. Further downstream, cut-off channels of the Rh^ one again become highly eutrophic. Some mesotrophic species occur exclusively in cut-off channels upstream from Lyon, such as Hippuris vulgaris, Hottonia palustris, C. platycarpa, and Potamogeton natans. Some species occur both in the upper river and downstream of the Isere confluence (e.g. Groenlandia densa, Sparganium emersum) or the Dr^ ome River (e.g. P. coloratus, Sagittaria sagittifolia, Juncus articulatus). Finally, some species are found only in the eutrophic lower river, (Spirodela polyrhiza, Vallisneria spiralis, Lemna gibba). The main non-native aquatic plant species are Egeria densa, E. canadensis, E. nuttallii, Lagarosiphon major, Ludwigia peploides and L. grandiflora, Myriophyllum aquaticum.

7.5.3. Floodplain Forests Alluvial forests have decreased by 50–80% during the past 50 years, being replaced by agriculture and other human activities. During the 18th century, forests were limited to the riverbanks (riparian forest) and islands. Upper terraces were used for agriculture and lower terraces as grassland. The ecological features of alluvial forests depend on geomorphology (braided, meandering, anastomosing). During the 18th century, allogenic successions occurred in braided sections with a strong rejuvenation process of fluvial landforms. Coarse sediments (sand, gravels and pebbles) were displaced by floods and constituted unstable bars. Plant succession was usually reset at a softwood stage (Salix daphnoides, Salix purpurea, Salix eleagnos, Salix viminalis, Salix alba, Alnus incana), with the more mature species being poplars (Populus nigra). From the middle of the 19th century, anthropogenic pressure began to increase along the river corridor, and hard wood species such as Fraxinus excelsior progressively colonized river margins (Marigo et al. 2000). More recently, hydroelectric development of the Rh^one valley has led to severe changes in by-pass sections, causing a reduction in wetted areas and lowering of the water table by up to 1 m in some areas. The main effects of the hydrological change were: (1) a regression in softwoods (S. daphnoides, S. purpurea, S. eleagnos, S. alba, S. viminalis, P. nigra and A. incana), (2) a progression of hardwoods (F. excelsior, Acer pseudoplatanus, A. platanoides, Tilia cordata, Coryllus avellana, Carpinus betulus, Quercus pubescens, Buxus sempervirens, F. sylvatica), (3) a progression of monopolistic species in open gaps (Impatiens glandulifolia, Solidago gigantea, Palaris arundinacea, Urtica dioica, Rubus fruticosus, Crataegus monogyna, Prunus spinosa, Berberis vulgaris, Humulus lupulus, Clematis vitalba, Parathenocissus

PART | I Rivers of Europe

quinquefolia), (4) an arrival of new species usually associated with Q. pubescens (sometimes Q. petraea) and C. betulus (Vinca minor, Mercurialis perennis, Phyteuma spicatum, Melica uniflora, Euphorbia sylvatica, Lamium galeobdolon), (5) the development of new types of plant communities as open poplar woods made up of P. nigra, Robinia pseudacacia (non-native species) and Q. pubescens (Klingeman et al. 1998). The creation of new areas by engineering works has favoured the establishment of non-native species such as Reynoutria sachalinense, Buddleia variabilis, Buddleia davidii, Ambrosia artemiaefolia, Acer negudo, Amorpha fruticosa (in tributaries), Aster novi-belgii and Galega officinalis (downstream from Lyon), Impatiens roylei (upstream from Lyon on sandy beaches), Solidago canadensis and Phytolacca americana. Senecio inaequidens has been found recently in the Drac and Isere valleys. River embankment and impoundment have reduced or eliminated ‘alpin’ pioneer species as Myricaria germanica and Typha minima, a protected species in the Swiss upper Rh^one. Similarly, A. incana and some willow species (S. daphnoides and S. triandra) have become rare. Along reservoirs, the increase in water table and decrease in current velocity have led to the replacement of species requiring well-oxygenated water such as A. incana by more tolerant species such as Salix cinerea and Alnus glutinosa. Longitudinally, the following species are representative: (1) limited populations of T. minima, Epilobium fleischeri and E. rosmarinifolium are still present in the Swiss Upper Rh^one, (2) Calamagrostis epigeios (sand, gravels, proximity of water table), T. minima (fine sand, proximity of water table), Salix eleagnos, Salix purpurea, M. germanica, Hippophae rhamnoides (gravels, proximity of water table, only upstream from Seyssel), Phalaris arundicea, Equisetum hiemale, Aegopodium podagraria, Salix triandra, S. daphnoides (sand, proximity of water table), P. nigra (gravels, coarse sand, deep water table), A. incana (fine sand, mid-depth water table), F. excelsior, Ulmus montana (fine sand and silt, deep water table), Ulmus minor and Prunus avium are distributed in braided sections upstream of Lyon, (3) in some meandering sections upstream of Lyon, a decrease in agriculture in the early 20th century allowed the development of oak forests of Quercus robur; this forest was destroyed in the 1980s for the Sault-Brenaz dam, (4) between Lyon and Montelimar and in the Sa^one floodplain, Populus alba and Fraxinus angustifolia replace P. nigra and F. excelsior, typical alpine species are absent; in the former braided section (i.e. ‘La Platiere’, nature reserve 50 km downstream of Lyon) P. alba and P. nigra co-occurred as well as F. excelsior and F. angustifolia with three maples (Acer platanoides, A. opalus, A. pseudoplatanus); in former meandering reaches (presently cut-off channels) where siltation was important and water oxygenation lower, Salix alba, S. cinerea and A. glutinosa are dominant, and (5) in the Mediterranean part downstream of Montelimar, large leaf trees progressively disappear: Tilia platyphyllos, A. glutinosa, F. angustifolia

Chapter | 7 The Rh^ one River Basin

and Q. pubescens replace Q. robur; Tamarix gallica and Glaucium flavum occur downstream of Arles. Long-term changes in floodplain vegetation have been documented on major tributaries, especially the Ain (Marston et al. 1995) and Isere rivers (Pautou and Girel 1994; Girel et al. 2003). The main non-native plant species include Acer negundo, Ailanthus altissima, Ambrosia artemisiifolia, Amorpha fruticosa, Aster lanceolatus, A. novi-belgii, A. squamatus, A. x-salignus, Bidens frondosa, Buddleja davidii, Helianthus tuberosus, H. x-laetiflorus, Heracleum mantegazzianum, Impatiens glandulifera, Parthenocissus inserta, Reynoutria japonica, R. sachalinensis, R. x-bohemica, Robinia pseudo-acacia, Senecio inaequidens, Solidago canadensis and S. gigantea. In wetlands of the Mediterranean zone, 6 non-native species occur: Acacia dealbata, Baccharis halimifolia, Cortaderia selloana, Paspalum dilatatum, Paspalum distichum and Phyla filiformis.

7.5.4. Aquatic Invertebrates Macrozoobenthic communities have been studied from the glacier’s outlet to the Rh^ one delta. Longitudinal, lateral and vertical patterns of aquatic invertebrate distribution have been examined as well as impacts of human activities on community structure. Regardless, some compartments of the river course have not been investigated as of this writing. In the most upstream section of the Swiss Rh^ one, the river flows in an active floodplain (‘Gletschbode’) and is highly influenced by the glacier (low water temperature - rarely above 4 C - and mean conductivity values about 10 mS/cm, low substrate stability and high concentrations in suspended sediments) and receives its first tributary, the Mutt River. The Rh^ one upstream of the Mutt harbours a zoobenthic community with low taxonomic richness (Knispel 2004). Among the 28 taxa present in the Rh^ one below the Mutt confluence and in the Mutt itself, Ecdyonurus picteti (Ephemeroptera), Capnia spp. (Plecoptera), Dixidae and Thaumalidae (Diptera) were absent in the Rh^ one upstream of the confluence, and 12 taxa were more abundant in the Mutt and downstream of the confluence the Rh^ one. The presence of different habitats in the floodplain (braided system after the confluence) enhances the species diversity, allowing the presence of Plecoptera (Perlodidae Perlodes intricatus, Nemouridae Protonemoura, Leuctridae), Trichoptera (Limnephilidae) and Ephemeroptera (Heptageniidae, e.g. Ecdyonurus picteti, Epeorus alpicola, Rhithrogena loyolaea). In the same upstream section, Ilg and Castella (2006) analysed the longitudinal distribution of 5 groups of macroinvertebrates defined by 6 biological traits and demonstrated a strong upstream-downstream gradient (from 1830 m to 1755 m asl). The upstream part (glacier snout) was dominated by small deposit feeders or scrapers, feeding on detritus or periphyton (Chironomidae, Diamesinae and Baetidae, e.g. Baetis alpinus). Small size, semivoltinism, absence of resistance forms and ability to live in the sediment interstices were important traits and considered adaptations to the harsh

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conditions of glacial streams. These groups also occurred downstream together with other taxa more heterogeneous in size, mainly crawlers, shredders that feed on various food sources (Nemouridae and Limnephilidae). A synthesis of data collected between 1991 and 1997 at 142 stations in 20 rivers including the Upper Rh^ one and major tributaries highlighted the taxa distributed according to local habitat characteristics (substrate and vegetation), physico-chemical parameters, and hydrological regime, especially hydropeaking (Baumann 2004). Hydropeaking associated with the channelization of the river has led to an impoverishment of the macrozoobenthic community and a dominance of Ancylidae (Mollusca), Gammaridae (Crustacea), Limnephilidae (Trichoptera) and Capniidae (Plecoptera). For instance, Allogamus auricolis (Limnephilidae) seems quite resistant to hydropeaking. Some Plecoptera are almost extinct (Doledec 2000; Baumann 2004): Brachyptera trifasciata (Taeniopterygidae), Nemurella pictetii (Nemouridae), Isoperla obscura (Perlodidae) and Dinocras cephalotes (Perlidae). Perla grandis (Perlidae) is considered rare. Siphonoperla montana, Chloroperla suzemicheli (Chloroperlidae), Perlodes intricate, Dictyogenus alpinum, D. fontium and Isoperla rivulum (Perlodidae) which were common alpine species in the 1980s are currently very rare. Substrate clogging by fine particles associated with algae allowed the development of Oligochaeta (especially Naididae) and Tipulidae (Diptera) associated with other pollutionresistant taxa such as Baetidae, Simuliidae, Psychodidae and Chironomidae. Bournaud et al. (1996) studied the longitudinal patterns of macroinvertebrate communities from the French-Swiss border to the sea. They identified 53 families (excepted Oligochaeta not identified to the family level) that represented 85% of the entire sampled fauna. Downstream from Lake Leman, the longitudinal succession of reservoirs, by-pass sections and short free-flowing sections associated with the original geomorphological features of the Rh^one floodplain offer a large diversity of habitats for macroinvertebrates. Downstream from Lake Leman to Verbois dam, three remarkable sectors were identified during a 10-year survey of macrozoobenthic communities (Dethier and Castella 2002). From Lake Leman to the Arve the water is very clear, the river bottom is made of pebbles and cobbles, and the current velocity is about 1 m/s. In this section, species diversity is relatively high and the dominant taxa are Dugesia polychroa-lugubris, Dugesia tigrina, Piscicola geometra, Dreissena polymorpha, Hydroptila sparsa, Hydroptila teneoides, Agraylea multipunctata, Leptoceridae and Lepidostomatidae. Other taxa, especially filtering collectors such as Hydropsyche spp., Neureclepsis bimaculata, were also present. Downstream of the Arve, turbidity increases strongly, especially during spring and summer, and current velocity is reduced because the river enters the Verbois reservoir. This confluence represents a major discontinuity in macrobenthic community with a decrease or loss of rheophilic and lithophilic taxa (Nemoura sp.,

264

Amphinemoura sp., Leuctra sp., Habrophlebia sp., Hydropsyche sp., Simuliidae). These taxa appear again downstream from Verbois dam (Perla sp., Leuctra sp., Brachyptera sp., Heptagenia sp., Rhithrogena sp., Ecdyonurus sp., Rhyacophila sp., Baetis sp., Serratella ignita, Elmis sp. and Riolus sp.). Among the 61 taxa recorded in the section between the lake and the Swiss-French border, several headwater species still occurred (i.e. Baetis alpinus, Odontocerum albicorne, Notidobia ciliaris, Hydropsyche dinarica and H. instabilis). Downstream, substantial data were collected from the late 1970s after the first dams were built before 1950. Hydroelectric development during the 1980s in the French upper Rh^ one section (downstream from Seyssel) caused important changes in macroinvertebrate communities. The creation of artificial waterbodies such as reservoirs, headraces and tailraces, and the drastic reduction in discharge and alteration of the flow regime in by-pass sections, led to the colonization by different communities. Rheophilic taxa such as Hydropsychidae, Heptageniidae, Simuliidae and Elmidae (Elmis maugetii) were considered common in the French upper Rh^ one prior to recent hydroelectric development. Most of the Trichoptera (18 taxa/24), Ephemeroptera (6 taxa/8) and Gammarus pulex were mainly or exclusively encountered in this section. Hydropsyche incognita was found exclusively at the border (Pougny), while H. contubernalis was dominant. Between Bregnier-Cordon and Lyon, the community had more potamophilic species such as Heptagenia sulphurea, Polycentropus irroratus, Lype reducta and more thermophilic Trichoptera (Cheumatopsyche lepida and Hydropsyche exocellata). Within the dammed section, macrophytes favoured taxa such as Hydra sp., Chaetogaster sp., Potamopyrgus antipodarum, Physa acuta and Hydroptila sp. Planarians and other molluscs became very abundant. Three rheophilic and lithophilic species disappeared in reservoirs, Theodoxus fluviatilis, Dendrocelum lacteum and Dugesia gonocephala (Dessaix et al. 1995). In by-pass sections, species typical of the Rh^ one before impoundment such as Heptagenia sulphurea, Rhithrogena sp., Ecdyonurus sp., Baetis lutheri, Protonemura spp., Isoperla spp., Perlodes intricata, Leuctra (gr. fusca) and Simuliidae were still present but became rare (Dessaix et al. 1995; Cellot 1996). Moreover, seven species of Hydropsychidae were found (H. angustipennis, H. contubernalis, H. exocellata, H. ornatula, H. modesta, H. incognita, H. siltalai). Bournaud et al. (1982) described the longitudinal distribution pattern of these species: H. siltalai and H. incognita inhabited the upstream part of the French Upper Rh^one; H. exocellata and H. contubernalis were common along the French Upper Rh^ one and, H. modesta was distributed all along the river corridor. The hydraulic habitats are also favourable for potamic species such as Potamanthus luteus and Polycentropus flavomaculatus, and limnophilic taxa such as Cloeon dipterum, Haliplus sp. and Platycnemis sp. A typology of side-arms, based on the distribution of macroinvertebrate species in the Rh^ one River upstream of Lyon

PART | I Rivers of Europe

and in the Ain River was established by Castella (1987) and Castella et al. (1991). A total of 43 Mollusca species, 9 Crustacea species, 29 Ephemeroptera species, 23 Odonata species, 112 Coleoptera species and 69 Trichoptera species were recorded. The lateral gradient in invertebrate communities was similar to the well-known longitudinal gradients (Illies & Botosaneanu 1963; Giudicelli et al. 1980). Downstream of Lyon, intense river regulation associated with strong chemical pollution and general habitat alteration led to a shift towards more lentic fauna. A total of 40 taxa was found both in the French upper and lower Rh^one, including Oligochaeta, Chironomidae and the mollusc Ancylus fluviatilis. Twenty seven taxa found in the French Upper Rh^ one were not recorded in the lower Rh^one, and 18 taxa were exclusive to this part of the river (Berrahou 1993). Most taxa were particulate detritus feeders (Mollusca, Asellidae and especially Proasellus meridianus) and taxa resistant to pollution (Achaeta). Some taxa, such as Oligochaeta, Chironomidae, Gammarus fossarum, Asellus aquaticus (Crustacea), several species of Mollusca (Bythinia tentaculata, P. antipodarum, Valvata piscinalis) were sampled all along the river but were more abundant in the lower Rh^one. Ecnomus tenellus, a lentic trichopteran, was highly abundant in the lower Rh^one because of the reduction of hydraulic constraints after river regulation. However, macroinvertebrate communities in by-pass sections of the lower Rh^one were quite different from those of the main channel, depending on the availability of habitats and hydraulic conditions (Fruget 1991; Fruget & Dessaix 2002). For example, in by-pass sections of Pierre-Benite and Peage-deRoussillon, epipotamic species such as Ancylus fluviatilis, Baetis fuscatus, Heptagenia sulphurea, and Hydropsyche spp. were found in some relict riffle areas (Fruget & Dessaix 2002). Tributaries also may contribute to local increases of biological diversity (Berrahou 1993). Downstream from the last dam (Vallabregues), water quality and progressive changes of mesological conditions (salinity, granulometry, current velocity and water temperature) were responsible for the decrease in taxonomic richness and presence of brackish and pollution-tolerant species. In a study of the invertebrate fauna of the delta, Fruget et al. (1995) identified 60 taxa, mainly distributed according to their preferences in salinity (Echinogammarus sp., Theodoxus fluviatilis) and current velocity (e.g. E. tenellus, Hydropsyche modesta, Dugesia sp.). During the last decade, potamic and lentic species (Asellus aquaticus (Crustacea), Caenis luctuosa (Ephemeroptera), E. tenellus, Cyrnus trimaculatus, Ceraclea dissimilis (Trichoptera)) have been favoured by the increase in water temperature associated with low water levels and low flow velocities in most by-pass sections. However, rheophilic species similar to those found upstream of Lyon such as H. exocellata and Oulimnius tuberculatus (Coleoptera) are still present in the Donzere-Mondragon by-pass section (Pont-Saint-Esprit) located 195 km downstream of Lyon. Local hydraulic conditions and the nearness of tributaries such as the Ardeche and Eyrieux Rivers which enrich the Rh^one with their drifting fauna can explain the presence of such taxa and other species

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Chapter | 7 The Rh^ one River Basin

such as Serratella ignita and Procloeon bifidum (Ephemeroptera) (Berrahou 1993). Long-term surveys allowed the study of the temporal variability in zoobenthic communities. Temporal trends combine the effects of dam building, the effects of climate change, of invasive species spread and of more recent rehabilitation measures. Daufresne et al. (2003) analysed the temporal change of macroinvertebrates between 1980 and 1999 around the nuclear power plant of Bugey just upstream the confluence with the Ain River. A gradual decrease or disappearance of cryophilic and rheophilic taxa was observed (Chloroperla spp., Nemura spp., Protonemura spp., Amphinemura spp., Brachyptera spp. (Plecoptera), Rhyacophila spp., Athripsodes spp. (Trichoptera), Ecdyonurus spp., Caenis spp. (Ephemeroptera), Stratiomyidae (Diptera)) with a concomitant increase in lentic and thermophilic taxa (Corixa sp. (Heteroptera), P. antipodarum, Theodoxus sp., Corbicula fluminea (Mollusca), Coenagrion sp., Platycnemis sp. (Odonata), Oecetis sp., Lepidostoma sp. (Trichoptera), Athricops sp. (Diptera)). The authors concluded that the increase in water temperature under climatic warming together with the development of hydroelectric schemes could explain the observed changes in invertebrate composition. Fruget and Bady (2006) analysed the temporal changes at the family level both in the French upper and lower Rh^one. Their analysis was based on long-term surveys of the fauna near 4 nuclear power plants (Bugey 50 km upstream of Lyon and Saint-Alban, Cruas-Meysse and Tricatin at a distance of 50 km, 150 and 185 km downstream of Lyon, respectively). From a total of 106 macroinvertebrates families, the authors found a decrease in family number from upstream to downstream that was linked to the alteration of physical habitat. They pointed out a gradual modification in community composition between 1985 and 2004, a significant improvement in water quality, a general increase in water temperature and slight changes in hydrological regime were the most important factors explaining the observed changes. More recently, unusual summer temperatures observed since 2003 and two large floods in 2001 and 2002 caused an increase in thermophilic species (e.g. E. tenellus) and exotic species (Dikerogammarus villosus, Atyaephyra desmarestii, Hypania invalida, Hemimysis anomala) in the lower Rh^ one. The recent increase of minimum flows in the by-pass section of Pierre-Benite increased the proportion of rheophilic taxa.

7.5.5. Non-native Species About 30 invertebrate taxa were introduced in the Rh^one River. Besides navigation, which allowed migrations and invasions, major changes in the river environment favoured colonization by potamo-lentic species and expansion of others (Fruget et al. 2001; Daufresne et al. 2007). The Sa^ one River, connected by the Freycinet canal network to rivers in northern Europe such as the Rhine, is a primary source of invasive taxa, in particular during floods. The main species include Cnidaria: Craspedacusta sowerbyi (around 1900), Cordylophora caspia (down-

stream of Lyon), Bryozoa: Pectinatella magnifica, and very recently (2005) Urnatella gracilis (downstream of Lyon), Turbellaria: Dugesia tigrina (beginning of the 20th century), Polycheta: Hypania invalida (downstream of Lyon since 2002, the only one freshwater Polycheta), Oligocheta: Branchiura sowerbyi (around 1950), Mollusca Gastropoda: Menetus dilatatus, Physella heterostropha/acuta (beginning of the 20th century), P. antipodarum, Gyraulus parvus, Lythoglyphus naticoides (downstream of Lyon, around 2000, thermophilous species) and Mollusca Bivalvia: D. polymorpha (1850), Corbicula fluminea (in 1985 in the Sa^one, after 1993 in the Rh^ one). Invasive species comprise a number of Crustacea. Gammarus roeseli, Gammarus tigrinus, Dikerogammarus villosus, Crangonyx pseudogracilis, Orchestia cavimana and A. desmarestii were found downstream of Lyon in the 1990s. Chelicorophium curvispinum and Hemimysis anomala appeared after 2000 also downstream of Lyon, Orconectes limosus was found around 1960, whereas Procambarus clarkii (downstream of Lyon) and Pacifastacus leniusculus (between Geneva and Lyon) appeared more recently. Dikerogammarus villosus was first observed in France in the Sa^one River in 1997, and then in 1998 in the Rh^one downstream of Lyon, in Lake Leman in 2002, and in the French Upper Rh^one in spring 2006.

7.5.6. Protected Species Few macroinvertebrates are protected, but Castella et al. (2005) mentioned the presence of Anisus vorticulus in six side-arms in the French upper-Rh^one (Bregnier-Cordon). This species is listed in the annexes of the EU Habitat Directive and its conservation is clearly linked to the conservation of its habitat (lentic waterbodies with large densities of macrophytes – Hydrocharis – and woody debris). Other species found in backwaters of the French Upper Rh^one are protected either at a national or European level: Pomatinus substriatus, Bidessus minutissimus, Stictotarsus duodecimpustulatus, Haliplus fluviatilis (Coleoptera), Caenis pseudorivulorum, Ephemera vulgate, P. luteus (Ephemeroptera), Nymphula stagnata (Lepidoptera), Erythromma lindeni, Erythromma viridulum, Gomphus vulgatissimus, Libellula fulva (Odonata), Leptocerus interruptus (Trichoptera), Physa fontinalis, Theodoxus fluviatilis (Mollusca), Sialis nigripes (Megaloptera) (Paillex 2005). Lastly, four species present in the French part of the Rh^ one belong to the Red List of threatened species in France (Maurin & Keith 1994): Coenagrion mercuriale, Leucorrhinia caudalis, Oxygastra curtisii, (Odonata), and Pisidium pseudosphaerium (Mollusca Bivalvia).

^ne Groundwater System and its 7.5.7. The Rho Obligate Fauna (Stygobionts) Surface water-groundwater interactions are now recognized to exert a major control on structural and functional attributes of river ecosystems. Nevertheless, the groundwater

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realm flowing beneath alluvial floodplains was not obvious in the past, and its existence has only been recently incorporated into the thinking of river ecologists (Gibert et al. 1994). From extensive studies carried out on the Upper Rh^one River (Gibert et al. 1977; Seyed-Reihani et al. 1982; Dole 1983; Marmonier 1988), the four dimensional nature of streams, comprising their vertical extension, was documented, explored and included in the ‘hydrosystem’ concept (Bravard et al. 1986b; Amoros et al. 1987b, 1988; Bravard et al. 1992). Such a precursory approach was later emphasized by Stanford and Ward (1988) and Ward (1989) and is now commonly developed in many integrative studies (e.g. Malard et al. 2003). The influence of exchange processes between the epigean river and its aquifer will not be detailed here, as several syntheses are available in the literature (e.g. Stanford and Ward 1993; Brunke and Gonser 1997; Boulton et al. 1998). The alluvial aquifers of the Rh^ one host a large number of invertebrate species, ecologically heterogeneous, especially in the subsurface interactive zone (hyporheic zone) where epigean invertebrates (stygoxenes and stygophiles, Gibert et al. 1994) can seek refuge during unfavourable surface conditions, or protect their eggs and young stages from predation or other disturbances. The Rh^ one aquifers are also colonised by a number of obligate groundwater species called stygobionts. A total of 64 stygobiotic species is currently reported from the French part of the Rh^ one (tributaries excluded). Such a richness is high for the groundwater environment (Culver & Sket 2000), but it is comparable to other European large rivers (Rhine, Danube) (Dole-Olivier et al. 1994). The taxonomic composition of the stygobiotic fauna is unique compared to that of the epigean fauna. The Rh^ one stygobiotic fauna is characterized by a quasi-absence of insects (one Coleoptera species) and a strong dominance of crustaceans (36 species, 56% of total richness) and molluscs (16 species, 25% of total species richness). Three groups of crustaceans (Copepods, Amphipods and Ostracods) represent 47% of total richness, often demonstrating higher species richness in groundwater than in surface water (e.g. 10 species belong to the stygobiotic genus Niphargus compared to 4 species in the epigean genus Gammarus). Nevertheless, this remarkable composition is a characteristic of stygobiotic assemblages worldwide (Ferreira et al. 2003). The Hydrachnidia frequently colonise the hyporheic zone of the Rh^ one, but little is known on its species composition and distribution in the Rh^ one due to a lack of taxonomic expertise. Despite unique features such as rarity, endemism, strong biological and ecological singularities, vulnerability, and high patrimonial value, the stygobiotic fauna still does not benefit from clear protection status (Juberthie 1995; Danielopol et al. 2004). Spatially, stygobiotic richness is non-uniformly distributed along the Rh^ one valley corridor. Hot spots probably result from the co-occurrence of high amounts of Quaternary alluvial deposits and lateral aquifers offering possible

PART | I Rivers of Europe

connections between these entities. The thickness of alluvial deposits and their lateral expansion vary along the river continuum. Alluvial plains and constrictions succeed each other along the river course like beads on a string (Stanford & Ward 1993). Each plain is shaped by its own geologic settlement and its geomorphic and hydrologic history with the active channel, thereby offering variable environmental conditions for the development of the stygofauna in terms of permeability, water circulation patterns within interstices and other parameters (temperature, oxygenation, food availability). From present knowledge, most of the obligate groundwater species are found in the vicinity of Lyon in the Miribel-Jonage section (Creuze des Ch^atelliers 1991). This area (20 km 5 km) is especially species rich (Culver and Sket 2000; Danielopol and Pospisil 2001), hosting half of the total richness reported in the French Rh^one valley (33 species). In this section, the Rh^one drains highly permeable glaciofluvial and fluvial deposits (thickness 20–30 m, hydraulic conductivity 3.103 m/s). The water circulation pattern within the alluvia (drainage versus recharge areas) was stressed as a major determinant of faunal composition at spatial scales ranging from a few meters to several kilometres. Hyporheic flowpaths were described in relation with the geomorphology of the river (lateral channel types, meandering, changes in slope, outcrops and knickpoints) (Dole & Chessel 1986; Marmonier & Dole 1986; Marmonier 1988; Creuze des Ch^atelliers & Reygrobellet 1990; Creuze des Ch^atelliers 1991; Dole-Olivier & Marmonier 1992a; Marmonier et al. 1992). The composition of the stygobiotic fauna was shown to change in a similar way along the longitudinal, lateral and vertical dimensions from the main channel to the floodplain margins, from upstream to downstream reaches and from subsurface to deep phreatic zones (concept of repeated gradients, DoleOlivier et al. 1993, 1994). Temporal changes in stygobiotic fauna during flow disturbances matched those observed along the three spatial dimensions of the river system (Marmonier & Dole 1986; Dole-Olivier & Marmonier 1992b; Dole-Olivier et al. 1997). Less species-rich areas were investigated by Creuze des Ch^atelliers (1991) in the Bregnier-Cordon section (French Upper Rh^one) and Donzere-Mondragon section (200 km south of Lyon), but these investigations were restricted to the active channel of the river and did not extend into the floodplain. Stygobiotic biodiversity of the Rh^one is clearly under-studied. Promising and extensive explorations must be developed in poorly known areas to better assess species richness, especially in the southern part of the river corridor (e.g. Avignon-Arles section), focusing on the floodplain dimension rather than the active channel submitted to intense clogging downstream of the Isere. The concomitant influence of past marine transgressions/regressions (i.e. source of marine colonizers), the absence of Quaternary glaciations and the presence of permeable aquifers suggest high levels of biodiversity in these areas.

Chapter | 7 The Rh^ one River Basin

7.5.8. Fish Geologically, the Rh^ one catchment emerged from a sea basin in front of the Alps orogenesis. The colonization by freshwater organisms, especially fish, can be considered as rather recent. During the Pliocene, the alpine Rh^ one and Rhine formed the head of the Danube catchment and the fish fauna of these rivers was probably the same (Persat et al. 1995). Glaciations depleted Danubian species in the Rh^one and the Rhine (Persat 1988; Persat & Berrebi 1990): the most thermophilic and limnophilic species such as Silurus glanis were eradicated from the Rh^ one and Rhine. On the other hand, glaciations allowed the colonization of the Rh^ one by cryophilous species such as salmonids, bullhead (Cottus gobio), and burbot (Lota lota) (Persat & Keith 1997). The apron (Zingel asper) is the only endemic species in the Rh^one and, until recently, the only major endemic fish in France. It testifies to the ancient connection of the Rh^ one with the Danube that was inhabited by two species of the same genus: Z. zingel and Z. streber. The fish fauna of the Rh^one also includes some southern species: blageon (Telestes souffia), southern barbel (Barbus meridionalis), soiffe (Chondrostoma toxostoma) and river blenny (Salaria fluviatilis) (Persat 1988). The southern part of the catchment served as refuge during glaciation for several species. For instance, the northern limit in distribution of southern barbel is the Isere subbasin. Colonization of the different sub-basins by species after glaciation and before construction of major barriers in the 19th century led to the current distribution of native species. The history of the Rh^ one corridor during the last two million years shows that several sections in the river can be distinguished. The upper river, including the Swiss Upper Rh^ one and Lake Leman, was covered by the W€ urmian glacier. After glacial retreat, the ‘Perte du Rh^ one’, a crevice like canyon cut in the thick Urgonian limestone layer 42 km downstream of Geneva was a natural barrier for most fishes downstream. Only some rheophilic species as brown trout (Salmo trutta), minnow (Phoxinus phoxinus) and grayling (Thymallus thymallus) might have colonized the Upper Rh^ one by crossing this canyon (Persat & Keith 1997). Several uncertainties exist about how other species colonized the river upstream of ‘Perte du Rh^ one’, and the native status of many species is still questionable. From ‘Perte du Rh^one’ to Avignon, the Rh^ one was a large braided river with high flows and sediment inputs provided by alpine tributaries. These hydro-morphological features allowed the persistence of a rheophilic community typical of the barbel zone (Kreitmann 1932; Persat et al. 1995). Presently, the Rh^ one extending down to the Sa^ one confluence, usually called ‘French Upper Rh^ one’, is considered as a separate entity, and the lower Rh^ one from the Sa^ one to the Camargue delta is the last entity. Excluding the Rh^ one, Changeux and Pont (1995) recognized three main ichthyogeographic regions in the French catchment: the Sa^ one basin, the Durance basin and Mediterranean tributaries of the Rh^ one, and the Isere basin as a

267

typical alpine drainage. Each ichthyogeographic region has different climatic features: cool and humid in the Sa^ one basin (oceanic regime), dry and hot in the south (Mediterranean regime), and cold water in the alpine region (elevation effect). Fish communities in lowland rivers (Sa^one basin) and moderate altitude rivers from the Jura mountains included bitterling (Rhodeus amarus), three-spined stickleback (Gasterosteus aculeatus), burbot, ruffe (Gymnocephalus cernuus), black bullhead (Ameiurus melas), and silver bream (Blicca bjoerkna). In southern rivers (southern Alps and the Mediterranean) fish species include southern barbel, eel (Anguilla anguilla), soiffe, pike perch (Sander lucioperca), apron, blageon and carp (Cyprinus carpio) (Changeux 1995). Alpine fish communities included brown trout, bullhead, grayling and brook lamprey (Lampetra planeri). In the internal Alps, non-native species such as brook trout (Salvelinus fontinalis) and rainbow trout (Oncorhynchus mykiss) could constitute major fractions of the community. Fish richness was positively correlated with the natural logarithm of the size of the sub-basins. At the intra-regions scale, the main factors influencing the presence or absence of different species were river slope, distance from the source, and hydrological features of the different sub-basins. In the Alps, altitude, which influences water temperature and flow regime, was an important factor explaining species presence. Since 1860, 11 fish species have been introduced. In 1860, the ruffe (Gymnocephalus cernuus) was found in the Rh^one. The species was native in the Meuse, Moselle and Rhine catchments, and was probably native in the Ognon River, a tributary of the upper Sa^one. In 1880s, the nase (Chondrostoma nasus) colonized the French basins through artificial waterways. It was first in the Sa^one (around 1840), then in the French Upper Rh^one (around 1880) and in the Ain River (in 1903). Rainbow trout (O. mykiss) were introduced in the Rh^one catchment in the same decade than the nase. In 1920, two other North American species were found in the Rh^one: the black bullhead (Ameiurus melas) and the pumpkinseed (Lepomis gibbosus). In 1930s, the pike perch (Sander lucioperca) colonized the Rh^one and probably arrived in the Sa^one and Doubs rivers from the Rhine-Rh^ one Canal around 1910. The mosquitofish (Gambusia affinis) was introduced in south France to control mosquito populations. In 1940s, largemouth bass (Micropterus salmoides) was introduced for angling and the species developed small populations in the Rh^one, mainly in the south. In 1987, the wels (Silurus glanis) was caught in the lower Rh^one. It was noted in the Doubs River around 1930 and was introduced in the Sa^one in 1975 by anglers from where it colonized the lower Rh^one and then the French Upper Rh^one. The species was also introduced in several reservoirs (i.e. Vouglans in the Ain River). This species was native in the Rh^one River during the Miocene but was extinct during glaciations. In 1989, the Prussian carp (Carassius auratus gibelio) and topmouth gudgeon (Pseudorasbora parva) were recorded for the first time in the French lower Rh^one and then in the Upper Rh^ one in 2003, whereas goldfish (Carassius auratus) was probably

268

introduced earlier. Carps were introduced by Romans and crucian carp (Carassius carassius) probably colonized the Rh^ one during the 18th or early 19th century.

^ne 7.5.9. Fishes in the Swiss Upper Rho Originally, 17 native species belonging to 8 families occurred in the Swiss Upper Rh^ one and tributaries (Fatio 1882, 1890). These included cryophilic species (bullhead, brown trout – and Lake resident trout – , grayling), rheophilic species such as schneider (Alburnoides bipunctatus), minnow, stone loach (Barbatula barbatula) and limnophilic species (roach – Rutilus rutilus – , rudd – Scardinius erythrophthalmus – , tench – Tinca tinca). The native status of several species, such as burbot, eel, perch (Perca fluviatilis) and some thermophilic ones (roach, rudd, tench) is still doubtful because of the ‘Perte du Rh^ one’ barrier. Of these species, only 9 are present today and brown trout is the dominant species (K€ uttel 2001; Peter & Weber 2004; Weber et al. 2007). The first (1863–1894) and second (1930–1960) river corrections for flood protection led to a decrease in lateral connectivity, floodplain habitat heterogeneity and fish diversity (Weber et al. 2007). Five species were introduced in the Swiss Upper Rh^ one (three-spined stickleback, crucian carp, carp, rainbow trout and brook trout), although carp is no longer present.

7.5.10. Fishes in Lake L eman Thirty species are present in Lake Leman; 20 are considered native and 10 were introduced (e.g. rainbow trout and brook trout). Salvelinus alpinus and Coregonus lavaretus are native species that occurred naturally only in Lake Leman and Bourget Lake. These species are sensitive to eutrophication and, presently, S. alpinus populations are sustained by stocking (http://www.thonon.inra.fr/poisson/ pacagelacustre/pacagesalmonides/omblechevalier/omblepacage.htm). The two initial forms of C. lavaretus present in the lake disappeared at the beginning of the 20th century, being replaced by other forms of the same species (Gerdeaux 2001). These salmonids, perch, and to a lesser extent trout (S. trutta, lacustrine form) and pike are species of interest for anglers and professional fishermen (http://www.cipel.org/sp/). The native status of several species (especially the thermophilic cyprinids) is still doubtful. The three-spined stickleback was introduced in a pond near Hermance (Leman basin) in 1872 and was probably in Lake Leman at the end of the 19th century (Fatio 1890). Burbot was introduced during the 15th century (Lunel 1874).

^ne Downstream From 7.5.11. Fishes in the Rho ^ne Geneva and French Upper Rho Gobin (1868) divided the French upper Rh^ one into five sections. In the first, from the border (24 km downstream from Lake Leman) to the ‘Parc’ (57 km from Lake Leman, pres-

PART | I Rivers of Europe

ently just downstream from Genissiat Dam) were brown trout, chub (Leuciscus cephalus), burbot, gudgeon (Gobio gobio) and minnow. Barbel (Barbus barbus), carp, pike and perch were present only downstream of ‘Perte du Rh^ one’. Upstream of the ‘Perte du Rh^one’ canyon, barbel was introduced in 1888 (Anon. 1938) and bream (Abramis brama) at the beginning of the 20th century (after 1938). A few eels were able to migrate above the ‘Perte du Rh^one’ (Kreitmann 1932). The cold turbid water of the Arve River near Lake Leman outlet decreased the temperature in the Rh^one during snow and ice melting periods, and species recorded in the Arve (brown trout, grayling, chub and gudgeon) probably colonized the Rh^one downstream of the confluence (Kreitmann 1932). The second section between the ‘Parc’ and the outlet of Bourget Lake (‘Canal de Saviere’) had a diversity of habitats for fish as the Rh^one flowed through a wide braided floodplain with numerous side-arms and wetland areas in the ‘Chautagne’ and ‘Marais de Lavours’, respectively. Lentic side-arms were used by phytophylic species for reproduction (pike, perch, tench and carp). The floodplain was considered the most productive fishery in the French upper Rh^one. The tributaries of ‘Les Usses’, ‘Dorche’ and ‘Fier’ were commonly used by several species for breeding and as refuge against floods. Trout, grayling, barbel, pike, eel, perch, chub, dace (Leuciscus leuciscus) and gudgeon were the most abundant species (Gobin 1868; Anon. 1938). The grayling population was very important. Among non-native species, the nase had a high population density in the braided section and notable migrations into tributaries were reported, especially in the Usses and Fier (Anon. 1938). The third section runs from the confluence with Bourget Lake outlet 84 km downstream of Geneva to Sault-Brenaz 154 km from Geneva. It had large floodplains, three narrow canyons and 13 tributaries. The Guiers River flowing from the Chartreuse Mountains is the main tributary with trout, grayling, burbot, barbel, chub, and dace. River blenny, an abundant species in Bourget Lake, was mainly present in the Rh^one downstream from the lake outlet (Leger 1943). The apron was also present (Leger 1943). This third section was the upstream limit of twaite shad (Alosa fallax rhodanensis) and sea lamprey (Petromyzon marinus) in the Rh^one. Burbot was abundant because of the presence of small tributaries and numerous ditches in wetlands. Grayling abundance was lower than in the second section. In the lower part, fish productivity decreased because side-arms and backwaters were less numerous. Eel was abundant both in the Rh^ one and tributaries. The fourth section between Sault-Brenaz and the Ain confluence was considered relatively poor compared to the upper sections. In this stretch, the river flowed between steep banks, islands were scarce and it had only one tributary: the Bourbre River. The main fishes were pike, tench, barbel, chub, perch, carp and bream. In the last section from the Ain confluence to Lyon, the Rh^one flowed through a meandering zone until Jons and, then,

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Chapter | 7 The Rh^ one River Basin

in a 15 km long braided section until Lyon. Engineering works conducted after 1850 to improve navigation led to the disconnection of meanders which occur now as oxbow-lakes (Bravard 1987; Roux et al. 1989). The floodplain offered a large diversity of habitats and species such as trout, dace, barbel, pike, carp, tench, chub, perch, bream, roach, rudd, gudgeon and minnow. The presence of blageon was cited in the French Upper Rh^ one by Kreitmann (1931) and Leger (1943). Soiffe was not noted by Gobin (1868) but was probably present, at least from the third section to Lyon (Leger 1945). Its occurrence was noted later in the last section (Anon. 1938). Bullhead was mentioned in the Rh^ one but was probably more abundant in tributaries. Bitterling was recorded only in the 5th section but should have been present upstream. Today, the fish community of the Rh^ one between Geneva and Lyon is strongly affected by 10 hydroelectric schemes. In the Swiss Rh^ one, downstream from Lake Leman, monitoring revealed the presence of 28 species, including brown trout, grayling, pike, bream, bleak (Alburnus alburnus), barbel, gudgeon, chub, blageon, minnow, bitterling, roach, rudd, tench, stone loach, black bullhead, three-spined stickleback and perch. Some other species are present but rare: schneider, carp, pumpkinseed and bullhead. The very rare occurrence of species such as S. alpinus, Coregonus spp. and burbot is linked to the proximity of the lake. Eel and goldfish were caught occasionally, mostly from recent introductions (S.F.P. N.P. Geneve 2003). The Genissiat dam was built from 1937 to 1947 and represented the first and highest barrier to fish migration. Daily water level fluctuations from hydroelectricity production are currently regulated by the Seyssel compensation dam built in 1951 and located 7.5 km downstream of Genissiat dam, and the fish community is quite poor. Five low waterfall hydroelectric schemes with by-pass sections between Seyssel and Lyon fragment the river and create new artificial waterbodies as reservoirs and canals. Despite an altered discharge regime, by-pass sections provide suitable habitat for most fish species, especially lithophilic fishes. Presently, 44 species occur in the French Upper Rh^one. Eels are stocked, soiffe are very rare, and natural trout and grayling populations are found (Persat & Eppe 1997). The introgression of foreign genes in grayling populations shows the impacts of stocking operations during the last 50 years. Trout and grayling are still present up to Lyon, at least in bypass sections and connected flowing channels. The cyprinid community in the French Upper Rh^ one is dominated by chub, barbel, schneider, gudgeon and minnow. Dace, nase and blageon are less common, probably because of habitat alteration. Lentic reservoirs and some side-arms and backwaters provide habitat for limnophilic (rudd, tench, crucian carp, pike, pumpkinseed and, locally, pond loach – Misgurnus fossilis) and potamophilic species (bream, bleak, pike perch, carp, ruffe, wels, bitterling and perch) (Persat et al. 1995; Klingeman et al. 1998). River blenny is regularly sampled near the Bourget Lake outlet, and burbot is rare. Coregonus sp. from Geneva Lake or Bourget Lake is sampled periodically. In the past 20 years, the increase in mean

annual water temperature is believed to be responsible for the decrease in dace and increase of thermophilic species such as chub, schneider and barbel (Daufresne et al. 2003).

^ne 7.5.12. Fishes in the French Lower Rho Kreitmann (1932) noted that the same fish species (except Acipenser sturio and euryhaline fishes) were found along the 248 km of the Lower Rh^one, classified as a barbel zone. The average slope was relatively high (50 cm/km), discharge was 1500 m3/s at Viviers, and the slope reached 1.44 m/km several kilometres downstream of Valence. The substrate was mainly coarse alluvium with silt and sand deposited along the banks and in backwaters. Because of the influence of Mediterranean rivers on the hydrology of the Rh^ one, the lower Rh^one was divided into three section, a first one from the Sa^one confluence to the Eyrieux confluence (125 km), a second one downstream from the Eyrieux confluence to the Durance confluence (123 km) and a third one close to the Mediterranean Sea. The fish community in the first section had at least 36 species, including large migratory fishes (twaite shad, sea lamprey, river lamprey Lampetra fluviatilis and eel), brown trout, grayling, burbot, bullhead, dace, blageon, soiffe, bleak, roach, barbel, bream, perch, ruffe, stone loach, apron, river blenny and pike. The channel of the second section was considered as unstable with coarse sediment transport and high loads of suspended matter. Side arms and backwaters were more numerous in this section and played an important role for fish reproduction and nursery for young-of-the-year. The floodplain area was reduced by engineering works (Girardon’s embankments) in the 19th century for navigation, and in the 1930s a decline in common sturgeon (A. sturio) was already noted and recorded only up to the Ardeche confluence. The lowest part of the river is divided in two arms: the ‘Petit Rh^one’, right branch of the delta, and the ‘Grand Rh^one’, left branch of the delta (Photo 7.4). Both marine and freshwater species occurred in these arms because of the mixture of salt waters and freshwater. Seven species were commonly fished in the ‘Petit Rh^one’ (carp, tench, common bream, silver bream, rudd, perch and chub), three were rare (blageon, dace, Rh^ one streber) and common white fish and grayling were found very occasionally. Marine species were reported upstream from the river mouth (brackish water): flounder (Platichthys flesus), brill (Scophthalmus rhombus), turbot (Psetta maxima), common sole (Solea solea), bass (Dicentrarchus labrax), thick-lipped grey mullet (Chelon labrosus), golden grey mullet (Liza aurata). Other species as sea lamprey, common sturgeon, eel, shad and flat-headed grey mullet (Mugil cephalus) were found more upstream (freshwater). In the ‘Grand Rh^one’, the marine species were also recorded and some of them far upstream in freshwaters (i.e. bass). Freshwater species were found from Arles to Saint-Louis (upstream limit of brackish water): carp, common bream, silver bream, rudd, barbel (rare), perch, pike and trout (mainly after large floods) (Gourret 1897).

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PHOTO 7.4 Mouth of the Rh^one River near Port-Saint-Louis (Photo: Compagnie Nationale du Rh^one).

Today, 43 fish species occur in the Lower Rh^ one, and the common sturgeon is extinct (Table 7.6). The French Lower Rh^ one fish community differs from the French Upper Rh^one community because of the near absence of brown trout, dace, minnow, blageon, soiffe, burbot and bullhead. The grayling is absent, eel densities are higher than upstream of Lyon and twaite shad is only found downstream of Montelimar. The 12 hydroelectric schemes altered channel morphology, thermal regime, and substrate of the river. This river section also was regularly impacted by pollution. From the Sa^ one River to the Isere River, the fish community mainly comprises potamophilic and limnophilic species that are well-adapted to slowflowing regulated sections with warmer temperature and moderate pollution (e.g. roach, chub, bleak, bream, tench, rudd, carp, pike perch, black bullhead and pumpkinseed). Barbel and nase still occur in bypass sections and river blenny is found in low abundance. From the Isere River to the Ardeche River, the community structure changes because of the presence of rheophilic species such as schneider, blageon, gudgeon, barbel, nase, stone loach, bullhead, and to a lesser extent dace and soiffe. Here, water temperature is lower, slope is higher, and bypass sections longer than upstream, thereby providing suitable feeding and spawning habitats for rheophilic species. Bitterling is present in both sections, mainly in bypass reaches. Downstream of the last hydroelectric power plant, the Rh^ one flows to Arles and then forks in two arms that form its delta. Between Vallabregues power plant and the delta, several artificial backwaters (dikes built during the late 19th century) and dead arms are used as reproduction and nursery areas (Poizat & Pont 1996; Pont & Nicolas 2001). The main species occurring in this river section are chub, pumpkinseed, silver bream, roach, nase and gudgeon. Other species such as bleak, black bullhead, rudd, bream, tench and barbel

are present in lower numbers. The fish community comprises 45 species, among which 10 are euryhaline species (Atherina boyeri, Gobius niger, D. labrax, C. labrosus, L. aurata, Liza ramada, Liza saliens, M. cephalus, P. flesus, Syngnathus abaster) and four are large migratory species. Physical barriers from river regulation have reduced longitudinal distributions of euryhaline species. Bass (D. labrax) and mullets (L. ramada, M. cephalus) migrated as far as the Durance River confluence 85 km upstream from the sea (Kreitmann 1932). Today, the bass distribution is limited to the 65 km lower section of the river because of the Vallabregues power

TABLE 7.6 Total number of fish species (including extinct), number of remaining native, non-native species, and extinct fish species in various river sections along the Rh^ one River River sections

Total Native Non-native Extinct

Swiss Upper Rh^ one Lake Leman French Upper Rh^ one French Lower Rh^ one Rh^ one delta Ain Upstream Vouglans Ain Vouglans Reservoir Lower Ain Upper Sa^ one Lower Sa^ one Upper Durance Serre-Pon¸con Reservoir Middle Durance Lower Durance

22 30 45 44 46 18 25 32 38 38 5 11 28 37

*

9 20 29 29 34 16 16 24 28 23 4 10 20 23

5 10 15 14 11 2 9 7 10 12 1 1 8 13

8 0 1 1 1 0 0 1 0 3* 0 0 0 1

the endangered species Zingel asper is not officially considered as extinct but has not be observed for a long time.

Chapter | 7 The Rh^ one River Basin

plant and weir in the by-pass. The two Mullets benefited from rehabilitation measures for twaite shad to pass upstream of the Vallabregues hydropower station and have been found upstream as far as Avignon. The thin-lipped grey mullet (L. ramada) is most abundant.

7.5.13. The Apron The apron, Zingel asper, is a small endemic fish in the Rh^one basin. In 1900, it was distributed throughout the Rh^one catchment but was absent upstream from ‘Perte du Rh^one’. Today, it inhabits a few locations in the Ardeche, Durance and Doubs basins. The two most important populations are those in the Durance and Beaume (Ardeche) basins. A few individuals were still present in the Ain River in 1989 and more recently in the Dr^ ome River. In the Rh^one, a few individuals were recorded between 1950 and 1980, at Yenne 93 km downstream of Geneva near Bourget Lake and, in Miribel Canal a few km upstream of Lyon. The last known capture in the Rh^ one was in May 1985 at Vernaison 12 km downstream of Lyon. The presumed reasons of the decline of the apron are (1) the general decrease of the natural flow regime, (2) the degradation in both quality and quantity of water in rivers and, (3) gravel extraction and other works in riverbeds. Recent studies improved the knowledge of the species regarding habitat use and reproductive behaviour (Labonne et al. 2003; Danancher 2005; Labonne & Gaudin 2005), population genetics (Laroche & Durand 2004) and diet (Cavalli et al. 2003). A Conservation Program has been initiated to protect the remaining individuals and restore the population (http://www.cren-Rh^ onealpes.fr/part2/progs/ life_apron.htm). Indeed, the apron is referenced in Appendix II of the Bern Convention on the Conservation of the Wildlife and Natural Environments in Europe, in Appendices II and IV of the European Fauna-Flora Habitats Directive, and in the Red List of threatened species in France. The program aims to (1) perform a demographic survey of known populations, (2) develop suitable fishways for the species, (3) increase the connectivity between habitats (Durance, Ardeche) to increase the number of individuals, the spatial distribution of the species, and the genetic mixing in the population, (4) organize and develop a monitoring survey of river stretches where the species is present, (5) develop experiments for artificial reproduction, (6) experimental restocking operations, and (7) inform people about the results and the biology of the apron.

^ne 7.5.14. Migratory Fishes in the Rho Five migratory species occurred in the Rh^ one catchment in the early 20th century: sea lamprey (P. marinus), European river lamprey (L. fluviatilis), sturgeon (A. sturio), twaite shad (Alosa fallax rhodanensis) and European eel (Anguilla anguilla). The biology and ecology of the two lampreys are poorly documented. They occur in Camargue and in the ‘Petit

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Rh^one’. Their upstream distributions are limited to Avignon and the downstream part of the Durance. The sturgeon was reported as highly abundant during the Middle Age. Overfishing reduced the population as early as the 13th and 14th centuries, and the decline was intensified during the 19th and 20th centuries because of river embankment and regulation. The last known catch occurred in 1969–70 at the river mouth and in 1954–55 near the Ardeche confluence, although another catch was reported downstream of Arles in 1989. This species is now protected and a project to restore populations in the Rh^one is under development. Two species of shad were mentioned by Leger (1945/ 48), the Rh^one twaite shad (Alosa fallax rhodanensis) and the allis shad (Alosa alosa). Today, only the Rh^one twaite shad, considered as a discrete group within the species Alosa fallax, is present in the lower Rh^one (Le Corre et al. 1997, 1998, 2000, 2005). Alosa alosa was stocked in the 1950s in the Rh^one and a few hybrids (A. fallax A. alosa) were found in the Aude River, a small French Mediterranean river. In the Sa^one, before 1882, the upstream migration of the twaite shad reached Auxonne at 220 km upstream of Lyon and was reported from the downstream end of the Doubs River. Until 1937, in the French Upper Rh^one, shad migrated up to Bourget Lake. In the Isere River, the migration was reported as far as Grenoble. The lower parts of southern tributaries (Ardeche, Ceze, Durance, Gardon) were also used for reproduction. The migration of the twaite shad along the lower Rh^one and the main tributaries has been constrained by 27 dams or weirs. The first barrier on the Sa^ one was the ‘La Mulatiere’ dam built in 1882 just upstream of the confluence with the Rh^one. In 1921, access to the Isere River was closed by the construction of ‘Beaumont-Monteux’ dam (7 km from the confluence with the Rh^ one). The twaite shad was stopped at Lyon in 1937 after the completion of the ‘Jons’ dam only few kms upstream of Lyon, and the use of the reproduction sites along the lower Rh^one was limited by the ‘Donzere-Mondragon’ (1952) and ‘Vallabregues’ (1974) hydroelectric schemes. Until recently, the reproduction of the twaite shad was limited to the lower Rh^one downstream of the last dam. Since 1994, a large program that aimed towards restoring migration ways for the twaite shad in the Rh^one catchment allowed spawning migration in the Rh^one in the Donzere bypass section and in 3 tributaries (Ardeche, Ceze and Gardon). In 2006, young-of-the-year shad were sampled near Montelimar at 165 km from the sea, providing evidence of reproduction in this area. Morphological and biological data on upstream migrant twaite shads are now available on the Rh^one (Le Corre et al. 2000). The spawning migration occurs between March and June, and the age of spawners ranges from 2 to 8 years for males and 3–8 years for females. Sizes range from 255 to 490 mm for males and 335–520 mm for females. The growth rate and longevity of the Mediterranean twaite shad are greater than those of Atlantic allis shad.

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The eel population is poorly described and few relevant data are available to estimate the stock in the Rh^ one, except catches by professional and amateur fishermen. The mean annual eel catch by professional fishermen is 9239 kg/year in the delta and 7275 kg/year in the lower Rh^ one, and 38 kg/year (delta) and 179 kg/year (lower Rh^ one) by amateur fishermen (data 1999–2002, Conseil Superieur de la P^eche 2005). Crivelli (1998) indicated biomasses ranging from 3.0 to 2269 kg/ha in canals in Camargue and from 0.2 to 40 kg/ha in ponds. Data collected from 1979 to 2005 by diverse groups monitoring fishes downstream of Lyon were used to assess spatial and temporal changes in eel population densities and size-class structure. Over 400 electrofishing operations were used and 4 size classes were considered (Figure 7.5). The smallest eels (first and second size-classes) were mostly present downstream of Vallabregues dam, highlighting this structure as a migration barrier. Large eels (>440 mm, >4 years) dominated upstream samples. The largest individuals were still present as far as 300 km from the sea while the CPUEs (catch per unit effort) remained very low. The long-term survey of the CPUE (data from 1980 to 2005 collected from Arles to the third dam downstream of Lyon) showed a regular decrease in eel densities as the number of dams from the sea increased. In each section, CPUEs decreased after 1995, and this fact agrees with the general decline in European eel populations reported in the literature. Moreover, the presence of dams near the delta affects strongly the upstream migration and, the availability of suitable habitats for eel downstream of Lyon is very low. Eel abundance in the Rh^ one is 10–100 lower than in the Loire River, France. Further, a large number of young eels are probably removed and sold locally or exported to Italy and Japan. To restore eel populations, resource managers should improve migration pathways, better manage flows, connect backwaters, and improve water quality. Several studies are

FIGURE 7.5 Mean abundance of eel (four size classes, in mm, and for all size classes combined, total) between the Mediterranean Sea and Lyon (average values; 1979–2005). Catch per unit effort (CPUE) corresponds to the number of eel caught at a given station by electrofishing during 20 min. The location of the hydropower stations is indicated.

PART | I Rivers of Europe

examining the potential effects of Anguillicola crassus, a nematod parasite affecting yellow and silver eel physiology and swimming capacity. Infection rates can reach 80% of silver eels in Camargue (Lefebvre et al. 2006). Eels are currently restocked as well as in the French Upper and Lower Rh^one. Between 1994 and 2004, 3 243 000 EU have been spent to improve the upstream migration of fish in the lower Rh^ one up to Avignon and several tributaries (Ardeche, Gardon, Ceze).

7.5.15. Amphibians Of the 35 amphibian species recorded in France and Switzerland, 23 occur in the Rh^one floodplain (7 species of Urodela and 15 species of Anoura) and one in Lake Leman (Rana latastei). Among the Anoura, Rana kleton esculenta is a hybrid between Rana ridibunda and Rana lessonae, and Rana kleton grafi was from the natural crossing between Rana ridibunda and Rana perezi. Loss of wetlands and small ponds, water pollution, habitat fragmentation and use of insecticides are responsible for the decline in most amphibian populations, except for the marsh frog (R. ridibunda). This species disperses from central Europe and competes with native species such as Perez’s frog (R. perezi), western spadefoot (Pelobates cultripes) and yellow-bellied toad (Bombina variegata). The common toad (Bufo bufo), fire salamander (Salamandra salamandra) and palmate newt (Triturus helveticus) occur locally all along the Rh^one. The common frog (Rana temporaria), pool frog (R. lessonae) and edible frog (Rana kleton esculenta) are absent in the Rh^ one delta. Perez’s frog (Rana perezi) and Graf’s frog (Rana kleton grafi) are typical Mediterranean species and occur from the delta marshes to Montelimar. Common frog populations have decreased since the 1950s. The midwife toad (Alytes obstreticans), well-distributed along the Rh^ one River, has disappeared in the Swiss Rh^one downstream of Lake Leman since 1980, despite multiple re-introductions (Geneva Herpetological Society). Some amphibians are mainly found in the northern part of the Rh^one. Smooth newt (Triturus vulgaris) and alpine newt (Triturus alpestris) are rare in the French Upper Rh^one and Lower Rh^one floodplains upstream of Montelimar but are absent downstream. South great crested newts (Triturus cristatus) are scarce because of the lack of reproduction areas. Backwaters around Arles have been identified as the last southern reproduction areas for this species. Around Geneva, South great crested newt populations have been declining since 1987 because of the nonnative Italian great crested newt (Triturus carniflex). Among the Anoura, the common tree frog (Hyla arborea) occurs mainly in the Upper Rh^one floodplain, while the agile frog (Rana dalmatina) is found as far as Montelimar. Other amphibians are mainly present in the south part of the Rh^one River. The Mediterranean tree frog (Hyla

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Chapter | 7 The Rh^ one River Basin

meridionalis) is commonly found in Camargue and in the lower Rh^ one floodplain. Until recently, the Mediterranean tree frog and common tree frog co-occurred between Lyon and Valence but river regulation and the loss of wetlands led to their quasi-extinction. The Western spadefoot is present from the delta to Valence, and the Parsley frog (Pelodytes punctatus) and natterjack toad (Bufo calamita) are found in the south with abundances decreasing from south to north. The natterjack toad occurs regularly along the river. The yellow-bellied toad has disappeared in the Mediterranean part of the Rh^ one since the early 20th century. Most amphibian species are protected.

7.5.16. Reptiles Three snake species and two turtles are linked to aquatic biotopes along the Rh^ one River. The dark green snake (Coluber viridiflavus), European grass snake (Natrix natrix), viperine water snake (Natrix maura) are protected both nationally and internationally (Bern Convention), and the dark green snake is listed in annex IV of the directive 97/ 62/EEC on the conservation of natural habitats and of wild fauna and flora. Two populations of European pond terrapin (Emys orbicularis) are known, one at ‘l0 Ile Cremieu’ on the French Upper Rh^ one and the other in Camargue. European pond terrapin populations have declined because of competition with the non-native Trachemys scripta (red-eared slider). The European pond terrapin is listed in annexes II and IV of the directive 97/62/EEC on the conservation of natural habitats and of wild fauna and flora.

7.5.17. Birds Some common bird species occur regularly along the Rh^one River, including the grey heron (Ardea cinera), common kingfisher (Alcedo atthis), common black-head (Larus ridibundus), black kite (Milvus migrans), Eurasian coot (Fulicula atra), Eurasian reed-warbler (Acrocephalus scirpaceus), mallard (Anas platyrhynchos), mute swan (Cygnus olor), and common moorhen (Gallinula chloropus). The black kite and Eurasian reed-warbler are common along the Rh^ one and have stable populations. Population sizes of grey heron, Eurasian coot, mallard and common moorhen have increased because of their ability to colonize artificial wetlands and waterbodies, especially around towns. The grey heron was classified as harmful (it has almost disappeared during the 19th century) and as a game bird in 1967, but today this species is protected. The mute swan was considered very rare in 1936, but the number of individuals has increased considerably since the 1970s as the species became sedentary. In contrast, habitat alteration caused a decrease in populations of common kingfisher populations during the 20th century. The same is true for the little bittern (Ixobrychus minutus), which occurs in the Leman basin and downstream in the lower Rh^ one. The Eurasian curlew

(Numenius arquata) and bluethroat (Luscinia svecica) have stable populations, although these species are uncommon and nest only in the French Upper Rh^one. The grasshopper warbler (Locustella naevia) and marsh warbler (Acrocephalus palustris) occur in the French and Swiss Upper Rh^ one and their distributions are increasing, especially the marsh warbler since 1980–1990. This species seems to tolerate urbanization and dry habitats. The Camargue is famous for birds because it has the highest species richness in France with 398 species (of which 132 nest there) out of 512 recorded. The Carmargue also is a wintering area (many duck species), an important nesting ground (little bittern, squacco heron – Ardeola ralloides), and a stopping place for migratory species (i.e. red knot – Calidris canutus). Long-term trends were reported for several species. The grey heron, buff-backed heron (Bulbucus ibis) and little egret (Egretta garzetta) populations have increased, while black-crowned night-heron (Nycticorax nycticorax) and purple heron (Ardea purpurea) populations have declined. The Camargue is the only French site where nine species of heron nest. It is also the main wintering area for ducks in France (average of 150 000 individuals), especially for common teal (Anas crecca), mallard, Eurasian wigeon (Anas penelope), gadwall (Anas strepera), northern shoveler (Anas clypeata) and common pochard (Aythya farina). Mallard, gadwall and red-crested pochard (Netta rufina) reproduce in Camargue. Several species of waders have relatively stable populations such as the common ringed plover (Charadrius hiaticula), kentish plover (Charadrius alexandrinus) and pied avocet (Recurvirostra avosetta). In France, collared pratincole (Glareola pratincola) nests only in Camargue; this species is mainly associated with rice fallow lands and temporary ponds and is only found in a few places in the delta. Among Laridae, some populations are increasing such as Caspina gull (Larus cachinnans) or Mediterranean gull (Larus melanocephalus), while others are decreasing such as little gull (Larus minutus) or common tern (Sterna hirundo). Several other species such as the common black-head have relatively stable populations. The Camargue is the most important site for greater flamingo (Phoenicopterus roseus) nesting in the west Mediterranean region and the only one in France. Between 1983 and 2002, the number of nesting pairs varied from 8600 to 22 200 pairs. The number of individuals has increased during the past 50 years, especially after the creation of a special area at ‘Salins de Giraud’.

7.5.18. Mammals Among mammal species that occur along the Rh^ one, attention will be on species with useful and accurate data. In the past, European otter (Lutra lutra) and European beaver (Castor fiber) were common along the Rh^one, but were hunted for their fur and almost disappeared during the 19th century. In 1909, the protection of European beaver in southern France allowed the recolonization of the Rh^ one basin and the species reached Lyon around 1960. The

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species is now found along the whole river from Switzerland to Camargue. The European otter is protected at national (France and Switzerland), European and international levels. This species is classified as ‘near threatened’ in the IUCN red list of threatened species. The European otter is sensitive to habitat alteration but is still present in low numbers in the French part of the river. The last observations in the Swiss Upper Rh^ one were in 1970. The Southwestern water vole (Arvicola sapidus) is also listed in the IUCN red list as ‘near threatened’. Indeed, the populations are critically threatened and the species is neither protected at the national or European level. This species was very common, but wetland draining, river embankments and competition with the non-native coypu (Myocastor coypus) and muskrat (Ondatra zibethicus) were probably responsible for its decline. The situation is the same for Eurasian water shrew (Neomys fodiens) but it is protected by French law and the Berne Convention. In 1940, the North-American muskrat was absent in the Rh^ one valley. It was recorded in 1960 in the Ain and in the French Upper Rh^ one floodplain in 1970. In Switzerland, one observation was reported around 1990 upstream of Lake Leman. Today, the main goal is to limit its distribution because it is considered as a vermin in France. Coypu was introduced in France at the end of the 19th century and it spread along the Rh^ one river valley during the 20th century and will probably reach Switzerland (Geneva) soon. The coypu is considered as a vermin because they cause damages by digging holes and usually feed on agricultural plants. Among the 19 Chiroptera species identified along the Rh^one, Daubenton’s bat (Myotis daubentonii) and Geoffroy’s bat (Myotis emarginatus) are protected. They occur in alluvial forests and their presence seems to be strongly related to waterbodies.

7.6. MANAGEMENT AND CONSERVATION 7.6.1. Economic Importance Minor hydroelectrical production occurred in the Valais from 1902 to 1950. An exponential increase in high-head hydropower schemes in the Swiss Upper Rh^ one occurred from 1951 to 1975. From 1976 to 2003, small hydropower schemes, adaptation of powerhouses, and a dam heightening were implemented with a cumulative effective capacity of all reservoirs being 1195 Mm3, corresponding to 21% of the annual mean flow of the Rh^ one at Porte-du-Scex (Meile et al. 2006). Hydroelectric production in the Valais is 10 billion KWh/year of which 1.5 billion is produced in the Swiss Upper Rh^ one. French production of electricity was 542.3 TWh in 2003, 78% (420 TWh) of which were produced by nuclear power, 12% (64 TWh) by hydropower, and 10% (54 TWh) by thermal means. The Rh^ one-Mediterranean watershed produced 25% of this electricity, and >50% of hydropower potential occurs in the Rh^ one catch-

PART | I Rivers of Europe

ment. In the French Rh^one (excluding the littoral area), the mean annual production of electricity is 128 412 GWh, 16 TWh (3%) of which is from hydropower. The four nuclear power plants on the Rh^one produce 22% of the French nuclear electricity (93 TWh/year). The Rh^one-Sa^one corridor is a main axis for navigation (517 km long). Since the Gallo-Roman period, the Rh^ one has been used to transport various goods and materials (metal, wood, fabrics, and cereal). This large way is connected by smaller canals to the Rhine River (‘Canal du Rh^ one au Rhin’), the Moselle River (‘Petite Sa^one’), the Seine River (‘Canal du Centre’), the Yonne River (‘Canal de Bourgogne’), and the Marne River (‘Canal de la Marne a la Sa^one’), and the Garonne basin via the ‘Canal du Rh^ one a Sete’. The transport capacity of the Rh^one downstream of Lyon is 22 Mt/year, most of it being local and made of bulk goods such as oil and gravels. Container transport is increasing rapidly. In 2005, 58 807 TEU (20-feet Equivalent Unit) were transported on the Rh^one River, 20% greater than in 2004. Rough minerals, agricultural products, oil products and fuel represented 41%, 14%, 13% and 7%, respectively, of transported goods. One of the most important transport centres is Port Edouard Herriot at Lyon with interconnected railroads, roads and navigation. The amount of transport is 10 Mt/year, 935 000 tons transported by ships. The Rh^one River catchment is an important reserve for groundwater. Over 200 Mm3/year taken in the alluvial aquifer is used as drinking water for three million inhabitants.

7.6.2. Flood Control Large floods in the Valais were relatively frequent in the past (1640, 1740, 1778, 1846, 1860), most often between August and October. Damages were often extreme, and led to the first correction of the Swiss Upper Rh^one (1863–1894). Its success created more industrial and economic developments in the Valais. After two large floods in 1930 and 1960, a second correction was completed using large amounts of bed material to build dikes. In October 2000, the Rh^one flooded 1000 ha (980 m3/s at Branson), causing 306 Me in damage and initiating a third correction. The project will run for 30 years from Gletsch to Lake Leman and will cost 612 Me. The project aims include environmental needs, flood security, and socio-economical development such as agriculture, hydroelectricity production and tourism. The main goal is to widen the river, deepen the bed, and reinforce dikes wherever necessary. After World War II, economic development along the lower Rh^one valley was intense: hydroelectricity production, navigation and irrigation were promoted by the ‘Compagnie Nationale du Rh^one’ and lead to new farms, industries and towns along the river. Today, over 556 000 inhabitants in 310 towns live in the Rh^one floodplain. Three floods occurred in 2002 and 2003, with damages of 846 Me from the 2003 flood. In January 2004, the government introduced a ‘global strategy’ to prevent flooding of the Rh^one and its main

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Chapter | 7 The Rh^ one River Basin

tributaries. The main objectives are to limit extreme floods, to control future development in flood areas and to change land use to reduce flood damage. To mitigate flood peaks, 12 large flood expansion areas have been identified from Chautagne to Vallabregues, and the delta. Flood risk in the French Upper Rh^ one is already low because of several large overflowing areas. To reduce flood duration, 50% of existing dikes will be reinforced before 2015, especially between Beaucaire and Arles. In the delta, priority efforts will be made to improve water drainage into the sea to better protect the Camargue. Management policies will focus on a ‘protection plan for inundation risk’ for the Rh^one River and the main tributaries, on rehabilitation of flood expansion areas, on dike improvement, and better information on risk prevention and management.

7.6.3. Fishery Statistics on professional and amateur fisheries on the Rh^ one and Sa^ one are available since 1988 (http:// 195.167.226.100/peche/carnet.html) (Table 7.7). Fishermen are more numerous and fish catches higher in the lower Sa^ one than in other sections (29% of all amateurs and 38% of all professionals). For amateur fishermen, the mean annual fish biomass caught is 80 kg/year per licence. For professional fishermen, fish biomass caught is 1 ton/year per licence and each fisherman usually has several licences. The most important fishery (48%) is large cyprinids (breams, carp, roach, barbel, nase and chub). Small cyprinids (especially bleak) are an important fishery of professional fishermen in the Sa^ one and Doubs. Large cyprinids represent 44% of the fishery biomass in the French lower Rh^ one and 81% in the French Upper Rh^ one. Pike-perch and pike are carnivorous fishes with commercial interest. Pike-perch catches are important in

the Sa^one and French lower Rh^one. Pike populations are relatively abundant in the French Upper Rh^one and upper Sa^one but they are less common in the lower Sa^ one. The mean individual weight of caught fish (pikes) ranges between 2.1 and 2.5 kg. Trouts are caught by amateur fishermen in the French Upper Rh^one (average fish biomass is 1.1 kg). The Wels fishery increased significantly after 1994, especially in the lower Sa^one. This fish is also important in the lower Doubs and to a lesser extent in the Lower Rh^one. The Wels population has increased since 1990. Burbot is mainly caught by amateur fishermen in the French Upper Rh^one (73 kg/year, period 1988– 2001). In the delta and French lower Rh^one, shads, mullets and bass can constitute a large part of the fishery (14% in the lower Rh^one). The eel fishery also is important in the lower Rh^one and delta, but is low in the Sa^ one despite stocking efforts.

7.6.4. Conservation and Restoration Along the French Rh^one and its main tributaries, 86 areas have protection status at the regional, national or European level. Sites of community importance (Directive 92/43/ EEC) and Special Protection Areas (European Union directive on the Conservation of Wild Birds, 79/409/CEE) represent 22% of these protected areas (http://natura2000. environnement.gouv.fr/regions/idxreg.html). The area within the Natura 2000 network is 98 590 ha (1614 along the Ain River, 680 at the Rh^one-Ain confluence, 19 658 along the Sa^one River, 8455 along the Doubs River, 575 along the Isere River, 6047 along the Durance River, and 61 561 along the Rh^one River). Nine sites in the Natura 2000 network are on the French Rh^one River (FR8201771, FR8212004 Lake Bourget – Chautagne – Rh^one; FR8210058, Upper Rh^one islands; FR8201785,

TABLE 7.7 Mean estimated biomasses (kg/year) caught by amateur and professional fishermen in the Rh^ one River (French Upper Rh^ one (FURh), the French Lower Rh^ one (FLRh) and delta (DELT)), the Sa^ one (Upper Sa^ one (USao) and Lower Sa^ one (LSao)) (1988–2001) and the Doubs River (1997–2001) Fish categories

FURh Pr. F

Eel Other amphihyalins Large cyprinids Small cyprinids Carnivorous fishes Salmonids Catfish Others Total

FLRh Am. F.

Pr. F

DELT Am. F.

USao

LSao

Pr. F

Am. F.

Pr. F

Am. F.

Pr. F

Doubs Am. F.

Pr. F

Am. F.

5 – 9368 407 623 78 74 247

170 – 9652 133 1556 178 224 826

5308 3255 3668 264 1279 1 278 316

170 566 8694 1114 1620 9 581 992

6528 18 509 2385 0 477 0 112 114

145 7981 882 14 503 9 121 232

5 – 2221 1047 1055 0 374 662

65 – 4875 216 1340 2 206 2333

49 – 25 232 13 107 5710 7 3925 9300

115 – 7264 905 4163 5 2880 6273

34 – 7695 6150 1640 4 660 820

98 – 1906 222 765 1 1168 1531

10 802

12 739

14 369

13 746

28 125

9887

5364

9037

57 330

21 605

17 003

5691

Estimated values are calculated by using the declared biomasses and estimated biomasses caught by fishermen who did not return their capture forms (one considers that their fish efficiency was the same as that of fishermen declaring their captures). Eight groups of fish species have been selected. The ‘ other amphihyalins’ species group includes shads, bass, mullets, lampreys; the ‘ carnivorous fishes’ species contains largemouth bass, pike, perch and pikeperch; the ‘ others’ group contains, among others, burbot, black bullhead, stone loach and pumpkinseed.

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floodplain and waterbodies of Miribel-Jonage island; FR8201749, FR8212012 Platiere island; FR8212010, Printegrade; FR8201677, alluvial floodplain of the lower Rh^ one; FR9310019, Camargue). Except for the Isere and Ain Rivers, the main tributaries and the Rh^ one have areas of community importance. Four main tributaries have national natural reserves, the Sa^ one (‘La Truchere Ratenelle’), the Doubs (‘l0 ile du Girard’, ‘Lac du Remorey’, http://www.maisondelareserve.fr/), the Dr^ ome (‘Les Ramieres du Val de Dr^ ome, http://ramieres.val.drome. reserves-naturelles.org/), and the Ardeche (‘Reserve Naturelle Nationale des Gorges de l0 Ardeche’, http://www. gorgesdelardeche.fr/reserve-naturelle.php). The Camargue is a Special Protection Area with 358 bird species being recorded and 132 nesting regularly. There are 200 migratory species, including purple heron (Ardea purpurea), white stork (Ciconia ciconia), black stork (Ciconia nigra), and squacco heron (Ardeola ralloides). A Regional Natural Park was created in 1970, allowing tourism, environmental protection, water resource management and the agricultural and economical development of local populations. Three main areas are usually distinguished: (1) the ‘Upper Camargue’ north of the ‘Etang de Vaccares’ is a fluvial area with freshwater ponds, (2) the ‘Middle Camargue’ around the ‘Etang de Vaccares’ where soft salt soils are used for agriculture (rice, corn, maize) and livestock grazing, and (3) the ‘Lower Camargue’ of marine – lagoon origin with a zone of salt ponds used for salt production (Salin de Giraud). Strictly protected areas in Camargue (private and public) cover 21 700 ha, the National Natural Reserve (13 117 ha, http://www.reserve-camargue.org/) is one of the most important. Its biodiversity includes 513 plant species, 50 Mollusca species, eight amphibian species (Mediterranean tree frog (H. meridionalis), western spadefoot (P. cultripes)), 14 reptile species (European pond turtle (E. orbicularis), southern smooth snake (Coronella girondica)), and 34 mammalian species (Kuhl’s pipistrelle (Pipistrellus kuhli). The reserve is a Biogenetic Reserve for Europe. Two other National Natural Reserves exist along the Rh^ one, the ‘Marais de Lavours’ (http://www.reserve-lavours.com/) and ‘l0 Ile de la Platiere’ (http://www.ile.platiere.reserves-naturelles.org/). The ‘Marais de Lavours’, created in 1984 with 474 ha, is an ancient peat swamp (alkaline peat of Carex lasiocarpa) connected during floods to the Rh^ one before regulation (Chautagne – Belley section). The arachno and entomofauna have been well studied: 185 spider species, 436 butterfly species, 120 Coleoptera species, 257 Diptera species and 41 dragonfly species were recorded. Among the 215 vertebrate species, 12 amphibian species (natterjack toad (Bufo calamita), agile frog (R. dalmatina), pool frog (R. lessonae), common tree frog (H. arborea), and yellow-bellied toad (B. variegata)), 4 reptiles species (Aesculapian snake (Elaphe longissima)), and 207 bird species (Eurasian curlew (Numenius arquata) and bluethroat (Luscinia svecica)) were found. ‘L’Ile de la Platiere’ reserve is located 50 km downstream of Lyon in the ‘Peage-de-Roussillon’ by-pass sec-

PART | I Rivers of Europe

tion and covers 484 ha. About 64 Mollusca species, 669 Coleoptera species (Lucanus cervus), 43 dragonfly species (Coenagrion mercuriale), 165 butterfly species (63 diurnal species, 102 nocturnal species), and 280 vertebrate species were recorded. Among the vertebrates are 4 amphibians, 6 reptiles (dark green snake (C. viridiflavus)), 215 bird species (70 nesting) and 36 mammals. Over 700 plant species were identified, including trees (83 species), aquatic plants (35 species) and herbaceous plants. These two national reserves are also Special Protection Areas for birds. A Regional Natural Reserve comprising an alder (A. glutinosa) ash (F. excelsior) forest (Alno-Padion, Alnion incanae, Salicion albae) was created in 1988 on the French Upper Rh^one (‘Iles du Haut-Rh^one’, 226 ha).

7.6.5. Restoration Activities and Potential The initial corrections of the Swiss upper Rh^ one have greatly altered the ecological value of the floodplain, whereas the last correction, although questionable because of hydroelectrical production, aims to rehabilitate alluvial habitats and biodiversity. From 1999 to 2001, a large alluvial area (100 ha) was rehabilitated just downstream of Geneva: ‘les Teppes de Verbois’ (http://etat.geneve.ch/dt/ site/protection-nature/master-content.jsp?componentId= kmelia274&nodeId=2007) and is now protected at local and international scales (Ramsar Convention). In 1998, a large restoration program was developed for the French Rh^one to (1) increase minimum flow rates in 8 by-pass sections (Chautagne, Belley, Bregnier-Cordon, Miribel-Jonage, Pierre-Benite, Peage-de-Roussillon, Montelimar and Donzere-Mondragon), (2) rehabilitate connections with secondary channels and backwaters, and (3) restore migratory pathways for large migratory fishes (eel and twaite shad). Presently, the minimum flow has been increased at Chautagne (2004), Belley (2005), Bregnier-Cordon (2006) and Pierre-Benite (2000), and 23 side-arms being restored in the French upper Rh^one (Photo 7.3) and 3 at Pierre-Benite. Cooperation between water managers, scientists and stakeholders led to the development of scientific surveys to evaluate the success of restoration. It involves collection and management of data, the development of new protocols for pre and post-restoration assessments, the development of predictive models of the effects of restoration, and the analysis of pre and post-restoration data, and evaluating postrestoration responses (Lamouroux et al. 1999, 2007). For fish, expected effects of the increase in minimum flow are an increase in ‘midstream’ species that prefer fast-flowing and deep microhabitats (barbel, nase, bleak, schneider, dace and grayling). In the Pierre-Benite restored section in 2000, the proportion of these species already doubled five years after minimum flow increase. River side-channels follow ecological succession that over time (decades) leads to terrestrialization (Bravard et al. 1986a). Under natural conditions, fluvial dynamics

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Chapter | 7 The Rh^ one River Basin

compensate for this succession to terrestrialization by creating new side-channels (Amoros et al. 1987a). The Rh^one River corrections reduced the fluvial dynamics of the river and increased the sedimentation in backwaters that increased the rate of succession (Bravard et al. 1986a). The Rh^ one was also impacted during the 20th century by hydroelectric projects. Consequently, the restoration of sidechannels concerns both natural processes (succession and alluvial deposition) and human impacts (embankments and hydroelectric production). Regardless, rehabilitation targets must be defined according to the present environmental conditions and incorporate realistic strategies. For instance, some environmental alterations such as changes in water quality and flow regime caused by human activities appear irreversible, especially in large rivers, limiting potential restoration options. The guiding principle for defining rehabilitation targets was to improve habitat diversity, thereby increasing biodiversity to previous successional stages (Amoros 2001). Two distinct approaches were used in the Rh^ one system (1) flood pulsing as a disturbance to increase habitat diversity, reduce competitive exclusion, and reset ecological successions, and (2) use of groundwater to enhance habitat diversity and biodiversity. For example, the bed of three side-channels at Pierre-Benite was excavated, sediments were removed in 1999, and the minimum discharge was increased in 2000. Further, two side-channels were designed to be flood scoured, one having an additional supply of groundwater and the other being connected to the river at both ends. The third side-channel was designed to have river backflow through a downstream connection. A 5-year monitoring program showed that the number of aquatic plant species remained 8–12 in the control side-channel, whereas it increased in the three rehabilitated channels, being highest (21–23 species) in the flood-scoured and groundwater-supplied channel (Amoros et al. 2005). The number of species unique to one side-channel (downstream connexion) was 35% of the total species number in the bi-connected channel (downstream and upstream connexion), 29% in the groundwater-supplied channel, and 9% in the back-flow channel.

7.6.6. EU Water Framework Directive Seven groundwater aquifers and 26 surface waterbodies were defined along the French Rh^ one (http://195.167. 226.100/DCE/RM/RM_etat-des-lieux.htm). Among the surface waterbodies, 19 were classified as heavily modified (85% of the river) and one was unclassified (the Chautagne by-passed section). Among the remaining waterbodies, 2 were between Bregnier-Cordon and Jons (Cusset hydroelectric scheme), 2 were bypass sections on the upper Rh^one (Belley and Bregnier-Cordon), and the others were bypass sections on the lower Rh^ one (Peage-de-Roussillon and Donzere-Mondragon). Two waterbodies were identified as having a risk of failing to meet the WFD objectives (i.e. to

reach a ‘good surface water status’ by 2015): the section between the Swiss border and Seyssel dam and the river stretch between the Sa^one and Isere confluences. For the other waterbodies, there was doubt concerning the risk of failing to meet the WFD objectives. At the watershed scale, 552 ‘running water’ waterbodies were described (61% of all waterbodies); 161 waterbodies were identified as heavily modified, 116 had a great risk of failing to meet the WFD objectives, and 204 had a chance to reach the objectives. For other waterbodies, available information was not sufficient to evaluate their ability to reach WFD status by 2015. In 2003, 20 surface waterbodies reached good status for classical physico-chemical parameters and all waterbodies will probably reach this status by 2015. For micropollutants such as pesticides and metals, only 30–50% of the surface waterbodies reached good status in 2003, and no waterbody reached good status for organic pollutants, especially polycyclic aromatic hydrocarbons (DIREN 2005). The biological status is difficult to evaluate for each waterbody because of the paucity of information. As the Water Framework Directive objectives are very ambitious, success of its implementation will depend on the efficiency to solve critical issues such as the management of water pollution (nitrates, pesticides), river restoration, hydroelectricity production, and navigation. For large rivers such as the Sa^one and Rh^ one, pristine biological references are lacking and objectives must be defined for each waterbody. Camargue comprises 10 transitional waterbodies, including the two arms of the Rh^one, the littoral and 7 lagoons. Only one waterbody would potentially reach a good ecological status by 2015. The Vaccares and ‘Salins d’Aigues Mortes’ ponds have a high risk of failing to meet WFD objectives by 2015. For the other waterbodies, there is doubt whether they will reach a good ecological status by 2015, because their hydromorphological functioning is highly disturbed.

7.7. THE AIN RIVER 7.7.1. Geomorphology The Ain is 200 km long and drains 3713 km2 in the Jura Mountains (Photo 7.5). Its main tributary is the Bienne River. The Jura Mountains are composed of eastern sedimentary folds (1600 m asl) and western low plateaus (500– 1200 m asl) sloping to the west. This well-watered and forested range has karstic features due to the predominance of Jurassic limestone. It was affected by Quaternary glaciations that layed thick till deposits. Local erosion of till provides most of the sediment from clay to boulders entering into the Ain network. The coupling of slope and fluvial processes generates a steep gravel-bed river. The channel of the Ain is confined inside gorges along most of its length, and a chain of four hydroelectric dams were built from 1930 to 1970. Downstream of the gorges, the Ain wanders almost freely for 40 km, except where bridges constrict the channel. Erosion of fluvio-glacial deposits from the W€ urm Ice

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PART | I Rivers of Europe

PHOTO 7.5 The Lower Ain River (Photo: J.M. Olivier).

Age provides most coarse sediments to the river. Sidechannels from the ancient braided belt and more recent meanders, as well as a recently developed alluvial forest, contribute to the rich biodiversity of the river corridor. However, the river can no longer cut off meanders and create new palaeo-channels. Further, bed incision (2 m in the last 30 years) has lowered the groundwater level causing a loss of riverine wetlands.

7.7.2. Hydrology and Temperature The Ain catchment has an oceanic hydrologic regime, despite altitude, because it is highly influenced by rainfall (Table 7.3). The isotherm of 0 C is at 1000–1200 m a.s.l. The annual mean discharge is 132 m3/s. Strong daily fluctuations (>100 m3/s) usually occur downstream of the reservoirs due to hydroelectricity production. Even in March, the month of maximum discharge, snowmelt only contributes 30% of discharge. Most floods occur between October and March, when rainfalls and snowmelt are combined. The Ain discharge during floods can reach one River at its conflu2400 m3/s and exceeds that the Rh^ ence with the Ain River.

7.7.3. Biogeochemistry Water of the Ain is quite hard due to the predominance of limestone, whereas sulphate concentration is low. The sediment load of the Ain has never been monitored. In the 1950s, most of the bedload in the Rh^ one at Lyon (30 000 m3/year)

originated from the Ain,. The chain of hydro-dams built along the Ain trapped sediments and most of the suspended load. Today, most sediment transfer to the Rh^one is from bank and bed erosion in the 40 km long downstream reach. The Ain catchment is dominated by extensive agricultural practices (breeding, meadows and forests) with some local viticulture and cheese production in the Jura Mountains. The lower valley is characterized by intensive farming. The main industrial pollutants are from mechanical factories, surface treatments, cheese processing, plastics and sawmills. Most industries are concentrated along the lower part of the Ain River including the ‘Plaine de l’Ain’ (confluence with the Rh^one), the ‘Plastics Valley’ (city of Oyonnax), the city of Morez with its eyeglass industry, and the city of Saint-Claude well-known for traditional hand-crafted pipes. Water quality problems are linked to toxic pollutants including pesticides in the Ain and some tributaries and metal and organic micro-pollutants in tributaries such as the Ange River and Oignin River (Oyonnax).

7.7.4. Aquatic and Riparian Biodiversity The cut-off channels of the Ain have high species richness and many rare macrophytes. Aquatic plant communities in cut-off channels are adapted to flood disturbances (mainly ruderal, small-sized species, for example C. platycarpa, Potamogeton pusillus, P. natans, S. emersum), and oligotrophic (C. major, P. coloratus) or mesotrophic waters. The Ain is highly dynamic and surface water and groundwater nutrient content is intermediate and low, respectively. A large alluvial forest develops along the lower 40 km of the river where the floodplain widens. The riparian forest is

Chapter | 7 The Rh^ one River Basin

mainly composed of hard wood species such as F. excelsior, F. angustifolia, U. minor, T. cordata and Ailanthus glandulosa. Coarse and permeable sediments favour the establishment of communities dominated by P. nigra, S. eleagnos, Acer platanoides, Viburnum lantana, Cornus sanguinea, Ligustrum vulgare and mesophilous species such as Q. pubescens and Robinia pseudacacia. The alteration of the river hydrology by anthropogenic activities (lateral embankments, dam construction) associated with natural processes (incision) have lowered the water table by 1 m, and pioneer communities have been progressively replaced by more terrestrial-like species (Marston et al. 1995). Data for aquatic invertebrates are mainly available for the alluvial floodplain of the lower Ain where habitat diversity is high (Berahou 1993; Cogerino 1989). The most representative limnophilic taxa are Helobdella stagnalis, Erpobdella octoculata (Hirudinea), Galba corvus (Mollusca), Leptophlebia marginata, Habroleptoides modesta (Ephemeroptera), Taeniopteryx schoenemundi (Plecoptera), Aeschnidae (Odonata), Callicorixa praeusta, Micronecta sp. (Heteroptera), Athripsodes sp., Mystacides azurea, Setodes argentipunctellus, and Oxyethira distinctella (Trichoptera). The most abundant rheophilic taxa are B. lutheri, B. rhodani, Ecdyonurus venosus (Ephemeroptera), Chloroperlidae, Siphonoperla torrentium (Plecoptera), Esolus parallelepipedus, Elmis aeana, E. maugetii (Coleoptera), Rhithrogena semicolorata, Rhyacophila dorsalis, Hydropsyche incognita, C. lepida (Trichoptera), and Wilhelmia equina (Diptera). Among the main tributaries of the French Rh^ one River (Arve, Guiers, Ain, Sa^ one, Isere, Eyrieux, Dr^ ome, Ardeche, Durance, Gard), Berahou (1993) considered the lower Ain as one of the most lotic. Among the macroinvertebrates collected in these tributaries, five rheophilic taxa are exclusive to the Ain (Orectochilus villosus, Riolus subviolaceus (Coleoptera), Agraylea sp., Hydropsyche contubernalis and Setodes argentipunctellus (Trichoptera)). The side-arms of the lower Ain harbour 36 species of Trichoptera, 94 species of Coleoptera, 10 species of Odonata, 12 species of Ephemeroptera, and 6 species of Crustacea (including the stygobiotic amphipods Niphargus kochianus and Niphargopsis casparyi). The composition of Coleoptera reflected successions within side-arms (Castella 1987). Elmidae were dominant in lotic side-arms but were progressively replaced by Dysticidae and Haliplidae in paleochannels with strong groundwater input. Leger (1926) recorded 18 fish species from the Bienne confluence (the major tributary of the Ain) to the Rh^one confluence. The dominant species were nase, brown trout, grayling, chub and bream. Brook lamprey, eel, twaite shad, barbel, gudgeon, blageon, schneider, carp, stone loach, pike, and bullhead, perch and ruffe were present in lower densities. Minnow inhabited small tributaries and was probably also present in the Ain. Apron was not recorded by Leger (1926) but it occurred in the Ain and Bienne. The upper course of the Ain offered impressive lotic sections suitable for brown trout. The main alteration of the river by large dams occurred from 1901 (Sault-Mortier) to 1968 (Vouglans). The canyon

279

was transformed into a succession of several reservoirs with favorable conditions for limnophilic species. Presently, the Ain can be divided in three parts: the upper section from the headwaters to the large dam of Vouglans, including the first large dam at Blye (48 km from the spring); the intermediate section fragmented by a succession of 5 large dams; and the lower Ain downstream from the last dam (Allement) to its confluence with the Rh^one. In the upper section, the river has been fragmented by watermills built to produce energy for small factories and five low dams. The impact of these dams on fish populations has not been studied. Eighteen species occur in this section. They are mainly rheophilic species (stone loach, bullhead, schneider, barbel, soiffe, blageon, gudgeon, dace, minnow, trout and grayling) although limnophilic species such as tench, rudd, and black bullhead also occur. Other native (bleak, roach, pike, perch, and chub) and non-native species (carp and pumpkinseed) are also present. Vouglans is the largest reservoir along the river. Among the 25 species present in the reservoir, 9 are non-native and several of them were introduced for angling (pike-perch, brook trout, lake char – Salvelinus namaycush – and wels). The following reservoirs downstream hold a limnophilic community. The lower Ain is a large floodplain with meanders and several side-arms and backwaters often fed by groundwater. Thirty-one species belonging to 12 families occur in the lower floodplain. Rheophilic species (trout, dace, nase, barbel, schneider, minnow, stone loach, and blageon) dominate, and the grayling population is the most important one in the Rh^one catchment. Apron, burbot and eel are very rare. Potamophilic (bream, pike, and carp) and limnophilic species (tench and rudd) maintain small populations because of the presence of lentic side-arms and backwaters (Mallet 1999). Soiffe is absent although a large natural population is present upstream in the Suran River, a tributary flowing from Jura. Six of the 31 species are non-native. Hydrology and water temperature depend on hydropeaking. Minimum instream flows increases water temperature during summer, stressing the most sensitive species such as grayling. Among the three species of Urodela present along the Ain, the fire salamander and palmate newt are the most common species whereas the alpine newt is present only in the lower river. Eight species of Anoura occur along the river. The common toad and midwife toad are well distributed along the river, whereas the natterjack toad occurs in a few spots within the valley. The southern species, Pelodytes punctatus (Parsley frog), inhabits mainly the lower Ain, and could be present upstream whereas agile and marsh frogs occur only downstream of Vouglans dam. Only the European grass snake inhabits the Upper Ain valley. This species cooccurs with dark green snake in the lower Ain. The European pond terrapin is probably present. The bird community of the Ain is composed of common species with stable populations such as mallard or Eurasian coot. Other populations such as grey heron or little ringed

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plover (Charadrius dubius) are increasing as the number of sand and gravel pits increase. Hen harrier populations (Circus cyaneus) have been declining in the whole Rh^oneAlpes} region since the 1970s, but this species is still nesting in a few places in the lower Ain floodplain. Gadwal nested in three places in 1977 and is still nesting today in a few places. Four species of falcon inhabit side-arms and backwaters of the floodplain: Eurasian hobby (Falco subbuteo), rock kestrel (Falco tinnunculus), merlin (Falco columbarius) and peregrine falcon (Falco peregrinus). Most records of mammals are in the lower Ain including European otter, European beaver, Southwestern water vole and Eurasian water shrew populations. Muskrat and coypu populations are probably limited to the lower Ain.

7.7.5. Management and Conservation Mean annual hydroelectricity production along the Ain is about 750 GWh. Tourism is well developed along the river and Vouglans reservoir (canoe-kayak, angling, swimming). About 27 000 and 9000 persons/year practice nautic sports in the Ain and Vouglans reservoir, respectively. The Upper River and lower valley are famous for trout and grayling angling, respectively. Because of the good water quality, recreation activities are very intense in the lower Ain during summer and recent attempts aim to regulate tourism activities. Groundwater resource management is an important issue in the lower Ain floodplain because agriculture mainly depends on groundwater supply. The ‘Lower Ain floodplain management program’ aims to stabilize the amount of pumped groundwater in the future. The lower Ain is considered as a highly important floodplain. The water quality is very good and this running part of the river offers suitable habitats for sensitive species such as grayling. Further, although the discharge regime is influenced by hydroelectricity production, the lower valley remains dynamic. Unfortunately, recent bed incision reduced the meandering potential of the river and caused drying of several backwaters. River bed armouring is progressing at 500 m/year. In 2002, a Life program (Conservation of habitats created by the Ain River dynamic, http://www.bassevalleedelain.com/life/fr/index.php) was approved by the European Community and two contiguous sites (2294 hectares) were included in the Natura 2000 network (FR8201653 and FR8201645). Five backwaters were rehabilitated (2.6 km) to stop the drying process and increase wetted areas, resulting in 20 new macrophyte species such as L. natans. In order to favour the development of alluvial forests and especially pioneer species, 1500 ha will be protected against human activities. A special management program including 40 communes and covering 602 km2, 53 km of the lower Ain and 18 tributaries, was set up in 2006. The main objectives of the program are: to restore the fluvial dynamics of the Ain; to improve discharge management; to improve flood risk management; to protect groundwater resources; to increase water quality; to preserve river and

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backwater biodiversity; to restore the fish community; to manage tourism; and to evaluate the efficiency of the program. Among the 10 waterbodies identified along the Ain, only 3 are not classified as heavily modified: the most upstream section from the first large dam (Blye), the river part between Blye dam and Vouglans reservoir, and the lower part downstream of the last power station. Four waterbodies are reservoirs. The first upstream waterbody is the only one having a great probability to meet the WFD objectives (good status) and a reference site was selected in this section (Champagnole, Jura). For all other waterbodies, the probability of meeting the WFD objectives is low.

ˆ NE RIVER 7.8. THE SAO 7.8.1. Geomorphology The Sa^one River drains an Eocene-Oligocene, north–south graben filled in the early Tertiary. Between 1.8 and 3 Ma BP, the Bresse Marl Complex was made of fluvial gravels from the Aar and Doubs rivers and marl deposits in lacustrine areas. Between 1.2 and 1.7 Ma BP, overlaying sediments came from the surrounding plateaus. During the Quaternary, flowing southward and shifting to the west, the Sa^one incised its valley through uplifting sedimentary fill. The tectonic warping was complex since the middle of the river flowed across subsiding areas, while the lower river evolved to the uplift of the Lyon area and incised a narrow valley through metamorphic rocks of the eastern Massif Central. For instance, 40 km from its confluence with the Rh^one, the Sa^ one Wurmian gravel deposits are 10 m lower than those of the Rh^one in Lyon (relative subsidence: 0.2–0.4 mm/year). The active tectonic explains the low gradient of the Sa^one, which is 0.068 m/km between the Doubs and Azergues rivers (132 km). The steepest gradient downstream of this reach (0.17 m/km) is probably due to bedload inputs from the Azergues River (about 30 km upstream from Lyon) during the late Holocene. The floodplain of the Sa^one, prone to long-lasting floods, was protected by low levees constructed between 1843 and 1895. About 17 000 ha of agricultural lands are now protected except from 1 to 6 year summer floods which sustain floodplain meadows.

7.8.2. Hydrology and Temperature The Sa^one has an annual mean discharge of 445 m3/s at Lyon (period: 1920–2001) (Table 7.3). The specific discharge is 14.8 L/km2/s, and the river has a typical rain regime (oceanic type) with high winter flows and floods (rainfall) and low summer flows (evapotranspiration). The spring flow from the Doubs tributary is increased by snowmelt from the Vosges and Jura Mountains. The 100-year flood (3180 m3/ s at Lyon) is modest but its duration can be >30 days in the middle river. Discharge of historic floods was much higher, reaching 4300 m3/s for the 1840s flood.

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7.8.3. Biogeochemistry

7.8.4. Aquatic and Riparian Biodiversity

Except for restricted northern headwaters on granitic sandstone of the Vosges mountains, the river drains natural mineralized waters from limestone bedrock and received water inputs from the Doubs River that flows over large karstic areas. Chemical industrial inputs from Solvay (Tavaux, Jura) increase mineralization (chlorides) and a strong agricultural pressure contributes to high levels of nitrates (Figure 7.6). The Sa^ one is a large slow-flowing floodplain river that contrasts with the alpine character of the Rh^ one. The river flow is slowed even more because of navigation control. Most tributaries have a lentic character as well and water in the catchment is highly eutrophic. The catchment mainly comprises agricultural landscapes with strong pressures from farming, and intensive culture and viticulture activities causing diffuse pollution by nutrients and pesticides. Several cities located along tributaries such as Dijon (Ouche River), Besan¸con (Doubs River) and Belfort and Montbeliard (Doubs River basin) are sources of urban and industrial pollutants. The Doubs catchment contains traditional milk and cheese production on the plateaus, and also auto manufacturing and surface treatment facilities that release various micropollutants. Tributaries from the Burgundy and Beaujolais wine producing areas add organic pollutants and pesticides, as well as urban and industrial pollutants. Tributaries in the eastern catchment have cumulative impacts from nutrients and pesticides linked to viticulture and intensive agriculture (corn). The upper Sa^ one has high loads of nickel and arsenic. The sediment load in the Sa^ one is impacted by gravel and sand removal as well as by flow reduction from dams that also trap sediments from tributaries. As such, the Sa^one essentially carries suspended sediments that are deposited on the alluvial plain during floods. Astrade (2005) reported a suspended load of 50 mg/L over 10 days during the January 1995 flood (1585 m3/s). A concentration peak (70 mg/L) in suspended sediment occurred at bankfull discharge. In comparison, the Rh^ one at Arles can transport >2500 mg/L during floods in a similar time period.

Phytoplankton are sparse in the Sa^one with only 24 species being recorded (e.g. 66 species are found in the Loire River). The most common taxa were Diatomophyceae, Cyanophyceae and Chlorophytae. In 1998, the average cell abundance was 13 200 cells/L and chlorophyll-a concentration was 4 mg/L. In summer, algae concentration can reach 567 000 cells/L and chlorophyll-a concentration 69.5 mg/ L. These are relatively low values compared to the Loire River where average algae concentration is 40 106 cells/ L and chlorophyll-a concentration ranges between 100 and 200 mg/L. Zooplankton numbers are also low with a deficiency in Rotifera (14 species). Planktonic Crustacea are dominated by Copepoda (80% of the community), and Claodocera are mainly represented by Daphnia, Diaphanosomas and Bosmina (Fruget and Persat 2000). In the main channel, 67 macrophyte taxa were recorded (22 submerged species, 28 species with floating leaves, 16 emergent species, and 15 filamentous algal species). Bornette et al. (2001) found 66 species of which 12% were absent in the Doubs, Rh^one and Ain rivers. Eutrophic species such as C. demersum, S. polyrhiza and L. minor are highly abundant as well as species intolerant to floods (N. lutea and N. alba). Other species such as S. aloides, Valisneria spiralis, Potamogeton nodosus and M. spicatum are also common. E. Canadensis, Potamogeton lucens, P. perfoliatus and S. sagittifolia occur in a few backwaters. The most common helophytes are tolerant to high nutrient levels and prefer undisturbed wetlands (Glyceria maxima, Rumex hydrolapathum, Acorus calamus and P. australis). Rare species such as Trapa natans, Hydrocharis morsus ranae, and Butomus umbellatus occur in the river. Cut-off channels along the river are mostly eutrophic with little influence by floods. They are consequently dominated by the same tall, competitive eutrophic species (Godreau et al. 1999). Because of its hydrology and fertile soils, the floodplain has been used for agriculture since the Middle Age. Presently, there are many poplar plantations. Two natural sections include: (1) fragments of alluvial forests upstream from Ch^alon-sur-Sa^one where F. angustifolia reaches its northern limit and occurs with A. glutinosa and Salix alba; and (2) small and fragmented hard wood forests downstream from Ch^alon-sur-Sa^one, composed of Q. robur, F. angustifolia, F. excelsior, Ulmus laevis, U. minor, A. glutinosa, and Salix alba. These residual forests are endangered by development of poplar plantations and agriculture. U. laevis is mainly present along the Sa^one in the Rh^one catchment. The Sa^one is characterized by typical limnophilic macroinvertebrate species. From the spring to the confluence with the Doubs River, communities are dominated by burrowing and pollution intolerant species such as Pisidium supinum (Mollusca), Ephemera lineata, Ephoron virgo, C. luctuosa (Ephemeroptera), whereas epibenthic and pollution tolerant species are abundant downstream (Helobdella stagnalis, Herpobdella octoculata, Glossiphonia complanata (Hirudinea),

FIGURE 7.6 Long-term change of the nitrate concentration (mg/L) in the Sa^ one at Auxonne (C^ote d0 Or). Source: Data from Agence de l0 Eau Rh^one-Mediterranee-Corse.

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Asellus aquaticus (Crustacea)) (Tachet et al. 1988). A recent study of the lower Sa^ one upstream from Lyon showed that half of recorded taxa were alien species: Chelicorophium curvispinum, Dikerogammarus villosus, A. desmarestii (Crustacea), D. polymorpha and Corbicula fluminea (Mollusca), Pectinatella magnifica (Bryozoa), Hypania invalida (Polychaeta), and Dugesia tigrina (Planaria) (Persat and Fruget 2007). Except for Oligochaeta and Chironomidae, common native species are potamolentic species such as E. tenellus (Trichoptera) and C. luctuosa (Ephemeroptera). The abundance of non-native species probably explains the rarity of burrowing species such as E. lineata and E. virgo (Ephemeroptera) or G. fossarum and Asellus aquaticus (Crustacea), and the recent decline of Gastropoda. Over 40 Odonata species were recorded in cut-off channels of the Sa^ one River (Godreau et al. 1999), some quite common (Ischnura elegans, Platycnemis pennipes and Coenagrion puella) and others specific to particular habitats (C. mercuriale and Gomphus pulchellus). Both C. mercuriale and O. curtisii have threatened status in Europe and Cordulegaster bidentata is restricted to France. Mollusca received a particular attention because of their high abundance in the Sa^ one. Annual surveys (1996– 2004) at five sites along the Sa^ one (116, 194, 225, 332 and 472 km downstream from the source) and two sites on two tributaries (Ognon and Doubs) identified 24 species (14 Gastropoda, 10 Bivalvia). Nearly 60% of the total density was represented by three species: Valvata piscinalis, Pisidium subtruncatum and Corbicula fluminea. Other important species were the gastropods P. antipodarum, Gyraulus albus and Bithynia tentaculata, and the bivalve Sphaeriidae Musculium lacustre, Pisidium nitidum, P. casertanum, P. amnicum and P. moitessierianum. The longitudinal gradient in aquatic insects along the Doubs and 11 tributaries was described by Verneaux et al. (2003). Species in upstream springs, brooks and karstic outlets included Rhadicoleptus spinifer, Drusus annulatus, Agapetus fuscipes (Trichoptera), N. pictetii, Nemoura cinerea, and N. cambrica (Plecoptera). In the middle and lower sections (Doubs, Loue) were E. lineata, E. virgo, P. luteus, and Caenis horaria (Ephemeroptera), and E. tenellus, A. multipunctata, and Leptocerus tineiformis (Trichoptera). Fruget et al. (1996) examined macroinvertebrate communities in the main channel and backwaters of the Doubs River and RhineRh^ one Freycinet canal that connects the Rhine to the Sa^one. High richness (149 taxa) was related to the habitat diversity. Dominant taxa were Chironomidae and Oligochaeta. Other common taxa included Trichoptera (27 species), Mollusca (22 species), Coleoptera (18 species) and Ephemeroptera (17 species). Plecoptera (Leuctra sp.), Trichoptera (Hydropsyche siltalai, H. incognita, H. exocellata, H. contubernalis, C. lepida, Psychomia pusilla, and Rhyacophila spp.), Ephemeroptera (B. fuscatus, S. ignita, and Potamanthus lutheus), Coleoptera (E. parallelepipedus and Elmis maugetti) and Diptera (Simulium spp.) were common in lotic stretches. Lentic species (L. tineiformis, C. dipterum, Caenis sp., Caenis robusta, the Odonata Coenagrionidae, Ancylus fluviatilis,

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Physa acuta) were found in backwaters and canals. Leutridae, Rhyacophila spp., and Baetis spp. were associated with the bryophyte Fontinalis upstream of the confluence with the Allan River. Originally, at the beginning of the 20th century, the fish fauna was composed of 30 native species, including twaite shad and sea lamprey (mainly in May during migration) that are no longer able to migrate. River lamprey was not recorded by Leger (1945), but it probably migrated in the Sa^one in the 19th century. Apron was present in the Loue and Doubs rivers. Nine-spined stickleback (Pungitus pungitus) and probably ruffe were native in the Sa^one basin. The upper 13 km of the river was the trout zone, the following 93 km the barbel zone, and the last 366 km the bream zone (Leger 1945). In the last 70 km before Lyon, Leger (1945) found 14 abundant species (bleak, roach, bream, nase, chub, carp, tench, gudgeon, perch, pike, eel, burbot, black bullhead and pumpkinseed), 4 common species (dace, soiffe, barbel and rudd) and 10 less common species (brown trout, ruffe, pike-perch, large-mouth bass, minnow, bullhead, threespined stickleback, stone loach, bitterling and brook lamprey). The Sa^one is usually divided into the upper Sa^one from the source to the Doubs confluence (315 km) and the downstream lower Sa^one (157 km). Thirty-eight species occur in the upper Sa^one and 10 are non-native. Apron is present in the Lanterne and Ognon rivers. Cyprinids are well represented in the Sa^one. Rheophilic fishes such as bullhead and trout are rare and grayling is absent. In the Doubs, 35 fish species are known, and nine-spined stickleback is absent. The brown trout is widely distributed in the Doubs, and grayling occur in the upper Doubs near the French-Swiss border and in the tributaries Dessoubre and upper Loue. The lower Doubs has a typical potamic ichthyofauna such as roach, bleak, bream and silver bream, chub, wels, perch, but also rheophilic species such as dace, schneider, soiffe, nase, barbel, minnow and gudgeon (Fruget et al. 1998). Regularly, 38 species occur in the lower Sa^one and 12 are non-native. Brown trout, bullhead, and burbot are rare or absent. Dominant fishes are potamic and limnophilic species, including roach, chub, bleak, pumpkinseed, silver bream, rudd, gudgeon, perch, tench, topmouth gudgeon, bitterling, bream, carp and pike-perch. Large carp occur in the Sa^one. Pike are not abundant in the lower Sa^one because of the disappearance of submerged meadows used for reproduction. Wels is very abundant. Cut-off channels and sidearms provide suitable reproductive and nursery areas for phytophylic and litho-phytophilic fishes (Grenouillet et al. 2000, 2001). Five species of Urodela and eight species of Anoura occur in the Sa^one catchment. The common toad, midwife toad, common frog, fire salamander, palmate newt and alpine newt are common. The smooth newt is less abundant than the alpine newt and the great crested newt is relatively rare because of fish predation. The Sa^one floodplain provides suitable habitat for the common tree frog. The common toad

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and agile frog, which are abundant in southern France, are rare along the Sa^ one. The yellow-belled toad is only found in the upper Sa^ one valley; its absence downstream is probably due to the loss of flooded forests in the floodplain (Craney & Piston 1994). The dark green snake and European grass snake are present along the river. Several common birds occur in the Sa^ one valley, including grey heron, Eurasian reed-warbler, meadow pipit (Anthus pratensis), reed bunting (Emberiza schoeniclus), yellow wagtail (Motacilla flava) and northern lapwing (Vanellus vanellus). Other species such as the grasshopper warbler have stable populations. Eurasian curlew populations have increased over the last 10 years with 200–300 breeding pairs today. Corncrake (Crex crex) occurred everywhere in France except the south in the early 20th century, but the number decreased by >35% between 1984 and 1997 (Mayaud 1936). Presently, this species is found only in the Sa^ one valley (30–50 singing males were recorded in 2000). The situation was the same for the sedge warbler (Acrocephalus schoenobaenus). Whinchat (Saxicola rubetra) is rare in France but present in the Sa^one floodplain and is increasing in numbers. The marsh warbler shows the same pattern with an increase since 1990. In contrast, the little bittern has almost disappeared in the Sa^one floodplain. Several species of Ardeida are found on the |Ile de la Motte}, a Natura 2000 site in the lower Sa^ one, including black-crowned night heron, little egret and buff-blacked heron. A colony of 30–50 pairs of black-crowned night-heron established in this Natura 2000 site is of special importance because the species is decreasing in the Rh^ one-Alps region. The Sa^ one floodplain provides suitable habitats (feeding and resting areas) for overwintering migratory birds such as the great white egret (Egretta alba), white stork (Ciconia cico-

nia), osprey (Pandion haliaetus), and several waders such as the wood sandpiper (Tringa glareola). European beaver have been present in the S^aone floodplain since 1991, although few data exist. European otter are found in the lower Sa^one, and Eurasian water shrew, muskrat and coypu have been recorded all along the Sa^one.

7.8.5. Management and Conservation Hydroelectricity is mainly produced on the Doubs and Loue rivers (300 GWh/year). The Sa^one valley is an old axis of civilisation, being a natural link between the Mediterranean and lands in the north (Bravard et al. 2002a) (Photo 7.6). The Sa^one has been regulated for navigation since the 19th century, using low navigation dams upstream after 1841 and narrowing the channel downstream after 1845 (Astrade 2005). Although the navigation system was completed by 1882, transport was modest (400 000 tons/year) due to railway competition. Around 400 km of the Sa^one are navigable from Corre to Lyon. Only small ships (<400 tons) are able to navigate the ‘Petite Sa^one’ where 22 dams were built. Between 1958 and 1991, five navigation dams were built on the ‘Grande Sa^one’ and the riverbed was dredged to allow large barges up to 4400 tons. Four large commercial ports are present along the Sa^one: Pagny-Seurre (mean annual traffic: 244 000 tons), Ch^alon-sur-Sa^one (mean annual traffic: 903 000 tons), M^acon (mean annual traffic: 418 000 tons) and Villefranche-sur-Sa^one (mean annual traffic: 696 000 tons). The alluvial aquifer of the Sa^one is a large reserve for drinking water with 700 000 inhabitants currently using this resource. PHOTO 7.6 Sa^one River, 25 km upstream from Lyon (Photo: J.M. Olivier).

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Fishery is an important activity on the Sa^ one, mainly cyprinids, wels and pike-perch. Spinycheek crayfish (Orconestes limosus) is also harvested (367 kg/year in the upper and 4217 kg/year in the lower Sa^ one). The Sa^ one floodplain has been colonized by typical plants and animals with large areas covered by meadows or alluvial forests. From the source to the confluence with the Rh^ one River, four sites belong to the Natura 2000 network (FR4301342, Sa^ one Valley; FR 2612006, alluvial meadows and associated environments of Sa^ one-et-Loire; FR 2600976, floodable meadows and forests of the Sa^one valley between Ch^alon/Sa^ one and Tournus and the lower Grosne River; FR 8201632, wetted meadows and alluvial forest of the Sa^ one valley). These alluvial habitats are especially important for birds, for instance, as a nesting place for corn crake and a biotope for Eurasian curlew. The lower Doubs constitutes another Natura 2000 site (FR 4301323), providing several habitats for aquatic and terrestrial vegetation and animals (little ringed plover, stone curlew (Burhinus oedicnemus), European bee-eater, purple heron, and little bittern). The Sa^ one valley was heavily impacted in the past (toxic and agricultural pollution, sand and gravel extraction, navigation). Rehabilitation success of the Sa^ one River is dependent upon the improvement of water quality and ecological status of polluted tributaries. A large management program was developed for the catchment. A Life program (1997–2001, 1.32 Me) was launched in a floodplain area (72 000 ha) with the goal to harmonize agricultural practices, flood management and biodiversity conservation. Specific objectives were to: (1) increase compatibility between navigation and agriculture by improvement of navigation equipment; (2) restore floodplain functioning; (3) to protect groundwater resources by limiting N and P inputs; and (4) to set up a monitoring program to inform and educate local people. An experimental program (1998–2001) was developed on 6500 ha (six sites) in the floodplain, and included restoration and maintenance of floodgates, ditches and canals, access of spawning sites for phytophylic fish species (especially pike), management of the alluvial forest for native species, limiting bank erosion by using eco-engineering technology, and protection of groundwater quality and quantity. Shore protection against waves created by ships favoured vegetation development (V. spiralis, Najas spp.), microphytic and microbenthic species, and provided nursery places for fishes. Among nine waterbodies along the Sa^ one, only the last 40 km between Villefranche/Sa^ one and the Rh^ one confluence were classified as heavily modified. Indeed, water pollution in the lower river is high (mainly pesticides and metals, but also nutrients), and backwaters often were altered. The status between the Doubs confluence and Villefranche/Sa^ one (126 km) is still doubtful. Two waterbodies have a high risk of failing to meet the WFD objectives. The risk is low for only one waterbody and there is doubt concerning the other waterbodies. The upper three waterbodies are morphologically unaltered but water pollution by pesticides, metals and organic pollutants is high and diffuse. The

PART | I Rivers of Europe

high human use of the valley and river gives little hope that the river will reach good ecological status by 2015.

7.9. THE DURANCE RIVER 7.9.1. Geomorphology The Durance is an alpine Mediterranean river that drains 14 322 km2. The tributary Claree is considered as the main upstream origin of the Durance, although the river lies at 2400 m a.s.l. on the slopes of Montgenevre Pass on the French-Italian border. The Durance merges 320 km downstream with the Rh^one at 12 m a.s.l. The upper catchment (3688 km2 or 25% of the total area) from the source to the Ubaye River confluence is alpine. The middle part (8152 km2 or 57%) from the Ubaye to Mirabeau Gorge is subalpine as are the tributaries Bu€ech (1485 km2) and Verdon (2302 km2). The lower catchment (2565 km2 or 18%) from Mirabeau to Avignon is a Mediterranean river (SDAGE RM&C, 1996). The river crosses different geological formations including metamorphic rocks, alternated marls and limestone. The latter were deposited during the Secondary Era and folded during the Tertiary, thereby inducing the deposition of flysch and conglomerates. Limestones dominate in the catchment. Pleistocene glaciers covered the upper part of the catchment and created U-shaped valleys, but they did not reach the lower catchment. In the middle Durance, Pleistocene terraces still constitute a large part of the valleyfloor, while such terraces were eroded in the lower part in the Holocene. The Durance before regulation was a good example of sedimentary continuity with a regular and high slope profile that was linked to flow increases and sediment load inputs from tributaries. The homogenous character of these tributary alluvial inputs gave the Durance a more or less uniform coarse granulometry (SGFH 1916a; Belleudy & Lefort 2001). Excluding some areas (Brian¸con, Argentiere, Saint-Clement, Serre-Pon¸con, Sisteron and Mirabeau), the river essentially flows through a 1–6 km wide valley. In the late 19th century, channel widths ranged from <100 to >1600 m. Water widths in 1890 ranged between 200 and 700 m in the middle and lower Durance and <100 m in the upper river (Warner 2000). Deforestation combined with geomorphic characteristics and climate was responsible for severe erosion and the braided pattern of the river before 1860. The channel width was reduced due to a natural decrease in runoff at the end of the Little Ice Age. Later, the channel width was reduced further by channel protection works, gravel extraction, afforestation of side-valleys and mid-20th century regulation schemes (Miramont et al. 1998), resulting in a channel width 30% and wetted width 25% less than that before 1890 and an increase in agricultural land area of 62 km2 (Warner 2000). The river flows through fertile basins which have been intensively used for irrigated agriculture for centuries. As early as the late 12th century, canals were used to deliver

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water to mills and for irrigation. In 1554, the engineer Adam de Craponne built a canal to irrigate the plain of La Crau, the ancient Durance delta (Balland et al. 2002). In the late 19th century, diverted flows in the lower Durance exceeded 80 m3/s at times, above the lowest summer discharge of 42 m3/s in 1870 (Garot 1903). Conflicts caused the Ministry of Agriculture to pass a law in 1907 to control water use. Various projects were initiated (Wilhelm 1913), and the 5 January 1955 law was passed to satisfy three objectives: flood control, irrigation, and hydroelectricity (Clebert and Rouyer 1991). Large regulation schemes on the Durance and Verdon rivers started after World War II and finished in 1974. Currently, the hydroelectric network includes 18 powerhouses, operated by two major high-head storage schemes: Serre-Pon¸con dam (1955–1959, 1270 Mm3) on the Durance and Sainte-Croix dam (1971–1974, 767 Mm3) on the Verdon. The middle Durance, regulated since 1962, has seven power plants supplied by a side-channel carrying 250 m3/s (Reverchon et al. 2006). For flood control, waters from the Durance and tributaries flow through an 185 km by-pass system from 780 to 0 m asl in the Etang de Berre lagoon. The wealth and well being of the Provence region has been to the detriment of the river and alluvial landscape. About 250 km of the Durance downstream of Serre-Pon¸con dam carry 1/40th of the initial annual flow. This low flow is interspersed by short and large floods, partly controlled by water retention in reservoirs but which still are geomorphologically active (Photo 7.7). The silting of new channels is fast and encroachment of riparian forest regularly requires maintenance to hold high flows. Large volumes of freshwater and silt enter the Etang de Berre, a lagoon of 155 km2 affected by urban and industrial wastes, and contribute to its degradation.

7.9.2. Hydrology and Temperature A Mediterranean climate prevails in the Durance catchment, which receives less annual precipitation than other alpine tributaries of the Rh^one. Parde (1925) suggested that modest rainfall was caused by the surrounding mountains that open to southeast. Rainfall is minimum in July and maximum in October and November, and can be intense. The upper Durance has a nival flow regime, little influenced by glacial inputs (1% of the catchment area) but with high snowmelt flows in spring (maximum in June) and low flows in winter (Table 7.3). In the middle and lower Durance, the influence of Mediterranean rainfalls increases with decreasing altitude. Here, the flows become highly irregular, especially in autumn with large floods. Parde (1925) reported that the 19th century high floods in the Durance at Mirabeau were 5000 m3/s in November 1886, 5100 m3/s in October 1882 and 5200 m3/s in November 1843 (436 L/s/km2). Along with afforestation, the Durance-Verdon regulation schemes reduced the probability of high floods. However, the risks and socio-economic costs of large floods increased in the valleys because of extensive floodplain developments (Balland et al. 2002). The Durance hydrology changed mostly because of the high-head reservoirs and their management. Most floods in the upper catchment are stored in Serre-Pon¸con and Saint-Croix reservoirs. Short-term temperature data were recorded for the middle Durance near Serre-Pon¸con and near the Asse tributary. The upper section has cold water released from Serre-Pon¸con dam, temperature then increases rapidly in the first 10 km due to the Mediterranean climate (range is 6 C in summer and 1–2 C in winter). Maximum summer temperature is 21.5 C, but 11 C below the dam (Gras and Gilbert 1987). Further downstream, groundwater inputs from

PHOTO 7.7 The regulated middle Durance near Manosque, Alpes-deHaute-Provence (Photo: Georges Carrel).

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alluvial and hillslope aquifers increase spatial variability in temperature. In 1990–1991, water temperature ranged from 0 C in February to 27 C in July, and the daily range was 7–8 C in spring, 5–6 C in late summer and autumn, and 3–4 C in winter (Dumont et al. 1993).

7.9.3. Biogeochemistry, Bedload and Sediment The Durance has hard waters due to sulphates from Triassic gypsum located in the upper catchment. The sediment inputs from the Durance are the highest in the Rh^ one catchment at a bedload of 300 000 m3/year and suspended load of 600 000 m3/year. The specific erosion exceeds 1000 tons/ km2/year. Jurassic black marls or ‘Terres Noires’ cover 2200 km2 of the Durance catchment. These areas are often unvegetated and subject to weathering and erosion, resulting in a badlands topography with suspended solids in the rivers (Mathys et al. 2003). Results obtained on small experimental basins (see Web site: DRAIX ORE) located in the Bleone River watershed, a left-hand tributary of the middle Durance, show usual sediment concentration of 100–300 g/L, up to 800 g/L on the Laval basin (86 ha). The annual erosion rate reaches 190 tons/year on totally unvegetated area (Mathys et al. 2003). The high sediment loads cause technical, socioeconomic and ecological problems on the regulated Durance by silting by-pass sections, intermediate reservoirs of the Durance-Verdon hydroelectric complex and the Etang de Berre lagoon. The intermediate reservoirs were >50% filled by silt since their setting up from 1959 to 1991, requiring special management flushing rules (Reverchon et al. 2006).

7.9.4. Nutrients and Pollution Upstream to Serre-Pon¸con reservoir is a remarkable natural milieu (Durance valley, Claree River valley, Queyras Natural Regional Park, and Ecrins National Park) that is relatively pristine but with high tourism pressure of skiing in winter and whitewater sports, boating and bathing in Serre-Pon¸con in summer. Sewage inputs associated with seasonal peaks cause organic pollution in the river near densely populated resorts. Flow regulation by 29 hydroelectric power plants in the catchment, and weirs in the mountains for irrigation, increase pollution problems during peak tourism. Downstream from Serre-Pon¸con dam, irrigation development and agricultural practices caused increases in pollution by pesticides and organics, augmented by minimum flow policies in the river. Pollution by chlorinated solvents in the middle Durance remains a major problem for the river health and supply of drinking water.

7.9.5. Aquatic and Riparian Biodiversity The algal community of the middle Durance consists of 99 species belonging to the Chromophytae (69 species), Chlorophytae (20), Cyanophytae (7), Euglenophytae (1) and Rhodo-

PART | I Rivers of Europe

phytae (2). Diatoms are typical species of mineralized water (Cocconeis pediculus, Cymtopleura solea) and meso- or polysaprobic waters (Gomphonema parvulum, Nitzschia palea). Green algae such as Cladophora, Pediastrum and Scenedesmus are also present. Macroalgae such as Characeae (Chara vulgaris var. foetida) and Vaucheriacae (Vaucheria sp.) are common. Flow regulation led to the proliferation of filamentous Chlorophyceae and the disappearance of stenothermic species like H. foetidus (Chlorophyceae) and Fragilaria arcus (Diatomophyceae) (Cazaubon & Giudicelli 1999). The upper Durance is considered as a dynamic system with pioneer communities and softwood species (T. minima, Calamagrostis littorea, M. germanica, S. eleagnos, and S. purpurea). Downstream, dikes, dams, and water intakes reduce the fluvial dynamics. Downstream from Sisteron, the floodplain covers a large area that contain shrubs of S. triandra and S. purpurea, and large trees like Salix alba, A. and dominated by F. angustifolia. They also have some foothill species such as Q. pubescens and Acer campestre. Mediterranean species found in the lower Durance floodplain include T. gallica, Acer monspessulanum, Erianthus ravennae, Imperata cylindrical, and Spartium junceum. No data are available on macroinvertebrates before impoundment and regulation of the river (1950s). The earliest ecological studies of the Upper Durance were done between 1977 and 1979 (Dumont 1980; Dumont & Rivier 1980). Upstream to Serre-Pon¸con dam, fauna is typical of alpine rivers with species such as Amphinemura sulcicollis, A. triangularis, Capnia vidua, Dictyogenus alpinus, D. cephalotes, Nemoura fulviceps, N. mortoni, N. sinuate, P. grandis, Perlodes microcephala, Protonemura brevistyla, P. intricate, P. lateralis, P. nimborum, P. praecox, Rhabdiopteryx neglecta, Taeniopteryx kuehtreiberi (Plecoptera) and Allogamus auricollis, Drusus discolour, Rhyacophila simulatrix, and R. torrentium (Trichoptera). First studies of the middle Durance and lower Asse tributary in 1984 (Prevot 1984) recorded 207 taxa and showed the simultaneous presence of southern species, Sericostoma galeatum, Agapetus cravensis (Trichoptera), Dryops algiricus (Coleoptera), Tetisimulium bezzii, Wilhelmia mediterranea (Diptera Simuliidae), and alpine species, Ecdyonurus ruffii (Ephemeroptera), Chloroperla tripunctata, Perla bipunctata, P. marginata (Plecoptera). Simuliidae, Plecoptera (D. cephalotes, Dictyogenus ventralis, C. tripunctata), Ephemeroptera Heptageniidae (Ecdyonurus ruffii, Ecdyonurus lateralis, Rhithrogena sp.) and Oligoneuriidae (Oligoneuriella rhenana) were found in the Asse, an unregulated gravel-bed river. Macroinvertebrates in the regulated Durance were eurythermic and potamic. The main species inhabiting the river are Caenis macrura, C. luctuosa, B. lutheri, P. antipodarum, H. exocellata, Eusimulium rubzovianum, Hydropsyche modesta, Hydroptila vectis, B. fuscatus, Lymnea ovata peregra, Polycentropus flavomaculatus, Esolus pygmaeus, Lebertia pulchella, Psychomyia pusilla, Micronecta meridionalis, and Limnius intermedius. In flowing side-arms, the community was dominated by Hirudinea (Hemiclepsis marginata, E.

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octoculata), Trichoptera (Hydropsyche incognita), Gastropoda (P. antipodarum, Ancylus fluviatilis) and Odonata (Coenagrion mercuriale). In the early 1990s, Cazaubon and Giudicelli (1999) collected 77 taxa in the middle Durance. Densities ranged from 1060 to 1900 individuals/m2. Thirty taxa were considered common and represented 90% of the sampled individuals. The community was composed of potamal species such as H. exocellata (the dominant species considered as the ‘fundamental species in the macroinvertebrate community of the regulated Durance’), H. modesta, B. fuscatus, and B. pavidus, and by rhithral species of H. incognita, B. lutheri and Ecdyonurus helveticus (sporadic) and Caenis pusilla, a southern species along with Leuctra geniculata (Plecoptera), Hydroptila vectis, Polycentropus flavomaculatus and Setodes sp. (Trichoptera). Two species of Simuliidae occurred: Simulium pseudequinum was abundant during spring and summer while S. bezzii was abundant in winter. Orthocladiinae (Diptera, Chironomidae) were present throughout the year. Because of high summer temperatures, stenothermic species such as D. cephalotes (Plecoptera) present upstream and just downstream of Serre-Pon¸con dam are not found in the middle Durance. As is the case for Dictyogenus ventralis, Isoperla grammatica, Perla bipunctata, P. marginata (Plecoptera), Acentrella sinaica, Rhithrogena sp. and Epeorus sp. (Ephemeroptera) that are present in the Asse and Buech rivers. Univoltine species such as the Ephemeroptera Serattella ignita and O. rhenana are probably favoured by the warmer thermal regime in the middle Durance. Other species such as the polyvoltine species Simulium bezzi maintain populations by having a single generation in winter. The reduction in discharge and narrowing of the riverbed decreased habitat availability and eliminated backwater habitats, leading to the extinction of species such as E. octoculata, Dina lineata, and H. marginata (Hirudinea). Near the confluence with the Rh^one, the macroinvertebrate community has several Mediterranean taxa like Crustacea Gammarus pulex gallicus. The two exotic species of Crustacea, A. desmarestii (also a Mediterranean species) and O. limosus were recorded. Data of fishes in the Durance come mainly from the grey literature. Based on Rabotin (2002), Holley and Guibert (2005) and Irz (2006), 43 species from 14 families were recorded along the Durance river, including the introduced lacustrine species S. alpinus and C. lavaretus. The Durance basin can be considered a special ichthyoregion in the Rh^one catchment (Changeux & Pont 1995) with high occurrences of southern cyprinids, soiffe, southern barbel and apron. Longitudinally, the fish assemblages include introduced brook trout in the headwaters, followed successively by brown trout, then cyprinids along with blageon and barbel, to migratory species of eel, twaite shad and mugilids M. cephalus, L. ramada near the Rh^ one confluence. Of the 42 species sampled in the Durance, 16 are non-native and include carp and crucian carp. Most non-native species were

introduced in the late 20th century for angling, especially salmonids (brook trout, rainbow trout, grayling) and in reservoirs (C. lavaretus and S. alpinus). Other non-native species colonised the Durance from the Rh^one, including cyprinids Chondrostoma nasus, Carassius gibelio, Carassius auratus, percids Sander lucioperca, centrarchids Lepomis gibbosus, M. salmoides, the ictalurid Ameiurus melas, and the poeciliid Gambusia affinis. The last exotic species were the topmouth gudgeon (1999) and the cobitid Cobitis bilineata which suddenly occurred after 1994. River regulation altered the longitudinal distribution of fishes, partially known from an historical fish map (Leger 1934). Flow regulation caused other ecological changes including an increase in fish growth (Bouchard et al. 1998) and hybridization between two cyprinids C. toxostoma and C. nasus (Costedoat et al. 2005, 2007). Three species of Urodela and seven species of Anoura are found along the Durance; the common toad, marsh frog and fire salamandra are the most common. The alpine newt is present in the upper Durance valley, and this constitutes its southern distribution limit. The palmate newt occurs only at one location in the lower Durance. The Mediterranean tree frog is present far upstream in the Durance valley up to Gap, whereas the Parsley frog occurs in the middle and lower river in low numbers. Perez’s frog is inhabits the lower Durance, but populations are decreasing with the expansion of marsh frog. The dark green snake was recorded only in the middle Durance, and viperine water snake occurs in the middle and lower river. The European pond terrapin colonizes in the lower Durance. The Durance holds one of the highest species richness in France with over 260 bird species. Most of the French species, except those occurring in mountains and those linked to marine shores, are present. Over 60 species having a European Community status were recorded, including little bittern (20– 30 pairs), black kite (100–150 pairs), calandra lark (Melanocorypha calandra) (6–10 pairs, 20% of the French population) and little bustard (Tetrax tetrax) (15 individuals). Alluvial forests are colonized by several species of herons (little egret, black-crowded night heron, and buff-backed heron). Several paludicole (marsh-inhabiting) species occur in reedbeds such as purple heron, Eurasian bittern (Botaurus stellaris), little bittern, spotted crake (Porzana porzana), moustached warbler (Acrocephalus melanopogon), and penduline-tit (Remiz pendulinus). Gravels bars and movable shores offer habitats for common stern, little ringed plover, European bee-eater (Merops apiaster) and common kingfisher. The European beaver is found in the Durance valley, even in the upper river (upstream of Sisteron). The southwestern water vole, muskrat and coypu were recorded only in the lower Durance.

7.9.6. Management and Conservation The national and regional socio-economic importance of the Durance basin is considerable. Hydropower generation which in <60 years has increased from 95 MW (SGFH

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1916b) to 2000 MW provides 10% of the hydroelectric production in France. The reservoirs guarantee water for irrigation and drinking through a complex network of canals. Southwest users benefit from a water supply of 114 m3/s from the Durance by-channel and southeast users receive a water supply of 40 m3/s from the Verdon scheme. About 100 000 ha in Provence are irrigated through the DuranceVerdon schemes. Water demand linked to tourism in large reservoirs and rivers in the Durance basin has been underestimated. The high tourism in winter for skiing is causing a growing demand of water for artificial snow (average 3000 m3/ha) and tourism in summer relies on rivers for whitewater sports and Serre-Pon¸con reservoir (3000 ha) for bathing and boating. Lake Sainte-Croix and the famous Verdon canyon have also become a touristic attraction. Tourism now represents 11% of the gross regional product in the Provence-Alpes-C^ote d’Azur. A large part of the Durance (from 678 to 12 m a.s.l., area: 15 954 ha, FR9312003) belongs to the Natura 2000 network with many natural habitats in the mountains and Mediterranean zone. Durance hydrosystem requires complex measures for rehabilitation that consider all socio-economic and environmental stakeholders. A large governmental mission (Balland et al. 2002) was recently entrusted with the decision-making processes and coordination between environmental stakeholders. The main concern is the change of flow regime in the regulated river, the transfer of fine sediment load, and the rehabilitation of Berre lagoon. The transport of suspended matter was partly restored up to 1.8 million tons (SOGREAH 2000), and flow of the Durance canal was modified in 1995 to restore the threatened Etang de Berre. Here, freshwater inputs decreased from 3.6 Gm3 per year (1966–1995) to 2.1 Gm3 and floods carrying highsuspended sediment loads were maintained in the former channel to reduce sediment deposition in the Etang de Berre. The upper Durance has three waterbodies that are not considered as heavily modified. The most two upstream waterbodies have high probability to reach the good status by 2015, the third one, located on a tributary affected by hydropower and gravel abstraction, has a risk of failing to meet the good ecological status by 2015. The Serre-Pon¸con reservoir is classified as heavily modified. Downstream, two waterbodies are also identified as heavily modified and the lower part upstream of the confluence with the Rh^ one River has a high risk of failing to meet the WFD objectives by 2015. For other waterbobies, there is doubt about their ability to reach good status by 2015.

7.10. CONCLUSIONS AND PERSPECTIVES Before regulation, the Rh^ one basin had a large array of landscapes and high biological diversity. Tributaries flowing from Alps, Jura, Vosges, Massif Central and Cevennes had different morphological, hydrological and ecological characteristics that differentially influenced the physical, chem-

PART | I Rivers of Europe

ical and biological features of the Rh^one. In the Swiss Valais, the first and second river training works and the construction of high-head storage reservoirs considerably modified the hydrological regime, suspended sediment load, surface water temperature, ground water level and temperature and oxygen content in Lake Leman. Present ecological features and biodiversity in the Rh^one valley are far from those prevailing at the end of the 19th century. Today, natural habitats of the Swiss Rh^one floodplain cover only 6% of the whole floodplain area and analysis of historic maps indicate a loss of 90–100% of alluvial habitats areas. The objective of the third Rh^one correction is to (1) insure effective protection against floods as water levels during flooding are 3–4 m above the floodplain and dikes can break because most are old and easily damaged, (2) improve the ecological potential of the floodplain by promoting alluvial areas and restoring natural processes, and (3) promote economic development and tourism in the Valais. The Arve River flowing from Mont Blanc supplied the Rh^one with large amounts of coarse sediments up to the 20th century, whereas today only fine sediments reach the Rh^one because of the reservoirs just downstream of Lake Leman. From an ecological point of view, the Arve contributes cold water to the Rh^one and modifies its physico-chemistry. The presence of ‘Perte du Rh^one’ a few kilometres downstream from the lake played an important role for the colonization of the upper river by fishes. The first French hydroelectric power station was built in 1884 on the Valserine River near its confluence with the Rh^ one and another was constructed in 1899 on the Rh^ one upstream of ‘Perte du Rh^one’; they contributed greatly to local industrial development. The gorge was used to build Genissiat dam, the head of a series of six hydropower plants that greatly modified the physical and biological characteristics of the river. The confluence of Rh^ one with the Sa^one River at Lyon is a major source of hydrological, physico-chemical and biological discontinuity along the French Rh^one River. The urbanization and industrial development of Lyon, in peculiar downstream, has a major influence on water quality in the Rh^one. Downstream, arrival of cold water from the Isere allows the recovery of several fishes present in the French upper Rh^one. The beginning of the Mediterranean zone and the presence of several tributaries downstream from the Isere lead to a progressive change in riverine features, especially the increase in water temperature. Downstream from Arles, the delta of Camargue constitutes an exceptional landscape that, despite human interventions to limit damages caused by large floods, remains an area of great ecological, cultural and sociological importance. Special attention has been paid recently to improve flood management downstream of Vallabregues by creating overflow areas upstream and by increasing embankment security. Sediment deficit in the delta led to a progressive advance of the sea, and studies are being conducted to find ways to restore sediment transport to the Rh^one delta.

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The natural functioning of the main tributaries Arve, Ain, Sa^ one, Isere, Dr^ ome, Ardeche, Durance, and Gard has been greatly altered for the past 200 years. The main environmental problems on the Ain are linked to flow management for hydroelectrical production and groundwater extraction for irrigation in the lower valley. The hydroelectric facility in the middle valley led to the loss of areas with high morphological and ecological interest. Protection of the lower river and associated wetlands and biodiversity is presently a great challenge. The Sa^ one valley has been strongly altered by human activities (channel regulation and dredging for navigation, industrialization, agriculture) and, despite the will to restore and improve the morphology and ecology of the river floodplain, management goals to maintain existing economic activities and diminish pollution levels (toxic pollution, pesticides), a protection program against floods, and enhancement of ecological functions of the river remains a difficult task. The Durance catchment is extensively used for hydroelectricity production, irrigation, and drinking water production. Geomorphological and ecological processes are heavily altered by water abstraction and management objectives in the WFD context are quite difficult to attain. At the watershed scale, much effort has been made to move from a traditional strategy of flood defence to one of flood risk management. Local populations and water management committees joined efforts to analyse the main causes of flooding and elaborate policies and action plans to reduce risk stochasticity, diminish vulnerability, and manage residual risk. All these measures must be integrated in a more general program that includes the set up of the WFD, the protection of surface and groundwater quality and quantity, and the preservation of biodiversity. The French government, Watershed Management authorities, ‘Agence de l’Environnement et de la Maitrise de l’Energie’, ‘Voies Navigables de France’, local Regional Councils (Languedoc-Roussillon, Provence-AlpesC^ ote-d’Azur, Rh^ one-Alpes, Bourgogne et Franche-Comte,) and the ‘Compagnie Nationale du Rh^ one’ signed a global program towards sustainable development of the Rh^one and its valley named ‘Plan Rh^ one’. This ambitious program has six themes: (1) a patrimonial and cultural section devoted to the improvement of the knowledge of cultural development linked to the Rh^ one River along the valley, and a new appropriation of the river by the public at large, (2) a global strategy to prevent flood risks, (3) a program of water quality improvement (WFD) and achievement of the inventory of Sites of Community importance (Natura 2000 sites, Sa^ one floodplain and Camargue), (4) promotion of hydroelectricity and eolian energy production, (5) promotion of fluvial transport along the Rh^ one-Sa^ one axis especially by harbour infrastructure improvement, and (6) development of tourism (river boating, ‘veloroute’). The cost of this program (2006–2013) will be >800 Me. After the period of river regulation and deterioration during the 20th century, the will to insure good water quality and quantity has progressively led to the awareness of the necessity to protect and restore, as much as possible, the

ecological functioning of rivers. Recent large floods, both in the Swiss (Valais) and French part of the river (especially the lower Rh^one and Camargue), have forced authorities to reconsider sediment and water transfer along the river. Knowledge about the impact of pesticides and toxins on the biology is still insufficient and research is urgently needed. New problems linked to global climate change are occurring, especially regarding water temperature. To meet current objectives (i.e. river ecological restoration and objectives of the Water Framework Directive) is a great challenge as well as for the small and large rivers of the Rh^one catchment because of the necessity to integrate socio-economic and ecological objectives.

Acknowledgements We thank the following people for their contributions to the preparation of this chapter: Corinne Masse for help in data collection and preparation, Alain Poirel for water temperature data on the French part of the Rh^one River and tributaries, Frederique Eyrolles (Laboratoire d’etudes Radioecologiques en milieu Continental et Marin) for data about radionuclides, Vincent Passani for hydrological data of the Durance watershed, Jacky Girel, Henri Persat, Jean-Claude Rostan, Gudrun Bornette, Jean-Fran¸cois Fruget, Sylvain Doledec, Bernard Dumont, Pierre Joly, Sandrine Plenet and Eric Feunteun for their valuable help and discussions about biodiversity of the Rh^one River watershed. The Museum National d’Histoire Naturelle provided helpful data on biodiversity along river corridors ([Ed]. 2003–2006; Inventaire national du Patrimoine naturel (Web site: http://inpn.mnhn.fr/)). We thank Electricite de France (EDF) and the Compagnie Nationale du Rh^ one (CNR) for providing details about discharge, dam features and hydroelectricity production, the Commission internationale pour la protection des eaux du Leman for providing physico-chemical data of the Rh^one River Downstream from Leman Lake and the Federal Office for the Environment (FOEN) for hydrological and temperature data in the Swiss Upper Rh^one valley.

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RELEVANT WEBSITES http://www.ecologie.gouv.fr/HYDRO-banque-nationale-de-donnees.html: National Data Bank ob Hydrometry and Hydrology (France). http://rdb.eaurmc.fr/: Information about water quality, aquatic milieu and water management on the French Rh^one watershed. http://195.167.226.100/DCE/RM/RM_etat-des-lieux.htm: data about WFD implementation in the French Rh^one waterhed. http://www.rhonealpes.ecologie.gouv.fr/orgfh/html_orgfh_fichesesp.php3: Direction Regionale de l’Environnement Rh^one-Alpes. Delegation de bassin Rh^one-Mediterranee. Les orientations regionales de la gestion de la faune sauvage et d’amelioration de la qualite de ses habitats (O.R.G.F.H.) en Rh^one-Alpes. http://www.oieau.org/5pcrd/projets/EUROLAKES.htm: EUROLAKES, Integrated Water Resource Management for Important Deep European Lakes and their Catchment Areas. http://natura2000.environnement.gouv.fr/regions/idxreg.html: Natura 2000 network in France. http://www.cipel.org/sp/: website of the International Commission for the Protection of Lake Geneva (CIPEL). http://195.167.226.100/peche/carnet.html, Statistics on professional and amateur fisheries on the Rh^one and Sa^one are available since 1988. http://www.vs.ch/Press/DS_12/PU-2005-06-29-7882/fr/Rapport%20FR. pdf: Documentation on the third correction of the Rh^one in Valais, Switzerland. www.irsn.org: ‘Institut de Radioprotection et de Surete Nucleaire’, the IRSN’s scientific website gives information about the Institute’s research activities in the field of nuclear safety and radiation protection. http://inpn.mnhn.fr/: Museum national d’Histoire naturelle [Ed]. 2003– 2006. /Inventaire national du Patrimoine naturel. http://www.thonon.inra.fr/poisson/pacagelacustre/pacagesalmonides/ omblechevalier/omblepacage.htm: data about fish farming in the Lake Leman. http://lepus.unine.ch/carto/: Swiss Center of Animal Cartography ÓCSCF http://www.karch.ch/karch/d/pro/rolia/roliafs2.html: Red-list of Amphibians in Switzerland. http://www.karch.ch/karch/f/pro/rolir/rolirfs2.html: Red-list of Reptiles in Switzerland. http://www.cren-Rh^onealpes.fr/part2/progs/life_apron.htm: Life program on the Apron.

Chapter 8

The Fennoscandian Shield B. Malmqvist

T. Muotka

C. Nilsson

Department of Ecology and Environmental Science, Umea University, SE-90187 Umea, Sweden

Department of Biology, University of Oulu, P.O. Box 3000, FIN-90014 Oulu, Finland

Department of Ecology and Environmental Science, Umea University, SE-90187 Umea, Sweden

H. Timm Estonian University of Life Sciences, Agricultural and Environmental Institute, Centre for Limnology, Tartu County, EE61101 Estonia

8.1.

8.2.

8.3. 8.4.

Introduction 8.1.1. Biogeographic Setting 8.1.2. Human Colonization 8.1.3. Human-Caused Threats to River Biodiversity 8.1.4. Biogeography The Rivers 8.2.1. The Dal River 8.2.2. The Ume River 8.2.3. The Torne River 8.2.4. River Koutajoki 8.2.5. The Neva Conclusions and Outlook Acknowledgements References

8.1. INTRODUCTION 8.1.1. Biogeographic Setting The Fennoscandian Shield encompasses roughly the northern half of Sweden, all of Finland, and the westernmost part of European Russia, ranging in latitudes between 60 and 70 , and intersecting the Arctic Circle. This region also represents the westernmost extension of the taiga biome and is well within the boreal zone, covering a tetragonshaped area between the longitudes 11 (in the southwest) and 41 east (in the northeast). Bedrock is Precambrian, dating back 1.7–1.9 billion years and including metasedimentary, metavolcanic rocks and several generations of Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

granitoids. Even older (2.5–3.1 billion years) rocks (mainly gneisses and greenstone belts) characterize the Archean geological province in northern Finland and the Kola Peninsula. These rocks are often overlaid by moraines shaped by erosion by repeated glacial events into a hilly landscape with numerous lakes and watercourses. For obvious reasons Finland is known as the ‘land of the thousand lakes’; in fact Finland has over 56 000 lakes with a surface area >1 ha. Despite the stunning numbers, their combined volume is less than a fourth of Lake Ladoga, the largest Fennoscandian Shield lake (Larsson 2004). Most rivers in the ecoregion flow into the Baltic proper, or into its extensions, the Gulf of Finland or the Bothnian Bay (Figure 8.1). Peripheral parts of the region have rivers draining to the north (e.g. the Tenojoki flowing into the Tanafjord which in turn connects to the Barents Sea), and in the case of the Kola Peninsula, to the south. The majority of the rivers flow into the Baltic and its fringing bays. In Sweden, originating in the mountain chain along the border to Norway, these rivers generally flow in an easterly or southeasterly direction, whereas the Finnish rivers flow westward or southward into the Gulf of Finland. The Koutajoki is the exception and drains in an easterly direction into the White Sea. At a mean annual discharge of >2500 m3/s, the largest river is the Neva, which is situated in the southeast, drains Lake Ladoga – Europe’s largest lake at 18 000 km2 – and passes through the large city of St. Petersburg (4.7 million inhabitants in 2002). Other large rivers of the region include the Torne–Kalix system (catchment: 58 000 km2) connected by the unique bifurcation, the T€arend€o River, linking the two main rivers. The Kemi, Pite, Lule and Ume Rivers, the latter with its almost equal-sized tributary the Vindel, and 297

298

FIGURE 8.1 Digital elevation model (upper panel) and drainage network (lower panel) of The Fennoscandian Shield.

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Chapter | 8 The Fennoscandian Shield

the Dal River are further examples of rivers extending 400– 550 km in length (Figure 8.1). These are all mainly snowmelt-driven rivers with flow peaking in early to mid-summer. An extended ice cover, a general feature in the region, lasts from November through March; ice break-up may not occur until late May in some rivers and years. The climate of the region is cold-humid and relatively mild considering the high latitude (60–70 N) due to the proximity of the Gulf Stream. Owing to this and the noticeable marine influence, temperatures can be up to 20 C warmer than normal for these latitudes. These benign climate conditions gradually erode to the east, although summers can be hot; for example the lowest and highest temperatures recorded at Oulanka Research Station in the Koutajoki catchment on the Arctic Circle near the border between Finland and Russia are 48 and +32 C, respectively. Winters in the region tend to be extended with a mean temperature in the coldest month of about 10 to 15 C and snow cover is present for 4–5 months. The high latitude is responsible for a seasonally variable day length, ranging between 0 and 24 h depending on season and is increasingly variable to the north. Summers are relatively short but the long days compensate for their brevity by promoting primary production. Annual precipitation ranges between 500 and 700 mm, mostly as snow. Snow accumulation and snowmelt are significant drivers of runoff patterns in the region. A prominent feature of the Baltic during the Holocene was its alternation between being a large freshwater lake and a marine body of water depending on the nature of the outlet shifting between contact with or isolation from the North Sea. At the recession of the ice until 11 500 BP the Baltic Ice Lake was formed, followed by the Yoldia Sea (11 500– 10 700 BP), the Ancylus Lake (10 700–9800 BP), and the Littorina Sea (from 9800 BP). Due to isostatic land uplift and sea-level rise the present Baltic Sea is a stage of the Littorina Sea, ranging in salinity from 2% to 3% in its entrance/exit area (the Belt Sea) to nearly pure freshwater (0.2–0.3%) in the northern Bothnian Bay. The presence of historic high water-levels is marked by significant characteristics in the landscape and rivers. Most significantly, the moraine soils have become locally depleted in finer fractions, whereas others have received fines creating sedimentary soils. At the highest altitudinal extensions of the sea (250 m asl), substrate heterogeneity appears higher than elsewhere with possible positive influences on biotic diversity (Nilsson et al. 1989; Dunn et al. 2006). The isostatic rebound is markedly high in the central Fennoscandian Shield, reaching a maximum near the coast of northern V€asterbotten, Sweden, where it amounts to 0.9 m per 100 years (Ekman 1996). This rapid uplift, among other effects of ecological significance, increases the dynamics in river mouths and results in an extension of present river lengths and the shaping of new rivers. Glacial processes during the advance and retreat of ice had impacts of great consequence for the landscape. At its maximum during the last glacial period, the ice was

2000 m thick in northern Finland and the Bothnian Bay (Lambeck et al. 1998). Erosion from the weight and movement of ice resulted in the crushing and scarring of the bedrock, enabling boulders, rocks and soils to be transported over long distances and deposited as erratic blocks and moraine. The landscape often shows directional evidence of ice movements in the shape of hills and lakes. River valleys in the region sometimes show such evidence in the form of steep valley slopes on the lee side in relation to the predominant direction of ice movement (Rudberg 1984). Glacial rivers resulting from the melting ice brought massive amounts of eroded material that shaped eskers and deltas. Rivers traverse post-glacial sediments deposited by glacial processes but also, below the highest coastline, by lacustrine and marine processes. Wave action during periods with high sea/lake levels caused washing of fines in exposed areas. Local geology influences river water chemistry. Data from Swedish river mouths provide insights into changes in water chemistry comprising a 30-year-period (F€ olster & Wilander 2002). As confirmed through concentrations of sea salts, there is a clear influence of climate on water chemistry reflecting the North Atlantic Oscillation (F€olster & Wilander 2002) with consequences for biota (Bradley & Ormerod 2001). Silica, in contrast to the general pattern of high constituent concentrations at low discharge, is thought to be low due to an increased uptake in plankton in years having long water residence time in lakes and reservoirs (F€ olster & Wilander 2002). The clearest temporal trends over the 30 years included a decline in SO4 from decreasing deposition. In the northernmost Torne and Kalix rivers, this trend was not present because of their geographical position in which the transport from remote continental sources is small. The amount of organic material did not vary regularly during the time period but its quality seems to have changed to a darker brown colour with higher nitrogen content as shown by an increasing absorbance and decreasing C/N ratio.

8.1.2. Human Colonization Humans have lived in the region for millennia and, as recent discoveries suggest, even for much longer than believed. For € aset, example the stone-age settlement (6000 BP) at Alvn€ Vuollerim, at the confluence of the two main branches of the Lule River (at the Arctic Circle) was discovered only 20 years ago, and colonization of Finland already occurred 9000 BP. Along with the coastal areas, river valleys were highly attractive for early colonisers. One obvious reason was that the rivers were teeming with fish and attracted various game. Hunting and fishing were clearly important. Farming came later, although a well-developed agriculture was present along the coast of the Bothnian Bay since 2500– 3200 BP. Reindeer husbandry is intimately linked to the life of the Sami people, who populate parts of the region, and has been important for centuries. The moving of reindeer herds from lowland forests to the mountains and the return back in

300

autumn are recurrent spring and autumn activities. Ample amounts of lichens supply winter fodder in the forests, but grazing is better in the mountains during the summers. The pressure from biting insects is also lower in the mountains in summer, while it can be stressful in the boreal forest, especially at higher temperature and weak winds. The well-being of reindeer is influenced by the rivers, directly by affecting migration and indirectly by the production of biting insects. Until relatively recently reindeer were driven by Sami on foot or skis and usually on ice along the rivers, but now this tradition has been substituted by truck transport aided by helicopter surveillance and electronic communication. Along impounded rivers, a return to traditional reindeer migration would be almost impossible today because of poor ice conditions associated with flow regulation. In the relatively flatter terrain of Finland, reindeer movement is far more restricted than in Sweden. Other wild animals also were annual migrants and already 5000 years BP (Swedish National Encyclopedia) people constructed pitfalls to trap wild reindeer and moose, often in systems of multiple pits connected by fences. These traps were even used after humans started to live permanently in the region until the method was prohibited in Sweden in 1864. The fact that most artefacts and historical sites, like pitfall trap systems, have been found along rivers emphasizes that river valleys served as important corridors for human settlement.

8.1.3. Human-Caused Threats to River Biodiversity 8.1.3.1 Agriculture and Forestry Farming changed the demographics of the region. The transition from growing wheat, which is sensitive to a cold climate, to the less sensitive barley, and the beginning of manure use around 2500–3000 BP allowed culturing of relatively meagre soils. Agriculture provided a more stable factor that benefited human settlement, which was further bolstered by new crops such as flax and rye 1000 BP. Along rivers in northern Scandinavia, the production of hay on riverbanks and meadows inundated during the annual spring flood was important for food for domestic animals. In these riparian habitats, snowmelt water fertilized the soils by annually bringing nutrients. Today, these fertile grounds are no longer used (except in a few places as sites of historical interest) and have become overgrown or impacted by flow regulation. Forests were (and still are) a main source of income in the region, and as rivers penetrate forests there are multiple reasons for how human activities affected the rivers. Some important influences included the ways forests were managed and cut, timber transported using flowing water, and dams constructed. In northern Sweden, wood was harvested and processed from the late 17th century until the early 1900s to provide charcoal for the growing ironworks in the south. The production of tar, and in some areas potash, was also significant. Even if the production of charcoal, tar and material for

PART | I Rivers of Europe

ship-building was important, the technically improved sawing techniques in the second half of the 18th century and expanding industrialization boosted timber cutting and changed the landscape extensively when water-driven timber industries began to flourish along the rivers. While most accessible areas were harvested first, even remote areas of the region now have been logged at least once. Since around 1950 motorized clear cutting across large areas of land replaced the selective harvest of large trees. Only in some areas, notably in Russian Karelia and the Kola Peninsula, nearly pristine forests remain today where they make up an informative reminiscence of the historical features of the landscape. One of the most important values of these areas is that they provide target conditions to be used for restoration efforts. Ditching, which was extensively used to improve forest production was also done in the context of the peat industry. Negative side effects from ditching include increased concentrations of aluminium and suspended solids as well as decreased alkalinity (Vuori et al. 1998). Fish habitats in many small streams were also destroyed by ditching. At a larger scale, dense ditching systems likely reduced water retention capacity and lead to more spiky hydrographs. It seems that ditching now is losing popularity. Permission has been more restrictive in Sweden since 1986, but ditching is still allowed in conjunction with planting of clear-cut areas. Many older ditches are becoming shallower and losing their function for draining. In Finland, little new ditching is taking place but old ditches are being re-opened in many areas. However, even this is rather restricted and the riparian zone must be left untouched. Whether negative ditching effects in forested lands will be reversed remains to be assessed. Rivers were used to transport timber to coastal industries. For this purpose, most rivers have been channelized, bedrock thresholds blasted and splash dams built. No river was too small for timber transport; the smaller ones were impounded with temporary splash dams and timber sent down after snowmelt in spring. Impacts during the timber floating era, which lasted until the 1970s, were considerable (Nilsson et al. 2005a) with potentially severe effects on the fishery in rivers and the sea (Figure 8.2), and other aquatic biota and riparian ecosystems. In Finland and Sweden, restoration to shift rivers back to their natural state was taken up soon after log driving had been discontinued. This work involved returning large boulders into river channels, opening up closed side channels and removing constructions such as dams and piers in the rivers. Commercial forestry has altered natural forests extensively across the Fennoscandian Shield, causing shifts in tree species composition, clear cutting of large areas, reduction of tree age, soil scarification and fertilization, and dense networks of ditches and forest roads. All contribute to changes in water chemistry (nutrient leakage), soil erosion, and increased solar radiation onto streams, especially where no buffer strips provide shade, with consequences for fish, other aquatic life, and riparian organisms such as bryophytes (Hylander et al. 2002). Exactly how much commercial

Chapter | 8 The Fennoscandian Shield

301

FIGURE 8.3 The gradually decreasing discharge amplitude (monthly means) in the lower parts of the Lule River associated with increasing hydropower impacts (from Bergstr€om and Lindstr€om, 1999).

FIGURE 8.2 Total length of floatways (top), and amounts of logs (middle) transported in Swedish rivers, and overall catches of Baltic salmon in the sea (from Nilsson et al. 2005).

trolled remotely by power companies to optimize power production. Flow regulation gives rise to a discharge pattern that is strongly altered. The flow is evened out over the course of the year relative to the natural flow regime with a typical annual water-level variation of 3–6 m. In wintertime, when electricity needed for heating, flows are considerably greater now than before when they were low due to snow accumulation and frozen soils (Figure 8.3). The current flow pattern is in stark contrast to the summer peak flows, which have become truncated in regulated rivers because of filling and storage in mountain reservoirs. Short-term daily oscillations also often occur as water is withheld to some extent at night and used in the daytime. Flow-induced changes following river regulation can have significant effects on riverine life. The normal flow of a river in the region shows dramatic seasonality with a peak in early summer due to snowmelt and low discharge in late summer and winter (Figure 8.4). Such a hydrograph causes large areas to be seasonally flooded and generates erosional forces of substantial magnitude that act on the physical habitat and directly on biota along the shorelines of reservoirs. A regulated river can be recognized as such by the proximity of

forestry has affected rivers is far from clear, but rivers obviously receive less wood today than they did in the past (Liljaniemi et al. 2002). Associated ditching also affected water chemistry, particle transport and runoff rates.

8.1.3.2 River Regulation River regulation for hydropower production is a major impact with serious consequences for ecosystem integrity such as instream production, fish migration, riparian vegetation, and ecosystem connectivity. In northern Sweden, most of the electricity is produced and exported to more densely populated and industrialized southern parts outside the Fennoscandian Shield. For Sweden, about half of the electricity is produced in hydropower plants. The most common model is to have storage reservoirs in mountain areas that are regulated over several years, depending on needs. This long-term scheme is used in combination with short-term run-of-the-river regulation of impoundments, often con-

FIGURE 8.4 River regulation changes the hydrograph from a natural state of high summer and low winter flows (reconstructed in the graph) to a more or less constant discharge throughout the year as demonstrated in this graph from the Lule River in Sweden. In 1993 the annual flood in combination with rain led to unusually high summer flow, whereas in 1995, when a 100-year flood occurred in unregulated rivers in the region, empty reservoirs were able to largely contain the water in the Lule River (from Bergstr€om and Lindstr€om, 1999).

302

TABLE 8.1 General characterization of the Fennoscandian Shield

Mean catchment elevation (m) Catchment area (km2)

Neva

Kymijoki

104 281 000

128 37 159

Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25%) ecological regions Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparse vegetation Wetland Freshwater bodies

Kiiminkijoki 127 3900

Koutajoki

Torne€ alven

Kalix€ alven

Lule€ alven

Ume€ alven

Indals€ alven

Dal€ alven

196 28 210

407 40 157

397 17 893

595 24 885

511 26 815

505 25 849

394 29 040

79.8 61.8 3.2 3 60

10.0 55.8 3.2 1 60

1.4 53.0 1.2 1 60

1.7a 55.9 0.7 1 60

11.8 50.5 2.2 2 60; 62

8.9 51.6 1.7 2 60

15.8 69.7 2.8 2 60; 62

13.6 71.1 1.3 2 60; 62

14.1 67.4 1.0 2 60

12.0 66.0 2.1 3 60

0.3 7.4 6.0 57.5 1.9 0.0 8.8 18.2

1.3 8.0 0.0 64.8 7.0 0.0 1.2 17.7

0.5 2.1 0.0 51.9 19.8 0.0 22.6 3.1

0.1 0.6 10.8 59.9 4.0 0.6 2.8 21.3

0.3 0.5 0.4 41.1 32.6 5.0 15.1 5.0

0.3 0.3 0.3 54.1 18.6 5.6 17.1 3.7

0.2 0.2 0.1 40.1 24.0 18.2 8.0 9.2

0.3 1.0 0.2 50.4 28.4 4.3 8.0 7.4

0.4 2.1 3.8 48.8 24.7 2.6 8.2 9.4

1.0 3.7 1.7 62.1 17.8 0.1 7.1 6.5

5.1

0.3

5.2

10.3

23.0

16.8

46.3

4.0

10.0

7.8

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

Fragmentation (1–3)

3

3

1

2b

1

1

3

3

3

3

2 44 3 3 17 6181

0 34 3 0 17 22 176

0 20 1 0 6 22 837

3 17 1 0 2 6517

1 25 0 0 2 25 377

0 23 1 0 2 26 278

15 25 1 0 1 26 466

16 25 1 1 5 24 062

20 24 2 0 5 24 674

10 34 2 0 9 25 397

Number of large dams (>15 m) Native fish species Non-native fish species Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person) a

In Finland only. Based on partly unconfirmed information. For data sources and detailed explanation see Chapter 1.

b

PART | I Rivers of Europe

Protected area (% of catchment) Water stress (1–3) 1995 2070

303

Chapter | 8 The Fennoscandian Shield

forest to the river channel, in contrast to free-flowing rivers that have wide riparian areas denuded of perennial plants – a consequence of large and intact snowmelt-driven flooding. Life forms on these banks require recurring disturbances by high floods to remain natural. The annual floods create bare soils that rapidly colonizing plant species can invade and prevent dominant species from overwhelming the habitat, thereby promoting a highly diverse community typical of large river littorals (Table 8.1). Regulation completely alters river habitats. Former rapids become inundated or are lost or removed using explosives, and the river’s profile is shifted from being gradual to showing steps with long, slow-flowing sections, much like elongated lakes that extend for tens of kilometers punctuated by dams. In some cases, river water is diverted from the main channel into canals or tubes for several kilometers to turbineprovided power plants located at the side of the natural river and leaving the original channel nearly dry or with a ‘minimum flow’. Some of these channels have been provided with weirs to increase water volume. This type of regulation differs from traditional plants that were built in association with the dam itself. A problem for river life in the newer type occurs when reservoirs are already filled and rainstorms contribute more water. Often then the dam gates are suddenly opened and large amounts of water released downstream causing flood disturbance to fish and other animals. Operating dams with a small margin that results in sudden flushing events has been identified as the strongest negative effect of river regulation on macroinvertebrate diversity in north Swedish regulated rivers (Englund & Malmqvist 1996). The fragmentation of rivers by dams constitutes an important impact caused by dams. Fragmentation is a result of the barrier effect of the dams and by the establishment of large lake-like reservoirs that disconnect running waters. One of the most drastic effects is the complete obstruction of upstream migration of many fish species, in particular anadromous species such as salmon, sea trout and river lamprey. Even if these fishes were able to migrate up regulated rivers, the degree to which natural habitats are impacted is often so great that no or a limited area of suitable spawning grounds remain. Where sections or tributaries are still undamaged, the provision of fishways can be an important management strategy. In many cases, however, downstream migrating young fish are damaged during the passage through turbines. To compensate significant losses of sea-running salmon and sea trout, Finland and Sweden have developed extensive hatchery programs. The number of reared salmon smolt released is 2 million per year in Sweden alone. Sea trout are released at a rate of over half a million annually. To maintain genetic integrity, hatcheries have been located on each of the main rivers to breed the particular stocks from these rivers. Although compensation releases have managed to maintain a fishery in the Baltic, it has not been a complete success because the increased fishery on salmon tends to take a larger share of wild salmon and thereby threatens the remaining natural populations, for example the one breeding in the Torne River. The

increasing availability of inexpensive farm salmon, especially from Norway, is presently ameliorating the pressure caused by commercial fishing on Baltic salmon. Another effect of fragmentation by dams is the obstruction of downstream seed dispersal, leading to discontinuous plant communities and greater risk for extinction (Jansson et al. 2000). A striking effect of river regulation is also the depauperation of the littoral zone of regulated lakes and reservoirs caused by the alternating filling and drawing down (Grimas 1961, 1962; Nilsson & Keddy 1988). In some large reservoirs with wide water-level fluctuations, the littoral zone becomes virtually barren with few plants scattered along the high-water limit (Nilsson et al. 1997). To ameliorate the negative impacts of littoral depletion, beneficial prey for fish that can tolerate the negative impacts of regulation have been introduced, including mobile crustaceans such as the mysid Mysis relicta and the amphipods Gammaracanthus lacustris and Pallasea quadrispinosa. A consequence of their introductions has included competition with fish and the fact that Pallasea acts as a vector for a nematode fish parasite (Cystidicola farionis). Non-native species of fish that are less dependent on littoral production have also been introduced, such as the American Lake trout in Swedish reservoirs in the late 1950s (slightly later in Finland). Recent experiments involving reservoir fertilization constitutes another attempt to improve the fishery in these nutrient-limited systems. In these experiments, N and P were added to local areas in a reservoir in the catchment of the Indal River and allegedly improved the condition (weight-to-length relation) of Arctic char (Milbrink et al. 2003). Whether large-scale fertilization of reservoirs is feasible and to what extent such management would influence other biota is presently not well understood.

8.1.3.3 Urbanization Urbanization has recently been shown to be a serious modifier of stream ecosystems that involves impacts on channels and flows (Paul & Meyer 2001; Walsh et al. 2005). For example large impervious surfaces lead to more rapid runoff without passing through soils to the same degree as in natural streams. Urban streams also tend to have high nutrient, metal and pesticide levels, leading to negative responses by stream life. However, urbanization has rarely impacted the region’s rivers due to the relatively low human population density, except for St. Petersburg.

8.1.3.4 Peat Extraction The most prominent effect of peat mining on freshwaters is an increase in N concentrations and, in most cases, pH and alkalinity. In the early ‘ditching phase’ high POM concentrations also occurred. A survey in northern Sweden showed that benthic invertebrates can be favoured when the proportion of mined land is <4%, whereas they are clearly depressed compared to reference sites when this proportion is high (Olsson & Bystr€om 1991). Fish, in particular 0+, are

304

reduced in affected streams at altitudes <250 m asl. Ditching of waterlogged peatlands leads to altered habitat structure and changed water quality, including increased concentrations in aluminium and POM that suppress benthic organisms (Vuori et al. 1998).

8.1.3.5 Mining Mining affects freshwater ecosystems and has long been influencing watercourses in the region. Detailed mapping of geology, well-developed infrastructure, and rich minerals have sparked a recent increase in prospecting with subsequent findings of gold, nickel, copper, zinc and other metals. Lately, the search for diamonds has intensified, using the presence of strong diamond indicators such as Archaean rocks, low heat flow and thick lithosphere (Geological Survey of Finland). There is a growing concern about uranium. There are indications that the region has some of the world’s largest reservoirs of this much sought after substance and prospection has recently increased in Finland and Sweden by the international mining industry. There is a worry that the pressure will grow for mining uranium, which presently is on hold in Sweden, and if resumed might lead to political and environmental consequences that are difficult to predict. Extensive mining has strong environmental effects on freshwater ecosystems through toxic leakage and differential responses among organisms.

8.1.3.6 Industrial and Other Pollution Pollution is probably comparatively less than in many other European ecoregions, and serious impacts are relatively localized. Apart from urban sprawl, notably in St. Petersburg, with associated problems, and in mining areas, such as the Dal River catchment, it is important to mention at least one significant industrial centre. This centre is a

PART | I Rivers of Europe

limited geographical area in the western Kola Peninsula where the large copper–nickel smelter in Nikel, the nickel refinery in Monchegorsk, and ore roasting plant in Zapolyarnyi are located. Heavy metals and sulphur dioxide are emitted in large quantities and pollute local soils and freshwaters. The pollution effects decline exponentially with distance from the industry to background levels in soils at a distance of 200 km (de Caritat et al. 1997) and 30–40 km in aquatic ecosystems (Korhola et al. 1999).

8.1.4. Biogeography Following previous classifications of climate zones and plant biogeography, Petersen et al. (1995), in their review of Nordic rivers, recognized two biogeographic regions within the Fennoscandian Shield. One of them, the Southern mixed forest rivers group, encompasses southeast Finland (primarily the Vuoksi subcatchment of the Neva) whose streams are characterized as ‘low-gradient streams in mixed coniferous forest, heavily interspersed with clear or humic lakes, ponds and wetlands, which overlap the boreo-nemoral zone’. These streams tend to be short, connecting lakes, peat bogs and wetlands, in a landscape mosaic. The entire Neva could be viewed as a part of this class. The second group, the Boreal rivers group, includes the rest, whose streams can be regarded as ‘high-gradient streams in the coniferous and deciduous forests of the boreal vegetation zone’. European black alder (Alnus glutinosa) dominates riparian tree communities of group 2 streams (and other wet areas). Before turning to the specific rivers, a short account on the pearl mussel – often considered a flagship species – in the region is presented. Over several centuries, fishing for pearl mussels was destructive to their populations because little concern was paid to make the harvest sustainable. Pearl fishing is known to have occurred widely in rivers in northern Sweden and Finland since the early 16th century (Figure 8.5) FIGURE 8.5 Sketch made by Linnaeus during his trip to Swedish Lapland in 1732 showing a man lying down on a raft in the P€arl€alven river (‘Pearl River’), operating a pair of long-handled tongues to retrieve pearl mussels.

305

Chapter | 8 The Fennoscandian Shield

and each landowner had to deliver 100 unopened mussels yearly to the capital on the king’s order (Awebro 1995). Pearl fishing was a stately privilege between 1691 and 1723, but was not particularly lucrative and interest continued to be weak with occasional bursts of renewed activity. One such period started in the late 1800s and continued into the early 20th century. The P€arl€alven (‘the Pearl River’, a tributary to the Lule River) developed into a minor ‘Klondyke’ during this period. The overfishing of mussels in this river resulted in the prohibition of pearl fishing in 1914, but only in 1994 was a general ban enacted in Sweden. Although many pearl mussels appear to be poorly reproducing (only a third of the existing populations produce offspring in Sweden) and the species is listed as ‘vulnerable’, the region is considered a core population of global importance (the IUCN status is ‘endangered’). This listing is despite the fact that the number of sites having mussels has been reduced by 66% in Sweden and 75% in Finland in the last 100 years. The healthiest populations are currently found in rivers on the Kola Peninsula. The degradation of habitats for pearl mussels and their increasingly aging population structure suggest that the quality of rivers is deteriorating.

8.2. THE RIVERS 8.2.1. The Dal River 8.2.1.1 Physiography, Hydrology and Climate The Dal River (Swedish: Dal€alven) is the second longest river in Sweden, 520 km, arising near the Norwegian border with a catchment size of 29 040 km2. Two main branches in the upper part include the northern one, V€asterdal€alven, € which merges with Osterdal€ alven downstream of Lake Siljan (area: 290 km2, depth: 124 m). These two arms drain 73% of the entire catchment. The catchment is rich in lakes with 3600 lakes >0.01 km2. Large tributaries are Ore€alven and Lill€alven. The lower course of the river has a gentle gradient and flows through several large lakes (F€arnebo-, Hedesunda- and Untrafj€ardarna) in a landscape of habitat mosaics strongly influenced by flooding. Annual mean discharge at the outflow is 379 m3/s, with a maximum recorded at 2450 m3/s (Swedish National Encyclopedia). Based on their length, 63% of the 1962 running water objects in the Dal River are first order streams and 20% and 9%, respectively, are orders two and three (L€ ofgren et al. 2001). In the northwest, the landscape is mountaineous reaching a highest altitude of 1200 m asl. About 25% of the catchment is at an elevation >500 m asl. Three quarters of the land cover are predominately forest. The human population of the catchment is 250 000 (Swedish National Encyclopedia) equivalent to a population density of 8.6/km2. The geology of the catchment is characterized by gneisses and granites, and leptites are important and associated with the presence of ore in the east. In the northwest, Jotnian sandstone, dating back at least 1200 million years, is

common. Soils are predominately of moraine origin, which at Lake Siljan can be fine and rich in lime. In the lower catchment, that is in the southeast, below the highest postglacial sea-level (190 m asl), glacial sediments are widespread. The north–central parts are fairly sandy and quite barren, partly covered by nutrient-poor mires. Viewed from space, a 37-km diameter circular depression, named the ‘Siljan Ring’, can be seen in the centre of the catchment and believed to result from a late Devonian meteorite impact. The climate of the catchment, which largely coincides with the province of Dalarna, is characterized by relatively warm summers and cold winters, and reflects the general altitudinal gradient increasing from southeast to northwest. Winters are particularly harsh in the northwest, with an average January temperature of 11 C. The average July temperature is 12 and 15 C in the west and east, respectively. Precipitation in most places is 600–800 mm/year, but exceeds 1200 mm/year in the west, with August being the wettest month (Swedish National Encyclopedia). Duration of snow cover ranges between 80 and 200 days per year (SNA 1995) and annual runoff between 8 and 25 L/s/km2 with the highest values in the mountains (Tryselius 1971). Considerable amounts of nutrients are transported by the river to the sea. The Bothnian Bay annually received 4200 tons N and 150 tons P in the period 1990–2000 (Tr€ojbom & Lindestr€om 2002). The sources of these nutrients were primarily forests, including clear-cut areas and to a lesser degree agricultural activities and industries. Although sewage treatment plants contributed to the N load they did less so concerning P, which is reasonably well removed in sewage processing in Sweden. Over the last 50 years a highly significant increasing trend in the accumulated river water temperature (‘degree days’) can be observed, with the seven highest values being recorded after 1996. This changing trend is of great importance, since temperature is one of the most vital environmental factors to organisms, for example the spawning migration of salmon serves as an example (Dahl et al. 2004). Salmon arrival, especially that of females, to the river in the period 1960–2002 was strongly influenced by the temperatures of both the sea water and the river with fish ascending the river earlier in years with high temperatures. Discharge had no significant influence on migration and temperature effects were not seen in sea trout.

8.2.1.2 Land Cover and Human Impacts The catchment is 75% covered by forest, where different broadleaf species make up 10% and Scots pine and Norwegian spruce together the rest in roughly equal proportions. Most forests are managed for forest production (94%). Other land covers include wetlands (9%), agriculture (5%), high mountains (3%), and urban areas (1%) (L€ofgren et al. 1998). Artifacts show that people lived along the lower parts of Dal€alven 6000 years BP. People were resident here from the Bronze Age or early Iron Age. It is likely that hunting and

306

fishing were important along with agriculture in those days. Activities associated with mining and forestry grew in intensity and many hydro-works were established along the river and its tributaries. The Dal was an important vehicle for timber. For 100 years numerous streams and rivers were affected by disturbances associated with the timber transport, including damming, flushing of logs, and channelization. The total length of publicly available watercourses for timber floating was 3500 km, and in 1952, 30 million logs were sent down the river. Timber floating was discontinued in 1971, when log transport was transferred to roads. The Dal drains a mining-rich area that has been exploited since the Middle Ages. Although starting in the 9th century, mining increased in the 16th century and it remains high at Garpenberg mine today (1115 kilotonnes ore were processed in 2005) (Geological Survey of Sweden 2006). At the town of Falun, copper mining had been going on for a millennium but was discontinued in 1992. This area, including Falun, with its well-preserved 17th century mill is now a World Heritage site. Reflecting its mining history, the river brings considerable pollution to the Baltic Sea, primarily heavy metals. High metal concentrations have been recorded in lake sediments in the region (SNA 1992). Because heavy metals are more soluble in acid soils and waters, their presence is related to pH. Numerous streams, especially tributaries to Dal€alven in the southeast, carry high loads of copper, zinc, lead and cadmium. This is particularly the case where leakage from old mine deposits occur and historic mining sites are quite abundant. Nitrogen concentrations approximately double from 0.2 mg/L in the upper parts to near 0.4 mg/L near the mouth almost 400 km downstream (Tr€ ojbom & Lindestr€om 2002). The annual contribution of P and N to the Baltic Sea from the river was in the 1990s about 180 and 4000 tons, respectively. These amounts equal 0.5% of the total input to the Baltic. For both nutrients, the most important sources are forests (P 45%, N 37%) and agriculture (P 14%, N 19%). The industrial contribution for N (24% including effluents from sewage treatment plants) is significant (Tr€ojbom & Lindestr€ om 2002). Nearly half of the nutrient inputs to the river is fixed in lake sediments or emitted to the atmosphere and does not reach the sea. To counteract acidification, considerable areas have been limed in the catchment. Liming commenced in the late 1970s and many freshwater systems have been limed since. Currently, 150–250 lakes and 80 streams are treated with 15 000 tons CaCO3 per year. The Dal River is regulated, contributing 8% to Swedish hydropower (Swedish National Encyclopedia). There are 500 dams in the catchment (SMHI 1995). Twenty-six hydropower plants >1 MW are built on the main stem and on € the tributaries V€aster- and Osterdal€ alven (SNA 1992), generating 4000 GWh/year. Reservoir live storage, that is the percentage of the yearly discharge that can be contained in the reservoirs, is 26% (Dynesius & Nilsson 1994). At 125 m, € Tr€angslet dam on the Osterdal€ alven is the highest dam in Sweden, and water-levels (range 37 m) in the reservoir vary

PART | I Rivers of Europe

in vertical extent more than any other Swedish reservoir. The damming effect on river flow ranges 70 km upstream, and below the dam a 4 km canyon reach is left dry. Tr€angslet dam, and many other dams on the Dal (e.g. in the lake reservoirs of Siljan and Balungen), obstruct fish migration completely (Beier 2002). Being regulated, the river has a hydrograph that is much less variable than a free-flowing river. Peak flow in May, associated with snowmelt, is relatively low but still the highest. Typical for regulated rivers, winter flows are comparatively high. Fragmentation and other disturbances associated with river regulation also impact the ecology of the river.

8.2.1.3 Aquatic and Riparian Biodiversity The Dal is located just at the southern range of the Fennoscandian Shield. It forms a well-established biogeographical border traditionally named ‘limes norrlandicus’, ‘Norrland’ roughly being the region in Sweden to the north of the Dal River. Many organisms, especially southern species, have here their northernmost occurrences, including deciduous trees such as pedunculate oak and ash. More than a sharp division, limes norrlandicus is a climatic, topographic and biogeographic transition zone connecting the boreal coniferous region in the north with the deciduous mid-European region in the south. From a European ecoregion perspective, limes norrlandicus also forms the boundary between the Fennoscandian Shield and Central Plains ecoregions. Often in early summer the forests along the lower part of the river are flooded. These lower parts have great natural conservation value representing a swamp forest biotope that was formerly common in the region but which now largely has vanished. In these virgin forests considerable amounts of dead wood support a high diversity of insects and woodpeckers (including the white-backed woodpecker, which is now on the verge of extinction in Sweden). Many unique insects also live here. One example is the cinnabar-red, endangered (EN) flat bark beetle (Cucujus cinnaberinus), which has a stronghold in large aspen trees along the river. The area is also important for recreation, including hiking, angling, canoeing, and birdwatching, being only 2 h from Stockholm, the capital of Sweden. The area around F€arnebofj€arden is classified as a Ramsar site since 2001. Here multiple-channel rapids connect lakes in a diverse landscape characterized by wetlands that are often flooded, including riparian meadows, wetland forests dominated by alder or birch, peat bogs and mires. Counter to many other rivers in the region, the lower Dal flows over lime-rich bedrock that favours biodiversity. Some 270 species of higher plants, rare lichens, mosses and fungi are found here. Viola persicifolia, Letharia vulpine (wolf lichen) and the neckera moss (Neckera pennata) are examples of rare species. Lynx and otter are residents in the area. Several research institutes with interests in salmonids are € located at Alvkarleby near the mouth of the Dal. One of them is the Swedish National Board of Fisheries. Already in 1871

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Chapter | 8 The Fennoscandian Shield

€ a salmon hatchery was opened at Alvkarleby. The hatchery € was expanded when the falls at Alvkarleby were harnessed for hydropower in 1911–1915. Today, there are laboratories for ecological and behavioural research, and a modern production line of smolts at this site. Research has to a large extent focused on the effects of salmon and trout farming with regard to behavioural and genetic changes, asking whether differences between farmed and wild fish have genetic or environmental causes, and on the problems of genetic diversity loss in salmonids in general. Salmon returns have been monitored over the years at € Alvkarleby, showing that populations have fluctuated strongly during the last century. The pattern reflects well the general situation for the Baltic salmon over the last 100 years. The most dramatic decline in numbers followed when upstream migration was blocked and breeding areas destroyed when dams for hydroelectricity were built on the rivers. To compensate losses, a hatchery programme was initiated and enabled large-scale recovery. However, its success resulted in a renewed and intensified fishing pressure at sea that led to a new reduction in numbers. Around 190,000 salmon and 60 000 sea trout smolts are released at € Alvkarleby each year. Asp is a rare member of the Dal River fish fauna. The presence of this large globally red-listed cyprinid is restricted to small, localized populations in the lower part of the river (Artdatabanken 2006). In the Fennoscandian Shield ecoregion the species seems restricted to the Neva and Dal Rivers. The invertebrate fauna of the Dal is not thoroughly reported. However, numerous studies on specific questions and extensive monitoring of tributaries have been done. An interesting study is the classical work by Karl M€uller on the ‘colonization cycle’ of riverine insects. He studied the degree to which female insects fly upstream to lay their eggs, in that way compensating downstream displacement during larval life (M€ uller 1982). The study showed the major species flying along the lower parts of the Dal (at Gysinge and S€ oderfors), including the mayflies Baetis rhodani, Leptophlebia marginata and L. vespertina and the caddisfly Cheumatopsyche lepida, and to what extent they fly upstream. For the latter mentioned species, he found that out of a total catch of 11 507 individuals 77.5% were heading in an upstream direction in accordance with his expectations. A similar tendency was found for the Leptophlebia species, B. rhodani and the stonefly Nemoura cinerea. From his work, it is evident that netspinning caddisflies, such as C. lepida, and other filter feeders were particularly well represented in this part of the river, a fact that was attributed to rich food from lacustrine parts upstream. High abundances of filter-feeding blackflies in the lower parts of the river are reflected in recurrent biting problems encountered at cattle farms. Attacks of massive numbers occasionally have caused the death of cows, especially heifers, in this region. The notorious pest species Simulium reptans, named by Linnaeus, is an inhabitant of large rivers and seems responsible.

Flooding causes spectacular mass development of mosquitoes in the lower parts of the river. Ochlerotatus stichticus is the most common species, which is bloodsucking on mammals, including humans, and aggressive at night and day. Sweden has traditionally a highly restrictive legislation towards the use of insecticides. Nevertheless, due to the mosquitoes’ perceived severity, this region is thus far the only place in the country where active mosquito control is allowed, but tentatively only for a test period. A toxin, consisting of the bacterium Bacillus thuringiensis var. israelensis, often simply called BTI, is used to this end. The control agent is spread using helicopters. Some concerns, still unresolved, include whether a strong reduction in mosquitoes might upset important trophic links in the ecosystems in this area. The control programme carefully has followed possible side effects since BTI treatments started in 2000. The most widely distributed benthic macroinvertebrates in tributaries of the Dal, apart from chironomids and blackflies, are certain mayflies (B. rhodani, B. niger), stoneflies (Amphinemura sulcicollis, A. borealis, Leuctra sp. and Isoperla grammatica) and caddisflies (Rhyacophila nubila, Polycentropus flavomaculatus, Oxyethira sp.) (Malmqvist & Hoffsten 1999). Red-listed species are few. Due to low buffering capacity, many smaller streams are potentially vulnerable to acidification, particularly at altitudes >500 m asl. A comparison of data from 20 sites in 1990 with similar data from 1975 to 1981 suggested that in two such sites the fauna might have been negatively influenced in this way, whereas in most cases there was no indication of change (Lingdell & Engblom 1991). Although pollution levels generally are low today, concentrations of copper, zinc, lead and cadmium at polluted sites can be as high as 35, 1500, 16.5, and 3.4 mg/L, respectively (Malmqvist & Hoffsten 1999). A study of stream macroinvertebrates across >100 streams revealed that metal-polluted streams show drastic reductions in species richness (Malmqvist & Hoffsten 1999). On average, richness was only 44% of that expected from models built using data from unpolluted streams in the region. Some stream-living insects appear to suffer more from metal pollution than others, including several otherwise widespread species, such as the mayflies Ameletus inopinatus, Ephemerella aurivilli and Heptagenia dalecarlica, the stonefly Protonemura meyeri and the caddisfly Apatania sp., since these were completely missing from affected streams. Correlative analyses suggested that copper and zinc were the causative agents.

8.2.1.4 Management and Conservation Despite long-standing exploitation with dramatic impacts, the Dal has maintained high environmental qualities. One reason is probably the great diversity of unique freshwater habitats encountered across the catchment from the mountains to the sea and in the transition zone between the Fennoscandian Shield and the Central Plains and Borealic

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Uplands ecoregions. In a thoughtful review of the environmental status of the river, L€ ofgren et al. (1998) suggested (1) energy and transport systems, (2) land use, and (3) diffuse emissions originating from individuals and households should be incorporated in the management of the river. A ‘system shift’ in management would include a better use of energy (renewable; higher efficiency), more efficient transportation of goods and people, less use of harmful substances, and restoration of polluted sites. The county of Dalarna actively performs conservation management, including a number of specific projects to improve environmental quality across the catchment. For example abundant remnants of mining continue to pollute the region, but in 2003, a regionally adapted version of one of the Swedish national environmental quality objective (a nontoxic environment) was implemented with a time plan for identifying affected areas and reaching goals in terms of sanitation. Already, measures around the town of Falun have resulted in quality improvements. For instance, in the Lake Runn, a steady increase in Secchi depth and decreasing zinc concentrations have been seen over the last 15 years (Tr€ ojbom & Lindestr€ om 2006). There are currently three national parks and 168 nature reserves in Dalarna that cover almost 250 000 ha. These provide protection for about 8% of the county’s area including a large number of important freshwater habitats in the Dal catchment, including sections € in the main channel and the Osterdal€ alven arm.

8.2.2. The Ume River 8.2.2.1 Geomorphology and Hydrology The Ume River is one of the larger rivers in northern Sweden. It has two seventh-order main stems – the Ume and the Vindel Rivers – each 420 km long with a joint final eighth-order reach of 40 km. Its mean annual discharge at the mouth equals 431 m3/s, of which 184 m3/s belongs to the Vindel (mean, 1961–1990). The entire catchment area comprises 26 815 km2, of which 13 837 km2 is drained by the Ume and 12 630 km2 by the Vindel. The Ume has a number of large headwater lakes, the uppermost in the main valley being € Lake Overuman near the Norwegian border. Lake Storuman in the middle reach is the largest lake in the catchment. Before 1927 there was no road along this lake but from 1900 to 1930 there were regular steamboat runs over the lake. The largest lake of the Vindel is Lake Storvindeln in the upper reaches near the mountains. The Vindel also has a major tributary – the Lais River – with several large lakes. During the second half of the 1900s, the Ume was heavily impounded and regulated. Development started in 1951 and within about a decade most parts of the river were dammed and their flow regulated. Along most of its reach, the Ume now forms a series of dams and storage reservoirs or runof-river impoundments. At present, there are 19 hydropower stations on the former major rapids in the Ume and its tributaries, and the majority of lakes have regulated water-

PART | I Rivers of Europe

level fluctuations. The storage reservoirs experience an annual variation in water-level with an extreme low during early summer and an extreme high in mid to late summer. This variation is enforced to maintain a more or less stable flow through the hydropower stations during the entire year. The largest storage reservoirs in terms of vertical water-level fluctuations are the Gardiken and Abelvattnet with 20- and 18-m ranges, respectively. The creation of both of these reservoirs caused large areas of land to be inundated. The run-of-river impoundments have smaller variation in waterlevel compared to previous conditions (usually 1 m), but the water-level varies frequently and often reaches its low and high each day. This variation allows electricity production that matches the variation in demand during day and night. The main channel of the regulated Ume only has a couple of small rapids in the headwaters; both rapids have regulated flows. In contrast, the Vindel is free-flowing and only has a few old, small power stations in a couple of tributaries. The decision to keep this river free-flowing was taken in 1970 after one of the greatest environmental battles in Sweden. The river is still affected by hydropower production because downstream of the confluence with the Ume, the Vindel passes the Stornorrfors power station with a turbine capacity to use most of the Vindel discharge. This power station has a fall of 70 m and for several years it was the largest hydropower station in Europe. The Vindel has a typical nival flow regime with an annual low in late winter and annual high a couple of months later (early June) from melting snow and ice during April-June. The highest flow ever recorded (2000 m3/s) was in 1995 and the record low is 20 m3/s. The record high was a disaster for many inhabitants along the river because many houses were flooded and had to be evacuated, whereas others were protected by temporary dikes. The Ume is oligotrophic with generally low levels of P and N. In most cases, this means <10 mg/L for P and <250 mg/L for N. Levels of total organic carbon are <5 mg/L in the main channel but somewhat higher in tributaries. There is also a west–east gradient with values of P, N and organic carbon increasing towards the coast. The pH typically falls around 7 in the main channels but is lower in most tributaries. Sediment transport is comparatively low, especially in the Ume where most sediment is trapped in impoundments. Earlier, the Ume was famous for several large cataracts/ waterfalls. One of these cataracts, F€allforsen in the lower reach, was a natural obstacle for migrating fish. Therefore, during the most recent millennia, the Ume has not been producing salmon. ‘Recent millennia’ refers to the fact that crustal rebound, which during the last 8000 years amounted to 250 m, caused the coastline to recede by 150–180 km along the two main valleys. A few thousand years ago, anadromous fish migration potentially extended further upstream in the river. In its headwaters, the free-flowing Vindel forms one of Sweden’s most distinct inland deltas. Downstream of the

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Chapter | 8 The Fennoscandian Shield

delta there is a Kursu valley and lateral drainage channels, formed by meltwater during the deglaciation period. Lake Storvindeln is one of Sweden’s few remaining lakes with a natural range of water-level variation around 4–5 m. The extreme low-water levels are further lowered because of a boating channel blasted into the outlet threshold of the lake. Downstream, the river has an extremely irregular course with sharp bends and small rapids, depending on an irregular distribution of moraine formations. This area includes wide riparian meadows and long, narrow river lagoons, and a few larger rapids cutting through bedrock thresholds. At the former high coastline, the river has a large fossil delta and downstream of this several eskers and one of the largest dune fields in the region. Further downstream, the riverine landscape is characterized by high, steep banks, terraces and ravines, and large floodplains. Along most of its course, the river flows through sparsely populated regions. Most people live in the city Umea (population 111 000), situated between the confluence of the main channels and the sea. The second largest urban area is Lycksele (population 12 000) on the Ume 100 km upstream of the rivers’ confluence.

8.2.2.2 Land Use Patterns The river has a long history of reindeer herding, implying that reindeer herds were kept in alpine areas during summer and brought downstream over winter to graze on the extensive sediment terraces where pine heaths provided abundant lichen growth. During the past 500 years or so, the river valleys were successively colonized by farmers, beginning downstream and reaching the mountains in the 1800s. Most farms were in the vicinity of tranquil reaches with large, productive floodplains cleared for hay-making. Seasonal flooding fertilized these floodplains and made annual harvesting possible. Floodplain meadows were successively abandoned in the mid-1900s when artificial manure became available, and the impoundment of the Ume made further use of these meadows impossible. In the Vindel, many of the hay-meadows are currently developing riparian forests but in a few of them cattle grazing has been introduced as a means of recreating the formerly open landscape character and producing organic beef. One of the most recently colonized areas in the Ume, the Gardiken-Bj€ orkvattnet valley, only persisted for around 70– 80 years until the valley was flooded after filling of Gardiken reservoir in 1961. This reservoir destroyed several small villages and forced over 130 permanent inhabitants to resettle. Given the already sparse population in this mountain area, this was a substantial impact. For instance, the reservoir ruined a major part of the agricultural land in the upper Ume valley and closed the dairy in the adjacent village T€arnaby. The damming of this valley destroyed spectacular riverine and lake landscapes. The former Gardsj€ on lake was drained by a waterfall in a constrained channel, implying that during snowmelt water-levels rose quickly in the lake and natural

water-levels fluctuated 5–6 m. This variation produced a well-developed plant zonation and maintained the largest shoreline polygon field in Sweden. During the mid-1800s, timber became valuable as part of industrialization, commercial logging started, and the rivers were successively developed to transport logs. In the Ume, all tributaries and main channel reaches downstream of the conifer forest line were affected by logging (Photo 8.2). Briefly, rapids were channelized often by means of piers along their margins, side channels were blocked and main channels cleared of boulders by removal or blasting. Timber floating was maintained on the Vindel until 1976 and on the Ume until 1980. During the latter years, logs were floated despite the fact that the Ume was impounded. The run-ofriver impoundments did not interfere with timber floating, especially if logbooms were used, and flumes at the dams made log passage possible. During recent years, many of the stone piers remaining from the log-driving era in the Vindel have been removed and boulders returned to the channel bottoms. In addition, small dams have been removed and formerly dry side channels have been reconnected to the river. This has caused channels to become coarser and many riverine habitats (such as side channels and riparian zones) that were more or less disconnected for over a century are now rehabilitated (Nilsson et al. 2005a). To facilitate recovery of trout populations in the Vindel, spawning areas in several tributaries have also been restored. The connectivity of small tributaries has been improved by adjustments of road culverts for better fish passage. These restoration activities have led the Vindel to regain more aquatic and riparian habitats.

8.2.2.3 Aquatic and Riparian Biodiversity Biodiversity for most parts of the regulated Ume is radically different compared to its previous state. Storage reservoirs have poor vegetation restricted to the uppermost parts of the shoreline. These communities represent mixtures of species from aquatic and lower parts of natural shorelines such as Ranunculus reptans, and ruderals such as Poa pratensis (e.g. P. alpigena and P. irrigata) and Rorippa palustris. This vegetation varies in abundance depending on the duration of flooding (Nilsson & Keddy 1988). Most reservoir shorelines are barren. The fish fauna has been modified so that benthic feeders such as brown trout have decreased and pelagic feeders such as whitefish (Coregonus spp.) have increased. In most cases, fish productivity has decreased compared to pre-damming conditions and parasites have become more common. Run-of-river impoundments have relatively well-developed shoreline vegetation, but it is usually restricted to a narrow strip compared to that of free-flowing rivers. This vegetation is most similar to that of lakes with a zone of meadow-like vegetation at the top of the shoreline and further down Carex species (on fine sediments) or even barren ground (on coarse deposits). The vegetation is a result of

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artificial water-level fluctuations, but is also affected by ice conditions that differ compared to pristine conditions. In a free-flowing river, ice is formed at a relatively high level in autumn, and when flow decreases the ice settles on the lower riparian ground. In contrast, because of frequent water-level fluctuations, ice in run-of-river impoundments moves up and down throughout the winter. This movement is an erosive factor and contributes to shorelines along the main channel having scarcer vegetation cover than those in protected bays. Below the ice-affected levels, and because water-level fluctuations are often reduced in vertical extent compared to free-flowing rivers, the run-of-river impoundments may have abundant vegetation of aquatic vascular plants such as Myriophyllum alterniflorum, Potamogeton gramineus, Ranunculus peltatus and Sparganium spp. The fish fauna of impoundments is dominated by species preferring lentic conditions. For instance, salmonids have become rare, whereas species such as European perch and northern pike are now common. No other Swedish river has been the focus of so much ecological research as the Vindel, and the riparian and aquatic vascular plants and many of the aquatic invertebrates are well documented. The river flows through alpine terrain, mountain birch forests, various wetlands and coniferous forests. The riparian zones have a mixture of vegetation types, from crustaceous lichens on rocks to lush riparian forests, rich in herbs. The entire river has well-zoned riparian vegetation that is governed by the wide range of water-level fluctuations and calm ice break-ups. Storvindeln Lake is surrounded by a riparian forest of spruce and hardwoods, with a field layer of species such as Geranium sylvaticum, Maianthemum bifolium, Melampyrum sylvaticum, Vaccinium vitis-idaea, and Viola biflora. Outside the forest edge, Calluna vulgaris and species such as Bartsia alpina, Calamagrostis stricta, Deschampsia cespitosa, Parnassia palustris and Pinguicula vulgaris dominate the vegetation. Bryophytes are common. Closer to the summer water-level, there is a distinct zone of Carex juncella. Further downstream, the river runs through coniferous forests and cultivated areas. The aquatic vegetation is welldeveloped in many tranquil reaches and in most floodplain bays. A bay on the floodplain close to the former highest coastline has 30 species of aquatic vascular plants, including the rare Stratiotes aloides. M. alterniflorum, P. gramineus, P. perfoliatus and R. peltatus are common aquatics along parts of the river. The forests in the terrace landscape between Rusksele village and the confluence of the Vindel with the Ume are dominated by Scots pine heaths. The steep banks are often covered by mixed forest, and Norway spruce dominates in ravines. Agricultural land is usually confined to level areas, € but in Overr€ oda both the densely occurring ravines and the terraces in between have been transformed to agricultural land, creating an open, undulating landscape. The Vindel has many tributaries. The largest one, the Lais River, has high species density and a plant zonation similar to

PART | I Rivers of Europe

that along the Vindel. The middle Lais River presents welldeveloped boulder meadows, on higher levels with forest and on lower levels with abundant vegetation of Caltha palustris and C. juncella, and with some of the world’s largest populations of Taraxacum crocodes. Many smaller tributaries have headwaters in wetlands and riparian areas include several plant species (such as Sphagnum spp.) typical of peatlands. On average, rapids along the Vindel have the most species-rich vegetation, composed of a mosaic of different vegetation types. Usually, patches of both heath vegetation and herb-rich meadow vegetation are present. The Lina Rapids in the middle reach of the Vindel holds the Swedish record of riparian species density: 138 species of vascular plants have been found along 200 m of the zone between spring highwater and summer low-water levels. Recently, the plant diversity of riparian communities along the Vindel was shown to vary in response to the magnitude of flooding each year. While plant diversity of tranquil reaches is reduced by extended floods, turbulent reaches tend to suffer little loss of species. This difference seems to depend on fewer incidences of anaerobic conditions along turbulent reaches and suggests that turbulent reaches serve as diverse plant sources from which propagules might disperse to rescue depleted diversity in tranquil reaches after major floods (Ren€of€alt et al. 2007). Probably because of the low number of lakes, the Vindel is an excellent dispersal corridor and many alpine species extend their distribution far downstream. For example Angelica archangelica ssp. archangelica, Astragalus alpinus, Euphrasia frigida var. frigida and Pedicularis sceptrum-carolinum occur along most of the river but not, or only rarely, in the surrounding inland or coastal regions. The variation in downstream limits of plant distributions is not related to variation in seed buoyancy, suggesting that dispersal is more efficient than what appears from floating ability or that dispersal and establishment are obstructed in various ways (Danvind & Nilsson 1997). Downstream dispersal is not the only reason for occurrences of alpine plants in rivers far beyond the mountains, as a short growing season is a common feature in both the mountains and the riparian zone. In the latter case, the vegetative period is constrained by flooding in early summer and rain-induced floods later in the summer may lead to further reduction. Another pattern known for less than two decades is that plant species density also varies predictably downstream. In the Vindel, riparian vegetation in the main channel is most species-dense in the middle reaches, a pattern analogous with that suggested for ‘total biotic diversity’ in the river continuum concept. This peak in plant species density coincides with the former highest coastline and may be functionally related to a combination of biological and disturbance variables and geometric constraints on large-ranged species (Dunn et al. 2006). Tributaries of the Vindel show an opposite pattern with least species richness in the inland reaches where the Vindel has its peak (Nilsson et al. 1994). The Ume, as well as other impounded rivers in northern Sweden, also shows this inverted pattern of species richness.

Chapter | 8 The Fennoscandian Shield

The Vindel encompasses a special mixture of animals with northern and southern main distributions. For example the alpine area has populations of arctic fox and wolverine. These areas also comprise important breeding areas for ducks, waders, passerines, gallinaceous birds and birds of prey. The river is an important migration route for birds, and includes several important resting areas, for example in the € delta of Ovre Gautstr€asket Lake. The Vindel has important spawning grounds for Atlantic salmon and anadromous brown trout (so-called sea trout). A stretch of rapids in the middle reach of the river downstream of Rastrand village is a particularly important spawning area for Atlantic salmon. All fish must pass a low-flow channel and a fish ladder to make it upstream of Stornorrfors hydropower station. Rivinoja et al. (2001) using radio-telemetry showed that salmon have significant difficulties in finding the fishway; only a fourth of wild salmon and no hatchery-reared salmon managed to pass the dam at the hydropower station on their migration route to spawning areas in the Vindel. Further risks face the fish in connection with migrating downstream when many smolt and adult fish pass the turbines. In Storvindeln Lake all Swedish species of whitefish (Coregonus spp.) are present and in the headwaters of the river arctic char occur. Storvindeln Lake also serves as a feeding area for a large-sized population of brown trout that migrates to rapids further upstream for spawning. Wise management (catch and release and restricted licensing) during recent years has developed a popular fishing industry around this species and for the common arctic grayling.

8.2.3. The Torne River 8.2.3.1 Physiography, Hydrology and Climate The Torne River (Swedish: Torne€alven; Finnish: Tornionjoki) partially forms the political border between Sweden and Finland. In contrast to most other rivers entering the Gulf of Bothnia, it has a gentler gradient and no major falls. Its valley is fertile and has attracted extensive agriculture despite its high latitude; most of the river is well above the Arctic Circle. This can partly be explained by the favourable summer climate with frequent inflow of continental warm air masses from the east, regionally known as ‘the Russian heat’, especially in lower half of this 520 km long river. The catchment area is 40 157 km2 with 66% in Sweden, 33% in Finland, and <1% in Norway. The 322 km2 large lake, the Torne Tr€ask, at 342 m asl represents one of the river’s scenic source areas. The Torne Tr€ask is surrounded by snow-clad mountains reaching up to 1500 m asl and the Abisko Scientific Research Station, the flagship institution of the Royal Swedish Academy of Sciences on its southern bank. Over 1300 lakes >0.2 km2 are found in the catchment. The Torne has some large tributaries, including the Lainio River and K€ onk€am€a-Muonio River, which originate in the far north and in fact are larger than the Torne stem at their

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confluences; the Muonio River should be considered the main channel (Hjort 1971). The K€onk€am€a drains the mountain lake Kilpisj€arvi near the three-nation border between Norway, Finland and Sweden. In its middle reaches, the river is connected to the Kalix River by a natural cross-channel, the T€arend€o River, which carries a little more than half of the Torne River’s discharge to the Kalix River. Together, these rivers constitute the largest free-flowing river system in Europe outside Russia. The mean annual discharge of the Torne is 315 m3/s (period 1970–1997), but due to between-year variation in precipitation this mean fluctuates between 300 and 500 m3/s. The lowest and highest discharges during the period 1911–1975 were 45 and 3667 m3/s, respectively (SMHI 1979). Seasonal variation is also extensive, showing peak flow in May and June with monthly means of about 1000 m3/s and with a minimum from January to April at 100 m3/s. Most of the catchment bedrock dates back 1.6–2.7 billion years, a time when this region was part of the ancient Karelian continent. While bedrock in the upper catchment consists of Caledonian slate and granite-gneisses, that in the mid and lower parts are characterized by granites, quartzite and mafic volcanite. Limestone occurs frequently together with volcanite forming easily weathered alkaline rocks from which important minerals like calcium and magnesium contribute to the lush vegetation. Limestone is particularly found north of the town of Pajala, near Kolari and in the Ylitornio/Tornea area. The soils are largely a product of glacial processes and therefore show a dominance of moraine. Peat is common. A characteristic feature in the area between the Lainio and Muonio rivers is the extended eskers that were formed from material brought and deposited by glacial rivers. Sedimentary soils formed from deposited silt and clay are found in the Pajala and Kolari regions and widespread along the lowermost part of the river (Puro-Tahvanainen et al. 2001). The climate varies due to the large extension of the catchment. For example, the mean annual temperature in the lowermost part is +1 C where latitude and altitude are lower and the climate moderated by the proximity of the sea, but as low as 2.6 C in the upper parts (Elfvendahl et al. 2006). At 300 mm/year, precipitation at Abisko is among the lowest in Scandinavia. This is in stark contrast to the western part of the Torne Tr€ask and along the catchment towards the Norwegian border where precipitation reaches 1700 mm/ year. More than half of the precipitation in the upper catchment falls as snow. The smaller amounts to the east are caused by rain shadow. In the mid and lower catchment, annual precipitation ranges from 400 to 550 mm. Snow cover is present for 175 days near the river mouth but for >225 days in the headwaters. Slow forest growth signifies the harsh northern climate, and ice stays longer. The famous ice hotel at Jukkasj€arvi and its ice art use all their raw material from river ice from the Torne. Although ice thickness on the river is rarely <70 cm in winter, it shows considerable variation between years. Ice breaks up between 1–20 May each year. During particular

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melt-off conditions during ice break-up, problems may occur in river sections that have a topography such that the channel narrows after wider parts and where the ice thickness is significant. A choked river and severe flooding is commonplace. In some places levees have been built to prevent flooding. The Swedish Meteorological and Hydrological Institute has developed a model showing that the most useful parameters for predicting severity are the sum of minimum daily air temperature in April, ice thickness, increases in discharge and winter precipitation (Granstr€ om 2003). Along with wetlands, mires and other freshwater habitats (together 20%), forest is the most prominent type of land cover in the catchment (60% of the catchment) and two thirds are coniferous. As a consequence, forestry is regionally important despite the fact that annual growth is slow. Mires are used for peat harvest, especially in the Finnish part of the catchment, but the combined area is small and the environmental impact marginal in comparison with forestry. The human population of the catchment amounts to 80 000 (Nilsson 2006) with a population density of just 2/km2.

8.2.3.2 Land Use Mining around the Swedish city of Kiruna in the upper catchment is regionally important. A railway was completed by 1902 connecting the iron mines here with the ice-free port of Narvik in Norway. Wastes from the Kiruna mine (but not the ones in the adjacent Svappavaara mine) drain into the Kalix River. Mercury pollution causes problems locally in Lake Ala Lombolo in the Kiruna area that drains into the Torne River at Jukkasj€arvi via Luossajoki stream. The impacts stem from previous pollution and still cause reduced invertebrate diversity and deformed mouthparts in larval midges living here (Hoffsten et al. 2006). The Torne was used extensively for timber transport, but here the work was partly an international collaboration with common interests between Sweden and Finland. These floatways had a joint length of 580 km with additional national lengths of 900 and 950 km on the Swedish and Finnish sides, respectively. Timber floating in the Torne was discontinued in 1971. People in the valley form a cultural unity sharing, among other things, a unique language: me€ankieli, a variety of Finnish that has received minority language status in Sweden. The impact from the construction of floatways was caused by the homogenization of bottom substrates, increased erosion of fines, obstruction of side channels, and decreased channel complexity, all with likely negative consequences for fish and other life in the river. Among the impacts of the timber floating was also the removal of the classical fish catch constructions that were built as bridges reaching out from the banks towards the centre of the river. In recent decades attempts have been made to restore some of the alterations caused by log driving. Water chemistry, at Mattila near the mouth of the river (SEPA database hosted by SLU, Uppsala), shows low ionic contents and dynamics influenced by the snowmelt hydro-

PART | I Rivers of Europe

graph. Average conductivity over the last 35 years has been 40 mS/cm but shows considerable seasonal variation with winter values 50 mS/cm and a minimum of 24 mS/cm in June. The water is low in colour but in connection with the early phase of the spring flood, that is in mid-May during the local meltwater runoff, a strong peak in colour associated with TOC is evident. The pH is circumneutral in the main channel with the highest values in summer. Nutrient levels in the river are generally low. Human impact in terms of addition to background loads is small, particularly in the upper catchment, and represents only 13% and 12% for P and N, respectively (Elfvendahl et al. 2006). Average concentrations of total P (1969–2005) and N (1987–2005) measured 20 and 350 mg/L, respectively. Even if concentrations appear low, the amounts of N transported to the Bothnian Bay are increasing. From 1969 to 2004, the N load increased by about 60–5600 tons/year. Phosphorus loads remain largely constant at slightly more than 300 tons/year. Tributaries of the Torne have been limed. This practice has been discontinued, however, probably because of growing insight that the acidity present has a natural origin and is not anthropogenic. Liming not only risks to alter the natural structure of aquatic animal assemblages (Dangles et al. 2004) but also has negative effects on riparian and wetland vegetation, especially that of Sphagnum mosses and Hepatophyta. The Torne is often considered one of the few unregulated large rivers in Sweden, but two tributaries are regulated for hydropower: the Tengeli€onjoki in Finland (producing 43 GWh/year) and Puostijoki in Sweden (6 GWh/year). In Sweden, a smaller hydropower plant also is present in the main channel of the river at Kengis, but there is no damming and <25% of the flow is used at this plant. One might therefore conclude that the river is unaffected by fragmentation caused by damming. In the 1950–60s, as one of three technological alternatives of exploiting the hydropower of the Kalix and Torne rivers, the possibility of turning the flow direction was investigated. The current river channels would then have lost half of its current discharge to a tunnel from Lake Torne Tr€ask draining westward to the Atlantic at the Rombak Fjord in Norway, encompassing a drop of 375 m. Fortunately, considering the great risk of enormous impacts on the environment, none of the plans were ever realised (Johansson 2006). Agriculture along the river is most extensive in the lower parts and includes cattle farming (primarily for dairy production), ley and pasture, in addition to a few cereals (rye and barley) and potato. Riparian flat land was cleared extensively in the past for hay-making. The deposition of river-borne sediments during flooding rejuvenated annually the alluvial soils between the high and low-water levels. Today, these habitats are either used for grazing or no longer used and overgrown.

8.2.3.3 Aquatic and Riparian Biodiversity The Torne is the most important wild salmon-bearing river in the Baltic. Its salmon has not only a unique value from a

Chapter | 8 The Fennoscandian Shield

conservation perspective but is also an economic resource for commercial fishery and sport fishing. At Kukkola and Matkakoski, two large rapids in the lower river, the banks are intensely frequented by rod-fishing anglers both on the Swedish and Finnish sides of the river. In the Middle Ages salmon fishing was already important here and taxed both by the Church and the Crown. Old documents show that in the middle of the 16th century the catch was between 10 and 90 tons per year. In 1562 the catch was 725 barrels, corresponding to 82 tons (Tuunainen et al. 1979). The method to capture salmon was by towing a seine net between two boats. In the 17th century, a new more efficient technique was introduced involving the building of pilework fences tightened with wickers that guided the salmon into traps. These constructions were locally named pator (singular pata). Reports from the 16th to the 19th centuries show large variations between yearly lows around 50 tons and highs reaching 400 tons. A dramatic reduction in the 1940s was probably related to intense fishing pressure at sea and in the 1950–60s catches were reduced to merely 20 tons per year reaching a low in the mid-1980s at not more than a few tons. Since then the population has recovered somewhat, especially following the good years of reproduction in 1991 and in 1996–1998, but is still probably negatively affected by intense fishing pressure and by environmental problems in the Baltic. Another backlash has also been the M74 syndrome, a reproduction disorder in salmon that possibly is related to a deficiency of vitamin B1 (thiamine) that increased in the early 1990s. The disease has negatively influenced the Baltic salmon, including the Torne population.

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As one of the few remaining sizeable wild populations in the region, the salmon of the Torne have great importance. The low-gradient of the river allows salmon to migrate and spawn up to 450–500 km from the sea, further than in any other Baltic river. Upstream migration takes place during the summer and the first ones to migrate are largest and assumed to include those that cover the longest distances upstream (Karlstr€om 2002). Spawning takes place in September–October with spawning commencing in the upper river. Eggs hatch in spring and after 3 years (range: 2–4) the smolt descend to the sea, forage there and return 1–4 years later. Of the 25 fish species recorded, the sea trout and whitefish (Coregonus lavaretus) are of particular importance. The classical fishing of whitefish takes place during the upstream migration using large hand-held nets, which have an opening of 50–70 cm and a long handle. The net is swept slowly from upstream to downstream at special sites with known quality. At the Kukkola rapid (Photo 8.1) >3000 whitefish have been caught this way in a single day. The invertebrate fauna of the river shows similarities with that of other northern rivers in the region. Of the 23 Plecoptera species recorded in recent inventories, at least three redlisted species were found: Xanthoperla apicalis (NT), Isoptena serricornis (NT) and Nemoura viki (DD) (Malmqvist 1999). The presence of I. serricornis is interesting because it is only in the far north (in the Lule and Torne Rivers) that this species, whose larvae dwell in sandy reaches, can be found in Sweden. This is despite its relatively wide but rare occurrence in Western Europe as close as Jutland, Denmark, and it thus represents one of many species belonging to different taxonomic groups that have invaded this geographical region from

PHOTO 8.1 The long Kukkola Rapids in the lower part of the Torne River are attractive for tourism and traditional fishery (photo: Bj€orn Malmqvist).

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PART | I Rivers of Europe

PHOTO 8.2 The Vindel River (The Vindel Rapids) in winter. The deflectors along the rapids are constructions reminiscent from the timber floating era when they hindered logs from stranding (photo: Bj€orn Malmqvist).

the east. Another example is the ibis fly (Atherix ibis), a bloodsucking species that was first recorded in Sweden from the Torne but was shown later to inhabit mid-sized streams in this and adjacent systems (Malmqvist 1996). At these northern latitudes there are also many other biting Diptera. In snowmelt pools in May and June, large numbers of mosqui € at the Arctic Circle, Nilsson toes develop. Near Overtornea and Svensson (1995) noted that the larvae of 6 mosquito species, all belonging to the genus Aedes, attracted a number of predators to meltwater pools. Foremost were dytiscid beetles (21 species), but also hemipterans and other Diptera inhabited these ephemeral waterbodies in the catchment. The blackfly (Diptera: Simuliidae) fauna is rich and due to the northern location contains many taxa with circumpolar distributions. There is a strong but as yet unexplained tendency of northern species to be more frequently bloodsucking on birds than on mammals relative to blackfly species found at lower latitudes (Adler et al. 2004). The Euroasian beaver (Castor fiber) was reintroduced into Sweden in 1922 from the remnant Norwegian population after having been driven extinct at the end of the 19th century following excessive hunting. The species has subsequently expanded its range to most of the country but only reached the Torne recently where it is now firmly established. The non-indigenous North American beaver Castor canadensis is expanding in Finland following introductions in the 1930s when the two Castor species were believed to be conspecific. Since these species appear unable to live together and the North American species seems to outcompete the Euroasian one in Finland, it will be interesting and important

from a nature conservation point of view to see whether the Euroasian beaver will resist the American species (Halley & Rosell 2002). The flora along the Torne has been described by Nilsson (1999). His report portrays the area downstream of Lake Tornetr€ask, where the river flows through a flat landscape dominated by mountain birch forests and mires in its upper parts, followed downstream by spruce forests. Maximum riparian species density is found in the middle reaches of the river along long stretches of rapids where species such as Astragalus alpinus, A. frigidus, Bartsia alpina, Saussurea alpina, Pinguicula vulgaris and Primula stricta are found. In its lower reaches, the valley is wide with a series of deltas and large floodplains. The river, as a whole, includes many rare northern species, such as Arctophila fulva, Chrysosplenium tetrandrum, Polemonium acutiflorum and Thalictrum simplex ssp. boreale, as well as southern species, such as Butomus umbellatus and Carex elata. The summer concentration of chlorophyll a at Kukkola ranges between 1.5 and 3.2 mg/L, reflecting the relatively low nutrient levels (Puro-Tahvanainen et al. 2001).

8.2.3.4 Conservation The Torne clearly represents a highly important system. Its size, relatively high latitude, multitude of aquatic, riparian and wetland habitats and low human impact all contribute to its unique biodiversity. To sustainably safeguard these conservational values, the Torne is classified as a Natura 2000 area in the EU network together with the Kalix River. Both

Chapter | 8 The Fennoscandian Shield

rivers have national rivers status in Sweden. The largest lake in the catchment, Torne Tr€ask, is a Man and Biosphere reserve formed in 1986 and has important biological and geological values. Near the Abisko research station, a small (75 km2) national park was founded in 1909. In many places, for example near the tributary the Vittangi River, there are old-growth pine forests with trees 300–500 years old growing on glaciofluvial sediments that provide a strong sense of wilderness. These forests, often draped in hanging lichens, host many red-listed species like the Siberian jay and Siberian tit, two extremely cold-hardy birds. In line with the Water Framework Directive, the Torne is classified as an international river basin district with associated specific responsibilities. To this end a collaboration project (TRIWA) between the Lapland Regional Environment Centre in Finland and the County Administrative Board of Norrbotten in Sweden has been initiated to characterize its lakes and rivers, attain an overall picture of the ecological state of the surface waters in the area, and develop a common monitoring programme for both lakes and rivers in the watershed. This work is underway where one of the tenets is to develop a joint river basin management for the future. A progress report has recently identified particularly important aquatic environments for protection including the freely flowing main channel and the flooding riparian areas of the Torne and its tributaries (Elfvendahl et al. 2006). Among recognized threatened animals are salmon and pearl mussel, and among plants almond willow (Salix triandra) and myrinia moss (Myrinia pulvinata).

8.2.4. River Koutajoki 8.2.4.1 Introduction The Koutajoki system flows on both sides of the FinnishRussian boundary. The majority (80%) of the watershed is on the Russian side, and the Finnish part comprises 4915 km2 of which 4500 km2 belong to the River Oulankajoki subdrainage. The Oulankajoki has its sources in the municipality of Salla, north-eastern Finland, and it has a total length of 135 km. The two major tributaries of the Oulankajoki are the rivers Kitkajoki (1841 km2) and Kuusinkijoki (1006 km2). Kitkajoki flows into the Oulankajoki close to the border and Kuusinkijoki joins it just across the border, a few kilometers before the river drains into Lake Paanaj€arvi. Together these three drainage basins comprise 85% of the total catchment area of Lake Paanaj€arvi. Paanaj€arvi is a deep (max depth 128 m), elongated (24 km) and narrow (1– 1.5 km) fjord-like extension of the Oulankajoki. From Paanaj€arvi, the river, now called the Olanga River, runs through a series of 13 rapids over its 20-km course to Lake Pyaozero (782 km2). Another large lake, Lake Topozero (986 km2), discharges into Lake Pyaozero from the south. In 1960, the water-level of Lake Pyaozero was raised by 9 m to serve as the reservoir for the Kuman hydroelectric power plant. From Pyaozero, the river enters the White Sea through a series of

315

lakes and rivers, the easternmost of which, River Koutajoki, gives the name for the whole drainage system. The Russian part of the drainage system east of Lake Paanaj€arvi has been strongly modified for power production with three power plants and three large reservoirs. The Russian part of the system is largely uninhabited and although different parts of it have been, and still are, under heavy forestry practices, areas near Lake Paanaj€arvi remain in practically pristine condition. At the heart of the Koutajoki River system, about 5–12 km south of the Arctic Circle, is the Oulanka–Paanaj€arvi protected area, which consists of Oulanka National Park in Finland and Paanaj€arvi National Park in Russia, Republic of Karelia. These two parks cover an area of 132 000 ha. Since most research on the watercourses and other natural resources in the area has focused on the Oulankajoki–Paanaj€arvi subdrainage system, the rest of this chapter will mainly summarize research conducted in this part of the drainage system. The first signs of human settlement in the area date back to 7000–8000 BP. These ancient people were nomadic hunters and fishermen. In the Middle Age, the area was inhabited by Saami tribes who practised reindeer herding, fishing and hunting. Finnish settlers used the Oulanka–Paanaj€arvi area for reindeer herding and agriculture already in the late 17th century, but it was not until late 1760s before the first Finns settled permanently in the area forcing Saami people further north. People living in the Oulanka–Paanaj€arvi region developed close trade relations with other Finnish tribes living by the White Sea. Economic use of forests began at the turn of the 20th century, and the Oulanka–Paanaj€arvi–Olanga River was used for floating timber towards the White Sea. Forests in the present Oulanka National Park were subject to heavy timber harvesting and many of the rapids were dredged to facilitate log floating. The period of active forestry was, however, rather short. The centre of the permanent settlement in the area was the village of Paanaj€arvi, through which the main thoroughfare from the Gulf of Bothnia to the White Sea passed. The area is widely known by its natural beauty and, from the late 1800s onwards, tourism became a new livelihood for the local people. The area attracted up to 1000 visitors each year, among them Finland’s national artist Akseli Gallen-Kallela, whose paintings of the people, biota and landscape of Paanaj€arvi are now part of the national heritage of Finland. After World War II, Paanaj€arvi became part of the Soviet Union and the present border line was established. From that time until the early 1990s, the Paanaj€arvi area was visited only by Soviet frontier guards, while the Finnish part of the drainage system was under strong development. It has been stated that Paanaj€arvi is now in as pristine a condition as it was before the 1800s. The three major river channels on the Finnish side of the border are reputed for their scenic beauty, with the Rapid Kiutak€ong€as in Oulankajoki being the landmark of the area with 50 000 visitors each year. All three rivers

316

are famous for their recreational fisheries, and Finland’s second biggest winter skiing resort, Ruka (130 000 visitors during winter), guarantees a steady flow of tourists to the area.

8.2.4.2 Biogeographic Setting 8.2.4.2.1 General Aspects The Kuusamo Uplands, which the Oulankajoki system is part of, is said to be the best preserved part of taiga forest in Western Europe. In the biogeographical classification of Nordic countries based on terrestrial vegetation, climate and soil (Nordic Council of Ministers 1984), the area belongs to the North Boreal ecoregion. The Kuusamo Uplands are generally characterized by hilly taiga forests interspersed with numerous peat bogs and lakes between 250 and 450 m asl. 8.2.4.2.2 Paleogeography Between 1.8 and 2.5 billion years ago, there were several earthquakes and volcanic eruptions in the area and they produced volcanic rocks that now partly overlay the archaic rocks. The entire bedrock of the area has been affected by powerful tectonic movements and folding of the surface layers. The Earth’s crust cracked in many places some 1.5 billion years ago and the largest fracture zones were formed as a result of earthquakes: the riverbeds of Oulanka, Kitka and Olanga Rivers and the basin of Lake Paanaj€arvi. At that time, bedrock of the area began uplifting, a process that is still underway. The region is still seismically active and several modest earthquakes have been recorded in the area, causing faults along the shores of Lake Paanaj€arvi and Oulankajoki valley. The last glaciation, Weichsel, began in the Oulanka–Paanaj€arvi area about 115 000 years ago and it lasted until about 10 000 years ago. The landscape is distinctly striated as a result of tectonisms and active glacier processes, to the extent that local people talk about the ease of traveling through the landscape ‘lengthwise’ as opposed to ‘crosswise’. As the ice sheet expanded, it moved across the Oulanka–Paanaj€arvi area, eroding part of the bedrock beneath it, and carried away and eventually deposited the moraine material, which today covers the slopes and tops of ridges in the area. Some of the moraine material was stratified to form plateaus with ridges and drumlins in the direction of the moving ice. At the melting stage, the ice sheet started to retreat westwards and the territory became free of continental ice 9500 years ago. The glacier retreat was soon followed by the formation of vegetation. The original tundra-type vegetation gave way to boreal taiga vegetation. In the beginning of the post-glacial era there was only a 30–40 km wide and 100– 300 m high zone of highland in the watershed area separating the White Sea and the Baltic Sea, while at present this distance is 400 km, and the whole relief has risen >200 m in places (Koutaniemi 1999).

PART | I Rivers of Europe

8.2.4.3 Physiography, Climate, and Land Use 8.2.4.3.1 Landforms and Geology The Oulanka–Paanaj€arvi area is characterized by a highly variable relief. Most of the area is a plateau at an elevation of 200–300 m asl, and tops of the highest fells, most of which are on the Russian side, rise to >500 m asl. The course of the major waterways is determined largely by bedrock fractures, and the smaller streams and rivers also follow zones of weakness in the bedrock (Koutaniemi 1979). Oulankajoki River, Lake Paanaj€arvi, and Olangajoki River divide the area in the west–east direction. The relief of this part of the river is strongly tilted towards the east. As the river enters Oulanka National Park on the Finnish side, the water-level is 200 m asl, while the elevation of Lake Paanaj€arvi is 128 m asl, and of Lake P€a€aj€arvi 110 m asl. The 50 km long, 0.5–2 km wide and up to 200 m deep corridor-like valley extending from Lake Paanaj€arvi towards Kuusamo Uplands originates from tectonic movements and is manifested in west–east oriented gorges, canyons and depressions (Koutaniemi 1999). Bedrock of the Oulanka–Paanaj€arvi area is composed of Proterozoic schists, being characterized by quartzites, blackschists, dolomites and greenstones (Koutaniemi 1999). The schists are surrounded by the Fennoscandian Shield of the Archean basement, typically comprising nutrient-poor acidic rocks. The geological diversity of the Oulanka–Paanaj€arvi area, with frequent occurrences of volcanic and sedimentary rocks enriched in all trace elements, create favourable local conditions for the development of a highly diverse biota (Systra 1998). 8.2.4.3.2 Climate The climate of the Oulanka–Paanaj€arvi area is mildly maritime. Annual precipitation is 520–550 mm and one-third of it comes as snow. The fells of the area are the highest peaks between the Gulf of Bothnia and the White Sea, causing cloudiness and increased likelihood of rain. An associated phenomenon is packed snow that is a heavy load of snow on trees on the highest ridges during winter. The variable topography creates extremely variable microclimates in the Oulanka–Paanaj€arvi area. Compared to the upland plateau, climatic conditions in the Oulanka–Paanaj€arvi–Olanga basin are highly continental. In winter, cold air descends into the river valley and air temperature can be 2–5 C, sometimes even 10 C, lower than on the surrounding plateau. In summer, hot air stays motionless in the river valley, making the air warmer than in the uplands. South-facing slopes of the river valley are generally much warmer than the shady and moist north-facing slopes. The climate of the area is characterized by extreme seasonality. The annual mean temperature is around 0 C and the difference in mean temperature between the warmest (July) and coldest (January) months is almost 30 C. The first snow usually falls in early October and the winter lasts

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Chapter | 8 The Fennoscandian Shield

for 6.5 months. The snow cover typically exceeds 80 cm and air temperature can fall below 40 C, the all-time record being 48 C (January 1985). Lakes and rivers are covered by ice for about 6 months. A notable exception is Lake Paanaj€arvi which, due to its great depth, freezes over about 1 month later than other lakes in the area (Koutaniemi et al. 1999). Spring takes over in late April – early May when the snow begins to melt. In summer, around solstice, there is no darkness even at midnight, and this continuous daylight lasts for almost 2 months, causing arhythmic behaviour in many freshwater organisms (see M€ uller 1973). The mean temperature in July is +15 C, but in the river valley, temperature often exceeds +30 C in July and early August. The warm and light summer is very short and autumn begins already in September. 8.2.4.3.3 Land Use Patterns Historically, forestry has been the major land use in the Oulanka–Paanaj€arvi area. The most active period of timber harvesting was in the beginning of the 20th century, and signs of it can still be seen in forest structure (P. Siikam€aki, pers. comm.). Present-day agriculture in the area is modest. Just before World War II, agriculture around Lake Paanaj€arvi was intense, producing the largest crops of rye in all of Finland. An important change to the riparian landscape was caused by a management practice adopted by local people already in the 18th century, whereby riverside meadows and mires were artificially flooded to improve hay production. This practice diminished the amount of Sphagnum mosses in the bottom layer and removed trees and bushes, thus favouring plants suitable for fodder. This resulted in a 70% increase in hay biomass production, and was therefore of considerable economical importance to local people. As a by-product, this management practice enhanced the biodiversity of meadow vegetation. The use of semi-natural meadows for hay production ceased by the 1950s, leading to revegetation of the managed meadows by trees and bushes with an associated loss of biodiversity (Vasari 2000). The former, luxurious stage of vegetation can now only be witnessed in the Oulanka National Park where a few meadows are actively managed to enhance agricultural biodiversity. A major present-day land use in the area is tourism. Negative impacts of recreational use on nature are inevitable, and the per capita use-impact relationship is often curvilinear: at low levels of use, impacts on local vegetation and other biota are drastic, but they soon level off, provided that disturbance to vegetation is minimized by concentrating all use on trampling-tolerant environments (Cole 1992). The number of visitors to the Oulanka National Park now approaches 180 000 per year, and it appears that the negative impacts of the increasing recreational use can be effectively managed by the ‘concentrated-use’ strategy (Kangas et al. 2006).

8.2.4.4 Geomorphology, Hydrology, and Biogeochemistry 8.2.4.4.1 Geomorphology and Channel Forms The Oulanka River valley is a fjord-like formation extending north-westwards from Lake Paanaj€arvi. The valley proper is 30 km long, 1–2 km wide and the valley floor is 100– 200 m lower than the surrounding upland plateau. The Finnish section of the valley up to the Kiutak€ong€as Rapids consists of a NW–SE running fracture zone. East of Kiutak€ong€as, the valley is lower with a very gentle (0.2– 0.4) profile. Kitkanjoki and Kuusinkijoki valleys also follow fracture zones, but these valleys are much shorter, narrower and more abrupt in their aspect. A key post-glaciation process controlling the fluvial morphology of the Oulankajoki valley has been land uplift. The overall land uplift in the area has been 160–180 m, and it is an ongoing process, although only at a rate of about 1 cm/km per 1000 years (Koutaniemi 1979). Following deglaciation, huge amounts of gravel, sand and silt from glacier meltwaters were deposited on the valley bottom. At the time of melting of the continental ice, the bottom of the valley was covered by deep water that prevented the spreading of material transported by the glacier rivers (Koutaniemi 1987). Today, the main channel is kept relatively shallow and broad by the abundant bedload originating from the easily erodible sandy valley ill. In most of Fennoscandia, bedrock restraints the formation of meanders, but the lower parts of the Oulankajoki represent conditions favourable for river meandering. The meanders migrate continuously along the river channel, with a maximum rate of 2.5 m, and on average 0.7–0.8 m, per year. This means that each successive meander belt will travel a full wavelength at an interval of 350–800 years. The downstream movement of meanders is controlled by the severity of the snowmelt-induced flood in the spring. At the first phase of the rising flood, erosion is dominant, but as the flood retreats, accumulation is the governing process. The annual net balance of these two processes determines how much a meander belt changes each year (Koutaniemi 2000). 8.2.4.4.2 Hydrology Seasonal variation of discharge in the Koutajoki basin features a double peak typical of Finnish rivers. The highest floods occur in spring (typically mid-May), with a second, much less pronounced, late autumn (October) peak being caused mainly by reduction in evaporation. In Oulankajoki, the water-level in May is typically some 70 cm above the mean, whereas in October, the mean value is exceeded by only 5–10 cm (Koutaniemi 1979). The Oulankajoki has a mean discharge of 23 m3/s, and the peak discharge during the spring flood in late May is on average 102 m3/s. The highest-ever spring flood in May 1973 was 462 m3/s, that is 150-fold higher than the lowest discharge (3.1 m3/s; April

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1990) measured for this river (Koutaniemi 1987). Mean discharge of Kitkajoki River is 19.3 m3/s and that of Kuusinkijoki River about 9 m3/s. The peak flow in Kuusinkijoki approaches 60 m3/s, whereas in Kitkajoki it is only double the annual mean. The annual minimum flows occur during the winter, when the discharge of Kitkajoki exceeds that of Oulankajoki usually 2–3-fold. Discharge variability is overall much higher in Oulankajoki than in its tributaries. This is partly because of the rather abrupt topography of the river valley, but the main reason is the low percentage of lakes (4.7%) in its catchment, as compared to Kitkajoki (21.7%) and Kuusinkijoki (13.3%). Oulankajoki and Kitkajoki remain free-flowing, whereas Kuusinkijoki is slightly regulated, but the annual flow regime remains typical of boreal rivers with no diel regulation. The main hydrological factor in the area is the accumulation of snow during winter: snowmelt-induced floods may sometimes account for two-thirds of the annual discharge of Oulankajoki (Koutaniemi 1984). The magnitude of the spring flood is mainly controlled by the severity of the preceding winter: in very cold winters, precipitation and, consequently, snow cover remains low, resulting in lower-thanaverage floods in the spring. The spring flood re-structures the river valley each year, transporting enormous amounts of inorganic and organic material to Lake Paanaj€arvi, which has sometimes been called ‘a graveyard’ for trees fallen into the river from the undercut slopes of Oulankajoki (Koutaniemi & Kuusela 1993). Ice jams that often form in the tightest meanders may also cause dramatic local-scale re-structuring of the river channel (Koutaniemi 2000). During the last few decades, the flow regimes of these near-pristine subarctic rivers have been altered by broadscale climatological factors. For example Arvola and YliTolonen (unpublished) noted a close agreement between the NAO-index and wintertime precipitation in the Oulanka area during 1968–1996. This result suggests that snow accumulation and, consequently, flood regime of rivers in the Oulanka–Paanaj€arvi area are partly controlled by weather dynamics in the North Atlantic. Long-term discharge records of the Oulankajoki show that both the magnitude and timing of annual peak floods have changed during the same time period: peak floods are smaller and they occur more than 2 weeks earlier now than they did 40 years ago (P. Siikam€aki, pers. comm.). Because of its elongate shape, west–east orientation and great depth, Lake Paanaj€arvi is hydrologically exceptional among similar-sized lakes elsewhere in northern Finland. The theoretical retention time of the lake water is 5 months, but because the upper water surface behaves much like a through-flow river (‘epilimnetic river’, Koutaniemi et al. 1999), the hypolimnetic waters are changed only during spring and autumn turnover. 8.2.4.4.3 Biogeochemistry Based on their water quality, rivers of the Koutajoki system can be regarded as being in an excellent condition, although

PART | I Rivers of Europe

winter nutrient inputs have been considered to be ‘alarmingly high’ (Koutaniemi & Kuusela 2007). These relatively high inputs come from various non-point sources (cultivation, ditching of forests and peat bogs, aquaculture, tourism) but, owing to more effective wastewater management and reduced agriculture in their catchment areas, nutrient concentrations in Oulankajoki and Kitkajoki have decreased since the early 1980s (Arvola & Ylitolonen, unpublished). Lake and river waters in the area are mainly oligotrophic and, due to frequent occurrences of calcareous rocks, slightly alkaline. Peat bogs cover 45% of the catchment area of the Oulankajoki, resulting in brownish water (mean water colour 50 mg Pt/L, compared to <20 mg Pt/L in Kitkajoki) with a high content of humic substances. First to third orders streams in the system have, with a few exceptions, extremely clear water. Water chemistry of the two main channels, Oulankajoki and Kitkajoki, tracks seasonal and short-term variation in runoff (Arvola & Ylitolonen, unpublished.). The basin runoff of Oulankajoki changes drastically, that is, several orders of magnitude, during the spring flood and also after heavy rainstorms in the summer, resulting in pronounced changes in water chemistry. In Kitkajoki, by contrast, all changes in water chemistry are relatively minor and occur slowly. Of the long-term changes (1968–1997), most pronounced is the rise of spring values in pH and alkalinity, both of which decreased slightly in 1978–1987, but have thereafter recovered to the same level as in the 1960s. The changes have not been dramatic, although pH in Kitkajoki has increased by 0.25– 0.35 units, from about 6.9 to 7.2, in the period 1978–1997. These changes most likely resulted from a substantial decrease in SO4 and NO3 deposition in the area since the late 1970s. Similarly, P concentration (tot-P) has declined slightly but steadily since the end of the 1980s. Today, tot-P concentration in Oulankajoki typically varies between 5 and 15 mg/L, while concentrations in Kitkajoki and smaller tributary streams are even lower (Heino 2005). This change in nutrient loading during the last 15–20 years has resulted mainly from improved wastewater treatment and changes in land use patterns such as reduction in the amount of arable land and decreased use of fertilizers (Arvola & Ylitolonen, unpublished.). There are no long-term water quality data available for Kuusinkijoki. However, occasional measurements throughout the 1990s show that P concentration of the river water is somewhat higher in Kuusinkijoki (range of tot-P during summer base-flows: 8–23 mg/L) than in the two other subdrainages (Oulankajoki: 4–18 mg/L, Kitkajoki: 4–15 mg/L). It has therefore been suggested that since the level of anthropogenic disturbance, especially forestry and aquaculture, is much higher in Kuusinkijoki than in the other two rivers, Kuusinkijoki might pose a threat to Lake Paanaj€arvi (Koutaniemi & Kuusela 1993). This is conceivable, as Lake Paanaj€arvi receives >90% of its waters via Oulankajoki, and 16% of these waters originate from Kuusinkijoki. Nevertheless, the values measured by Koutaniemi and Kuusela

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Chapter | 8 The Fennoscandian Shield

(1993) in Lake Paanaj€arvi were not particularly high in 1990 (tot-P up to 13 mg/L) and were even lower in 1996–1997 (on average 3–8 mg/L; Koutaniemi & Kuusela 2007). Considering the generally improving trend of water quality in the Finnish part of the drainage system, nutrient loading from Kuusinkijoki should not present a major obstacle to Lake Paanaj€arvi and its biota.

8.2.4.5 Aquatic and Riparian Biodiversity During the late-glacial and post-glacial periods the isthmus between the White Sea and the Baltic basin was narrow, and even today, the headwaters of Oulankajoki and Kitkajoki are separated only by a narrow step (watershed Maanselk€a) from rivers running towards the Baltic Sea. It is therefore not surprising that the Oulanka–Paanaj€arvi valley has served as one of the main post-glacial immigration routes for eastern vegetation to Fennoscandia. This historical process is apparently still underway, as suggested by recent evidence from terrestrial insects: some insect species considered as ‘glacial relicts’ may in fact be quite recent invaders. Furthermore, the Oulanka–Paanaj€arvi area is the northernmost distribution range for numerous animal and plant species, and it has also received many immigrants of northern origin. Such an important role as a distributional corridor, together with the extremely variable topography and frequent occurrence of calcareous rock are the main reasons for the exceptionally high biological diversity for many organism groups in the area. One of the peculiarities of Lake Paanaj€arvi is that it holds several glacial relicts, that is species that colonised the area soon after deglaciation. An example of such a relict species is smelt, which occurs in Lakes Pyazero and Paanaj€arvi but not in the Finnish part of the system. Of particular importance are the crustaceans Monoporeia affinis, P. quadrispinosa and Mysis salemaai. Another relict species, G. lacustris does not occur in Paanaj€arvi, but has been found in Lake Topozero. These relict species have poor dispersal capacities: they do not disperse upstream and are therefore restricted to waters once accessible through direct water connections during deglaciation (V€ain€ ol€a, 1993). Lake Paanaj€arvi was invaded by these organisms when the White Sea basin reached the area following glacier retreat. Previously, M. salemaai was considered a sibling species in the M. relicta species group, but recent evidence using both molecular studies (mitochondrial DNA; allozymes) and multivariate morphometrics have shown that M. relicta sensu lato comprises several distinct species. M. salemaai is closely related to M. segerstralei, and mtDNA data indicate remarkably recent divergence between these two species (Audzijonyte and V€ain€ ol€a, 2005, 2006). The winter population of Mysis in Lake Paanaj€arvi is relatively high (50 individuals/m2 and 0.9 g/m2) for a northern lake (Hakala et al. 1993). In late summer, planktonic crustaceans are abundant in the stomachs of Mysis, indicating heavy predation pressure on these zooplankters. Thus, Mysis appears to have a pivotal role in the pelagic food webs of Lake Paanaj€arvi: it is potential prey for many fish

species, yet it may compete for food with the young, planktivorous stages of the same fish (Hakala et al. 1993). 8.2.4.5.1 River Plankton During a 1-year study, Arvola and Nurmesniemi (2001) found 89 taxa of planktonic algae in Kitkajoki and 62 in Oulankajoki. Almost 40% were diatoms, and flagellates were also abundant in both rivers. Overall, their findings suggest that these two adjacent rivers differ profoundly in terms of the nutritional value of river seston, with Kitkajoki being clearly more productive than the more humic Oulankajoki. Hentunen (1995) documented much higher densities of net-spinning caddisflies in the rapids of Kitkajoki compared to Oulankajoki. Similarly, the species composition of the net-spinning guild overlapped little among the two rivers, but whether this is related to river productivity remains unknown. 8.2.4.5.2 Periphyton and Aquatic Bryophytes A comparison of regional diversity of benthic diatoms across eight rivers in Finland, Soininen et al. (2004) showed that Oulankajoki with 230 taxa represents a ‘hot spot’ of regional diversity of lotic diatoms. Local taxa richness was also highest in Koutajoki with a mean richness per site of 60. A key to high diatom diversity and unique species composition in the area lies in the bedrock: most streams studied were highly oligotrophic but with relatively high pH (mean of 7.4) and conductivity (mean of 85 mS/m). Koutajoki also supports exceptionally high diversity of aquatic bryophytes. Virtanen and Muotka (1993) reported 51 bryophyte species (14 hepatics, 36 mosses) in the area, the present number being 56 species (R. Virtanen, pers. comm.). For comparison, corresponding values for other rivers in Finland vary between 22 (River Oulujoki) and 35 (River Tenojoki). Four of the 56 species recorded in the Oulanka– Paanaj€arvi subsystem are considered near-threatened and eight threatened (one critically threatened) in the Red List of Finnish species (Rassi et al. 2000). Another critically threatened species, Scapania carinthiaca, has been found in one small stream in Oulanka National Park. The record occurrence here of this semi-terrestrial species is the only known in Finland. Muotka and Virtanen (1995) studied the structure of bryophyte communities in Oulankajoki and its tributaries. Using long-term discharge records, they documented a gradient in species composition from frequently disturbed sites to more stable ones. They also found a consistent pattern of zonation of bryophyte species along a gradient from continually submersed to persistently dry conditions in small streams and lake outlets. An abrupt increase in species richness occurred at or just above the water line, where facultatively aquatic species tolerant of both submersed and exposed conditions formed the bulk of the community (Virtanen et al. 2001). The most stable sites were dominated by a few perennial species (e.g. Fontinalis spp.) capable of monopolizing space. Species composition in low-biomass sites was more variable, yet one

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growth form (small-statured species with high allocation to spore production) seemed to thrive in these highly disturbed environments. Muotka and Virtanen (1995) thus suggested that disturbance, either in the form of bed movement, waterlevel variation or ice scour, is the driving force of stream bryophyte community structure. In a recent study, Heino and Virtanen (2006) observed that the regional occupancy and mean local abundance of stream bryophytes in Koutajoki were positively correlated, and that the relationship varied according to bryophyte life form: the relationship was quite strong in truly aquatic species but much weaker in semi-terrestrial taxa. They suggested that the community dynamics of obligatory aquatics is governed by dispersal limitation, while habitat availability is the key factor for semi-terrestrial bryophytes. 8.2.4.5.3 Benthic Macroinvertebrates Similar to most other aquatic groups, Koutajoki supports the most species-rich benthic macroinvertebrate fauna of all Finnish rivers. In Heino et al. (2003a) study, the number of macroinvertebrate species (excl. Diptera) in Koutajoki (only Finnish side included) was 96, while it varied between 43 and 90 in seven other approximately similar-sized drainage systems in Finland. The mean local species richness in Koutajoki was 23.6 taxa per site, being only exceeded by streams draining Lake P€aij€anne in Central Finland (29.9 taxa, on average). Species turnover, that is among-stream variation in species composition, was clearly highest in Koutajoki. All the sites sampled for this study were headwater streams, and in another study including a wider variety of stream types and sizes, Heino and Mykr€a (2006) recorded a total of 169 macroinvertebrate taxa from 78 sites in Oulankajoki, Kitkajoki and Kuusinkijoki. The pattern of high taxonomic richness in the Oulanka–Paanaj€arvi system is particularly intriguing considering that freshwater organisms, with few exceptions, exhibit a general trend of decreasing richness with increasing latitude (Heino 2002). Figures mentioned above are based on strictly standardized larval collections, and a more thorough picture of species richness in an area can be obtained from provincial species lists based on a variety of collection methods. A potential caveat in such species list is, however, that they are not restricted to individual drainage systems but span whole biogeographic provinces. For the biological province of Kuusamo, such species lists are available for mayflies (Ephemeroptera; Savolainen & Saaristo 1981), stoneflies (Plecoptera; Kuusela 1996), caddisflies (Trichoptera, Laasonen et al. 1998) and blackflies (Diptera: Simuliidae; Kuusela 1992). Savolainen and Saaristo (1981) recorded 38 species of mayflies in Kuusamo, but an updated number in the Oulanka–Paanaj€arvi area is 41 (E. Savolainen, pers. comm.), with two threatened and two near-threatened species. Altogether, 28 species of stoneflies were recorded by Kuusela (1996) in Oulankajoki and its tributaries. An updated list of caddisfly species in the Oulanka–Paanaj€arvi area contains

PART | I Rivers of Europe

128 species (J. Salokannel and A. Rinne, pers.comm.), of which 13 are near-threatened and one threatened (Semblis phalaenoides) in Finland. The Trichoptera fauna is exceptionally rich, and the distributional limit for many taxa, with either the southernmost (e.g. Oxyethira lingstedti, Apatania forsslundi, Brachypsyche sibirica) or northernmost (e.g. Lype reducta, Plectrocnemia conjuncta, Notidobia ciliaris) occurrences in Finland being recorded here. Heino et al. (2002, 2003b) showed that streams of the Oulanka area differ from streams in other areas in Finland based mainly on higher values for pH, alkalinity and conductivity, and low values of P (see also Mykr€a et al. 2007). However, macroinvertebrate assemblages were much less predictable, overlapping rather heavily in species composition with other rivers in the north boreal ecoregion but with a set of indicator taxa with north-eastern distributions in Finland. 8.2.4.5.4 Fish The fish fauna of Koutajoki is rather poor, consisting of 18 fish species. Unlike for most other taxa, this figure also contains records from the Russian territory, and some of the species (Arctic char, smelt, three-spined stickleback, gudgeon) only occur in the Russian part of the system. A typical headwater stream in the area would contain 2–6 species, with brown trout, alpine bullhead, European minnow and burbot as the core species. By contrast, Kuusinkijoki, for example contains 11 fish species (Nyk€anen et al. 2004). Only one fish species (rainbow trout) in the system is non-indigenous, and even this species occurs as a non-reproducing fish farm escapee. Habitat selection, life history patterns, migrations and genetic structure of brown trout have been intensively studied in the Koutajoki (Huusko et al. 1993; Koljonen & Huusko 1993; M€aki-Pet€ays et al. 1997). Both stream resident, upstream migrants, and downstream migrants are found in the river. Monitoring of trout movement since the 1960s using mark-recapture methods has shown that most of the parr and smolt from the three Finnish rivers ascend to Lakes Paanaj€arvi or Pyaozero where they spend 2–4 years before their first spawning migration to home rivers. Practically all recaptures are from the river of tagging. Kiutak€ong€as Rapids in Oulankajoki, with a drop of 14 m in 200 m, was long believed to be a migration barrier for brown trout, but recent research using radiotelemetry has proved that during high flows trout can pass this barrier (Saraniemi 2005). In contrast, Jyr€av€a Rapids (Photo 8.3) on Kiutajoki with a sudden drop of 9 m is unpassable for trout, and smolts above this waterfall migrate upstream to Lake Kitka, and then back to spawn just above the waterfall. Genetic studies (Huusko et al. 1993; Koljonen & Huusko 1993) have shown that the stock from Kitka above Jyr€av€a deviates strongly from those in other rivers, and also from the one in the same river below the waterfall. The explanation for this difference goes back to the post-glacial history of the system. After deglaciation,

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PHOTO 8.3 Jyr€av€a Rapids in the River Kitkajoki. Jyr€av€a is a migration barrier for fish, mentioned in the text (photo: P. Siikam€aki).

Lake Kitka was first connected to the Baltic Basin but, due to post-glacial land uplift, this connection was cut off 8400 years ago. Then the point of discharge changed to its present position with waters running towards the White Sea (Heikkinen & Kurimo 1977). Similarly, the presence of the mitochondrial clade III, which is of Baltic origin, of the salmonid pathogen Gyrodactylus salaris on grayling of Lake Kitka is explained by the historical connection to the Baltic Sea (Meinil€a et al. 2004). Grayling in Karelian rivers draining the White Sea, including the Oulanka–Paanaj€arvi–Olanga system, are parasitized by a different clade (clade IV). Thus, these two clades are separated geographically by a few tens of kilometers, yet they remain unmixed, due partly to the sedentary habits of grayling, and partly to the 9 m Jyr€av€a waterfall acting as a natural barrier to fish migration (Meinil€a et al. 2004). The densities of juvenile brown trout in Kitkajoki and Kuusinkijoki have been monitored by the Finnish Game and Fisheries Research Institute from the mid-1980s onwards, and even longer in Oulankajoki. Based on these data, Huusko and Korhonen (1993) reported that the densities of young trout resulting from natural reproduction in these rivers are high to moderate. Densities in Kitkajoki below the waterfall and in the lower reaches of Kuusinkijoki (on average 0.57 and 0.75 individuals/m2, respectively) are superior compared to those in most similar-sized rivers in Fennoscandia. No long-term data are available from the Russian territory but sampling conducted in rivers draining Lake Paanaj€arvi suggests that these stocks are at least moderate (>0.20 individuals/m2 on average) (Huusko & Korhonen 1993). Overall, Huusko and Korhonen (1993) consider the spawning

population to be large enough to maintain trout production at or near its carrying capacity. In the Finnish territory, no marked changes in juvenile trout densities have occurred since the mid-1970s, although fishing pressure has increased considerably during that period, with 8000 licenses being sold each year (Saraniemi 2005). Researchers have expressed concern, however, about the increasing fishing pressure in Lakes Paanaj€arvi and Pyaozero that may become a threat for trout in Koutajoki. Furthermore, as the populations originating from different rivers are genetically differentiated and gene flow between the stocks is minimal (Huusko et al. 1993), any mixing of the stocks should be strictly avoided, as this might lead to a considerable loss of genetic diversity and elimination of locally adapted stocks (Koljonen & Huusko 1993). The fish fauna of Lake Paanaj€arvi is characterized by large numbers of piscivorous fishes: pike, perch, burbot, trout and char. This is probably one reason for the surprisingly low diversity and abundance of cyprinids in the lake, another reason being the scarcity of low littorals in this deep lake with an abrupt profile (Koutaniemi & Kuusela 1993). Using echo surveys, Huusko et al. (1999) showed that the pelagic fish in the lake were generally rather large and their size distribution resembled more that of unfished natural lakes than of exploited lakes. The main fish species in Lake Paanaj€arvi are vendace, whitefish, perch and smelt (Huusko et al. 1999). Many of the more than 80 small lakes and ponds in Paanaj€arvi National Park contain unique fish communities (Shustov et al. 2000). Most of these waterbodies are in deep depressions of the fault zones, and clear and rich in calcium. Many are deep (tens of meters) and isolated. Perch is the

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most common fish species in these lakes, and in some lakes they may grow large, 44–48 cm and 1–1.2 kg. Some of these lakes also contain dwarf-size trout or char, which begin laying eggs at the size of 40–55 g (Pervozvanskii & Shustov 1999; Shustov et al. 2000). An interesting ichthyological finding is an isolated population of ninespine stickleback recorded by Kuusela (2006) from a small lake (Lake Rytilampi, 0.45 km2) in Oulanka National Park. Here this species reaches the ‘world-record length’, up to 11.0 cm, and all individuals lack pelvic spines. Invasion of the lake by other fish species is prevented by a steep waterfall in the outlet stream. It can therefore be assumed that the ninespine stickleback population has remained isolated ever since deglaciation, that is for 9000 years. Studies on mechanisms underlying the peculiar morphology of these fishes are underway, but lack of predation pressure, together with sexual selection favouring larger males, are the most probable candidates (Kuusela 2006). 8.2.4.5.5 River Dynamics and Riparian Plants In Oulankajoki, spring floods carry masses of sand and gravel from eroded riverbanks to accumulation areas (Photo 8.4), and also directly destroy riparian trees and other plants, and all these effects are intensified by ice scour and the occasional formation of ice dams. As a result, floods destroy entire populations of riparian plant species but also create open gaps for new colonization, thereby facilitating the occurrence of species that are inferior competitors in more closed vegetation, but are able to withstand floods and/or quickly colonize newly created habitats. An example of a species dependent on river dynamics is Silene tatarica (Photo 8.5), which is a threatened,

PART | I Rivers of Europe

perennial species growing along the riverbanks. Its main distribution area is on the Russian steppes, and north-eastern Finland represents the north-western range of its distribution. It has only been found on three rivers in Finland, the Oulankajoki being one of them. S. tatarica grows in many habitats along a successional gradient from open, sandy habitats to almost closed, vegetated shores. On open riverbanks, the plant is sparsely distributed and low, whereas in less disturbed, closed habitats it grows tall. One individual may produce thousands of seeds during a growing season, and the seeds are able to float and germinate in water. The species does not spread vegetatively, and new populations are established only through sexual reproduction. Mature, flowering individuals have a long taproot with high tensile strength and underground dormant meristemes, which make them highly tolerant of disturbance by water movement and sand burial (J€ak€al€aniemi et al. 2004). New patches are colonized by a few individuals, potentially causing a population bottleneck, and the average dispersal distance is <50 m (J€ak€al€aniemi et al. 2005). Using molecular markers, Tero et al. (2003) showed that their sample sites along the Oulankajoki valley consisted of distinct subpopulations. They estimated a low level of gene flow between subpopulations, with a few long-distance (several kilometers) bidirectional dispersal events caused probably by fishermen or reindeer. Studies conducted on the Oulankajoki suggest that, although S. tatarica is classified as an endangered species in Finland, its populations in the Oulanka area seem viable (J€ak€al€aniemi et al. 2005; Tero et al. 2005). The other distribution areas of the species in Finland are strongly regulated, thus preventing the natural river dynamics and creation of open, vegetation-free habitats along the riverbanks. PHOTO 8.4 River Oulankajoki. An accumulation area of a meander in the lower part of the river (photo: by Leo Koutaniemi).

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PHOTO 8.5 Silene tatarica, a threatened vascular plant that is completely dependent on the river dynamics (Photo: Pirkko Siikam€aki (the present head of the Oulanka Research Station) who’s been leading a group of plant population biologists studying the colonization-extinction dynamics of the species in the Oulankajoki river valley).

8.2.4.6 Management and Conservation Most of this chapter has dealt with the Oulanka–Paanaj€arvi subsystem, simply because most information available for the Koutajoki comes from this particular area. The rest of the drainage system is within the Russian territory and has, for the most part, been strongly modified by man. In contrast, although the Finnish part of the drainage system is used for forestry, aquaculture and some agriculture, a large part of it is within a nature conservation area. Oulanka National Park on the Finnish side and Paanaj€arvi National Park on the Russian side are directly connected, with the river valley and the river–lake continuum forming the core of the area. Together these parks preserve one of the last remnants of unmodified taiga forests in Western Europe. The conservation status of the Oulanka–Paanaj€arvi region is good and threats to its biota seem relatively minor. Forests in the Kuusinkijoki subdrainage and in the northernmost parts of the Oulankajoki system are under commercial use but this is unlikely to constitute any major threat to river ecosystems. Due to increasing fishing pressure, especially in Lakes Paanaj€arvi and Pyaozero, fishing regulation at the watershed-scale, in close co-operation between the Finnish and Russian authorities, is needed to secure the future of brown trout in Koutajoki (Shustov et al. 2000; Saraniemi 2005). Although the number of visitors to Paanaj€arvi National Park is now <7000 per year (180 000 in Oulanka National Park), the recreational use of the park is likely to increase in the future. The first signs of increasing use have already been noted as slightly deteriorating water quality in those parts of Lake Paanaj€arvi that receive most

visitors (Koutaniemi & Kuusela submitted). Nevertheless, perhaps the greatest threat to Lake Paanaj€arvi and its surroundings comes from increased commercial use of forests adjacent to the park. Although these activities have not yet reached the immediate surroundings of the park, changes in land use patterns in distant parts of the catchment are likely to have an impact on the highly vulnerable and biologically distinctive small lakes and ponds in the Paanaj€arvi area. Such impacts are not restricted to sections immediately downstream, but may also have upstream repercussions, especially as many running water organisms are highly mobile, some of them (e.g. brown trout) exhibiting consistent migrations from lakes to the upstream river sections. Therefore, all land use practices adjacent to either one of the parks, and on either side of the boundary, need to be carefully organized to ensure lasting protection of this irreplaceable taiga massif for the future.

8.2.5. The Neva 8.2.5.1 Introduction The Gulf of Finland and Lake Ladoga arose after the last glaciation 12 000–13 000 years ago. Their connecting river, the Neva formed only 2000–2500 years ago, is the most recent breakthrough into the eastern part of the Gulf of Finland. Before that, the river reached the sea further north than today. The name Neva is generally reserved for the lowermost 74 km of the system, downstream of Lake Ladoga, from where the river falls only 4.7 m. The Neva

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catchment (281 000 km2) constitutes some 18% of the Baltic Sea catchment and is the largest in the region (Nezihovskij 1988). Its catchment extends from 55 to 64 N latitude, and from 27 to 37 E longitude. The Neva has the region’s largest discharge at 2530 m3/s. In the European part of Russia, the Neva is the fifth largest after the Volga, Pecora, Kama and Northern Dvina rivers. Its discharge equals the combined flow of the Dnieper and Don, despite its catchment area being three times smaller. The Neva’s mean runoff is 28.4 cm/year. Many large rivers flow into Lake Ladoga with the Volhov, Svir’ and Vuoksi being the most important ones. The Neva catchment is where the Scandinavian Shield ecoregion meets the Eastern Plains and Taiga ecoregions with significant parts in each. The drainage covers the southeastern part of Finland, the southern part of Russian Karelia, considerable parts of St. Petersburg and Novgorod Regions and small territories in Pskov Region in Russia, and Vitebsk Region in Belarus.

8.2.5.2 Physiography and Climate The Neva drains primarily the Ladoga-Onega hollow, Il’men’ Lowland (the Lovat’-Volhov area), and Valdai Upland (Msta River). The Ladoga-Onega hollow is a large, hilly plain with coarse glacial deposits. The soils are mostly sandy or peaty of low alkalinity. Highly acidic sod-podzolic soils with low humus content and podzolic-boggy soils predominate. The climate around St. Petersburg is moderately cool with short summers. Mean annual precipitation is 550 mm/ year and mean annual air temperature is 2.5 C (4 C in January; 16 C in July) (Nezihovskij 1973). In winter, the snow cover can reach depths of 50–80 cm (sometimes 1 m). 70% of the precipitation falls as snow and the average annual duration of snow cover is 113 days. About 52% of the annual precipitation evaporates. Lakes form 17% of the Neva catchment area, covering 1350 km2. Due to the long meridional extent of the basin, snow melts gradually, and hence, the water supply of the lower Neva remains more or less stable throughout the year. The moderating effect of Lake Ladoga also contributes to the flow stability. The Ladoga-Onega hollow is surrounded by low-altitude uplands. The Vetrennyj Pojas with an elevation up to 250–300 m asl situated in East Karelia near the White Sea is where one of the main source rivers, the Ileksa, originates. Precipitation here amounts to 50–60 cm/year and the annual mean temperature is 1.6 C (11.6 C in January and 16.4 C in July). Spruce forests predominate but a large proportion of the landscape consists of wetlands. Lakes make up 10% of Ileksa’s catchment with the largest lake being Vodlozero (334 km2) (Kaufman 1990; Soloveva 1973). The Il’men’ (Volhov-Lovat’) Lowland is formed at the bottom of an ancient periglacial lake and has an elevation of 18–50 m asl. The climate is temperate continental, strongly influenced by low pressures from the Atlantic, and characterized by high humidity, relatively mild winters, and cool

PART | I Rivers of Europe

summers (Il’ina & Grahov 1980). The average January temperature is 10 C, and the average July temperature ranges from 16.5 to 18 C. Average precipitation is 50–65 cm/year; spring, summer, and fall are all rainy. As a result of low evaporation and inflow of warm air masses, the region is wet with 5430 km2 of bogs and 3615 km2 of rivers. The lowland is bounded to the east by the Valdai Hills, considered one of most beautiful parts of the East European Plain. The Valdai Hills are 600 km long and 150–250 m (max. 343 m) high. The hills constitute watersheds for several rivers: the Volga, the Western Dvina (Daugava), the Volhov and the Dnieper. Bedrock consists of limestones, covered by clays, moraine and alluvial sediments. The frontier of the last glaciation was located along the south-eastern border of the Valdai Hills. Among the glacial moraines, kames and eskers, there are many depressions, some of them with lakes. There are also many long, narrow lakes in the ancient preglacial hollows.

8.2.5.3 Human Colonization The history of human settlement began some 10 000 years ago, when Finno-Ugric (Saami/Lapp) hunters and fishermen settled in the area. In the early Iron Age (2500–1900 BP), the southern Finno-Ugric tribes (Karelians, Izhorians) inhabited forested areas. Later, Scandinavians from the west and Slavish tribes from territories of the modern Ukraine and Belarus invaded the region. The Volhov River was a segment of an important water trade route 800–1000 years ago, connecting the Baltic and Black Seas. Other parts of this route included the Neva River, Lake Ladoga, Lake Il’men’, the Lovat’ and Dnieper Rivers. The area historically belonged to the KievRussian State from 862, and thereafter to the Novgorod Republic in 1136–1478. The Moscow Principality possessed the area between 1478 and 1610. The lower Neva was thereafter a part of the Swedish Kingdom (1611–1703). In 1703 Russians took the area back and built St. Petersburg at the mouth of the Neva. From 1712 until the revolution in 1917 St. Petersburg was the capital of Russia.

8.2.5.4 Landscape and Land Use in the Neva Basin Presently, 55–90% of the natural vegetation consists of coniferous or mixed forests, dominated either by Scots pine or Norway spruce. The deciduous component is generally composed of birch or aspen. Willows are abundant near water. Grasslands with common reed and different species of sedges occur in the large floodplains, for example along the Volhov and its tributaries and at Lake Il’men’. Sphagnum bogs with dwarf pines are common in the north. The forested component of the lower Neva catchment is 55%. Other land cover consists of 12% agricultural land, 13% wetlands, 12% waterbodies, 1% urban, and 7% other types. Agricultural areas are concentrated near the large cities (St. Petersburg,

Chapter | 8 The Fennoscandian Shield

Novgorod) and on the Valdai Uplands. In the Novgorod Region, forests occupy 40%, and agricultural land 16%. In Russian Karelia, the percentage of cultivated land is <5%. Although land in the Neva valley is not very productive, it is still used for farming, particularly for potatoes, vegetables, barley, rye, oat, milk and the pig industry (Sel’skoe hozjajstvo, ohota i lesovodstvo v Rossii 2004).

8.2.5.5 Geomorphology, Hydrology and Biogeochemistry We consider here the system Ileksa–Vodla–Svir’–Neva as the Neva main stem because the Svir’ (the outflow of Lake Onega) represents the largest subcatchment and has the largest discharge compared with the other two main tributaries, the Vuoksi and Volhov. The total length from the source of Ileksa to the Gulf of Finland (including Lakes Onega and Ladoga) is 940 km. The uppermost stretch of the Neva (Ileksa) flows primarily from north to south for 207 km. Downstream of Lake Vodlozero, it is called the Vodla and continues to flow south before turning west into Lake Onega, Europe’s second largest lake, a stretch of 175 km. From Lake Onega, the Svir’ continues southwest 224 km to Lake Ladoga. The lower Neva (downstream of Lake Ladoga) flows 74 km to the west. The width of the lower Neva ranges from 400–600 m to 1000–1250 m near the mouth. Water depth is generally 8–11 m with a maximum of 24 m in St. Petersburg (Nezihovskij 1973, 1981). The stream order of the lower Neva is probably 8. Average monthly water temperature reaches 17 C in July. The water is relatively clear (5–10 mg seston/L) and the average amount of dissolved minerals is 56 mg/L. Typical hydrochemical characteristics upstream of St. Petersburg have been reported as: pH 7; HCO3 28.5 mg/L, SO4 9.4 mg/L; Cl 6.3 mg/L; Ca 9.6 mg/L; Mg 2.7 mg/L; NO3–N 0.64 mg/L; PO4–P 0.012 mg/L; Fe 0.10 mg/L; BOD5 1.5 mgO/L; BODtotal 2.5 mg/L; CODMn 8.8 mg/L; CODCr 24.0 mg/L; NH4–N 0.26 mg/L. Total hardness is 0.60 meq/ L, oxygen saturation 90–100%, and conductivity 80– 100 mS/cm (Nezihovskij 1981). Conductivity in Lake Ladoga was 83–84 mS/cm (Petrova & Raspletina 1987), the Svir’ River, 50–60 mS/cm, the Volhov River 230 mS/ cm (summer) or 100–150 mS/cm (during floods) and in the littoral of Lake Onega, mostly 46–48 mS/cm. The Neva carries an annual load of 310 000 tons sediments into the Gulf of Finland (Syvitski et al. 2005). BOD5 is normally <2 mg O/L but is much higher (3–5 mg O/L) within St. Petersburg. The upstream part and the main tributaries of the Neva have generally soft and humic water (Kaufman 1990). For example in the Vodla River, pH was 6.6–6.8 in spring, and 7.0–7.2 in summer. The mineral content was 30–40 mg/L, HCO3 dominated, and mean BOD5 1.4 mg O/L. The timing by which different tributaries carry the highest amounts of water into Ladoga differs: small rivers (Olonka, Vidlitsa, Sjas’) peak in mid-April, the Volhov in the beginning of May, the Svir’ in the end of May, and the

325

Vuoksi in June. Although seasonal water fluctuations in the lower Neva are not extensive, no less than 295 floods have occurred in St. Petersburg since 1703, the most recent one taking place in March 2002 and the most severe one in 1824 when the river rose 421 cm above its normal level and over 300 people died (Nezihovskij 1973). The cause of catastrophic floods is a long west–east seiche formed by cyclones from the Atlantic passing the Baltic Sea. If the wind direction coincides with the direction of this wave, the waterlevel can rise suddenly in the Neva Estuary, the easternmost narrow part of the Gulf of Finland. The Volhov flows into Lake Ladoga from the south. Like the Neva, only the lower river is called by the name of the main stem. Upstream of Lake Il’men’, the longest tributary is Lovat’ (535 km). The approximate length of the Volhov together with the Lovat’ and Lake Il’men’ is 790 km. The Msta (445 km) runs from the Valdai Hills and flows into Lake Il’men from the east. The Selon’ (248 km) enters Lake Il’men’ from the south–west and is, like the Lovat’, primarily a plain river. The Msta and Lovat’ pick up sediment when traversing the flat plain of fine alluvial deposits called the Il’men’ Lowland and therefore carry much less transparent water than the northern rivers of the Neva. The discharge of the Volhov’s tributaries varies much more than any others of the Neva. For example the summer discharge of the Selon’ may be 11 times less than in spring. In upstream reaches of the Lovat’ the difference between minimum and maximum water-levels can be as great as 9 m. Snow generates the majority of the Volhov’s discharge, the share of rain being 20–30%, and that of groundwater 10–20%. The Vuoksi River is the third major subcatchment of the Neva. Although this river has many important features of importance for the region’s biodiversity, we refrain from a more detailed account here. The Vuoksi catchment is dominated by lacustrine rather than riverine environments. Large Finnish lakes, including Saimaa, Europe’s 4th largest lake harbouring land-locked salmon and a subspecies of ringed seal, are dominant elements. The fourth tributary of Lake Ladoga in size (after Svir’, Volhov and Vuoksi) is Sjas’ (260 km) that enters the lake from the south. There are also important canals, for example the ones connecting Lake Onega with the White Sea and Baltic (White Sea–Baltic Sea Canal which was opened in 1933) and with the Volga River along the Vytegra River (The Volga–Baltic Waterway, 1964). Prior to human impact, the water of the rivers entering Lake Ladoga generally had a low total content of ions and nutrients, especially of mineral P, but high levels of dissolved organic matter and silica. A report on the state of main tributaries by Trifonova et al. (2003) shows that the lowest total content of ions (15–45 mg/L) is typical of northern and north-eastern inflows. The pH in these rivers was generally <7 and the water colour dark (100–350 Pt mg/L) due to the extensively paludified catchments. The darkest water and lowest pH were observed in the Tuloksa River. Since the catchments of the southern and south-eastern inflows (the

326

Pasa, Ojat’, Sjas’ and Volhov) are composed partly of carbonate rocks, their total content of ions is much higher (52– 150 mg/L), pH 6–7, and in the Sjas’, Volhov and Neva even as high as 7.4–7.8. The highest concentrations of P were recorded in the Volhov and Sjas’ (up to 150 mg/L) and in some small rivers with extensive human impact in their catchments. In the large Svir’ and Burnaya (the lower reach of Vuoksi) rivers, total P levels were lower (36 mg/L) and in the northern and north-eastern inflows even lower (15– 24 mg/L) due to lower anthropogenic impacts. The trophic state of the rivers ranged widely from oligotrophic to highly eutrophic. Large lakes form a considerable part of the Neva catchment. Lake Ladoga is mesohumic oligotrophic and Lake Onega oligohumic and oligotrophic. The water of Lake Ladoga has a higher mineral content than that of Lake Onega. In contrast, the water of Lake Il’men’ is hard and strongly eutrophic. According to Sabylina and Martynova (2003), most of the inflow to Lake Onega is derived from the and Suna that contribute 60% of the total rivers Vodla, Suja runoff. The water in Lake Onega has low mineral content (on average 25 mg/L) and contains moderately humic organic matter (water colour >40 mg Pt/L, CODMn > 10 mg O/L, pH 6). Earlier the water quality was higher (colour 20 mg Pt/L, CODMn 5–8 mg O2/L, Corg 4–6 mg/L, TP 7–12 mg/L). Since the mid-1950s, local pollution and eutrophication have affected the Kondopoga, Petrozavodsk and Bol’saja Bays. To maintain the oligotrophic status of Lake Onega, the total P content in the deep pelagic parts of the lake should not exceed 15 mg/L. The average total P has not yet exceeded 8–10 mg/L. If pollution increases as expected, the final eutrophication level may be far higher than in Lake Ladoga because the average depth of Lake Onega is much less.

8.2.5.6 Aquatic and Riparian Biodiversity 8.2.5.6.1 Algae and Cyanobacteria More than 470 phytoplankton taxa (440 species) have been identified in tributaries of Lake Ladoga (Trifonova et al. 2003). The most diverse groups include Bacillariophyta (163 taxa, 42%), Chlorophyta (148, 30%), Cyanophyta (38, 8%) and Chrysophyta (34, 7%) with highest species numbers found in the largest rivers, that is the Neva, Svir’ and Volhov (181, 171 and 168 species, respectively). High diversity (120–150 species) was also observed in the Burnaja (Vuoksi), Sjas’, Olonka and Vidlica, while only 66–96 taxa were reported from the Uuksu, Pasa, and Miinola. In general, the southern and south-eastern inflows showed more diverse communities than the northern and north-eastern inflows. River phytoplankton consisted of >50% planktonic species and >40% benthic and periphytic forms, which is typical of riverine plankton in turbulent rivers (Trifonova et al. 2003). Maximum biomass of phytoplankton in Lake Ladoga was found in a bay near Sortavala in 1992–1995. Holopainen and Letanskaya (1997) found Aphanizomenon flos-aquae,

PART | I Rivers of Europe

Woronichinia naegeliana, Anabaena spiroides and A. lemmermannii to be the dominant cyanobacteria. Based on planktonic biomass, chlorophyll a and productivity, the pelagial of Lake Ladoga could be classified as mesotrophic. Eutrophication was obvious in bays, particularly in Volhov Bay. Drabkova and Viljanen (2000) established that phytoplankton biomass in Lake Ladoga was largely determined by Cyanobacteria and cryptomonads, constituting 62–85% of total algal biomass. Diatoms prevailed in near-shore parts influenced by large rivers. In the littoral of Lake Onega, 336 taxa of phytoplankton have been found (Raspopov 1973). 8.2.5.6.2 Zooplankton Because of its relative shortness, the lower Neva possesses mainly zooplankton originating from Lake Ladoga. Between Lake Ladoga and the Baltic Sea, zooplankton density decreases approximately 10-fold (Ivanova and Teles, 1996). Large and sensitive forms are gradually replaced by rotifers. In the Volhov Bay of Lake Ladoga, zooplankton tend to be dominated by small rotifers and crustaceans; in terms of biomass, the large rotifer Asplanchna priodonta, the copepods Eudiaptomus gracilis and some species of Mesocyclops and Bosmina prevail and have remained nearly unchanged over time (Lavrent’eva et al. 1997). In the northern part of Lake Ladoga, Polyakova et al. (1997) recorded a long-term decrease of calanoids and increases of rotifers and cladocerans, whereas in the central part of the lake the zooplankton community seems to have remained relatively stable for 40 years (Drabkova & Viljanen 2000). 8.2.5.6.3 Plants Local macrophytes in the lower Neva are scarce due to water depth and steep banks (Nezihovskij 1973). In the littoral of Lake Onega, 121 species of higher plants have been recorded (Raspopov 1973). The depth limit for macrophytes in this lake is usually 3 m, but reaches occasionally 10 m. 8.2.5.6.4 Invertebrates Most of the lower Neva (except near St. Petersburg) had good water quality into the 1950s (Baluskina et al. 1996). Its sandy and gravelly bottom used to be inhabited by filter-feeding caddisflies Hydropsyche nevae and H. ornatula, crustaceans Pontoporeia affinis and P. quadrispinosa, and oligochaetes Propappus volki. In muddy areas, natural pelophiles (Oligochaeta, Sphaeriidae) occurred. In 1994–1995, the original fauna only partly remained (Baluskina et al. 1996). At this time, typical taxa in little disturbed regions included the chironomid Cladotanytarsus mancus, snail Ancylus fluviatilis, caddisflies Hydropsyche sp., different Plecoptera, and the leech Glossiphonia complanata. In the cold (1–4 C) profundal of Lake Ladoga, P. quadrispinosa dominated in the 1950s, and the large relict species Gammaracanthus (Relictacanthus) loricatus was also found. Oligochaetes were represented by Stylodrilus heringianus, Lamprodrilus

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Chapter | 8 The Fennoscandian Shield

isoporus and Spirosperma ferox. In the sublittoral (15–52 m), Saduria entomon occurred. Orthocladiinae, Tubifex newaensis and the same oligochaetes as in the profundal were also common (Baluskina et al. 1996; Slepuhina et al. 2000). At least 403 macroinvertebrates have been found in Lake Ladoga (Stal’makova 1968) and 530 species in Lake Onega (Popcenko & Aleksandrov 1983). The fauna of Lake Onega is more similar to eastern rivers such as the Onega and Mezen’ but has fewer species of marine origin than Lake Ladoga. 8.2.5.6.5 Vertebrates The fish fauna in the lower Neva has many species in common with that of the Gulf of Finland (Kuderskij 1996). A total of 44 native species have been found, among them only 30 species in the lower Neva. Only smelt and river lamprey have commercial importance in the lower Neva, while in Lake Ladoga, vendace, smelt, pikeperch, common bream, roach and perch, are caught intensively. Sturgeon is virtually extinct and the stocks of arctic char, salmon and whitefish are in a critical state. Compared to 1988, the catches of salmon in Lake Ladoga have decreased more than 10-fold, those of whitefish by 50%, and those of smelt by 25–56%. At the same time, stocks of perch and pikeperch have increased (Kuderskij 2000). Vendace apparently does not suffer from intense human impacts, and like the smelt, it now has a leading role for fisheries in Lake Ladoga. Since the 1970s, significant structural reorganization of the community has taken place (Lavrent’eva et al. 1997). Some unusual fishes are found in the large lakes in the catchment. In Lake Vodlozero, a relict whitefish species Coregonus sardinella occurs, indicating an ancient connection between Lake Onega and the Onega River that flows into the White Sea (Kuderskij 1996). However, the systematic affinity of this species is controversial. In Lake Onega, a particular morph of fourhorne sculpin (Triglopsis quadricornis onegensis) occurs, as does a large morph of vendace (Coregonus albula kiletz). Several warmwater species such as asp and tench inhabit Lake Ladoga but are missing from the colder and more oligotrophic Lake Onega. Compared to other parts of the Neva catchment, Lake Il’men’ is probably one of the most productive with a fish stock of 20 kg/ha, which is 10-fold greater than that of Lake Onega (Il’ina & Grahov 1980). The main commercial fishes in Lake Il’men’ include perch, pikeperch, common bream, pike, and ziege. The present population of the Ladoga seal is about 6000 individuals (Medvedev et al. 1997, 2000). It is a relict from the glacial period and an endemic subspecies of the ringed seal included in the Red Data Books of Russia, East Fennoscandia and Karelia. In 1996, it was classified as vulnerable by IUCN. In Lake Saimaa, in the Vuoksi catchment, the Saimaa Seal is another unique lacustrine subspecies.

8.2.5.7 Human Impacts and Special Features The most important alterations of the Neva and its catchment result from (1) chemical contamination through industrial and urban activities, (2) engineering projects associated with navigation and flooding, (3) introductions of non-native species, and (4) overfishing. From 1989, a decline in industrial production in Russia connected with a deterioration of the economy somewhat reduced the intensity of industrial water use. (1) Industrial and urban activities. The Neva catchment has some of the greatest metropolitan areas in the ecoregion, including St. Petersburg at the mouth of the Neva (4.7 million inhabitants), Novgorod on the Volhov River (240 000 inhabitants) and Petrozavodsk at the western shore of Lake Onega (279 000 inhabitants). These concentrations of humans are bound to have affects on the river. St. Petersburg takes most of its freshwater from the lower Neva and Lake Ladoga. In the 1970s, the consumption was 5.2 million m3, that is 2.5% of the river’s discharge (Nezihovskij 1981). At the same time, 5.6 million m3 of untreated wastewater was pumped either directly to the river, or to the estuary. Sewage treatment plants were constructed only in the mid1980s. Compared to the lower Neva that has a relatively high discharge, its tributaries near St. Petersburg are less diluted and thereby more polluted (Nezihovskij 1981; Baluskina et al. 1996). This is shown in the most polluted areas by a missing or strongly depauperate benthic community represented by only pelophiles (Tubificidae, Sphaerium). In the profundal of Lake Ladoga, the abundance of P. quadrispinosa has sharply decreased since the 1950s, and G. loricatus disappeared (Baluskina et al. 1996). Recently, however, the density of Pallasea has somewhat recovered and even Gammaracanthus has been observed again (Drabkova & Viljanen 2000). In several bays of the lake, macroinvertebrates have gone extinct locally due to pollution from pulp and paper mills. The most polluted regions such as near the Sjas’ River near Pitk€aranta in the cucij Bay and the Hiidenselk€a Bay near Sortavala have S been reported to be slowly recovering, although the number of taxa remains low and morphological deformities occur in several animal groups. The total amount of wastewater discharged into Lake Ladoga in 1987–1988 reached 1.6–1.7 billion m3/year, of which 85% had been treated (Voropaeva 1990), and more than half derived from pulp and paper mills. The contaminants break down slowly because of the relatively low temperature in the lake. The Priozersk pulp factory in the north-western part of the lake had probably the most harmful impact to the lake but was closed in 1988. Other mills in Pitk€aranta, L€askel€a, (in the northern part of the lake), Svetogorsk (on the Vuoksi River) and Sjas’stroj (in the southern part) are still in use. Serious

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PART | I Rivers of Europe

eutrophication of the lake began in the middle of the 1970s when 7000 tons P polluted the lake yearly. The amount of organic substances reaching the lake after closing the Priozersk mill is 100 000 tons/year. In terms of absolute quantities, the pollution load is largest via the Volhov River. The relative stress may, however, be even higher in northern bays near the mills in Pitk€aranta and L€askel€a. In addition to eutrophying substances, the Sjas’stroj and Svetogorsk paper mills in 1985–1987 emitted 1130 and 1200 tons chlororganic substances per year, respectively. In the beginning of the 1960s, Lake Ladoga was an oligotrophic waterbody. The input of P was then only 2500 tons/year, and the concentration of total P 10 mg/L. In 1981–1982, the input already exceeded the estimated critical level of 7000 tons/year. The Volhov, Svir’ and Vuoksi were the main sources. The annual average content of total P has declined from 24–27 (1977–1980) to 20–22 mg/L (1988–1992). Nitrogen no longer limits plankton development (Raspletina et al. 1995). Saprobity and toxicity in Lake Ladoga increased during the 1970s and 1980s and so did phytoplankton biomass, whereas the populations of many sensitive species declined (Drabkova et al. 1995). Morphological deformities of invertebrates were observed in heavily polluted areas. The increasing environmental problems were caused by growing industrialization and economic development. The most adverse effects appeared to occur in isolated bays and near-shore areas. Despite the fact that the Svir’, Volhov and Vuoksi have similar annual discharge, the Volhov alone accounts for 40% of the P input of all the Lake Ladoga tributaries in spring (Wirkkala et al. 2000). Concentrations of P and N in 1998 were 55 and 925 mg/L, respectively, upstream of the Volhov aluminium and fertilizer plant, and 96 and 1003 mg/L downstream. These figures give an idea about the input into Lake Ladoga from the River Volhov, amounting to 60% of the total P and 40–50% of the N. The contributions from the Vuoksi and Svir’ were also high. Mean output via the Neva was equivalent to 34% of’ the total P input and 77% of N. Estimates from 1992 to 1995 showed that the total P input was 5050 tons/year and that of N 66 840, while more recent figures (1997–1998) point to an annual mean input of P and N of 3700 and 52 500 tons/ year, respectively, suggesting a continuing decrease. Rivers brought at least 3700 tons oil, 245 tons copper, 300 tons lead, and 30 tons cadmium to the lake in 1992 (Kuderskij 1996). In the lower reaches of Svir’, the content of phenols was 6, crude oil 2.6, and copper 2.8 times greater than stipulated. In the lower reaches of the Sjas’ near Sjas’stroj, the content of phenols exceeded the permitted value even by 100 times. Raspletina and Susareva (2003) characterized longterm trends in the nutrient regime of Lake Ladoga and its tributaries. As a consequence of intensive economic

development in the catchment, the mean total P concentration in the river input increased from 27 mg/L in 1959–1962 to 80–85 mg/L by the end of the 1970s and early 1980s. In the lower Volhov, the total P concentration was 230–160 mg/L. The total input of P into the lake thus increased >3.3 times (from 1800 to 6000 tons/ year). Since 1996, the mean total P content did not exceed the permissible concentration (50 mg/L) to maintain the lake in a mesotrophic state. The mean concentration of total N in the river input for the period of 1976–1998 was 800 mg/L, which was 30% higher than in 1959–1962. The input of total N from the catchment area was 9–16 times greater than the input of total P. In contrast to P, there appears to be no decreasing trend in total N input into the lake. Cattle and pig farming, as well as applications of fertilizers and pesticides in the catchment, have decreased since 1990 (Drabkova & Viljanen 2000). This may have contributed to a general decrease in total P input from 6830 tons/year in 1976 to 2300 tons/year in 1996. The total N inflow increased from 66 050 tons/ year in 1976–1979 to 80 000 tons/year in the 1980s, stabilizing at 77 000 tons/year in 1992–1995. In spite of the decline in anthropogenic loading during the past decades, no obvious changes in trophic status could be detected from the data on chlorophyll a and primary production. Although ecological conditions have stabilized in Lake Ladoga, the problem of improving its water quality is still urgent. In the 1980s, the population size in the basin of Lake Onega was 500 000, more than half concentrated in Petrozavodsk. The total water use was 160.8 million m3 (Kaufman 1990). Paper and pulp mills formed 66% of the industry. In 1988, Petrozavodsk emitted 50 million m3 wastewater into Lake Onega, Kondopoga 75.5, and Medve z’egorsk 4.9. At this time, 84% of the sewage had been treated. During 1975–1986, no substantial differences were observed in offshore lake hydrochemistry, except for some increase in colour and decrease in transparency. Total P content was constantly 0.09– 0.13 mg/L in offshore areas. In several bays, serious environmental hazards were registered, particularly near Petrozavodsk, Kondopoga and Medvez’egorsk. Lignin is a main pollutant of Lake Onega and Lake Ladoga (Kalinkina 2000). It is the major component of the effluent from the pulp and paper industry. The processes in pulp and paper mills consume large quantities of water, for example 38.9 million m3 of wastewater were discharged from such sources into Kondopoga Bay of Lake Onega in 1998. The lignin content after biological purification may be 340 mg/L in this wastewater, which implies that large amounts of lignin enter lakes and rivers each year. Lignin decay is slow and accompanied by a reduction of oxygen content in the water, increased BOD values and quantitative changes in the saprophytic microflora. Lignin has caused two

Chapter | 8 The Fennoscandian Shield

kinds of effects on zooplankton in Lake Onega. First, it stimulated the growth and increased secondary production. Second, its high stability and tendency to accumulate created a source of pollution due to its decay products (phenols and methanol). These effects caused at high contents (i.e. 0.5 g/L or more) high mortality of Cladocera, while at low concentrations (0.1 g/L or less), their abundance and biomass increased. In 1991–1996, the phenolic content in rivers flowing into Lake Ladoga ranged from 0.5 to 16 mg/L (Krylenkova 2000). Maximum contents were reported at spring floods in the Vuoksi, Volhov and Svir’. The phenolic load into Lake Ladoga reached a maximum (0.02 g/ m2 year) in 1993 and decreased to a minimum (0.006 g/ m2 year) in 1997, far above the maximum admissible concentration in Lake Ladoga at 1 mg/L. The highest annual-weighted phenolic contents in surface waters exceeded this boundary until 1995, indicating significant pollution. The most polluted parts were the northern and north-western archipelagos and the southern bays, both being close to urban and industrial regions. The input from rivers and mean load in the lake were at maximum in 1993 (3000 tons/year and 0.02 g/m2, respectively). There has since been a gradual decline in phenol content. cucij Bay in the north-western part of Lake The S Ladoga was influenced by wastewaters of the Priozersk pulp and paper plant for more than three decades (Raspopov et al. 2003). The ecosystem here was completely destroyed and considered ‘a dead zone’ with the water surface covered by dark foam with H2S odour. The plant was closed down in 1986 and the volume of effluents decreased from 59 to 0.9 millions m3 per year. After that, the upper part of the bay, which was most polluted, was isolated by a stone dam. In the following years a rapid recovery of the ecosystem took place. Biodiversity in general increased, and emergent, floating-leaf and submerged plants appeared gradually to the extent that by 1992 all types of macrophytes were present in the bay. Now the bay’s biological quality is mesotrophic. (2) Engineering projects to improve navigation and reduce flooding. One of the oldest dams in the Neva system was built in the mouth of the Volhov in 1926 for producing hydroelectricity. Downstream of Lake Onega, VerhneSvir’skaja and Nizne-Svir’skaja further dams were constructed mainly for ship transport. The lower reaches of the Suna and the outflow of Lake Vodlozero are also regulated by dams. The Volhov dam closed the migration possibilities for the Volhov whitefish (a subspecies of C. lavaretus) from Lake Ladoga to reach its spawning areas in the Msta (Il’ina & Grahov 1980; Kuderskij 1996). The Neva is connected with the White Sea, Volga River and Black Sea via canals. The oldest canals were built into the river delta to ensure river transport

329

to the castles of St. Petersburg in the beginning of 18th century. During 1703–1708, the upper reaches of Msta and Tvertsa in the Volga catchment were connected. In 1719–1731, an artificial waterway, connecting the Neva and Volhov along the southern shore of Lake Ladoga was constructed. During the period 1802–1810, this waterway was extended up to the mouth of Svir’, and in 1852, to that of the Vytegra, which is the present part of the Neva–Volga canal route. In 1861–1882 the old channel was already out of date. The new canal was located between the old one and Lake Ladoga. In the 20th century, the canals lost their economical importance because most ships moved along Lake Ladoga. Rytk€onen and Rumyantsev (2001) analysed the environmental risk caused by water-borne transportation in Lake Ladoga and the Neva. They concluded that connections between the Neva and Volga, as well as that between the Neva and White Sea, played an important role in the Russian inland waterway network. During the years 1980–1990, the annual transport volume was almost 30 million tons. After the disintegration of the Soviet Union, transport decreased to a low point in 1996. During recent years, ship traffic has increased; for example on the Svir’ it now exceeds the level before the crisis. The number of accidents causing oil release to the water in St. Petersburg has increased from 8 cases in 1995 to 30 cases in 2000 due to the strong development of the shipping. Devastating floods increased the need for control of the Neva. Levees were the earliest form of flood control and were first built to protect St. Petersburg. Construction of a modern flood defense system began in 1980 and was about 60–70% complete by the end of the 20th century. The complex includes 11 dams, 6 sets of sluice gates and 2 navigation passages. Unfortunately, even the existing incomplete parts have caused considerable accumulation of pollutants in Neva Bay, thereby completely cancelling the positive effects of the treatment works here. Apparently, the effort seems to have relieved the Neva from industrial effluents but, at the same time, failed to produce any noticeable improvement of the bay’s ecological state. (3) Introduction of non-native species. Several non-native species have been introduced into the Neva via the Volga–Baltic Sea canal, for example sterlet, ‘omul’ ’ (pollan), and ‘peled’ (northern whitefish) (Kvasov et al. 1990). Non-native carp and rainbow trout are cultivated, for example in the cooling waters of Kirisi Plant and elsewhere (Il’ina & Grahov 1980). In Lake Il’men’, the benthic crustaceans Paramysis intermedia in offshore areas and Gmelinoides fasciatus in the littoral are other non-native species that have established (Mickevic & Andreeva 2003). Slepuhina et al. (2000) reported that benthic habitats in shallow areas of Lake Ladoga changed markedly after the introduction of the amphipod G.

330

fasciatus from Lake Baikal. The high productivity, rapid spread and predatory behaviour of this species have made it the dominant species and it has, for instance, outcompeted the native Gammarus lacustris. The zebra mussel, now a serious pest species in North America, is another invader that reached the Neva Estuary (eastern Gulf of Finland) by the mid-1980s (Orlova & Panov 2004). (4) Overfishing. Although industrial and urban activities together with damming are responsible for strong negative effects on native fish populations, overfishing and illegal fishing are also seriously contributing to the decrease of valuable fishes (Kuderskij 1996). Fishing pressure increased particularly in the 1960s (except for salmon and trout, which were stressed already by then). Unfortunately, catch statistics have recently become unreliable.

8.2.5.8 Conservation The Kivac nature reserve (106 km2), situated 30 km NW of Kondopoga, is the oldest in the region. In 1931, it was set aside as a forest centre – a waterfall on the Suna being the symbol of the area (Belousova 1992). Along the lower reaches of the Svir’, the Nizne-Svir’skij nature reserve (established in 1980; 410 km2) is located. The purpose of this reserve is to protect the Svir’ Bay in Lake Ladoga and its surroundings (Sviderskaja & Hrabryj 1985). The Vodlozero and its vicinities are included in the Vodlozero National Park (580 000 ha). Several islands are protected in large lakes. In Lake Ladoga, the Valaam Islands (established in 1965; 3600 ha) in the northern part of the lake are particularly valuable because of their old forests (the percentage of forests older than 140 years exceeds 15%). The surroundings of the islands are important habitat for the Ladoga seal (Kravcenko & Sazonov 1992). The mid and upper reaches of the Ojat’, Pasa, and Sjas’ Rivers have been protected since 1979 because of their value for the spawning of salmonids (Sviderskaja & Hrabryj 1985). Several other areas having valuable bogs and watercourses between Lakes Ladoga and Onega and north are also protected (Hohlova & Belkin 1988).

8.3. CONCLUSIONS AND OUTLOOK In many respects, the rivers in the Fennoscandian Shield ecoregion are in better shape than the rivers in most other European ecoregions. This fact is in most parts related to its low population density and the relatively low intensity of land use in the catchment. Human population size and the intensity of pressure on nature tend to go hand in hand and the rivers in the ecoregion reflect this general picture. Moreover, due to the prevailing climate characterized by relativatively high wetness, running waters are regionally abundant, and the pollution situation is in most cases not serious. It should however, be mentioned that there are numerous environmental problems creating challenges for future developments in the ecoregion.

PART | I Rivers of Europe

Some of the ecoregion’s problems are no doubt serious, including (1) the urban sprawl in some areas generating the typical suite of problems associated with urbanization, that is increases in impervious surfaces altering hydrology and geomorphology, and increasing the loading of nutrients, metals, pesticides, and other contaminants due to the runoff from urbanized surfaces and via municipal and industrial discharges (Paul & Meyer 2001), (2) the fragmentation of rivers by dams interrupting normal dispersal processes and breaking up previously continuous habitats into disconnected pieces with negative consequences for biota (Dynesius & Nilsson 1994; Nilsson et al. 2005b). In addition, damming appears to seriously impact material transport, including that of silica (Humborg et al. 2006), with likely bearings for the ecosystems in downstream parts of the rivers and the Baltic, and (3) increasing physical and chemical changes to catchments due to intense forestry, mining and other activities, with repercussions for life in rivers and their tributaries. The problems are in most cases identified and management plans often exist, but sometimes it does not seem possible to reconcile conflicting interests of exploiters and those who understand that functional rivers are both necessary and an asset to society. It is particularly obvious when considerable economic values are involved as in the production of electricity or activities affecting large areas, like forestry and mining. The legislative activities of the European Union are however, promising and the implementation of the Water Framework Directive may lead to significant and rapid improvements across Europe. Despite pressure from a multitude of human impacts outlined in this chapter, the situation in the Fennoscandian Shield ecoregion is even improving, in some respects, as negative effects of environmental impacts become better understood, legislation is made more efficient and ruthless exploitation exceptional. Examples of positive effects include the radically decreasing deposition of sulphuric acid and the increasing areas under protection (e.g. in Sweden, most of the total area of nature reserves and national parks is in the northern part of the country and in the ecoregion described here). The ambition to restore streams and rivers in the region is also increasing, including the liming of acidified lakes and streams and restoring hydrological complexity in previous floatways for timber. Furthermore, the risks of losing valuable biodiversity have become obvious, leading to increasing awareness and conservation initiatives including compilations of national red-lists to aid local administrations in the protection of streams and rivers throughout the region. At the same time, since virtually all these pressures continue to be a threat and new impacts, including climate change (Figure 8.6) are likely, active conservation work to minimize damages remains a necessity. Biodiversity at higher latitudes may be more robust than at lower latitudes. Species here tend to have larger distributions, to be able to tolerate wide seasonal climatic fluctuations (Rapoport’s rule), and lower spatial turnover (beta

331

Chapter | 8 The Fennoscandian Shield

REFERENCES

FIGURE 8.6 River warming. The positive trend in number of annual P € water degree days [ ðtemp dayÞ] at Alvkarleby in the lowermost part of the River Dal. Data from the Swedish Board of Fisheries.

diversity). These are factors probably contributing to the relatively low number of high latitude species that have gone globally extinct. Running waters also tend to have a strong capacity of self repair once impacts have ceased. The extent to which changes caused by environmental impacts are reversible is, however, not very well understood but is likely to vary considerably depending on system and type of organisms. Particularly serious in this ecoregion is probably the complete loss of genetically unique stocks of fish, salmonids and other migratory fish in particular, whose populations have become fragmented or driven extinct due to the damming of rivers. Such losses are clearly irreversible. In the long perspective, according to current climate models, climate change may make southern Europe, and parts of other continents, less inhabitable for humans and human population centres may therefore gradually shift further to the north. Should this happen, the pressure on ecosystems, including those in the Fennoscandian Shield ecoregion, is likely to increase. Therefore, it is of utmost importance for river managers to focus not only on improving affected systems today and maintaining those that are in good shape, but also be prepared for accommodating more people at the same time as industrial wastes must be minimized and damming avoided. To maintain biodiversity, and associated ecological goods and services, it will also be important to ensure that all types of habitats in the region are well represented.

Acknowledgements The following persons offered valuable help with the compilation of data and comments on the manuscript for which we are greatly grateful: Andreas Broman, Dan Evander, Matti Hovi, Ari Huusko, Tomas Loreth, Anders Kinnerb€ack, Leo Koutaniemi, Kalevi Kuusela, Karl-Erik Nilsson, Janne Raunio, Cathy Reidy Liermann, Aki Rinne, Juha Salokannel, Berit Sers, Pirkko Siikam€aki, Ivar Sundvisson, Jukka Syrj€anen, Riitta Teiniranta, Tarmo Timm, Risto V€ain€ol€a and Risto Virtanen. The work was also supported by two research projects of Estonian University of Life Sciences: SF 0170011508 and SF0170006s08.

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Stal’makova, G.A. 1968. Zoobentos Ladozskogo ozera. In: Kalesnik, S.V. (ed). Biologi ceskie resursy Ladozskogo ozera (zoologija), Nauka, Leningradskoje otdelenie, Leningrad, pp. 4–70. Sviderskaja, M.D., and Hrabryj, V.M. 1985. Sohranim dlja potomkov. Osobo ohranjaemye prirodnye territorii Leningradskoj oblasti. Lenizdat. Systra, Y.J. 1998. Geological diversity: the main reason for the biodiversity of the Paanaj€arvi National Park. Oulanka Reports 19: 23–26. Syvitski, J.P.M., V€or€osmarty, C.J., Kettner, A.J., and Green, P. 2005. Impact of humans on the flux of terrestrial sediment to the global coastal ocean. Science 308: 376–380. Tero, N., Aspi, J., Siikam€aki, P., and Tuomi, J. 2003. Genetic structure and gene flow in a metapopulation of an endangered plant species Silene tatarica. Molecular Ecology 12: 2073–2085. Tero, N., Aspi, J., Siikam€aki, P., and J€ak€al€aniemi, A. 2005. Local genetic population structure in an endangered plant species, Silene tatarica (Caryophyllaceae). Heredity 94: 478–487. Trifonova, I., Pavlova, O., and Afanaseva, A. 2003. Comparative assessment of the ecological state of Lake Ladoga tributaries by their phytoplankton. In: Simola, H., Terzevik, A.Yu., Viljanen, M., Holopainen, I.J. (eds). Proceedings of the Fourth International Lake Ladoga Symposium 2002,University of Joensuu, Publications of Karelian Institute, pp. 260–265 Vol. 138. Tr€ojbom, M., and Lindestr€om, L. 2002. N€ arsalter i Dal€ alven 1990–2000. L€ansstyrelsen Dalarnas l€an 2002, Vol. 17, 14 pp. Tr€ojbom, M., and Lindestr€om, L. 2006. Samordnad recipientkontroll i Dal€ alven 2005. L€ansstyrelsen Dalarnas l€an 2006,Vol. 23, 110 pp. Tryselius, O. 1971. Runoff map of Sweden. Average annual runoff for the period 1931–60. In: Sveriges meterologiska och hydrologiska institut, Meddelanden, serie C, nr. 7. Tuunainen, P., Nylander, E., Alapassi, T., and Aikio, V. 1979. Kalastus ja kalakannat Tornionjoen vesist€oss€a. Riista- ja kalatalouden tutkimuslaitos, Helsinki. 1–81. V€ain€ol€a, R. 1993. Zoogeography of “glacial relict” crustaceans in northern Fennoscandia – a molecular systematic approach. Oulanka Reports 12: 109–113. Vasari, Y. 2000. The significance of flooded meadows for the vegetation and flora in Kuusamo. Oulanka Reports 23: 91–93. Virtanen, R., and Muotka, T. 1993. Stream bryophytes in Koillismaa (Ks), northeastern Finland. Oulanka Reports 12: 57–69. Virtanen, R., Muotka, T., and Saksa, M. 2001. Species richness – standing crop relationship in stream bryophyte communities: patterns across multiple scales. Journal of Ecology 89: 14–20. Voropaeva, GM. (ed). 1990. Puti soversenstvovanija prirodopol’zovanija v bassejnah bol’sih ozer na primere Ladozskogo ozera, Nauka, Leningradskoe otdelenie. Vuori, K.M., Joensuu, I., Latvala, J., Jutila, E., and Ahvonen, A. 1998. Forest drainage: a threat to benthic biodiversity of boreal headwater streams? Aquatic Conservation-Marine and Freshwater Ecosystems 8: 745–759. Walsh, C.J., Roy, A.H., Feminella, J.W., Cottingham, P.D., Groffman, P.M., and Morgan, R.P. 2005. The urban stream syndrome: current knowledge and the search for a cure. Journal of the North American Benthological Society 24: 706–723. Wirkkala, R.-S., Haimi, P., Raspletina, G., Susareva, O., Niinioja, R., R€am€o, A., Lozovik, P., Martynova, N., and Gordjuseva, N. 2000. River inputs into Lake Ladoga. In: Peltonen, A., Gr€onlund, E., Viljanen, M. (eds). Proceedings of the Third International Lake Ladoga Symposium 1999, University of Joensuu, Publications of Karelian Institute, pp. 168–174 Vol. 129.

Chapter 9

Arctic Rivers John E. Brittain

Gısli M. Gıslason

Vasily I. Ponomarev

Norwegian Water Resources and Energy Directorate, PO Box 5091 Majorstua, 0301 Oslo, Norway Natural History Museum, University of Oslo, PO Box 1172 Blindern, 0318 Oslo, Norway

Institute of Biology, University of Iceland, Askja-Natural Science Building, 101 Reykjavık, Iceland

Institute of Biology, Komi Science Centre, UrD RAS, 167982 Syktyvkar, Komi Republic, Russia

Jim Bogen

Sturla Brørs

Arne J. Jensen

Norwegian Water Resources and Energy Directorate, PO Box 5091 Majorstua, 0301 Oslo, Norway

Directorate for Nature Management, 7485 Trondheim, Norway

Norwegian Institute for Nature Research, 7485 Trondheim, Norway

Ludmila G. Khokhlova

Sergej K. Kochanov

Alexander V. Kokovkin

Institute of Biology, Komi Science Centre, UrD RAS, 167982 Syktyvkar, Komi Republic, Russia

Institute of Biology, Komi Science Centre, UrD RAS, 167982 Syktyvkar, Komi Republic, Russia

Institute of Social and Economic Problems of the North, Komi Science Centre, 167982 Syktyvkar, Komi Republic, Russia

Kjetil Melvold

´ lafsson Jo´n S. O

Lars-Evan Pettersson

Norwegian Water Resources and Energy Directorate, PO Box 5091 Majorstua, 0301 Oslo, Norway

Institute of Freshwater Fisheries, Keldnaholt, 112 Reykjavık, Iceland

Norwegian Water Resources and Energy Directorate, PO Box 5091 Majorstua, 0301 Oslo, Norway

Angelina S. Stenina Institute of Biology, Komi Science Centre, UrD RAS, 167982 Syktyvkar, Komi Republic, Russia

9.1.

9.2.

9.3.

Introduction 9.1.1. Geology 9.1.2. Landscape 9.1.3. Climate 9.1.4. Hydrology 9.1.5. Water Chemistry 9.1.6. Biota The Altaelva River 9.2.1. Physiography, Climate and Land Use 9.2.2. Geomorphology, Hydrology and Biogeochemistry 9.2.3. Biodiversity 9.2.4. Management and Conservation The Tana River 9.3.1. Physiography, Climate and Land Use 9.3.2. Geomorphology, Hydrology and Biogeochemistry

Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

9.4.

9.5.

9.6.

9.3.3. Biodiversity 9.3.4. Management and Conservation The Komagelva River 9.4.1. Physiography, Climate and Land Use 9.4.2. Geomorphology, Hydrology and Biogeochemistry 9.4.3. Biodiversity 9.4.4. Management and Conservation The Varzuga River 9.5.1. Physiography, Climate and Land Use 9.5.2. Geomorphology, Hydrology and Biogeochemistry 9.5.3. Biodiversity 9.5.4. Management and Conservation The Onega River 9.6.1. Physiography, Climate and Land Use 9.6.2. Hydrology and Hydrochemistry

337

338

9.7.

9.8.

9.9.

9.10.

9.11.

9.12.

9.13.

PART | I Rivers of Europe

9.6.3. Biodiversity 9.6.4. Management and Conservation The Northern Dvina River 9.7.1. Physiography, Climate and Land Use 9.7.2. Hydrology and Hydrochemistry 9.7.3. Biodiversity 9.7.4. Management and Conservation The Mezen River 9.8.1. Physiography, Climate and Land Use 9.8.2. Geomorphology, Hydrology and Hydrochemistry 9.8.3. Biodiversity 9.8.4. Management and Conservation The Pechora River 9.9.1. Physiography, Climate and Land Use 9.9.2. Geomorphology, Hydrology and Hydrochemistry 9.9.3. Biodiversity 9.9.4. Management and Conservation The Geithellnaa River 9.10.1. Physiography, Climate and Land Use 9.10.2. Geomorphology, Hydrology and Biogeochemistry 9.10.3. Biodiversity The Laxa River 9.11.1. Climate and Land Use 9.11.2. Geomorphology, Hydrology and Biogeochemistry 9.11.3. Biodiversity 9.11.4. Management and Conservation €kulsa River The Vestari Jo 9.12.1. Physiography, Climate and Land Use 9.12.2. Geomorphology, Hydrology and Biogeochemistry 9.12.3. Biodiversity The Bayelva River 9.13.1. Physiography, Climate and Land Use 9.13.2. Geomorphology, Hydrology and Biogeochemistry 9.13.3. Biodiversity 9.13.4. Management and Conservation Acknowledgements References

9.1. INTRODUCTION Arctic regions of the world cover a substantial portion of the Earth’s land mass and constitute one of the major biomes. Although annual precipitation is often low, streams, rivers, lakes and wetlands are particularly common and widespread due to low evaporation rates, widespread permafrost, and extensive melt water from snowfields and glaciers. Arctic river ecosystems (Figure 9.1) increase and decrease in tact with the Ice Ages and are therefore young in geological

terms. Since the last Ice Age many glacier-fed rivers have been replaced by snowmelt and rainfall dominated rivers; a change reflected in channel morphology, water quality and biota. Arctic rivers are generally among the most pristine ecosystems worldwide. However, they are under increasing threat from global and regional anthropogenic impacts. Although often far removed from centres of industrial activity, they are subject to the long-range transport of persistent organic pollutants in addition to local sources of pollution. For instance, freshwaters in northern Norway have been severely affected by acidification as a result of emissions from smelters further east. The poor nutrient status of many arctic ecosystems makes them particularly vulnerable to uptake of contaminants. Rivers along the northern coastlines of Eurasia are also key transport pathways, carrying pollutants from contaminated land areas, such as those associated with weapons production, out into the continental shelves of the northern oceans (AMAP 2004a,b, 2005a). The fish resources of Arctic rivers have been exploited by man for centuries, and catches of migrating salmonids have been important for many indigenous peoples. However, the introduction of exotic species and stocking with genetically foreign strains has been widespread. Recreational fishing is now becoming an important industry in many Arctic rivers. Climate change is also impacting the Arctic and current climate change scenarios indicate proportionally greater impacts at high latitudes (AMAP 2005b). In non-glacial rivers water, temperatures are expected to rise. In addition, increasing air temperatures may also disrupt permafrost leading to changes in runoff characteristics and favouring formation of groundwater storages. In contrast, increased glacier ablation will, at least in the short term, result in decreased water temperature and therefore a downstream expansion of the kryal fauna (McGregor et al. 1995). Arctic areas also contain major water resources that have been extensively exploited. The construction of dams and reservoirs for hydropower development has impacted many arctic rivers (Dynesius & Nilsson 1994), often leading to changes in water flow and temperature. The construction of dams also interrupts the river continuum and has been responsible, at least in part, for the decline of many migratory fish populations. Arctic rivers have also been used for transport of timber from forested inland areas, resulting in dam construction and canalisation. Flood protection measures, although less widespread than elsewhere in Europe, have also been instigated in some arctic rivers where infrastructures are at risk. The Arctic Circle (66 N 320 W) inadequately represents the Arctic region due to the effects of ocean currents and land mass topography influencing climate. Northwestern Europe is strongly influenced by the warm waters of the Gulf Stream, making the climate relatively mild in

Chapter | 9 Arctic Rivers

FIGURE 9.1 Digital elevation model (upper panel) and drainage network (lower panel) of Arctic Rivers.

339

340

winter. Hence, the Arctic is better defined as areas north of the treeline, typically approximating a mean July isotherm of 10 C. The Arctic can be divided into the High and the Low Arctic. The High Arctic typically refers to various islands lying within the Arctic Basin, such as the Svalbard archipelago. Deforestation in much of Iceland has created treeless areas that are often classed as subarctic as they possess many characteristics in common with the true arctic. The subarctic also includes a transitional zone between the continuous closed canopy woodlands of the boreal forest and the treeless arctic tundra. This transitional zone is wide in Eurasia where it can extend for 300 km.

9.1.1. Geology The geology of the European Arctic is varied. Norway’s northern most area, the county of Finnmark, has a complex geology. In the south and eastern parts eroded Precambrian bedrocks give rise to gentle slopes and rounded terrain forms. To the northwest, including the Varanger Peninsula, these bedrocks are overlain by sedimentary rocks, while further west hard gabbros characterize an alpine landscape. Glacial deposits are extensive and there are substantial gravel and sand deposits in the main valleys and on the Finnmarksvidda. Further east on the Kola Peninsula the bedrock is dominated by granite and gneiss of the Baltic Shield, although there are again extensive Quaternary deposits. The Dvina and Mezen basins are characterized by Permian, Triassic and Jurassic sandstones overlain by extensive Quaternary deposits. Further east the Pechora basin, bordered by the Timansky Ridge to the west and the Urals to the east, is known for its oil, gas and coal deposits. During the last major glaciation the major rivers of northwest Russia were blocked by the continental ice shelves of the Barents Sea, forming a huge inland sea, Lake Komi, which probably had its outlet into the Baltic Sea, although the final emptying of the lake occurred through the Pechora valley and the White Sea (Maslenikova & Mangerud 2001). Iceland is almost entirely of volcanic origin, and its bedrock is 80–85% basalt lava. The island straddles the Mid-Atlantic Ridge, marking the boundary between the North American and Eurasian tectonic plates. The active volcanic zones run through the island from southwest to northeast giving rise to lava flows, geysers and hot springs. Glaciers cover approximately 11% of the island (Einarsson 1994; Saemundsson 1979). Svalbard is a mountainous archipelago dominated by snow and ice and some 60% is covered by glaciers and icefields. The geology is varied, Precambrian, Cambrian and Ordovician basement rocks predominating along the west coast and in the northeast, while much of the archipelago is dominated by sedimentary rocks, Devonian, Carboniferous–Cretaceous and Tertiary strata. The latter contains layers of

PART | I Rivers of Europe

coal that form the basis of the coal mining industry on Svalbard.

9.1.2. Landscape Landscape forms are very different throughout the European Arctic. The western parts of Finnmark reach altitudes >1000 m asl and are characterized by deep valleys, steep slopes and glaciers. In contrast, the central parts of Finnmark and the Kola Peninsula have much more gentle terrain forms and are characterized by thousands of small lakes and pools, birch forest and extensive lichen heaths. Several fjords, Altafjord, Porsangerfjord, Laksefjord, Tanafjord and Varangerfjord, cut deep into this plateau-like landscape. To the southeast there are large tracts of open pine forest. These are the western outliers of the Taiga forests that stretch eastwards in a band across Russia all the way to the Pacific. Out towards the coast, on the Nordkinnhalvøya and the Varangerhalvøya birch forests give way to arctic tundra. Further east inland there are extensive undulating plains with a mosaic of rivers, lakes and bogs that stretch all the way to the Urals. Most of the plains are forested, but towards the coast in the east the forests give way to arctic tundra. There are extensive areas of permafrost in the lower part of the Pechora basin, notably in the northeast. About 60% of Iceland is a highland plateau >400 m asl. Coastal lowlands generally extend for only a short distance inland. Fjords cut deep into the plateau in the west, north and east, whereas these are extensive lava flats and alluvial plains in the south (LandmI`lingar Islands 1993). Cultivated land is limited to 1.4% of the island (Upplysingathjonusta landbunadarins 1994), while urban areas cover only 0.07%. After 1100 years of human activity, birch forest (Betula pubescens) now only covers about 1% of the island (Steindorsson 1964), although the treeline is around 400 m asl.

9.1.3. Climate Although located at 69–70 N, the coastal areas of Finnmark, especially in the west, are influenced by the Atlantic, giving rise to milder winters and cool summers. The inner parts of the fjords and the inland areas have a much more continental climate, with colder winters, warmer summers and lower precipitation. Further east the climate gets progressively cooler as the Atlantic influence decreases and this trend continues through the Northern Dvina, Mezen and Pechora basins. Winters are cold, although summers are warm in the more inland areas to the south. Iceland, situated at 63 250 –66 320 N, has a cool temperate maritime climate and average temperatures of the warmest month exceed 10 C only in the lowlands of the south and west, while in winter the coastal lowlands have a mean temperature close to 0 C. Annual precipitation varies from <600 mm in the north to in excess of 4000 mm over the highest icefields.

341

Chapter | 9 Arctic Rivers

The Svalbard Archipelago, located between 76 and 80 N and only 1000 km from the pole, has long winters with several months of constant darkness and short summers with midnight sun. The islands are influenced by the Gulf Stream and low pressure weather systems that track into the North Atlantic, and even during winter the western parts can experience periods with rain and temperatures over 0 C. However, summers are short, even in coastal areas. Snowmelt takes place during May and June and subzero temperatures usually return in September. During winter, extensive sea ice forms in the fjords and along many coastal areas.

9.1.4. Hydrology Three main types of running water ecosystems have been identified between the permanent snowline and treeline (Steffan 1971; Ward 1994): the kryal, or glacier-melt dominated system; the rhithral, or seasonal snowmelt-dominated system; and the krenal, or groundwater-fed system. Snow and ice cover varies significantly over small spatial scales, and different stream and river reaches will display characteristics that reflect the relative proportions of the three principal runoff sources (Brown et al. 2003). In High Arctic areas such as Svalbard, groundwater is limited by the widespread distribution of permafrost, but in areas further south it may be extensive. The proportion of these three water sources explains much of the spatial and temporal heterogeneity of biotic communities in Arctic rivers (Milner et al. 2001). In Arctic regions there is a close and interactive relationship between streams and their catchments. The significance of these interactions varies with changes in terrestrial vegetation and the extent of permanent snowfields and glaciers (Power & Power 1995). The input of allochthonous terrestrial plant material to aquatic ecosystems is greatest in subarctic areas, but may also be significant above the treeline where riparian vegetation, frequently of willows, can be extensive. Rivers in the European Arctic vary considerably in size, from the large rivers of northern Russia to the multitude of small and medium-sized rivers typical of northern Scandinavia. The rivers of Iceland and the Svalbard archipelago are typically short, but may seasonally display high flows as a result of snow and ice melt. Huge glacial outburst floods (J€ okulhlaup) may occur in glacial rivers, notably in Iceland, often completely reforming river channels and transporting huge amounts of sediments downstream. Significant freshwater discharges into coastal marine areas arise from tundra regions of northern Russia and many of these rivers also carry considerable amounts of sediments into estuarine and marine environments. Icelandic rivers have been divided into three categories (Kjartansson 1945, 1965): glacial rivers with high summer discharge, extensive sediment transport, high turbidity and unstable substrates (Palsson & Vigfusson 1991); direct runoff rivers found in catchments with bedrock of low permeability, with increasing influence of groundwater in the low-

lands and highest discharge during the spring thaw; and spring-fed rivers, the most common type close to the edges of the permeable bedrock within the neo-volcanic zone, particularly emerging under edges of post-glacial lava, often connected to fissure systems formed by tectonic movements (Sigurdsson 1990), and characterized by low annual fluctuations in discharge and relatively stable river beds. Many arctic rivers in northern Europe originate in temperate and boreal forests and, in contrast to most rivers, environmental conditions, such as water temperature and ice conditions often become more severe as they flow northwards towards the sea. Hydrological regimes are typified by the contrast between extremely low winter flows and the high discharges associated with spring snowmelt and the summer glacial melt season (Table 9.1, Figures 9.2 and 9.3).

9.1.5. Water Chemistry The chemistry of European arctic waters varies considerably, depending on geology, although nutrient levels are generally low throughout the region. The rivers in northern Norway and the Kola Peninsula that lie on the Baltic Shield have low levels of dissolved solids. Further east, several rivers originate in karst areas, giving much higher concentrations. The same is true of the rivers on Svalbard that lie on sedimentary rocks. Icelandic rivers vary in their chemical composition, largely depending on whether they originate from or flow through volcanic areas. In volcanic areas total dissolved solids (TDS), as well as phosphate and/or nitrate concentrations are naturally high.

9.1.6. Biota Water temperatures in arctic rivers are invariably low and fall with increasing altitude and latitude, although there are major differences between kryal and rhithral streams; often as much as 10 C during summer. Low temperatures combined with high sediment load and channel instability serve to make glacier-fed rivers amongst the most inclement of habitats for aquatic biota (Brittain & Milner 2001). Snow and ice is a particular feature of arctic rivers, creating unique environmental conditions that have led to the development of many adaptive mechanisms among the biota (F€ureder 1999; Prowse 2000), although winter conditions inevitably cause high mortality, especially in reaches susceptible to formation of frazil and anchor ice. The lack of nutrients, limited allochthonous inputs, low temperatures and the long period of ice and snow cover limits species richness, biomass and productivity. In general, species richness and ecosystem productivity decrease with increasing latitude (Castella et al. 2001). The extensive glaciation and the isolation of Svalbard and Iceland has also hindered colonisation and thereby limited biodiversity, both of fish and invertebrates (Milner et al. 2001; Gıslason 2005). On Iceland there are only one species each of Plecoptera and Ephemeroptera, 11 species of

342

TABLE 9.1 General characterization of the Arctic Rivers

Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25%) ecological regions Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparse vegetation & barren Wetland Freshwater bodies Glacier Protected area (% of catchment) Water stress (1–3) 1995 2070 Fragmentation (1–3) Number of large dams (>15 m) Native fish species Non-native fish species Large cities (>100 000) Human population density (people/km2) Annual GDP ($ per person)

Pechora

Mezen

Northern Dvina

Onega

Varzuga Komagelva

Tana

161 322 000 138.0 52.8 3.5 3 51; 60

137 78 000 27.1 56.9 0.9 1 60

143 357 000 109.0 59.9 0.9 2 60

135 56 900 16.9 62.9 1.7 1 60

158 9510 2.4 55.3 0.5 1 60

330 16 380 6.4 54.0 3.1 2 60; 62

0.0 0.1 0.3 53.1 42.5 0.5 1.4 2.1 0.0 12.2

0.0 6.4 24.8 56.5 0.0 0.0 11.9 0.4 0.0 6.2

0.1 7.2 0.0 90.6 0.5 0.0 0.0 1.6 0.0 5.2

0.1 19.4 11.3 51.9 0.0 0.0 14.7 2.6 0.0 6.1

0.0 0.5 20.2 49.9 0.0 0.0 26.2 3.2 0.0 23.7

0.0 0.0 30.9 0.8 0.0 51.7 16.6 0.0 0.0 93.5

1.0 1.0 2 2 35 2 1 2

1.0 1.0 1 0 27 1 0 0

1.0 1.0 1 0 35 6 3 5

1.0 1.0 1 0 28 4 0 3

1.0 1.0 1 0 20 1b 0 0

1.0 1.0 1 0 4 1b 0 0

2928

2929

2873

2929

2929

293 321 0.3 64.9 0.9 2 44; 62

34 076

Altaelva

Geithellna a Lax a

462 7389 3.1 56.4 3.8 2 60; 62

625 187 0.6 138.6 2.48a 1 38

0.0 0.0 26.6 33.1 22.1 10.2 6.1 1.9 0.0 33.0

0.0 0.1 66.7 16.9 1.4 4.8 7.8 2.3 0.0 1.0

0.0 0.0 0.5 3.3 16.2 68.0 0.0 0.4 11.6 0.0

1.0 1.0 1 0 17 4c 0 0

1.0 1.0 2 1 14 2b 0 2

1.0 1.0 1 0 1 0 0 0

30 710

33 981

31 325

Vestari-J€ okuls a

436 2385 1.8 47.8 2.2a 1 38

Bayelva

679 840 0.7 40.8 0.1 1 38

243 33 0.04 74.3 6.3 1 5

0.0 0.0 1.6 3.9 34.5 55.7 0.5 3.8 0.0 8.4

0.0 0.0 1.0 0.0 8.0 77.9 1.0 1.3 10.8 0.0

0.0 0.0 0.0 0.0 0.0 52.4 0.0 0.3 47.3 0.0

1.0 1.0 2 0 5 0 0 1

1.0 1.0 1 0 1 0 0 0

1.0 1.0 1 0 0 0 0 0

31 325

31 325

n.d.

PART | I Rivers of Europe

Precipitation and mean annual temperatures for the Laxa and Vestari-J€ o kulsa are based on data from the Icelandic Meterological Office, Reykjavik. Land use for Geithellnaa, Laxa and Vestari-J€ o kulsa based on information from G. Gudjonsson, Institute of Natural History, Reykjavik. Data on forest cover in Iceland: Iceland Forest Research Station data base. a Mean for whole catchment. b One species is not reproducing. c Three species are not reproducing. For data sources and detailed exlanation see Chapter 1. n.d.: no data

343

Chapter | 9 Arctic Rivers

FIGURE 9.2 Annual discharge patterns for selected Arctic rivers: Altaelva (1971–2004), Komagelva (1980–2003), Tana (1911–2004) and Bayelva (1990– 2004). The discharge patterns for Komagelva are based on discharge data from the gauging station at Batsfjord in a neighbouring catchment to the north.

Trichoptera, 4 Simuliidae, 80 species of Chironomidae and 5 species of Coleoptera. Of these, only Plecoptera, 5 species of Trichoptera, all Simulidae species and 41 species of Chironomidae occur in running waters (Tuxen 1938; Peterson 1977; Gıslason 1981; Lillehammer et al. 1986; Hrafnsdottir 2005). Svalbard has only a single trichopteran, Apatania zonella, a dubious record of an ephemeropteran and no Plecoptera (Coulson & Refseth 2004). In the arctic rivers of mainland Europe the biota becomes progressively more diverse as one moves eastwards and inland, with the lowest number of taxa along the Atlantic coast and the highest diversity in the continental Russian river catchments such as the Pechora. Grazers, notably chironomids, but also mayflies and caddisflies, are the dominant functional feeding group in alpine and arctic rivers owing to the lack of riparian vegetation, although in the low alpine/arctic the presence of riparian vegetation alongside the streams gives rise to a significant allocthonous input that is utilised by shredders, such as stoneflies (Peterson et al. 1995). In many European Arctic rivers salmonids (e.g. Atlantic salmon, brown trout, whitefish, grayling and Arctic char) are the most important fishes, both in terms of the number of species and in terms of their significance in sport and

commercial fisheries (Figures 9.4 and 9.5). The number of fish species is greatest in the large Russian rivers to the east and least in the islands of Svalbard and Iceland. There are six freshwater fish species in Iceland, all occurring in running waters: Atlantic salmon (Salmo salar), brown trout (Salmo trutta), Arctic charr (Salvelinus alpinus), the three-spined stickleback (Gastreosteus aculeatus), European eel (Anguilla anguilla) and its hybrid with the American eel (A. rostrata) and the European flounder (Platichthys flesus) (Gudbergsson & Antonsson 1996; Albert et al. 2006; Bjarni Jonsson, personal communication). Many salmonid fish populations undergo upstream migrations into arctic rivers from the sea which can represent a substantial input of marine derived nutrients to nutrient poor systems (Kline et al. 1997; Stockner & Macisaac 1996).

9.2. THE ALTAELVA RIVER The Altaelva River is the third largest river in northern Norway, and the sixth in Norway. It is a sixth order river and the catchment covers 7389 km2. The official name of the catchment is Alta–Kautokeinovassdraget, while the lower

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FIGURE 9.4 Annual catch of anadromous salmonids in selected northern Norwegian rivers.

FIGURE 9.3 Seasonal patterns in precipitation and runoff in selected Arctic rivers.

47 km of the river, as far as Atlantic salmon migrates, is called Altaelva. Further upstream, the river is known as Kautokeinoelva, but in this context the entire river is called the Altaelva River. The river originates near the Finnish border, flows primarily in a north direction, and empties into the innermost part of the Alta Fjord (70 N 23 E). The extensive plateau, Finnmarksvidda, at 300–500 m asl forms a large part of the drainage. The catchment is within the core area for the Sami people in Norway, and hence also a central area for reindeer husbandry. Remains of a 10 000 year old culture, called the ‘Komsa’ culture, after the initial finds at Alta, are the oldest traces of ancient people in Norway. It has not been proven that these people were ancestors of the Sami people (Anon. 1994). In Alta, >5000 rock carvings, the oldest dated around 4200 BC, have been uncovered in later years (www.alta. museum.no) and are listed on the UNESCO’s World Heritage List.

Chapter | 9 Arctic Rivers

The Altaelva is one of the most important salmon rivers in Norway. Written information about the Altaelva salmon exists from the 16th century, when the salmon fishery was owned by the king. In the middle of the 19th century, British people introduced sport fishery for salmon, and the river is now internationally famous for its sport fishery (Eikeset et al. 2001). After much controversy, especially with regard to the rights of the Sami people and the Altaelva salmon, a hydropower station was built on the river in 1987. The outlet of the power station is located at the top of the anadromous reach, 47 km from the sea. As a result, the temperature and flow regimes have been somewhat altered downstream, and the Atlantic salmon catches decreased in the area below the dam during the first 10 years of impoundment. However, in later years there are indications of recovery.

9.2.1. Physiography, Climate and Land Use About 30% of the catchment is covered by birch forest with treeline at 450–500 m asl and the rest by lichen heath, bedrock, bogs and numerous lakes. Agriculture is concentrated in the lower part of the river and around the communities of Kautokeino and Masi and covers only 0.03% of the catchment. About 17 000 people live within the catchment, most in the communities of Alta (pop. 9000) and Kautokeino (pop. 2000). There is little pollution, except some sewage downstream of Kautokeino (Traaen et al. 1983). The climate is influenced by the Gulf Stream, especially near the coast, with higher temperatures and more precipitation than inland areas, which have a more continental climate. At Alta, at the river mouth, annual mean precipitation is 420 mm, while the upper part of the catchment is among the driest areas of Norway, with an annual precipitation of 360 mm in Kautokeino (Norwegian Meteorological Institute). Most precipitation occurs in summer (June–September), especially in inland areas. The mean July temperature is 12.4 C in Kautokeino and 13.5 C in Alta. The mean January temperatures are 15.9 and 9.02 C, respectively. Finnmark County is the main area for reindeer husbandry in Norway. In the West Finnmark Reindeer District, of which the Alta–Kautokeino drainage is a major part, more than 1000 people are involved in reindeer husbandry, and in 2003 about 79 000 reindeer were present in this district. Almost the entire catchment, except the lower part of the valley near the main river, is used for reindeer grazing (Størset et al. 2004). Use of the natural resources, and other kinds of outdoor recreation, has a long tradition in the area and includes fishing, hunting, and berry picking, especially cloudberries.

9.2.2. Geomorphology, Hydrology and Biogeochemistry The geology of the catchment is varied. The lower part is characterized by Eocambrian metamorphosed sedimentary rocks, especially gneiss near the coast. In the upper part there

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are largely crystalline basement Pre-Eocambrian rocks, admixed with some basic rock types, giving circumneutral waters (Traaen et al. 1983). Much of the inland plateau is overlain with moraine deposits, while there are substantial glacial and marine deposits near the fjord. Two main branches of the river, one from northwest and the other from south, have their confluence 7 km downstream of Kautokeino. The headwaters of the northwest branch are 750 m asl. The first 20 km are rather steep (1.8%), but the river levels off on the Finnmarksvidda at 400 m asl. The south branch has its headwaters at 400 m asl in the interior of the plateau. The drainage from thousands of small lakes and ponds scattered throughout the plateau flows into the Kautokeino River. From the village of Kautokeino to the hydropower dam at Virdnejavri, a distance of 80 km, the fall is only 35 m. This part of the river is characterized by an almost continuous row of lakes, interrupted by riffles. The Virdnejavri dam was built across the valley in the upper part of the largest canyon in northern Europe (Photo 9.1). The outlet of the hydropower station is located at the limit for anadromous salmonids, 47 km from the sea. From here, the river flows rather rapidly to the sea, with an average gradient of <0.2%. The hydrological regime of the Altaelva River is characterized by high flows in early summer (May–June) and low flows in winter (Figure 9.2). The highest floods always occur during snowmelt and floods of more than 1000 m3/s are common (Magnell 1998). Rain-caused floods in late summer or autumn are rare and relatively small. At the outlet into the fjord (catchment area 7389 km2), the mean annual discharge is 99 m3/s (specific discharge 13.4 L/s/ km2). The highest observed floods were in late May 1920 and in mid-June 1917 with daily discharges of 1302 and 1225 m3/s, respectively. After the hydropower regulation in 1987, the annual flow regime changed, with higher discharge during winter and slightly lower discharge during the spring flood. The main river is covered with ice from November to May, although 5–7 km of the river downstream of the outlet of the power station is usually ice-free throughout most of the winter. The ice run in spring is now earlier than before regulation. Water temperatures are near zero from mid-November until late April, increasing during May/ June, and reaching a maximum of about 14 C in August. After regulation, water temperatures downstream have decreased during June and July, but have increased in late summer and early autumn due to the moderating effect of the hydropower reservoir. Just below the power station, temperatures have increased somewhat during winter. The tributary, Eibyelva, entering into the main river in the lower part of the catchment shows a similar temperature pattern as in the main river, except in the autumn. River waters are characterized by rather high alkalinity (200–400 CaHCO3 meq/L), and pH is usually above 7.0 (Traaen et al. 1983). Nitrate and phosphate concentrations are low throughout the catchment.

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PHOTO 9.1 Looking up the famous canyon on the Altaelva River (Photo: R. Pytte Asvall).

9.2.3. Biodiversity In connection with the creation of the hydropower reservoir, there was an increase in the green alga, Microspora amoena, as a result of increased phosphorous concentrations (Ugedal et al. 2005). This effect has now decreased and algal communities are now dominated by the green alga Ulothrix zonata and the diatom Didymosphaenia geminata. In connection with hydropower development, invertebrates have been thoroughly investigated in the lower part of the river. Densities were rather high for the region, with Chironomidae, the predominant group, followed by Ephemeroptera, Trichoptera and Plecoptera (Bergersen 1989; Ugedal et al. 2005). A correlation between algal biomass and invertebrate density has been shown (Koksvik & Reinertsen 2008) and after the initial increase in benthic densities as a result of increased algal growth, benthic densities have now decreased to pre-regulation densities. In total, 16, 21 and 18 species of Ephemeroptera, Trichoptera and Plecoptera, respectively, have been recorded in the lower part of the river. Baetis rhodani, Ephemerella aurivillii, E. mucronata, Diura nanseni, Leuctra fusca, Rhyacophila nubila and Arctopsyche lagodensis are the most numerous species (Ugedal et al. 2005; Koksvik & Reinertsen 2008). The stonefly fauna of the catchment is well documented (Lillehammer 1974, 1988) and in the upper part of the catchment 27 species have been recorded. Asellus aquaticus has been recorded from the upper part of the catchment (Walseng & Huru 1997). The freshwater snail, Valvata sibirica, classified as rare in the Norwegian Red List, has been recorded near Kautokeino (Walseng & Huru 1997). The stonefly, Nemoura viki,

considered as rare in the Red List, is known from the Kautokeino area (Lillehammer 1972). There are 14 native fish species in the river (Jensen et al. 1997). These species can be divided into two groups based on their immigration history. Atlantic salmon, brown trout, Arctic char, eel, three-spined stickleback and flounder immigrated from west and north, through marine waters. The other group, called the Finnmark species (whitefish, pike, minnow, burbot, perch and nine-spined stickleback), spread from the southeast from the Ancylus Sea in the Baltic area after the Ice Age (Huitfeldt-Kaas 1918). Atlantic salmon is the most important species in the anadromous section of the river (46 km), both economically and socially. The organisation of the sport fishery for salmon in this river is distinct. The fishing rights are owned by an organisation called ‘Alta Laksefiskeri Interessentskap (ALI)’. All people possessing or leasing agricultural land in the Alta valley sufficient to feed at least one cow can be members. The profit is divided equally between all members independent of property size. The fishing season lasts from 1 June to 31 August. Fishing permission is based on a combination of exclusive letting and selling of licenses on a daily or weekly basis. The number of fishing licenses is limited. Most daily and weekly based licenses are sold through a lottery to local people. There is also a sea trout fishery in the river, with annual catches of 1–2 tons. The Alta salmon is famous for its large size, with an average weight up to 10 kg in some years. Based on the annual catch, the Alta is one of the five best salmon rivers in the Arctic region (Figure 9.4). From 1891 to 2003, the mean annual recorded catch of anadromous salmonids

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Chapter | 9 Arctic Rivers

(Atlantic salmon, brown trout and Arctic charr) was 7.8 tons. Atlantic salmon comprised 86% of the catch since 1983. The average annual catch from 1974 to 2004 was 15 tons. Females are usually larger than males in the river because they stay longer at sea before they return to the river to spawn. Most males return after only 1 year at sea, while most females stay 3 years at sea before they mature and return to the river. The mean weight of 1-sea-winter (1SW) salmon in the period 1993–1997 was 2.0 kg. For 2SW, 3SW and 4SW fish in the same period, mean weights were 6.5, 10.5 and 14.5 kg, respectively (Jensen et al. 1998). The largest salmon ever caught weighed 27.1 kg. Thousands of lakes with good fishing in both summer and winter are located on the Finnmarksvidda. The main species are brown trout, Arctic charr and whitefish. Grayling was introduced to the river basin from the River Tana during the 1920s (Berg 1964). Pink salmon are also occasionally caught in the river, but reproduction has not been documented. This species has penetrated westwards from the Kola Peninsula, Russia, where it has been introduced on several occasions since the 1960s (Berg 1977). Only one amphibian, the common frog, is present in the watershed.

9.2.4. Management and Conservation The Altaelva River has been exploited for hydropower since 1987, with an annual production of 700 GWh. A 110-m high dam was constructed across the main river 5 km downstream from the original outlet of Lake Virdnejavri, 50 km from the sea. The lake surface has been raised 15 m. The length of the reservoir is 18 km, with a total regulation height of 20 m and a volume of 135 106 m3. The power station is near the dam, and the outlet at the upper end of the salmon producing area, 2.5 km downstream of the dam. The power station has an upper and a lower inlet, and because of reservoir stratification, water temperature in the river downstream can be modified. Just downstream of the dam, in the Sautso area, catches of Atlantic salmon have decreased after regulation, although not in other parts of the river (Ugedal et al. 2005). The regulation scheme is being revised to reduce the effects of temperature and flow changes on ice conditions and fish. The river has recently been designated a National Salmon River, giving the salmon population and its habitat additional focus in the management of the river. There are 19 km of flood protection embankments along the lower river, many built in connection with hydropower development. Recently, work has started to improve the quality and lessen the environmental impact of these embankments. Above Virdnejavri, the catchment is protected against further exploitation for hydropower by the National Protection Plan for River Systems (Anon. 1976). Eibyelva and other tributaries from the west below the dam are also protected. The outflow into Altafjord is on the monitoring list of river deltas compiled by the Norwegian

Directorate for Nature Management. The delta is an important transit site for wetland birds (Nordbakke 1983). The catchment has several plant species with distinct eastern distributions, notably the protected Oxytropis deflexa (Pall), not found elsewhere in Europe and represented by an endemic subspecies, O. deflexa norvegica. One of the two populations of this endemic subspecies has been reduced by the damming of the Alta River to form Virdnejavri reservoir (Elvebakk 2006).

9.3. THE TANA RIVER The sixth order subarctic border river between Norway and Finland, the Tana (Tenojoki in Finnish), has a catchment area of 16 380 km2, of which 5092 km2 is in Finland (Siirala & Huru 1990). The Tana flows northwards to the Tana Fjord on the Barents Sea at 70 470 N, 28 250 E. The name Tana comes from the Sami word, Deatnu, meaning ‘big river’, and is actually the name of the river from the junction of the major tributaries Karasjohka and Anarjohka (Inarijoki in Finnish), that drain a large part of the plateau, Finnmarksvidda. The river forms the border between Norway and Finland for 283 km, but the lowermost 77 km of the river is solely in Norway (Siirala & Huru 1990) and the last 18 km are tidal. Iesjavri, 390 m asl, the largest lake in the catchment with an area of 55 km2, drains to the major tributary Iesjohka. The Tana probably supports one of the largest stocks of Atlantic salmon in the world (Niemel€a 2004), as well as the world’s highest annual Atlantic salmon catch at an estimated 70 000–250 000 kg (Figure 9.4). The river valleys and aquatic habitats are virtually pristine, and the only human impact affecting the salmon is fishing (Niemel€a 2004). However, long stretches of the main stem have sandy substrate and low gradient, making them unsuitable for salmon production. Erosion is significant and huge sand banks build up in the river mouth, providing suitable habitat for up to 30 000 male goosanders during the moulting period in late summer and autumn (Svenning et al. 2005). The valleys of the Tana and its tributaries represent a core area for Sami culture and language. The catchment is sparsely populated (0.5/ km2), with a total of 7000 people, of which 5500 live in Norway (www.ssb.no/fob/kommunehefte). Most people live in the villages of Utsjoki, Nuorgam and Karigasniemi on the Finnish side, and Karasjok and Tana Bru in Norway.

9.3.1. Physiography, Climate and Land Use Bedrock in the lower 50 km of the river is little altered Eocambrian sedimentary rocks, while in the greater part of the catchment Precambrian rock complexes dominate. The river valley and much of the catchment is covered by Quaternary Ice Age deposits. Marine sediments, clay and silt, occur largely up to Storfossen (Alakong€as), but reach up to 90 m asl at Utsjoki. Glacio-fluvial deposits with coarse sand and gravels dominate upstream, although there are also areas

348

with fine glacio-lacustrine sediments (Fergus & R€onk€a 2001). The climate, especially in the southernmost part of the catchment, is continental, characterized by long winters and relatively warm summers (Fergus & R€ onk€a 2001). The lowest air temperature ever recorded in Norway, 51.4 C, was in Karasjok in 1886, while the lowest recorded monthly mean temperature was 27 C in February 1966, also in Karasjok (Fergus & R€ onk€a 2001). There is a climatic gradient from the coast, with long-term January/July mean air temperatures of 12.2/12.3 and 17.1/13.1 C at Rustefjelbma (10 m asl at the river mouth) and Karasjok (169 m asl), respectively (Norwegian Meteorological Institute). The climate is dry with an annual precipitation of 350– 450 mm, most falling during summer and especially in inland areas. The highest mountains are the Gaissat (1000 m asl) in the western part of the catchment, although most of the catchment lies at 200–400 m asl (Fergus & R€ onk€a 2001). Forest and alpine tundra each cover about 40% of the catchment and wetlands 10% (Fergus & R€ onk€a 2001). The treeline is 20–30 m asl at the coast increasing to 400 m asl further inland. Most of the forest is birch, but along Utsjoki, Karasjohka, Anarjohka and the main stem down to Levajok, open pine forests dominate. A mosaic of wetlands, lichen heaths and birch forest is typical in much of the southwestern catchment, especially along Iesjohka. Stone walls to gather and lead wild reindeer towards and over cliffs have been found in or near the river valley (Vorren 1958), and have been dated to >4000 years BP (Furset 1995). Until the 17th century, the Sami people were almost the only inhabitants and they administered the fisheries themselves (Steinar Pedersen, personal communication). Salmon was a valuable resource, attracting traders from countries such as Holland (Pedersen 1986). The present national border, at that time between Denmark and Sweden, was drawn up in 1751, but the Sami people continued to fish more or less as before (Pedersen 1991). The Sami people of the river valleys developed the nomadic way of reindeer husbandry during the second part of the 17th century, probably because of reduced game stocks (Siirala & Huru 1990). Through an annex to the border treaty in 1751, the Sami people in the border area could use land and water resources on both sides of the border, still making it possible for the people living in, for example Utsjoki, to bring their reindeer to the fjords in summer (Pedersen 2006). In 1852 the border was ‘closed’, creating serious consequences for reindeer husbandry and to a lesser extent salmon fishing (Siirala & Huru 1990). Reindeer husbandry is still important and about 99% of the area in the region of Karasjok is used for reindeer grazing (Siirala & Huru 1990), supporting up to 50 000 reindeer in winter, spring and autumn (Anon. 2006). Even though the general trend has been a reduction in numbers, many people are still full or part-time employed in reindeer husbandry.

PART | I Rivers of Europe

A fishing arrangement closing the entire or part of the river with birch branches or similar material placed between wooden poles, a precursor of the still used ‘barrier’ was in use in earlier centuries (Pedersen 1986). This required cooperation between the people on both sides of the river, and was used in the upper part of the main stem and in Iesjohka and Karasjohka (Pedersen 1986). Those who now have fishing rights for nets are allowed to use different types of gear for salmon fishing, although this is now strictly regulated. Presently, it is possible to travel by car on both sides of the main stem and even to Angeli on the Finnish side of upper Anarjohka, but roads suitable for cars were not completed along the main stem until 1979. Earlier the river played a major role in transportation and people were obliged to go by river boat in summer and on the river ice in wintertime. There is also a track for snowmobiles along the main stem. The river was previously used for transportation of timber, mainly along Karasjohka and Anarjohka.

9.3.2. Geomorphology, Hydrology and Biogeochemistry The valleys of Anarjohka and the main stem downstream have a typical U-shaped formed by Ice Age glaciers. The valley floor is 200–300 m lower than the mountain plateau and lichen heaths above. Along the river valley there are substantial deposits of gravel and sand, forming eskers, terraces and deltas (Siirala & Huru 1990). These deposits are the main source of sediment in the river and most of their erosion is a result of natural processes (Fergus & R€ onk€a 2001). Extensive unstable sandbanks are a characteristic feature of the lower parts of Tana (Eie et al. 1996). At Storfossen and much of the lower stem, sand underlies the surface layer while in Utsjoki and Leavvajohka there is more gravel. Transport of suspended material is relatively low and in 1999 a specific sediment yield of 4800 tons/year was measured. However, large amounts of sand are transported along the river bottom and also in suspension during major floods (Fergus & R€onk€a 2001). River water quality has been classified as good or very good in the later years (Traaen 2003), although previously the river was significantly polluted with sewage downstream of Karasjok. After 1993, the situation improved with the installation of a new sewage treatment plant. The river has high levels of dissolved salts (calcium 2–9 mg/L) due to calcareous rocks and extensive moraine deposits. The waters are circumneutral with a pH of 6.8–7.6 and conductivity 31– 79 mS/cm (Traaen 2003; Johansen et al. 2005). Natural levels of phosphorus in the Tana are relatively high (4.5– 7.5 mg/L in 2002) and contribute to good productivity. Episodes with increased erosion and ensuing high turbidity give increased levels of total phosphorous, especially in the lower reaches (Traaen 2003). The hydrology of the Tana is characterized by high flows in early summer (May–June) and low flows in winter

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PHOTO 9.2 The Tana River is icecovered from October to May and experiences major ice runs in most years. (Photo: R. Pytte Asvall).

(Figure 9.2). The highest floods always occur during snowmelt. Rain-induced floods in late summer or autumn are rare and relatively minor. At the outlet into the fjord, the mean annual discharge is 203 m3/s, giving a specific discharge of 12.4 L/s/km2. The highest observed floods were in late May 1920 and in mid-June 1917 with daily discharges of 3844 and 3429 m3/s, respectively. From October to May the river is ice-covered, with water temperature of 0.1–0.4 C (Niemel€a 2004). The Tana River has amongst the most spectacular ice runs in the country (Photo 9.2). Since the uppermost tributaries are to the south and have a more continental climate, maximum temperatures in spring tend to be higher. This gives rise to earlier ice melting than in the more coastal areas downstream, sometimes leading to major ice jams in narrow rapids such as around the Storfossen area. The ice runs give rise to substantial erosion and sediment transport (Fergus & R€ onk€a 2001). There is often extensive local flooding due to ice jams, especially in the upper reaches. Late ice runs, in late May and early June, give the most extensive flooding as discharge is usually greater at that time. Water temperature is measured at Polmak (50 km from the mouth) in the lower part of the river and in the tributary Karasjohka some 250 km from the mouth. During winter (late October until late April) water temperatures are close to 0 C, rising to about 15 C in summer. Mean water temperatures in the Utsjoki area reach 12.9 C in July. In the tributary streams summer temperatures vary mostly between 10 and 15, although some streams are cooler (Johansen et al. 2005).

9.3.3. Biodiversity In general, information about freshwater invertebrates is sparse (Walseng & Huru 1997). Johansen (2005) recorded 17 mayfly species, 20 stonefly species and 21 caddisfly taxa from tributary streams. E. aurivillii, Baetis muticus, B. subalpinus and B. rhodani were the most widespread mayflies. D. nanseni, Arcynopteryx compacts, Taeniopteryx nebulosa, Protonemura meyeri, Leuctra spp. and Capnia atra were the most common stoneflies. The stonefly, Nemoura. viki, considered as rare in the Norwegian Red List, is known from the Tana catchment (Lillehammer 1972; Johansen 2005). The pearl mussel was previously widely distributed in the Tana, but in 2004 it was only found in a few locations (Paul Eric Aspholm, personal communication), probably due to excess harvesting. Pisidium amnicum recorded near Karasjohka is classified as rare in the Norwegian Red list (Walseng & Huru 1997). The freshwater snail, Valvata sibirica, classified as rare in the Norwegian Red List, has also been recorded from the catchment (Walseng & Huru 1997). The crustacean, Lynceus brachyurus, is recorded from Maskejohka (Walseng & Huru 1997). The copepod, Heterocope borealis, restricted to the county of Finnmark in Norway, is found in pools and tarns in the catchment. Mysis relicta has been recorded from Polmakvatn, south of Tana Bru. Seventeen native fish species have been recorded in the Tana, including the bullhead, which is probably introduced. More than 1200 river km are accessible for anadromous salmonids (Niemel€a 2004). In addition to the main stem, there are more than 20 spawning tributaries with distinct salmon

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strains (Elo et al. 1994; V€ah€a et al. 2007). Tributary streams with dense riparian vegetation have been shown to be of major importance for food and cover for salmon parr (Johansen et al. 2005). During the period 1972–2006 the annual catch of Atlantic salmon usually varied between 100 and 200 metric tons, with a mean of 135 tons. The salmon population is dominated by grilse and 2-sea-winter fish and the mean weight from 1990 to 1999 was 3.6 kg. The salmon show diverse life history traits. The freshwater phase is between 2 and 8 years, whereas the marine phase varies from 1 to 5 years before returning for the first time to spawn (Niemel€a et al. 2000). Many salmon survive spawning at an increasing rate, and since 2000 previous spawners have represented up to 25 % of the total spawning stock of multi sea winter salmon (Niemel€a et al. 2006). In total, virgin and previous spawning salmon give rise to nearly 100 smolt and sea age combinations, which is the greatest in any single river system throughout the distribution area of Atlantic salmon (Niemel€a 2004, Jaakko Erkinaro personal communication). According to Berg (1964), there has also been a stock of the so-called ‘autumn salmon’ that ascend the river in autumn but do not spawn until the next season, as in a large proportion of the salmon in White Sea rivers such as the Varzuga (Jensen et al. 1998; Section 9.5). There are indications that these ‘autumn salmon’ have become rare of late. Pink salmon have been introduced into the Barents Sea and White Sea basins from the Pacific Ocean since 1956 (Bjerknes & Vaag 1980), and they have been recorded in the catches in Tana each year since the 1970s. Spawning has not been documented. Since the 1970s, the bullhead has been recorded in the large Finnish tributary Utsjoki (Pihjala et al. 1998). It is frequent in areas with low salmon density but is seldom found in areas with a high salmon density (Gabler 2000). In 2000, the bullhead was found for the first time in the main stem of the Tana near the confluence with the tributary Utsjoki (Niemel€a 2004). Despite being on the Norwegian Red List, it has probably been introduced into Utsjoki. The viviparous lizard probably has its northern limit in the river system, but its distribution is not mapped in detail (Siirala & Huru 1990). There is a small population of the harbour seal, registered in the Norwegian Red List as in need of monitoring, in the Tana estuary. In the 1800s, the population was much larger. Grey seals and harp seals also occur in the Tana Fjord. The Anarjohka and Lemenjoki National Parks in the upper catchment are important areas for brown bears. Elk seem to be increasing in number and are common in the river valleys.

9.3.4. Management and Conservation The Atlantic salmon is economically the most important fish species, and up to 45 000 daily fishing licenses are sold to tourists annually. Sea trout, grayling, whitefish and pike are also economically important. Today salmon are caught by

PART | I Rivers of Europe

several methods, such as ‘barriers’, fixed gill nets, drift nets, and rod and line. Barriers consist of a fence made of wood or metal bars and a gill net which is attached to the outer edge of the fence. The nets are set in a hook-like position to drive the fish into a narrow corner. Gill nets and barriers probably take about half the catch, rod and line accounting for the other half (Erkinaro et al. 1999). Besides the main stem of the Tana between Storfossen and Levajok, Iesjohka and Karasjohka are known to produce the largest salmon in the river system (Niemel€a 2004). A male salmon weighing 36 kg was caught below Storfossen in 1928, probably a world record for this species (Berg 1964). The conservation of the salmon stocks of the Tana is based completely on natural production. The catchment is protected against hydropower exploitation (Anon. 1976) and there are no dams or power stations on the river. Furthermore, through a bilateral agreement between Norway and Finland, fish stocking is not allowed. The river has recently been designated as a National Salmon River, giving the salmon population and its habitat additional focus in the management of the river. Even if the stocks seem to be relatively healthy, some symptoms of over exploitation have been reported (Berg 1964; Niemel€a 2004; Moen unpublished data). Some of the weakest tributary stocks seem to be extinct and important tributaries like Iesjohka were found to have below optimal salmon parr densities in the 1970s (Bjerknes 1978). In 2001, catches were almost at the level of the mid 1970s, even though low densities of spawning salmon have been reported in Karasjohka and Iesjohka in several years after 2000. More than 30 km of erosion protection have been built along the river by Finnish and Norwegian authorities since the mid-1970s, but this is unlikely to be extended in the future (Fergus & R€onk€a 2001). Nevertheless, most of the Tana is a dynamic system little affected by human impact. The large natural sediment sources and the natural erosion and sedimentation processes remain active and make it unique in Norway and more akin to the large Russian rivers further to the east. The river mouth (‘Tanamunningen’) is a Nature Reserve and a Ramsar site. An unspoilt river estuary of this size is rare in Europe. The site is particularly important for the goosander Mergus merganser, with up to 13.5% of the Northwest–Central European population resting there during moulting in autumn. In Austertana, on the east side of the river mouth, there has been mining for quartzite that is shipped out directly. The discharge of ballast waters from these ships represents a potential threat to local biodiversity. In Anarjohka National Park in the south, and in many other areas along the river valleys further downstream, reindeer husbandry is widespread, especially in winter, and there have been problems with overgrazing in recent years (Anon. 2006). There are some cabins associated with reindeer husbandry, fishing and hunting. Along some of the tributaries there are tracks for snowmobile and ATV vehicles, and sea planes are allowed to land at certain sites. Apart from these activities, there is little human impact in the catchment.

Chapter | 9 Arctic Rivers

9.4. THE KOMAGELVA RIVER The Komagelva is a fourth order river that begins on the plateau of the Varanger Peninsula and flows eastwards to the Varangerfjord at KomagvI`r. The 321 km2 catchment has a maximum altitude of 633 m asl. The few lakes in the catchment are small. The river mouth is about 30 km from the easternmost town in Norway, Vardø. In fine weather you can see over to Russia on the other side of the Varangerfjord. The region has an arctic climate, with a mean July air temperature of only 9.2 C in Vardø and the entire Komagelva catchment lies north of the treeline. Komagelva is an attractive salmon and Arctic charr river. The catchment has an interesting geology, flora and fauna and the river was included in the first National Protection Plan in 1973. The municipality of Vardø and the surrounding region has a long history. The precursor of Vardøhus fort was built in the 1300s (Willoch 1960). The marine resources in the Barents Sea have given rise to an extensive fishing industry, although in recent years there has been a decline in local land-based processing and unemployment has been high.

9.4.1. Physiography, Climate and Land Use Bedrock of the catchment consists of Eocambrium sedimentary rocks, mainly sandstones. The Trollfjord–Komagelv fault zone runs more or less along the river course. The river valley itself has been formed by running water and not by glacial erosion (Sørbel & Tolgensbakk 2004). The inland ice in this area was polar in nature and thus

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frozen permanently to the bedrock. In the bottom of the valleys and along the sides there are deposits of moraine material and meltwater channels. Almost circular deposits or rings of moraine material are unusual, but are more common in this region than in any other part of the world (Sørbel & Tolgensbakk 2004). The river bed is composed predominantly of gravel and stones and appears fairly stable (Power 1973). Below the ravine, Bjørneskardet, there are no waterfalls or rapids to prevent ascending anadromous fish. In the lower part of the valley, the river has cut through a flat plain and flows in a wide shallow channel between steep banks (Power 1973). The river waters are circumneutral (pH 6.95–7.45) and ionic content increases downstream (conductivity 20– 50 mS/cm) (Eie et al. 1982). Climatically, the Varanger Peninsula is at the border of permanent permafrost (Sørbel & Tolgensbakk 2004), with a mean annual temperature in Vardø of 1.3 C (Norwegian Meteorological Institute). Precipitation is low with an annual mean in Vardø of 563 mm for the period 1961–1990. The maritime influence gives a mean January temperature in Vardø of 5.1 C. The uppermost reaches of the catchment are practically without vegetation, although further downstream grasses and heath vegetation occur (Photo 9.3). Below Bjørneskardet, where the river becomes slower flowing and meandering, there are dense riparian stands of willow (Eie et al. 1996). In general the river and the river valley are little influenced by human activity. The catchment is used for reindeer husbandry, largely in summer. Less than 10 persons live permanently around the river mouth, although the lowermost part of the catchment has 150 recreational cabins. PHOTO 9.3 The upper reaches of the river, Komagelva, Varangerhalvøya National Park. (Photo: A. Bjordal).

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A road open for vehicles reaches about 7 km into the valley, serving anglers and grouse hunters together with cabin owners. The road is closed in winter, but there is a snowmobile track. In summer, the reindeer herdsmen use ATV vehicles in the catchment.

9.4.2. Geomorphology, Hydrology and Biogeochemistry The catchment is susceptible to erosion and frost action is probably a major source of river sediment. In a nearby catchment, Julelva, the specific sediment yield was estimated at 23 tons/km2/year (Jim Bogen, personal communication). There are no discharge records from Komagelva. However, data from neighbouring rivers show that the hydrological regime in the area is characterized by high flows during snowmelt (mid-May to mid-July) and low flows in winter. The highest floods always occur during snowmelt. The lack of lakes in the Komagelva catchment usually limits the duration of high flows in spring to about 3 weeks (Berg 1964). Rain-induced floods in late summer or autumn are rare and relatively small. At the outlet into the fjord, the mean annual discharge is calculated at 8.3 m3/s (specific discharge 25.8 L/s/km2). The mean lowest annual discharge and the mean annual flood discharge, estimated on data from neighbouring rivers, are 0.7 and 66 m3/s, respectively (Figure 9.2). There are few observations of water temperature from Komagelva (Eie et al. 1982). However, data from other rivers in the area show that from early November to late May the water temperature remains close to 0 C, increasing rapidly to 12–16 C in July/August. The river is ice covered from November to May and ice runs in spring can be relatively severe. In some years there may be temporary ice runs during autumn (Berg 1964).

9.4.3. Biodiversity In general, the flora and fauna of the Varanger region is of considerable interest because of its location between western and eastern biogeographical elements. Among the eastern plant species typical of the area are Allium schoenoprasum ssp. sibiricum, Dianthus superbus, Oxytropis campestris ssp. sordida and Veronica longifola (Anon. 2004). The willow stands along Komagelva are considered of international interest (Anon. 2004). Benthic densities are low above 300 m asl. In the lower river below Bjørneskardet, benthic densities are unusually high for the region, probably due to the high allochthonous inputs from dense riparian willow stands. The high benthic biomass provides the basis for good salmonid production. Chironomids and mayflies dominated the benthos during July and August, and 8 species of mayfly, 11 species of stonefly and 4 species of blackfly have been recorded (Eie et al. 1982) The fauna is typical of the

PART | I Rivers of Europe

northern and eastern parts of Scandinavia. The small water bodies along the floodplain of the river have a rich and varied zooplankton fauna and 18 taxa have been recorded (Eie et al. 1982). The fish community in the Komagelva consists of the species moving in from the west after the Ice Age: Arctic charr, Atlantic salmon and brown trout, as well as threeand ten-spined sticklebacks (Huitfeldt-Kaas 1918). The anadromous reach is only 33 km, but relative to its size, the Komagelva is an attractive salmon and sea charr river; giving annual catches of more than 6000 kg salmon in the 1970s (Figure 9.4). The river has never been stocked with salmon or other fish species. After the 1970s, the salmon catches have been relatively stable at a significantly lower level than before, although the reason for this is unknown. From 1905 to 2003, the mean annual recorded catch of anadromous salmonids (Atlantic salmon, brown trout and Arctic charr) was 2.5 tons. Since 1983, Atlantic salmon have constituted 78% of the catch. The salmon population is dominated by grilse and the mean weight from 1990 to 1999 was 2.3 kg. They are known to be especially shy and difficult to catch, probably due to the crystal clear water and low discharge (Berg 1964). Pink salmon have been stocked in the Barents Sea and White Sea basins from the Pacific Ocean since 1956, and from year to year some of these fish reach the Komagelva. They may also have come from some of the Norwegian salmon rivers where they seem to spawn regularly, such as the river Neiden on the south side of Varangerfjord. Spawning of pink salmon has not been documented in the Komagelva. The marshes and wetlands along the river valley are important ornithological sites for among others red-necked phalarope, red-throated diver and whooper swan (Systad et al. 2003). The endangered Arctic fox has one of its last outposts on the European mainland in the heart of the Varanger Peninsula. The wolverine has always been present in the Varanger Peninsula, but is seen as a constant threat to the reindeer husbandry.

9.4.4. Management and Conservation The Komagelva was among the first group of Norwegian rivers protected against exploitation for hydropower in 1973 (Kontaktutvalget Kraftutbygging – naturvern 1971). Most of the catchment is now included in the recently established 1804 km2 Varangerhalvøya National Park (Anon. 2004). The area is highly pristine, and contains a suite of different biogeographical regions, special biotopes for protection of plants and animals, river valleys, valuable coastal areas and cultural relics. The shoreline of the Varangerfjord south of the river mouth is a nature reserve because of its sand dunes and several ‘eastern’ plant species growing at the extreme western edge of their distribution. In 2003, the Norwegian Parliament included Komagelva as one of the

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PHOTO 9.4 The Varzuga River with Varzuga village in the background. (Photo: B. O. Johnsen).

‘National Salmon Rivers’, the only one wholly in the Arctic (Anon. 2001).

9.5. THE VARZUGA RIVER The Varzuga River is on the Arctic Circle in the southern part of the Kola Peninsula in northwest Russia. It flows southeast from Varzugskoie Lake and drains into the White Sea. It is one of the largest rivers on the Kola Peninsula with a length of 254 km and catchment area of 9510 km2. The primary tributaries are the Pana, Arenga, Serga and Kitsa Rivers (Photo 9.4).

9.5.1. Physiography, Climate and Land Use Bedrock of the Kola Peninsula is dominated by granite and gneiss of the Baltic Shield, although there are extensive Quaternary deposits. The catchment area consists of 50% wetlands and 50% forest. It is mainly low gradient marshy tundra. The vegetation is dominated by lichen heath, birch trees and willow scrub. In some locations, primarily on hills, conifers grow. Surface soils are peaty or sandy, but occasionally rocky. The climate is characterized by long winters and cool summers. The mean annual air temperature in the nearby Umba village is 0.5 C, with means of 11.0 C in January and 14.3 C in July. Mean annual precipitation is 498 mm, with greatest amounts in summer (Anon. 2003). Most of the catchment is unpopulated, but there are two small villages, Kuzomen and Varzuga, near the mouth of the river and 24 km upstream, respectively (Photo 9.4).

9.5.2. Geomorphology, Hydrology and Biogeochemistry The headwaters are 200 m asl and the river has a mean gradient of about 0.8 m/km. In the upper reaches, runs and small riffles of 25–40 m predominate. In the middle reaches, large pools are more common, in addition to some major rapids, being especially frequent in the lower reaches. In the headwaters, the river is 2–6 m wide, increasing to 20–40 m in the upper reaches, 60–150 m in the middle reaches and up to 200 m in the lower reaches. In the lower 20 km, which is tidal, the river can be up to 800 m wide. The mean discharge near the village of Varzuga is 76.5 m3/s. The annual discharge regime is characterized by a spring flood, low discharge during summer, smaller floods during autumn and low water levels in winter. The spring flood, lasting for 15– 40 days, normally occurs in May and June. The lowest water level during summer is usually observed in July. The river freezes in October–November and ice-break occurs in May. Riffles and runs become ice-covered 20–40 days later than pools, while major rapids freeze only during the most severe winters. Anchor ice may form in riffle reaches. Water temperature rises rapidly during May, and increases to a maximum of about 17 C in July. In general, the waters of the Varzuga have low ionic concentrations due to low dissolution of crystalline minerals in the catchment, and its water chemistry has remained essentially unchanged for more than 50 years (Ziuganov et al. 1998).

9.5.3. Biodiversity Twenty native fish species occur in the River Varzuga (Jensen et al. 1997). Atlantic salmon is the predominant fish

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species, but brown trout, grayling, whitefish, pike, roach, minnow, perch and three- and nine-spined sticklebacks are also common. The salmon stock in the Varzuga is one of the largest in the world, and on average 70 000 spawners ascended the river annually during the last 15 years of the 20th century (Kaliuzhin 2003). The Varzuga has two distinct salmon runs. The summer run fish arrive in June to midAugust and spawn that autumn. In contrast, the autumn run fish arrive from mid-August onwards and continue upstream until ice formation. They do not spawn in the year they arrive, but wait until the following autumn before spawning (Jensen et al. 1998). Most salmon are grilse (1-sea-winter fish). Introduced pink salmon occasionally enter the river. Pink salmon have been introduced into the Barents Sea and White Sea basins from the Pacific Ocean since 1956. They are now established in some rivers on the Kola Peninsula and enter other rivers in the region (Berg 1977). The Varzuga River has the world’s largest population of freshwater pearl mussels, estimated to exceed 100 million specimens (Ziuganov et al. 1994).

9.5.4. Management and Conservation The catchment has not been subject to any major economic developments. However, the salmon population has become the target of harvesting, providing an important source of income for local communities. Before 1958, nets operated in the lower reaches were used to fish for salmon. After 1958, the river has been blocked by a barrier fence with a trap (‘Ruz’), which is installed annually at a site located 12 km upstream from the river mouth. Usually, all ascending fish were caught for commercial purposes each second day, while on alternate days they were allowed to migrate freely. From 1987 onwards, the fence has been operated every third day or less frequently. From 1961 to 1989, the catch of Atlantic salmon varied between 33.4 and 161.2 metric tons, and averaged 72.5 tons (Jensen et al. 1997). In later years, several camps for recreational sport fishery have been established in the river, mainly practising a catch and release fishery. Recent genetic studies (Primmer et al. 2006) indicate that there is a significant degree of isolation between the salmon populations of individual reaches and tributaries, suggesting that the preservation of a number of spawning sites spaced throughout the tributary system is recommendable for ensuring sustainable fishing tourism in the river.

9.6. THE ONEGA RIVER The Onega catchment is situated in the northern part of the East European Plain and bounded by the Vetreniy Poyas and Andoma Uplands in the west, and the Onega–Dvina, Ozersk–Lebshina, and Sukhona–Dvina Uplands in the east. The Onega, a fifth order river, originates in Lake Lacha and flows north through the Vozhe–Latchensk and Onega lowlands and discharges into Onega Bay on the White Sea. The

PART | I Rivers of Europe

Onega has a catchment area of 56 900 km2 and a river length of 416 km. There are more than 3000 lakes within the river catchment. The Onega catchment is entirely within the Arkhangelsk Region. Over the centuries the river has served as one of the main trade routes towards the White Sea. Before the port of Arkhangelsk was built at the mouth of the Northern Dvina, Onega was the only large port in northern Russia. The waters of the Onega catchment are used for domestic and municipal services as well as for the timber industry.

9.6.1. Physiography, Climate and Land Use The relief of the Onega catchment is a result of successive glaciations, with undulating plains and hilly moraines. In the south, the glacial plains are at an altitude of 100–150 m asl. The river flows along an undulating, forested plain and forms a delta where it flows into Onega Bay. Rapids are frequent and in the upper reaches of the river the most difficult rapids to pass have always been Kargopolski Rapids (388–370 km from the mouth), in the mid-channel the Biryuchevski Rapids (212–190 km from the mouth), and in the lower reaches the Kokorinski Rapids (25–18 km from the mouth). The spring flood in the upper reaches of the Onega lasts for 3 months and discharge remains high during most of the summer. Numerous cold springs discharge into the upper and middle reaches of the river, and the groundwater contribution to the Onega is 30–40%, the highest among comparable rivers in the region. The catchment area has a temperate-continental climate with short cool summers and long cold winters. The average annual temperature in the south of the catchment at the town of Kargopol is 1.5 C, and in the north at the town of Onega it is 1.3 C. The average temperature of the warmest month ranges from 16.4 C (Kargopol) to 15.9 C (Onega). Mean temperatures usually are >0 C in April, and temperatures fall <0 C in the latter part of October. The duration of the frost-free period at the mouth of the Onega River is on average 107 days (Pylnikova 1989). The Onega catchment belongs to the zone of high humidity. The annual precipitation is about 600 mm, with highest rainfall from July to September. The landscape is usually snow covered from late October until late April, with a normal snow depth of 60– 70 cm. The catchment is situated in the podzol soils zone of the north and middle Taiga. The primary soils originate from Quaternary deposits: moraine and top-soil loams, and fluvioglacial and ancient alluvial sand deposits. The Severo– Onezhsk bauxite deposits are associated with Carboniferous karst limestones. The catchment is covered with coniferous forest, mainly pine.

9.6.2. Hydrology and Hydrochemistry The widest ranges in water level recorded in the Onega River are 3.4 m in the upper reaches, 9.7 m in the mid-channel and 6 m in the lower reaches. The largest recorded river

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discharge was 4930 m3/s, the lowest 82.6 m3/s. The average annual river discharge at the mouth is 535 m3/s. The mean specific catchment runoff is 9.8 L/s/km2 (Figure 9.3). As a rule, the average discharge of the spring flood is approximately six-fold larger than mean discharge. However, the seasonal unevenness of the flow in the Onega is reduced by its lake source and the karst structure of the river catchment. The density of the hydrographic network is 0.39 km/ km2. The ice regime of the river is complex, and the Onega River has one of the shortest ice cover periods of the larger northern rivers on account of rapids. At rapids and groundwater inflows, the ice cover is temporary. Freezing of the Onega River begins at its mouth in the north and spreads upstream. In the upper reaches of the Onega, ice break usually proceeds quickly and does not cause any problems, although lake ice remains longer. In the mid-channel and lower reaches there are usually two ice runs, the main one from the Onega and another from its tributaries. Water chemistry of the Onega is strongly influenced by the 90+ highly mineralized springs in the upper reaches. The proportion of groundwater in the upper reaches of the river amounts to 40–50%. During winter the mineral content is 181–354 mg/L, decreasing during the spring flood and increasing again to 225 mg/L during low flows in summer. At the river mouth the mineral content is on average 20 mg/L lower. Bicarbonate and calcium are the predominant components. Up to 25% of the Onega catchment is boggy, resulting in high humic levels and high colour values (60–200 ). The average concentration of iron is 0.5 mg/L, but sometimes it exceeds 1.0 mg/L. The content of ammonia nitrogen lies within the range 0.04–0.30 mg/L. Oxygen deficiency (down to 49%) occurs during winter, but in summer, the average saturation is 70 to 90%. The waters are predominantly alkaline (pH 6.9–7.4) (Filenko 1974; Olenicheva 1990–1991).

9.6.3. Biodiversity Data on aquatic biodiversity are scarce and fragmentary and to a large extent refer to animal populations. In the Onega catchment, species of the genera Potamogeton, Sparganium, Stratiotes, Hydrocharis, Typha, and rarely Petasites, have been recorded (Tolmochev 1974–1977; Potokina 1985). The following aquatic species are protected: Subularia aquatica, Lobelia dortmanna, Batrachium dichotomum, Typha angustifolia, T. latifolia, Spirodela polyrrhiza, Zostera marina and several species of sedge (Andreev 1995). The planktonic fauna of the Onega includes 72 species, mostly Cladocera, but also Copepoda (Cyclopidae, Calanoida) and Rotifera (Gordeeva 1983). The composition is similar to that of the Northern Dvina, the main part consisting of widespread species of Bosmina, Chydorus, Mesocyclops and Euchlanis. The fauna of the upper reaches consists predominantly of limnophilous species. The average density of zooplankton is 483 000/m3, giving a biomass of 3.7 g/m3. Due to high current speed and sediment load in the middle

reaches, zooplankton here are mostly bottom-dwelling species in areas near banks. Zooplankton diversity increases in the lower reaches due to the slower current. Sixteen macroinvertebrate groups have been recorded in the drift (Shubina et al. 1990). Mayflies, blackflies and chironomids were the most numerous, although caddisflies were also an important part of the biomass. The zoobenthos is mainly composed of chironomids, mayflies, stoneflies, blackflies, beetles, molluscs and worms (Gordeeva 1983). In summer, the average density is 968/m2, giving a biomass of 6 g/m2. On sandy-silty substrates, molluscs (Pisidium) make up 70% of the biomass. On clay-sandy substrates the community is characterized by a predominance of chironomids and oligochaetes constituting the main part of the biomass. The numbers of molluscs is limited by high current speed. In the stony bottom community, Cryptochironomus, Pisidium and hydropsychid Trichoptera are frequent. There are 32 species of fish from 13 families in the Onega, including pink salmon, Atlantic salmon, brown trout, vendace, northern whitefish, powan, inconnu, and grayling (Novoselov 2000). Sterlet, northern whitefish and pink salmon are among the introduced species. Ten species of amphibians and reptiles have been recorded within the limits of the Onega catchment (Kuzmin 1999). The majority of the species are widely distributed from the headwaters to the river mouth, but the crested newt is restricted to southern areas of the catchment. There are 182 species of breeding birds in the Onega catchment within the limits of the Arkhangelsk and Vologda regions (Dementiev & Gladkov 1951–1954; Ivanov & Shtegman 1978; Sviridova & Zubakina 2000). The song birds have the greatest number of species, followed by sandpipers, waterfowl, birds of prey and owls. The majority are migrating species and only 45 species inhabit the catchment throughout the whole year. The avifauna is dominated by species widespread in the Palearctic, followed by species of European and Siberian origin. There are few Arctic species. In the catchment, 52 species of mammals have been recorded (Geptner et al. 1961, 1967; Dinets & Rotshild 1996), with 51 species recorded in the southern part of the catchment and 44 species in the lower reaches. The southern area forms the northern limit for several species of mammals (hedgehog, bat, harvest mouse, common vole, European polecat and roe deer). In contrast, arctic foxes only occur in the northern part during their autumn–winter migration.

9.6.4. Management and Conservation The Arkhangelsk Region Red Book (Andreev 1995) includes the fish species inconnu and bullhead. As they are at their northern limit and low in numbers, four amphibians (Anguis fragilis, Lacerta agilis, Natrix natrix and Vipera berus) are also included in the Arkhangelsk Region Red Book. Twenty-one species of birds are included in the Red Book of the Russian Federation. An additional 53 species on

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PHOTO 9.5 The Sysola River, Northern Dvina basin, looking downstream (Photo: V. Ponomarev).

the decline or at the northern limit are included in the Red Book of the Arkhangelsk Region. Among the introduced mammals are representatives of the American muskrat and American mink, and Far Eastern raccoon dog. At the beginning of the 20th century, beaver were reintroduced. Many mammals that are at their northern limits in the catchment are included into the regional Red Book due to low numbers. The Kenozersky, Vodlozersky and Russian North National Parks are located in the Onega catchment. The main aim is protection and promotion of the recreational use of northern mid-taiga forests and a number of historical and cultural sites. In 2005, the Kenozersky National Park was included in the list of UNESCO biosphere reserves. The Kozhozerskiy Reserve and seven game preserves are also in the catchment (Yermolin 1991; Kulikov 1995).

9.7. THE NORTHERN DVINA RIVER The Northern (Severanaya) Dvina, a seventh order river, has the largest catchment in Europe and discharges into the Arctic Ocean (Photo 9.5). It has the second highest discharge after the Pechora. The catchment is located in the northern part of the East-European Plain. It is bounded in the west by the Onega–Dvina Plateau and in the east by the Dvina– Mezen Plateau and the Timansky Ridge in the Vychegda River catchment, which forms the border with the catchment of the Pechora River. The southern part the catchment is located in the high areas of the Northern Ridges that form the main watershed of the Russian Plain and separates the catchment from the rivers flowing north from the Volga catchment. The Northern Dvina catchment comprises 357 000 km2, and it is 744 km from the junction of the Sukhona and the Yug Rivers to the sea.

The geographical position of the Northern Dvina, with its proximity to the Volga catchment and its relief, has given it a vital role in the history of Russia. The river network and lakes of the catchment’s southern border (including the Sukhona River and Kubenskoe Lake) form a part of the Northern Dvina waterway, constructed in 1825–1828, connecting the catchments of the White Sea and the Caspian Sea. It starts on the Sheksna River near the community of Topornaya and ends on the Sukhona River at the well-known Znamenity Lock. The total length of the system is 127 km. The Sukhona River is one of the Russian rivers where people have always tried to improve navigation conditions, and even in 1278 Russian princes attempted to regulate various difficult bends in the river channel.

9.7.1. Physiography, Climate and Land Use The relief of the Northern Dvina catchment was formed as a result of glaciation that caused topography of undulating surfaces and hilly moraines. In the south of the catchment (in the Vologda Region), glacial valleys reach around 100– 150 m asl. The Dvina–Mezen Plain slopes gently north towards the White Sea. The plains are forested and mainly boggy. In the north, it gradually changes to the Primorskaya coastal plain at 5–75 m asl. In the east and northeast, the Mezen–Vychegda plain meets the Northern Ridges at 250– 270 m asl. In the northeast, the Timansky Ridge separates the catchment from the Pechora catchment. Towards the Onega–Dvina divide is an undulating plain at 100– 200 m asl, with hills up to 250 m asl and where the lower parts are boggy. In the southeast there is a plateau with altitudes up to 150–200 m asl. The southern part is formed by the Sukhona–Volga watershed, while in the east it

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stretches along the western slopes of the Northern Ridges. In the Timan Range there are karst formations. The climate of the region is characterized by a low number of sunshine hours in winter due to the influence of the northern seas and intensive western movement of air masses from the Atlantic. This also leads to changeable weather throughout the year. The short, cool summer lasts for 2–3 months, with a mean monthly temperature of 16–17 C, but with frosts possible in any month. Autumn starts during early September with temperatures down to 2 to 4 C. The common autumn weather pattern is rainy with frequent thaws (Kobysheva & Narovlyansky 1978). In October, cold arctic winds are followed by a decrease in temperature to 10 to 15 C. Winter starts in late October and lasts for 5– 6 months. The mean temperature in January is 20 C. Snow cover is stable and blizzards frequent. Winter precipitation is 110–200 mm, while summer rainfall is 400–500 mm. The main soil-forming strata in the Northern Dvina catchment include overburdens of drift clay and blanket clay, fluvio-glacial sediments and fossil alluvial sand sediments. The catchment is located in the area of podzolic soils of the northern, sub- and southern taiga. The terrain is mainly covered with coniferous forests and peat bogs. Sparse timberlands are characteristic of the northern taiga, while to the south there are large areas of dense, fast growing coniferous forest.

9.7.2. Hydrology and Hydrochemistry The smaller river valleys are up to 10–50 m deep and several hundreds metres wide, while the large rivers have a trapezoid valley profile with a wide flat bed. In the lower reaches of the Northern Dvina the valleys are shallow with gently sloping sides. The Northern Dvina River is formed by the junction of the Yug River (catchment area 35 600 km2) and the Sukhona River (50 300 km2), in whose estuary there is the historic town of Veliky Ustug. The Vychegda River (121 000 km2) flows into the Northern Dvina 74 km downstream. The Vychegda River is the largest tributary on the river. Downstream of the confluence, the Northern Dvina is called the ‘Big’ Northern Dvina. Kotlas, at the mouth of the Vychegda River, is the second largest city in the Arkhangelskaya Region. It is an important river port and railway junction in the European North of Russia, established in 1899. The hydrographic network frequency of the Yug River is 0.72 km/km2, that of the Sukhona is 0.52 km/km2 and that of the Vychegda 0.62 km/km2. At 362 km from the mouth, the Vaga River (catchment 44 800 km2) flows into the Northern Dvina from the left bank. From here, the river flows through gypsum strata almost down to the mouth. At 137 km, the right bank tributary, the Pinega River (42 000 km2), flows into the Northern Dvina just upstream of the estuary. The river is 600–800 m wide, increasing to 2.0–2.5 km at the estuary. In general, the density of the hydrographic network is 0.58 km/km2; and the total length of all waterways in the catchment is more than 206 000 km.

The river is mainly fed by precipitation and snowmelt (Figure 9.3). Groundwater is insignificant and patchy, although in the southeast mineral springs play some role in groundwater supply. The river carries a high sediment load that contributes to forming the vast multi-channel delta. Extensive floodplains with terraces are typical of most tributaries. There are long reaches with sandbanks, although most rivers, except for the Vychegda, do not meander. River water solute concentrations are usually 200–450 mg/L, but sometimes fall to 100 mg/L. Bicarbonate, calcareous waters dominate. In the Northern Dvina estuary, solute concentrations reach 13 000 mg/L due to intrusion of saline water up to the Mekhrenga and Kuloy Rivers. In such cases, the concentration of chloride can reach 5.6 mg/L and that of sodium up to 3100 mg/L. Water colour varies from 30 to 250 , dichromate oxidation is about 13–80 mg/L, but in the estuary it can reach 188 mg/L. Iron concentrations vary widely (130– 3570 g/L), as does ammonium (70–2200 mg/L). The waters are saturated in oxygen for most of the year, but during winter ice cover values may fall to 12–27%. The pH is in the region of 6.5–7.8 (Olenicheva 1990–1991; Filenko 1974).

9.7.3. Biodiversity The Northern Dvina phytoplankton is typical of lowland rivers (Bryzgalo et al. 2002), mainly consisting of diatoms and green algae, with Asterionella and Aulacoseira being dominant, and Cyclotella and Stephanodiscus occurring in some areas. In warm periods, Anabaena increases in number. In the estuary, phytoplankton includes Fragilaria, Diatoma, Nitzschia, Scenedesmus and Pediastrum. Cyanobacteria are represented by species of Microcystis, Anabaena and Merismopedia. Their densities change from 400 to 6 000 000/L according to locality and season. At pulp and paper mill discharges the density of algae decreases. According to Korde (1959), Vychegda River phytoplankton includes 110 algal taxa and 13 Cyanobacteria. Most diversity and highest densities are in diatoms, followed by Cyanobacteria (Anabaena and Aphanizomenon). In some lakes, algal blooms have been recorded. The density of algae varies from 84 to 503 000/m3. In upstream reaches there are 150 taxa with diatoms having the greatest diversity (Getsen & Barinova 1969). The main genera are Epithemia, Cocconeis, Synedra, Achnanthes, Fragilaria, Diatoma, Gomphonema, Melosira, Cymbella and Rhoicosphenia. In hilly reaches, Ulothrix, Cladophora, Spirogyra, Oedogonium and Chantransya are common and stones are often covered with the Cyanobacteria, Nostoc. Characteristic genera for the Northern Dvina catchment are Potamogeton, Sparganium, Equisetum, Sagittaria, Ceratophylla and Petasites (Tolmachev 1974–77; Zvereva 1969; Potokina 1985; Vekhov 1990). In the Northern Dvina delta, subject to brackish water, Triglochin, Mertensia and Zannichelia occur. The downstream ecosystems have changed due

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to human use of the floodplain (Vekhov 1990, 1993) and Utricularia, Myriophyllum, Potamogeton, Nuphar, and Butomus are becoming rare. In enclosed channels Hydrocharis, Stratiotes, Sparganium and Lemna are present, while in coastal zones Caltha, Alisma, Polygonum, Carex, Equisetum and Typha are found. In places showing anthropogenic impacts, Elodea canadensis is often dominant (Postovalova 1966; Teteryuk 2003). The Northern Dvina zooplankton is rich in Bosmina, Chydorus, Mesocyclops and Euchlanis species (Gordeeva 1983). Holopedium, Daphnia, Pleuroxus, Podon and Ectocyclops are also common. In the area near the estuary, there are 122 species of macroinvertebrates (Semernoy 1990), including sponges, oligochaetes, leeches, molluscs and chironomids. Oligochaetes and chironomids are most diverse, while Isochaetides, Orthocladius and Mollusca are the most numerous. Mean zoobenthos density and biomass is 6800/ m2 and 11.3 g/m2, respectively. Typical genera among molluscs are Planorbis and Valvata, and among Chironomidae, Limnochironomus and Procladius (Yepishin & Yelsukova 1990). In polluted areas, Rotifera dominate, in particular, Brachionus (Bryzgalo et al. 2002), while zoobenthos densities increase due to higher numbers of oligochaetes. In the Vychegda River, zooplankton includes 44 taxa of Rotifera and 31 taxa of Cladocera (Korde 1959). On average, rotifers constitute 96% of numbers. Zooplankton is similar to that of the Northern Dvina. Densities vary from 10 000 to 253 000/m3 (Zvereva 1969). Zoobenthos includes 17 groups, dominated by Chironomidae, and Oligochaeta and molluscs in some areas (Zvereva 1969; Leshko 1998). There are 51 species of molluscs, with the genera Anisus, Lymnaea and Sphaerium most numerous (Leshko 1998). The fish fauna includes 41 species from 14 families (Solovkina 1975; Novoselov 2000) such as Atlantic salmon, vendace, powan, inconnu and grayling. As a result of introductions, river fishes also include Danubian bream, asp, spined loach, northern whitefish, zander and pink salmon. In the Northern Dvina, there are 11 species of amphibians and reptiles (Anufriev & Bobretsov 1996; Kuzmin 1999). Many species are at their northern limit, and Tritutus vulgaris, T. cristatus, A. fragilis, N. natrix and V. berus are common only in the southern taiga and sub-taiga zones, while the other species are recorded north towards the estuary. The Northern Dvina is the western border for Salamandrella keyserlingii. At present, breeding birds in the Northern Dvina catchment, including territories from the southern taiga to shrub tundra include 16 orders (Yestafiev et al. 1995, 1999; Sviridova & Zubakina 2000). The northern border of 88 breeding bird species lies within the catchment. The highest bird diversity, 195 species, is typical of the headwater and midreaches. Further north, the avifauna is poorer, and in the lower reaches there are 107 species. There are 56 non-migratory species in the Northern Dvina catchment. In the southern and central parts of the Northern Dvina, birds common for the Palaearctic region are most usual, although

PART | I Rivers of Europe

species of European and Siberian origin are also typical. In the north, birds of Siberian and Arctic origin are common, including waterfowl and sandpipers. In the south, there are many birds of prey, owls, pigeons, doves, woodpeckers and song birds. Since the beginning of the 20th century, populations of some 40 species, mainly European or common Palaearctic species have moved northwards. In contrast, partridges have moved south, while they were earlier typical in zones up to the sub-taiga (Kochanov 2001). There are 56 species of mammals recorded in the Northern Dvina catchment (Geptner et al. 1961, 1967; Anufriev et al. 1994; Polezhaev et al. 1998). In the southern, middle and partially in the northern taiga, there are 51 species compared to 38 species in downstream areas. The borders of the subtaiga and northern taiga form the limit of species such as water shrew, hedgehog, polecat, bats, raccoon dog, wild boar and roe deer. Lemming, narrow-headed vole and Arctic fox all inhabit the tundra. In the middle of the 20th century, new species were introduced: muskrat, American mink and raccoon dog, and European beaver were reintroduced.

9.7.4. Management and Conservation For many centuries, the Northern Dvina has served not only as the main waterway of Russia, connecting its centre to the North, but also to Europe. At present, the main industries in the Northern Dvina catchment are timber, wood processing, pulp and paper, mechanical engineering, ferrous metallurgy, light industry and food production. The macrophytes, Oenanthe aquatica, Nimphoides peltatum, Elatine hydropiper, Mertensia maritima, S. aquatica, Nuphar pumila, S. polyrrhiza, Zannichelia pedunculata, T. angustifolia, L. dortmanna, Ranunculus lingua and Eleocharis quinqueflora are among the protected species (Andreev 1995; Taskaev 1998). Triglochin, Potamogeton and Veronica anagallis-aquatica are classified as vulnerable. The Pinega Reserve, created in 1974, and 16 reserves aimed at preserving and enhancing rare species and lake ecosystems are in the Northern Dvina catchment (Yermolin 1991). In the Komi Republic, there are three specially protected water bodies, six ichthyological reserves in the catchments of the Vym, Sysola and Vychegda and complex reserves like the one on Sindor Lake (Taskaev et al. 1996). The fishes, inconnu and bullhead, are listed in the Red Books of the Arkhangelskaya and the Vologodskaya regions. Due to a limited and sporadic distribution and low numbers, five species of reptiles and amphibians have been included in the Red Books of the Arkhangelsk region and the Komi Republic (Taskaev 1998). Some 22 species of birds are listed in the Red Book of the Russian Federation. Due to low population size, around 60 species located in the northern areas are listed in the Red Books of the Komi Republic, the Arkhangelsk Region and the Vologodkaya Region. Many mammalian species inhabiting the northern borders of their distribution also have small populations and have been entered into regional Red Books.

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9.8. THE MEZEN RIVER The Mezen, a sixth order river, is one of the longest and largest in northeast Europe with a length of 966 km and catchment area of 78 000 km2. It originates at Chetlassky Stone (500 m asl) in the North Timan and enters the Mezen Bay of the White Sea. The Vashka River is the largest tributary with a length of 605 km and catchment area of 21 000 km2. It enters the Mezen 192 km from the estuary (Zhila 1965). Administratively, 400 km of the Mezen is situated in the Komi Republic (43.5% of the catchment), and the rest is within the Nenets National District of the Archangelsk Region. The main part (75% of the area) of the Vashka River flows through the Komi Republic. The main communities are the towns of Koslan and Usogork and the 16th century town of Mezen at the estuary (Ilyina & Grakhov 1987).

9.8.1. Physiography, Climate and Land Use The springs that form the source of the Mezen River are situated between the bogs near Chetlassky Stone. The river runs first south and then northwards, flowing along the western slope of Timan Ridge. Much of the catchment is flat, mostly at altitudes of 130–180 m asl. The river catchment is underlain by Permian, Triassic and Jurassic rocks, and overlain by Quaternary deposits up to 20 m deep. The soils are mostly podzolic and boggy, although humus soils occur in Timan Ridge area. The Mezen catchment lies mainly within the sub-zones of the central and northern taiga, forests constituting 87% and bogs 12% of the area. Frequent changes of air masses characterize the climate in the Mezen catchment. Proximity to the ocean also has an impact on climate. From south to north, mean annual temperature decreases from 1.2 C (Kotlas) to 1.1 C (Mezen). Throughout most of the catchment, January is the coldest month, but February is the coldest in the Mezen estuary. Mean daily temperature falls to 44 C during extremely severe winters on the coast of the White Sea. In contrast, an absolute maximum temperature of 35 C has been recorded in July. Spring usually starts in early April, while summer begins in early June. By the end of September, the mean daily temperature falls to 5 C. Winter starts at the end of October and lasts until the beginning of May. Runoff is 50–55% of the annual precipitation of 600 mm. About 200 mm precipitation is stored in the snow pack before being released in the spring thaw (Zhila & Alyushinskaya 1972; Anon. 1989).

9.8.2. Geomorphology, Hydrology and Hydrochemistry The Mezen catchment covers a considerable part of northeast European Russia. The mean annual discharge to the White Sea is 858 m3/s (Table 9.1, Figure 9.3), which is gives a total yearly freshwater volume of >27 km3. The Mezen River is a typical northern river, characterized by high flows

during the spring thaw, low flows during summer, interrupted by flash floods, as well as by very low winter flows. Widespread karst systems in the Timan Ridge provide much of the source water for the Mezen River and its tributaries and reduce variation in discharge. In upstream areas, the Mezen River is 0.5–1 km wide, but when it turns north its width increases to 2–5 km. At the town of Mezan, the river is 3–4 km wide. Floodplain terraces, often complex and up to 200 m wide, are noticeable along the river valley. In the estuary, water levels have an amplitude up to 7.6 m and the river is tidal >60 km upstream (Ilyina & Grakhov 1987). The hydrochemistry of the Mezen system was studied from 1987 to 1990 by Khokhlova (1997). The waters are characteristically rich in calcium carbonate, with TDS concentrations of 2.8–200 mg/L, depending on season. In the tributaries of the Vashka River (Evva River), the concentration of major ions reaches 300 mg/L. There are also increased concentrations of sulphates and sodium ions due to underground karst sources. Rivers of the Mezen catchment vary in content of organic and inorganic compounds. Colour, permanganate and dichromate values vary between 10 and 168 , 3.7–23.0 and 7.6–59.1 mg/L, respectively. High concentrations have been recorded for ammonia (up to 1.78 mg/L) and iron compounds (up to 0.90 mg/L). Pollutants such as phenol (2–28 mg/L) from forestry and copper (2–17 mg/L) from natural sources exceed maximum permissible levels in fishery areas.

9.8.3. Biodiversity Most of the available information on biodiversity is from the upper and middle reaches of the Mezen and some of its tributaries. A total of 168 diatom taxa have been recorded in nonplanktonic communities in the Mezen River and its tributaries, such as the Vashka, Ertom, Evva and Pozh. Epilithon is abundant, with Fragilaria, Achnanthes, Epithemia and Cocconeis most common. Tributaries are rich in Melosira and Gomphonema and other genera. Cocconeis placentula and Melosira varians are commonly recorded. Most of the dominant species are considered to be indicators of high nutrient content (Stenina 1997). Their development is favoured by macrophytes present in the slow-flowing river and the alkaline waters. The most common genera in the Mezen River are Potamogeton, Sparganium, Sagittaria, Batrachium, Stratiotes and Hydrocharis (Tolmachev 1974–1977; Shmidt & Sergienko 1984; Leshko 1998). The estuary is rich in Triglochin martimum. Potamogeton and Petasites are widespread in slowflowing reaches with sand-silt substrata Myriophyllum, Eleocharis, Sagittaria and Uricularia are also present. Aquatic mosses such as Fontinalis and Dichelima cover stony and silty bottom (Shubina & Zheleznova 2002). River banks are colonised by Carex, Equisetum, Comarum, Alisma and Butomus. Allium, Pinguicula and Aster are found in the moist and stony towpaths and stony headlands (Lashenkova 1970).

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Zooplankton consists of rotifers, cladocerans and copepods (Leshko et al. 1990). Numbers and biomass are extremely low, with maximum values of 790/m3 and 0.006 g/m2, respectively (Zvereva & Ostroumov 1953). Euricercus, Simocephalus, Polyphemus, Scarpholeberis and Acroperuus dominate the near shore zone and slow-flowing reaches of the river. The zoobenthos includes Hydra, Nematoda, Oligochaeta, Mollusca, Araneina, Hydracarina, Harpacticoida, Cladocera, Ostracoda, Copepoda, Collembola, Odonata, Ephemeroptera, Plecoptera, Coleoptera, Trichoptera, Simuliidae, Chironomidae Heleidae and Diptera (Zvereva & Ostroumov 1953; Leshko 1996; Leshko et al. 1990; Sidorov et al. 1999). Chironomids are abundant, up to 2300/ m2. The biomass in the slow-flowing middle reaches is dominated by Mollusca (up to 3.2 g/m2). A study carried out in 1997 (Sidorov et al. 1999) showed that Chironomidae and Ephemeroptera dominated the biomass in upstream reaches. Chironomidae on stony substrates include 87 taxa (Kuzmina 2001), the most common being Orthocladius, Microtendipes, Thienemanniella, Tanytarsus and Cladotanytarsus. The benthos in the tributaries has a similar composition (Martynov et al. 1997), although Chironomidae are more numerous; from 1700 to 9700/m2. Coleoptera, Trichoptera and Chironomidae are major contributors to the zoobenthic biomass. There are 57 species of molluscs (Leshko 1998), the most important are in the genera Cincinna, Anisus and Lymnaea. Leeches are widespread, especially the genera Pisciola and Helobdella (Lukin 1954). The fish fauna of the Mezen consists of 28 species from 11 families (Solovkina 1975). The most important are the native species, Atlantic salmon, powan, inconnu and grayling, as well as the non-native pink salmon. One reptilian species (Lacerta vivvipara) and three amphibians (S. keyserlingii, Rana arvalis, Rana temporaria) are recorded from the catchment (Anufriev & Bobretsov 1996; Kuzmin 1999). The fauna of nesting birds is represented by 156 species (Yestafiev et al. 1995, 1999), compared to 30 species wintering in the region. Bird communities are composed of widespread Palearctic taiga species, as well as Siberian and European species. There are 45 mammal species in the Mezen catchment (Geptner et al. 1961, 1967; Polezhaev et al. 1998; Anufriev 2004), most of which are widespread across the entire catchment.

9.8.4. Management and Conservation A number of protected areas (zakazniks) have been created in the Mezen catchment, primarily for protection of the landscape and bogs/forests (Yermolin 1991; Taskaev et al. 1996). In terms of the fishery, the Mezen River and its tributaries is one of the most valuable river catchments in NW Russia. Nymphaea candida, N. pumila, Spirodela polyrrhiza are protected species (Andreev 1995). The vascular plants, Triglochin maritimum and Sparganium microcarpum as well as the moss, Dichelima falcatum, have decreased due

PART | I Rivers of Europe

to anthropogenic impact (Taskaev 1998) and are vulnerable. The fishes, inconnu and bullhead, are listed in the regional Red Book of the Komi Republic and Archangelsk region (Andreev 1995; Taskaev 1998). The Siberian salamander, S. keyserlingii, is included in the Red Book of the Archangelsk region and Komi Republic. This species occurs sporadically in the middle reaches of the Mezen, mainly in the higher wetlands. The natural taiga landscape, plentiful forage and the absence of human disturbance help to preserve rare and protected birds. The Red Book of the Russian Federation includes12 species, while the regional Red Book of the Komi Republic and Archangelsk region lists an additional 18 threatened or decreasing bird species. Naturalized mammals include the muskrat and raccoon dog, while the beaver has been reintroduced. The list of protected mammals includes six species from the northern areas (taiga shrew, Northern bat, Russian flying squirrel, Siberian chipmunk, European mink and badger) in the regional Red Books of the Archangelsk region (Andreev 1995) and Komi Republic (Taskaev 1998). The Mezen River catchment is little developed economically, but in the long-term there is potential for forestry and agriculture. Nevertheless, intensive deforestation has caused impoverishment of zoobenthos in some reaches (Leshko 1996, 1998).

9.9. THE PECHORA RIVER The Pechora, a 12th order river, has the highest mean discharge of European rivers flowing into the Arctic Sea. Its occupies the vast Pechora lowlands bordered by the Ural Mountains in the east and by the Timansky Ridge in the west and southwest, dividing the Pechora from catchments of the Northern Dvina, Mezen and Volga Rivers. The Pechora catchment covers 322 000 km2 and the river is 1809 km long (Photo 9.6). The original colonization of the region started in the Palaeozoic around 300 000 years ago. The earliest archaeological remains are at the Mamontova kurya site in the middle reaches of the Usa River, the largest right-hand tributary of the Pechora. The Finno-Permian tribes, ancestors of the present-day Finnish people, appeared in the region in the Late Stone Age (3000–4000 BC). The ancestors of Komi people, the present-day indigenous people, appeared in this area in the first millennium BC. The far northern regions (tundra, forest tundra) were populated by the Ugro-Samodian tribes in the Middle Ages. They engaged in deer hunting, fishing and hunting marine animals (Stolpovsky 1999; Spiridonov 2001).

9.9.1. Physiography, Climate and Land Use The catchment of the Pechora River is in the northeast part of the East European Plain and also partly in the Ural Mountains. The catchment is divided into three main orthographic provinces: the Pechora lowlands, the Timansky

Chapter | 9 Arctic Rivers

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PHOTO 9.6 Valley of the Pechora River, middle section (Photo: V. Ponomarev).

Ridge and the Urals. The northeast part of the catchment is within the boarders of Bolshezemelskaya tundra which is a hilly plain with numerous moraines and ridges at 200– 350 m asl. Between the moraines and ridges are many lakes, mostly of thermokarst origin. The northwest part of the Pechora River is occupied by the Malozemelskaya tundra. The Timansky Ridge, with an average altitude of about 190 m asl and peaks of around 400 m asl (Chetlassky Kamen at 463 m asl), forms the west and southwest part of the catchment (Zhila & Alyushinskaya 1972). The east part of the catchment is formed by the Ural Mountains with maximum altitudes of 1600–1800 m asl (Gora Naroda 1895 m) and small glaciers in the highest parts. The Urals in the Pechora River catchment are 20–50 km wide in the north and 60–100 km wide in the south. The Ural Mountains capture the moisture-laden air, giving rise to high flows in the rivers flowing from the western slopes. The main mountain rivers (Upper Pechora, Ilych, Shugor, Kosyu) flow in broad valleys. The mountains are mainly composed of metamorphic and igneous rocks, although as in the Timansky Ridge, karst structures are widely developed in the Ural foothills, influencing the hydrology of smaller rivers. The central part of the Pechora catchment is occupied by the Pechora Lowlands, a flat area overlain with 100 m or more moraine material (Rykhter 1966; Efimov & Zaitsev 1970). The topsoil of the catchment’s largest part, from 60 latitude southwards, is podzol, loam and sand, while in tundra areas waterlogged gleysol soils dominate. Vast peat bogs are widely distributed throughout the catchment. The largest European wetlands are situated in the catchment: the Usinsky wetland between the Usa and Pechora Rivers and Martosheveksky wetland between the Pechora and Mylva Rivers.

The vegetation is mainly coniferous forest, the forest coverage increasing from 60% in the north to the 90% in south. In tundra and forest tundra that cover <30% of the catchment, the forests are thin and trees scattered. About 20% of the Pechora catchment is in the permafrost region (Bolshezemelskaya and Malozemelskaya tundra). In the extreme northeast, permafrost is continuous, its thickness reaching 250–300 m. The degree of intermediate permafrost increases southwestwards. On the left-bank of the Pechora River catchment, permafrost is either absent or only found in a few areas (Efimov & Zaitsev 1970). The large size of the Pechora catchment, both longitudinally and latitudinally as well as differences in relief, results in considerable climatic heterogeneity. The average annual air temperature is always below zero, decreasing from the southwest (1.0 to 1.3 C) to the northeast (3.5 to 5.0 C). The warmest month is July, the coldest is January or February. The absolute minimum temperature has been recorded in the Urals (55 C) and in the southern part of the catchment (54 C). The absolute maximum for the main part of the catchment is 34–35 C, in the northern part 31– 33 C. The earliest daily average air temperature above 0 C is in the southern part of the catchment (14–18 April), the latest in the Polar Urals (28 May). In autumn, the average air temperature falls below 0 C in southern parts of the catchment between 10 and 15 October, and in the north and in the mountains between 1 and 10 October. The average duration of the period with above 0 C temperature varies from the south to the northeast from 160–180 days to 125–150 days (Anon. 1989). The highest annual rainfall occurs on the slopes of the Urals (800–1000 mm), increasing with altitude (Kemmerikh 1961; Taskaev 1997). In the lowlands, precipitation increases from north to south, from 550 to 700 mm. About

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30–35% of the annual precipitation falls in winter, with a minimum in February and a maximum in October. The average date for snow cover is 7–10 October in the north, 28–30 September in the Polar Urals and 5–13 October in the rest of the region. The snow cover remains for about 190 days in the southwest and 230 days in the extreme northeast. Snowmelt starts in the middle of May in the southwest and at the beginning of June in the northeast (Anon. 1989). The oldest settlements in the catchment, including the communities of Pustozersk, Ust’-Tsylma and Izhma, were founded between the end of the 15th century and the middle of the 16th century. Until the 1930s, economic activity in the Pechora catchment was restricted to agriculture, deer ranching, logging, hunting and fishing. When major coalfields were discovered in the northern part of the Usa River catchment at the beginning of 1930s, the coal-mining industry was developed (Chernov 1989). In the coal mining areas, the cities of Vorkuta and Inta were founded, together with associated industries. At the same time, the first oilfield (1932) and gas field (1935) were discovered and industrial development started in the Timano–Pechorsky oil and gas bearing province in the Izhma River catchment. The most intensive development took place in the 1970s, based on the discovery of major oil and gas fields in the Bolshesemelskaya tundra, and Ukhta and Sosnogorsk in the Izhma catchment received new impetus for their development. In addition, new centres developed, including Naryan–Mar at the mouth of the Pechora River, Usinsk at the mouth of the Usa River and Vuktyl on the right bank of the middle Pechora River. At present, the energy industry plays a leading role in the regional economy. There are large thermal plants operating in Pechora, Vorkuta and Inta using local raw materials. The main railway in the Pechora region was built in the 1940s and connected the central Russian cities with the cities of the Komi Republic. A system of oil and gas pipelines was also developed. More traditional branches of the economy, the timber industry, agriculture and fishing, deer ranching and shipping developed simultaneously with these other industries.

River, the Pechora again turns north and flows in this direction until it reaches the sea. In the area from the Usa confluence and to the estuary, the left tributaries are typical taiga plains rivers, while the right tributaries originate in the Bolshezemelskaya tundra region. This part of the Pechora is called the Low Pechora (Stolpovsky 1999; Ilyina & Grakhov 1987). In montane and submontane parts of the catchment, the river flows in a narrow valley with steep sides. Lower down, from Rkm 1643, the river valley extends up to several kilometres forming vast floodplains covered with forests and meadows. In some places there are multiple channels, but when crossing hilly terrain it flows in narrow twisting valleys. Below the Usa confluence, the volume of water is almost doubled, and the watercourse is 2 km wide, with large numbers of channels and islands and floodplains of several kilometres in some places. At 130 km from the estuary, the river splits into two arms that down-river form the 45 km wide delta. The lower reaches of the Pechora are characterized by channel instability, wide floodplains and vast areas covered with shifting sand. The river is tidal up to 140 km from the sea (Stolpovsky 1999). The Pechora network consists of 34 570 streams and 62 140 lakes. The average stream frequency in the catchment is 0.48 km/km2, varying from 0.20 in the karst areas (Timansky Ridge) to 1.0 km/km2 in other regions. The total length of all streams in the catchment is 155 800 km, although 99% of the rivers are <50 km in length. There are 20 rivers >200 km in length. The largest lowland tributaries of the Pechora are:

9.9.2. Geomorphology, Hydrology and Hydrochemistry

*

The Pechora River originates from a small spring near the mountain of Pechor-Ya-Talyakh-Sekhal (‘The mountain which gave birth to the Pechora River’) in the northern Urals at 897 m asl. In the Urals, the Pechora is a typical mountain river with rapid flowing waters and stony substrates. The montane character of the Pechora continues until its confluence with the Ilych. Afterwards, and down to the estuary, it is a typical plains river. In the mountains, it flows west; then as it emerges from the mountains, it turns north. The Pechora then crosses the subzones of the middle and northern taiga, where forest cover is 85%, and bogs and wetlands comprise 10% of the area. Below the confluence with the Usa River, the Pechora turns west. Below the confluence with the Izhma

*

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Severnaya Mylva – left bank tributary, enters the Pechora at Rkm 1360 from the estuary; 213 km in length, catchment area 5970 km2, average altitude 174 m asl. In the catchment, forest coverage is 92%, wetlands cover 6%. The valley is 2–5 km wide, with a floodplain 1 km. The average slope is 0.00036 ppm. Kozhva – left tributary, enters the Pechora at Rkm 868; 194 km in length, catchment area 9560 km2. Forest coverage 95%, wetlands 4%; valley width 3–6 km, floodplain 1.0–1.5 km; average slope 0.00025 ppm. Izhma – the largest left bank tributary rises from the eastern slopes of the Timansky Ridge and enters the Pechora at Rkm 455. River length 531 km, catchment area 31 000 km2, mean altitude 141 m asl, average slope 0.00044 ppm. The river valley consists of several terraces; the width increasing from 2 to 12 km towards the confluence. The floodplain is discontinuous, 0.2–2.0 km in width. The catchment area is 90% forest and 6% wetland. Tsylma – the second largest left bank lowland tributary that rises on the eastern slopes of the Timansky Ridge and enters the Pechora River at Rkm 415. The river length is 374 km, catchment area 21 500 km2, average altitude137 m asl, and average slope 0.00040 ppm. The valley consists of several terraces, broadest towards the confluence. The floodplain width is 0.2–3.0 km. The

Chapter | 9 Arctic Rivers

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catchment is 73% forest and 14% wetlands, while in the north forest-tundra and tundra landscapes are prevalent. Sula – the lowest large left bank tributary of the Pechora, originating from Sul’skoye Lake situated in the Northen Timan. The river catchment is almost completely situated in the Nenets Autonomous Area within the Malozemellskaya tundra region. It runs into the Pechora at Rkm 41. The river length is 353 km, catchment area 10 400 km2, average altitude 92 m asl and average slope 0.00069 ppm. Forest covers 40% of the catchment, while 55% is tundra. The river valley is indistinct, reaching 10 km in width. The downstream floodplain is up to 2– 5 km wide.

All the major right bank tributaries from the western slope of the Ural Mountains until the Usa River flow into the Pechora. *

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Ilych – originates from a swamp in the Tima-Iz foothills (593 m asl) and flows into the Pechora at Rkm 1400 from the estuary. The river length is 411 km, and catchment area equals 16 000 km2. The upper reaches are between spurs of the Ydjydparma with maximum altitudes of 1195 m asl (Kozhymis) and 1096 m asl (Listovka). Near the catchment of the Pechora headwaters the river turns sharply west and crosses the mountains at the confluence. The average slope is 0.00058 ppm and the average altitude is 274 m asl. The major part of the catchment is hilly and 91% is covered in forest, much of which is boggy in the lowlands. The Ilych valley varies in width from 2 to 5 km, and the floodplain in middle and lower reaches is from 0.6–1.0 to 4–6 km wide. The larger part of the Ilych catchment is in the Pechoro-Ilychsky Nature Reserve. Shugor – originates in the slopes of the Yaruta Mountains at 720 m asl, and flows into the Pechora at Rkm 1037. The river length is 300 km, watershed area 9660 km2, and average slope 0.0024 ppm. The highest mountains in the catchment are Tel’posoz (1617 m asl), Khoriaz (1326 m asl) and Pedy (1001 m asl). The upper reaches flow from the south to the north; near the Pedy Mountains it turns sharply west. The upper reaches are characterized by high gradient and rapid flows and there are many rapids. After turning west, it is split into several minor channels in some places. Here the river flows in a broad (up to 10 km) mostly forest-covered valley; the floodplain is discontinuous. The Shugor River is protected as a part of the National Park ‘Yugyd Va’. Usa – the largest right bank tributary of the Pechora rises at the junction of the Malaya and Bolshaya Usa, flowing from the Polar Ural spurs and runs into the Pechora at Rkm 754. The river length is 565 km, catchment 93 600 km2, and the average river gradient decreases downstream from 0.0048 to 0.0011 ppm. The left bank Usa tributaries are mostly mountain rivers. The largest are the Lemva (9650 km2), the Kosyu (14 800 km2) and the Bolshaya Synya Rivers (4040 km2). The highest peak of the Urals, Gora Narod (1895 m asl) is in the catchment

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of the Kosyu River. The right bank tributaries rise in the Bolshezemelskaya tundra region. The largest are the Vorkuta (4550 km2), the Bolshaya Rogovaya (7290 km2), the Adz’va (10 600 km2) and the Kolva Rivers (18 100 km2). The tundra rivers originate in areas of permafrost, whose thickness reaches 250–300 m (Cherny 1970). The forests in the Usa catchment cover 10% of its area. The remainder is tundra, forest tundra, alpine areas and wetlands. The typical discharge regime of the Pechora and its tributaries include a high spring flood, with 60–68% of annual runoff in most rivers, low winter flows (5–7% of annual runoff) and a summer–autumn low flow period interrupted by relatively high rainwater floods (25–30% of annual runoff). The discharge pattern of rivers draining permafrost areas is rather different, with 71–80% of annual runoff occurring in the spring, only 1–3% during winter and 20–25% in the summer–autumn season. A more even discharge pattern is typical of karst rivers. A unimodal spring flood peak is typical of the lowland rivers of the Pechora catchment, in contrast to the mountain rivers where there are normally several peaks. The mean date for the onset and termination of the spring flood varies. In the south it begins around 15 April and ends around 31 May. In the north, the flood starts on about 15 May and ends on 1 July. Maximum water levels and discharge are recorded in most rivers during the period 20 May–5 June, although in mountane and tundra rivers the peak is 10–15 days later. Ice jams occur during the high water period in large and minor rivers as well as in the Pechora estuary that lead to water level rises of 1–3 m and flooding of adjacent areas (Zhila & Alyushinskaya 1972; Taskaev 1997). For most lowland rivers, the maximum specific runoff values are 70–120 l/s/km2, and for mountain rivers 300–400 L/s/km2. There are many gauging stations on the Pechora and its tributaries, between 66 and 75 have been in operation over the last 30 years, and 45 stations have representative data (Filippova 1985, Figure 9.3). The duration of the low water period decreases northeast from 120 days in Timan to 60 days in the subpolar Ural and Bolshezemelskaya tundra (Kokovkin 1988). In this period, groundwaters are the main water source. Typical winter runoff values vary from 3.5 to 4.0 L/s/km2 in the southern and central part of the Pechora catchment and the Urals to 0.1–0.2 L/s/km2 in the central part of the Bolshezemelskaya tundra (Kokovkin 1988) The winter low water period is 150–180 days in the southern part of the Pechora basin and 200–220 days at its northeast edge. The rivers are covered with ice 60–110 cm thick and small tundra rivers freeze to the bottom (Kokovkin 1997). The surface water chemistry and mineralization of the waters of the Pechora catchment vary considerably both with season and region (Vlasova 1988; Khokhlova 1994a). During winter, the chemistry is strongly influenced by the composition of the groundwater as this is the only water source. The general chemical characteristics for all rivers of the region include low mineralization of river waters in the

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spring floods (30–50 mg/L), summer and winter low-water periods (to 100–200 mg/L), predominance of bicarbonate and calcium ions, low water hardness during the whole year, high iron concentrations in most Taiga rivers (up to 2.2 mg/L), relatively high concentrations of phosphorous and nitrogen, as well as phenols, low iodide and fluoride concentrations, and pH varies between 6.0 and 8.0 during the year (Zhila & Alyushinskaya 1972; Vlasova 1988). The sources of right bank tributaries of the Pechora (Ilych, Podcherem, Shugor, upper Usa) are on the western slopes of the Urals. They have low mineralization levels (in the low water period <100 mg/L), favourable oxygen levels (100% saturation), and circum-neutral pH. Organic substances and nutrients are quite low. The right bank downstream tributaries of the Pechora River (Laya, Shapkina), as well as the Usa tributaries (Bolshaya Rogovaya, Adz’va, Kolva), flow through permafrost areas. Here mineral content is up to 250 in summer and 450 mg/L in winter, and even up to 1000 mg/L in the Vorkuta and Seida Rivers (Khokhlova 1994b). Higher levels of mineralization lead to an increasing share of sulphate and sodium ions. Boggy areas increase the concentrations of humic substances. The Pechora left bank tributaries (Velyu, Kozhva) and the Izhma right tributaries (Verkhny Odes, Nizhny Odes, Ayuva) crossing the Pechora lowlands also have moderate mineralization (73–100 mg/L), and a favourable oxygen regime. However, they have more humic substances and colour reaches 140 or more, permanganate values 20 mg/L and dichromate 80 mg/L. Ammonium nitrogen concentrations are also greater here (up to 1.8 mg/L) as well as iron compounds (up to 1.7 mg/L) (Vlasova 1988; Leshko & Khokhlova 2003). The left bank Timan tributaries of the Izhma (Sedyu, Ukhta, Kedva) are characterized by high water mineralization levels (up to 600 mg/L), with increased sulphate ions, and in the Ukhta also chloride (Kuchina 1955). TDS in the Pechora River vary from 15.2 (spring) to 630.6 mg/L (winter). The level of mineralization is relatively high in the section Troitsko–Pechorsk–Vyktyl, where it is dominated by calcium and bicarbonate ions. The Pechora River lies between the right and left tributaries level in terms of organic and biogenic substances. In the forest and swamps areas, as well as in the estuary, water colour increases up to 48 , permanganate up to 19.3 and dichromate up to 44 mg/L. Ammonium nitrogen concentrations vary from 0.14 to 1.83 mg/L and iron from 0.16 to 0.61 mg/L. During the open water period oxygenation is near saturation. In winter, however, there is lack of oxygen (21–59%), especially in downstream reaches. The pH varies from 6.1 to 7.9, but is mostly close to neutral.

9.9.3. Biodiversity Research on the biota of the Pechora River has taken place over a long period and there is considerable information on the biodiversity of the river and its catchment (Zvereva 1969; Taskaev 1997; Ponomarev et al. 2004a,b).

PART | I Rivers of Europe

In the montane areas of the upper Pechora River benthic algae are characterized by a diversity of diatoms (204 taxa), dominated by Cymbella, Achnanthes, Hannaea and Nitzschia (Stenina 2005). In tributary streams, the rheophilic taxa, Diatoma, Meridion, Didymosphenia, Gomphonema and Fragilaria occur. Filamentous red, green, yellow–green algae and Cyanobacteria are also common on stony substrates. In the river, its tributaries and floodplain lakes of the Middle and Lower Pechora there are more than 700 algal and cyanobacterial species (Chernov 1953; Getsen 1973; Shubina 1986; Patova & Stenina 2004); diatoms, green algae and Cyanobacteria are particularly diverse. In the phytoplankton, the predominant taxa are the diatoms, Aulacoseira, Asterionella, Melosira, Fragilaria and Nitzschia as well as the Cyanobacteria Aphanizomenon and Anabaena (Getsen 1971; Yenikeeva 1983). Mass algal and cyanobacterial blooms have been recorded in the river delta (Stenina et al. 2000; Stenina & Khokhlova 2004). In spite of high currents, the upstream areas of the Pechora are characterized by rich aquatic vegetation on account of stable bottom conditions. The main components are Petasites and aquatic mosses (Zvereva 1969; Shubina & Shubin 2002). In the reaches where water velocities are low, Sparganium, Potamogeton, Scirpus, Hippuris and Caltha thrive, in addition to horsetails and sedges (Zvereva 1969; Teteryuk 2004). The Middle Pechora is characterized by high diversity and abundance of macrophytes due to deep silty substrate (Zvereva 1971a). Batrachium, Butomus, Cicuta and Alisma grow near the river banks and aquatic mosses on the stony bottoms. The Lower Pechora is poor in macrophytes because of unstable channels, although individual stands of Potamogeton, Hydrocharis and Myriophyllum are present. Most macrophytes are concentrated in the backwaters and floodplain lakes (Zvereva 1969; Vekhov & Kuliev 1986). The banks of small shallow streams in the Pechora catchment are often colonised by sedges and willows, and 69 macrophyte species have been recorded from such streams (Rebristaya 1977; Teteryuk 2004). Zooplankton of the Upper Pechora is low in diversity and density (Tyutyunik 1983; Baranovskaya 1991; Shubina 1997; Fefilova 2002; Bogdanova 2004; Shubina 2004) due to high water velocity and stony substrata. Zooplankton is restricted to bank areas where low numbers of Biapertura, Acroperus, Alonella and Euchlanis are present. When stream velocities slow and macrophytes develop, the fauna becomes more diverse especially near the banks (77 species and forms). The key groups are Rotatoria, Cladocera, Copepoda, with Bosmina, Chydorus, Ceriodaphnia, Euchlanis, Sida and Eucyclops predominating. The Middle Pechora is characterized by higher zooplankton diversity (93 taxa) and abundance (Baranovskaya 1971). The most favourable areas are the floodplain lakes, where Bosmina, Chydorus, Euchlanis and Cyclops juveniles dominate. The average density in the Upper and Middle Pechora varies from 200 to 33 200/m3, and biomass varies from 0.05 mg/m3 to 91.0 mg/m3. The zooplankton community is heterogeneous, depending on

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the part of the Pechora watercourse and the flow (Zvereva 1969, 1971b; Shubina 2004). In the Lower Pechora, densities are up to 86 000/m3 and biomass up to 12.7 g/m3, with Copepoda and Cladocera dominant. Zoobenthos of the Pechora River catchment consists of many taxa, (Shubina 2004), the montane streams being especially rich in species. In the Upper Pechora, aquatic insects are numerous with Trichoptera, Ephemeroptera, Plecoptera and Diptera predominant (Shubina 1997; Shubina & Shubin 2002). Stony substrata and river banks are rich in molluscs, leeches, caddisflies, chironomids and other invertebrates. Zoobenthos of the Middle Pechora is dominated by chironomids, oligochaetes, benthic crustaceans, nematodes and mayflies (Zvereva 1969; Shubina 1997). The most developed invertebrate communities are found on stable stony substrata and macrophytes. The communities of the Lower Pechora and floodplain biotopes are most diverse in silty areas, where chironomids, oligochaetes and nematodes dominate (Zvereva 1969; Shubina 2004). Zoobenthos densities range from 100 to 26 900/m2 in different river sections, and biomass from 0.02 to 11.7 g/m2 (Shubina 1997; Shubina & Shubin 2002; Shubina 2004). A total of 55 molluscs species have been recorded from the Pechora (Leshko 1998), the genera Lymnaea and Anisus being dominant. The Pechora River is traditionally of great significance in terms of fisheries (Figure 9.5). A total of 33 fish species in 15 families form relatively sustainable populations, several undertaking migrations within the Pechora River and its tributaries (Ponomarev et al. 2004a,b). Siberian sturgeon, flounder, pink salmon and the taimen are also occasionally recorded in the Pechora River. The special value of the Pechora River fish population is a result of the dominant salmonids. These include migratory species (pink salmon, Atlantic salmon and pollan), semi-migratory species that never migrate to sea or even to the main channel of the Pechora or its main tributaries (vendace, powan, inconnu and smelt) and common non-migratory species that live only in one local region of the catchment (Arctic charr, broad whitefish, northern whitefish, grayling and Arctic grayling). Practically all European salmonids (12 species) are known from the river. Sterlet and pink salmon are non-native species in the Pechora River. One reptile and four amphibian species have been recorded in the Pechora catchment (Anufriev & Bobretsov 1996; Kuzmin 1999). Of these, four species are widespread in the catchment, while the European common toad is restricted to the plains of middle taiga. The fauna of nesting birds in the Pechora catchment contains representatives of 15 orders (Morozov 1987, 1989; Morozov & Kuliyev 1990; Yestafiev et al. 1995, 1999). Within the upper and middle reaches there are 171 nesting bird species. In the lower reaches, species diversity decreases, with 104 species in 8 orders found, and 40 species spend the winter in the region. The bird fauna is diverse and many species, including blackthroated accentor, lanceolate warbler, yellow-browed warbler, black-throated thrush, Siberian rubythroat, red-flanked

bluetail, white’s thrush, and Indian tree pipit are at the limits of their European range. Since the end of the 19th century, the range of >30 bird species has extended northwards (Kochanov 2001; Yestafiev 2005). There are 54 mammal species in the Pechora catchment (Geptner et al. 1961, 1967; Anufriev et al. 1994; Polezhaev et al. 1998; Bobretsov et al. 2004). Within the southern and middle part of the northern taiga there are 48 species, compared to only 26 species in the downstream reaches. The upper catchment forms the northern limit for bats, field voles, roe deer; and the middle and northern taiga form the northern limit for water shrew, pigmy shrew, raccoon dog and wild boar. In contrast, lemmings and arctic foxes inhabit the tundra areas. In the northern and subpolar Urals mountains, there are several colonies of the northern pika, Ochotona hyperborean. The western limit for the sable lies within the catchment. In the middle of the 20th century the muskrat was introduced and the non-native American mink and raccoon dog colonised the area from the south. At the beginning of the 20th century, beaver were reintroduced. The roe deer has not been recorded since the middle of the last century.

9.9.4. Management and Conservation The western slope of the Ural Mountains from the Ilych River to the Kozhim River (the Kosyu catchment) is a part of the Yugyd Va National Park. Recreational activities are being developed in the Park. In recent years the water quality of the Pechora River has been negatively affected, either as a result of insufficient waste-water treatment or due to industrial accidents. The continued development of the extensive energy resources of the region poses a continuing challenge for management, as well as being a potential threat to the pristine nature of much of the catchment. The macrophytes, Ranunculus pallasii and E. quinqueflora, are protected (Taskaev 1998). N. candida, N. tetragona, T. maritimum, Potamogeton filiformis, Ranunculus hyperboreus, R. pygmaeus and V. anagallis-aquatica are registered in the Pechora River catchment as potentially endangered species affected by anthropogenic activities (Tolmachev 1974–1977). Zoobenthic species diversity has also been reduced due to anthropogenic activities (Leshko & Khokhlova 1999). The fishes, Arctic grayling, Arctic charr, inconnu, taimen and bullhead are listed in the regional Red Books of the Komi Republic and Arkhanglesk region. In recent years negative changes in salmon species populations connected to anthropogenic impacts, such as industrial, agricultural and household pollution as well as poaching have been registered. The only species among the reptiles and amphibians in the Red Book of the Arkhangelsk region (Andreev 1995) and the Komi Republic (Taskaev 1998) is Salamandrella keyserlingii, a widespread species, but uncommon and present in low numbers. A total of 14 bird species are listed in the Red Book of the Russian Federation (white-billed diver, lesser whitefronted goose, Berwick’s swan, osprey, spotted eagle, golden

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eagle, white-tailed eagle, gyr falcon, peregrine falcon, oystercatcher, curlew, ivory gull, eagle owl and great grey shrike). An additional 39 species, which are declining in numbers or at the limits of their range north, are listed in the regional Red Books of the Komi Republic and Arkhangelsk region. Numerous species within the northern borders of the catchment are low in numbers and are listed in these regional Red Books. The American mink has attracted a great deal of attention with regard to endangered species. It has spread north and an increase in numbers threatens many native species. The Pechoro-Ilychsky Biosphere Nature Reserve, founded in 1930, is at the confluence of the Pechora and Ilych Rivers (Bobretsov et al. 2004). In 1994, the nearby Yugyd Va National Park, situated on the western slope of the Urals, was created. The main objective is to undertake research and protect the typical and unique flora and fauna of taiga-montane ecosystems of the region (Anufriev 2000; Ponomarev 2001). The nature reserve and National park are incorporated into the UNESCO Nature Heritage list. The Pechora Delta forms part of the Nenets State Nature Reserve founded in 1997, and boarders on the Nenetsky State Nature Sanctuary founded in 1985. The key activity of these protected areas is the protection and study of endangered animal and plant species in the typical ecosystems of the eastern European tundra and the Barents Sea coastal waters. In addition, there are nine fish sanctuaries and four aquatic nature reserves in the Pechora catchment (Taskaev et al. 1996).

The river partly originates from a glacier and runs down a Ushaped valley formed during the last Ice Age. The size of the catchment is 187 km2 (Adalsteinsson & Gıslason 1998). The Tertiary bedrock is impermeable and most runoff flows directly into the river along the bottom of the valley. Discharge varies from day to day depending on precipitation, especially during autumn, as well as seasonally. Discharge is greatest in spring, summer and autumn, with discharge of 30–50 m3/s, while winter discharge ranges from 5 to 15 m3/s. There is also variation in annual mean discharge, from 10 m3/s in 1971 to 25 m3/s in 1976, reflecting annual precipitation. Conductivity is low, between 17 and 30 mS/cm, lowest in the upper reaches and highest in the lower reaches. pH varies from 7.4 in the upper reaches to 8.0 in the lower reaches. Nutrients are low as the river is on an ancient bedrock formation (>10 million years old). In September 1995 PO4-P was 11.2–15.8 mg/L in all reaches and total N was 62.6 mg/L, 47.0 mg/L and 4.0 mg/L in upper, middle and lower reaches, respecitively. NO3 was by far the highest constituent, 55.9 mg/L, 40.7 mg/L and 40.0 mg/L in the upper, middle and lower reaches, respectively.

RIVER 9.10. THE GEITHELLNAA

9.10.3. Biodiversity

9.10.1. Physiography, Climate and Land Use

Chironomids are most abundant of all invertebrates (Larusdottir et al. 2000), with densities ranging from 8000 to 36 000 /m2, with lowest numbers in the upper reaches. The proportion of Chironomidae larvae in the benthos varies little, between 97.5% in the upper reaches to 99.9% in the middle and lower reaches. The blackfly, Simulium vittatum, has been recorded in window traps in all reaches. The number of chironomid species in window traps (Jonsson et al. 1986) was 12, 15 and 16 in the upper, middle and lower reaches, respectively. They all belonged to Diamesa and Orthocladiinae, except a single specimen of Tanytarsus gracilentus recorded in the upper reaches (Olafsson et al. 2002). Although no catch statistics are available for fish, Arctic charr (S. alpinus) have been caught in the river by electrofishing.

The Geithellnaa is a third order direct runoff river in eastern Iceland at 64 350 N, 14 450 W. The catchment is characterized by Tertiary bedrock (Johannesson & SI`mundsson 1998). As a runoff river, it collects water from the highlands eastnortheast of the Vatnaj€ okull Ice Sheet and flows along a 25 km long and narrow valley Geithellnadalur, excavated during the last Ice Age. The majority of the water in the highlands comes from a small icecap east of Vatnaj€okull, the Thorisj€ okull. The mean air temperature in the upper reaches is 1.1 C and at sea level 3.9 C. The coldest month in the highland catchment is February with a mean temperature of 7.8 C, while at sea level it is 0.1 C in January. The warmest month is July in the highland catchment with mean temperature 7.8 C and August at sea level with mean temperature 9.1 C. Precipitation data are only available for the lower reaches, averaging 1312 mm, with May being the driest month and October the wettest. Only 54.5% of the total catchment is covered with vegetation, with 2% coverage in the upper reaches and 11% in the middle reaches. Agricultural land is limited and covers only about 0.5% of the lower reaches, although the area of farm land was much greater

prior to the 20th century. Today, only six people live on a farm in the lower reaches, giving a population density here of 0.03 persons/km2.

9.10.2. Geomorphology, Hydrology and Biogeochemistry

RIVER 9.11. THE LAXA The River Laxa is a third order river. It drains Lake Myvatn and flows 58 km northwards to the sea. M yvatn is located in the northeastern part of Iceland at around 65 350 N, 17 000 W and 277 m asl. It is fed by many cold and warm springs containing high levels of phosphorous

Chapter | 9 Arctic Rivers

367

PHOTO 9.7 (a) The Bruarfossar waterfalls in the River Laxa in 1912 (Photo: W.H. Lamblon, District Museum, Husavik). (b) The Bruarfossar waterfalls in the River Laxa 2006. Power plants were built here during the period 1939 to 1973 (see text) (Photo: G. Gudbergsson).

and nitrogen. Subsided lava and a lava dam form the basin of lake M yvatn, and lava also partially forms the bed of the Laxa. Both Lake M yvatn and the Laxa have been extensively studied (Photo 9.7).

9.11.1. Climate and Land Use The climate of Iceland is oceanic, but inland, especially in the northeast, it is more continental in character (Einarsson 1979). The annual mean air temperature is 1.7 C at M yvatn, 2.3 C in the middle reaches of the Laxa and 2.6 C at sea level. The average temperature for July, the warmest month, is highest at Lake M yvatn, 10.4 C, compared to 10.1 C in the middle reaches of the Laxa and 9.9 C at sea level (Icelandic Meteorological Office).

During the coldest month, January, the mean temperature at Myvatn is 4.4 C, in the middle reaches 3.2 C of the Laxa and 2.7 at sea level. The Myvatn area is in the part of Iceland with the lowest precipitation (Einarsson 1979), largely due to being in the rain shadow of the Vatnaj€okull Ice Sheet. The average annual precipitation at Lake Myvatn is 435 mm, but increases to 563 mm at sea level. At Myvatn, the lowest precipitation is in May and highest in October, but at sea level it is lowest in April and highest in June. The human population is mainly restricted to the area around Lake Myvatn, with a small village on the north shore of the lake. Farms are also located on the shores of Myvatn and on the shores of Lake GrI`navatn, in the lower reaches of the tributary River Kraka and along the banks of the Laxa. The population density at the upper reaches of the Laxa is

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0.3 persons/ km2, compared to 1.3 persons/km2 in the middle and lower catchment areas.

in winter, and low or almost depleted during summer due to uptake by algae.

9.11.2. Geomorphology, Hydrology and Biogeochemistry

9.11.3. Biodiversity

The Laxa River flows out of M yvatn, a shallow lake with an area of 37 km2 in the volcanic zone of northeast Iceland. M yvatn is fed by warm and cold springs on its eastern shores and by Lake GrI`navatn, a short distance to the south. Its theoretical retention time is 27 days with a mean outflow to the Laxa of 33 m3/s (Olafsson 1979a; Rist 1979a). The warm spring water is rich in nitrogen and the cold spring waters are rich in phosphorus (Olafsson 1979b). High solar radiation and nutrients in the spring water render Lake Myvatn as one of the most productive lakes in northern Europe (Jonasson 1979a). The Laxa River can be divided into two parts, the upper 33 km from M yvatn to the Bruafossar waterfalls (Photo 9.7), and the lower 26 km from the waterfalls to the Arctic Ocean. The Bruafossar waterfalls in the Laxargljufur canyon are impassable to fish. The mean discharge of the Laxa where it enters the sea is 55 m3/s (Rist 1979a). The river bed consists of lava with boulders (diameter 20–50 cm), stones (10–20 cm), gravel and sand (<10 cm). yvatn has only 17% vegetaThe 1359 km2 catchment of M tion cover. The catchment of the Laxa (including the catchment of M yvatn) covers 2385 km2, 39% of which is covered with vegetation. The Laxa’s tributaries have higher vegetation cover, ranging from 25% to 88% (Gıslason 1994), increasing at lower altitudes. The discharge of the Laxa is stable and floods rarely occur. In the spring thaw in May, discharge increases by about 35% and occasionally (about every 6–7 years) as much as 100% (Hydrology Department of the National Energy Authority, Gıslason 1994). Lake M yvatn is usually covered with ice from October or November until May, or sometimes to early June, with average duration of 189 days a year (Rist 1979b). Conductivity in the Laxa is high. In the outlet in 1977– 1978, it was 151–193 mS/cm, although slightly lower downstream (141–166 mS/cm). The pH of the Laxa varies between 7.7 and 9.3. Nutrients, originating in spring water in the source Lake M yvatn, fluctuate seasonally, mainly due to production in the lake (Table 9.2). They are high

A total of 52 invertebrate taxa have been identified from the Laxa, (Gıslason 1994; Olafsson et al. 2004; Thorarinsson et al. 2004). The blackfly, S. vittatum (Simuliidae), is the most abundant benthic invertebrate in the outlet from Myvatn. The stomach contents of blackfly larvae reflect the seston composition in the river, mainly drifting algae and detritus from the lake (Gıslason & Johannsson 1991). Further downstream, chironomid larvae are the most abundant benthic invertebrate group (Gıslason 1994). Chironomidae account for 27 of the 52 benthic species in the river. In the upper reaches of the river, 19 chironomid species have been recorded from window traps, compared to 23 and 25 species in the middle and lower reaches, respectively (Gıslason et al. 1995). The density of invertebrates in August 1978 was estimated at 132 500 /m2 near the outlet, falling to 97 700 /m2 in the middle reaches and increasing to 195 500 /m2 further downstream (Thorarinsson et al. 2004), after the river had flowed through a wide channel that reduced the water velocity to about 0.4 m/s (Jonasson 1979b). The vertebrate fauna of the upper river is characterized by a landlocked brown trout (S. trutta) population and two duck species, Barrow’s goldeneye (Bucephala islandica) and the harlequin duck (Histrionicus histrionicus) (Einarsson et al. 2006). In the upper part, S. vittatum constitutes about 60% of the diet of the brown trout regardless of fish size (Steingrımsson & Gıslason 2002). The relative contribution of S. vittatum to the diet declines downstream from Myvatn. The seasonal variation in stomach contents of brown trout reflects the different number of generations of S. vittatum in the upper and lower parts of the river (Gıslason & Steingrımsson 2004). S. vittatum has two generations per year in the upper part, whereas only one generation per year emerges in the lower river. In the lower reaches of the Laxa, Atlantic Salmon (S. salar) is the most common fish species caught, with anadromous brown trout being nearly as abundant, together with a small number of anadromous Arctic charr (S. alpinus). The Harlequin duck is also common in the lower reaches of the river (Gardarsson 1979).

TABLE 9.2 Nutrients (PO4-P, NO3-N and SiO2-Si) in the River Lax a, at the outlet of Lake M yvatn, in the middle reaches (33 km from outlet) and lower reaches (58 km from the river mouth)

Outlet Middle reaches Lower reaches

PO4-P (mg/L)

NO3-N (mg/L)

SiO2-Si (mg/L)

3.10–45.22 2.17–19.82 3.41–11.37

0.14–38.52 0.84–47.34 0.98–5.04

1.12–10.78 2.53–10.45 3.00–6.88

´ lafsson (1979b) and Eirıksdo´ttir et al. (2008). Data from O

369

Chapter | 9 Arctic Rivers

9.11.4. Management and Conservation

9.12.1. Physiography, Climate and Land Use

In 1939, a power station (5 MW) was built by the town of Akureyri on the Laxa 30 km downstream from Lake M yvatn. It uses the upper part of the 39 m high Bruar waterfalls. A dam diverts the water to the station’s intake, but there is no storage reservoir above the dam. Another power station (9 MW) became operational in 1953, and uses the lower part of the waterfalls, with a head of 29 m. There is also a small dam to divert the water to the intake of the station. Construction of a third power station began in 1970 and was intended to be 25 MW. It was to use the same inflow as the initial station, but be hidden inside the mountain, and with a 56 m high dam on the river that would have inundated about 15 km of the valley. This led to a dispute between farmers and environmentalists, on the one side, and the Akureyri Power Company and the government on the other. The dispute ended up with a settlement that lead to a 13.5 MW power station below the existing dam for the initial power station and using the same head of water. Limnological research on lake M yvatn and the Laxa (Jonasson 1979a) gave rise to the legislation embodied in the M yvatn and Laxa Conservation Act (1974), covering the entire Lake M yvatn catchment and the Laxa with 200 m buffer zones on each bank. In accordance with the Act, the M yvatn Research Station was established in 1974 on the banks of the M yvatn. The station has formed the basis for further research on the lake and the Laxa. In 1977, M yvatn-Laxa was the first wetland in Iceland to be designated on the Ramsar list (Convention on Wetlands of International Importance especially as waterfowl habitat) for its diverse biota and wealth of waterfowl (Gıslason 1998). The size of the designated area is 200 km2 and covers lake M yvatn and the Laxa, all wetlands in the catchment and a large area around lake M yvatn, and a 200-m buffer zone on each side of the Laxa (http://www. ramsar.org/profile/profiles_iceland.htm). In 2004, the protected area was reduced by revision of the Myvatn and Laxa Conservation Act, from the whole catchment of lake M yvatn to a 200 m zone along the banks of Lake Myvatn and adjacent wetlands, a total of 153 km2. There are plans, not yet put into force, to significantly increase this protected area.

The Vestari J€okulsa flows north across the central highland plateau and reaches the lowlands about 40 km from the glacier snout. The mean annual temperature for the upper reaches is 2.1 C (Icelandic Meteorological Office), and mean monthly temperatures from June to September are above 0 C. The warmest month is July with a mean temperature of 7.1 C and January the coldest with a mean of 8.3 C. Temperatures increase downstream and in the lower reaches the mean annual temperature is 2.8 C, the mean July temperature is 10.1 C and the mean January temperature is 2.6 C. Annual precipitation varies from 380 mm in the lowlands to 727 mm in the upper reaches, with May being the driest month. The river runs through a barren catchment with little or no vegetation cover in the upper reaches. In the middle reaches vegetation cover is about 4% and in the lower reaches 93%, with an overall vegetation cover of 48% (Gıslason et al. 2001, Photo 9.8). There is no forest in the area. There are small patches of vegetated land in the upper and lower reaches, notably near the spring-fed tributary, Midhlutara, that is used as summer pasture for sheep. The lower parts of the catchment serve as pasture for sheep and cattle. Cultivated land is restricted to the lower reaches and its cover is <1%. Human settlement is also limited to the lower reaches where the population density is about 0.05 individuals/km2. There are no forests and only small wetlands are found around Vestari J€ okulsa and its tributaries.

€ RIVER 9.12. THE VESTARI JOKULS A The Vestari J€ okulsa is a typical glacier-fed river. It is a fourth order river that originates from the glacier, Satuj€okull, an outlet glacier from the Hofsj€ okull Ice Sheet at an altitude of 860 m asl in northern Iceland. The middle section is located at 65 160 N, 19 050 W. It was well studied in the late 1990s under the auspices of a cooperative European project on glacier-fed rivers (Brittain & Milner 2001; Gıslason et al. 2001).

9.12.2. Geomorphology, Hydrology and Biogeochemistry The Vestari J€okulsa originates as three main branches (eastern, middle and western branch) from the northwest outlet glacier, Satuj€okull, part of the Hofsj€okull Ice Sheet. A hyaloclastite mountain ridge separates the eastern branch from the others. A fissure zone assumed to be connected with a central volcano below the glacier (Bj€ornsson 1988; Sigurdsson 1990) cuts through the area. The river flows with a gradient of 5–10 for most of the way from the glacier to the lowlands, except between the edge of the highland plateau and the lowlands, where its slope increases to around 20. The glacier catchment area of the river is 90 km2 compared to the 820 km2 at the lowest gauging station in the lowland valley, 45 km away from the glacier. The annual average discharge (1971–1997) at the lowest sampling site of the river is 21.4 m3/s (Gauging station no. 145, National Energy Authority in Iceland, Hydrological Survey). TDS, deduced from conductivity, indicate that the middle branch is fed by meltwater originating directly or interacting with the assumed volcanic area, as its mineral content is already high (>50 mS/cm) in July, while the other branches have conductivity as low as 10 mS/cm (Gıslason et al. 2000). The eastern branch, close to the

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PART | I Rivers of Europe

PHOTO 9.8 The River VestariJ€okulsa near its confluence with the tribuatary Hofsa, seen from termial moraines from the end of the last Ice Age (Photo: G.M. Gıslason).

glacier, was dominated by clear meltwater in July 1997, but in September the same year all branches were highly turbid. The conductivity in the eastern branch remained low, while the conductivity in other branches was higher (>40 mS/cm), which indicates that the glacial meltwater was mixed with geothermal water. In mid-winter, the Vestari J€ okulsa is mainly spring fed and at the upper gauging station summer discharge decreases from 30– 40 m3/s to <1 m3/s in winter. In the lower reaches the discharge is typically 15 m3/s in winter and 35–50 m3/s in summer. At such discharges, TDS commonly vary between 65 and 80 mg/l, which corresponds to 90–120 mS/ cm (Adalsteinsson et al. 2000), similar to that estimated as the groundwater component late in the summer season. The conductivity varied from 8 mS/cm at the glacier snout to 113 mS/cm in the lower reaches, while pH was 6.0–6.7 near the glacier snout, 7.2–7.4 in the middle reaches and 7.7–7.8 in the lower reaches (Gıslason et al. 2000). Nutrients were low in all reaches, highest in onset of winter and lowest in mid-summer. They were higher in a branch from the glacier with geothermal influence than other glacier outlets (Table 9.3). Total N was varied, but NO3 was low, 0– 1.0 mg/L in upper and middle reaches and 0–5.9 mg/L in

lower reaches. N was also present as NO2 and NH4, ammonia values being higher Suspended solids vary considerably with season and between branches. Close to the junction of the branches, 22.5 km from the glacier, suspended solids vary between 100 and 1200 mg/L. Suspended solids subsequently decrease to 85 mg/L in the lowlands (Gıslason et al. 2001). During summer, chlorophyll a increases from 0.1 mg/m2 at the glacier snout to 1.6 mg /m2 1.4 km from the glacier, declining again to 0.1 mg/m2 at 7.5 km from the glacier and increasing again downstream to 0.16 mg/m2. These changes are associated with decreasing proportion of glacial melt water that was 50% in the uppermost reaches of the river and only 20% 42 km downstream, when tributaries and groundwater have entered the river (Adalsteinsson et al. 2000). Channel stability, expressed by the Pfankuch index, declines downstream from 55 to 21–35, indicating greater channel stability at increasing distance downstream. Maximum water temperatures recorded over the summer increase downstream, from around 0 C at the glacier snout to approximately 12–14 C 4.5 km downstream. Higher values, up to 17.3 C, were recorded in some of the tributaries.

TABLE9.3 Nutrients (PO4-P, NO3-N and SiO2-Si) in the River Vestari-J€ okuls a, in upper reaches (close to glacier snout), the middle ranges (22 km from glacier) and lower reaches (45 km from the glacier) (unpublished data)

Upper reaches Upper reaches with geothermal influence Middle reaches Lower reaches

PO4-P (mg/L)

Total N (mg/L)

SiO2-Si (mg/L)

0–2.8 0–22.1 0–17.7 0–35.6

7.7–18.4 7.0–30.5 7.0–31.0 6.4–40.6

1.39–4.5 2.9–5.5 7.1–11.5 11.2–17.2

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Chapter | 9 Arctic Rivers

9.12.3. Biodiversity

9.13. THE BAYELVA RIVER

There is considerable seasonal and annual variation in the density of major macroinvertebrate groups in the Vestari J€ okulsa. Density and composition change significantly along the downstream gradient, with higher densities and diversities with increasing distance from the glacier margin. Chironomidae are the dominating taxon at all sampling sites (Olafsson et al. 2000). In the upper reaches, nine chironomid species were recorded in window traps: of those, three were Diamesa, five Orthocladiinae (Chaetocladius, Cricotopus, Eukiefferiella and Metriocnemus) and one Simuliidae (Simulium vittatum). In the middle reaches, 6 chironomid species were found and in the lower reaches 12 species. All the species belonged to Diamesa and Orthocladiinae. S. vittatum, presumably originating from non-glacial streams, was also recorded in the middle and lower reaches (Gıslason et al. 2001).The density of chironomid larvae increased significantly downstream, from 29 to 5877/m2 (upstream and downstream, respectively). The upstream chironomid assemblages are dominated by the genus Diamesa, whereas Orthocladiinae and Tanytarsini dominated lowland reaches (Olafsson et al. 2000; Gıslason et al. 2001). The only fish species found in the main Vestari J€okulsa is Arctic charr. These are generally small-sized individuals and their size at sexual maturity is <15 cm. Atlantic salmon were caught in small numbers (2–23 annually) from 1974 to 1982 in the tributary Hofsa. This was during a period when salmon were commonly released into rivers to increase the salmon run. At least one of the tributaries, the River Svarta, confluent with the Vestari J€ okulsa 45 km from the sea, has always been known for its good salmon run.

Bayelva, otherwise known as the Red River because of the high levels of coloured glacial sediment, is located at 79 N, 12 E, in the Kongsfjord on the western part of the island of Spitsbergen. The catchment area is 33 km2, of which 55% is glaciated (Brittain & Milner 2001). The highest point of the catchment is 742 m asl. The main sources of Bayelva are two small polythermal glaciers, Austre Brøggerbreen (11.7 km2) and Vestre Brøggebreen (5.3 km2) (Photo 9.9).

9.13.1. Physiography, Climate and Land Use The bedrock is sedimentary: limestone, shale and sandstone. The upper parts of the catchment are dominated by glacier, bare rocks and extensive recent moraine material, while tundra vegetation has become established in some areas near the fjord. The landscape is alpine with both cirque glaciers and large valley glaciers, some of which reach the sea. The scientific station of Ny-A lesund, the world’s northernmost permanent settlement, on the Kongsfjord, 2 km to the east of the catchment, has an annual mean air temperature of 6.3 C and a July mean of 4.9 C. Precipitation is low with an annual mean of 385 mm recorded in Ny-A lesund, although calculations adjusted for the increase in precipitation with altitude indicate a mean annual precipitation for the Bayelva catchment of 890 mm (Killingtveit et al. 2003). There is no permanent habitation within the catchment. There is a small recreational cabin near the gauging station that is located 600 m from the outflow into the fjord. Coal mining was carried out in to the area up until the early 1960s, PHOTO 9.9 Bayelva and the source glaciers, Austre and Vestre Brøggebreen (Photo: J. E. Brittain).

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PART | I Rivers of Europe

FIGURE 9.6 Annual sediment transport (suspended load) and mean water discharge in Bayelva.

but is now abandoned. In the Bayelva catchment there are only small vestiges of this activity in the form of tracks, timber and small excavations. Today the catchment is used for research carried out from Ny-A lesund. A small lake in the catchment, Tvillingvatn, is used as the water supply for Ny-A lesund. A small airstrip is located on the eastern edge of the catchment.

9.13.2. Geomorphology, Hydrology and Biogeochemistry Most meltwaters leave the glacier via large lateral channels to which fine sediments are supplied by mass wasting of icecored moraines at about 100 m asl (Hodson et al. 1998). The channels from these two glaciers converge after about 1 km and the river then flows a further 2 km down to the fjord, alternating between single and braided channels as it breaks though recent terminal moraines. As is typical of glacier-fed rivers, the substrate is unstable (Castella et al. 2001). There are two main tributaries, Tvillingvassbekken and Mørebekken, both of which carry little sediment. Tvillingvassbekken flows out of a small shallow lake Tvillingvatn (area 0.35 km2; maximum depth 6.3 m), while the waters of Mørebekken are filtered through extensive terminal moraines. Normally, there is no runoff in Bayelva from early October until the end of May. Snowmelt, and glacial meltwater later, leads to intense flows in June, July and August. Due to rainfall, high floods can occur during late summer and early autumn. In some years, runoff has occurred in late autumn and early winter as a result of the intrusion of Atlantic air into the Arctic Basin. At the gauging station in Bayelva, the world’s northernmost permanent facility, the mean annual discharge is 1.12 m3/s (specific discharge 36.2 L/s/km2). The highest observed flood was in mid-September 1990 with a daily discharge of 32 m3/s. The annual water balance for the whole Bayelva catchment has been estimated for the period 1990– 2001 by Killingtveit et al. (2003), based on a wide range of data, both from the Bayelva catchment and other catchments

on Svalbard. The following mean annual estimates were calculated: precipitation 890 mm (summer 277 mm; winter 597 mm), evaporation 37 mm, runoff as a result of negative glacial mass balance 245 mm and runoff 1050 mm. This gives an error term of 31 mm. The Bayelva freezes to the stream bed each winter from September/October to end of May. From mid/late June to late August the river is free of ice. The water temperature is low and normally does not exceed 4 C. The temperature maximum occurs in early July and freeze up starts some time in September. The sediment load in the Bayelva is delivered by the polythermal glaciers Austre and Vestre Brøggerbreen as well as eroded material from moraine areas surrounding the glaciers. The total annual suspended load during the period of measurement (1989–2001) shows large year-to-year variation (Photo 9.6). The highest load on record was 23 000 tons in 1990, due to a huge flood in September that year. Exhaustion effects meant that sediment transport did not reach the same level until some years later. The mean specific sediment yield of the glacier and the moraine area has been estimated at 586 tons/km2/year (Bogen & Bønsnes 2003). The sediment concentrations are also subject to large seasonal variations. Late in the summer season when the runoff originates from glacial meltwater, the mean suspended sediment concentrations are often about 100–300 mg/L. The huge flood in September 1990 gave a concentration of 4000 mg/L. Rainwater floods in August and September often give rise to high sediment loads. From 1920 to 1930, Lake Tvillingvatn received groundwater from a sandstone aquifer underlying the lake. Recent water balance studies indicate that that there is no longer any groundwater flow of that type (Haldorsen et al. 2002). Previous melting of the permafrost along the glacial front of Brøggerbreen as a result of large amounts of meltwater and a steep hydraulic gradient may have been halted as the glacier retreated and exposed the glacial forelands to renewed permafrost. The river waters are circumneutral. Calcium and magnesium are the major cations, while bicarbonate concentrations are relatively high in relation to other anions. Conductivity is typically 40–80 mS/cm (Lods-Crozet et al.

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Chapter | 9 Arctic Rivers

2001). The major controls on hydrochemistry in the catchment include snowpack solute elution, rapid alteration of minerals via surface reactions and slow, incongruent silicate dissolution (Hodson et al. 2002). The importance of chemical weathering increases downstream. The restricted sub-glacial weathering, because of the largely cold-based thermal regime of the glaciers, means that the proglacial areas are the most important zones of solute acquisition by meltwaters, causing significant enrichment of major ions, silica and dissolved CO2 within only a short distance from the ice margin (Hodson et al. 2002).

9.13.3. Biodiversity The geographical isolation of the Svalbard archipelago limits the available species pool (Milner et al. 2001; Coulson & Refseth 2004). Water temperatures are low and the substrate is unstable, giving a benthic fauna low in numbers and poor in species, and composed almost exclusively of chironomids (Diamesinae and Orthocladiinae) and oligochaetes (Castella et al. 2001; Lods-Crozet et al. 2001, 2007). Periphyton is the main food source and chlorophyll a concentrations may reach values over 10 mg/m2 in the shallow waters of the downstream reaches during the period of continuous daylight (Lods-Crozet et al. 2001). Arctic charr occur throughout much of Svalbard (Klementsen et al. 2003; Svenning & Gullestad 2002), but not in the Bayelva river system as there are no accessible lakes to maintain a population during winter.

9.13.4. Management and Conservation While the catchment is not included in any of the designated National Parks, there are strict environmental regulations governing the whole of Svalbard. Owing to its accessibility and infrastructure, the area around Ny-A lesund is a centre for international Arctic research over a wide range of disciplines (www.kingsbay.no).

Acknowledgements Randi Pytte Asvall kindly provided information on ice condition in the Altaelva River. We wish to acknowledge the help of Eero Niemel€a for providing information on the Tana salmon fishery and Steinar Pedersen for his input to the social history of the Tana River. Tharan Fergus has also provided information on sediment characteristics of the Tana River. We are indebdted to Trausti Jonsson, Icelandic Meteorological Office for providing weather data for all Icelandic catchment areas and Bj€ orn Traustason for compiling the data on forest cover of Icelandic catchments. The Hydrological Service of the National Energy Authority provided digital maps of catchment areas of the Icelandic rivers. Thanks also Einarsson, M to Dr. Arni yvatn Research Station, for reading and commenting on parts of the manuscript.

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PART | I Rivers of Europe

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RELEVANT WEBSITES www.seNorge.no Snow, weather, water and climate in Norway http://www.nve.no Hydrology and watercourse management http://www.hi.is/HI/Stofn/Myvatn/engframe.htm Web site on Lake Myvatn and the River Laxa, Iceland http://www.polarenvironment.no Polar Environment Centre, Tromsø, Norway http://www.environment.no State of the Environment Norway http://www.bafg.de/servlet/is/2491/?lang=en Arctic runoff database http://www.acia.uaf.edu/ Arctic Climate Impact Assessment http://www.amap.no/ Arctic Monitoring and Assessment Programme http://www.arctic.noaa.gov/detect/land-river.shtml A Near-Real Arctic Change Indicator Website

Chapter 10

British and Irish Rivers Chris Soulsby

Doerthe Tetzlaff

Chris N. Gibbins

School of Geosciences, University of Aberdeen, Aberdeen AB24 3UF, UK

School of Geosciences, University of Aberdeen, Aberdeen AB24 3UF, UK

School of Geosciences, University of Aberdeen, Aberdeen AB24 3UF, UK

Iain A. Malcolm Fisheries Research Services Freshwater Laboratory, Pitlochry, Perthshire PH16 8BB, UK

10.1. 10.2.

10.3.

10.4.

10.5.

10.6.

10.7.

Introduction Biogeographic Setting 10.2.1. General Aspects 10.2.2. Palaeo-Geography Physiography, Climate and Land Use 10.3.1. Landforms and Geology 10.3.2. Climate 10.3.3. Land Use Patterns Geomorphology, Hydrology and Biogeochemistry 10.4.1. Geomorphology 10.4.2. Hydrological Regime 10.4.3. Biogeochemistry Aquatic and Riparian Biodiversity 10.5.1. Macrophytes 10.5.2. Macroinvertebrates, Reptiles and Amphibians 10.5.3. Mammals and Birds 10.5.4. Fisheries Management and Conservation 10.6.1. Economic Importance 10.6.2. Conservation and Restoration 10.6.3. Catchment and River Basin Planning Conclusions and Perspectives References

10.1. INTRODUCTION The British Isles, comprising the United Kingdom (Scotland, England, Wales, and Northern Ireland) and the Republic of Ireland, occupy the northwest Atlantic seaboard of Europe. The latitude and longitude of the area ranges from around 50 N to 61 N and 2 E to 11 W, respectively. As the land Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

masses of both mainland Britain and the island of Ireland are of limited spatial extent, nowhere is far from the sea and the rivers are relatively small in comparison with continental Europe. Despite this, the area has marked differences in climate, geology and population densities that result in a diverse range of rivers with distinctive physical, chemical and ecological characteristics and varying degrees of human impact. In this chapter, we examine some representative rivers of the British Isles that encompass much of this geographical diversity (Figure 10.1, Table 10.1). These include the northern rivers of the Spey, Tay and Tweed that drain mountainous parts of Scotland. In England and Wales, the focus shifts initially to rural rivers that have upland headwaters but also more marked lowland influences, including the Severn and Wye. Those rivers that drain catchments with more dominant urban influences are then assessed such as the Mersey: historically one of the UK’s most polluted rivers draining the industrial heartlands of northwest England. Similar urban influences characterize many sub-catchments of the Ouse– Trent system that drains industrialized parts of northern England and the Midlands. Human influences are even stronger in the Thames catchment, focused around London, which drains the most densely populated and economically important region of the British Isles. In contrast, the small Frome– Piddle river in southern England shifts attention back to lowland catchments, albeit of a much more rural character. The river Shannon is the largest river system considered and lies within the Republic of Ireland. It has a distinct history and quite different character to the rivers on the British mainland. Descriptions of these rivers will be embedded within a wider systematic consideration of the environmental characteristics of the British Isles. After describing the general geographical setting of the region, we outline the main 381

382

PART | I Rivers of Europe

FIGURE 10.1 Digital elevation model (upper panel) and drainage network (lower panel) of the British and Irish Rivers.

topographic, climatic and land use characteristics of this area. The way in which these factors produce a wide spectrum of geomorphic, hydrological and biogeochemical characteristics of these rivers is examined. The manner in which this physico-chemical template affects the biodiversity of riverine and freshwater habitats is also considered. We also assess how a long legacy of increasingly intense human– environment interactions have affected these rivers and

how future environmental changes are likely to be mediated by the increasingly sophisticated institutional arrangements that have evolved for their sustainable management. In the course of a relatively short-chapter, it is clear that the coverage will often merely scratch the surface of the extensive and detailed body of research papers and management plans for many of these rivers and the reader is referred to the various references for further detail.

Spey Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25 %) ecological regions Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparse vegetation Wetland Freshwater bodies

Tay

Tweed

442 3007

377 5260

2.0 124.4 5.8 2 11

5.3 160.9 5.9 2 11; 17

251 5037 2.5

Ouse 155 8925 1.6

Trent

Thames

111 10 466

94 13 470

0.9

2.1

Frome and Piddle 103 643 0.2

Severn 137 10 589 3.3

Wye

Mersey

214 4123

159 2300

Shannon 95 16 120

96.1 7.6 1 17

94.7 8.1 1 17

74.6 8.9 1 17

69.9 9.4 2 33

86.4 9.8 2 33

85.5 8.8 2 17

2.3 109.3 8.6 2 17

1.2 100.5 8.7 1 17

7.0 102.2 9.1 2 17

0.5 4.2 10.6 15.2 49.0 18.6 1.6 0.3

0.9 14.2 8.5 10.7 47.8 15.1 0.3 2.2

1.2 28.2 28.0 11.0 29.7 0.0 1.6 0.3

8.7 42.4 23.1 4.6 18.2 0.1 2.7 0.2

17.3 47.7 27.5 4.0 2.3 0.1 0.5 0.6

22.9 54.6 12.4 8.9 0.6 0.0 0.1 0.5

2.4 60.5 25.4 7.1 4.0 0.0 0.6 0.0

7.4 48.0 30.0 5.6 8.8 0.0 0.1 0.1

1.5 26.2 42.3 7.6 22.2 0.0 0.0 0.2

37.3 15.8 27.9 3.9 10.6 0.2 3.7 0.6

1.2 9.2 65.7 3.0 6.5 0.6 10.8 3.0

Protected area (% of catchment)

7.2

1.4

4.6

32.5

9.3

27.0

62.0

12.9

7.5

12.2

0.6

Water stress (1–3) 1995 2070

1.0 1.0

1.0 1.0

1.0 1.0

2.0 2.0

2.0 2.0

2.9 2.9

1.0 1.0

1.8 1.8

1.0 1.0

2.9 2.9

1.0 1.0

2

3

2

2

3

2

1

3

2

3

2

13 1 0 6 26 842

19 6 0 25 26 842

20 8 0 24 26 150

28 8 4 320 24 595

30 8 6 590 25 692

30 12 4 920 30 391

25 3 0 136 25 028

31 10 1 213 24 974

32 8 0 78 23 834

19 8 1 1257 25 298

15 14 0 34 26 145

Fragmentation (1–3) Number of large dams (>15 m) Native fish species Non-native fish species Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person)

Chapter | 10 British and Irish Rivers

TABLE 10.1 General characterization of the British and Irish Rivers

For data sources and detailed explanation see Chapter 1.

383

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10.2. BIOGEOGRAPHIC SETTING 10.2.1. General Aspects A range of biogeographic provinces result from the British Isles spanning a fairly wide range of latitudes and longitudes (Palmer 1999). More specifically, the range of latitudes extends from continental climatic conditions in the southeast in England to the sub-arctic zone in northern Scotland. In this northerly region, tundra-like conditions at lower altitudes in northern Scotland are characterized by extensive boreal peatlands dominated by Sphagnum spp. At high altitudes, sub-arctic conditions prevail, even though only small areas extend above 1000 m asl (Shaw & Thompson 2006). At intermediate altitudes on more freely draining soils, boreal coniferous forest dominated by Scots Pine (Pinus sylvestris), with Birch (Betula spp.) also being common, is the natural vegetation. Moving south through the lowlands of central Scotland and into northern England and Wales, a milder climate results in broadleaf temperate forest dominated by Oak (Quercus spp.). In the south of England, the broadleaf forest is more diverse with species such as elm (Ulmus spp.), hazel (Corylus avellana), small leaf lime (Tilia cordata), beech (Fagus sylvatica) and ash (Fraxinus excelsior) becoming more common, particularly on more basic soils. The natural forest cover in Ireland would probably have ranged from birch in the western uplands, through mixed forest of oak–ash–hazel in better-drained lowland areas, to alder (Alnus glutinosa) dominant in wetter areas (Cross 1998). Of course given the long human history and high population densities on the two islands, most of the natural vegetation has been cleared, and the UK and Republic of Ireland are now two of the least forested countries in Europe, with only around 10% tree cover (Peterken 1994).

10.2.2. Palaeo-geography The geology of Britain and Ireland, although very complex, exhibits rough northwest/southeast gradient. Igneous and metamorphic formations underlay much of the north and west from the Scottish Highlands through the Irish mountains of Donegal, Connemara and Kerry, the English Lake District and North Wales, whilst sedimentary rocks prevail in the lowlands in the south and east of Britain and the central lowlands of Ireland (Woodcock 1994). The highlands of Scotland and northwest Ireland form part of the Caledonian mountain chain that extends east to Scandinavia. Five-hundred million years ago (MYa), this mountain chain formed part of the ancient continent of Laurentia and was continuous with what are now the Appalachian Mountains in northeast America. Collision with other continental landmasses around this time resulted in a period of major mountain building and metamorphosis that folded the Dalradian sediments that comprise much of the Scottish Highlands (Gordon & Wignall 2006). About 440 MYa, the granite of the Cairngorms was intruded from

PART | I Rivers of Europe

deep within the Earth’s crust. As the north Atlantic began to split around 80 MYa, North America separated from northwest Ireland and Scotland, which then converged with what are now the rest of the British Isles. The rocks which form the uplands of northern and western England mainly comprise a diverse range of sedimentary rocks that have been uplifted in past phases of mountain building. Lower Palaeozoic sediments dominate the southern uplands of Scotland and much of the Welsh mountains. These rocks, mainly mudstones and shales, are associated with the Ordovician (490–443 MYa) Silurian (443– 418 MYa) periods. These uplands tend to be flanked by sedimentary rocks in the lowlands, mainly sandstones, laid down in the Devonian period (418–354 MYa). The main watershed in England is aligned south–north, and is formed by the Pennines, a diverse range of carboniferous (354– 290 MYa) sediments, mainly limestones and gritstones. Rocks from this period also form much of the central plain of Ireland. Younger Triassic rocks (252–199.5 MYa), mainly sandstones, have largely been eroded from upland areas and now mainly dominate the lowlands of northern and central England where they form important aquifers. Sediments from the Jurassic (199.5–142 MYa) dominate a small upland area in the North York Moors in northeast England and then run south though part of the lowlands of eastern England. The youngest Cretaceous (142–65 MYa) rocks are mainly chalk and they dominate the southeast of England. The uplift of these areas dominates the main drainage patterns of Britain, although a long history of subsequent erosion is responsible for sculpting the main lineaments of the landscape. The most recent phases of marked erosion have been in the subsequent glaciations of the Pleistocene (1.8–0.01 MYa) that affected most of the British Isles. As a result, mountains in the north and west are often characterized by steep glaciated valley landscapes and abundant glacial and periglacial sedimentary deposits that affect the character of contemporary river corridors, which have been further influenced by fluvial processes during the Holocene (0.01 MYa). However, the glacial influence also affects lowland terrain, as ice sheets moving from the north have left extensive depositional landforms over much of the islands.

10.3. PHYSIOGRAPHY, CLIMATE AND LAND USE 10.3.1. Landforms and Geology This complex and extremely diverse geological framework of the British Isles underpins much of the variability in the resulting riverine landscapes. Some of the highest mountains in the north of Scotland dominate the headwaters of the rivers Spey and Tay. The river Spey has its source in the Monadliath mountains in the Central Highlands of Scotland, but collects a significant amount of drainage from western tributaries in the Cairngorm mountains that contain the largest area of land in the British Isle above 1000 m asl (Gimingham 2002).

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PHOTO 10.1 The River Tweed is a major salmon river and forms part of the border between England and Scotland (J. Walley).

Both the Cairngorms and Monadliaths have been extensively affected by glaciation, and many of the Spey’s tributaries, such as the Feshie, drain steep mountainous headwaters into glaciated valleys. The Tay drains a complex, montane catchment that also bares a strong imprint of Scotland’s glacial legacy. The Tay itself flows out of Loch Tay, which is fed by the river Dochart, with a catchment in the Central Highlands. Although the Tay discharges into the North Sea on the east coast, its source on the slopes of 1130 m Ben Lui is only around 30 km from the western Atlantic coast. Two other west–east aligned tributaries, the Lyon and Tummel, also form substantial components of the catchment. The river has northerly headwaters, principally the Garry and Tilt, which drain the southern Cairngorm massif and flow into the Tummel before becoming confluent with the Tay. Downstream, the river is joined by the Isla, which also has its source in the southern Cairngorms. The river flows into a large tidal estuary downstream of the city of Perth, entering the North Sea near Dundee, Scotland’s fourth largest city. The largest Scottish river system lying to the south of the highland boundary fault, which separates the most mountainous part of the Scottish land mass from the central lowlands, is the River Tweed (Photo 10.1). It drains a catchment area of around 5000 km2. Historically, the river, flowing west to east in orientation, has been the focus of an important border region, and parts of the river still form the boundary between Scotland and England. The Tweed has its head-

waters in catchments underlain by Lower Palaeozoic mudstones and shales that dominate much of the southern uplands of Scotland. The river flows through the town of Peebles before joining with the Etterick Water, which drains similar headwaters and flows through the town of Selkirk. The Tweed drains an almost circular-shaped catchment and subsequently a number of other important tributaries add to the complex character of the river network. The Gala Water, a north bank tributary that flows through Galashiels, joins before the Teviot, which flows though Hawick and past Jedburgh. The Tweed then flows through Kelso and Coldstream where it is soon joined by the Till, a south bank tributary that mainly drains the Cheviot Hills in England before receiving inflows from the north bank tributary of the Whiteadder. The river discharges into the North Sea through Berwick, the main town on the border between Scotland and England. The River Severn is the longest river (at 354 km) in the UK and drains a large, diverse catchment in England and Wales (Photo 10.2). The Severn has its source at around 700 m asl on Plynlimon in the mountains of Central Wales. The geology of the headwaters is dominated by Ordovician and Silurian sediments that characterize much of the Welsh mountains. Further downstream in the lowland catchment, Permian and Triassic sandstones give rise to more freely draining soils in fertile agricultural regions such as Vale of Evesham in the catchment of the Avon tributary. The river becomes tidal downstream of the town of Gloucester and

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PHOTO 10.2 The source of the River Severn lies in the peatlands of Plymlinon. (D. Jones).

occupies a large estuary before discharging into the Irish sea through the Bristol channel, a long, narrow inlet with the second highest tidal range in the world. The River Wye is a catchment that also has its headwaters on Plynlimon (Photo 10.3). Despite their common source areas, the Wye and Severn diverge and the Wye flows a distance of 256 km through Wales, via the towns of Rhayader and Builth Wells and into England through the towns of Hay-on-Wye, Hereford, Ross-on-Wye and Monmouth before entering the Severn Estuary at Chepstow. Along its course, it is subsequently joined by lowland tributaries such as the Lugg, Frome and Monnow, before the Wye valley itself becomes increasingly incised downstream. Further north, the eastern headwater tributaries of the Mersey, such as the Ethrow and Tame, have their sources at around 600 m asl on the dissected plateau of the Pennine hills and flow off the western scarp slope. The upper catchment is dominated by uplifted gritstones and coal measures of the carboniferous. These rivers then flow in to the lowlands of the Mersey basin that are mainly underlain by Triassic sandstones. The lowlands are drained by tributaries like the Bollin and Weaver, which also have sources in the southern Pennines. The river discharges through the large Mersey estuary on which the city of Liverpool is located, and thence into the Irish Sea. The rivers Ouse and Trent both drain into the estuarine river Humber and on into the North Sea. The two rivers drain some 20% of the land area of England. The resulting mean discharge of 250 m3/s is the largest single input into the North Sea from the UK. As a consequence, the Ouse– Trent system has been extensively studied, particularly its

pollutant load (Jarvie et al. 1997). Both rivers derive much of their flow from tributaries draining the 500– 600 m high plateau of the Pennines. The larger tributaries then flow from these carboniferous headwaters over driftmantled Triassic rocks in their lower courses. The flat low-lying land surrounding the Humber estuary was formed by a glacial lake at the end of the Devensian glaciation and is characterized by lacustrine deposits in the lower reaches of both rivers. The Yorkshire Ouse is the northerly tributary of the Humber and it drains a large part of northern England. In its lower tidal reaches, the Ouse is joined by three major tributaries, the Derwent, the Don and the Aire. The Derwent mainly drains sparsely populated land to the north of the Humber Estuary comprising much of the upland North York Moors and then flows into the low-lying Vale of Pickering. The principal north Pennine tributaries of the Ouse are the Nidd, Ure and Swale, which are confluent upstream of the City of York (Photo 10.4). These tributaries, along with the Wharfe that joins just downstream of York, drain catchments with a strong influence of carboniferous limestone. They flow into the lowland of the Vale of York. Downstream of the Wharfe confluence, the river Derwent enters from the north. This river receives its drainage from the North York Moors, a 400 m high dissected plateau of Jurassic rocks. Although the south bank tributary of the Aire also has its source in the Central Pennines, it drains a heavily industrialized lowland catchment with the cities of Leeds, Bradford and Halifax. Likewise, the Don rises further south in the Pennines, but receives drainage from the city of Sheffield and the town of Rotherham.

Chapter | 10 British and Irish Rivers

387

PHOTO 10.3 The River Wye in its lower reaches (R. Hindle).

Upstream of its confluence with the Ouse, the river Trent is one of the largest river systems in England and has a complex catchment that drains much of the English Midlands. The Trent rises in the southern Pennines on Biddulph Moor near Stoke in the west, and its course flows some 280 km east through the urban centres of Burton, Nottingham Newark and Gainsborough, before entering the Humber Estuary. The main tributaries of the Trent drain a catchment

of great contrasts that include predominantly rural headwaters such as the Rivers Dove and Derwent in the Peninnes, which are again underlain by carboniferous geology comprising limestone in the south and millstone grit, a siliceous sandstone, in the upper Derwent. Other major tributaries include the highly urbanised Tame catchment in which Birmingham, the second largest city in the UK, is located, and the Soar, a large east bank tributary that drains a catchment PHOTO 10.4 The River Ure, a Pennine tributary of the Ouse at Aysgarth Falls (M. Knapton).

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PHOTO 10.5 The tidal limit of the River Thames at Teddington Lock in western London (Anonymous).

that includes the city of Leicester. These southeast headwaters are characterized by gently undulating catchments (ca. 100–200 m asl) composed of glacial tills covered by loamy clay soils that impede drainage. Downstream of Nottingham, the catchment is underlain by Sherwood sandstone, a major UK aquifer. The Thames is one of the England’s largest rivers and occupies an iconic status in the national psyche where it flows through the centre of London. The river has its source some 150 km to the west in Gloucestershire and, including its extensive tidal estuary, drains an area of around 13 000 km2 (Photo 10.5). The catchment is low-lying, with the western headwaters in the Cotswold Hills at just over 300 m asl. These hills, which are mainly composed of Jurassic sediments, source the upper Thames and other major tributaries such as the Windrush and Cherwell (which flows through Oxford). Other low-lying hills like the Malborough Downs in the southwest, are the main headwaters for other tributaries such as the Kennet and Lambourn. Headwaters in the Chilterns to the north feed tributaries such as the Ver and Lea. Whilst the Wey drains part of the northern slopes of the South Downs. Geologically, the Thames basin is underlain by Cretaceous geology with extensive areas of chalk outcropping that dominate the landscape. The Frome and Piddle rise on the North Dorest Downs in southern England and drain west to Poole Harbour, prior to entering the English Channel (Photo 10.6). The catchments are mostly rural in character, with the only large urban centre being the town of Dorchester (population: 15 000) on the Frome. The Frome drains an area of around 400 km2, whilst the Piddle catchment is under half this size. The maximum altitudes in the headwaters are 266 m asl for the Frome and

PHOTO 10.6 The River Frome characteristic of the chalk streams of southern England (Natural England).

Chapter | 10 British and Irish Rivers

389

PHOTO 10.7 The wide, low gradient River Shannon at the ancient monastic site of Clonmacnoise (Anonymous).

275 m asl for the Piddle. Both catchments have similar chalk-dominated geology and are mainly characterized by agricultural land use. Both rivers have been the focus of a long history of scientific research as a result of the establishment by the Freshwater Biological Association of its ‘River Laboratory’ on the banks of the Frome upstream of Wareham. This has resulted in the Frome being one of the freshwater sites in the UK Environmental Change Network (www.ecn.ac.uk). More recently, together with the Piddle, which has had a history of research associated with water quality issues and water abstraction, it has been one of four catchments investigated as part of the government funded LOCAR (Lowland Catchment Research Project) study. The pairing of the Frome and Piddle offer invaluable insight into the nature of lowland chalk rivers in the UK, which have unique hydrochemical and ecological characteristics, but are subject to a wide range of pressures. The River Shannon is the longest river system in the British Isles (Photo 10.7). With a catchment area greater than 16 000 km2, it drains significant proportion of the Republic of Ireland and is over 328 km long. It mainly rises in the Cuilcagh Mountains in the south of County Fermanagh and flows through 11 of Ireland’s 32 counties. It flows though the large lakes of Lough Allen, Lough Rea and Lough Derg. Its principal tributaries are the Such and Brosna. The Shannon drains much of the central plain of Ireland, where carboniferous limestone is overlain by glacial deposits of varying texture and depth. The region has extensive peat bogs.

10.3.2. Climate The climate of the British Isles is dominated by maritime air masses from the Atlantic that can have a polar influence, particularly during winter, or a sub-tropical influence, most

commonly in the summer (Ward 1981). As the area stretches some 1150 km from north to south, and 660 km from west to east, the islands experience a range of climatic conditions. This results in marked gradients in hydroclimatic factors that drive the hydrological and thermal regimes of rivers (Cook 1998; Harris et al. 2000). The location of mountainous or upland areas along the Atlantic seaboard of the British Isles exerts an orographic influence that creates a rain shadow effect and further exacerbates west–east precipitation gradients. Mean annual precipitation in the mountains of the northwest exceeds 1500 mm, but falls below 500 mm in the southeast (Marsh et al. 2000). Mean annual air temperatures are <10 C over extensive parts of the Scottish Highlands, but >15 C in southeast England. This is reflected in actual evaporation rates that range from 550 mm in the southeast, but are typically closer to 400 mm over the much of the landscape and fall below 350 mm in the cooler highlands of Scotland. This general pattern of climatic diversity is manifest in very different hydroclimatological regimes for the rivers considered. In the north, the mountainous headwaters of the Spey and Tay have annual precipitation exceeding 2000 mm, with a significant proportion (up to 30%) falling as snow (Soulsby et al. 1997a). The more westerly headwaters of the Tay receive more precipitation than the Spey, although the lower catchments receive much less, 700 mm at Spey Bay and in the Tay estuary, giving catchment averages of around 1200 and 1600 mm, respectively. The more southerly and easterly location of the Tweed means that the climate is warmer and drier than the Spey and Tay. Here rainfall ranges from around 1800 mm in the southern upland headwaters to 650 mm near Berwick, with a catchment average of 961 mm. The westerly upland headwaters of the Severn and Wye receive an average annual precipitation of around 2400 mm

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in the Cambrian mountains of central Wales, but the lower catchments receive only 700 mm. Of the rivers considered in this chapter, the Mersey is distinguished by flowing west, having headwaters in the Pennines in the east of the catchment, with the orographic influence resulting in over 1100 mm of average annual precipitation. This contrasts with the 840 mm in Liverpool to the west. In the Ouse catchment, the Pennine headwaters receive an annual average precipitation of 1200–1300 mm, falling to 630 mm in the Vale of York. The northerly tributaries in the North York Moors receive 900 mm. The headwaters of the Trent have annual rainfall varying from >1300 to <600 mm near Newark, and the catchment average rainfall is 746 mm. The large catchment of the Thames encompasses one of the driest parts of Britain with a catchment average rainfall of 700 mm. Rainfall is highest in the Cotswold headwaters at 800 mm, although high transpiration rates limit groundwater recharge and result in summer soil moisture deficits over much of the catchment (Finch & Harding 1998). The westerly location of the Frome results in higher annual rainfall at 950 mm. Further west, the Shannon receives around 1000 mm of precipitation, although totals are higher in the northwest headwaters (Mills 2001). Around 450 mm of this moisture is lost as evapotranspiration. Winters in Ireland are mild, with mean January temperatures up to 6.5 C and July temperatures around 14 C (Cross 1998). Strong winds are a characteristic feature of the climate and there is a high incidence of cloudiness (Collins & Cummins 1996).

10.3.3. Land Use Patterns Geology and climate play a major role in setting the physical template for soil development and landscape capability. Land use characteristics vary dramatically in the British Isles. Despite the high population densities in urbanised parts of the lowlands (88% of the population is in urban centres), some of the lowest population densities in Europe are found in the mountainous fringes of Scotland and Ireland. However, this has not prevented rivers from being radically altered (Sear et al. 2000). The influence of human activity on land use is widespread and longstanding and has a major influence on hydrological processes. Precipitation, evaporation, soil water flow paths and groundwater recharge are all affected by land use change with concomitant implications for river system functioning (Newson 1997). The UK and Ireland both have a long history of deforestation of native woodlands, with >90% of the land being cleared in both countries. In the past 100 years, concerted efforts have been made to reforest large tracts of land, particularly in the cheaper, wetter areas of the mountainous northwest. The focus has been on planting exotic coniferous species, particularly fast growing species from the Pacific Northwest of America (Newson 1997). Favoured species include Sitka spruce (Picea sitchensis), which is now the most widespread tree species in the UK, mainly planted in

PART | I Rivers of Europe

large monocultures that are harvested on a 40–60 year rotation. The development of large new areas of forestry in the uplands has had a major effect on some rivers in terms of greater water use (via evapotranspiration) by tree cover and water quality impacts ranging from increased suspended sediment supply, temperature moderation, and eutrophication to enhanced acidification (Robinson et al. 2000). Forest clearance means that agriculture is now the dominant land use, covering 70% of the UK land area (Robinson et al. 2000). Agriculture affects rivers in many ways. In terms of water quantity, it is estimated that around 10% of the landscape is artificially drained. Naturally waterlogged soils in low-lying areas have been extensively drained for centuries to bring land under cultivation. The process accelerated in the post-war years and in the 1970s, and government grants covering 50% of the drainage costs resulted in rates of land drainage reaching 1000 km2/year. The process usually involved under-drainage of soils, together with canalization of stream channels; that is, the deepening, widening and straightening rivers to lower water tables and evacuate runoff more rapidly (Sear et al. 2000). Around 1% of the agricultural land in the UK, particularly in the drier and warmer southeast, is irrigated either from borehole pumping or direct river abstraction. As well as affecting the physical characteristics of rivers, agriculture has had a profound effect on catchment biogeochemical processes and stream water quality. Most obvious has been nutrient enrichment through fertilizers of N and P. Through technological developments and subsidies from the EC Common Agricultural Policy, fertilizer application rates of N, for example, increased from 50 000 t/year in 1928 to over 1.3 106 t/year in the 1980s (Moss 1998). Over 450 pesticides have been approved for use and 120 are commonly applied to agricultural lands, although application rates are decreasing from the 30 000 t/year in the 1970s and 80s (Robinson et al. 2000). Similar trends are evident in Ireland, although being less marked due to the lower agricultural capability of most soils. Urbanised areas cover 10% of the land surface of the UK, although this is expected to increase to 12% by 2016. Up to 5 million new homes are thought to be needed, mainly focused in the southeast as the UK economy is increasingly aligned to that of continental Europe. Obviously such planned urban growth has implications for water supplies, effluent production and urban runoff generation, and has potential to exacerbate longstanding urban influences on the physical, chemical and biological characteristics of rivers (Chin 2006). Again, although less marked in Ireland, expansion of urban areas has occurred over the past 10 years due to the economic success of the Irish economy since joining the EU. This has led to expansions of towns and cities, and increased second home ownership in the rural west of the country such as towns like Athlone and Limerick. The patterns of geology and climate described in previous sections dictate that land use characteristics and population densities in the different catchments considered in this chapter exhibit extreme contrasts. In the Spey and Tay

Chapter | 10 British and Irish Rivers

catchments, extensively managed mountains and moorlands that form the stereotypic view of Scotland are exploited by the tourist industry and form an important component of the Scottish economy. Population densities are low and often conservation designations, such as the Cairngorms National Park, protect large tracts of land. The Spey drains a relatively sparsely populated area; around 20,000 people live in the catchment, mainly in small towns with populations of <3000 individuals. Such mountain areas are characterized by subarctic vegetation, whilst lower lying hills are dominated by heather (Calluna) moorlands that are managed for grouse (Lagopus lagopus) and red deer (Cervus elaphus). On steeper hillslopes at intermediate altitudes are remnants of the native boreal forest cover, with some of the largest tracts of semi-natural woodlands in the British Isles such as the Scots pine dominated forests in the Spey catchment. Some commercial plantations of non-native species also occur, particularly in parts of the Tay catchment. Whilst in the lower Spey and Tay valleys, the milder climatic conditions and better soils support arable land. These landscapes, particularly in the Spey, are drained by rivers that have a high degree of naturalness. These support Atlantic salmon (Salmo salar) that is important both for conservation and as an economically important sports fishery. The Tay catchment is also significant for its salmon fishery, although hydropower production affects most of the river with natural lochs (or lakes) and artificial lochs being regulated for hydroelectricity (Gilvear 1994). The milder climate and lower altitude of much of the Tweed results in a catchment that is dominated by agricultural land use; 18% of the area is arable farming, 63% rough grazing and 17% forestry (Tweed Forum 2003). The hills are lower than in the northern Highlands and much more of the catchment is characterized by gentler slopes and land with much greater agricultural capability. Consequently, the Tweed is much more intensively farmed than the Spey or the Tay, although the river is still an important salmon fishery. The hills around the catchment were predominantly used for sheep grazing and wool became an important local produce. The energy of the Tweed system was used to support a large number of woollen mills in the main towns present on each tributary. Over 100 000 people currently live in the catchment, and the main towns have populations of around 5000–20 000. In the upland headwaters of the river Severn, land use is predominantly sheep grazing and commercial forestry. As the Severn flows east through Wales, it occupies an increasingly substantial floodplain that is grazed for beef production in the English counties of Shropshire, Worcestershire and Gloucestershire. In the middle reaches of the river, lowland sub-catchments drain some of the UK’s largest dairy farms. Downstream of the town of Shrewsbury, it is joined by the river Tern, a lowland northerly tributary, before flowing through Coalbrookdale. In the 18th century it was one of the first modern industrial sites in the world, being the location of the on of the first coke-based blast furnaces heralding

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modern methods for steel production. Inflows from the river Stour, a northern tributary, brings in drainage from parts of the so-called ‘Black Country’, another historic industrial heartland in the west Midlands where metal processing industries were concentrated. The river receives drainage from the agricultural catchment of the river Avon, downstream of Worcester where the lower catchment has an increasing proportion of arable land. After passing Gloucester, the river discharges into the sea via the Bristol Channel. Like the Severn, the headwaters of the Wye itself are forested, but there is also sheep grazing on open moorlands. The catchment remains similar to the Severn and is predominantly agricultural in character (57% of the catchment is grazed, with 17.5% arable) with only 4% urban and limited industrial development. Much of the Mersey catchment drains the densely populated, industrialized lowlands of northwest England. The cities of Liverpool and Manchester are within the catchment as well as the large industrial towns of Bolton, Macclesfield, Warrington and St. Helens, resulting in >34% of the catchment being urbanised. In total, >5 million people live in the catchment. For almost 300 years, Liverpool has been one of the most important sea ports in Britain. This underpinned the expansion of the area as one of the major centres for rapid population growth and heavy industry in Europe during the industrial revolution. The fast-flowing headwater streams of the Pennines provided the location for a large textile industry that harnessed their power in mills to drive mechanised looms. Chemical industries associated with textiles also expanded; such as bleach, dyes, finishing trades. This provided further impetus to the local development of heavy chemical industries, paper mills and glass production. With 5 million people living in the catchment, sewage inputs to the Mersey system have been enormous and heavy industry has used the watercourses as a means of effluent disposal; the Mersey has an unenviable legacy of pollution. The large, complex catchment of the Yorkshire Ouse has marked contrasts in land use. The Derwent mainly drains sparsely populated land to the north that incorporates the extensive heather (Calluna sp. and Erica sp.) moorlanddominated uplands of the North York Moors (a National Park) that are grazed by sheep, and low-lying fertile arable lands of the Vale of Pickering. The main tributaries of the Ouse – the Wharfe, Nidd, Ure and Swale – also drain upland moors on the eastern side of the Pennines where sheep grazing is the dominant lands use. The landscape is conservationally important and lies within the Yorkshire Dales National Park. As these rivers flow into the lowlands of the Vale of York, land use becomes increasingly characterized by arable and mixed farming in the more fertile lower floodplains. The south tributary of the Aire has its source in the Pennines, but it drains a heavily industrialized catchment that includes the towns and cities of Leeds, Bradford and Halifax. As with the towns on the Mersey tributaries, these

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urban centres often developed rapidly on the basis of the textile industries that used mills utilizing the power of Peninne streams. The southerly tributary, the Don, rises in the Pennines, but receives drainage from the city of Sheffield and the town of Rotherham where a major steel industry developed historically as a result of the availability of coal from the Yorkshire and East Midlands coalfields. Historically, headwater tributaries in the Pennines had local mining industries for lead and zinc. Land use patterns in the Trent have a number of distinct features. Like the Ouse, the Pennine headwaters are dominated by rough grazing on moorlands that partly lie within the Peak District National Park. Over 6 million people live in the catchment, mainly in large urban centres. Many of these, such as Birmingham, Stoke on Trent and Leicester, lie at the headwaters of the rivers and the urban environment and its associated industry has major implications for the quantity and quality of water downstream. Many of the urban areas have, or historically had, a wide range of industrial activities: Birmingham and the surrounding ‘Black Country’ have been important for vehicle manufacturing, heavy engineering and metal finishing, Stoke on Trent has long been a major centre for the pottery industry, Burton on Trent is an important centre for the brewery industry, whilst towns like Leicester specialise in textiles. The carboniferous geology of the catchment resulted in historical coal production in Nottinghamshire and South Yorkshire, which in turn supported a large steel industry, although both of these traditional industries are now largely in decline. A further distinct feature is that the Trent valley has the UK’s largest concentration of fossil-fuel based power stations, largely due to the proximity of coalfields and availability of cooling waters in the Trent itself. The catchment also has a rural character, and the lowlands are an important agricultural region. Intensive mixed farming occurs in the hinterlands of markets in the main urban centres of Birmingham, Nottingham and Leicester and dairying is important in the Staffordshire and Derbyshire areas to the west. The fertile alluvium of the Vale of Trent has been extensively drained and is intensively farmed for arable production of wheat, potatoes and sugar beet. Within the Thames catchment, extensive urban areas are surrounded by high quality agricultural land that is mainly used for arable farming. A total length of 5330 km of managed river forms much of the drainage network, and extensive, fertile floodplains cover almost 900 km2. A remarkable feature of the Thames basin is the population density in the area around London and the focus of economic activity in this area. The catchment covers just 10% of the land surface area of England and Wales, yet it contains 25% of the total population and is the location of economic activity that generates 25% of the Gross National Product. As a result of this current activity and its long history, London having been the national capital of England for 1000 years, the Thames is a highly impacted catchment in almost every way. In the Frome catchment, land cover is dominated by permanent grassland with dairy or stock rearing with some

PART | I Rivers of Europe

cereal cropping. The upper parts of the catchment in the North Dorset Downs drain a landscape of high amenity and ecological value, and comprise part of the Dorset Area of Outstanding Natural Beauty – a nationally designated area for landscape protection and conservation. Land use in the Shannon catchment is dominated by mixed farming that covers much of central Ireland (McGovern et al. 2002). This comprises generally low input grazing that is suited to the predominantly poorly drained gley soils. This has, however, seen intensification since Ireland’s accession to the EU. Such intensification has also been aided by a long history of arterial drainage in the Shannon catchment, which being so flat and low-lying is notoriously prone to waterlogging and flooding (Bhattarai & O’Connor 2004). Extensive basin peatlands occupy the catchment, although these have been affected by cutting for domestic and commercial use with several of the largest peatbogs being used for electricity generation (Cross 1998). Despite these land use changes, the Shannon still has a floodplain dominated by species rich fen grassland with species such as Agrostis canina and Carex spp., which is largely unfertilized and only managed by an annual mowing regime for hay making (Spink et al. 1998).

10.4. GEOMORPHOLOGY, HYDROLOGY AND BIOGEOCHEMISTRY 10.4.1. Geomorphology Differences in geology, hydroclimate and human management result in great contrasts in the geomorphology of the rivers of the British Isles (Gregory 1997). In the Scottish rivers, the Spey and Tay, steep mountainous headwaters, flashy hydrological regimes and the abundance of glacial and periglacial sediments in valley landscapes give the rivers high levels of energy and a variety of alluvial channel types (Werritty & McEwan 1997). In contrast, rivers like the Thames and Trent have low gradients, more subdued hydrological regimes and more heavily managed channel networks (Gregory 1997). Gurnell & Petts (2000) show that only 19% of the main rivers in the UK have anything approaching natural hydrological and geomorphological flow regimes – in Scotland the figure is 35%. The range of impacts varies from reservoir regulation (26%), flow augmentation from groundwater or interbasin transfers (16%), abstractions (63%) to nutrient augmentation from sewage (33%). Of the rivers covered in this chapter, the Tay, Tweed, Mersey, Severn, Wye, Ouse, Trent and Thames are amongst the major regulated rivers in the UK. More generally, channel management schemes – for purposes such as flood protection, land drainage and erosion control – have resulted in substantial modification to 52% of lowland channels and 35% of upland main river channels (Sear et al. 2000). Despite this, the relatively small scale of British rivers means that marked topographic gradients result in rapid transitions from upland to lowland areas and a wide range of channel

Chapter | 10 British and Irish Rivers

types. The Devonian glaciation of the British Isles infers that river channels have re-established themselves relatively recently (over the past 12 000 years) in valleys that generally reflect pre-glacial landscapes. These contain a rich array of glacial and periglacial deposits that influence contemporary fluvial processes. Consequently, there has been a great deal of interest in the fluvial geomorphology of the rivers of the British Isles and many rivers have sites of geomorphic interest, whilst some offer excellent opportunities for understanding the inter-relationships between river channels, fluvial processes and landscape evolution. The Spey is of particular interest in terms of its geomorphological functioning as a British river where high levels of energy are present in a channel with relatively natural conditions. It contains areas of active braiding – a rare state for British rivers – particularly on the Feshie tributary (Werritty & McEwan 1997) and in the tidal estuary at Spey Bay (Riddell & Fuller 1995; Werritty & McEwan 1997). The Feshie braids have some of the most rapid rates of channel migration recorded in the UK, reflecting the high energy state of the river (Werritty & Leys 2001). However, the natural geomorphic processes in some parts of the Spey have been affected by management. Recent work by Gilvear (2004) has shown the impact of Spey Dam on the effectiveness of geomorphic processes over a 60-year-period, with the reduction of flood flows causing sedimentation in the channel and reducing channel width. Much less dramatic, but possibly more significant in terms of cumulative impacts, are the plethora of informal engineering works that are used for bank protection and fishing improvements, particularly along the main stem of the river (Leys 2001; Pretty et al. 2003). Despite being a highly regulated river for hydropower production, the headwaters of the River Tay have some extensively studied sites for fluvial geomorphology. Processes of meander formation and bedload transport have been extensively investigated in the Allt Dubhaig, a headwater tributary of the river Garry (Hoey & Ferguson 1994). Moir et al. (2004) examined the distribution of channel types in the Allt a’ Gleann Bheag in relation to wider catchment controls in the upper reaches of the River Isla. Werritty and McEwan (1997) have described the influence of base level controls on knick-point migration of bedrock-lined channels at the Falls of Dochart on the River Dochart where it flows into the Loch Tay. In the main stem of the river, Gilvear and Winterbottom (1992) showed how regulation has led to reduced complexity of river channels and highlighted how historic management for flood protection has affected contemporary fluvial processes and how major floods caused channel avulsions (Gilvear & Harrison 1992). Like the Spey, the Tay and the Tweed are both important salmon fisheries and have been subject to a plethora of channel modifications for fishing improvements that have cumulative impacts on natural channel processes. The Severn and Wye are important examples of rivers, from headwaters to estuary that contain sediments providing

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invaluable insight into the processes and timescales of river basin evolution (Higgs 1997; Lewin 1997). For example, the headwaters of the Elan tributary of the Wye provide excellent examples of natural Welsh mountain streams and their associated geomorphological features upstream of Craig Goch reservoir. In contrast, the Severn between Dolwen and Penstrowed has long meandering sections that represent one of the best-preserved piedmont river floodplains in the UK (Higgs 1997). A further meandering section of the river at Welshpool, more lowland in character, has been extensively studied; as has the Lugg, a meandering tributary of the Wye. In the lower Severn, a stretch of the river at Preston Mountford allows the rivers contemporary processes to be assessed in relation to longer scale Quaternary evolution, whilst in the lower Wye, a series of bedrock incised meanders provide insight to the rivers response to base level change in the Severn estuary (Gregory 1997). Given this template, many process-based investigations of fluvial geomorphology have been carried out in the Severn. Bull (1997) looked at the relationships between flood peaks and the movement of fine sediment waves down the river. Walling and Quine (1993) used Cs-137 from fallout from the Chernobyl explosion to examine the fate of such fine sediment pulses, concluding that 23% was retained by floodplain storage and 2% in bars within the river channel. Steiger et al. (2001) examined in-channel storage in terms of depositional features that add habitat diversity. Other workers such as Wilkinson et al. (2004) examined the hydraulics of water flowing in meandering sections of the Severn to understand the processes sustaining pool riffle sequences. More modified rivers are less instructive in terms of basin-scale perspectives on landscape evolution and fluvial geomorphology. Although even in the heavily modified Mersey catchment, Danes Brook and the river Bollin offer some interesting examples of channel migration and flood plain evolution in lowland rivers (Harvey 1997). In the Ouse–Trent system, Pennine headwaters like the Swale have been investigated to show how steep boulder/cobble bed channels respond to high magnitude low frequency flooding (Macklin 1997). Other reaches, like Ayesgarth Falls, provide good examples of knick-point migrations in bedrock-lined channels. Walling et al. (1998) examined the processes of floodplain construction by assessing sediment accretion rates in the lower Ouse. In the Pennine headwaters of the Trent, the river Derwent near Hathersage was an early site where the impacts of river regulation on channel response were investigated (Petts 1984). Further upstream, the erosion of peats and evolution of drainage networks in upland peat bogs have been examined (Tallis 1973). Although now a low energy, lowland river, palaeo-environmental evidence indicates that the lower Trent was a dynamic braided system some 12 000 years ago (Greenwood et al. 2003). Examination of relatively recent maps and air photos by Large and Petts (1996) show that the Trent was still dynamic prior to extensive channel management in the 20th century. More recently, Knighton (1999)

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adopted a catchment scale approach to assess stream power variations within the Trent. Such work may provide a guide for future, more sustainable approaches for appropriate geomorphology based river channel management. Although the Thames has been extensively modified, it is an important river from the perspective of longer-term river basin evolution (Gibbard & Lewin 2003). Regarding the contemporary river system, Downs (1994) carried out a geomorphological characterization of parts of the Thames catchment and assessed the relative importance of extensive natural controls and more localised human influences in regulating channel processes and adjustment to management. He concluded that few channels are capable of recovering their sinuosity after channel management, thus highlighting the importance of existing meandering channels and the need for restoration of previously straightened reaches. Low gradient channels overlying chalk or clay tend to be depositional in nature and thus may require regular maintenance. Channelised reaches with higher gradients show evidence of erosive enlargement of the cross-section, which indicates such management is not sustainable. The Frome–Piddle system, although small in scale, gives some good examples of different channel types in a less disturbed chalk catchment (Ladle & Westlake 2005). The geomorphology of the Shannon is highly distinctive. The upland maritime rim of the basin, and flat carboniferous interior of the central catchment, results in very low channel gradients (Bhattarai & O’Connor 2004). For example, in the 205 km reach between Loch Allen and Loch Derg, the river falls by just 12 m. The large network of lakes within the basin form important connections between the channels themselves. The resulting problems of water-logged land and flood risk dictate a long history of arterial drainage and channelisation that radically altered channel characteristics. The first phase of this commenced immediately following the Great Famine in 1845–1846. More systematic works followed the Arterial Drainage Act in 1945 that resulted in widespread straightening, deepening, widening, embankment construction and lake storage development. The aggressive approach to channel management was advocated by US Army Corps of Engineers (Rydell 1956). Consequently, most of the river is navigable, and water-based recreation using boats is an important economic use of the river. This has, however, come at the expense of greatly reduced habitat diversity.

10.4.2. Hydrological Regime The hydrological and thermal regimes of rivers in the British Isles reflect the hydroclimatic variability that the islands experience, together with differences in catchment geology and geomorphology (Figure 10.2 and Table 10.2). With mountainous headwaters, high precipitation and snowmelt on upland soils such as gleys, peats and shallow rankers, the Spey has a responsive hydrological regime (Goody 1988). Mean monthly flows often show a marked spring peak in

PART | I Rivers of Europe

FIGURE 10.2 Runoff in the British Isles (after Ward 1981).

discharge, reflecting the influence of snowmelt, and daily flow hydrographs exhibit diurnal variation (Ferguson 1984). The Cairngorm headwaters are prone to high-magnitude, low frequency floods in response to snowmelt or rainfall (McEwan & Werritty 1988). Groundwater in alluvium and various periglacial and fluvioglacial drifts in headwater areas sustains appreciable summer baseflows, which may also be influenced by high precipitation (Soulsby et al. 1998). The Feshie tributary of the Spey has been one of four larger catchments in the UK NERC-funded Catchment Hydrology and Sustainable Management (CHASM) project that sought to explain the hydrological behaviour of a larger mesoscale catchment (Soulsby et al. 2006a). This built upon earlier work in the Allt a’ Mharcaidh, a 10 km2 tributary of the Feshie, which is a part of the UK Acid Waters Monitoring Network and the UK Environmental Change Network (Soulsby et al. 2000). The Feshie work used isotopic tracers to show the importance of catchment characteristics, particularly soil hydrological properties, in determining the hydrological functioning of the catchment (Rodgers et al. 2004). Sub-catchments dominated by responsive peaty soils (histosols) or skeletal montane soils (leptosols) have low groundwater contributions (<40%) and short residence times (<0.3 years). Sub-catchments with a high coverage

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TABLE 10.2 Hydrological characteristics of the British catchments at the most downstream gauging site

River

Station

Period

Catchment area (km2)

Spey Tweed Ouse Trent Thames Tay Frome Severn Wye Mersey

Boat o Brig Norham Skelton North Muskham Kingston Ballathie East Stoke Total Haw Bridge Redbrook Westy

1952–2004 1962–2005 1969–2004 1968–2004 1883–2005 1952–2005 1965–2004 1971–2004 1936–2005 1986–2003

2861.2 4390.0 3315.0 8231.0 9948.0 4587.1 414.4 9895.0 4010.0 2030.0

of freely draining soils – such as humus iron and alpine podzols, and alluvial soils (fluvisols) – were characterized by high groundwater (>40%) contributions and longer mean residence times (1 year) (Soulsby et al. 2006b). The steep, responsive nature of many sub-catchments results in an active flood regime along the Spey. Although the properties and infrastructure threatened by flooding are concentrated in the Aviemore area, extensive flooding of agricultural land has also occurred (Marsh et al. 2000). Flood generation in the upper catchment of the Spey is moderated by a regulated hydrological regime for hydropower production, which results in a major interbasin water transfer south to the rivers Tay and Laggan (Gilvear 2004). In addition, natural flood attenuation in the Insh Marshes forms one of the best examples of a floodplain fen that has extensive storage capacity to moderate flood peaks (Grieve et al.

Mean flow (m3/s)

Q95 (m3/s)

Q10 (m3/s)

Average annual rainfall (mm) (1961–1990)

65.4 78.9 50.1 28.3 65.5 167.9 6.4 106.2 73.9 37.3

19.0 14.2 7.5 183.4 7.8 42.8 2.2 19.6 11.4 7.7

123.6 169.5 124.9 747 161.0 333.3 12.3 254.6 174.0 82.4

1120 955 900 747 706 1425 968 792 1011 1076

1995), whilst overbank flow on the braided sections of the River Feshie at Feshie Lodge (Rodgers et al. 2004) and the Feshie alluvial fan at the Spey confluence (Gilvear et al. 2000) have similar floodplain storage in riparian zones with a high degree of naturalness (Photo 10.8). This flood attenuation role of many Scottish floodplains has given attention on trying to integrate them in flood management plans (Werritty 2006). Water demand in the Spey catchment is generally much lower than available resources. Supply is focused on two major abstractions, Loch Einich that meets the needs of Aviemore, the main tourist centre, which has seasonally high demands as a result of visitor influx. In the lower river, the Spey Abstraction Scheme, the largest groundwater abstraction scheme in Scotland, comprises a series of 36 groundwater wells in the alluvial floodplain of the Spey and PHOTO 10.8 The River Feshie a major tributary of the River Spey rises in the Cairngorm mountains (D. Tetzlaff).

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supplies settlements in the lower catchment and adjacent coastal areas (Chen et al. 1997). The wells are generally 50–100 m from the river, and mainly pump river water through the alluvial aquifer where the colour and metals content (Fe and Mn) is significantly reduced. Whisky distilleries are also significant water consumers, many being associated with an iconic stream or spring used in marketing the product (Cribb & Cribb 1998). The river Tay is the largest river in Scotland, and, in terms of discharge, the largest river in Britain. It is also the most intensely regulated river for hydropower production (Gilvear 1994). Naturally, the Tay would have an extremely responsive hydrological regime as its catchment is characterized by mountainous terrain with low permeability igneous and metamorphic geology and shallow, low permeability soils (Black & Hardie 2000). Although the northern Cairngorm tributaries have a snow-melt influenced hydrological regime, it is less marked than the Spey. This is because the western tributaries drain the climatically milder Central Highlands (Johnson & Thompson 2002). However, the highly regulated nature of the river means that many tributaries and the main river itself have highly artificial regimes, and compounded by a series of interbasin transfers on many tributaries that support the hydropower schemes within the catchment (Gilvear 1994). For example, Jackson et al. (2007) show the degree of flow regime alteration that can occur with reference to the River Lyon (Photo 10.9), where a sequence of two hydrodams on the river has very different operating strategies. At Lubreoch dam, hydro-generation is continuous for much of the year. Downstream at Stronuich reservoir, water is transferred south to support hydro-schemes in the Lochay system. Consequently, only compensation releases occur downstream and the river needs 10 km, and inflow from a

PART | I Rivers of Europe

number of large unregulated tributaries, before a more natural flow regime is re-established. More serious problems occur in other parts of the Tay catchment, most notably in the River Garry which supports an interbasin river transfer and often receives little compensation water (Gilvear 1994). However, the specific impacts depend on the operating rules for individual reservoirs, and how hydropower schemes are managed as a group to meet operating demands and water conservation measures during summer low flows. An interesting aspect of the baseflow regime of the Tay is the use of freshet releases to encourage fish migration during summer and autumn. This is evident in the compensation releases on the river Lyon below Stronuich reservoir (Jackson et al. 2007). The overall impact of individual dams is damped for the Tay system, as regulated and unregulated systems produce an integrated hydrological response. Despite the regulated nature of the flow regime, the Tay has had historic flood problems and, in recent years, experienced some of the worst flooding in Scotland (Marsh et al. 2000). Problems have been most marked in the city of Perth in 1990 and 1993, and this has resulted in investment in an upgraded flood warning system and a major flood defence scheme (Falconer & Anderson 1993). It also prompted examination of how historic management and channelisation of the river, with a concomitant loss of floodplain storage, may have worsened downstream flood levels (Gilvear & Winterbottom 1992). As the best agricultural land is generally found on the floodplain of the Tay and its major tributaries, flood embankments have been built by individual land owners in an attempt to protect crop lands. Many such barriers have been poorly constructed and maintained and are prone to over-topping and failure (Gilvear & Black 1999). Examination of the flooding issue on the Tay has helped PHOTO 10.9 The River Lyon is a tributary of the River Tay draining the central highlands of Scotland. Like many parts of the Tay, the river is heavily regulated for hydropower (C. Gibbins).

Chapter | 10 British and Irish Rivers

identify some important aspects of the hydrology of Scottish rivers. For example, it is evident that precipitation levels in the western and central parts of Scotland have increased dramatically over the past few decades (Werrity 2002). Moreover, it has become apparent that floods tend to cluster in ‘flood rich’ and ‘flood poor’ periods, with the 1990 and 1993 Perth events falling into one of these ‘flood rich’ periods (Black & Hardie 2000; MacDonald et al. 2006). With a large and diverse catchment, the Tweed has a complex and varied hydrology. Precipitation is highest in the headwaters in the southern uplands, although the circular configuration of the catchment means that convergence of flows can have similar flood response times that lead to substantial floods. The lower altitude and more southerly location means that the influence of snow has a minor effect on catchment water balance and lower areas are not so responsive to floods. The catchment has high annual evaporation rates, ranging from 400 mm in the headwaters to 450 mm in the lower parts, so larger soil moisture deficits can occur. The catchment has experienced some extreme floods, both on the main stem of the river and on tributaries, with some 9% of the catchment being at risk of flooding, with the potential to affect 4500 properties (Tweed Forum 2003). The hills in the catchment headwaters are underlain by low permeability slates and shales, covered by responsive peaty soils that facilitate rapid translation of precipitation inputs into the river (Abesser et al. 2006). The headwaters are the home for 13 water supply reservoirs, which serve communities along the Tweed. Some were originally constructed to supply the woollen mills that were important in the main towns along the river. Recent large reservoirs augment the water supply to the city of Edinburgh (Jowitt & Hay-Smith 2002). In the east of the catchment, the geology changes to more permeable Old Red sandstone and carboniferous limestones for significant aquifers, and borehole supplies are important for crop irrigation in the lower catchment. Precipitation in the headwaters of the Severn is >2000 mm on the highest mountains, falling to 800 mm in the lowlands to the east. The geology is highly variable; in the headwaters Lower Palaeozoic mudstones and shales predominate and are mantled by peats and peaty podzolic and gleyed soils. Further downstream in the lowlands, Permian and Triassic sandstones give rise to more freely draining soils. The headwaters of the rivers Severn and Wye (see below) rise on the eastern slopes of Plynlimon and have been the focus of the most intensive hydrological studies in the UK. The former Institute of Hydrology established the Plynlimon experimental catchments in the 1960s to investigate the influence of forestry on the water balance of upland streams and rivers (Kirby et al. 1991). Intensive monitoring to determine catchment water balances demonstrated that the afforested Severn catchment ‘used’ more water than the neighbouring Wye mainly due to enhanced evaporation from interception storage (Hudson et al. 1997). As a part of this work, hydrological process studies of evapotranspiration, soil hydrology and groundwater response have given some

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important insights into the hydrological behaviour of upland catchments in the British Isles and the ways in which they influence the hydrology of floods and baseflows in rivers downstream (Kirby et al. 1991; Haria & Shand 2004; Bell 2005). As part of the CHASM research project, recent hydrological research in the Severn has focused on upscaling beyond the headwaters at Plynlimon. Other recent work has included the hydrology of lowland floodplains in relation to flood attenuation and sustaining baseflows (Burt et al. 2002; Bates et al. 2006). More recently, in terms of hydrological research, the Tern sub-catchment forms part of the NERC-funded Lowland Catchment Research (LOCAR) programme (Clay et al. 2004). This reflects a general shift in the focus of UK hydrological research from upland, responsive catchments to lowland permeable catchments. The interconnections between responsive upper catchments and lowland floodplains have become an important issue on the river Severn in recent years (McCartney & Naden 1995). In 2000, 2002 and summer 2007 repeated flooding along the Severn caused major problems in towns like Shrewsbury. The hydrology of the Severn is affected by more than land use change. Large reservoirs on headwater tributaries, such as Llyn Clywedog (1963), regulate the river and form part of interbasin water transfers in the case of Lake Vrnwy (1881) on the River Vrnwy that forms Liverpool’s water supply. The regulation is managed via flow requirements downstream at Bewdley, which under low flow conditions requires a 4-day travel time. In Permian and Triassic sandstones on the lower catchment, major aquifers are managed for water supply, and the Shropshire groundwater scheme is used to augment flows in the river if prolonged drought conditions compromise upstream reservoir releases. Intensive hydrological studies in the Plynlimon catchments also included detailed assessment of the water balance of the Wye catchments, examination of soil hydrological processes, and most recently groundwater influences on river flows (Hudson et al. 1997). Significant reservoir developments on the upper Wye at Craig Goch resulted in regulated flows downstream. Nevertheless, flood problems also remain a major issue on the Wye. Lying in the west of England, precipitation in the Mersey basin is relatively high with a catchment average of just over 1000 mm. This is accentuated by the orographic effect of the western Pennines where rainfall is highest. The disjunction between the uplands of the Mersey and its lower catchment results in a marked contrast in its hydrology. Tributaries such as the Irwell (Photo 10.10), Tame and Etherow have their sources in the peat covered moorlands on the Pennines that are mainly composed of carboniferous grit and coal measures. The central and southern parts of the catchment, which are drained by the Rivers Bollin and Weaver, are underlain by Triassic sandstones and marls and covered by boulder clay (Harvey 1997). Aside from this natural diversity, the catchment is heavily impacted by numerous towns and cities. Flow regimes in tributaries are variously affected by

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PHOTO 10.10 The River Irwell near Manchester, a tributary of the River Mersey (I. Roberts).

reservoirs, particularly in the Pennine headwaters, abstractions (for domestic, industrial and agricultural supplies) of surface and groundwater sources, and large effluent returns and urban storm drains. The Yorkshire Ouse drains a large part of northern England and rainfall is unevenly distributed across the catchment. It is highest in the Western Pennines, where peaty soils result in flashy hydrological regimes. However, in parts of the Pennine tributaries, carboniferous limestones provide karst environments and groundwater dominated hydrological regimes (Talling & Parker 2002). In the North York Moors in the northeast of the catchment, peaty soils dominate a landscape of Jurassic sandstones. Some limestones also outcrop and drain into the Derwent (Carey & Chadha 1998) and hydrological regimes tend to be flashy and responsive (Evans et al. 2005). Large lowlands of the catchment covering the Vale of York and Vale of Pickering are mantled by glacial drift, and although precipitation is lower in these areas, the soils tend to be clay rich, drained and responsive. These soils limit the amount of groundwater recharge to the Triassic sandstone aquifers beneath. In the southerly Pennine tributaries, urban areas and reservoirs constructed for mill towns have artificial influences on hydrological regimes. Flow regimes in tributaries are variously affected by reservoirs, particularly in the Pennine headwaters, abstractions (for domestic, industrial and agricultural supplies) of surface and groundwater sources, and effluent returns. The city of York has major flood problems as it was developed on the floodplain of the lower Ouse (Kuchment et al. 1996). The last recent major flood occurred in 2000 and flood forecasting, warning and alleviation are major priorities (Abrahart & See 2002).

Although many Pennine tributaries of the Trent are characterized by upland peat-dominated catchments, some are also affected by regulation, particularly in the southern tributaries such as the Derwent in the Peak District National Park (Maddock et al. 2001). Extensive parts of the catchment are influenced by urban runoff from the cities of Birmingham, Derby and Leicester. The large urban populations living in the catchment also dictate that sewage discharge is an important component of flows, particularly during summer low flows. Additionally, extensive use of water from the Trent as cooling water means that effluents are a significant component of flows. A final artificial influence on flows are the large flat lowlands of the Trent – in many places covered in clay-rich glacial drift – that results in a high density of agricultural drainage (Robinson et al. 2000). The upland headwaters, and long concentration times, result in flooding potential in many parts of the lower Trent and considerable effort is being expended on flood management (Williams & Archer 2002; Environment Agency 2004). The dominance of chalk in the Thames catchment results in a hydrological regime with a strong baseflow component that accounts for 70% of natural flows and >95% in many chalk tributaries such as the Kennet and Pang (Marsh et al. 2000). Extensive work has been carried out assessing the nature of groundwater–surface water exchange in the Thames catchment (Adams et al. 2000). The importance of the chalk groundwater in providing 35% of public, industrial and agricultural supplies in the Thames region has been a major motivation. With high population levels and essential economic activity within the catchment, the Thames has had a long history of human intervention in its hydrological regime (Gurnell & Petts 2000). The most serious problem

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has probably been that of excessive surface water and groundwater abstraction, which together with reduced recharge from extensive urban areas, has caused a reduction in river flows (ca. 50% of flows are abstracted) and lowering of water tables (Littlewood & Marsh 1996). This has caused serious low flows in many tributaries, some of which dried completely in the droughts of the late 1980s and early 1990s. Artificial recharge using excess winter surface water abstractions (up to 100 ML/day) and more careful aquifer management has reduced the scale of this problem in recent times (Adams et al. 2000). Infrastructure investment in the Thames floodplain means that there is a serious flood problem with >1.5 million people in the catchment at flood risk (Laverie & Donovan 2005; Marsh et al. 2005). Severe flooding in the autumn of 2000 resulted in prolonged inundation, as the high groundwater levels that generated the flood took a long time to subside (Kelman 2001). In the Frome–Piddle system, the westerly coastal location results in annual precipitation to these catchments of around 900 mm. Although the geology is dominated by the Cretaceous age, the two catchments are slightly different. The Frome catchment shows a sequence from Greensand and Gault clay in the northern and western headwaters, and chalk in the central part of the catchment (covering 50% of the catchment area). The lower catchment valley has chalk covered by Tertiary sands and gravels (Paolillo 1969). In the Piddle, the chalk dominates the headwaters and mid-reaches, although this is covered by Tertiary sands and gravels in the lower catchment. The dominant influence of chalk in the local geology results in a groundwater dominated flow regime, accounting for 80% of the discharge in both systems. The groundwater influence is evident in streams known as winterbournes – which are dry in summer but flow in winter when groundwater recharge raises water tables that then discharge as springs at the head of winterbournes. Groundwater supplies a significant proportion of water in the catchment and pumping from deep boreholes dictates that the Piddle, in particular, has been affected by groundwater abstraction. The actual source of the river Shannon is a spring from a karstic cave system in County Cavan (Gunn 1996). Such karstic systems are common in many limestone dominated parts of the Shannon catchment and can contribute to prolonged serious flooding of seasonal wetlands known as Turloughs (Kilroy et al. 2005). The annual precipitation is fairly evenly distributed throughout the year, and monthly averages vary between 100 mm in December and January, to around 60 mm between May and July (Mills 2001). Monthly evapotranspiration peaks at around 70 mm in June and July, and falls to around 5 mm in December and January. The flat topography of the basin, high precipitation, well-connected karstic groundwater systems and extensive peat bogs dictate a responsive hydrological regime and potential for flooding. Despite the long history of arterial drainage, Bhattarai and O’Connor (2004) conclude that the effectiveness on flood control was largely limited to the first decade or so after

scheme implementation, thus the river’s flood regime appears relatively unaltered (Spink et al. 1998). The river is regulated for hydropower production at Ardnacrusha which, when installed in 1929, was the largest hydroelectric scheme in the world. Although this only impacts the hydrological regime of the river near Limerick, it contributes to river fragmentation. Most of the river is affected by the regulation of Loch Allen for hydropower, which provides compensation waters in the summer (Cullen 2002). Water levels in a number of other lochs are regulated for navigation purposes.

10.4.3. Biogeochemistry As the first major industrialized country, Britain was subject to rapid and intense urbanisation and chronic freshwater pollution in many rivers (Moss 1998). High population densities resulted in extensive pollution from domestic sewage that contaminated water supplies and had severe public health implications in the Victorian era with outbreaks of waterborne diseases like typhoid and cholera being common (Newson 1997). The use of rivers as a means of disposing of industrial waste had catastrophic ecological impacts downstream of main urban centres. Fortunately, this prompted increasingly stringent discharge controls administered by increasingly sophisticated regulatory authorities and the expansion of sewage treatment facilities. Together with the industrial decline in the late 20th century, this has resulted in many water quality improvements around major urban and industrial centres in recent decades (Cook 1998). However, pollution from urban areas continues and there is currently concern over the influence of more exotic pollutants such as endocrine disrupters from hormonal contaminants in sewage effluent (Williams et al. 2000). The adverse water quality impacts of many towns and cities in the lowlands of the south and east of the British Isles resulted in most water supply reservoirs being located in the wetter, less populated and cheaper lands of the northwest (Cook 1998). Water supply reservoirs have been built in these areas since the Victorian era, mainly to spatially separate zones of water supply and zones of effluent discharge. In 1950s and 1960s many rivers in the Scottish Highlands were also dammed as part of hydropower schemes that also have water supply functions (Gilvear 1994). Despite this, it would be misleading to suggest that water quality problems in the British Isles have been restricted to industrial and urban sources. As already noted, over the past 50 years agricultural intensification, which saw significant increases in fertilizer and pesticide applications, produced a concomitant increase in nutrient loads in many lowland rivers (Williams et al. 2000; Department for Environment Food and Rural Affairs, 2003). In the British uplands, enhanced deposition of atmospherically derived acidic-oxide pollutants has caused acidification of streams. This has particularly affected afforested catchments, as enhanced acid loading on forest canopies has accelerated soil acidification

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and enhanced leaching of toxic inorganic aluminium into rivers (Reynolds et al. 1988; Ormerod et al. 1989; Soulsby 1997). In moorland areas used for sheep grazing, pesticides used for sheep dip have contaminated streams and there has been concern that pathogens from animal excrement form microbiological pollutants (Hooda et al. 2000). However, the biogeochemical processes that govern stream water quality vary in relation to catchment characteristics and land use pressures (Table 10.3). Relatively limited impact of human activities is evident in the general water quality issues in the highlands of Scotland (Soulsby et al. 2002). Water quality throughout virtually whole of the River Spey catchment is good or excellent, reflecting its low population density and upland-rural character (Scottish Natural Heritage 2003). The mountain streams tend to have a circumneutral pH. Alkalinity is dependent on geology and is low when resident rocks such as granite dominate and high when calcareous rocks or baserich mineralization occur (Soulsby et al. 2004). Nutrient levels tend to be below or close to detection, with N and P being tightly cycled by terrestrial and aquatic vegetation. A number of localised issues do occur. The Cairngorms headwaters of the Spey and part of the Monadliath mountains are dominated by slow weathering granite and schist that give rise to acidic soils and acid sensitive catchments (Soulsby et al. 1997b). Although levels of atmospheric deposition are modest, anticyclonic weather particularly in winter can bring high pollutant loads from central Europe. This can be compounded in stable, prolonged winters as deposition in snowpacks can cause marked acid episodes when snowmelt occurs and stream pH can drop near 4.0 (Davies et al. 1993). Recent emission controls have resulted in a reduction in acid deposition and a general reversal of stream water acidification in the Cairngorm region (Harriman et al. 2003). A distinct water quality issue in the Spey catchment is from discharges from whisky distilleries (Scottish Natural Heritage 2003). This causes thermal pollution and can increase the loads of biochemical oxygen demand and

heavy metals, particularly Cu to streams (Paton et al. 1995). Further alteration to the thermal regime of the Spey is in the operation of reservoirs like Spey dam in the headwaters, although the effects are usually localised. The Spey catchment is largely oligotrophic and nutrient levels remain low as a result of the large volumes of clean water from the headwaters. Most nutrient inputs from domestic and industrial discharges are controlled by wastewater treatment plants. Even in the lower reaches of the Spey where agriculture is more prevalent as a land use, and provides an additional source of diffuse pollution, nutrient levels are modest (Harriman et al. 1994). The Tay system has excellent water quality for much of its length. Like the Spey, the headwaters of some parts of the Tay are acid sensitive, though the presence of calcareous metamorphic rocks in the west of the catchment means that the larger river system itself is relatively well buffered. The intense regulation system on the Tay has more marked impacts with highly modified thermal regimes immediately downstream of dams and less natural hydrochemical variation (Jackson et al. 2007). In the lower catchment, particularly between Dunkeld and Perth; and in the catchments of the River Isla, the better soils and milder temperatures result in increasingly intensive agriculture, which in some places is a significant source of pollution of N and P (Harriman et al. 1994). In general, nutrient and pesticide levels remain relatively low. The main north–south road and rail links between the densely populated central belt of Scotland and the Highlands in Inverness and runs through the heart of the Tay catchment along the wide flat valley bottom and can cause localised water quality impacts from road runoff. The water quality of the Tweed was extensively examined as part of the UK’s Land Ocean Interaction Study (LOIS) in the 1990s. The Tweed was a flagship study catchment in the initiative that sought to understand the water quality of major east coast catchments in the UK that drain into the North Sea (Robson & Neal 1997). The Tweed has excellent water quality, 99% of the river network is Class 1 according to the SEPA water quality classification scheme,

TABLE 10.3 Selected water quality characteristics of rivers in this Chapter

pH Alkalinity NH4-H TON PO4–P SiO2-Si SO4 Cl Na K Ca Mg

– mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L

Spey

Tay

Tweed

Mersey

Ouse

Trent

Thames

Frome

6.5 17 0.03 0.32 <0.01 <0.01 – 9 5.1 0.6 5.3 2.3

7.5 15 0.03 0.48 0.03 – – 6 – – 6.9 1.3

8.0 30 0.07 2.09 0.06 2.7 24 18 10.0 1.2 22 7

7.3 70.5 4.1 3.5 1.2 8.3 86 86 69 7.8 45 8.5

7.8 52 0.15 3.5 0.12 3.9 43 24 18.7 3.4 57 10

7.9 117 0.41 8.8 1.13 7.4 164 90 79 10.5 96 23

7.96 65 0.3 7.2 1.3 11.2 67 46 34 7.0 98 5.4

8.0 63.0 – – – – – – – – – –

Chapter | 10 British and Irish Rivers

and serious pollution is limited to sections of tributaries draining arable land with high levels of nutrient enrichment (Jarvie et al. 2002). Large parts of the Tweed catchment have been designated as Nitrate Vulnerable Zones. In these areas there are attempts to control diffuse pollution of rivers and groundwaters by fostering best practices in agriculture to minimise N leaching to surface waters (Tweed Forum 2003). More intensive agriculture and other land use change such as ground preparation for commercial forestry have resulted in increased fine sediment delivery into the Tweed (Walling et al. 2000). Analysis of floodplain sediments suggests that the most marked impact of such land use changes occurred in the late 19th century when a major effort on land drainage brought more land into agricultural use and again in the first half of the 20th century when forest planting rates accelerated (Owens & Walling 2002a,b). The importance of sheep grazing in the upper catchment dictates that disposal of chemicals used for sheep dips is a potential water quality problem needing careful management. This is particularly the case since organophosphate dips were replaced by those based on synthetic pyrethroids that are less toxic to humans, but much more toxic to aquatic environments. Sewage effluent is the most significant source of many pollutant chemicals in the Tweed. These are usually treated and discharge consents keep pollutant levels within environmental objectives for water quality. In some places, the presence of trade effluents from the electronics industry in Selkirk and Galashiels has contributed to heavy metal pollution in the river. The situation is much better today than historically when wastes from the textile industry (fabric conditioners, dyes, etc.) were discharged into the river in virtually every large town along the river. The LOIS project demonstrated the impact of agriculture on the catchment in terms of nutrient status and the legacy of industrial pollution from specific sites and used time series analysis and GIS technology to produce spatial plots of water quality conditions around the catchment. After initial interest in the effects of forestry on the hydrology of upland rivers, research in the headwaters of the rivers Wye and Severn at Plynlimon focused on water quality issues after the mid-1980s (Neal 1997). Of particular interest was the way in which increasing forestry was associated with increased acidification of surface waters and mobilization of toxic metals such as aluminium (Neal et al. 1989; Neal 1997). Precipitation amounts, coupled with the ability of forest canopies to ‘scavenge’ acidic oxides from the atmosphere, explained increased acid loads onto catchments with mature commercial forest cover (Soulsby & Reynolds 1992). The lower Palaeozoic mountains of midWales are particularly sensitive to acidic inputs as the rocks are base poor, and with the intense leaching regime from high rainfall, soils are highly acidic (Soulsby 1997). Weak sulphuric and nitric acids were subsequently washed from forest canopies, dissociated in soils with H+ ions exchanging with Al3+ on soil cation exchange sites. Then mobile anions of SO42 and NO3 were able to leach Al3+ into streams

401

(Reynolds et al. 1988). Emission control legislation has reduced the severity of acidification over the past 2 decades, and forestry is controlled in acid-sensitive areas. It has been shown that forest felling operations can cause a short-term exacerbation of acidification by releasing NO3 as a mobile anion from decomposition and the loss of root uptake (Neal et al. 1997). Although buffering downstream restricts acidification problems to headwater areas, the legacy of historic metal mining in the upper catchment still propagates a downstream impact through elevated metal concentrations in fine sediments (Taylor 1996). In the lower Severn catchment agricultural chemicals become more important as sources of pollution. In particular, intensive agricultural production in the Vale of Evesham has been associated with surface water pollution with N and P. Northern tributaries draining the central Midlands where heavy industry in the Black Country has caused contamination with industrial pollutants and sewage effluent. Water quality issues in the Wye are similar to those in the rural parts of the Severn (Jarvie et al. 2003). In some places in the upper Wye, liming experiments have been carried out to minimise the effects of acidification that are characteristic of the upper Severn. In the lower Wye, acidification is not an issue and stream pH tends to be around 8.0, varying between 7.5 (at high flows) and 8.5 (at baseflows (Jarvie et al. 2005)). The control of nutrients has been a major issue in the Wye. In the headwaters at Plynlimon, N in precipitation is retained in the catchment, although some NO3–N leaching is evident (Reynolds et al. 1992). In the lower catchment where fertilizer application is highest, NO3–N levels can exceed 60 mg/ L in some tributaries, although concentrations are typically 15 mg/L NO3–N, whilst PO4–P concentrations are 64 mg/L. High populations and a long history of industrial activity dictate that the Mersey has been one of the most grossly polluted rivers in the UK. Sewage-related microbiological pollution in 1848 led to hundreds of people dying in a cholera epidemic (HMSO 1874). The chemical industry, which developed initially in support of the textile industry in Lancashire, has grown into one of the largest centres of chemical engineering in the UK. As a result, the Mersey has been historically polluted with chemicals ranging from raw sewage, heavy metals such as mercury, pesticides such as DDT, to other persistent organic contaminants such as polychlorinated biphenyls (PCBs) and pentachlorophenol (PCP) (Osborne et al. 1997; Turner & Mawji 2005). In the middle of the 20th century, >25 km of the Mersey estuary was anoxic, and ammonia levels exceeded 12 mg/L of NH4–N (Wood et al. 1999). Industrial decline and more stringent controls on pollution have dictated that the past few decades have seen marked improvements in water quality. In 1985, the Mersey Basin Campaign recognised that the Mersey had the most grossly polluted estuary in the UK resulting from historic and contemporary pollution from sewage and the chemical industry. Increasingly effective sewage treatment since 1981 and more effective control of effluents from the

402

petrochemical industry have improved the situation significantly throughout the system (Sparshott 1991; Kidd & Shaw 2000). Now, dissolved oxygen levels in the lower river generally remain >60% saturation and the biochemical oxygen demand of the river has been reduced from 300 t/day in the 1970s to just 30 t/day in 2001, mainly as a result of improved sewage treatment (Wood et al. 1999). Given the diverse nature of the Ouse–Trent system, the biogeochemistry of the river is highly variable and differentially affected by human activities (Sanders et al. 1997). The Derwent tributary of the Ouse, draining from the North York Moors, is relatively clean. Stream pH is circumneutral, although the sandstone bedrock and peaty soils in some areas dictate that alkalinity is low and upland streams are prone to acid episodes (Neal et al. 1998; Evans et al. 2005). Nitrate levels are <0.5 mg/L NO3–N in these headwaters, but downstream in the Derwent they increase to 2–5 mg/L from agricultural inputs (Robson & Neal 1997). The extensively grazed streams of the Pennine headwaters, like the Swale, have relatively low nutrient concentrations but a higher pH and alkalinity that reflect the influence of carboniferous limestones (Talling & Parker 2002). This limestone influence also affects the inorganic carbon budget of the rivers (Eatherall et al. 2000). High grazing intensities in the uplands can produce high-suspended sediment concentrations (Smith et al. 2003) that can also play an important role in heavy metal pollution from abandoned mines in the Pennines. Metals such as Pb and Zn, mainly stored in fluvial sediments, remain elevated both in solution and in particulate complexes (Walling & Owens 2003). The large millennium floods in the autumn of 2000 resulted in significant heavy metal pollution of river floodplain soils from upstream mining spoils (Dennis et al. 2003). In the upland tributaries like the Wharfe, the fine sediment load predominantly (70%) comes from uncultivated top soil, whilst downstream in the Ouse system cultivated top soil and eroding channel banks become major sediment sources (Owens et al. 1999). In the southerly tributaries of the Ouse, Aire and Don, different dominant biogeochemical processes contribute to contrasting water quality characteristics (Dawson & Macklin 1998; Walling et al. 2003). Upland catchments in the Yorkshire Peninnes have important water supply reservoirs for towns downstream. The soils of these catchments form important carbon reservoirs with their peaty soils, and a widespread problem has been increased colour in surface waters from these catchments that violate drinking water standards (Butcher et al. 1992). The source of the increased colour is unclear, although climatic warming, air pollution, poor land management (such as moorland burning) and overgrazing have all been cited as causal factors. Further downstream, the effects of industrial pollution and sewage discharge become apparent (Carter et al. 2003). For example, NH4–N concentrations, mainly from sewage, exceed 10 mg/ L in the Don and Aire, whilst NO3–N concentrations, from oxidised NH4–N and agricultural runoff, exceed 5 mg/L (Robson & Neal 1997). Owens & Walling (2003) used chem-

PART | I Rivers of Europe

ical analysis of floodplain sediments to show how P concentrations adsorbed on fine sediments has increased from agricultural intensification. Increases in pesticides such as lindane have been shown, although concentrations are decreasing from the peaks in the mid-20th century (Cousins et al. 1995; House et al. 2000). Owens et al. (2001) showed the influence of past and current industry on PCB and heavy metal pollution in the catchment, whilst Jurgens et al. (2002) highlighted how sewage effluent has resulted in marked estrogen contamination. In the Trent catchment water quality has been affected by the dense population and a long history of human influence. High concentrations and ranges of most pollutants are evident in some part of the catchment. In terms of urban runoff, the river basin receives the discharge of heated sewage from some 4 million residents (Robson & Neal 1997). In the 1970s most of the dry weather flow in the lower system was composed of pollution discharges. Consequently, orthophosphate levels in urban rivers such as the Tame and Sour exceed 5 mg/L compared with <1.0 mg/L in upland tributaries such as the Derwent (Robson & Neal 1997). Ammonia levels are greatly elevated in urban tributaries. Use of water for cooling in coal-fired power stations in the Trent valley result in significant thermal pollution along the river (Jarvie et al. 2000). Heavy and light industries in the catchment result in 6600 discharge consents and 3400 abstractions licences being in force. Despite this heavy use of the catchment, historic analysis of water quality data shows significant improvements since the 1960s as a result of more effective sewage treatment, a tightening of discharge consents and decline of traditional heavy industries (Crabtree et al. 1999; Jarvie et al. 2000). Despite the scale of the urban and industrial impacts on the biogeochemistry of the Trent, the catchment has also significant areas of intensive agriculture with concomitant pollution problems. In many tributaries, and along the main stem of the river, NO3–N levels exceed 10 mg/L (Robson & Neal 1997). The natural geochemical characteristics of water in the river Thames are dominated by Ca-bicarbonate waters derived from the headwaters that mainly drain catchments underlain by chalk (Neal et al. 2000). Stream pH averages 8.0, varying between 7.8 and 9.2. Agricultural runoff has a major influence with high flows in particular showing elevated levels of N, P, suspended sediments and pesticides (Johnes 1996; Kinniburgh et al. 1997). Johnes and Burt (1993) showed that NO3–N levels can exceed 11.3 mg/L in many parts of the river. Williams et al. (2000) show that this reflects average annual increases of 0.1–0.2 mg/L over the second half of the 20th century. Total phosphate levels are elevated at 0.9–2.7 mg/L – often associated with high-suspended sediment levels that can exceed 50 mg/L (Neal et al. 2000). Despite the high levels of nutrient leaching, Neal et al. (2004a,b) suggest that many parts of the catchment may still be retaining these nutrients. Power et al. (1999a,b) suggest that pesticide levels in the Thames waters are declining, although a longer-term legacy is stored in river sediments

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(Scrimshaw & Lester 1997). Younger et al. (1993) suggested that river waters have the potential to contaminate large areas of chalk aquifer that support public water supplies, but the dominant fine, organic-rich sediments that characterize the stream bed have low permeability and prevents stream water ingress. Serious historic pollution of the Thames has resulted from untreated sewage being discharged from the burgeoning population of London. In the Victorian era, anoxic conditions of the river resulted in S reduction and the emission of H2S gas that was so noxious it disrupted proceedings in the Houses of Parliament (Newson 1997). Despite widespread improvements in sewage treatment, large sewage discharge still result in elevated ammonia levels in some tributaries in Greater London (Flynn et al. 2002). Urban streams are affected by >9000 effluent consents in the catchment that include >130 major industrial processes, 274 sites using radioactive materials and 845 waste management sites. Although now closely regulated, elevated levels of Pb, pesticide residues and radioactivity are still evident in some areas and in the sediments of the Thames Estuary (Power et al. 1999b, Hilton et al. 2004). Holdhaus et al. (2002) highlighted that endocrine disrupters derived from estrogen have contaminated both waters and sediments in the Thames via sewage effluent. The chalk streams of the Frome–Piddle system are characterized by a strongly calcareous chemistry with a mean pH of 8.1. Water quality of both rivers is high; according to the Environment Agency, 97% of the catchment demonstrated very good or good water quality for 2000–2003 (Environment Agency 2004). In terms of General Quality Assessments for nutrients, nitrate levels are elevated in the Piddle and its major tributaries, elevated phosphate levels (mainly from point source sewage inputs) are found in the Frome and its major tributaries. Fluxes from the Frome have been estimated to be as high as 23 400 kg/ha TP (Hanrahan et al. 2001). The freely draining nature of the catchment soils overlying an extensive chalk aquifer have resulted in 90% of the catchment area being designated a Nitrate Vulnerable Zone to combat rising nitrate levels, especially in public supply boreholes and streams with sensitive ecosystems. Concern over fine sediment problems in the chalk streams in southern England provided the motivation for some detailed investigations in the headwaters of the Frome and Piddle (Walling & Amos 1999) where excessive sedimentation is perceived to be an issue. Poor land management practices and erosion of river banks were identified as the main sources of these fine sediments, contributing some 9–12 t/km2/year to the river (Walling & Amos 1999). The lack of major urban and industrial developments, together with the traditional low intensity nature of the prevailing pasture-based agriculture, dictates that water quality in the river Shannon is generally good (Spink et al. 1998). In the most recent survey of freshwater quality in Ireland, the Shannon Internal River Basin District was found to have 66% of channel lengths unpolluted, 21% slightly polluted,

12% moderately polluted, and only 0.6% grossly polluted (EPA 2006). Nitrate concentrations in the Shannon are generally <1 mg/L NO3–N, and ammonia concentrations are around 0.04 mg/L NH4–N. Despite this, the presence of carboniferous aquifers in the catchment, often with shallow soils, means that local groundwater contamination of nutrients and faecal coliforms from agriculture is an issue in some areas (EPA 2006) and can affect surface waters. For example, Kilroy and Coxon (2005) highlighted how phosphate can be transported from agricultural land into groundwaters via bonding on fine sediments during the winter period as overland flow becomes a more important mechanism for runoff generation. Donohue et al. (2004) show N delivery to streams can be seasonal and highly episodic; a process that may be missed by more conventional sampling. Pollution risks within the Shannon are not, however, restricted to agriculture; sewage effluent can also be important. As Ireland still has a large rural population in dispersed houses and small settlements, septic tanks are an important means of sewage treatment, with >160 000 people in the catchment not connected to conventional sewage treatment plants (Barr & Thompson 2004). Consequently, given the low levels of natural aquifer protection, septic tanks can contribute to groundwater pollution and ultimately surface water pollution (EPA 2006).

10.5. AQUATIC AND RIPARIAN BIODIVERSITY The marked climatic, geological and topographic gradients found within the British Isles result in a rich diversity of riverine environments with a wide range of habitats and species assemblages (Ratcliffe 1977; Holmes et al. 1998; Wright et al. 1998). The post-glacial sea-level rise that created the British Isles, resulted in limited time for dispersal of freshwater organisms from the land mass that became mainland Europe (Fitter & Manuel 1986). Thus, species diversity, despite many introductions, is comparatively low. It is impossible to give a comprehensive overview of the ecology of the rivers in question in such a summary chapter and the reader is referred to more detailed sources (e.g., Ladle & Westlake 2005). What follows highlights some of the more general features of the aquatic and riparian habitats of the rivers under consideration, together with reference to some of the more significant associated species from a conservation and management perspective.

10.5.1. Macrophytes Most macrophytes associated with river corridors in the British Isles are found mainly in the riparian zone and floodplain wetlands that can form species-rich ecotones. Relatively few are found within the channel itself. Those that are, vary in relation to geology, altitude, water quality, velocity, gradient, depth and management regime. Channel

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PART | I Rivers of Europe

TABLE 10.4 (Continued )

FIGURE 10.3 Classification of British Rivers according to macrophytes.

macrophytes form important shelter and food resources for invertebrates, fish and birds. Some fish use macrophytes as spawning substrate and many invertebrates lay their eggs on them. Holmes et al. (1998) used channel macrophyte surveys as a basis for classifying British rivers into four main groups (A, B, C and D) based on physico-chemical characteristics and plant species composition (Figure 10.3, Table 10.4). Oligotrophic, fast-flowing upland rivers such as the tributaries of the Spey, Tay, Tweed, Severn, Wye, Mersey, Ouse and Trent are characterized by mosses such as Fontinalis squamosa, Hygrohypnum luridum and the liverworts Scapania undulata and Nardia compressa (Class D). Moving out of such headwaters, as valley gradients decline, channels become larger and more geologically weathered, and greater

TABLE 10.4 Characteristic taxa of river types Groups species

A

Nuphar lutea Oenanthe fluviatilis Ceratophyllum demersum Potamogeton lucens Sagittaria sagittifolia Rorippa amphibia

X X X X X X

B

C

D

Groups species

A

Berula erecta Callitriche obtusangula Rumex hydrolapathum Veronica anagallis-aquatica Scirpus lacustris Carex riparia Carex acutiformis Glyceria maxima Zannichellia palustris Apium nodiflorum Epilobium hirsutum Polygonum amphibium Ranunculus calcareous Elodea Canadensis Potamogeton crispus Potamogeton perfoliatus Myriophyllum spicatum Freshwater sponge Lysimachia vulgaris Scirpus sylvaticus Cladophora glomerata – alga Sparganium erectum Eupatorium cannibinum Alisma plantago – aquatica Solanum dulcamara Cinclidotus fontinaloides – moss Hildenbrandia rivularis – alga Ranunculus penicillatus Callitriche hamulata Myriophyllum alterniflorum Eleocharis palustris Equisetum fluviatile Fontinalis squamosa – moss Hygrophynum luridum – moss Pellia epiphylla – liverwort Scapania undulata – liverwort Solenostoma triste – liverwort Brachythecium rivulare – moss Racomitrium aciculare – moss Achilla ptarmica Ranunculus flammula Montia Fontana Carex nigra Carex nostrata Littorella uniflora Nardia compressa – liverwort Marsupella emarginata – liverwort Sphagna – moss Dicranella palustris – moss Schistidium agassizii – moss Viola palustris Juncus bulbosus Potamogeton polygonifolius Filamentous algae – alga Fontinalis antipyretica – moss Rhynchostegium riparioides – moss Angelica sylvestris Filipendula ulmaria Mentha aquatica Myosotis scorpoides Salix species

X X X X X X X X X X X X X X X X X

X X X X X

X X X X X X X X

B

X X X X X X X X X X X X X X X X X X X X X X X X X

X X X X X X X X

C

X X X X X X X X X X X X X X X X X X X X X X X X X

X X X X X X X X

D

X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X

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Chapter | 10 British and Irish Rivers

groundwater contributions increase the alkalinity of stream water, communities become more diverse (Class C) and the biomass is greater. These areas might include species such as Ranunculus penicillatus and Carex nigra on the lower mainstem of rivers like the Spey, the upper reaches of the Tay and Spey, larger channels in the headwaters of the Severn and Wye, and upper tributaries of the Ouse. In lower catchments, such as the lower Tay and Tweed, much of the Severn and Wye systems, or lowland areas more generally, such as the Mersey basin, Trent and Ouse rivers, plant communities are adapted to lower velocities, wider, shallow channels with low gradients and a higher base status. Species of Potamogeton become more common and communities are generally more diverse (Class B). The fourth class of river identified by Holmes is that of the most lowland rivers, like the lower Ouse and Trent, most of the Thames system and the Frome and Piddle (Class A, Figure 10.3). River floodplains are also important habitats for macrophytes with marked ecotones creating a range of habitat and species diversity. On the river Spey, the Insh Marshes are one of the largest, least disturbed floodplain fens in the UK. The area is designated as a Site of Special Scientific Interest and is managed as a nature reserve (Grieve et al. 1995). Such sites are now rare now in the UK, as most lowland river floodplains have largely been disconnected from rivers as a result of drainage and flood defence activities. Palaeo-environmental reconstruction of the Trent floodplain shows that it was originally a dynamic environment of marked biodiversity up until the past 200 years (Brayshay & Dinnin 1999). Now only small fragments of such floodplain habitats remain (Large et al. 1994). Likewise on parts of the Thames floodplain, wet meadows with species such as Alopecurus pratensis and Sanguis officinalis occupy a tiny fraction of their former area as riparian lands were drained and improved for agriculture (McDonald 2001). Elsewhere in the Trent catchment along urban rivers such as the Tame, aggressive channel management has largely confined river channels, degrading the overall riparian habitat and offering only limited opportunities for restoration (Davenport et al. 2004). In the Frome catchment, wet floodplain meadows have been irrigated with water from the river since the 1st century AD (Ladle & Westlake 2005). More recently in many chalk rivers, such irrigation is used for commercial water cress (Nasturtium officinale) production. Macrophytes of the Shannon are broadly similar to those of lowland rivers on mainland Britain. The extensive network of lakes on the Shannon system creates a much more extensive suite of lentic habitats. Current research in Ireland is using macrophytes as a basis for river and lake typologies (Kelly-Quinn et al. 2004). The floodplains of rivers like the Shannon often have rich wet grasslands known as ‘callows’ (Spink et al. 1998), although the widespread arterial drainage in the catchment has removed much riparian tree cover. Riparian corridors act as effective conduits for the seed dispersal of aquatic plants and this has facilitated the spread of several notable invasive species along British rivers (Wadsworth et al. 2000; Goodson et al. 2002; Truscott et

al. 2006). These include species introduced over the past 200 years, such as giant hogweed (Heracleum mantegazzianum), Himalayan balsam (Impatiens glandulifera), Japanese knotweed (Fallopia japonica) and monkey flower (Mimulus guttatus). Once established, such invasives can seriously affect riparian habitats and cost huge sums of money to control and eradicate. Algae in British rivers are relatively poorly understood, although recent years have seen increasingly detailed studies that have elucidated the patterns, processes and ecological significance of algal communities. Upland rivers such as the Spey and Tay tend to be too short and fast-flowing to produce high algal density and biomass. In the lower reaches of larger rivers such as the Severn and Thames slower velocities and the presence of hydraulic dead zones allow high growth rates and important source areas for phytoplanktion such as Bacillariophyta and Chlorococcales (Reynolds & Glaister 1993). In the Thames, chlorophyll a concentrations were observed to increase from 10 mg/m3 in winter to 30 mg/m3 in summer with blooms in spring and autumn (Ladle & Westlake 2005). Skidmore et al. (1998) carried out a catchment-scale appraisal of phytoplankton chlorophyll a in the Trent system. In general, concentrations and growth rates increased downstream with spring and summer peaks being followed by an autumn decline. Certain tributaries such as the polluted Tame and upland Derwent had much lower concentrations, whilst lowland tributaries, with high nutrient levels, such as the Soar, were quite high. Thus the general downstream zonation was complicated by local chemical and biological factors. Recent detailed studies of the Thames phytoplankton have been completed by Ruse and Love (1997). Recent work in the catchment of the river Shannon involved using epilithic algal communities to classify the trophic status of lakes (DeNicola et al. 2004). Benthic algae are more common in upland streams, such as those in the Spey and Tay, where colonisation of larger cobbles and boulders on stream beds occurs that can sustain quite vigorous growth of groups such as Cladophora during summer low flows. Such streams tend to be nutrient limited in terms of N and P, however, and increased flows during autumn often rafts biomass downstream as a significant autochthonous input to stream secondary producers (Twist et al. 1998). On lowland rivers, benthic algae occur, although in deeper rivers like the Thames, light penetration to the benthos may be limited to 10% of the rivers length (Ladle & Westlake 2005). Recent studies have made some progress in modelling algal growth and transport in relation to environmental variables (Whitehead et al. 1997).

10.5.2. Macroinvertebrates, Reptiles and Amphibians The macroinvertebrate assemblages of British rivers have been extensively studied and are dominated by insecta (Armitage & Petts 1992). Of the estimated 30 000 species of insect in Britain, 1000 exploit water edge habitat and

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>3500 spend all or part of their life cycle in freshwaters. Evidence from palaeo-ecological studies indicate that many species re-colonised British and Irish water courses rapidly in the post-glacial (Greenwood et al. 2003). Wright et al. (1998) have collated a wide range of macroinvertebrate data for the UK and developed a computer tool (RIVPACS) to predict the composition of invertebrate communities from environmental variables. Although there are many specialist taxa in the UK macroinvertebrate fauna, many have overlapping niches. In upland streams, approximating the type C and D streams of the Holmes classification based on macrophytes, Plecoptera, Ephemeroptera and Tricoptera are usually the dominant orders. Diptera, Mollusca, Oligochaeta, Crustacea and Coleoptera are also present, although usually in lower abundance. In lower order streams in the upland headwaters, Baetis rhodani is often the most abundant species, with nymphs of Rhithrogena semicolorata and Ephemerella ignita also common and widespread. In more lowland streams, like the type A and B streams, lower velocities and finer substrate results in increasing abundance of detritus feeders such as Simuliidae, the Crustacean Gammarus pulex and Tubificidae. Slow flowing margins, backwaters and floodplain wetlands are important for Odonata, particularly in lowland areas, but also in upland riparian wetlands. Many rare macroinvertebrates have been found to be associated with areas of exposed riverine sediments (Bates et al. 2005) and in complex ecotones along channel margins (Greenwood et al. 1995). The sensitivity of macroinvertebrates, together with their relative ease of sampling and identification, has resulted in them being used as biological indicators of water pollution and habitat degradation in river management. Tools such as RIVPACS allow the observed composition of communities to be assessed in relation to what might be expected given environmental conditions (Wright et al. 1998). Other tools, such as the use of BMWP (Biological Monitoring Working Party) scores, uses the presence or absence of species of differential pollution tolerance (e.g., pollution-intolerant taxa such as Rhithrogena, Heptagena or Perla) to be used to evaluate the extent of water quality problems and as a framework for assessing the biological response of pollution control measures (Clarke et al. 2002). There have been a plethora of studies of macroinvertebrate communities in UK rivers. Dynamic upland rivers like the montane headwaters of the Spey and Tay have variable hydrological and hydrochemical regimes. Gibbins et al. (2001) showed that geologic influences on water quality in these areas had a dominant influence on community composition, with abundance and diversity increasing with alkalinity. Despite the torrential nature of such streams, communities showed a high degree of resilience and persistence with relatively low species turnover over a 15-year-period. It was assumed that the high hydraulic roughness of such channels create refugia that can be used in high spates. The importance of natural flow regimes to macroinvertebrate communities in the river Tay system was illustrated by

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Jackson et al. (2007). They showed that downstream of two reservoirs, communities were highly degraded in terms of species diversity and invertebrate abundance (Figure 10.4). In one case, the lack of variability in reservoir compensation flows was the cause, whereas daily cycles in hydropower release had differential impacts because of lack of low flows in another. In higher order channels of the Spey and Tay, the hydraulic, hydrochemical and morphological habitat diversity sustain important freshwater pearl mussel (Margaritifera margaritefera) populations (Hastie et al. 2004). This species is rare or extinct across much of its former range in the UK due to over-exploitation or deterioration in habitat quality. These rivers also have reasonable salmon runs that are important as the pearl mussel lifecycle involves a symbiotic relationship with salmonids (Hastie et al. 2004). The effects of afforestation and acidification in acid-sensitive headwaters of rivers like the Severn and Wye in the Lower Palaeozoic headwaters of mid-Wales has identified forestry-related changes to water quality, such as reduced pH and elevated Al concentrations as being responsible for reduced diversity and abundance of macroinvertebrate communities (Ormerod et al. 1989). A loss of species such as the Ephemeropteran Baetis rhodani and the Plecopteran Brachyptera risi have been noted as effective indicators of surface water acidification (Weatherley & Ormerod 1987). Work by Bradley and Ormerod (2002) showed that liming can be an effective treatment for acidification, in terms of increasing stream alkalinity, with treated streams showing modest improvements in macroinvertebrate diversity and abundance. Ormerod and Edwards (1987) have carried out extensive research on the effects of impoundments on the river Wye on macroinvertebrate communities, often showing adverse effects on abundance and diversity. Macroinvertebrates in the extensively urbanised parts of the Mersey, Ouse–Trent and Thames catchments have been

FIGURE 10.4 Taxon richness and abundance of main macroinvertebrates in regulated and unregulated parts of the river Lyon (after Jackson et al. 2007). Horizontal bars link sites with no significant difference.

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adversely affected by the complex cocktail of pollutants from industrial discharges, sewage effluents, storm drainage and contaminated land (Cao et al. 1997; Wright et al. 2000). For example, Amisah and Cowx (2000a) examined macroinvertebrates in the industrialized Don sub-catchment of the Ouse. Despite improvements in water quality as a result of improved sewage treatment and the decline of heavy industry, there were limited signs of recovery in pollution-sensitive macroinvertebrates. Crane et al. (2000) drew attention to the fact that accumulation of sediments in the hyporheic zone of urban streams may have an impact on macroinvertebrates long after surface water quality improvements had occurred. Despite these urban impacts, the less disturbed headwaters of these rivers have diverse and rare communities as Smith and Wood (2002) and Gunn et al. (2000) show for the limestone streams in the upper Trent catchment. More catchment-scale assessments of macroinvertebrate communities highlight the complexities of the influence on species composition and distribution of functional trophic groups. Previous work on the downstream continuum of the river Swale to Ouse showed general switches in functional groups from grazers (e.g., Plecoptera and Mollusca) in the headwaters to collectors (e.g., Oligochaetes) and predators (Odonata) in the lower river as predicted by the River Continuum Concept (Ward 1981). More recent work by Stockley et al. (1998) suggested that such patterns were less clear and that invertebrates had a much less marked impact on leaf litter processing than anticipated. Ruse and Davison (2000) also highlighted the complexity and diversity of Chironomidae in the Thames and demonstrated their sensitivity to changing environmental conditions. Macroinvertebrate communities have been the subject of detailed studies in the Piddle–Frome system in Dorset. For example, Cannan and Armitage (1999) showed the influence of geology on water chemistry and shifting community composition. Armitage et al. (2003) showed how the linkages between the river and its floodplain dramatically increase the diversity of macroinvertebrate communities in the river corridor. A total of 202 taxa were identified within the river– riparian–floodplain system, with 50 taxa being restricted to ditch networks in the floodplain. Recent work in Ireland showed that the macroinvertebrate fauna is broadly similar to that of UK rivers (Baars et al. 2004). A number of common taxa are widespread in most rivers in the Shannon: Baetis, Ecdyonurus, Elmis, Ephemerella, Gammarus, Limnius, Simuliidae and Chironomidae. Both siliceous and calcareous tributaries are characterized by the widespread occurrence of Hydropsyche, Leuctra, Potamopyrgus, Sericostomatidae, Dicranota and Hydracarina. Aphelocheirus and Ephemera danica were indicative of many, more calcareous, low gradient parts of the Shannon. A recent introduction in the Shannon has been the Zebra mussel (Dreissena polymorpha), presumably via recreational boats, which is an aggressive coloniser with detrimental impacts on native fauna.

The diversity of amphibians in the UK and Ireland is low, but those present are often important conservation priorities. The smooth newt (Triturus vulgaris) is relatively widespread throughout Britain and Ireland, whilst the great crested newt (Tritus cristatus) is rare in Britain and absent in Ireland. The palmate newt (Triturus helveticus) is also absent in Ireland and widespread only in rivers in the north and west. The common frog (Rana temporaria) remains widespread in Britain, and although it was introduced to Ireland, its numbers are declining. The common toad (Bufo bufo), in contrast, is absent in Ireland and widespread in Britain. The relatively poor reptile fauna of Britain and Ireland also form an important component of the biodiversity of river corridors and riparian zones. The common lizard (Lacerta vivipara) is widespread throughout the British Isles, whilst the slow worm (Anguis fragilis) is widespread in Britain, but absent from Ireland. Only two snakes, the grass snake (Natrix natrix) and adder (Vipera berus) are common in the riverine and wetland habitats in the UK. Grass snakes are most common in England, whilst adders are widespread, particularly in upland areas. Neither snake is present in Ireland.

10.5.3. Mammals and Birds Larger mammals of the British Isles have largely been hunted to extinction since colonisation in the post-glacial period. European brown bear (Ursus arctos), wolves (Canis lupus) and beavers (Castor fiber) are just three examples of mammalian extinction that have greatly affected the ecology of rivers and their riparian zones. River corridors, however, remain important habitats for other mammals that have conservation value. The otter (Lutra lutra) is an important species in British freshwaters that is protected by the EU Habitats and Species Directive. The species suffered a major decline in Britain in the 1950s as a result of habitat loss from agricultural drainage and pollution from organo-chlorine pesticides. The unpolluted Scottish rivers of the Spey and Tay remained strongholds for otters during this period, as did the uplands of Wales in the Severn/Wye headwaters. In much of lowland England, throughout much of the Mersey, Trent and Thames, otters became largely absent, although populations are showing signs of recovery (Mason & Macdonald 2004). Water voles (Arvicola amphibious) and water shrews (Neomys fodiens) are two small mammal species that also depend on aquatic habitat in the British Isles. Water voles tend to be associated with slower flowing rivers in lowland catchments like the Thames, Trent and Ouse where stands of Phragmites and Urtica form important food sources (Woodall 1993). However, it is now also recognised that they are well distributed in northern Scottish rivers like the Spey. Likewise, water shrews, one of only three species of shrew that are found in the British Isles that are aquatic, are most concentrated in lowland rivers. An additional group of mammals that are associated with riverine corridors is five of the 15 species of bats that are

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found in Britain. Natterer’s bat (Myotis nattereri) feed on insects in riparian woodlands, whilst Daubenton’s (Myotis daubentonii), Noctule (Nyctalus noctula) and Pippistrelle (Pipistrellus pipistrellus) bats feed over or near open water. The whiskered bat (Myotis mystacinus) uses both woodland and open areas as feeding habitats, particularly close to rivers. An important introduced mammal to river corridors in the British Isles is the American mink (Mustela vision), which has spread via escapes from fur farms. It is a catholic feeder with prey including fish, water voles, birds and their eggs and frogs. It is an aggressive and successful coloniser that has had a marked and negative impact on riverine biodiversity in many areas (Carter & Bright 2003). Over 20 species of birds are regularly found breeding and/or feeding along upland or lowland rivers in the British Isles (Ward et al. 1994). Of these, only the dipper (Cinclus cinclus) is largely confined to the uplands in the north and west. The red-breasted merganser (Mergus serrator) and goosander (Mergus merganser) are widespread on the Spey, Tay and Tweed, where salmonids can form a significant proportion of their diet (Gregory et al. 1997). They also occur along the rivers of northern England and Wales. The common sand piper (Actitis hypoleucos) is a common summer visitor on rivers north of the Humber and Severn estuaries. The insectivorous grey wagtail (Motacilla cinerrea) is particularly common in uplands streams in central and eastern England such as the headwaters of the Ouse and Trent. On lowland rivers, indigenous species regularly breeding include great crested grebes (Podiceps cristatus), little grebes (Tachybaptus ruficollis), mallards (Anas platyrhynchos), tufted duck (Aythya fuligula), mute swan (Cygnus olor), moorhen (Gallinula chloropus), coot (Fulica atra), kingfisher (Alcedo atthis) and reed bunting (Emberiza schoenuruus). Summer visitors include reed warblers (Acrocephalus scirpaceus), sedge warblers (Acrocephalus schoenobaenus) and sand martins (Riparia riparia). These birds tend to require in-channel marginal vegetation or backwaters for nesting or, in the case of kingfishers and sand martins, holes in steep river banks. These habitats have often been degraded as part of river management schemes, although habitat loss and water quality impacts on riparian birds are not restricted to the lowlands. Tyler and Ormerod (1992) examined the influence of afforestation and surface water acidification on dippers in UK uplands, where in some areas populations have declined. In contrast, Ospreys (Pandion haliaetus) have become re-established along rivers in Scotland, following re-introduction, reduced persecution and habitat protection (Saurola 1997). In winter, the lakes, wetlands and estuary of the Shannon are important habitats for hundreds of thousands of waders and waterfowl from the Arctic and northern Europe. From Arctic regions come waders such as knot (Calidris canutus), golden plover (Pluvialis apricaria) and black-tailed godwit (Limosa limosa), flocks of brent (Branta bernicla), barnacle (Branta leucopsis) and white-fronted geese (Anser albi-

PART | I Rivers of Europe

frons), and thousands of whooper swans (Cygnus cygnus). From Scandinavia and the Baltic come many ducks and waders, such as teal (Anas crecca) and lapwing (Vanellus vanellus), together with great flocks of thrushes and finches as the weather of the continent turns colder. Of Ireland’s breeding land-birds, the corncrake (Crex crex) and chough (Pyrrhocorax pyrrhocorax) are important in the Shannon. The corncrake (Crex crex), which migrates from Africa, prefers to nest in hay meadows. There were an estimated 300–400 corncrakes heard calling in the 1990s, including meadows on the banks of the River Shannon between Athlone and Portumna (Green 1996).

10.5.4. Fisheries With only 30 native species that spawn in freshwater, and less than half this number of additional species that have been introduced and naturalised, the Britain has a relatively limited freshwater fish fauna (Maitland 2004). A small number of native British fish species, the Atlantic salmon (Salmo salar), trout (Salmo trutta), twaite shad (Alosa fallax), smelt (Osmerus eperlanus) and eel (Anguilla anguilla), are euryhaline, and thus able to colonise from the sea. These fish, prior to human impacts, were probably relatively widely distributed throughout the British Isles. However, most native fish in mainland Britain, particularly the Cypriniformes (the most abundant freshwater group) are stenohaline. Species such as roach (Rutilus rutilus), dace (Leuciscus leuciscus), rudd (Scardinius erythrophthalmus), bream (Abramis brama), chub (Leuciscus cephalus), gudgeon (Gobio gobio), bleak (Alburnus alburnus) and minnows (Phoxinus phoxinus), amongst others, appear to have entered British waters in the post-glacial period (Lucas 2000). At this time, drainage from the south and east of England flowed out across a land bridge and may have been confluent with drainage from the river Rhine, or shared a floodplain with the Rhine, when sea levels may have been 100 m lower than they are today. Thus, the Thames, Humber (Ouse–Trent) and other rivers in the southeast may have had direct routes for species of stenohaline species to colonise (Wheeler 1977). An additional group of fish are often called ‘glacial relicts’, and are found in isolated freshwaters but are secondary freshwater species (Wheeler 1977). These once could migrate freely between rivers and the sea, but are now restricted to lake basins by barriers. They include the Arctic char (Salvelinus alpinus), and some populations of smelt and twaite shad. Human activities have had a widespread influence on the fish species composition of rivers in the British Isles. Species have been introduced from continental Europe and elsewhere. Moreover, stenohaline fish species with a restricted natural range have been spread more widely by deliberate and inadvertent means. Deliberate introductions have occurred to improve protein sources and increase fisheries potential. Accidental introductions have been facilitated by the UK’s extensive canal network allowing interbasin

Chapter | 10 British and Irish Rivers

transfers, accidental escape of live baits used in angling and interbasin transfers from water supply and hydroelectric supplies. As a result, fish species diversity is highest in the southeast and lowest in Scotland (Maitland 2004). Lampreys are a conservationally important group of eellike fish in British waters (Maitland 2004). The river lamprey (Lampetra fluviatilis) is found in estuaries and accessible tributaries of the Tweed and Tay. The species is normally anadromous, thus pollution or artificial obstacles such as weirs or dams impede migration. The brook lamprey (Lampetra planeri), the smallest of the lampreys found in the UK, is important in the Tweed, Tay and parts of the Wye. Like river lampreys, it requires clean gravel beds for spawning and soft marginal silt or sand for their larvae. The sea lamprey Petromyzon marinus is the largest of the lampreys found in the UK and is an anadromous species. It has similar needs for spawning and juvenile habitat. Sea lampreys have a preference for warm waters in which to spawn and seem to be relatively poor at ascending obstacles to migration. They are frequently restricted to the lower reaches of rivers, with the Spey being particularly important. The Spey is renowned as one of the leading Scottish salmon rivers, and is especially well known for its spring salmon fishery. This fishery exploits early returning adult fish that enter the river in the first months of the year. These fish generally spawn in the highest altitude headwaters of the river and spawn early in autumn (Tetzlaff et al. 2008). As with all major Scottish salmon rivers, the numbers of salmon are thought to have declined in recent decades and mortality at sea is believed to be the greatest cause (Friedland et al. 2005). The ecology of the Tay has probably been markedly affected by the development of hydropower (Maitland & Smith 1987). Considerable efforts have been made to install fish passes and sustain salmon in rivers upstream of the Tay’s network of dams (Gowans et al. 1999). Recent work has shown that both the homing of salmon to their natal stream, and the timing of their run, is finely selected and may be disrupted by marked regulation within the catchment (Youngson et al. 1994; Stewart et al. 2002). Moir et al. (2006) have shown that spawning location in headwater streams of the Tay is closely linked to the interaction of instream hydraulics and channel type. Salmon numbers in the Tay appear to have undergone a similar decline as in the Spey with hydropower operations probably adversely impacting salmonids. Despite a long history of human impacts on the quantity and quality of water in the Tweed, the catchment retains a wide range of riverine, riparian and wetland habitats that resulted in the river being designated a Site of Special Scientific Interest in 1976 and an SAC in 2005. The Tweed supports a run of Atlantic salmon that is a very important component of the local economy and has been the focus of catchment management initiatives. This has focused on riparian and in-stream habitat improvements that are hoped to benefit salmon populations (Tweed Forum 2003).

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Salmonids in afforested parts of the acid-sensitive upper Severn catchment have been adversely affected by acidification. Direct toxicity and adverse impacts on macroinvertebrates that are an important part of the diet of salmonids were deemed to be responsible (Weatherley et al. 1990). Similar processes have been evident in the upper Wye catchment, and liming has been advocated as a palliative management option (Weatherley et al. 1995). Other management in the Severn has prioritised removal of physical barriers to migration, which has also benefited eel populations (White & Knights 1997). As with Scottish salmon rivers, there is a worry that piscivirous birds like goosanders and cormorants (Phalacrocorax carbo) may be affecting stocks, with some advocating population control as a form of management. The lower reaches of the Severn and Wye also support fishing, mainly based on cyprinids. The fisheries ecology of the Mersey is in a state of recovery following the decline of traditional heavy industries, improved sewage treatment and more stringent controls on pollutant discharges (Nolan & Guthrie 1998; Johnes 1996). In the Ouse–Trent, the fishery has been grossly affected by water quality problems in urban and industrial areas. Salmon were once abundant throughout the system, but declined from the mid-19th century until the period of World War II, by which time they were more or less extinct in the Trent. In the 1920s, navigation weirs allowing boat access to Nottingham were installed and affected access (EA 2004). In the past, rapid urban storm runoff from the Tame resulted in an influx of low DO to the Trent that could deoxygenate downstream sections, resulting in fishery impacts (Crabtree et al. 1999) Water quality improvements, from improved sewage treatment and industrial decline, resulted in salmon being observed once again (EA 2004). A major constraint on recruitment is availability of spawning habitat given the long history of river management. Other issues in the Trent system include reservoir operations on headwater tributaries. Recent work has focused on exploring opportunities to incorporate ecologically acceptable flow regimes in reservoir operating procedures on the Derwent tributary (Maddock et al. 2001). A major issue on the Trent is water abstraction for power station cooling, which can affect fisheries by inadvertent mortality of juvenile fish at intake screens and as a consequence of thermal pollution (Carter & Reader 2000). In more polluted parts of the Ouse, fish population recovery from chronic water pollution has been more limited. Amisah & Cowx (2000a,b) examined fish population in the river Don following water quality improvements from improved sewage treatment and reduced industrial effluents that had decreased concentrations of NH4, BOD and certain heavy metals (notably Fe and Mn). Although brown trout and grayling (Thymallus thymallus) were present in the river, remaining water quality problems resulted in poor recruitment and the need for stocking programmes to aid fish stock recovery. Fish stocks in tributaries like the River Aire have also been affected, and as with some other rivers receiving sewage discharges, sexual disruption to species like gudgeon

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have been reported due to elevated levels of oestrogen (van Aerle et al. 2001). In rural parts of the catchment, flow augmentation from groundwater pumping in Vale of York tributaries have raised concerns over thermal impacts on fisheries (Cowx 2000). The River Thames supports a large freshwater and estuarine fishery, with a high species diversity including many introduced and estuarine species. This is a relatively recent recovery of the fish populations; as recently as 1920, no fish could live in the 46 km stretch of the estuary between Fulham and Tilbury due to pollution from untreated sewage and industrial waste following the rapid expansion and industrialization of the city in the early 19th century. The Thames was historically one of England’s great salmon rivers, with good quality spawning habitat in chalk stream headwaters. Documentary evidence from the 13th century shows that Thames salmon were an economically important food resource, and in 1810 alone, 3000 Thames salmon were sold at market. Yet by 1833, the species was extinct in the Thames, unable to penetrate the highly polluted estuary on their return from the sea. By 1953, the first attempts to adopt coherent sewage treatment strategies for London were developed, to improve control of industrial effluents. By 1974, individual salmon were being found again in the Thames, resulting in the Thames Salmon Rehabilitation Scheme being initiated in 1979. This initiative is now being carried forward by the Environment Agency (2005), who targeted 250 returning adults as part of their Action Plan. To achieve this, barriers to upstream migration are being removed, stocking is taking place, degraded habitats (Downs 1994) are being restored in important spawning tributaries such as the Kennet, and additional water quality issues (Yamaguchi et al. 2003) are being addressed. The Thames supports brown trout fishing in many chalk tributaries and cyprinids in many places. The Environment Agency is promoting fish enhancement projects on both rural tributaries like the Kennet, Pang and Cherwell and urban rivers like the Lea. Historically, chalk streams in southern England like the Frome–Piddle were important salmonid habitats (Strevens 1999). Adult Atlantic salmon have been counted automatically on the Frome for the past 25 years, resulting in the longest record for any English river system. The fish counter in the Frome showed that the annual salmon run in 1988 was over 4000 fish, but has fallen since then to 750 fish in 2004 (Beaumont et al. 2006). The composition of the run has also changed from multi-sea winter fish to grilse. Welton et al. (1999) note that brown trout are dominant in the upper Frome, with lower sections supporting grayling, dace, roach and pike (Esox lucius). Work by Masters et al. (2002) showed how pike extensively used floodplain ditches and wetlands, especially at high flows. Garner et al. (1998) showed how minnows moved between marginal habitat and mid-stream locations as a compromise between acquisition of food and metabolic costs of higher temperatures. Fish populations within the Frome–Piddle are currently threatened from agricultural pollution, with fine sediment mobilization respon-

PART | I Rivers of Europe

sible for habitat degradation (Walling & Amos 1999). In addition, groundwater abstractions have reduced fish habitat quality in some places (Strevens 1999). Linked to these issues is increased macrophyte growth within the stream channel that further facilitates sediment entrapment. The island of Ireland was soon isolated from mainland Britain and Europe in the post-glacial period, therefore natural fish assemblages in rivers like the Shannon are even more species poor than in the UK (Fitzsimons & Igoe 2004). All natural fish species in the Shannon are euryhaline, and there is archaeological and documentary evidence that cyprinids, pike and perch were introduced. Nevertheless, the native fish fauna of Ireland are an important natural resource, albeit one that is increasingly under threat. Agricultural intensification is a major concern, with diffuse pollution of nutrients or accidental organic pollution from poor farm management practices being major threats. The Shannon Regional Fisheries Board found that 70–80% of farms in a sub-catchment of the Shannon were discharging to the river. Arterial drainage has also had a significant negative impact on fish habitat, though canalisation (O’Grady & Gargan 1993). Linked to this, management and cutting of peat bogs has affected 92% of Ireland’s wetlands, and siltation from peat deposits affects many rivers in the Shannon, with peat deposits of 3 m affecting parts of Loch Derg and adversely affecting fish habitat. Livestock overgrazing, often promoted by EU subsidies, has also resulted in increased erosion, with concomitant delivery of P to rivers bound to fine sediments. Urbanisation and road development are impacting fish habitats, and increasingly active introduction of non-native fish, mainly accidentally as live bait for pike fishing, is adversely affecting native fish populations.

10.6. MANAGEMENT AND CONSERVATION 10.6.1. Economic Importance All of the rivers considered in this chapter have at least local and often national, or even international, economic significance. In most cases, the use of land within their catchments for agricultural production and urban and industrial development is fundamental to the national interest, and in many headwater areas, the management of moorlands are important to the rural economy. In many cases, direct consumptive water use is fundamental to economic activities, as is the use of rivers for effluent disposal. This means that each catchment usually has unique economic importance, with corresponding pressures that are manifest in the need for specific management and conservation strategies. The Spey sustains an important local economic base that includes hydropower production in headwater tributaries, water-based recreation, water demand – particularly during peak tourist seasons – and an economically important sports fishery for Atlantic salmon (SNH 2003). An internationally unique feature of the Spey is its importance as a source of water for 33 whisky distilleries that produce a variety of

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Speyside ‘single malts’, which have economic importance as major international exports and local cultural significance. The Tay is an economically important salmon river, and has some distilleries, but its main economic significance is its central role in the production of renewable energy from hydropower. This conflicts with its importance as a fishery, and also with its conservation significance reflected in its designation as an SAC. In addition to its biodiversity resources, the Tay provides an important base for a range of tourist activities such as canoeing. Salmon fishing is a key activity on the Tweed, Wye and Severn, although provision of public, industrial and agricultural water supplies to communities in and outside the catchments is also important. In the densely populated Mersey, Ouse, Trent and Thames catchments, urban and industrial water supplies and use of rivers for effluent disposal are fundamental to the economy of southern, central and northern Britain; with the use of water for cooling in the Trent valley fundamental to national energy supplies. The Shannon also has potentially conflicting economic values. The peat bogs of the catchment, and the flow of the river itself are important energy resources for Ireland. The exploitation of these resources requires potential impacts on the aquatic environment, and has the potential to threaten the economically important fisheries of the Shannon and the economic value of water-based recreation from boating activities. All of these, of course, have potential impacts in the conservation value of the river system.

10.6.2. Conservation and Restoration Recognition of the damage that had been done to British and Irish rivers, and the development of effective, ameliorative restoration management strategies, has been relatively recent. In the UK, despite earlier legislation, the 1974 Control of Pollution Act allowed much more effective management and control of point source pollution. In the next decade, this paved the way for more effective sewage treatment facilities in major urban areas and dramatically improved the quality of sewage effluents. It also resulted in tighter controls on the quality of industrial wastes, which became less of a problem as changing global economic circumstances led to a decline in traditional, heavy industries. Thus restoration of British rivers initially focused on water quality issues. Formal conservation of rivers was restricted to designation of sites, which initially were specific reaches of rivers, as Sites of Special Scientific Interest (SSSIs). This was a useful first step, but as designation only meant that a land owner had to inform the government conservation authorities of intention to carry out potentially damaging operations, it was often relatively unsuccessful. Later designation of whole rivers as SSSIs was a further step forward, although a major bureaucratic exercise given the number of riparian owners. Since the late 1980s, recognition of the need for more sustainable river management has grown. Water quality concerns have now extended to the problems of diffuse pollution

and their amelioration. Several dry years in the late 1980s and early 1990s focused attention on river regulation, water abstraction and the need to assess ecological issues when assessing environmental flows. Finally, the physical damage that has occurred to rivers as a result of channel management and land drainage has been highlighted, and the resulting damage to aquatic habitats has been recognised. The restoration of river channels is an increasingly important issue in British rivers and demonstration sites and habitat enhancement initiatives have been promoted by organisations such as the River Restoration Centre in the UK. This has had a positive effect on the policies of regulatory authorities. In Ireland, fisheries boards have promoted use of restoration techniques to improve habitat in rivers that have been affected by arterial drainage. European legislation under the Habitats and Species Directive has provided the basis for current conservation in designated certain rivers on the basis of species protection, which for the UK and Ireland particularly focus on Atlantic salmon, otters, fresh water pearl mussel, lampreys and river jelly lichen. Most rivers are not designated as SACs and need more generic protection. In some cases, as with parts of the Shannon, designation of Nitrate Vulnerable Zones may help restore water quality conditions. For most rivers, this protection will again be provided by legislation at the EU level through the Water Framework Directive.

10.6.3. Catchment and River Basin Planning As with all other member states of the EU, the EU Water Framework Directive is now the central piece of legislation guiding water resource and river management in Britain and Ireland. The identification of River Basin Planning Districts (RBPDs) will require a comprehensive assessment of river basin states, identification of existing and likely future pressures, and an approach to management that will not compromise the ecological status of the river in question. The development of management plans for river catchments has had already had a fairly lengthy history, particularly in England and Wales. The National Rivers Authority, the predecessor of the Environment Agency (the current competent authority for implementing the Water Framework Directive) developed an approach to catchment management in the early 1990s. When established in 1989, the National Rivers Authority, for the first time combined water resources, flood defence, pollution control, fisheries management and conservation functions within a single organisation (Walker et al. 2000). In some of the most pressured systems, such as the Thames, the new organisation created an enabling environment that facilitated more integrated approaches to the management of catchments (Gardiner 1994). Hitherto, regulatory authorities had primarily been concerned with water pollution control. In the 1990s, most river catchments had Catchment Management Plans produced. These subsequently were incorporated into Local Environment Agency Plans (LEAPs)

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(Newson et al. 2000). The formal process of Catchment Management Planning allowed multi-functional teams to assess the status of catchments, identify major management issues and propose solutions, which identified the partnerships needed with other agencies to implement management objectives (Walker et al. 2000). In Scotland the situation has been more complex. The Scottish Environment Protection Agency was established in 1996. It replaced the pre-existing River Purification Boards (RPB’s) that had responsibility mainly for pollution control. Although SEPA has a wider remit than the RPB’s, its powers are much more restricted than that of the Environment Agency in England and Wales. SEPA are now, for the first time, formally approaching the issues of integrated catchment planning throughout Scotland as part of its responsibility for implementing the WFD (SEPA 2006). Catchment planning has proceeded in Scotland largely on the basis of issue-driven grass-roots initiatives. For example, despite the status of the Spey as one of the least disturbed rivers in the UK, it will continue to be subject to environmental pressures. Tourist pressures continue to grow, as do the demand for increasing housing as more people seek to relocate or retire to rural areas such as Speyside. A recent land use change in increasing use of some of the Spey tributary catchments for sites of wind farms as pressure to increase renewable energy sources increases. Fortunately, the high conservation status of the catchment means that much falls within the Cairngorms National Park, and the designation of the river as a Special Area for Conservation has forced stakeholder interest groups to develop a Spey Catchment Management Plan (SNH 2003). This has engaged the notoriously fragmented range of statutory bodies involved in the management of Scottish freshwater resources and private interests to develop a strategy of protecting the diverse natural resources of the river (Leys 2001). Moves toward more integrated approaches to management are less advanced on the Tay. In part this highlights the political sensitivities of the Tay, where hydropower generation has a powerful control on the management of flows within the river. It was hoped by fisheries and conservation groups that the implementation of the Water Framework Directive would provide an opportunity for movements to more ecologically acceptable flow regimes in the Tay catchment. However, many rivers have been designated as Heavily Modified Water Bodies and will have lower requirements for maintaining ecological potential from the Directive (SEPA 2006). The importance of salmon fishing to the local economy dictates that salmon conservation has been a major motivating factor in movements toward integrated catchment management. The Tweed Foundation was established as a Charitable Trust by the River Tweed Commissioners, the statutory body responsible for fisheries management on the Tweed, to provide scientific assessment of the catchment and its resident stocks of salmon and trout. The Foundation created the impetus for the Tweed Forum that provided a basis

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for engaging the wider range of stakeholders with interests in the Tweed. This resulted in a catchment management plan for the catchment being produced that has seven strategic aims: (i) maintaining and enhancing water quality, (ii) ensuring that there is water available to support abstraction whilst protecting the needs of the environment, (iii) maintaining and enhancing the status and distribution of riverine, riparian and wetland species and habitats, (iv) ensuring that all river engineering respect the physical, ecological and aesthetic integrity of the river system, (v) adopting a catchment-wide sustainable approach to flood management, (vi) promoting tourism and recreation along the river and (vii) establishing a framework for delivering the catchment management plan. In England and Wales, the overall management structure for the Severn, Wye, Ouse, Trent, Thames and Frome are all similar, although local management priorities will vary. The main current process is developing River Basin Management Plans, as part of the WFD. At present, catchment management planning focuses on controlling water management through Catchment Abstraction Management Strategies (CAMS), developing flood management plans (especially in the case of the Severn, Ouse, Trent and Thames) and fisheries action plans (in the case of the Wye and Trent). On the Mersey, successful partnership approaches focus on reducing pollution problems and improving water quality (Riley & Tyson 2006). In the case of the Thames, future management will require tackling the issue of population and economic pressure that are predicted to require a 20% increase in new housing by 2021. There has been marked criticism on the problems of fragmented management in the Thames and highlighting of the poor integration of policies for land use planning, biodiversity, flood defence, tourism and agriculture and engineering for flood management. Like much of southern England, the catchments of the Frome and Piddle face marked environmental change. Increasing population levels and business focus result in growing development pressures for increased urban expansion and water demands. In addition, climate change predictions are for warmer drier summers and heavier winter rains. In a groundwater dominated catchment this results in increased possibilities for streams to dry in summer and prolonged groundwater floods to occur in winter. Low flows will be managed by CAMS (EA 2005) and the EA are promoting Landcare Partnerships to promote best management practices to mitigate impacts on the freshwater environment. To this end, it is hoped that initiatives such as LOCAR provide a basis for science driven management. In the Republic of Ireland, water and catchment management is being revolutionised by the Water Framework Directive (Barr & Thompson 2004). Currently a major research effort is underway to provide the scientific underpinning for management of the Shannon basin. Previously, the catchment was managed for hydropower production, fisheries and recreation, albeit in a fragmented and poorly integrated

Chapter | 10 British and Irish Rivers

manner. The WFD has the potential to set new agendas for more ecologically based approaches to river basin management in Ireland that will enhance integration and hopefully levels of environmental protection.

10.7. CONCLUSIONS AND PERSPECTIVES The rivers of the British Isles are characterized by a high degree of landscape diversity in a relatively small area. The post-glacial legacy of separation from mainland Europe gives the rivers of Britain and Ireland distinct ecological characteristics. The rivers are relatively small and have low species diversity. The nature of these rivers has been affected by a prolonged history of human management. Most notably the scale, rapidity and overwhelming impacts of early industrialization and urbanisation dominated many river systems. This eventually resulted in frameworks for restoration, initially through pollution control and subsequently, wider water resource management that have allowed many of the gross impacts of human activity to be reversed, and the ecological status of rivers improved. The fact that the rivers in Britain lie within the jurisdiction of single nation state has helped in this regard. In Ireland, the WFD is likely to result in much more integrated approaches to managing, and improving the ecological status of rivers like the Shannon. In the more remote parts of Britain and Ireland, rivers encompass some of the least disturbed habitats and landscapes in Europe and form an important part of the network of conservation sites protected by the Habitats and Species Directive. It is to be hoped that the Water Framework Directive will help secure the sustainable management of this small, but distinct component of Europe’s freshwater biodiversity.

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Walling, D.E., and Amos, C.M. 1999. Source, storage and mobilisation of fine sediment in a chalk stream system. Hydrological Processes 13(3): 323–340. Walling, D.E., and Owens, P.N. 2003. The role of overbank floodplain sedimentation in catchment contaminant budgets. Hydrobiologia 494: 83–91. Walling, D.E., and Quine, T.A. 1993. Using Chernobyl-derived fallout radionuclides to investigate the role of downstream conveyance losses in the suspended sediment budget of the River Severn, United Kingdom. Physical Geography 14: 239–253. Walling, D.E., Owens, P.N., and Leeks, G.J.L. 1998. The characteristics of overbank deposits associated with a major flood event in the catchment of the River Ouse, Yorkshire, UK. Catena 32: 309–331. Walling, D.E., Owens, P.N., Waterfall, B.D., Leeks, G.J.L., and Wass, P.D. 2000. The particle size characteristics of fluvial suspended sediment in the Humber and Tweed catchments, UK. Science of the Total Environment 251: 205–222. Walling, D.E., Owens, P.N., Carter, J., Leeks, G.J.L., Lewis, S., Meharg, A. A., and Wright, J. 2003. Storage of sediment-associated nutrients and contaminants in river channel and floodplain systems. Applied Geochemistry 18: 195–220. Ward, R.C. 1981. River systems and their river regimes. In: Lewin, J.L. (ed). British Rivers, Allen and Unwin, London, pp. 1–33. Ward, D. Holmes, N. and Jose, P. (eds). 1994. The New Rivers and Wildlife Handbook RSPB, Sandy 426 pp. Weatherley, N.S., and Ormerod, S.J. 1987. The impact of acidification on macroinvertebrate assemblages in welsh streams – towards an empirical model. Journal of Environment and Pollution 46: 223–240. Weatherley, N.S., Rogers, A.P., Goenaga, X., and Ormerod, S.J. 1990. The survival of early life stages of brown trout (Salmo trutta L.) in relation to aluminium specification in upland welsh streams. Aquatic Toxicology 17: 213–230. Weatherley, N.S., Jenkins, M.J., Evans, D.M. et al. 1995. Options for liming rivers to ameliorate acidity – a UK perspective. Water Soil Pollution 85: 1009–1014. Welton, J.S., Beaumont, W.R.C., and Ladle, M. 1999. Timing of migration and changes in age structure of Atlantic salmon, Salmo salar L., in the River Frome, a Dorest chalk stream, over a 24 year period. 1999. Fisheries Management and Ecology 6: 437–458. Werritty, A. 2002. Living with uncertainty: climate change, river flows and water resource management in Scotland. Science of the Total Environment 294(1–3): 29–40. Werritty, A. 2006. Sustainable flood management: oxymoron or new paradigm? Aera 38: 16–23. Werritty, A., and Leys, K.F. 2001. The sensitivity of Scottish rivers and upland valley floors to recent environmental change. Catena 42: 251–273. Werritty, A., and McEwan, L.J. 1997. Fluvial geomorphology of Scotland. In: Gregory, K.J. (ed). The Fluvial Geomorphology of Great Britain, Chapman and Hall, London, pp. 173–197.

Wheeler, A. 1977. Origin and distribution of freshwater fishes of British Isles. Journal of Biogeography 4(1): 1–24. White, E.M., and Knights, B. 1997. Dynamics of upstream migration of the European eel, Anguilla anguilla (L.), in the Rivers Severn and Avon, England, with special reference to the effects of man-made barriers. Fisheries Management and Ecology 4: 311–324. Whitehead, P.G., Howard, A., and Arulmani, C. 1997. Modelling algal growth and transport in rivers: a comparison of time series analysis, dynamic mass balance and neural network techniques. Hydrobiologia 349: 39–46. Wilkinson, S.N., Keller, R.J., and Rutherfurd, I.D. 2004. Phase-shifts in shear stress as an explanation for the maintenance of pool-riffle sequences. Earth Surface Processes Landforms 29: 737–753. Williams, A., and Archer, D. 2002. The use of historical flood information in the English Midlands to improve risk assessment. Hydrological Science Journal 47: 67–76. Williams, R., Burt, T.P., and Brighty, G. 2000. River water quality. In: Acreman, M. (ed). The Hydrology of the UK, Routledge, pp. 134–149. Wood, R., Handley, J., and Kidd, S. 1999. Sustainable development and institutional design: the example of the Mersey Basin Campaign. J Environmental Planning and Management 42: 341–354. Woodall, P.F. 1993. Dispersion and habitat preference of the water vole (Arvicola terrestris) on the River Thames. International Journal Mammalian Biology 58: 160–171. Woodcock, N. 1994. Geology and Environment in Great Britain and Ireland. Taylor and Francis 176 pp. Wright, J.F., Furse, M.T., and Moss, D. 1998. River classification using invertebrates: RIVPACS applications. Aquatic Conservation: Marine and Freshwater Ecosystems 8(4): 617–631. Wright, J.F., Winder, J.M., Gunn, R.J.M., Blackburn, J.H., Symes, K.L., and Clarke, R.T. 2000. Minor local effects of the River Thames power station on the macroinvertebrate fauna. Regulated River Research Management 16: 159–174. Yamaguchi, N., Gazzard, D., Scholey, G. et al. 2003. Concentrations and hazard assessment of PCBs, organochlorine pesticides and mercury in fish species from the upper Thames: River pollution and its potential effects on top predators. Chemosphere 50(3): 265–273. Younger, P.L., Mackay, R., and Connorton, B.J. 1993. Streambed sediment as a barrier to groundwater pollution – insights from fieldwork and modelling in the River Thames basin. Journal of the Institution of Water and Environmental Management 7(6): 577–585. Youngson, A.F., Jordan, W.F., and Hay, D.W. 1994. Homing of Atlantic salmon (Salmo salar L.) to a tributary spawning stream in a major river catchment. Aquaculture 121: 259–267.

FURTHER READING EA Environment Agency, 2003. Ouse Flood Risk Management Strategy – Executive Summary, 2003.

Chapter 11

Rivers of the Balkans Nikolaos Th. Skoulikidis

Alcibiades N. Economou

Konstantinos C. Gritzalis

Hellenic Centre for Marine Research, Institute of Inland Waters 46.7km AthensSounion Avenue, 190 13 Anavissos, Greece

Hellenic Centre for Marine Research, Institute of Inland Waters 46.7km AthensSounion Avenue, 190 13 Anavissos, Greece

Hellenic Centre for Marine Research, Institute of Inland Waters 46.7km AthensSounion Avenue, 190 13 Anavissos, Greece

Stamatis Zogaris Hellenic Centre for Marine Research, Institute of Inland Waters 46.7km AthensSounion Avenue, 190 13 Anavissos, Greece

11.1. 11.2. 11.3. 11.4.

11.5.

11.6.

11.7.

11.8.

11.9.

Introduction Historical Perspective Major Rivers and Tributaries Biogeographic Setting 11.4.1. General Aspects 11.4.2. Palaeogeography Physiography, Climate and Land Use 11.5.1. Geomorphology, Landform, Geology 11.5.2. Climate 11.5.3. Land Use Patterns and Human Pressures Hydrology and Biogeochemistry 11.6.1. Hydrology and Temperature 11.6.2. Biogeochemistry 11.6.3. General Characterization 11.6.4. Sediment Loads (Long-Term Trends) 11.6.5. Nutrients and Pollution Riparian and Aquatic Biodiversity 11.7.1. Riparian Vegetation 11.7.2. Lowland Riparian Woods 11.7.3. Deltaic Communities 11.7.4. Ichthyofauna 11.7.5. Macroinvertebrates 11.7.6. Reptiles and Amphibians 11.7.7. Birds 11.7.8. Mammals Management and Conservation 11.8.1. Economic Importance 11.8.2. Conservation and Restoration 11.8.3. Restoration Activities and Potential 11.8.4. Reference Conditions 11.8.5. EU Water Framework Directive Conclusion and Perspective

Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

Acknowledgements Reference

11.1. INTRODUCTION The Balkan Peninsula, or Balkans, is the historic and geographic name of southeastern Europe. The name is derived from the Balkan mountain range, the ancient Haemos, which divides Bulgaria and runs through eastern Serbia (in Turkish, Balkan means ‘a chain of wooded Mts’). The Balkans lay south of the rivers Save, Drava and Danube and is surrounded by the Adriatic and Ionian Seas in the west, the Mediterranean Sea in the south and the Aegean, Marmara and Black Seas in the east. The identity of the Balkans owes as much to its complex and often violent common history as well as to its spectacular mountainous topography.

11.2. HISTORICAL PERSPECTIVE Rivers and river gods played an important role in Greek mythology. Potamoi (Rivers) were thought to be offsprings of the Titan Okeanos (Ocean), son of Gaea (Earth) and Ouranos (Sky), and Tethys. The Balkan mountain ranges provide no barriers against human invasions from the north or east. Hence, the region has faced a long history of wars, rebellions, invasions and clashes between tribes, nations and empires – from prehistoric times to the recent Yugoslav war. The Balkan region has been inhabited permanently since the Middle Palaeolithic (Darlas 1995). It was the first area in Europe where farming cultures and livestock raising were established during the Neolithic era (Bailey 2000). In pre-classical and classical antiquity, the region was home to 421

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Greeks, Illyrians, Paeonians, Thracians and other ancient tribes. Later, the Roman Empire conquered most of the region but significant parts remained under classical Greek influence. At the end of the Roman Empire, migrating Slavs entered the Balkans. During the middle Ages, the Balkans became a battlefield between the Byzantine, Bulgarian and Serbian Empires. By the end of the 16th century, the Ottoman Empire emerged as the dominating force in the region. Because of frequent wars, the Balkans has remained the least developed area in Europe for the past 550 years. The Balkan nations started to regain independence in the 19th century. After World War II, until 1989, the Balkans (except Greece) was under communist regimes. In the 1990s, the region was hit by a civil war, with a death toll of 100 000 people, finally leading to independence of the former Yugoslavian states.

11.3. MAJOR RIVERS AND TRIBUTARIES This chapter covers 15 rivers that encompass the biogeographical diversity of the Balkan Peninsula (Figure 11.1). The Kamchia River flows into the Black Sea, all others into the Mediterranean; eight rivers enter the Aegean Sea (Evros, Nestos, Strymon, Axios, Aliakmon, Pinios, Sperchios and Evrotas), three the Adriatic Sea (Neretva, Drin and Aoos) and three the Ionian Sea (Arachthos, Acheloos and Alfeios). Six river basins are transboundary. The Drin (Drim) drains parts of Albania, Serbia, Montenegro, former Yugoslav Republic of Macedonia (FYR Macedonia) and Greece. For its relatively small size, it is among the most international rivers worldwide. The Neretva flows through Bosnia and Herzegovina and Croatia; the Evros (Maritsa, Meri¸c) basin is shared among Bulgaria, Greece and Turkey; the Strymon (Struma) and the Nestos (Mesta) are shared by Bulgaria and Greece, the Axios (Vardar) enters Greece from FYR Macedonia, while the Aoos (Vjose) flows from Greece towards Albania. The Kamchia is entirely located in Bulgaria, while the Aliakmon, Pinios, Sperchios, Arachthos, Acheloos, Alfeios and Evrotas are entirely in Greece. The catchment area of all 15 rivers totals 182 637 km2. Six river basins (Evros, Axios, Drin, Neretva, Strymon and Pinios) are considered as very large (>10 000 km2) and 9 as large (1000–10 000 km2). The Nestos, Drin, Neretva, Aoos and Arachthos drain mountainous catchments with mean altitudes >800 m asl, the remaining rivers drain mid-altitude (mean altitude: 300–800 m asl) catchments, with the Kamchia, Evros and Pinios having downstream lowland river sections. Most Balkan rivers form deltaic plains; some of them are wetlands of international importance. Table 11.1 summarizes the main physiographic characteristics of all catchments (Photos 11.1–11.10). The Neretva rises in Bosnia and Herzegovina (97.5% of its basin) and enters southern Croatia forming a large delta. The Basin contains the largest karstic river in the Dinaric

PART | I Rivers of Europe

Mts and is hydrologically connected with the Trebisnjica River. The Drin, the largest Albanian river, runs through a mountainous area towards the coast. It provides the third greatest river discharge in the European Mediterranean. The river has two main branches: the White Drin drains Serbia and Montenegro and the Black Drin originates from Lake Pespa (transboundary lake between FYR Macedonia, Albania and Greece) and Lake Ohrid (transboundary lake between FYR Macedonia and Albania). Before it enters the Adriatic Sea, the Buna River joins the Drin. The Buna drains Lake Shkodra (Shkadar), the largest Balkan lake (shared between Albania and Montenegro). The Aoos flows through an almost pristine mountainous landscape in NW Greece before it enters Albania (64% of the total basin). It forms a large delta. Its largest tributary is the transboundary Drino with a catchment area of 1320 km2 (80% located in Albania). The Kamchia runs through a wide basin in eastern Bulgaria and empties into the Black Sea. The river has two main branches, the Golyama–Kamchia in the north and the Luda–Kamchia in the south. The Evros is the largest river basin in the Balkans. It is shared between Bulgaria (66.4%), Turkey (27.2%) and Greece (6.4%). It flows through Bulgaria, then forms the borderline with Greece and Turkey and finally creates a large delta in the Aegean Sea. The main tributaries are the Tundja (7980 km2, 350 km) in Bulgaria, the Arda (5200 km2, 240 km) in Bulgaria with a small part in to Greece, and the Ergene (10 200 km2, 280 km) in Thracian Turkey. The Nestos is a highland river (mean altitude: 1006 m asl). It flows through Bulgaria (60% of the basin area) and Greece and enters the Aegean Sea forming an extensive delta. The main tributary is Dospatis (Dospatska) (236 km2) that emerges in Bulgaria and joins the Nestos in Greece. The Strymon basin is mainly located in Bulgaria (50%) and in Greece (37%), with tributaries draining small parts of FYR Macedonia (9%) and Serbia (4%). After entering Greece, it passes through the semi-natural Kerkini Lake and discharges into the Aegean Sea (Strymonikos Gulf). Major tributaries along the Bulgarian section are the Strumeshnitsa (1892 km2) and the Treklyanska (515 km2), while the Aggitis (2234 km2) is the main tributary in Greece. The Axios, located in the central Balkan Peninsula, drains the second largest catchment in the Balkans. The river drains 83% of FYR Macedonia and small parts of Bulgaria, Serbia and Greece before it enters the Aegean Sea (Thermaikos Gulf). Major tributaries are the Crna (5890 km2) and the Brejalinica (4307 km2). The river is hydrologically connected to Lake Doirani (Dojran), shared between Greece and FYR Macedonia. The Aliakmon, the longest river in Greece, receives overflow waters from Lake Kastoria. Its main upstream

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FIGURE 11.1 Digital elevation model (upper panel) and drainage network (lower panel) of Rivers of the Balkans.

tributary is the Venetikos (821 km2). Downstream, the tributaries Almopeos and Edesseos, connected through a long irrigation canal (named T66) (2100 km2), join the river that finally discharges into the Thermaikos Gulf forming a joint delta with Axios. The Pinios in central Greece drains the seemingly vast Thessaly plain and flows into the Thermaikos Gulf. Several permanent tributaries contribute to its runoff of which Titar-

issios (1750 km2), Onochonos (1575 km2) and Enipeas (1075 km2) are the largest. The Sperchios basin, south of the Pinios catchment, is the smallest of the examined rivers. It flows to the Maliakos Gulf (Aegean Sea) where it creates a rapidly expanding delta. The Arachthos drains a small mountainous basin located in western Greece. It outflows to the Amvrakikos Gulf (Ionian Sea) creating a large delta with extensive lagoons.

TABLE 11.1 General characterization of the Rivers of the Balkans Kamchia Neretva Drin

Evros

Nestos Strymon Axios

Aliakmon Pinios

Sperchios Aoos

Arachthos Acheloos Alfeios Evrotas

Mean catchment elevation (m) 311 848 868 400 1006 715 747 771 431 685 849 807 5338 13 311 20 585 53 078 6265 17 087 24 604 8880 10 743 1493 6813 1907 Catchment area (km2) River length 245 255 285 550 246 410 380 310 257 82 260 105 0.607 11.9 11.4 (21.4a) 7.0 2.076 4.31 3.62 2.7 2.55 0.703 5.55 2.08 Discharge (km3/year) 5.2 28.3 17.5 (26.3a) !4.2 10.5 8.0 6.7b 9.6 7.5 14.9 25.8 34.6 Specific discharge (L/s km2) Mean annual precipitation (cm) 57.7 117.7 105.3 62.9 64.8 60.8 62.9 67.1 62.4 64.4 100.2 91.2 11.1 9.2 8.9 11.2 9.6 10.1 9.9 10.6 13.3 13.2 11.8 12.9 Mean air temperature ( C) Number of ecological regions 2 2 4 4 3 3 4 3 2 2 2 3 Dominant (25%) 9 27; 39 9; 53 9; 58 9; 58 1; 9 9 53 1 1; 53 39; 53 39; 53 ecological regions Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparse vegetation Wetland Freshwater bodies

4.5 40.6 3.4 44.7 5.8 0.0 0.0 1.0

0.7 16.3 8.3 29.2 40.2 3.0 0.4 0.7

0.7 21.7 4.3 36.6 26.2 5.2 0.8 4.5

Protected area (% of catchment)

0.2

0.9

5.0

Water stress (1–3) 1995 2070

2.7 2.8

1.1 1.2

1.1 1.2

Fragmentation (1–3) 3 Number of large dams (>15 m) 3 Native fish species 38 Nonnative fish species 3 Large cities (>100 000) 0 48 Human population density (people/km2) Annual gross domestic 1800 product ($ per person)

2.4 34.5 2.0 35.8 22.8 1.4 0.3 0.8

1.4 34.0 8.1 32.1 23.4 0.3 0.2 0.5

1.1 39.3 0.4 30.4 25.4 1.6 0.4 1.4

2.1 51.1 1.6 16.9 32.8 1.2 0.1 0.2

1.3 31.4 0.2 32.4 33.7 0.8 0.1 0.1

1.0 16.0 0.5 35.7 39.3 6.9 0.1 0.5

0.6 19.3 0.0 24.7 30.4 3.5 0.2 1.3

0.7 22.2 0.0 26.3 43.0 3.3 0.3 4.2

0.8 38.6 0.9 17.2 39.9 2.1 0.0 0.5

0.7 34.6 0.0 15.8 48.0 0.8 0.0 0.1

1.1c

5.7

7.3

1.8

13.5

13.0

19.5

15.6

21.7

17.2

7.4

18.9

2.8 2.9

2.3 2.3

2.8 2.9

2.9 2.9

2.7 2.7

2.9 2.9

2.1 2.1

1.7 1.7

1.8 1.9

2.2 2.2

1.8 1.8

1.0 1.0

3 5 56 16 3 98

2 21 32 7 3 69

3 4c 21 8 0 33

3 4c 36 7 0 57

2 17 36 5 1 83

3 3 24 9 0 36

2 1 29 1 1 54

1 0 11 4 0 28

2 1 17 1 0 44

3 2 13 3 0 28

3 5 22 15 0 27

2014

2562

2922

6710

6636

3229

13 227

12 350

15 096

4407

9265

11 978

With Buna. Natural. c At least. For data sources and detailed explanation see Chapter 1. b

690 654 3637 2418 112 90 2.1 0.76 18.3 10.0 76.2 73.3 13.9 14.0 2 2 1 1

1.2 18.2 0.8 56.4 20.4 1.5 0.5 1.0

3 5 31 12 1 38

Land use data are approximate values. a

2.7 53.4 5.1 26.7 10.1 0.2 0.7 1.1

744 6478 255 4.38 21.4 80.8 13.5 2 1; 53

2 1 10 8 0 26

1 0 5 1 0 30

10 836 11 390

Chapter | 11 Rivers of the Balkans

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PHOTO 11.1 The Aliakmon’s Ilarion Gorge, near Kozani, Northern Greece; one of the largest deep canyons in Greece destined to be flooded by new hydropower dam developments (S. Zogaris).

The Acheloos, also situated in western Greece, has the highest runoff among all Greek rivers. The upstream and middle parts of the river receive numerous permanent tributaries with Megdovas (Tavropos) being the largest (830 km2). Close to its delta, four natural lakes (Trichonis, the largest and deepest Greek lake, Lysimachia, Ozeros and Amvrakia) are formed that maintain a present

or past connection with Acheloos. The river empties into the Ionian Sea forming a delta associated with extensive lagoons. The Alfeios, with its main tributary Ladon (750 km2), drains much of the western Peloponnese. The Evrotas is the southernmost basin of the Balkan mainland and empties into the Laconikos Gulf. PHOTO 11.2 Evrotas upstream drying out (N. Skoulikidis).

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PHOTO 11.3 One of western Greece’s most extensive braided river reaches on the mid section of the Acheloos river (S. Zogaris).

11.4. BIOGEOGRAPHIC SETTING 11.4.1. General Aspects The Balkan Peninsula is situated at the biogeographical crossroad between continental Europe, western Asia and the Mediterranean and Black Seas. It is characterized by a rich aquatic fauna and flora with a high proportion of en-

demic species. High biodiversity is a consequence of the region’s geologic and palaeoclimatic history as well as the geophysical variety of inland water bodies (Griffiths et al. 2004). During the Pleistocene, glaciers were restricted to mountain summits. The lowland areas provided refugia for the continental freshwater fauna and flora. Despite their rather small size, the Balkan rivers and streams host highly

PHOTO 11.4 The Aoos river near the Greek-Albanian border naturally constrained in conglomerate bedrock (S. Zogairs).

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PHOTO 11.5 The Arachthos river at Tzari Bridge upstream of the Pournari Reservoir (S. Zogaris).

diverse freshwater communities. The high degree of endemism, compared to the rest of Europe, is perhaps the most remarkable feature of the Balkans. For example Greece contains the largest number of freshwater fish species and the highest proportion of endemic fish in Europe (Crivelli et al. 1995).

The relative isolation of river basins through geological history has forged distinctive biogeographic boundaries and a complex historical sequence of biotic isolation and fragmentation (e.g. interruption of dispersal routes). During the formation of the mid-Aegean trench (9 Ma BP), the peninsula became separated from Asia Minor by the contiguous Aegean Sea (Dermitzakis & Papanikolaou 1981). One of the

PHOTO 11.6 The Evrotas river, flanked by native white poplars, remnants of extensive riparian forests (S. Zogaris).

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PHOTO 11.7 The Mesochora Dam (not yet filled) in the Upper Acheloos river; one of the largest and most controversial river diversion projects in Mediterranean Europe (S. Zogairs).

most distinctive long-standing biogeographical barriers is the Dinarides–Hellenides mountain chain that separates the western and eastern biotic assemblages. Phylogenetic studies confirm a west–east split of the Balkan’s aquatic and terrestrial biota. Even widespread species, such as the Pond Turtle (Emys orbicularis) and common reptiles, are split into western and eastern phylogroups (Schmitt 2007). The isolation of the western Balkan river basins since Miocene times has favoured a rich endemic aquatic fauna (Bianco 1986; Gasc 1997). Further, there are marked latitudinal gradients in species composition and richness. Species richness increases from south to north while the proportion of endemic species increases from north to south. The catchments south of the Aoos River are depauperate compared to the more northern basins. However, almost all primary freshwater fishes as well as several amphibians (e.g. Epirus frog Rana epiroticus) and reptiles are endemic to this area (Arnold & Ovenden 2002). The eastern part of the Balkan Peninsula is richer in aquatic biota, although the proportion of endemic species is lower. This area is influenced by adjacent biogeographic

regions, especially the Lower Danube-Black Sea region. In addition, climatic factors contribute to the generation of biogeographic differences. The eastern Balkans exhibit a continental and dry climate with harsh and cold winters. Some parts are biologically ‘isolated’ through local xeric climate conditions caused by rain shadow effects. Southeast Greece, a rather small part of the peninsula with low precipitation and dry summers, contains small and often intermittent rivers. They harbour fish and benthic invertebrate communities rich in endemic species (Economidis & Banarescu 1991). An important geological feature of the Balkans, with strong biogeographic implications, is the high proportion of karstic subterranean rivers, especially in the western part. They contain remarkable subterranean communities. This area is a ‘hot spot’ of hypogean biodiversity with unique life forms such as the Olm Proteus anguinusin in the Neretva. The Aggitis River tributary at the Strymon emerges from a vast system of underground caverns that provides habitat for the Thracian barbel Barbus cyclolepis and the Stone

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PHOTO 11.8 The Yeropotamos tributary of the AxiosVardar, on Mount Voras, Northern Greece (S. Zogaris).

crayfish Austropotamobium torrentium (Koutrakis et al. 2003, 2007). A definitive biogeographic characterization of the Balkans remains difficult because underlying biogeographic patterns are interrupted by several idiosyncrasies and inherent river basin attributes (numerous lakes, peninsular effects). There exist major discrepancies among researchers on how to define and delineate biogeographic regions for terrestrial, aquatic, or semi-aquatic biota in this region (Illies 1978; Banarescu 2004). Since aquatic biodiversity has not been well inventoried in many parts of the Balkans, satisfactory base-line knowledge of species distributions and the validity of the systematic taxonomy are far from complete.

11.4.2. Palaeogeography The Balkan Peninsula has developed over the course of several orogenic cycles from the Late Palaeozoic to the present following the collision between the Eurasian and African tectonic plates. The current orographic regime of

the Balkans is the result of the Alpine orogenesis during the past 250 million years (from late Triassic to the Quaternary). The Alpine orogenesis began with the rifting of Pangea, the development of tectonic rift valleys, and the advance of the Tethys Sea between Eurasia and Africa–Arabia. Widespread carbonate marine sedimentation (limestones, dolomites and marls) continued through the Triassic and Cretaceous. During the late Jurassic and early Cretaceous significant orogenic activities caused the break up of the continental crust within the Tethys Sea, where ophiolites, situated today along two parallel belts, have been emplaced. A Cretaceous to Eocene compressive deformation that migrated from the east to the west of the Balkans was followed by the generation of deep rift valleys, which were filled up by flysch and molasse (Eocene–Miocene, younging from east to west). During the late Palaeocene – late Eocene (50–35 Ma BP), large parts of the northern and eastern Balkans had already emerged and in the mid-late Eocene the Kamchia foredeep developed (Georgiev 2001). By the end of the Eocene the western part of the Tethys Sea was reduced to the

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PHOTO 11.9 One of the largest lowland Oriental Plane riparian woodlands in southern Greece clothes parts of the mid Evrotas river, in this summer-intermittent reach south of Sparta (S. Zogaris).

Mediterranean Sea. During the Eocene–Oligocene transition (32 Ma BP) the Paratethys was formed to the north. The gradual uplift of the Balkan and the Dinarides–Hellenides Mts separated the Balkan basins from the central European and the eastern and western Balkan basins. In the lower Miocene (23 Ma BP) the Pindic and Pelagonian Cordilleras, together with the Rhodopes, created large landmasses interrupted by seas. Deep sea carbonate and flysch sedimentation continued westward and shallow marine molassic deposits laid down between the mountain ranges. About 18 Ma BP, significant tectonic movements uplifted the whole Balkan region and huge napes were emplaced in most Alpine chains. By that time, the Balkans, the Aegean Sea and Asia Minor formed a large continuous landmass (Dermitzakis & Papanikolaou 1981). During the late Tortoninan (c. 8 Ma BP), widespread extensional tectonics caused intense fracturing of the central continental part, the invasion of the sea and the connection of the Mediterranean with the Black and Caspian Seas, both remnants of the Parathethys. In the mid-late Miocene, the initial rift structures of most Balkan rivers, for example the

Strymon, Nestos, Axios, Neretva, Aliakmon and Acheloos, were formed along large faults, together with the rifts of lakes Ohrid, Prespa and Doirani (Tzankov et al. 1996; Karistineos & Ioakim 1989; Medzida et al. 2006; Hinsbergen 2004; Lykoudi & Angelaki 2004). In the late Miocene, the lower part of the Strymon basin alternated between freshwater, lacustrine and marine conditions and was linked with Nestos through the Serres and Drama basins (Zagorchev et al. 2002). At the end of the Miocene (Messinian, 5.5 Ma BP), the Mediterranean Sea closed and almost dried, large volumes of evaporites precipitated in a series of vast basins (‘Messinian Salinity Crisis’) and then it was refilled with freshwaters from the Paratethys. This event may have facilitated the dispersal of freshwater organisms around a Mediterranean circum (Bianco 1990). During the Pliocene (5–2 Ma BP), the majority of the Balkan rivers started a rejuvenating phase forming wide and deep mother valleys, and large amounts of fluvial sediments were deposited (Psilovikos & Ioannou 1993). At this time, the palaeo-Striama river (Evros tributary) joined the palaeoTundja river (Tzankov et al. 1996). At the end of the

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Chapter | 11 Rivers of the Balkans

PHOTO 11.10 Kalaritikos, the main Arachthos River tributary (N. Skoulikidis).

Pliocene, rapid climate changes caused the disappearance of savannas and associated mammals and the development of steppic floras (Koufos et al. 2005). In the late Pliocene– Pleistocene, extensional dynamics formed the Amvrakikos Gulf, which was connected with Sperchios graben and the Gulf of Evia (Hinsbergen 2004), as well as the Alfeios and Evrotas basins (Hinsbergen et al. 2005), and the present day contours of the Balkan area were shaped. At the Plio-Quaternary boundary, a major marine transgression connected the Mediterranean with the Black Sea, the Caspian Sea and Lake Aral (Paluska & Degens 1978). The Quaternary period was marked by alternating largescale glaciations interfered by short warm intervals. In the Pleistocene, the Axios found its way to the sea, and thus other related palaeo-lakes were drained. Today, only Lakes Ohrid, Prespa and Doirani remain as remnants of this extensive system of lakes (Dumurdzanov et al. 2004). At 1.5 Ma BP, the palaeo-Evros, which emptied in the Marmara Sea through the Ergene River, was diverted to the Aegean Sea due to the uplift of the northern margin of Marmara Sea (Okay & Okay 2002). The Acheloos opened a valley through the Agrinio Basin, formerly filled by a large lake, remnants of which are four contemporary lakes, and emptied into the sea (Psilovikos et al. 1995). The same situation faced Pinios, formerly a Pleistocene lake, finding its way to the sea in the Holocene when the Tempi Gorge was opened (Leivaditis 1991). During the moist and cool conditions in the Upper Pleistocene–Holocene (130 000–18 000 years BP), glaciers covered the highest mountains, and rivers faced a second stage of rejuvenation opening steep and incised valleys (Psilovikos & Ioannou 1993). The rivers shortened,

alternating between meandering and braided styles, and propagated deltas, depending on glacial/interglacial cycles. At the last glacial maximum (21 500 years BP), when the sea level was 120 m lower than today, extensive shelf areas were exposed at the northern Aegean, the Adriatic and parts of the Ionian Sea. As a result, river confluences enabled dispersion and faunal exchanges. The Marmara Sea and part of the Amvrakikos Gulf were freshwater lakes. The Arachthos River and its tributary Louros (which today is a separate river) drained across the Amvrakikos Gulf, exhibited a braided style, and formed a delta in the Ionian Sea (Piper et al. 1988). The Thermaikos Gulf was a large alluvial plain drained by the extensions of Aliakmon and Pinios, then tributaries of the Axios palaeo-river (Lykousis et al. 2005). The Nestos and Strymon Rivers formed a joined delta in the Gulf of Kavala (Perissoratis & Conispoliatis 2003). With the retreat of the ice-sheets 18 000 BP, the Black Sea lacustrine system drained into the Mediterranean (Economidis & Banarescu 1991). Ancient flood myths may be based on the rising Mediterranean that suddenly broke through the Bosporus inundating the farmlands of the Black Sea about 5500 years BP. At that time, the sea level stabilized, while climate and tectonic movements, along with sediment deposition and deltaic formation, controlled the present shape of coastal areas.

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11.5. PHYSIOGRAPHY, CLIMATE AND LAND USE 11.5.1. Geomorphology, Landform, Geology The Balkan Peninsula is a rough Alpidic orogen of the Mediterranean type, with large thrust sheets, ophiolites, repeated events of metamorphism and related granitic intrusions, and sedimentation of thick carbonate, flysch and molasse deposits. With the exception of the Thracian plateau, the Balkans are a mountainous region geotectonically divided in Internal and External Balkanides. The External Balkanides extend along the Adriatic and Ionian coasts and are bound to the east by the NNW–SSE running Dinarides–Hellenides mountain range, the backbone of the western Balkans. They were dominated by the Alpine orogenesis and reveal a rather simple geotectonic structure made up of sedimentary sequences. The Internal Balkanides east of this mountain range were affected by even older orogenic movements and reveal a complex geotectonic structure dominated by metamorphic massifs of the Pre-alpine age (Carrigan et al. 2003), plutonic and volcanic intrusions and ophiolite suture zones. There are two ophiolite zones; the predominant one extends 1000 km along the Dinarides–Hellenides mountain range (Dinaric Mts to Mount Orthrys in Greece), and the second one extends eastwards along the Axios basin. Two shorter ranges climb in the ophiolite zones, running across FYR Macedonia and Greece, where Mt Olympos peaks at 2917 m asl; the second highest point in the Peninsula. The impressive chain of the Rhodopes (with Mount Rila, 2925 m asl) traverses the centre of the Peninsula, throwing out spurs towards the Black Sea and the Aegean. To the north, the 600 km long Balkan Mts, an elongation of the Carpathians, run from west to east across Bulgaria. Due to its relatively young geology, the Balkan Peninsula is characterized by highly fragmented hydrographic networks and is drained by many small and medium-sized mountainous rivers. Rivers run through steep, narrow mountain valleys, have flashy flow and sediment regimes, and descend abruptly to the coast. However, there are a few larger low-gradient rivers crossing the Balkans along prevailing thrust belts and related rift valleys that form extensive flood and deltaic plains. The Dinarides–Hellenides mountain range forms a series of nearly parallel ridges, plateaus and depressions, dissected by steep-sided valleys. A number of rivers (Neretva, Aoos, Arachthos, Acheloos, Alfeios, Evrotas) that emerge along the western slope of this mountain range lie exclusively or almost exclusively in the External Balkanides. Their basins consist of Mesozoic-Palaeogene carbonates covered by Palaeogene flysch. Magmatic and metamorphic rocks are absent in the basins of Neretva, Acheloos and Alfeios, whereas the headwaters of Arachthos and Aoos drain small ophiolite outcrops and the mountainous surroundings of Evrotas basin include small portions of schists.

PART | I Rivers of Europe

The Neretva is the largest river in the Dinaric Mts flowing for almost 250 km through a karstic area. It emerges at about 1100 m asl at the base of the Zelengora Mts (2032 m asl). The headwaters are dominated by Triassic and Jurassic limestone and dolomite. The river flows through a sequence of bedrock canyons and plains. In the last 30 km the river widens and branches, spreading into a 200 km2 deltaic plain. The Neretva Delta, one of the largest wetlands along the Dalmatian coast, includes small shallow karstic crypto-depression lakes, marshes and lagoons, fringed by limestone outcrops. The Aoos River (Photo 11.4) originates at the base of the Pindos Mts (Mavrovouni peak 2159 m asl) and flows through deep gorges and steep ravines. The Voidomatis tributary (384 km2), a partially intermittent river with a steep gradient (1.6%), flows through the renowned Vikos Canyon and joins the Aoos in the Konitsa plateau just upstream of its confluence with the Sarandaporos tributary (870 km2). The Gamila summit, an imposing alpine ridge with enormous vertical slopes, is one of the few glacial landscapes in Greece. Here, the unique alpine lake Drakolimni (Dragonlake) is located at an altitude of 2050 m asl. Flowing in a SE– NW direction, the Aoos is joined by the tributaries Drino, Zagori and B€enc€e. The lower meandering river channel is on average 25 m wide. The delta, with a well-defined cuspate shape, hosts the Natra Lagoon (33 km2). Carbonates (mainly limestones) overlain by flysch, cover most of the catchment. Recent deposits include Messinian evaporites and Pliocene molasses that outcrop between alluvial sediments. The narrow Arachthos basin (Photo 11.5) drains the Pindos Mountain range, with main springs in the Tzoumerka (2429 m asl) and Lakmos (2295 m asl) Mts. A spectacular gorge (30 km long) spans between the Tzoumerka and Xerovouni Mts. Among the numerous headwater tributaries, the Kalaritikos (Photo 11.10) forms two magnificent gorges south of Mt Lakmos. The Arachthos empties into the Amvrakikos Gulf, 30 km east of the Louros river mouth. The unique double-delta formation extends over 109 km2 (350 km2 with Louros delta), creating Greece’s largest coastal reed-swamp and saltmarsh system fringed by coastal lagoons known as the Amvrakikos wetlands. The basin primarily consists of flysch (68% of the basin), while limestones and dolomites cover the western and northeastern parts (23%). Small ophiolite outcrops impinge on the northern part of the basin, while alluvial sediments cover the river valley and delta. The Acheloos (Photos 11.3 and 11.7) starts at 1700 m asl and drains the rugged southern Pindos mountain range. The river enters the Agrinio plain where the average width of the channel is 25 m with a maximum of 90 m in the deltaic area. Water depth is up to 7 m in the narrow gorges and 1–2 m in the delta section. The large lobate-type delta covers 270 km2 and includes two large lagoons, Mesolonghi and Aetoliko. The bedrock consists of flysch (48% of the basin) and limestone (32%), while the valleys and the delta are covered by lacustrine Pliocene and alluvial sediments(20%). Small outcrops of Triassic evaporites appear in the lower basin.

Chapter | 11 Rivers of the Balkans

The Alfeios River starts at 1800 m asl at the Taygetos Mt and outflows into the Kyparissiakos Gulf. The surrounding Mts reach up to 2338 m asl (Mt Menalo). The upper Alfeios drains the Megalopolis plateau where lignite ores are enclosed. The riverbed is composed of gravel and sand, having a mean valley slope of 0.37%. Sediments from the Alfeios River contribute to the longest coastal sand dune system in Greece. The arcuate-oblique delta type covers 113 km2. The basin is formed by karstic limestones while the lowlands are covered by Pliocene (marine), Pleistocene (lacustrine and terrestrial) and alluvial sediments, underlain by Triassic evaporites. The Evrotas (Photos 11.6 and 11.9) traverses a lowgradient narrow plain bound by the steep mountain ranges of Taygetos (west, 2407 m asl) and Parnon (east, 1935 m asl). The river originates from the Taygetos Mt, near the springs of Alfeios River and flows southwards through the Laconia basin. It then crosses the Vrodamas limestone gorge and discharges into the Laconikos Gulf, where it creates a small (53 km2) arcuate-lobate delta. The mountainous area of the basin is formed by limestones (42% of the basin) and flysch (29%). The lower parts are covered by marine Pliocene and alluvial sediments (28%). The Drin, Aliakmon, Pinios and Sperchios Rivers flow from the eastern flanks of the Dinarides–Hellenides mountain range and are (except the lower Drin) within the Internal Balkanides. They drain ophiolites, acid metamorphic rocks (gneisses, micaschists, amphibolites and phyllites), granitoid intrusives and Mesozoic carbonates. The Aliakmon, Pinios and Sperchios Rivers emerge from the eastern slope of the Pindos range and flow eastwards. Extended Tertiary (Eocene–Miocene) molassic sediments of the Meso-Hellenic Trough (Aliakmon, Pinios) and Palaeogene flysch (Pinios, Sperchios) dominate their basins. The Black Drin starts from the unique Prespa and Ohrid Lakes and flows NNW–SSE along a rift valley fringed by the steep forested Sar Mts (up to 2500 m asl). Its drainage area includes mafic/ultramafic rocks (Midrita ophiolite belt with important Cr, Fe and Ni ores), granites, volcanic and volcano-sedimentary series. The White Drin mainly drains Neogene lacustrine and marine deposits of the Kosovo plateau and meets the main branch of the Drin in Albania. The lower basin is formed by Triassic-Cretaceous limestones, flysch/ molasse and recent deposits. The river forms a delta with coastal lagoons. The Aliakmon (Photo 11.1) emerges in the Pindos Mts (Mt Gramos, 2520 m asl, is the highest peak). The river first drains a plain, where it receives water from Lake Kastoria and Venetikos-tributary. Then a section with reservoirs follows and downstream, the Almopeos and Edesseos tributaries enter in the Imathia plain though the T66-channel. Finally, the river forms a 120 km2 Delta. The northern and southern basin consists of metamorphic and acid igneous rocks (14.5% of the basin) and ophiolites (9.2%), overlain by Triassic limestones (15.7%). The western basin is covered by molassic

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deposits (29.6%). Neogene-Quaternary terrestrial, lacustrine and marine sediments (31%) cover the lowlands. The Pinios surrounded by high mountains (Pindos, Kamvounia, Pieria, Olympos, Ossa and Orthrys), drains the vast Thessaly plain, a former Pleistocene lake. Downstream of the confluence with the Malakasiotikos, it becomes a lowland meandering river. Low mountains (693 m asl) divide the plain into a western and eastern part (Trikala and Larisa basins). Within the Trikala basin, the river widens up to 1.5 km forming a braided channel. Between Mts Olympos and Ossa, it passes through the Tempe Gorge and discharges into the Thermaikos Gulf forming a 69 km2 radial-shaped delta. Metamorphic and acid igneous rocks outcrop along the northern and eastern mountainous boundary (17.5% of the basin). Mesozoic sediments of Triassic and Cretaceous age (limestones, dolomites and cherts) are mainly found on the Pindos range (14.7%). Ophiolites (6.2%), underling these sediments, outcrop in erosional zones. Flysch and molasse (15.8%) cover the western basin, where conglomerate molassic outcrops form impressive landscape features. The Thessaly plain is filled with Neogene and Quaternary fluvio-lacustrine deposits, which cover almost the half of the basin (47.9%). The Sperchios becomes a river at 700 m asl at the foot of Tymfristos Mt (2327 m asl). The basin belongs to a narrow W–E orientated rift valley. The lower section of the river is meandering and finally ends in the shallow muddy Maliakos Gulf forming a 196 km2 lobate delta. The western basin is covered by flysch (48% of the basin), which supplies the riverbed with gravel. Mesozoic dolomites and limestones (16%) extend in the SE and NE basin. In the N and NE portion (Mt Othrys), ophiolite complexes with Cr-ores cover 12% of the basin. The valleys are filled by thick alluvial deposits (24%). The Axios basin starts at 750 m asl at the western slopes of Crna Gora Mountain (2062 m asl) and is bound to the north and west by the Sar Planina Mountain range (2748 m asl) and to the east by the ‘Surrounding’ Mountain Ranges (2252 m asl). In the headwaters, it receives the Treska-tributary (2068 km2) before entering the SkopjeVeles plains. The tributaries Pcinja (2840 km2), Bregalnica and Crna join the river before it enters Greece through the narrow Klisura Valley. Finally, it forms a wide bird-foot type delta in the Thermaikos Gulf. The delta is also fed by the Aliakmon, Loudias and Gallikos Rivers forming the most extensive wetland area in Greece (area: 600 km2). The mountainous areas consist of metamorphic rocks, granitoids and volcanic formations (43.5% of the basin), Mesozoic limestones (11.4%) and ophiolites (7.7%). Igneous and volcanic rocks are associated with mixed sulphides and are important sources of Pb–Zn ores. Flysch and molasse cover 5.6% of the basin. Lacustrine and terrestrial Neogene and alluvial sediments (31.9%) fill the river valleys and the delta. The Kamchia River emerges from the eastern flanks of the Balkan Mts and flows into the Black Sea. To the south, the Evros basin drains the large Thracian plain, bound to the south by the Rila-Rhodope Mts. The southern flanks of this

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massif are drained by the Nestos and Strymon rivers bordered by Pirin Mt. The Kamchia is a low-lying river emptying into the Black Sea 40 km south of the city of Varna. The basin is filled with Mesozoic-Palaeocene flysch and some Eocene molasse overlaying the metamorphic and intrusive rocks, and is marked by Late Cretaceous andesitic volcanism. The lower basin is covered by Pliocene and Quaternary sediments. The Strymon basin, confined to the north by Mt Vitosha, starts at the base of Mancho peak (2378 m asl). Mt Rila (2925 m asl) and Pirin (2914 m asl) form the eastern and southeastern catchment boundaries. Initially, the river flows through a mountainous terrain receiving a number of N–S flowing tributaries (Konska, Svetia and Treklyanska) and then turns to the south through a broad valley. It enters Greece through the Rupel narrows, crosses the vast Serres plain forming the semi-natural Lake Kerkini and then receives the inflows of Aggitis karstic river. The river empties in the Strymonikos Gulf forming a small delta (9 km2). A large portion of the basin (41.6%) is formed by acid metamorphic and plutonic rocks, that is schists, amphibolites, gneiss and ultrabasics, intruded by granitoid and Paleogene volcanic bodies (rhyolites, rhyodacites). Triassic carbonate rocks (marbles, limestones, dolomites) are restricted to the northern basin, while Palaeozoic marbles are found in the SE (mainly Aggitis basin). Carbonates cover 17.1% of the basin. Flysch deposits (5.2%) are restricted to the headwaters. The river valleys and the Serres–Drama plains are filled with terrestrial, lacustrine and marine Neogene and Quaternary sediments (33.7%). The Nestos starts at the eastern slope of Rila Mt and forms a narrow mountainous basin, confined by the Strymon catchment to the west, the Rhodope Mts to the east and the Gulf of Kavala to the south. After the confluence of Bijala Mesta and Cherna Mesta, the river flows through a rift plain between Mts Pirin and Rhodope, with their 109 small alpine glacial lakes and tarns. The headwater regions contain impressive geomorphologic structures, canyons and steep forested rocky gorges. Acid silicate rocks cover 68% of the basin. Metamorphic formations (gneisses, amphibolites, mica schists and marbles), Quaternary volcanics, with a variety of base and precious metals mineralization and geothermal fields, and granite plutons shape the upper and middle parts. Just before its delta, between Stavroupolis and Toxotes, the river cuts through the extensive karstic marble formation of Lekani Mt. Downstream of this impressive gorge, the river spreads over a large flat deltaic area covered by lacustrine and terrestrial Neogene-Quaternary deposits (18% of the basin area). Carbonate formations (13%), together with limited Eocene–Oligocene molassic sediments, mainly occur in the southern part. The 434 km2 arcuate delta consists of a mosaic of sand dunes, freshwater lakes and ponds, coastal lagoons and saltmarshes, and the relicts of the famous alluvial forest Kotza Orman.

PART | I Rivers of Europe

The Evros is a large lowland river draining the Thracian plain. It also emerges at the Rila Mt near the summit of Musala and runs first through a steep glacier valley and then east and southeast fringed by the Balkan and Rhodope Mts before crossing the Thracian plain. It forms the BulgarianGreek border over a short distance before it flows along the Greek-Turkish border to the Aegean Sea. At 140 Rkm (Parvomai) it reaches 200 m width and 5 m depth and has an unstable riverbed. In Greece, the river width reaches 150 m. The 188 km2 lobate-shaped delta contains two major lakes associated with swamps and extensive coastal lagoons. The Tundja tributary starts in Stara Planina Mts and flows through a low elevation plain (average basin altitude: 386 m asl) before entering the Evros at Edirne. The Arda river, flowing through a medium elevation plain (648 m asl), joins the main stem in Greece. The Ergene tributary, flowing through the East Thrace (Turkey) plain, joins the main channel upstream of the delta. Acid silicate rocks make up 37.8% of the basin. The mountainous parts consist mainly of metamorphic formations, granites and carbonates. Volcanic intrusives (andesites, tuffs, monzonites, diorites) occur locally and along the Maritsa fault. Important hydrothermal metallogenic zones rich in Au, Ag, Cu, Pb and Zn ores extend along the Balkan Mts and in the eastern basin. The Thracian plain is covered by Pliocene (including lignite ores) and Quaternary sediments. Lacustrine and terrestrial Neogene and Quaternary sediments are the dominant basin formation (41.9%). Carbonate rocks comprise 10% of the basin. Palaeogene molassic deposits (9.4%) mainly cover the Thracian plain.

11.5.2. Climate Altitudinal gradients, a diverse mountainous relief, and the influence of the Mediterranean and Black Seas create diverse climatic conditions in the Balkan Peninsula. In general, the climate is characterized by a distinct bimodal seasonality and a strong N–S gradient, with increasing temperature and decreasing precipitation towards the S–SE (Table 11.1). The S–SE Balkans suffers from prolonged droughts. In the past decades, average precipitation decreased and the frequency and severity of droughts increased (World Bank 2003). In 2007, during prolonged summer heat waves, heavy wildfires destroyed thousands of km2 of Balkan forests. The Adriatic and Ionian basins receive a much higher precipitation compared to the eastern Balkans. The Dinaric Alps exhibit a moderate continental climate with cold winters but warm and humid summers, while the higher Mts have a subalpine climate with extended periods of snow cover. Therefore, many rivers show steep climatic gradients along their course. The mean annual air temperature in the Neretva basin is 9.2 C but reaches >16 C downstream of Mostar. The Drin basin has the lowest average air temperature (8.9 C) of all examined basins, although its downstream section exhibits a Sub-Mediterranean climate with mild,

Chapter | 11 Rivers of the Balkans

wet winters and hot summers (mean annual air temperature: 16–18 C). Similarly, the upper section of the Aoos basin experiences a moderate Sub-Mediterranean and the lower section a Mediterranean climate. The highest precipitation occurs along the central Adriatic Mts. In the Dinaric Mts, precipitation exceeds 300 cm, with up to 550 cm in SW Montenegro. In Albania, mean precipitation ranges from 300 cm (Albanian Alps) to 130 cm (southern part). In NW Greece precipitation is maximal at 240 cm (upper Acheloos and Arachthos basins). The annual precipitation east of the Dinarides–Hellenides range is 25–50 cm less than in the western peninsula. The upper Axios basin exhibits a climate similar to continental European with long cold winters. The area south of Skopje is considered as one of the driest regions in FYR Macedonia. In winter, the dry ‘Vardar’ N-wind creates harsh cold conditions. Large areas of Bulgaria are characterized by a drought-prone climate (Alexandrov 1995). There, annual precipitation is <65 cm and potential evaporation exceeds 100 cm in most lowland sections. In the Pirin, Rila and Rhodope Mts, 30% of the annual precipitation falls as snow. The lower Evros, Strymon and Nestos basins change from continental Mediterranean climatic conditions, to an Interior Sub-Mediterranean climate, and finally to a typical Mediterranean climate in the deltaic plains. The Mediterranean climate, typical for Albania and most of Greece, is influenced by local orographic effects. A southward and a less significant eastward increase in air temperature and evapotranspiration occurs (Dalezios et al. 2002). Many river stretches in S and SE Greece have intermittent flow regimes. Enclosed lowland parts of the mainland experience a continental Mediterranean climate with cold winters and hot summers (e.g. mid-Aliakmon and Pinios basins), while upland reaches experience temperate continental conditions (e.g. upper Aliakmon). In the Pinios basin heavy rainfall may occur in winter and persistent droughts in summer with temperatures >40 C.

11.5.3. Land Use Patterns and Human Pressures In most catchments, evidence of human appearance dates back to the late Pleistocene (Middle Palaeolithic). During that period, the Balkan landscape experienced distinct cycles from deciduous forests to dry steppe, indicating week glaciation. During the Neolithic era, humans started cultivating cereals and legumes, and breeding domestic livestock (Bailey 2000). First settlements were established along rivers and around lakes taking advantage of good grazing conditions and naturally irrigated land. Prehistoric deforestation and soil erosion have been attributed not only to climate change (Hempel 1982) but also to human activities (Butzer 2005). According to the ancient traveller Pausanias, the reason that the Echinades Islands, 10 km offshore of the Acheloos estuary, were not joined to the mainland was that Aetolia remained untilled because the ancient Aetolians abandoned

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the area reducing sediment fluxes. Since the Minoan period, rivers and streams have traditionally been used as natural sewage systems. In addition, humans managed rivers by building dams or diverting channels to protect their settlements against floods (Morhange et al. 2000). The geographer Strabo noted that flood Morhange structures had already been built 2500 BP along the Pinios River. Large-scale deforestation occurred during the Roman, Byzantine and Ottoman Empires. Since the 15th century, rice fields have been irrigated through 560 km of canals in the Thracian plain (Knight & Staneva 1996). However, up to the 19th century, when major shifts of settlements and land use ensued, many areas in the Balkans were considered a wilderness and were scarcely populated. During the 20th century, farming technologies improved, although animaldrawn plows and cart wheels are still common in Albania, Bulgaria and former Yugoslavia. In the 1920–1940s, massive land reclamation took place in Greece to create new land for people displaced from Asia Minor. This resulted in the drainage of lakes, marshes and lagoons (e.g. Lakes Yiannitsa, Amatovou and Ardjan in Axios area and the marshes of Philippi in Strymon area), and channels of large rivers were rearranged (Papayiannis 1992). Land reclamation continued with the construction of extensive irrigation networks. As a result, northern Greece lost 1150 km2, or 73%, of its original wetlands (Psilovikos 1992). In Albania, extensive land reclamation and irrigation projects occurred during the past 50 years resulting in a significant loss of its native forests and marshes (Cullaj et al. 2005; Ciavola et al. 1999). The first dams were already constructed between the 1st and 5th century BC in ancient Alyzia, one of the most important cities of Acarnania (near the Acheloos basin). In the 1950s, the first large dams were constructed in the Balkans. In Bulgaria, huge drainage and irrigation networks were established together with interbasin water transfer projects (e.g. transfer from the Strymon and Nestos headwaters to the Iskar and Evros basins) (Knight & Staneva 1996). In the Neretva basin, 50 km2 of wetlands were drained, several large dams constructed, and water transferred between basins (EIA 2006). During the last decades, a lesser degree of agricultural intensification relative to northern Europe has been observed. However, increasing overall trends in the intensification process are apparent in the plains, especially in Greece, with increasing trends in agrochemical consumption and extensification in mountainous areas (Caraveli 2000). Landscape features and agriculture are intimately linked. The northeastern areas where almost treeless open landscapes prevail are intensively used for arable crops. The Dinaric, Albanian and Balkan Mts are characterized by extensively cultivated landscapes. In Albania and Greece, sharp contrasts between open cultivated and wilderness areas occur. Cereals are grown at a large scale and olives cover hillsides where possible, while Mts are used for extensive grazing. Yields are low due to moderate to high erosion

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creating stony soils (cambisols, luvisols), the dry hot climate and intersection of arable land by shrublands. The Evros, Pinios, Strymon plains as well as the lower Axios and Acheloos, including their main deltas, are fertile landscapes, intensively cultivated and densely populated (Meeus 1995). As a consequence, the plains of Serres (Strymon basin), Thessaloniki (lower parts of Axios and Aliakmon basins), Thessaly (Pinios basin) and Arta (lower Arachthos basin) have been designated as Nitrogen Vulnerable Zones (Directive 91/ 676/EEC). Since Greece joined the European Union in 1981 major efforts have been devoted to control municipal wastes. Today, >90% of the human population is connected to Waste Water Treatment Plants (WWTPs) (with 2/3 primary and 1/3 secondary treatments) (NCE 2003). However, small villages still have simple sewage systems (permeable seep-tanks) that may drain through local aquifers into affluent rivers and there is evidence of poorly functioning WWTPs in the smaller towns. In the other Balkan countries, municipal wastewater is rarely treated and even large towns are insufficiently connected to WWTPs. Moreover, the transition to a freemarket economy caused new problems such as land erosion, increased use of fertilizer, soil salinization, loss of soil fertility and locally a reduction in biodiversity (Sumelious et al. 2005). All Balkan countries face substantial solid waste management problems and have a great number of illegal, uncontrolled landfills. In Greece, mining and industrial activities are limited. Heavy industry is concentrated mainly to large urban centres and seasonally operating food production industries comprise the main industrial pressure. The other Balkan countries have developed significant mining and industrial activities during the communist era. Since the beginning of the 1990s, these countries suffered from a major economic crisis, with a reduction in mining, industrial and agricultural activities that led to an improvement in environmental conditions (UN/EC 1999, 2000, 2002a, b, c, d, 2007a, EIA 2006). It is characteristic that industries previously equipped with WWTPs have often not maintained their facilities. Due to recent economic stability, potential polluting industries have been reactivated (e.g. Rastall et al. 2004). Before the war, Bosnia and Herzegovina was the industrial heartland of former Yugoslavia. Most of its rivers were severely polluted. Today, the Neretva is affected by disposal of untreated municipal and industrial wastewaters, that is by heavy metals from metallurgy effluents (Konjic and Mostar) and from food, lumber, construction material and light industries. Intense agricultural production (mainly citrus orchards) is limited to the delta area (EIA 2006). The first significant morphological alteration occurred in the 1880s, when the Austrian–Hungarian government channelled 22 km between Metkovic and Usce. This part of the river is regularly dredged to ensure navigation and to prevent flooding. Before dam construction and land reclamation, the lowlands were frequently inundated during winter forming a large deltaic lake. Dam construction resulted in salt

PART | I Rivers of Europe

water intrusion in the lower Neretva and the destruction of the delta; of the initial 12 distributaries only three remain. The Drin flows through mountainous terrains and wide, densely populated valleys. The lowland section has been diked. In the Albanian part, half of the arable land is irrigated, whereas mountainous areas remain virtually undisturbed. In the upper basin, iron and chromium mining along with industrial activity affect Lake Ohrid, while copper, chromium, iron and nickel mining and processing (at a reduced rate in recent years) contaminate the middle and lower river sections as well as Lake Shkodra. Shkodra Lake is also threatened by the Moraca River that carries wastewater from an aluminium smelter in Montenegro (UN/EC 2002b). Unsustainable agricultural practices have led to an increase in non-point pollution and erosion (Faloutsos et al. 2006). Gravel extraction from the riverbed favours bed incision. Moreover, the river and lakes are affected by untreated or insufficiently treated municipal wastewater. Besides large reservoir construction, other major hydrological interventions include stream diversions to Lakes Prespa and Ohrid. Finally, illegal logging impacts many tributaries. The Kamchia receives annually 1.85 Mm3 industrial and 15.3 Mm3 municipal wastewater (including water from a storage battery plant in Shoumen) (Mihailov et al. 2005). Flow regulation has caused a degradation of riparian vegetation and localized habitat loss. In the Aoos basin, traditional agro-silvo-pastoral activities have been applied since the end of the 2nd millennium BC (Lafe 2003). Today, most of the catchment remains in a wild, almost untouched state with restricted agriculture, forestry, cattle breeding and some aquaculture. The river receives untreated effluents from five urban settlements (Konitsa, Permet, Argirokastro, Tepelen, Mamalje, Selenica), small-scale industrial areas and by-products of petroleum extraction in the lower section. There are no major dams disrupting the main river course. The lower part was diked in the 1960s and about one-third of the Narta lagoon has been converted into a commercially operated salina. Local gravel and sand extraction and deforestation lead to bank erosion and sediment deposition (Troendle 2003). However, overall, the Aoos is considered as one of the least modified rivers in Europe (Chatzinikolaou et al. 2007). The Evros and Tundja valleys have been colonized by humans since the Neolithic era to exploit their fertile fluvial soils (Bailey 2000). Today, the Evros basin hosts 3.6 million people, mainly around Plovdiv, Stara Zagora, Haskovo, Pazardjik and Edirne and the river is possibly the most impacted of the Balkans. In the Bulgarian part and the Arda basins, mining activities are intense and mostly untreated industrial effluents from heavy metal processing and plating units, chemical, textile, paper and food industries, wood processing, tanneries and dye factories are released into the river. In Turkey, industrial activities are concentrated around Edirne (textile, pharmacy, dairy, tanneries). In the whole basin, municipal WWTPs are inadequate to cover

Chapter | 11 Rivers of the Balkans

the needs of the population. Agriculture is intense and the use of agrochemicals is widespread, especially in the intensively cultivated plains of Plovdiv and Edirne and in downstream sections. Other pressures comprise reservoir construction, extraction of inert material from the riverbed and large-scale deforestation. Land reclamation, including extensive wetland drainage and canalisation, has led to coastline erosion and the destruction of deltaic sand-barrier islets while groundwater exploitation has led to an increase in salinity. Due to its rough relief, the Nestos basin has a low population density and contains relatively natural upland areas. In Bulgaria, industrial point pollution is limited to timber industries and uranium mining at Eleshnitza. Conditions may improve because industries at Razlog have been shut down and mining activities are scheduled to cease (NATURNET 2006). Intensive deforestation, especially in the NW basin, has led to excessive erosion and sedimentation. In Greece, only few agro-industrial units are potential pollution sources. Municipal WWTPs are restricted to Razlog and Chrisoupolis. Extensive agriculture is practiced mostly along the stream valley, especially in the irrigated southern Bulgarian stretch and in the delta. Land reclamation has transformed 80% of the virgin deltaic Kotza Orman forest (140 km2 before World War II) to farmland, creating an extensive irrigation and drainage network (Ministry of Environment Baden-W€ urttemberg 1990). Reservoirs, flood protection schemes, canalisation and embankments initiated the erosion of the delta (Stournaras 1998) and caused a reduction of coastal marshlands. In addition, groundwater exploitation from >2000 shallow wells increased salinization of the coastal aquifers. In the Drama plain of the Strymon basin, humans established settlements already in the Neolithic. Cropping and grazing, especially during historical times, affected soil erosion and aggradation. During the Ottoman period (15th to early 20th century), the basin was intensively farmed and grazed and native forests completely disappeared from the plains and surrounding hills (Lespez 2003). In ancient times, the Greek section was a wide, poorly drained valley with extensive marshes and shallow lakes. Two large shallow lakes survived until recently. In 1927 the former Lake Kerkini covered an area of 5 km2 surrounded by 26 km2 of marshes and wetlands and the former Lake Achinos covered 80 km2 with an additional 88 km2 of wetlands (Petrou 1995). In the 1930s, Lake Achinos was drained and a dam was constructed for flood control, transforming the Kerkini wetlands into a large semi-natural lake. By the 1980s, almost the entire Strymon River in Greece was straightened and embanked. In the Greek part, 33 Mm3/year industrial (slaughterhouses, tanneries, food industries) and 7.3 Mm3/year municipal wastewaters are discharged into the river (HMD 2003). Four WWTPs in Bulgaria and three in Greece are in operation. About 1400 km2 are irrigated land (900 km2 in the Greek section) (HMD 2003).

437

In the Axios basin, near Lake Doirani, early human impacts date back 2800 years BP, when deforestation and stock-breeding led to a replacement of native woody vegetation by xerothermic plants (Athanasiadis et al. 2000). In the 4th century BP, the river mouths of the Axios and Aliakmon were 30 km further inland (Kapsimalis et al. 2005) and the ancient cities of Pella and Skydra were located along the coast. Massive sedimentation led to the formation of Lake Yiannitsa, one of the largest deltaic swamps along the Aegean coast. In the early 1930s, drainage led to the loss of 70% of the former delta wetlands (Psilovikos 1992). During the last 40 years, groundwater exploitation from numerous irrigation wells considerably lowered the water table, and the delta area subsided at a rate of up to 10 cm/year. Consequently, the sea has expanded up to 2 km inland forcing authorities to construct coastal embankments (Stiros 2001). The basin is densely populated and the Axios is one of the most impacted rivers of the Balkans. In FYR Macedonia, the main point pollution sources are untreated industrial and municipal wastewater especially from metal and chemical industries such as agrochemical manufacturing from the cities of Veles and Skopje. Wastewater treatment plants exist only for few cities. The most important nutrient point source is the fertilizer plant of Veles (UNEP 2000). In FYR Macedonia, about 50% of the catchment has been converted into agricultural land, including 800 km2 irrigated land (NEAP 1996). Untreated municipal wastewater release 4700 tons/year N and 857 tons/year P into the river (NEAP 1996). In the Greek catchment, water demand for irrigation and agricultural pollution constitute the most important human pressures. There, almost 80% of the catchment is intensively cultivated, including 1400 km2 irrigated land. Industry, mainly food processing plants, plays a limited role because the bulk of the effluent is treated. The total annual input of nitrogen and phosphorous from industrial sources is 15 tons and 12 tons, respectively (Karageorgis et al. 2003). 7000 years BP, prehistoric man settled the southern shore of lake Kastoria and cultivated the fertile land of the area. The upper part of Aliakmon basin is mainly covered by forests and open pastures, while agriculture (140 km2 irrigated land) and agro-industrial production are localized. This part contributes 1073 tons N/year and 130 tons P/year to the Polyfyto Reservoir in the upper section of the river (Skoulikidis et al. 1998a). In the middle section, mining for asbestos and chromium threatens the river, while three reservoirs cover the valleys. Lignite combustion units in the city of Ptolemais (lying just outside the basin) use the water from the Aliakmon for cooling. They are also a major source of air pollution (SO2, heavy metals) for the entire area. The lower Aliakmon is densely populated and used for intensive agriculture (about 950 km2 irrigated land). The former extensive wetlands are drained by the canal T66. Land reclamations included artificial diversion, alignment of the main river channel, and embankment of the right river bank. Reservoirs have substantially diminished sediment loads, with a consequent reduction of deltaic development, salinization of the

438

deltaic areas and deterioration of wetlands. The large cities of the basin (Kastoria, Grevena, Kozani, Veria, Naousa) are served by WWTP, while untreated urban wastewater of smaller towns and villages and partly treated wastewater from small industrial units (dairy farms, cheese-dairies, food processing plants, hatcheries, slaughterhouses, tanneries, textile industries, dye-houses) are discharged directly into the river, its tributaries or affect groundwaters. In the Pinios basin, the Thessaly plain was a vast lake at the beginning of the Holocene that drained at the end of the Mesolithic era through the narrow Tempe passage (Leivaditis 1991). The latter was obstructed several times in the historical epoch and the landscape changed from river to lake and vice versa, forcing the ancient Greeks to deepen the Tempe Gorge and embank the river against flooding (Papadimos 1975). In the 1930–1950s, levees were constructed along the river and excess water from former Lake Karla, a relict of the ancient Thessaly Lake, was diverted through ditches to the Pinios. Before it was completely drained and converted into agricultural land in the late 1960s, Lake Karla was one of the largest inland wetlands in Greece. Today, the Thessaly plain is the most productive region in Greece and the Pinios basin the most cultivated basin in the Balkans (84% cropland). About 2750 km2 are irrigated. Groundwater exploitation resulted in lowering of the groundwater table by tens of meters (Marinos et al. 1997). In the Thessaly plain, >230 000 tons of fertilizers and 2000 tons of pesticides are used per annum (Bellos et al. 2004). In addition, the river receives partly treated municipal wastewater. The largest city Larisa discharges about 9.1 Mm3/year of treated sewage into the Pinios River, another 4.3 Mm3/year are from sugar factories, paper mills, slaughterhouses, olive-presses, dairy farms and dairies (Fytianos et al. 2002). In the headwater and mountainous parts of the Arachthos basin, human activities are restricted to small hamlets. About 180 km2 of the lowlands are intensively cultivated and irrigated from 4000 wells. The river receives treated wastewater from the city of Arta, untreated sewage from small towns and villages and partly treated wastes from small agro-industries (oil mills, fruit juice factories, dairy farms and slaughterhouses) and stock breading units. Sand is extracted from the riverbed. Impacts of two reservoirs, placed at the lower portion of the river, include erosion of the riverbed, significant upstream propagation of the sea, salinization of aquifers and coastal lagoon waters and deltaic and sand-barrier erosion (Mertzanis 1997). The Sperchios is a small basin dominated by semi-natural features, particularly in its upper and mid portions. This dynamic delta lies just north of the famous Thermopylae battlefield where the Greeks fought against the Persians in 480 BC. The narrow Thermopylae pass was of strategic importance controlling the transition between the sea and the coastal Mts. During the past 2500 years the delta expanded by 100 km2 (average: 4.1 ha/year). This average rate increased during the past century to 13 ha/year, mainly as a

PART | I Rivers of Europe

consequence of deforestation (Zamani & Maroukian 1980), reaching 23.6 ha/year between 1943 and 1971 (Kotoulas 1988). The former extensive marshes and riparian forests were mostly converted into agricultural land by the middle of the 20th century through the construction of a spillway connecting the upper delta with the sea and of levees bordering the river. Today, 154 km2 are irrigated and 22 700 tons of fertilizers and 306 tons of pesticides are applied each year (Dassenakis et al. 2005). Urban wastewater from the city of Lamia are treated, however, sewage of a number of small towns and villages remain untreated. Besides olive oil refineries and small manufacturing units (slaughterhouses, dairies, a dye-house, a cannery), industrial pollution is limited. The Acheloos drains one of the least populated Balkan basins with mostly semi-naturally vegetated areas, especially in the upper and mid portions. Interest in draining and controlling floodwaters of the rivers’ delta is evident since ancient times as depicted in the myth of the battle of Hercules with Acheloos the river god (Papadimos 1975). The shifting lower course created conflicts between the classical Greek tribes of Aetolia and Akarnania because the river was the border. At the beginning of the 20th century, large swamps still covered the western part of the delta. In the 1960–1970s, wetlands were drained and extensive reclamation works were completed to irrigate 500 km2 while from the 1960s onward large hydropower reservoirs were being constructed. As a result of siltation, the ancient shipyard of Oiniadaes (500 BC) is now about 9 km inland. Due to hydromorphological pressures (construction of dams and embankments along the lower portion of the river, creation of an extensive irrigation and drainage network and dredging of the river channel and the coastal lagoons), the Acheloos delta has been converted into a semi-natural regulated system (Psilovikos et al. 1995), with a dramatic reduction in sediment deposition, groundwater salinization and upstream sea water propagation. Industry plays a minor role in the catchment. The major towns (Agrinio, Messolonghi, Karpenisi, Stratos, Aetoliko and Thermo) are connected to WWTPs. The Alfeios basin has been occupied by humans since the Palaeolithic and Neolithic periods. The ancient sanctuary of Olympia is between Alfeios and its small Kladeos tributary. In the first centuries AD major alluviation events (as a result of the drainage of Pheneos karstic lake, connected underground with Ladon tributary) buried the ancient city (Kraft et al. 2005). To control floods, the lower river was diked. About 230 km2 are irrigated. The former extensive coastal lagoons were drained in the early 1970s (Agoulinitsa and Mouria lagoons). Small agro-industrial units, partly served by WWTPs and livestock breeding farms are scattered throughout the basin. Municipal WWTP facilities are restricted to the towns of Pyrgos, Megalopolis, Krestena and Olympia. In the upper section of the river, the Megalopolis lignite power plant produces high SO2 emissions (134 000 tons/year) due to the bad quality of lignite and the absence of pollution abatement equipment (NTUA 1997). Illegal extraction of inert material

Chapter | 11 Rivers of the Balkans

from the riverbed in the lower section resulted in bed incision of up to 5 m (Yannopoulos & Manariotis 2005). In summer 2007, wildfires burned large forested areas. The great city of Sparta was located along the banks of the Evrotas. It flourished after 1000 BC when the Dorians occupied Laconia. In ancient times, the deltaic area was a large swamp that was drained in the 1930s. Today, the lower river has been diked to prevent flooding and to expand agricultural land. The riverbed is regularly dredged. Land use in the basin is characteristic of the dry Mediterranean and dominated by olive groves. Over 90% of total nitrogen and phosphorous inputs originate from agriculture (Nikolaidis et al. 2006). Point pollution sources comprise untreated and treated (city of Sparta) municipal wastewater and effluents from agro-industrial units including >90 olive oil presses, orange juice factories, slaughterhouses, food industries and a plastic manufacturing plant – all concentrated around the city of Sparta. Wildfires in summer 2007 burned 216 km2 of Mt Parnon.

11.6. HYDROLOGY AND BIOGEOCHEMISTRY 11.6.1. Hydrology and Temperature Hydrological data are mainly derived from UNESCO (www. rivdis.sr.unh.edu) and from the Hellenic Public Power Corporation (Tables 11.1 and 11.2). The total river discharge in the European Mediterranean region is 330 km3/year (UNEP/MAP 2003). All Balkan rivers contribute 85 km3/ year. The rivers included in this chapter contribute 83% (70 km3/year) to the Balkan discharge, or 21% to the European Mediterranean runoff. Because the eastern Balkan basins exhibit a semi-arid climate, specific discharge is low, ranging between 4 and 14.9 L/s/km2. The western Balkan basins are characterized by high precipitation and specific discharge ranges from 18.3 to 34.6 L/s/km2. The Drin and Neretva rank 3rd and 4th in total annual discharge of all rivers in the Mediterranean region (after the Rhone and the Po Rivers). A large proportion of Balkan rivers is affected by hydropower generation. Most rivers are strongly fragmented by dams and flow regulation (Table 11.1). The Evros, Axios, Pinios, Alfeios and Aoos are ‘moderately fragmented’, while only the Sperchios and Evrotas are free-flowing. The hydrological and thermal regime depends on the seasonal distribution and type of precipitation (rain or snow), as well as on hydrogeological features (e.g. karstic or alluvial aquifers, degree of surface/subsurface flow interactions). Balkan rivers reveal a strong seasonal hydrology, mostly flashy in nature and with low summer flow. Three flow regime types are identified: (I) a pluvial type with discharge maxima in winter, (II) a pluvio-nival type with maximum discharge in winter and a second peak in spring (snowmelt) and (III) a nivo-pluvial type with maximum discharge in spring and a second peak in winter. Type I rivers include

439

the Neretva, Evros, Arachthos, Pinios, Sperchios, Acheloos and Alfeios Rivers, with 63–78% of their annual runoff between November and March. Drin, Aoos and Nestos belong to type II, while Strymon, Axios, Aliakmon and Evrotas are type III rivers. In type II and III rivers, 20–30% of the runoff is derived from snowmelt. Dam operations smooth seasonal variations and result in a modification of the hydrological regime downstream of reservoirs. Thus, Acheloos, Nestos and Aliakmon now present high to maximum discharge in July due to peak hydropower production. Based on the ratio between the long-term maximum and minimum monthly discharge (Table 11.2), four groups of rivers can be distinguished. For regulated rivers such as the Neretva, Nestos, Acheloos and Aliakmon, the karstic Aggitis and in the middle section of the Drin, the seasonal variation ranges between 1.5 and 3. The Axios, Alfeios (with karstic inflows) and Kamchia, as well as the upper Evros, Strymon and Nestos exhibit moderate seasonal variations with ratios between 3.2 and 7. The Aoos, lower Drin (Vau Deze), Strymon (Rupel), Evros (Edirne) and Arachthos show high hydrological variation with ratios between 7.6 and 15. Finally, the Pinios, Aliakmon and Evrotas exhibit very high seasonal variations (Table 11.2). Rock permeability drives baseflow contribution in river flow and regulates seasonal runoff variation and floods. The correlation between the ratio and the percentage contribution of baseflow in river runoff shows that high baseflow contribution smoothens seasonal hydrological variation (Figure 11.2). Over the past 40–45 years, the Balkan rivers have undergone dramatic discharge reduction (Figure 11.3), a common phenomenon for the entire Mediterranean region (UNEP/ MAP 2003). In addition, a severe drought at the end of 1980s – beginning 1990s created major water shortages (e. g. Mimikou 1993; Knight & Staneva 1996). Besides climate variability and change, evaporation from reservoirs and extensive water abstraction for irrigation diminish river runoff. The Evrotas has experienced a 79% discharge reduction (1974–2004), followed by Axios (57%, 1961–2000), Sperchios (48%, 1950–1990; Tsakalias & Koutsogiannis 1995), Kamchia (38%, 1936–1986), Drin (31%, 1965– 1984) and Arachthos (30%, 1982–2006). The annual discharge of the Aoos decreased by 24% (Greece) and 19% (Albania) (1964–1987), the discharge of the Acheloos decreased by 11.6% (1980–2006) and of the Aliakmon by 12.2% (1963–2006). In the Nestos, discharge remained stable (0.8%, 1966–2006), whereas it increased in the Evros by 7.5% (1963–1985). On average, the Neretva reveals the lowest and Strymon the highest mean annual water temperature (Table 11.3). Neretva, with a low snowmelt contribution to river runoff and substantial karstic flow shows weak seasonal variation. Reservoir outflow smooths seasonal variation and alters the thermal regime in receiving water bodies. For example, thermal variation downstream the Acheloos reservoirs is low with minimum temperature in February and maximum in September (in free-flowing rivers minimum water

440

TABLE 11.2 Discharge characteristics of the Balkan Rivers (in m3/s) Period

A (km2)

NQ

MNQ

MQ

MHQ

13300 12311 5400 12368 4857 665 5420 7931 19693 35165 3698 4090 4393 5509 2171 6777 10800 4650 20200 5505 5800 6030 6180 640 1778 1778 1845 3570 4118 8563

48.3 60.7 47.8 66.8 3.74 4* 36.1 14.2 20.4 27.1 31 15.2 9.7 4.4 3.5 13.5 27* 24.3 29.7 4.57 10.9 59.5 8.6 3.51 11.5* 4.9 8.1 48.3 60.7 11*

69.5 93.2 98.2 339 21.8 27 146 51.6 113 110 52.6 36.3 44.5 26.4 11.7 47 110 57.3 115 48.3 43.8 80.8 58 18.2 62 45.5 49 96.7 116 81

114 163 164 613 69.5 58* 260 123 272 299 76 73.4 111 84.4 30.5 111 228* 102 275 138 88.8 125 89.6 51.1 130.9* 129 113 182 244 171*

Sperchios Alfeios Evrotas

Kobotades Alfeiousa Vrodamas

1946–2005 1946–2005 1976–1984 1960–1968 1936–1986 1963–1971 1965–1984 1936–1985 1965–1979 1936–1985 1998–2005 2000–2006 1966–1989 1989–2000 1965–1979 1965–1979 1929–1932/1951–1956 1978–1990 1961–2000 1962–1988 1975–2006 1986–2006 1986–2006 1965–2003 1950–1980 1982–2006 1999–2006 1980–2006 1980–2006 1903–1911/1932–1942/ 1951–56 1932–1941/1949–1959 1949–1956 1974–2004

23 43 27 13 0.09

Pinios

Opuzen Metcovic Ura e Dodes Van Deze Gzozdevo Konitsa Dorze Plovdiv Harmanli Svilengrad Thysavrosb Platanovrisib Temenos Stavroupoli Radzavitza Krupnik Rupel Skopje Axioupoli Ilarion Polyfyto Sfikia Asomata Tsimovo Pournari Pournari I Pournari II Kremasta Kastraki Giannouli

62 67 2.9

110* 145* 10.4

a

Neretva Drin

Kamchia Aoos Evros

Nestos

Strymon

Axios Aliakmon

Arachthos

Acheloos

1165 3534 2000

21 2 1.6 0.7 2.2 3.8 2.7 0 1.5 5 6.6 3.4 2.1 0 15 0 0.250 0 0 1.9 13

0

12* 21* 0

HQ

MHQ/MNQ

MAX/MIN

Source

193 297 302 772 191

2.4 2.7 3.4 9.2 18.6

595 258 516 911 96.6 112 199 406 41 157

7.2 8.7 13.3 11.0 2.5 4.8 11.4 19.2 8.7 8.2

164 949 369 184 196 191 97

4.2 9.2 30.1 8.1 2.1 10.4 14.6

235 145 320 1118

26.4 13.9 3.8 4.0

1.7 2.0 2.9 11.2 8.0 14.5 7.7 5.0 3.2 5.1 1.5 2.2 6.5 3.5 4.2 5.0 8.4 4.2 6.4 16.6 3.2 2.0 3.1 13.9 11.4 8.0 12.1 1.9 1.9 15.5

Croatian Meteorol. & Hydrol. Service UNESCO UNESCO UNESCO Therianos 1974 UNESCO UNESCO UNESCO UNESCO PPC PPC GRDC Darakas 2002 UNESCO UNESCO Therianos 1974 GRDC EUROCAT PPC PPC PPC PPC PPC PPC PPC PPC PPC PPC Therianos 1974

9.2 6.9 20.1

Therianos 1974 Therianos 1974 HMRDF

21.9

–

A: catchment area upstream of gauging station, NQ: lowest measured mean monthly discharge, MNQ: arithmetic mean of the lowest measured mean monthly discharge, MQ: arithmetic mean annual discharge, MHQ: arithmetic mean annual of highest mean monthly discharge, HQ: highest measured mean monthly discharge, * arithmetic mean of month with minimum/maximum discharge, MAX/MIN: ratio between the month with maximum discharge and the month with minimum discharge, PPC: Public Power Corporation, HMRDF: Hellenic Ministry of Rural Development and Food. a b

water level. water used for hydropower production.

PART | I Rivers of Europe

Station

River

441

Chapter | 11 Rivers of the Balkans

FIGURE 11.2 Correlation between baseflow contribution to river flow and the ratio of maximum to minimum monthly discharge.

temperature occurs in January and maximum between June and August). Based on long-term records (1948–2005), the mean annual temperature of the Neretva increased by 0.27 C (average: 0.017 C/year), the maximum annual temperature increased by 0.42 C and the minimum temperature by 1.7 C. This is a general trend that also holds for all Greek rivers except the Strymon (Table 11.3). The Neretva, despite a high annual precipitation, has a low stream density because water is lost to the underground. Karstic springs contribute substantially to surface flow (Stambuk-Giljanovic 1999). Trebisnjica, one of the longest ‘subterranean’ rivers in the world, supplies water to the Neretva delta through karstic springs. In addition, excess water from Trebisnjica is artificially transferred to the Neretva. Maximum runoff occurs in December and minimum in July–August. The upper basin is characterized by a nivopluvial flow regime, a high specific discharge (over 45 L/s/ km2), and high water level fluctuations (up to 14 m near Mostar). Five hydropower plants in Bosnia and Herzegovina (Jablanica, Rama, Grabovica, Salakovac and Mostar) impound a total area of 36 km2 and store 1070 Mm3. In the downstream section, flood control measures and karstic inputs (26% of river runoff) reduce seasonal water level fluctuations (Glamuzina et al. 2002).

FIGURE 11.3 Long-term discharge variation (mean annual discharge) in selected Balkan rivers.

The Drin originates from the Lake Ohrid-Prespa karstic system. The Prespa Lake (surface area: 274 km2, basin: 1300 km2, mean depth: 16 m, maximum depth 47 m) contributes to Lake Ohrid about half of its karstic groundwater inflows (Amataj et al. 2007). During the past 20 years a decline of the water level in Lake Prespa has been observed. Lake Ohrid discharges 0.69 km3/year through an artificiallycontrolled outlet into the Black Drin. It is a deep lake (mean depth: 155 m, maximum depth: 288 m) that covers 358 km2 and drains 1310 km2. Lake Shkodra (basin area: 5180 km2), receives its waters mainly by the Moraca River (99 km long) and drains into the 44 km long Buna River that joins the Drin 1.5 km before the mouth. The hydrological regime of Buna and the water level of Shkodra depend on the flow of the Drin. During winter floods, the Drin floods back into the Buna, and consequently the lake experiences flooding from Drin water (Faloutsos et al. 2006). As a result, the lake

TABLE 11.3 Inter-annual and intra-annual variations of river water temperature (period: 1977–2003) River

Neretva Evros Nestos Strymon Axios Aliakmon Pinios Acheloos

Station

Metcovic Dikea Papades Rupel Axioupoli Ilarion Larisa Kastraki

SD: standard deviation.

Inter-annual

Intra-annual

Mean

Range

S.D.

12.15 15.61 15.89 18.09 15.25 15.02 17.31 14.96

3.3 9.49 9.27 7.08 4.27 4.73 12.88 4.61

0.64 1.9 2.19 1.94 1.13 0.97 2.25 1.22

Trend ( C/year) 0.052 0.014 0.16 0.024 0.029 0.014 0.009 0.065

Range

S.D.

11.1 18.1 18.4 15.1 18.5 17.9 17 10.36

4.04 6.86 6.14 5.51 6.81 6.86 6.58 4.01

442

surface varies from 372 to 542 km2 and the maximum depth exceeds more than five times the mean (8 m). In the mountainous basin, three groups of glacial lakes (Lura, Ballgjaj and Dhoski) are found. Snowmelt in the upper part of the river causes discharge maxima in May, while in the lower section maxima occur in December. Seasonal discharge variation increases downstream (Table 11.2). Two hydropower plants are in FYR Macedonia (Globochica and Spilje) and three in the lower Drin in Albania (Komani, Vau Deza and Fierza). Fierza, covering 97 km2, is the largest in Albania. Of the two Kamchia branches, Golyama is considered the main stem. Two reservoirs are along Luda Kamchia (Kamchia and Tzoveno) and a third one (Tiche) is formed through the confluence of three Golyama tributaries. The Kamchia reservoir provides most of the drinking water for the cities of Burgas and Varna (storage capacity: 229 Mm3). After reservoir construction, the total flow decreased from 0.87 to 0.61 km3/year (Jaoshvili 2002). The river exhibits a strong seasonal regime with maximum flow in February/March and minimum flow in October (Table 11.2). The Aoos catchment has a high stream density (0.92 km/ km2) and a high runoff coefficient (0.95 at Konitsa) due to the dominance of flysch. Maximum flow occurs in December and minimum in August–September. Between 21% and 25% of the flow originates from snowmelt and 66% from rain. Seasonal hydrological variation decreases from the headwaters downstream. A small artificial lake (surface area 11.5 km2, total storage capacity 260 Mm3) was created at the subalpine plateau (1400 m asl) that diverts 10% of Aoos water towards the Arachthos basin. The Evros has about 100 tributaries. Discharge data are limited for the Evros, therefore only estimates on total annual runoff are presented (Table 11.2). Mean annual discharge of the Arda tributary is 2.2 km3, of Tundja 1.08 km3 and of Ergene 0.87 km3. Maximum flow occurs between March and May, minimum between July and September. Rainfall contributes 52–55% to discharge in the upper (Plovdiv) and middle (Harmanli) basin, respectively, and increases to 71% at Edirne. Seasonal discharge variation increases, respectively (Table 11.2). There are 21 large reservoirs, mainly along Bulgarian tributaries (four in Ardas and three in Tundja) with a total storage capacity of 3440 Mm3. Despite numerous reservoirs, runoff remains highly variable with frequent severe floods. Among the most disastrous were the floods in 2005 and 2006 (UN/EC 2007b). The Nestos is snow fed in the Mts and rain fed in the lower reaches. In the middle section (at Temenos) rain and snow contribute 54% and 28%, respectively, to total discharge. Maximum flow occurs in spring (in May in the upper part and in April in the lower part of the basin), and minimum in August–September. In Bulgaria, six reservoirs are on tributaries, the largest is on the Dospatis (total storage capacity 430 Mm3). In Greece, three large hydropower reservoirs, Thysavros, Platanovrisi and Temenos (under construction)

PART | I Rivers of Europe

and a small irrigation dam (Toxotes), occur along the main stem. The former two cover 56 km2 and can store 798 Mm3. In the Bulgarian part of the Strymon, the runoff coefficient varies substantially (0.01–0.95) (Knight et al. 2001). In Bulgaria, 56 multipurpose reservoirs with a total storage capacity of 141 Mm3 have been constructed. Pchelina (area: 5.4 km2, capacity: 55 Mm3), Studena (capacity: 25 Mm3) and Djakovo are the largest. However, the risk of flooding is high. Moving downstream, the ratio between monthly maximum (May) and minimum (August) discharge increases: 4.2 at Radzavitza, 5.0 in Krupnic and 8.4 in Rupel. The water balance in the Greek sub-basin is positive (Tzimopoulos et al. 2007). The Aggitis tributary has a mean annual discharge of 0.55 km3 (8.3 L/s/km2). The Kerkini reservoir has a surface area of 109 km2 and a total storage capacity of 365 Mm3. It has a maximum depth of 10 m (average: 1 to 3 m). Upstream of the lake, the river ceases surface flow in summer due to water abstraction for irrigation. The Axios still exhibits a near-natural flow regime. Highest flow occurs in April and minimum in August. Rain and snow contribute 53% and 30%, respectively, to total flow. The mean annual runoff of Crna is 1.18 km3, of Treska 0.76 km3, of Bregalnica 0.44 km3 and of Pcinja 0.40 km3. Until recently, floods caused major damages. For example the city of Skopje was destroyed in 1963. To control floods, 17 large dams have been constructed at river tributaries in FYR Macedonia with a total storage capacity >500 Mm3. A small irrigation dam at the delta remains closed between May and September, allowing only 1 m3/s to pass during the dry period (Konstantinidis 1989). Doirani Lake has an area of 40 km2 (basin area: 272 km2), a total volume of 50.7 Mm3, and a maximum depth of 10 m. Overflow water enters the Axios through an artificial canal. Since the end of the 1990s, the water level of Lake Doirani has been receding as a result of drought and overexploitation for irrigation in Greece. In the free-flowing upper Aliakmon, the ratio between monthly maximum (March) and minimum (August– September) discharge is one of the highest in the Balkans (Table 11.2). About 70% of the river is hydrologically heavily modified due to damming. Reservoirs (Polyfyto Sfikia and Asomata) cover 81 km2 and can store 2.9 km3. Downstream of reservoirs, maximum discharge occurs in summer and minimum in spring. The shallow karstic Kastoria Lake (28 km2, mean depth: 4.4 m) overflows in the Aliakmon through a ditch. Pinios has only one major dam along the Smokovo tributary, although many small temporary earthen dams are constructed by farmers to serve irrigation. However, irrigation has deteriorated the water balance, which is strongly negative (reaching up to 1.2 km3/year; Loukas et al. 2006). As a result, the river partly dries out during dry years. Simultaneously the river has a flashy regime (Table 11.2) and despite flood protection measures severe floods continue to threat the region. The mostly unregulated Sperchios River receives 63 mainly torrential tributaries. About 69% and 19% of river

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Chapter | 11 Rivers of the Balkans

flow originates from rain and snow, respectively. Flush floods and high sediment loads cause frequent damages to downstream villages, agriculture and infrastructure. The runoff of the Acheloos is caused by rain (71%) and snowmelt (19%). The runoff coefficient decreases from 0.65 (headwater at Mesohora) to 0.51 (mouth). In the headwater and middle sections, four large reservoirs (Kremasta, Kastraki, Stratos and Plastiras) exist and two (Mesohora and Sykia) are under construction. These reservoirs will cover >150 km2 with a total storage capacity of 6.6 km3, 1.5 times the total annual discharge. From the Plastiras reservoir, 0.15 km3/year are transferred to the Pinios basin. Prior to dam construction, maximum discharge occurred in December and minimum in August. Today, discharge peaks in July and 30% of the annual flow occurs during summer (compared to 11% prior to dam construction). In the lower section, the natural Trichonis karstic lake (97 km2, maximum depth: 59 m, volume: 2.8 km3) is connected to the 13 km2 shallow alluvial Lake Lysimachia through an artificial canal. Excess water from these lakes is transferred to Acheloos. The river is also connected to the shallow alluvial Lake Ozeros during floods. The Arachthos basin has a high stream density (0.91 km/ km2; Karibalis et al. 2001), high specific discharge and a flashy flow regime (Table 11.2). Maximum discharge occurs in December–January and minimum in August. The reservoirs Pournari I and II cover 21 km2 and can store 800 Mm3. These reservoirs decrease seasonal flow variations but only slightly alter the relative seasonal flow variation. Water losses through irrigation (130 Mm3/year) and evaporation from reservoirs (12.5 Mm3/year) are counter balanced by water transferred from the Aoos River (138 Mm3, Mertzanis 1997). The Alfeios is partly supplied by karstic runoff. The Ladon and Lousios tributaries contribute 0.64 and 0.21 km3/year, respectively. Maximum discharge occurs in January and minimum in August, while the Ladon shows its maximum flow 1 month later due to karstic influence. In the downstream section, baseflow contributes 14% to total runoff, compared to 73% by rain. In the upper basin, baseflow contribution is higher (23%) due to karstic inflows. A small hydroelectric dam along the Ladon tributary (4 km2, total storage capacity: 58 Mm3) is used for flood control and irrigation and a small dam located 10 km upstream of the mouth, serves irrigation. Due to intensive water abstraction, drought and high transmission losses, parts of Evrotas show an intermittent flow regime. From its tributaries, only the Oinous ensures a permanent flow for most of the year. Apart from significant direct water abstractions for irrigation, the river remains unregulated, only localized earthen water abstraction weirs exist in summer. It has a flashy flow regime causing severe floods. Snowmelt (almost 40% of river runoff) and karstic outflow lead to discharge maxima in March.

11.6.2. Biogeochemistry In Greece, medium and large rivers have been monitored since the 1970s at monthly intervals for chemical quality (Ministry of Rural Development and Food, HMRDF and Ministry for the Environment Physical Planning and Public Works, HME), whereas studies have focused on their hydrochemical regime and pollution status (Skoulikidis 1993; Skoulikidis et al. 1998b, 2006; Nikolaou et al. 2002; Lekkas et al. 2004; Konstantinou et al. 2006). For the other Balkan countries, such data are often not available or inaccessible. Moreover, most technical reports and scientific publications are written in the native language. The Greek data presented are from HME and HMRDF as well as from scientific publications and technical reports. For the other Balkan countries, we used the EIONET database as well as information derived from scientific publications.

11.6.3. General Characterization The geology and climate are the main controllers of the hydrochemical regime. Geochemical and hydrogeological variability as well as precipitation patterns control water temperature and solute concentrations. Further, wastewater discharge, reservoir outflow and water abstraction locally affect chemical composition. The southern Balkan rivers belong to three hydrochemical zones with distinct hydrochemical composition. Zone 1 rivers (Evros, Nestos, Strymon and Axios) are of an acid silicate type with low air temperature. Zone 2 rivers (Aliakmon, Pinios and Sperchios) belong to a mafic silicate type, together with low precipitation. Zone 3 rivers (Aoos, Acheloos, Arachthos, Alfeios and Evrotas) are of a carbonate type, and generally with high precipitation (Skoulikidis et al. 2006). Zones 1 and 2 correspond to Ille’s ecoregions 6 and 7, while zones 2 and 3 correspond to the geologic (and hence geochemically) and climatic diverse Internal and External Hellenides. It is speculated that this hydrochemical zonation is broadly applicable to the entire Balkan Peninsula. For example the Kamchia basin lies in the extension of zone 1 to the north, while the extension of zone 3, west of the Dinarides-Albanides range, covers the Drin and Neretva basins. The majority of the Balkan rivers belong to the calciumcarbonate hydrochemical type (Ca > Mg > Na > K– HCO3 > SO4 > Cl) (in meq/L), similar to the average of rivers worldwide (Meybeck 1981). The Aoos headwaters are of a magnesium carbonate type (Mg > Ca). In Evros, Acheloos and Kamchia and in Nestos and Aliakmon headwaters, sodium is the second dominant cation while chloride is in Acheloos and Arachthos. In general, total dissolved solid concentration increases downstream and is proportional to the percentage of recent (Neogene and Quaternary) sediments in the river basins. The reasons include high surface/groundwater interaction in areas with vast alluvial aquifers, high weathering and dissolution capacity of unconsolidated sediments, and a downstream increase in

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PART | I Rivers of Europe

FIGURE 11.4 Correlations between discharge and specific conductance and discharge and nitrate concentration in the Axios and Axioupolis Rivers (data: Hellenic Ministry of Agricultural Development and Food, period: 1971– 2000).

pollution and evapotranspiration (Skoulikidis 1993). For example Nestos reveals pronounced upstream/downstream hydrochemical differences, as it flows from the Rhodope Mts, where weathering resistant rocks dominate and the climate is Transitional Mediterranean, to karstic formations and deltaic sediments, where the Mediterranean climate prevails (Skoulikidis 1991). Rivers in the northern part of zone 3 (Acheloos, Arachthos, Aoos) are only slightly mineralized due to high precipitation, causing dilution, and the dominance of poorly leached soils in their catchments. In the Peloponnese (Alfeios, Evrotas), mineralization increases southwards as climate becomes semi-arid. Evrotas, at the southern part of zone 3, exhibits the maximum mineralization of all examined Balkan rivers. Rivers in zone 2 (Aliakmon, Pinios, Sperchios and Aoos headwaters) present hard waters and are enriched with magnesium carbonate due to ophiolite weathering. In zone 1, the prevalence of magmatic and metamorphic rocks with sulphide ore dykes cause low (Nestos, Kamchia) to medium (Strymon, Axios) mineralization associated with high alkali and sulphate ion percentages (Evros, Kamchia, Nestos, Strymon, Axios) and generally medium hardness. Despite its position within zone 1, Evros presents exceptionally high mineralization (caused by elevated sulphate concentration), as a result of human impact (mining, industrial and municipal wastewaters) (Skoulikidis 1993). The Alfeios has the second highest sulphate concentration behind Evros due to gypsum dissolution and lignite mining and combustion (Skoulikidis et al. 2006). Increased chloride concentrations are caused by municipal wastes (Evros, Evrotas and Axios), marine deposits (Sperchios), evapotranspiration (Lake Doirani) and/or marine aerosol (Acheloos, Arachthos). Heracleitus (500 BC) said that ‘No man ever steps in the same river twice’. This means that a river is not the same at two different times, an aphorism that fully reflects the strong temporal hydrological and chemical variability of Balkan rivers. Most Balkan rivers reveal larger temporal than

spatial hydrochemical variation governed by the factors drought, dilution and flush flows (Skoulikidis & Kondylakis 1997). In general, specific conductance peaks during base flow conditions and is lowest during spring (snowmelt) and winter (rainfall). Thus, an inverse relationship between discharge and conductivity is commonly apparent (e.g. Figure 11.4). Such rivers are termed as ‘dilution type’ (Skoulikidis 1993). Floods are associated with soil–salt flushing and occasionally can enhance solute concentrations. The Aliakmon is a characteristic ‘flush type’ river showing maximum mineralization in winter (December). For the Evros, Strymon and Pinios, weak flushing processes occur in winter (December, January) and for Axios in autumn (October). The Pinios exhibits maximum mineralization in autumn (October), low levels in July–August and March and a minimum in December. This peculiar monthly chemograph is driven by increased dilution in December and March due to peak rainfall and snowmelt, respectively, and possibly by photosynthetically induced carbonate precipitation in pool dominated reaches during the dry period. Karst dominated rivers with weak seasonal runoff fluctuations, such as the Neretva, Aggitis and Evrotas, show low seasonal solute variations. Regulated rivers reveal an artificial temporal chemograph. For example in Acheloos, solute concentrations are low in summer as a result of carbonate precipitation in upstream reservoirs and high in winter due to inputs of hypolimnion waters (Skoulikidis 2002). The increase in solutes during a period of severe drought (end of the 1980s – beginning of the 1990s) demonstrates the impact of climate variability on river hydrochemistry. At that time, the conductivity in Axios rose by 40% compared with previous years (Skoulikidis et al. 1998b).

11.6.4. Sediment Loads (Long-Term Trends) The sediment transport data are from Poulos et al. (1996), Gergov (1996), Poulos and Chronis (1997), UNEP/MAP (2003), Eurosion (2004), Becvar (2005) and Zarris et al.

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Chapter | 11 Rivers of the Balkans

(2006). Balkan rivers tend to have naturally high sediment fluxes due to high relief ratios, high seasonal climatic variation, easily erodible rock formations and sparse vegetation. Fluxes have further increased by massive deforestation, fire, grazing and other human activities such as mining (e.g. Ardas River). The estimated total natural sediment flux of all rivers examined is 115 Mt/year (UNEP/MAP 2003; Eurosion 2004). In the western Balkans (Arachthos, Aoos, Acheloos, Drin and Neretva basins), high precipitation in combination with flysch bedrock cause specific sediment yields of 1000–16 000 tons/km2/year. In autumn, heavy initial rains on desiccated soils often cause landslides, especially where unconsolidated sediments prevail. During the first flush events, occurs often 50% to 95% of the annual sediment transport (Poulos et al. 1996). In the eastern basins, where magmatic and metamorphic rocks prevail (Kamchia, Evros, Tundja, Nestos, Strymon and Axios) and sediment transport mainly peaks during snowmelt, sediment yields are low and range between 9 and 200 tons/km2/year. Basins formed by a mixture of bedrock types (Sperchios, Aliakmon and Pinios) exhibit intermediate sediment yields (460– 1000 tons/km2/year). The organic fraction of suspended sediments transferred by major Balkan rivers is low (on average 2.83% POC, 1.69% PN). More than 50% of the inorganic fraction consists of muscovite-illite (27%) and silica (25%) (Skoulikidis 1989). In general, total sediment flux increases with catchment area. Hence, the total load of the Evros, Axios, Drin and Neretva Rivers is between 14 and 26 Mt/year. However, high sediment transport also occurs in small narrow mountainous basins such as the Aoos and Arachthos with 8.4 and 7.3 Mt/ year, respectively. The Aliakmon, Pinios and Strymon have similar fluxes (between 4.8 and 4.1 Mt/year), followed by Acheloos and Sperchios (2 Mt/year), while the flat Kamchia basin transports only 0.46 Mt/year (Cagatay 1997). Since the Mediterranean Sea is characterized by low wave energy and negligible tidal activity, the aerial extent of deltaic areas is correlated to sediment fluxes. However, this is not true for the large Pinios and Strymon basins. The Pinios River has a relatively small delta due to its low-gradient and cyclic basin shape that retains most sediment. Similarly, Strymon has a surprisingly small deltaic area as a consequence of sediment trapping in the former Achinos Lake. The long-term decline in river runoff, in combination with enhanced sediment retention in reservoirs, has resulted in a dramatic reduction in sediment fluxes during the past 50 years. For example the sediment transport of the Strymon River has decreased from 6.5 Mt/year (1932–1962) to 2.2 Mt/year (1962–1977) and to 1.3 Mt/year (1984–1990) (Crivelli et al. 1995; Psilovikos et al. 1994). The Drin experienced a 13-fold sediment reduction compared to pre-industrial rates (REAP 2006). Today, the proportion of the annual sediment flux trapped behind reservoirs is 99% for the Acheloos, 95% for Nestos, 85% for Aliakmon, 80% for Arachthos and 60% for Kamchia (Piper & Panagos 1981; Mertzanis 1997; Paraskevopoulos-Georgiadis 2001;

Jaoshvili 2002; Kapsimalis et al. 2005). Consequently, deltaic areas of dammed rivers are not expanding (Poulos et al. 1996) or have even started to decrease in size (Stournaras 1998). It is predicted that the sandy beaches and island barriers of the Acheloos delta will gradually erode and coastal lagoons will be intruded by sea water (Bouzos et al. 1994). Global sea level rise will further accelerate the destruction of many deltaic areas of the Balkans.

11.6.5. Nutrients and Pollution Table 11.4 lists the basic information about dissolved oxygen and nutrient concentrations in Balkan Rivers. To ensure comparability among rivers, we only report data from the lowermost monitoring station. On average, the Balkan rivers are well oxygenated with oxygen concentrations ranging from 10.5 mg (Sperchios) to 7.2 (Kamchia) mg/L. Minimum monthly values range from 9.5 mg (Aliakmon) to 5.8 (Evros) mg/L. Oxygen concentrations <5 mg/L are only sporadically recorded (e.g. Evros: 4.2% of all measurements). Minimum oxygen concentrations occur in summer. In Axios, Aliakmon (upstream of the dams) and Strymon, the correlation coefficient (r2) between monthly water temperature and dissolved oxygen range from 0.78 to 0.91 indicating that oxygen concentration is mainly physically driven. In Pinios, Nestos and Acheloos, the coefficient varies between 0.63 and 0.45 suggesting a higher biological influence, while in Evros no correlation exists between water temperature and oxygen. In fact, Evros, Nestos and Acheloos have high oxygen concentrations in summer as a consequence of increased photosynthesis in-stream (Evros, Nestos) or in upstream reservoirs (Acheloos). Figure 11.5 shows multi-year average nutrient levels in the Balkan rivers. The upper Aoos presents minimum concentrations of DIN (dissolved inorganic nitrogen), followed by the Acheloos. Of all examined rivers, the Drin shows a maximum DIN, followed by Evros, Evrotas, Kamchia and Axios. The Drin also exhibits the highest nitrate concentration, followed by Evros, Pinios and Axios. These rivers score ‘bad’ in nitrate quality according to a classification system developed by Skoulikidis et al. (2006). The lower Aoos (in Albania), Evrotas and Strymon exhibit ‘poor’ nitrate quality status. Nestos, Kamchia, Alfeios, Aliakmon and Neretva present a ‘moderate’ and Acheloos and Aoos (in Greece) a ‘good’ status. Concerning nitrite, Evros, with a maximum concentration, has a ‘bad’ status, followed by lower Aoos (in Albania), Axios, Kamchia and Evrotas which have ‘poor’ status. The Drin, Strymon, Nestos, Pinios, upper Aoos (in Greece) and Aliakmon are classified as ‘moderate’, while Acheloos, Evrotas, Alfeios and Neretva have ‘good’ status. Maximum ammonia levels place Kamchia in ‘poor’ status and Aliakmon, Evros, Axios, Nestos, Strymon, Pinios and Evrotas in ‘moderate’ status, while the rest of the rivers (Alfeios, Evrotas, Aoos/Vjose, Acheloos, Drin and Neretva) have ‘good’ status. The ammonia share of DIN in the

TABLE 11.4 Water quality characteristics of the Balkan Rivers River Aliakmon

Evros

Axios

Nestos

Pinios

Strymon

Acheloos

Aoos

Sperchios

Station Ilarion

Dikea (near border)

Brige Axioupoli (near border)

Papades (near border)

Larisa

Rupel (near border)

Downstream Kastraki reservoir

Konitsa brige

Basin average

DO (mg/l)

N–NO3 (mg/l)

N–NO2 (mg/l)

N–NH4 (mg/l)

TP (mg/l)

DIN (mg/l)

Average Median Range Count Period

10.9 11.0 6.0–14.5 192 1980–95

0.68 0.49 0.005–3.64 240 1980–00

8 5 0.09–137

140 23 2.3–13246

20 10 1–118

0.82 0.52 0.007–17

Average Median Range Count Period

8.9 9.4 1.2–12.5 78 1980–95

3.47 3.18 0.02–22.4 91 1980–01

165 18 0.30–3729

668 555 65–2668

3.74 3.23 0.02–27.8

Average Median Range Count Period

9.7 10.0 2.2–13.5 228 1980–95

1.86 1.62 0.004–5.1 240 1980–00

60 6 0.30–1704

634 506 26–4359

2.01 1.67 0.006–7.96

Average Median Range Count Period

9.8 10.0 3.1–13.2 220 1977–95

1.24 1.04 0.02–5.78 250 1980–01

14 5 0.30–164

136 111 10–627

1.34 1.08 0.03–7.03

Average Median Range Count Period

10.5 10.7 1–14 201 1979–95

1.92 1.60 0.08–12.1 241 1979–00

13 8 0.30–213

77 65 2–340

1.99 1.64 0.08–13

Average Median Range Count Period

10.0 10.2 2.6–13.4 192 1980–95

1.46 1.30 0.30–5.40 264 1980–01

16 2 0.30–312

144 114 18–1255

1.54 1.33 0.31–6.14

Average Median Range Count Period

10.9 11.0 6.0–13.7 192 1980–95

0.32 0.18 0.004–4.85 252 1980–01

7 4 0.30–79

21 10 0.51–663

0.37 0.21 0.01–5.36

Average Median Range

10 10.1 6–15.2

<0.22 <0.1 <0.1–2.20

10 64 <0.3–47

<36 <19 <19–222

19.6

<0.27 <0.18 <0.12–2.47

0.75

5.2

83.2

15.2*

Source, period (comments)

180 1980–94 105 31 0.67–1675 91 1980–94 87 44 1.9–1154 192 1980–95 84 36 3.9–1089 190 1980–95 63 36 6.2–709

HMRDF (interpolated data)

181 1979–94 63 33 7.8–436 192 1980–95 43 26 4.7–424 180 1980–94

0.89

HME 1984–87 Dassenakis et al. 2005

Floka dam (near mouth)

Average Median Range

10.1 10.1 8–12.2

0.69 0.70 <0.1–1.30

<5.5 <3.6 0.00–44

<54 <19 <19–222

<16 <10 <10–65

<0.74 <0.73 <0.12–1.57

Evrotas

6 stations

Average Median Range

8.9 9.0 6.6–11.8

1.21 1.17 0.43–2.26

21 16 5–75

65 50 30–172

<21 <18 <10–71

1.30 1.24 0.46–2.51

Drin

A1RV2 (near L Shkodra)

Average Median Range

8.6 8.6 2–12

4.60 1.465 0.035–12

16.3 16.3 1–65

37.75 35.25 10–80

36 31 9–90

4.65 1.52 0.046–12.2

Vjose

A1RV20 (near mouth)

Average Median Range

8.9 8.9 6.1–10.4

1.71 1.67 0.01–6.8

63.8 14.3 1–1200

44.3 51.5 12–210

29.1 28.9 12–75

1.82 1.73 0.02–8.21

28 066 (near mouth)

Average Median Range

7.15 7.56 4.6–8.5

1.23 1.03 0.65–2.81

49.5 44.1 21.3–107

737.7 484.5 124–1480

337.5

2.02 1.55

0.80–4.40

Average Median Range

9.78 9.9 5.1–12.1

0.62 0.59 0.27–1.01

5.7 39 2.5–20

37 28 5–160

28.4667 26.6667 0.005–0.08

Alfeios

Kamchia

Neretva

40 159 (near mouth)

HMRDF: Hellenic Ministry of Rural Development and Food, HME: Hellenic Ministry for the Environment, Physical Planning and Public Works. *

P–PO4.

0.66 0.66 0.28–1.19

HME 1983–97

Nikolaidis et al. 2006 (May, September 2006) EIONET 1994–01

EIONET 1995–05

EIONET 1992–04 (yearly data)

EIONET 2003–05 (yearly data)

448

FIGURE 11.5 Average nutrient concentrations of Balkan Rivers.

examined rivers shows dramatic variation. In the Drin, the ammonia proportion is minimum (0.7–1.1%). In Neretva, a 10-fold downstream ammonia concentration increase is evident (0.5% in Bosnia and Herzegovina and 5.6% in Croatia). In the majority of Greek rivers (Evros, Nestos, Strymon, Axios, Pinios, Alfeios) the ammonia share of DIN ranges between 2% and 6%. The Acheloos, Aoos and Aliakmon show higher ammonia portions (12–17%). In Bulgarian river stretches, ammonia comprises even higher proportions (21– 23% in Nestos, Strymon and Kamchia, 25–28% in Evros, Tundja and Arda), indicating municipal wastewater impact. The Axios in FYR Macedonia shows the maximum ammonia portion (44%), reaching 75% and 89% downstream of Skopje and Veles, respectively. The organic fraction of total dissolved nitrogen is 40% in the lower Acheloos, 50% in the upper Aliakmon and 65% in the upper Drin, while in rivers heavily affected by inorganic fertilizers the organic fraction decreases; 33% in T66 (Aliakmon-ditch), 35% in lower Axios and 11.5% in lower Strymon (Voutsa et al. 2001; Skoulikidis et al. 2001; Ovezikoglou et al. 2003; Borgvang et al. 2006). Rivers of zone 3 (Alfeios, Evrotas, Aoos, Acheloos) have the lowest total phosphorus (TP) concentrations. These rivers, along with Aliakmon, Neretva, Vjose, Drin and Pinios, belong to a ‘high’ quality class concerning TP. Strymon and Nestos have ‘good’ TP status, Kamchia ‘poor’ and Evros with Axios a ‘bad’ status. The organic fraction of TP comprises 62% in Acheloos, 50% in the upper Aliakmon, 54% in the upper Drin and 51% in the Axios (Greece) (Voutsa et al. 2001; Ovezikoglou et al. 2003; Borgvang et al. 2006). In the lower parts of the Acheloos, Aliakmon, Neretva and Drin, the organic P fraction ranges between 57% and 75%, indicating organic inputs of upstream reservoirs, while the high portion in Evros (70%) is attributed to organic pollution. In general, nutrients exhibit a downstream increase in their concentrations caused by a respective increase in human pressures with some exceptions due to the contribution of local point pollution sources. A notable exception is the Neretva River, where the TP concentration shows an upstream increase. Due to municipal wastewater impacts, the

PART | I Rivers of Europe

Drin tributaries in the area of Lakes Prespa and Ohrid show relatively high nutrient concentrations tending towards a ‘moderate’ quality. In addition, Lake Ohrid is being enriched with nutrients through underground inputs from Lake Prespa (ILEK 2005). Further downstream near the mouth, ammonia and nitrite levels decline while nitrate and phosphate increase (Borgvang et al. 2006) indicating impact of inorganic fertilizers. The headwaters of Aoos show very low DIN and P–PO4 levels of 0.03 mg/L and 5 mg/L, respectively (Chatzinikolaou et al. 2007). Upstream and midway sections, along with the Drino and Shushica tributaries, and despite a 10-fold DIN and a 3-fold TP increase relative to headwaters, maintain a ‘high’ quality. Kamchia has a relative degradation in quality downstream of Preslav with further increases downstream of Shumen, while the inflow of Luda Kamchia upgrades its quality. In rivers entering Greece from Bulgaria and FYR Macedonia, there is a steep increase in nitrate concentration, along with a respective decrease in ammonia concentration (e.g. Evros, Nestos and Strymon). Nitrate-pollution sources between the border stations are insignificant, and because it is unlikely that ammonia nitrification alone can account for the observed differences it seems probable that different techniques and methodologies are employed in the different states. In the Evros, below Kostenec, nutrient quality turns gradually to ‘bad’. DIN levels at the Bulgarian part range between 0.28 (near the source, i.e. upstream of Kostenec) and 6.1 mg/L (below Dimitrovgrad), while P–PO4 levels range between 10 (near the source) and 410 mg/L (below Harmanli). Ammonia reaches high levels, with maximum concentrations below Dimitrovgrad (1.56 mg/L N–NH4) and Harmanli (1.32 mg/L N–NH4), indicating municipal wastewater discharge. At the delta, autumn flushing causes high nutrient concentrations (N–NO3 exceeds 4 mg/L and P–PO4 almost reaches 700 mg/L) (Angelidis & Athanasiadis 1995), indicating agricultural impacts. In Tundja, ‘poor’ to ‘bad’ nutrient quality prevails. At its downstream section, below the industrial city Jambol, aquatic quality deteriorates. It improves slightly downstream Elhovo and even more before entering the Evros, although retaining ‘bad’ quality. In the Arda, nutrient quality ranges between ‘good’ and ‘moderate’. In the Bulgarian part of Nestos, ‘moderate’ quality prevails. Nitrate and phosphate levels decrease along the Greek stretch and, as a result of agricultural impacts, they increase again in the delta area. The quality of Strymon, below the Pchelina reservoir, in general presents ‘poor’ nutrient status (EIONET, Voutsa et al. 2001), while in the Bulgarian portion ‘bad’ TP quality dominates. The Axios shows also an exceptional spatial pattern, with nutrient maxima at its mid-reach, due to point source pollution from the towns of Skopje (organic chemical plant, municipal wastes) and especially Veles (fertilizer industry, municipal wastes), where average N–NH4 reaches 10.9 mg/L and TP 16 mg/L. Downstream and along the Greek stretch, water quality improves due to a reduction of point sources, except

Chapter | 11 Rivers of the Balkans

nitrate which increases as a result of intense agricultural activities. The Aliakmon headwaters and mountainous tributaries show ‘high’ nutrient status. Along the main stem, nutrient quality ranges between ‘good’ and ‘moderate’ status, while the Lake Kastoria canal has a ‘bad’ status (Skoulikidis et al. 2002a). Within T66 and downstream of its confluence to the river, the nutrient quality turns to ‘bad’ (DIN 4.9 mg/L, TP 630 mg/L; Voutsa et al. 2001). Along the Pinios main stem, ‘bad’ nitrate and ‘poor’ phosphate quality predominate, while tributaries show ‘bad’ nitrate quality and ‘good’ to ‘moderate’ phosphate quality (data: Stamatis 1999, Fytianos et al. 2002). In its upper and midway portions, the Acheloos shows ‘high’ nutrient status (data: Ovezikoglou et al. 2003), while the lower part shows ‘good’ quality for N-compounds and ‘high’ quality for phosphate (Skoulikidis et al. 2002b). Along the Sperchios, nutrient levels range between ‘good’ and ‘moderate’ status (data: Dassenakis et al. 2005). Nutrient levels along the Alfeios indicate ‘good’ to ‘high’ quality. The tributaries (Elisson, Lousios and Ladon) are of ‘high’ status. Aquatic quality slightly deteriorates below Megalopolis to improve again downstream (data: Skoulikidis et al. 2000). In the Evrotas, there is a downstream deterioration of Ncompounds from ‘good’ to ‘moderate’ status, whereas a quality improvement at the mouth is attributed to dilution due to karstic inflows. Concerning P constituents, the river shows ‘high quality’ (Nikolaidis et al. 2006). In general, Balkan rivers are enriched with nitrate in winter (December–February) as a result of arable land flushing (in the Aliakmon mainly in autumn), while dilution during spring and insignificant nitrate point discharges in summer keep nitrate concentrations low (Skoulikidis &

FIGURE 11.6 Long-term variation of nutrient concentrations in selected Balkan Rivers.

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Kondylakis 1997). Some rivers (e.g. Evros, Strymon and Aliakmon) show an increase in nitrate concentration with discharge, indicating the prevalence of flushing processes, while others (e.g. Axios, Nestos, Acheloos) show a decreasing trend with discharge, indicating the prevalence of dilution processes (see Figure 11.4). TP exhibits maximum levels at the rising limb of the hydrograph (mainly October, for Pinios in November) due to initial flushing. Ammonia peaks that occur in winter or spring may be attributed to organic matter mineralization. Increased TP and ammonia levels during low flow originate from municipal and industrial (e.g. seasonal food processing industries) effluents, although prevalence of denitrification processes (e.g. in the Pinios by standing waters) cannot be excluded. Regarding long-term nutrient variation (Figure 11.6), during the initial period of measurements, the Evros, Nestos, Strymon and Axios show a gradual increase in nitrate concentration reflecting agricultural intensification. In the dry period (end of the 1980s – beginning of the 1990s), all four rivers show a concentration increase. In the Evros, a decreasing trend is evident after 1991. In the Nestos, Strymon and Axios, after a decrease in the mid-1990s, nitrate increased again to reach the multi-year maximum in 1997–1998 and since then gradually diminished. The Kamchia shows peak nitrate values in 1997 and 2001. The Evros, Nestos, Strymon and Axios show maximum TP concentration in 1982. In the Evros and Axios, a second peak appears in 1990 that coincides with minimum discharge. After 1982, TP shows a clear decrease in the Nestos, a slight decrease in the Strymon, an increase in the Axios and no clear trend in the Evros. In the Kamchia, TP concentration increased in 1995–1997 and thereafter gradually decreased, with a peak in 2001, being also evident in the Neretva. According to the Directive 75/440/EC regarding the quality of drinking waters, the Aoos, Arachthos, Acheloos, Alfeios, Evrotas, Strymon, Nestos and Lakes Prespa and Doirani satisfy the conditions for their classification at A1 class. The Pinios, despite occasionally high nitrate and phosphorous concentrations, satisfies the conditions for its classification as A2 category, while the Aliakmon marginally meets drinking water criteria. The Axios generally satisfies the Directive’s conditions, despite occasional high nitrate, ammonia and phosphorous concentrations, while the Evros is marginally classified as A3 category (HME 2006). The other Balkan countries apply national criteria concerning water quality for different uses (drinking, swimming, recreation). The pollution of Greek rivers from compounds of List II referred to in Directive 76/464/EC, and other toxic compounds, shows low concentrations of VOCs and insecticides, whereas the concentrations of herbicides and metals generally range around moderate levels. Elevated concentrations occur in a number of cases due to a variety of factors including intense agricultural applications, meteorological events, industrial effluents, mining activity and the geochemical background (Lekkas et al. 2004). Regarding pesticides, the

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most polluted rivers are the Axios and Aliakmon. S-triazines, amide herbicides and organophosphorous insecticides are the most frequently detected, while organochlorine pesticides (banned in Greece in 1972) occur at very low concentrations (Konstantinou et al. 2006). The highest levels of organochlorines, occasionally exceeding the EC qualitative standards (Directive 76/464/EC), were detected in transboundary water bodies, especially near the borders (Evros, Nestos, Strymon, Axios, Small Prespa, Doirani) denoting transboundary pollution (Golfinopoulos et al. 2003; Lekkas et al. 2004; Konstantinou et al. 2006). In Axios, lindane (phased out in Greece since 2002, according to Directive 2000/801/EC) was detected in 100% of the samples at the entrance of the river to Greece, demonstrating the impact of lindane manufacturing in Skopje (Konstantinou et al. 2006). Concerning insecticides, methyl parathion, parathion (withdrawn since 2003 and not found in recent investigations) and diazinon were compounds previously detected in most Greek rivers, followed by fenthion, carbofuran and malathion. The highest insecticide levels were recorded for the Axios (up to 2000 ng/L for malathion, parathion and pyrazophos, 362 ng/L for parathion methyl and 7300 ng/L for carbofuran), while fenthion’s maximum was observed in Evrotas (Konstantinou et al. 2006). Several organophosphorous insecticides were detected, mainly in the Evros, Nestos, Strymon, Aliakmon, Acheloos, Pinios, Alfeios and Lake Prespa. Regarding herbicides, atrazine, simazine (withdrawn in Greece since 2004), metolachlor, alachlor and prometryne were most frequently detected (Lekkas et al. 2004; Konstantinou et al. 2006). The highest concentrations of simazine (117 ng/L) and cyanazine (63 ng/L) were found in Strymon (Lekkas et al. 2004), of prometryne in Aliakmon (6100 ng/L) and of propanil in Axios (20 600 ng/L) (Konstantinou et al. 2006). Captafol, captan, chlorothalonil, metalaxyl, flutriafol and vinclozolin were the fungicides found in the Axios, Aliakmon, Nestos and Evrotas (Konstantinou et al. 2006). VOCs exhibit low concentrations, with higher levels and greater variety detected in the Axios and Stymon. Hexachlorobutadiene exceeded the quality target level (0.1 mg/L) in the Axios, Strymon, Nestos and Pinios. In the transboundary rivers, a number of VOCs presented elevated concentrations near the border (e.g. 4-chlorotoluene and napthalene in Strymon, 1,1,2-trichloroethane in Nestos) denoting transboundary pollution, while others (e.g. 1,3-dichlorobenzene in Strymon) were attributed to Greek sources (Nikolaou et al. 2002). Despite the high geochemical background, riverine heavy metal levels (for world averages see Salbu & Steinnes 1995) are generally low (Lekkas et al. 2004). According to Lekkas et al. (2004), the highest toxic metal concentrations are present in the Strymon (6.39 mg/L As), Evros (9.17 mg/L Pb; world average 1 mg/L), Axios (43.6 mg/L Zn; world average 30 mg/L, 1.15 mg/L Al), Pinios (40.3 mg/L Cr, 51.1 mg/L Ni; world average 2.2 mg/L, 5.35 mg/L Co, 23.7 mg/L Cu; world average 10 mg/L) and L. Doirani, which generally shows elevated geogenic heavy metal concentrations, especially for As (51.5 mg/L). The

PART | I Rivers of Europe

Alfeios has high Fe and Mn levels (5.7 and 0.26 mg/L, respectively). Finally, Cd concentration distribution in core sediments of the Axios and Aliakmon reveal high anthropogenic flux in recent decades (Samanidou et al. 1991).

11.7. RIPARIAN AND AQUATIC BIODIVERSITY 11.7.1. Riparian Vegetation Mountainous areas still contain surprisingly undisturbed and often isolated river valleys, in particular close to political borders. Western tributaries of the Evros are covered by closed mixed and deciduous forests (e.g. eastern slopes of the Rhodope Mts along the border of Greece and Bulgaria). They are often a ‘secondary wilderness’ as a result of recent depopulation and cultural abandonment and provide speciesrich riparian habitats including residual alluvial alder forests (Alnion glutinoso-incane) and the rare willow Salix xanthicola listed by Greece’s Red Data Book (Phitos et al. 1995). The rivers in the western and southern peninsula often have similar but structurally varied montane riparian vegetation. For example the Aoos headwaters drain a unique plateau (1400 m asl) in the northern Pindos Mts that has been used for centuries as the summer grazing area by the Vlach shepherds. There, the riparian vegetation is disturbed by grazing forming scattered scrublands with willows and forbs as well as humid montane grasslands. All other headwater tributaries are steep and often colonized by Black Pine forests down to the edge of streams. Further downstream along the river valleys, Mediterranean mountain vegetation develops. Platanus orientalis is the most ubiquitous tree species along Balkan rivers, especially in the western and southern peninsula. In the Acheloos, the tree begins forming stands at about 1100 m elevation and continues along the length of the river until its delta in the Ionian Sea. In open depositional reaches, thickets of Salix eleagnus are characteristic throughout the western Balkans (Figure 11.7). The Upper tributaries of the Arachthos drain flysch badlands where landslides are frequent. These badlands create unique riparian zones with narrow wooded strips of Oriental Plane, alders and willows. The 30 km long Arachthos Gorge provides another spectacular area with high forest diversity including remarkable sclerophyll woods of holm oak; and, locally Laurel Laurus nobilis forms thickets beneath ancient Oriental Plane stands. In the southeastern Peloponnese, for example along the Evrotas River, many headwater streams are ephemeral or intermittent and fringed by open and linear riparian vegetation. The ubiquitous Oriental Plane is a longrooted phryatophyte that reaches the groundwater table even during the long dry summer.

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FIGURE 11.7 Natural longitudinal distribution of key riparian tree species along the Acheloos and Alfeios Rivers, Western Greece. The lower-middle and lower courses contain diverse hydrophilous tree communities because of extensive floodplain development and the presence of karstic springs that create perennial wetlands. Note, the extensive longitudinal dominance of the Oriental Plane (Platanus orientalis).

11.7.2. Lowland Riparian Woods

11.7.3. Deltaic Communities

Today, natural lowland riparian forests are rare in the Balkans and they are among the most threatened natural woodland types. Traditionally, wood cutting for rural and house hold use was intense along rivers, and is still commonly practiced in Albania. Only few lowland sections have escaped widespread degradation. Extensive riparian forests are rare and localized, one such remnant exists along the lower Kamchia. Along the Evros, intact riparian forests, including poplar-willow stands and small riverine wetlands that serve as refuges for the riparian flora and wildlife, remain along the Greek-Turkish border. One of the most famous lowland riparian hardwood forests in the Balkans is in the Nestos delta, the so-called Kotza Orman (Gerakis et al. 2007). In the western Balkans important lowland forests are present along Lake Shkodra and at Fraxos in the Acheloos Delta. However, in most areas hardwood hygrophilous woods with ash or oak are extremely rare and often only small plots of surviving trees remain. Overall, the proportion of alien riparian plant communities is lower in the Balkans than in Western Europe and Western Mediterranean (Zogaris et al. 2006). Some former lowland riparian forests in the southern Balkans (e.g. lower Alfeios and some Evrotas tributaries) have been replaced by Eucalypt plantations. In the northern and central Balkans, hybrid poplar plantations and species such as Robinia pseudacacia, Amorpha fruticosa are now widespread. The Treeof-Heaven Ailianthus altissima is also a widespread alien species in the proximity to settlements in lowland areas. In lowland areas, the invasive Giant Reed Cane Arundo donax covers disturbed and deforested streams and canals. These dense bamboo-like thickets impede the regeneration of willow and other riparian plants.

The extensive Balkan river deltas are famous for their diverse plant communities (Szijj 1981). Plant richness can be up to 300 to 400 species per delta (Sarika et al. 2005). The deltas of the Eastern Balkan are the richest because they contain elements from Asia or Eastern Europe (e.g. Iris orientalis in the Evros delta). Most rare species have a circum-Mediterranean distribution but are often constrained to certain freshwater wetland types. Sedge habitats, freshwater pools and wet grasslands are of outstanding local conservation importance. Species listed as vulnerable, such as Trapa natans, are found in lentic waters of the Lakes Prespa and Kerkini. Even formerly widespread species are today either patchy or local in their distribution and frequently listed as threatened (e.g. Isoetes histrix in Lake Prespa, Cladium mariscus in the Arachthos Delta and Ludwigia palustris in the Neretva and Acheloos Deltas). The large western Balkan deltas share similar landscape features (Koumpli-Sovantzi 1983; Sarika et al. 2005). The deltas are bounded by limestone hills, islets and large lagoons with barrier spits along the shore. Rich hydrophyte communities including Potamogeton spp., Myriophyllum spp., Polygonum sp. and helophytes (extensive reeds of Pragmites australis, Scirpus spp., Carex spp. and Typha spp.) cover the main river channel. Complex riparian galleries (Salix spp., Populus spp., Ulmus minor, P. orientalis, Fraxinus sp.) fringe the deltas. Deciduous scrubs, such as Tamarix spp., cover brackish coastal lagoons while Chaste Trees (Vitex agnuscastus) prevail along inland freshwater wetlands. Halophilous dwarf scrubs (Salicornia spp., Arthrocnemum spp., Halocnemum spp.) often form extensive steppes in river mouths and coastal saltmarshes. Along sandy shores, ammophilous associations form shifting dunes colonized by Ammophia arenaria, Agropyrum mediterraneum, Cakile maritime and are fringed by pine forests and juniper thickets. In shallow coastal

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areas, marine angiosperms such as Zostera and Cymodocea and the Neptune Grass Posidonia oceanica (in clear waters) form extensive sea meadows. The eastern Balkan deltas are geomorphologically more diverse. A unique formation is the estuarine mudflats in the Sperchios delta, the largest in the entire Aegean.

11.7.4. Ichthyofauna The Balkan Peninsula hosts a rich freshwater ichthyofauna with a high proportion of endemic species. It is considered as one of the world’s biodiversity hotspots (Peter 2006). The number of freshwater fishes is the highest in Europe, although estimates of richness vary. The Croatian rivers flowing to the Adriatic Sea host 88 species (Radovic et al. 2006). More than 135 species have been reported from Greece (Bobori & Economidis 2006). This number will further increase, because the taxonomy of many groups is under revision and new endemic species are still being discovered (Kottelat 1997). Out of 198 known Balkan fish species, 81 are listed as threatened or endangered by IUCN. Many of the more restricted species are declining in number. An even larger and yet poorly explored diversity exists at the subspecies level with unique phenotypes and genetic profiles (for salmonids: see Apostolidis et al. 1997; Bernatchez 2001; Snoj et al. 2002). The high level of endemism is a result of the complex geological history of the area in combination with distinct environmental gradients as well as past climatic changes. A well-accepted hypothesis of the origin and diversity of the Balkan ichthyofauna postulates that the Euro-Siberian and Palaearctic species colonized the area during the Oligocene and Miocene through river captures. The Alpine orogeny and the uplift of the Balkan Mts gradually isolated this area from the rest of Europe and additionally cut connections between the eastern and western Balkan drainages (Economidis & Banarescu 1991). Another hypothesis explains the colonization of freshwater species around the circum-Mediterranean during a short period in the late Miocene, when the Mediterranean dried and then was refilled with freshwater entering from the Paratethys (Bianco 1990). In any case, the area retains elements of the ancestral European

ichthyofauna that were lost in most other parts of the continent during the Pleistocene glaciations. From an ichthyogeographical perspective, two major divisions are recognized in the Balkans: the Ponto-Caspian and the Western Balkan. These divisions are biogeographically distinct because mountain boundaries form old barriers to fish dispersal. The Western Balkan rivers are dominated by relatively depauperate but endemic-rich assemblages that have experienced long periods of isolation. The rivers of the Ponto-Caspian division are more species-rich because many fish of Black Sea and Danubian origin intruded into this area during the Pliocene and Pleistocene when the Black Sea still was a freshwater lake. Opinions differ over the existence and delineation of additional freshwater biogeographic divisions and subdivisions (e.g. Bianco 1990; Economidis & Banarescu 1991; Stephanidis 1939; Maurakis et al. 2001). Economidis & Banarescu (1991) distinguished four main ichtyogeographic divisions: the Ponto-Aegean (with the subdivisions of Eastern Bulgaria, Thracian-East Macedonia and Macedonia–Thessaly), the Attiko–Beotia, the Dalmatian and the South Adriatic–Ionian divisions (Table 11.5). These divisions account for the long-term isolation of the Ionian from the Adriatic drainages as reflected by the presence of unique species endemic to both areas. The Ponto-Aegean division includes rivers flowing into the Black and Aegean Seas down to the Pinios River. The East Bulgarian subdivision, with its distinct influence from the Danubian and central European fauna, contains no endemic freshwater species, although there are brackish and anadromous species endemic to the Black Sea (Neogobius, Alosa spp). The ichthyofauna of the Kamchia includes species typical of the Danubian ichthyofauna (e.g. Aspius aspius, Squalius cephalus, Petroleuciscus borysthenicus, Barbus barbus, Chalcalburnus chalcoides, Gobio gobio, Alburnus alburnus and Alburnoides bipunctatus; see Karapetkova et al. 1993; Vassilev 1999). The Thracian-East Macedonian subdivision includes the 32 native fish species in the Evros and 36 in the Strymon (Table 11.1). It is postulated that their fish fauna entered from the Black Sea during its freshwater phase in the Pleistocene (Economidis & Banarescu 1991). Few taxa with AnatolianAsian affinities are represented by endemic species or

TABLE 11.5 Main ichthyogeographic divisions and subdivisions in the Balkans (in bold: rivers described in this book) Main divisions

Subdivisions

River catchments

Ponto-Aegean

East Bulgaria Thracian – East Macedonia West Macedonia – Thessaly

Kamchia, Ropotamo, Rezubtska, Veleka, Mandra Evros, Nestos, Strymon, Filiouris, Loutros, Marmaras, Vospos, Kosinthos, Kompsatos Axios, Aliakmon, Pinios (Thess.), Gallikos, Loudias, Sourporema

Attico–Beotia West Balkans

Sperchios, Kifissos, Assopos (mainland only) Dalmatian Adriatic Ionian

Neretva, Mirna, Lika, Zrmanja, Krka, Cetina, Soca Drin, Aoos (Vjose), Seman, Skumbi, Erzen, Ishmi, Matia, Buna Acheloos, Arachthos, Alfeios, Evrotas, Thyamis, Acheron, Louros, Krathis, Foinix, Piros, Mornos, Evinos, Pinios (Pelop.), Pamissos, Neda, Peristras, Velikas

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subspecies: Cobitis strumicae, Barbatula bureschi and B. cyclolepis (with the endemic subspecies B. c. cyclolepis in the Evros and B.c. strumicae in the Nestos and Strymon). There are few local endemic species such as Cobitis punctilineata (Strymon) and Squalius orpheus (Evros River). The fishes of the Western Macedonia–Thessaly subdivision belong to the Danubian faunistic complex and are most likely have colonized the area through a postulated Pliocene–Pleistocene river capture involving the Axios and Morava (Danube River tributary) (Economidis & Banarescu 1991). Fishes shared with the Danube basin include A. bipunctatus, A. alburnus, Rutilus rutilus, G. gobio, Gasterosteus aculeatus and Silurus glanis. A number of other fishes stemming from Danubian lineages have evolved endemic forms (Barbus macedonicus, Cobitis vardarensis, Gobio banarescui, Romanogobio elimeius, Pachychilon macedonicum, Chondrostoma vardarense, Vimba melanops, Squalius vardarensis and Zingel balcanicus). The rivers of mainland portion of the Attiko-Beotia division contain a depauperate freshwater fish fauna with distinctive endemics (e.g. Barbus graecus, Pseudophoxinus marathonicus) (Economidis 1995). The Sperchios River contains the locally endemic species P. hellenicus, confined to spring-fed wetlands of alluvial floodplains. The Western Balkan division drainages have remained isolated perhaps since the Miocene and are inhabited mostly by endemics. The Dalmatia subdivision encompasses a number of small and medium-sized rivers that drain Slovenia, Croatia, Bosnia and Herzegovina and parts of Montenegro. The shallow northern Adriatic Sea most likely dried during the last glacial maximum and several rivers had joined confluence allowing a faunal exchange among rivers of the Northern Adriatic and the Italian coast. In the Neretva, this group of fishes include the cyprinids Chondrostoma knerii, Squalius microlepis, Squalius svallize, Phoxinellus adspersus and Rutilus basak, the salmonids Salmo marmoratus and Salmo (Salmothymus) obtusirostris, the gobiid Knipowitschia croatica and the lamprey Lethenteron zanandreai (see Mrakovcic et al. 1995, 2002; Brigic et al. 2004). Two recently described species (Phoxinellus pseudalepidotus (Bogutskaya & Zupancic 2003) and Knipowitschia radovici (Kovacic 2005)) are endemics to the Neretva. Characteristics for the Dalmatian ichthyofauna are the high degree of diversification within the genus Phoxinellus (Bogutskaya & Zupancic 2003) and the existence of high morphological and genetic diversification among salmonid taxa (Glamuzina & Bartulovic 2006). The Adriatic and Ionian subdivisions were considered by Economidis & Banarescu (1991) to comprise a single ichthyogeographic region (the Southern Adriatic–Ionian Division). However, Bianco (1986) argued convincingly that the Adriatic and Ionian drainages host different fish faunas and proposed their separation. The Adriatic subdivision, delineated to the north by the Drin and to the south by the Aoos, is rich in endemic fishes (for faunistic descriptions see Spirkovski 2003; Crivelli et al. 1997; Rakaj & Floko 1995).

The Drin river system alone (including the associated Lakes Ohrid, Prespa and Skadar) contains more than 30 endemic freshwater fish species. Lakes Ohrid and Prespa are geologically old (Plio-Pleistocene) and as such they accommodate several local endemic species and subspecies (Ohrid: Salmo (Salmothymus) (Acantholingua) ohridanus, S. letnica, Pseudophoxinus minutes and Rutilus ohridanus; Prespa: Chalcalburnus belvica, Chondrostoma prespense, Barbus prespensis, Cobitis meridionalis, Phoxinellus prespensis and Rutilus prespensis). Two additional species endemic to the Drin have been recently described: Scardinius knezevici (Bianco & Kottelat 2005) and Eudontomyzon stankokaramani (Holcik & Soric 2004). Two Dalmatian salmonids are also found in the Drin: S. marmoratus and S. obtusirostris. The Ionian subdivision encompasses the drainages between the Thyamis and Evrotas and represents a long-term isolated area with a high proportion of endemic species (Economou et al. 1999). Two genera containing two species each are endemic to the Ionian drainages (Tropidophoxinellus and Economidichthys). Danubian and European genera typically present in other Balkan regions are absent (e.g. Chalcalburnus, Chondrostoma, Barbatula, Gobio, Alburnus, Alburnoides, Phoxinus, Cottus and Rhodeus). The Acheloos contains 22 native fishes including many lacustrine and fluvio-lacustrine forms that have probably descended from morphotypes inhabiting the ancient lake Aetoloacarnania. Six species of the Acheloos are locally endemic (Scardinius acarnanicus, Rutilus panosi, Silurus aristotelis, Salaria economidisi, Cobitis trichonica and Economidichthys trichonis) and eight species are endemic to the Ionian subdivision (Barbus albanicus, Tropidophoxinellus hellenicus, Pseudophoxinus stymphalicus, Barbus peloponnesius, Squalius peloponnensis, Economidichthys pygmaeus, Telestes pleurobipunctatus and Valencia letourneuxi). The Evrotas in the south has a depauperate native fish fauna (four species) with three species endemic locally or to southern Peloponnese (Squalius keadicus, Pseudophoxinus laconicus and Tropidophoxinellus spartiaticus).

11.7.5. Macroinvertebrates For most Balkan rivers, the taxonomy and distribution of benthic macroinvertebrates have been poorly documented. In Bulgaria, Serbia and Montenegro their identification is often possible to the species level although available information is restricted to specific catchments (e.g. Vidinova 2003; Bauernfeind 2003; Maurakis et al. 2004; Vidinova et al. 2006; Petrovic et al. 2006). In Greece, identification at the species level remains difficult due to lack of appropriate taxonomic keys. As a result, suitable data to evaluate the state of rare, endangered, or protected species are often absent. Two riparian butterfly species (Lycaena dispar and Apatura metis), listed in the Annexes of the EU Habitat Directive, are still locally common along the Evros, Aoos and other central Balkan rivers. Other freshwater species protected by the Directive

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include the mussels Margaritifera margaritifera and Unio crassus. The benthic fauna is widely used to assess the quality of freshwaters (Ghetti 1997). Thus, many inventories have been carried out for the southern Balkan rivers (Vourdoumpa 1999; Lazaridou-Dimitriadou 2002; Kampa et al. 2002; Iliopoulou-Georgoudaki et al. 2003; Skoulikidis et al. 2004; Gritzalis et al., 2006). Ephemeroptera, Plecoptera and Trichoptera (EPT-taxa) are used as sensitive indicators for (organic) pollution. The pristine or slightly polluted mountainous sections of the Alfeios, Aliakmon, Aoos, as well as the tributaries Nestos and Strymon are dominated by the taxa Rhithrogena lisettae, Ecdyonurus spp., Heptagenia spp., Epeorus spp., Taeniopteryx sp., spp., Habrophlebia spp., Choroterpes spp., Dinocras spp., Perla spp., Dictyogenus spp., among many others. In the more degraded lower sections, the diversity and abundance of EPT-taxa is usually much lower. The lower Axios (Kampa et al. 2002), Alfeios (Vourdoumpa 1999), Louros, Arachthos and Evrotas rivers (Gritzalis and Skoulikidis unpublished data) are dominated by Baetidae, Caenidae, Nemouridae, Hydropsychidae, denoting degradation. Avifauna and human activities have led to a fast expansion of molluscs in Greece. Some gastropods (e.g. Ancylus fluviatilis, Acrolocus lacustris) attain high abundance in fast-flowing and macrophyte-free headwaters. Other gastropods (e.g. Lymnaea spp., Physa spp.) mostly occur in middle and lower river sections that are rich in fine sediments and macrophytes. Theodoxus spp., one of the most abundant genera in the southern Balkans, has been collected along all lowland river types. Bivalvia, such as Pisidium sp. U. crassus and M. margaritifera, are locally common in lowland sections. For instance, M. margaritifera has been recorded in the Acheloos and Aliakmon and Unio spp. occurs in large numbers in the Alfeios and Aliakmon (Gritzalis and Skoulikidis unpublished report). Odonates of the families Aeschnidae (Aeschna spp., Anax sp., Boyeria sp.), Corduliidae (Somatochlora sp., Cordulia sp.) and Libellulidae (Orthretrum sp., Sympetrum sp., Libellula sp.) are typically found in near-pristine sites. Coenagrionidae (Pyrrhosoma sp., Ischnura sp., Enallagma sp., Coenagrion sp.), Calopterygidae (Calopteryx splendens), Gomphidae (Onychogomphus sp., Gomphus sp., Ophiogomphus sp.), Lestidae (Lestes sp.) and Platycmenidae (Platycnemis spp.) include more tolerant species and therefore are common in the middle and lower river sections. Cordulegaster spp. is a rare species in Greece. Epallage fatime occurs only in the Alfeios and Pinios. Dipterans of the families Chironomidae and Simulidae usually inhabit low quality waters. Other Dipteran species like Atherix spp. live in areas with good water quality, while species of other families (Dixidae, Limoniidae, Psychodidae, Ceratopogonidae, Blephariceridae, Tipulidae, Empididae) appear in low numbers and rarely co-occur in the same sampling site. The most abundant coleopterans belong to the families of Elmidae, Hydrophlidae, Gyrinidae and Dytisci-

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dae. The Heteroptera (Corixidae, Gerridae, Veliidae and Notonectidae) prefer pool conditions and display tolerance to various pollutants (Karaouzas & Gritzalis 2006). In polluted sites, Hirudinea are encountered in large numbers, with representative species belonging to the families of Glossiphoniidae, Hirudidae and Erpobdellidae. The species Hirudo medicinalis is rare in the southern Balkans (except in the upper Aliakmon). As detritus feeders, the majority of Oligochaeta are usually found at the lower, and often polluted, river sections. Among the Crustacea, the Astacidae are a rare group found mainly in pristine areas, for example in a tributary of the Strymon in Greece and in the headwaters of the Aoos, where huge numbers of Astacus sp. occur. The Atyidae and Palaemonidae include typical representatives of the meta- and hypopotamon of Balkan rivers. They prefer vegetated habitats and exhibit a higher tolerance to increased salinity. Gammarus spp. (Amphipoda) prefers fast-flowing oxygenated streams, although they are occasionally observed in pools. Corophium orientale has been reported from the Evros Delta (Kevrekidis 2005). From observations in large Greek rivers (Aliakmon and Axios), Asselus spp. and especially Asselus aquaticus (Isopoda) are associated with low flow velocity, low oxygen and organic pollution. Finally, freshwater crabs of the genus Potamon spp. are common in the Balkans (Maurakis et al. 2004; Bechev 2004).

11.7.6. Reptiles and Amphibians The Balkan river valleys host diverse reptile and amphibian assemblages; species richness benefits from remarkable heterogeneity of habitat and climatic zones. The Evros River is characterized by a transitional fauna between Sub-Mediterranean and Mediterranean bioclimates, and its herpetofauna includes species from different climatic and biogeographic realms. Amphibians include the southernmost distribution of the fire-bellied frogs Bombina bombina. The lower Evros valley hosts one of the westernmost populations of the Ottoman viper Vipera xanthina. Both Greek and Hermann’s tortoises are abundant. During the long warm summer, many reptiles seek shelter in the humid riparian zones. The herpetofauna shows a remarkable distinction between the eastern and western parts of the Balkan peninsula (Sotiropoulos 2004). The herpetofauna of the eastern Adriatic and Ionian coast, including the Peloponnese, includes at least 10 species endemic to this area (e.g. Albanian frog Rana shqiperica, Epirus frog R. epiroticus) (Arnold & Ovenden 2002). Many reptiles are listed as protected, although they are locally common (e.g. the two native semi-aquatic terrapins are widespread in lowland rivers). The herpetofauna of the Acheloos includes at least 20 species listed as protected at the national, European, or international level. Along river corridors, a typical faunal ‘zonation’ from upland coldwater species (e.g. Alpine Newts, Fire

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Salamander, Yellow-Bellied Toads and Stream Frog) to lowland warm-water species (e.g. Spadefood Toads Pelobates syriacus) occurs (Bousbouras & Ioannidis 1997).

11.7.7. Birds Many birds are associated with lowland rivers, riparian habitats and wetlands. The headwaters of Balkan rivers host few obligate aquatic birds, mainly Dippers and Grey wagtails, although mature riparian woodlands are often rich in terrestrial forest birds. The middle river sections, especially areas with extensive braided channels, contain small populations of river-breeding species, in particular common sandpiper, little-ringed plover and white and grey wagtails. The lowland reaches are often exceptional rich in waterbirds including many obligate wetland birds. Natural river floodplain habitats are rare; although areas such as the Louros– Arachthos delta hold remarkable riverine wetlands that host large colonies of breeding cicconiformes and other waterbirds. The deltaic systems of the Axios, Drin and Evros still contain wide floodplains with islands, bars and river flats that provide nesting sites for shorebird and tern colonies. Threatened wetland-associated raptors, such as White-tailed Eagle and Lesser-Spotted Eagle, nest in riparian forests along larger rivers such as the Evros, Drin, Nestos and the lower Aliakmon. The deltas of the Kamchia, Evros, Nestos, Acheloos, the double-delta area of the Arachthos and Louros, as well as the Lakes Kerkini, Shkodra and Prespa contain rich bird faunas often with more than 300 bird species per site. These sites are of exceptional ornithological importance especially for migrating species. For instance, Lake Shkodra is the westernmost breeding site of the Dalmatian Pelicans and hosts the second largest colony of the Pygmy Cormorants worldwide (UN/EC 2007b). The Evros delta is renowned as an internationally important bird area; its value has often been compared to the much larger river deltas of the Danube, Rhone and Guadalquivir (Makatsch 1959; Handrinos et al. 2005). This international significance is mainly due to its strategic geographical position along the important migration flyway between Europe and Asia. The delta is only 70 km from the Dardanelles that forms together with the Bosporus a key migratory ‘bottleneck’ for millions of birds. The delta is also an overwintering area for many species from Russia and Scandinavia (Handrinos & Akriotis 1997). Although the number of breeding birds has recently declined due to habitat loss and anthropogenic degradation, many rare European species still breed including Ruddy Shelduck (Tadorna ferruginea) and Spur-winged Plover (Hoplopterus spinosus). In addition, the middle sections of the Evros in southern Bulgaria are also extremely important for rare and threatened birds. There, Mediterranean species and certain raptors find their northernmost distribution or have important local population strongholds (Stoychev & Petrova 2003). The Dadia– Lefkimi–Soufli National Park in Greece (lower Evros) is

renowned for a remarkable variety of rare breeding raptors (21 breeding species), including internationally important populations of Eurasian black vulture, griffon vulture, Egyptian vulture, white-tailed eagle and lesser-spotted eagle (Petrou 1993). Monitoring of wintering birds has shown a decline in some large raptors and waterbirds in the Balkans (Tucker & Heath 1994). This includes Lesser-Spotted Eagle, Great Bittern and Waterfowl such as Ferruginous Duck and several geese species (Handrinos & Akriotis 1997). Supported by direct and effective conservation efforts, some birds have maintained and increased their breeding populations such as Dalmatian Pelican at Lake Prespa and the Louros– Aracthos delta (Zogaris et al. 2003). Other species such as Greater Flamingo, Great White Egret, Little Egret, Grey Heron and Great Cormorant are recovering or even expanding their habitat range. Control of indiscriminate shooting and poaching and the creation of artificial reservoirs may have assisted their populations (Tucker & Heath 1994; Handrinos & Akriotis 1997). Interestingly, local populations with expanding populations in parts of Western Europe have shown a regional decline in some wetland areas of the western Balkans (e.g. White Stork, Bittern, Pygmy Cormorant); therefore, small localized subpopulations may be vulnerable to extirpation in geographically isolated Balkan river valleys.

11.7.8. Mammals Several large mammals have declined in range and numbers primarily due to poorly regulated hunting and poaching. However, in upland wilderness pockets, still widespread in the Balkans, refugia for large mammals exist. River-associated mammals are poorly studied and information on rare or threatened species is mostly from protected areas. In the central Balkans National Park (upper Evros basin), a remarkable number of bat species, including species that use riparian habitats, has been recorded (Ivanova 1998). The area is an important stronghold for the wolf, a species that locally expanded its range due to a decrease in human populations in Mts and remote regions. The golden jackal Canis aureus occurs along lowland valleys where it finds shelter and prey along rivers and in deltas; it is frequently observed in the Nestos and Evros Deltas. However, the population of the Arachthos–Louros delta was extirpated in the early 1990s (Giannatos et al. 2005). The otter is widespread in all major river basins and uses a variety of habitats, even steep montane trout streams. However, a recent decline has been documented in lowland Balkan areas. The otter is rare in the highly degraded middle and lower sections of the Evrotas. The Balkans host Europe’s largest bear populations outside Russia, a species that frequently uses riparian areas for migration and feeding. An important brown bear population survives throughout the Dinaric mountain chain, from Slovenia down to the Pindos Mts in central Greece (Swenson et al. 2000). In some parts, brown bear

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populations are expanding their range due to the depopulation of villages. There is a noticeable recolonization of former areas in the northern Balkans and along country borders (Mertzanis 1998). Recently, the recolonization of the upper and middle section of the Aliakmon, Acheloos and Arachthos by bears has been reported. These long mountain river valleys may serve as stepping stones for the southward expansion of brown bears.

11.8. MANAGEMENT AND CONSERVATION 11.8.1. Economic Importance Most Balkan rivers are too shallow and steep to be navigable with large motorized vessels. For example, only the lower sections of the Neretva and Buna are used for trade and communication. Agriculture is by far the most important water consumer in Greece (89%), FYR Macedonia (80%) and Albania (72%). Agricultural water use accounts for 18% in Croatia, 10% in Bulgaria, but only 0.65% in Bosnia and Herzegovina. Half of the water resources in Croatia and Bulgaria (53% and 45%, respectively) supply water for industrial use. Large portions of agricultural land are irrigated in Albania and Greece (49% and 40%, respectively), compared to Bulgaria and FYR Macedonia (18% and 11%, respectively) and all other Balkan countries (between 0.2% and 2%) (World Bank 2003). The Evros, Pinios and Kamchia drain the most intensively cultivated basins (53.4 - 40.6% of the basin, Table 11.1). About 60% of the total rice production and 2/3 of the total mussel production (>30 000 tons/year) of Greece occurs in the Axios Delta and estuary (Karageorgis et al. 2003; Zanou et al. 2005). In Albania, Croatia, Bosnia, Herzegovina, Serbia and Montenegro, hydroelectricity represents a substantial source of power (97%, 62%, 59% and 40%, respectively, of total energy production). In FYR Macedonia, the share of hydropower is about 20%, in Greece and Bulgaria 10%. Dams along the Drin supply major energy for Albania (about 90%, 1350 MW, of total power production; World Bank 2003). Similarly, Neretva (installed capacity: 1120 MW) is a main energy source for Bosnia and Herzegovina (EIA 2006). In Greece, the total annual hydropower production is 3000 MW (PPC 2008). Most reservoirs have multipurpose functions (e.g. irrigation, urban water supply, cooling of thermoelectric plants, aquaculture, recreation). In Greece, around 30% of the usable volume of reservoirs is allocated for irrigation. In most Balkan countries there are major demands for further hydropower development, reflecting the expected strong economic growth in this region. There is also the obligation for EU and EUperspective countries to increase the share of energy from renewable resources to the total energy production. Other economic activities comprise forestry in mountainous areas, a declining industry, fisheries in lakes, lagoons and estuaries, ecotourism and cultural tourism, extraction of salt from lagoons and of inert material from

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riverbeds. The most important lakes for fisheries are Lakes Shkodra (annual production: 950 tons/year), Trichonis (500 tons/year), Ohrid (230 tons/year, declining in recent years), Kerkini (150 tons/year) and Prespa (100 tons/year). It is worth noting that the former Karla Lake (Pinios basin) had an average annual production of 1000 tons. In lagoons, many aquatic organisms flourish forming highly productive systems. Migratory euryhaline fishes and shrimps are the most abundant and commercially important species. Important lagoons for fisheries are the Mesolonghi lagoons in the Acheloos Delta (about 1400 tons/year) and the Narta lagoon in the Aoos Delta (200–340 tons/year). Salt extraction from the Mesolonghi lagoon reaches 120 000 tons/year, 65% of Greece’s salt production. From Narta lagoon, an additional 120 000 tons/year are harvested. Protected areas, where the local economy was formerly based on agriculture and forestry, play an increasingly important role for ecotourism and recreation. For example Lake Ohrid has been declared as a mixed cultural/natural heritage site by UNESCO, which stimulated the local tourist market (ILEK 2005). Other protected areas of major tourist interest include the Vikos–Aoos and Valia Kalda (Aoos) and the Pirin (Nestos) forest national parks, the Amvrakikos wetlands (Arachthos–Louros delta) and Lake Kerkini.

11.8.2. Conservation and Restoration Wars and political instability over the past centuries have created difficulties for both conservation and research. This has inhibited a thorough inventory of species, habitats types, conservation areas and conservation resources at the regional level. Hence, freshwater biodiversity patterns remain poorly documented and the underlying processes are far from being well understood. The protection of the natural aquatic heritage is often unsatisfactory and poorly planned because the focus has been mainly on forested lands or sites of outstanding scenic beauty. Greece and Bulgaria were the first countries in this region that implemented protected forested areas. In Greece, this was through the provision and regulation of the Forest Code and the law on National Parks. The implementation process has been very slow. A major problem remains the administrative complexity on issues of nature conservation, management and enforcement of legislation. Additional problems arise from institutional ineffectiveness, financial restraints, legal problems, deficiency of public involvement and limited political commitment to conservation (Kassioumis 1990; Handrinos & Akriotis 1997). During the past two decades, interest in inland water protection has increased, although the focus was primarily on lentic systems and selected wetland habitats. Biodiversity conservation, ranging from genetic diversity to landscapes, rarely targets rivers or streams in the Balkans. An exception is deltaic wetland areas. In fact, all the larger deltas contain

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protected areas such as Ramsar Sites, with statutory zonation designations. Human and natural factors are often deeply interdependent in these complex systems. The coastal lagoon systems, a priority habitat type for conservation in Europe, are usually exploited as traditional fish farms. Moreover, within the wider area of deltas, there are some unique habitats such as karstic ponds (deep cryptic depressions) either in marshes or in coastal lakes and lagoons, such as those encountered in the Neretva, Louros–Arachthos and Sperchios deltas. In the Sperchios upper delta, for example deep springfed ponds host the local endemic Pungitius hellenicus, perhaps the most range-restricted fish in the Balkans. Nonetheless, there are some upland riverine areas that have been assigned conservation status. These include some spectacular limestone gorges along the Nestos, Aoos, Arachthos and Alfeios, significant portions of the Axios, the virgin forests of Pirin (Nestos–Strymon basins) and Sredna Gora Mt (Evros basin) and several other headwater streams in the major river basins. Quite often, the main river channels are not included in conservation frameworks, and thus remain vulnerable to alteration. International treaties and designations have greatly assisted conservation efforts (UNESCO conservation designations). One of the most important steps in promoting the conservation of aquatic habitats was the signing of the Ramsar Convention for the protection of wetlands. In Greece, there are eight sites in the examined basins (Evros Delta, Nestos Delta and associated lagoons, Kerkini Lake, Axios–Loudias–Aliakmon Deltas, Lake Small Prespa, the Amvrakikos Gulf including the Arachthos Delta and Mesolonghi lagoons at Acheloos Delta). In FYR Macedonia, there is one site at Lake Large Prespa. Lake Shkodra and River Buna are Ramsar sites in Albania and Montenegro. The Neretva Delta is also protected by the Ramsar Convention with two sites in Croatia and Bosnia and Herzegovina, respectively. European Union Directives have also promoted the designation and conservation of protected areas in the Balkan states. In Greece, widespread identification and inventory of potential conservation areas officially begun in the early 1980s and was supported particularly by the Birds Directive (79/ 409) which uses bird populations and species’ vulnerability as criteria for the identification of sites of conservation importance. The Habitats Directive (92/43/EEC) for the protection of species and habitats of community interest contributed to the designation of protected areas within the Natura 2000 conservation scheme. This is the umbrella EU legislation for nature conservation and drives changes in national legislations, which are currently under reform. Greece has proposed 359 sites to be included in the NATURA 2000 protection network. These include a number of riverine gorges, almost all the major river deltas including associated lagoons, and a number of lakes that maintain a present or past connection with large rivers, such as Lakes Trichonis, Lysimachia, Ozeros, Amvrakia, Kerkini, Prespa and Kastoria. National legislation concerning national parks is in a transitional phase

as the Natura 2000 network expands and new protected areas with their management bodies are being planned. In Bulgaria, monitoring schemes are better developed than in other Balkan countries, and assistance from the EU has helped important site inventory processes. Since the country joined the European Union (January 2007), it undertook the obligation to submit to the European Commission a list of sites to be included in the NATURA 2000 network. The management of natural areas in the Former Yugoslav Republics is still in a transitional stage. In FYR Macedonia, a forestry corps is responsible for the management of designated protected areas (covering about 7.3% of the land area), but its tasks mainly involve inspections. This country plans to extend the protected area surface area to 12% of its national territory, establishing 250 Protected Areas. In Bosnia and Herzegovina, even though international assistance has helped to develop the framework of an environmental law, legislation remains incomplete and the management of protected areas is far from being satisfactory. In Montenegro, a comprehensive set of acts devoted to the management of Protected Areas has not been completed. However, the existing national legislation (the National Parks Law) covers several issues of management of the four officially designated National Parks, including Shkodra Lake. Serbia’s protected areas are classified according to the criteria recommended by the World Conservation Union (WCU), and their management is coordinated by the Ministry of Environment according to national laws. In Albania, the actual management of protected areas and national parks is the responsibility of the Ministry of Agriculture and Food. This Ministry intends to reorganize protected areas, grouping several national parks together and increasing the total surface of Protected Areas and National Parks from 165 000 hectares to over 449 000 hectares (15.6% of the country’s area). However, enforcement and monitoring within Albania’s protected areas is inadequate, and management plans do not yet exist for most areas.

11.8.3. Restoration Activities and Potential Ecological restoration efforts have traditionally concentrated on conservation actions for endangered species and protected area habitat enhancement. Most projects are carried out at a local scale such as riparian tree planting. European Union funding has been instrumental for promoting this type of active restoration. Between 1992 and 2005, Greece benefited from 46 LIFE-NATURE projects that in many cases provided small restoration programs, often targeted on wetland restoration. The EU-INTERREG programme and the EU-Structural Funds have also assisted restoration efforts primarily at the local level and often of demonstrative nature. NGOs, Government Research Institutes, and University Departments have been active too, often in cooperation with the local and federal Government (Aperghis & Gaethlich 2006). Active river restoration has not been

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extensively implemented and there is a major lack of post evaluation or project monitoring (Theocharis et al. 2004). A current large wetland restoration project concerns the partial re-establishment of Lake Karla (Kettunen & ten Brink 2006). Another ongoing project concerns the restoration of 2.8 km2 riparian forests in the Nestos delta. Additional restoration activities have been undertaken for the Evros riparian forest in Bulgaria and in the Kamchia delta.

11.8.4. Reference Conditions Establishing reference conditions is important for developing ecological quality classification systems according to the Water Framework Directive 2000/60/EC (WFD). Identifying natural watercourses is not an easy task in the cultural landscape of the Balkans because centuries of varied land use and settlement combined with pollution and widespread hydromorphological modifications obscure the natural physical and biogeochemical structure and processes. Balkan landscapes, as other Mediterranean landscapes, usually show a mix of degraded and regenerating biophysical features. Also, temporal rainfall patterns differentially affect aquatic biotic communities (Bonada et al. 2007). However, the majority of the mountainous parts of Balkan river basins, especially along the country borders, can be considered as minimally disturbed. These regions are only affected by livestock grazing, although the density of roads has increased recently, particularly in Greece. Sporadic ecological quality assessment studies carried out in Greece confirm that a number of headwaters and tributaries in the Nestos, Axios, Aliakmon, Aoos, Acheloos and Alfeios basins satisfy the EU criteria regarding hydrogeomorphological, chemical and biological (mainly based on macroinvertebrates) reference conditions (Lazaridou-Dimitriadou et al. 2000; Skoulikidis et al. 2002a, 2004; Iliopoulou-Georgoudaki et al. 2003; Chatzinikolaou et al. 2007; Economou et al. unpublished data).

11.8.5. EU Water Framework Directive The water resources in the Balkan Peninsula are temporally and spatially unevenly distributed among and within countries. Some countries face localized water shortages, while most major rivers and lakes are transboundary, creating conflicts of interest. Almost all Balkan countries face daunting water resource challenges because of urgently required investments in water supply, sanitation, irrigation and hydroelectricity. At the same time, water quality deteriorates (e.g. Evros, Axios, Kamchia, Drin), water exploitation for irrigation increases (e.g. the Thessaly and Laconian plains), fragmentation by large dams is a major pressure (e.g. Drin, Neretva, Acheloos, Nestos, Aliakmon), flooding remains a major threat (e.g. Evros, Drin, Aoos, Sperchios, Neretva) and droughts increasingly exhaust water resources (e.g. Pinios, Evrotas).

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With the exception of Greece and Bulgaria, which are EU Member States, all other Balkan countries are in the process of integration. This obliges compliance with EU policies, rules and regulations concerning water, here in particular, with the WFD, which is the basic water management legal instrument. However, economic, political and structural constraints impose considerable impediments on the application of the EU environmental legislation. Water management traditions and approaches differ among countries, reflecting differences in political systems, administrative structures and relevant institutional frameworks. Greece has adopted the EU water policies and rules including the WFD. Nevertheless, the application of environmental legislation was proved in a number of cases inadequate. Even in protected areas, and despite national and international legislation, environmental protection has been often neglected in favour of large-scale development projects. Environmental Impact Assessments have so far been applied often in inappropriate and ineffective ways (Handrinos & Akriotis 1997). An outstanding example of this is the well-publicized Acheloos Water Transfer, a megaproject which planned to divert a large portion of the waters of the Acheloos (today in a reduced scale of 0.6 km3/year) towards the Pinios basin. This transfer is anticipated to serve irrigation of 2400 km2, drinking water supply, hydropower production and to improve surface and groundwater quality and quantity of the Thessaly plain. The project has been ongoing and has stirred debate and controversy for over 30 years; but, study after study, has not convinced courts or the public that the environmental costs do not significantly out-way the benefits of this water transfer. For the other Balkan countries, constraints arise from long-standing sectoral planning traditions, heavy investment requirements (e.g. in sanitation and waste treatment infrastructure), poor administrative capacities and little experience of dealing with multidisciplinary issues. Additional difficulties arise from the deteriorating government services and public infrastructure following severe civil conflicts that recently affected the economies of some countries. Hence, policies and strategies for water use and management evolved on different principles, reflecting the long duration of the previous period of central planning culture and practice. In accordance with the prevailing political and administrative structures, management followed a top-down approach based primarily on sectoral planning, in which different sectors and services were separated and handled by different ministries and agencies. Bulgaria has joined the EU very recently (January 2007), and Croatia, as a candidate country, made progress in establishing appropriate legislative and institutional framework for a decentralized integrated management on a river basin district scale compliant with the demands of the WFD. In the constituent republics of the state union Serbia and Montenegro the water legislation has several shortcomings hampering the effective management of water resources including lack of a clear institutional framework (World Bank 2003). In

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Bosnia and Herzegovina, water management is under the authorities of two entities; the Federation of Bosnia and Herzegovina and Republika Srpska, which have two independent water laws and organizational structures based on the WFD. Geopolitical and administrative boundaries in the Neretva basin make the optimal management of the river basin, delta and coastal zone complex and difficult. In FYR Macedonia and Albania, despite the adaptation of WFD principles in respective water laws, there is a clear lack in implementing a modern water resource management into reality (Speck 2006). The speed of legal and institutional reforms required for the implementation of the WFD is generally slow in all countries, including Greece. In Greece and Bulgaria, despite the recent elaboration of preliminary River Basin Management Plans, there is limited progress in implementing the Directive, particularly for the assessment and classification of the ecological status of waterbodies (Skoulikidis & Gritzalis 2005; BMEW 2005). Concerning the management of shared basins, one-sided exploitation of water resources and pollution impact by upstream parties cause critical deficiencies of water quantity and quality to downstream countries, including surface and groundwaters and wetlands. The Neretva, Evros, Tundja, Nestos, Strymon and Prespa and Doirani Lakes are examples of shared waterbodies where such situations are encountered (GWP 2005). To face the transboundary nature of water supply and sanitation issues, the Balkan countries adopted the Water Convention of the United Nations Economic Commission for Europe, which entered into force in 1996. The provisions of the WFD and the Water Convention include the design and implementation of joint plans, joint river authorities, transboundary river basin units and coordinated national measures at a basin scale, and provide the platform for the management of shared water basins between member states and non EU countries. However, joint international management is either insufficient or completely missing for the majority of shared rivers and lakes despite, agreements, protocols and treaties signed for the rivers Neretva (not fully in power), Drin (between Albania and FYR Macedonia), Aoos, Axios, Evros (between Greece/Bulgaria and Greece/Turkey) and Nestos and for Lakes Shkodra, Ohrid, Prespa and Doirani (GWP 2005). In the majority of cases, political obstacles, lack of resources or inefficient collaboration in a technocratic level (Kallioras et al. 2006) have not allowed proper implementation (GWP 2005). An example of poor transboundary cooperation is the case of the Evros basin, where major problems are connected with floods and water quality. Moreover, the Axios basin has been at the heart of numerous conflicts between Greece and FYR Macedonia for decades (GWP 2005), despite agreements on water management that date since 1959. In contrast, the case of Prespa Lake is an excellent example of how transboundary environmental issues can encourage international cooperation among neighbouring nations (Greece, FYR Macedonia and Albania). Lake Ohrid

provides another example of effective measures being taken for cooperative management of transboundary lakes. Moreover, after years of disputes, a bilateral treaty regulating the amount of Nestos water entering Greece has been signed, while cooperation exists between the two countries in the framework of several bilateral research projects (GWP 2005; UNESCO 2006). Overall, the Balkans represent one of the most important areas for potential transboundary cooperation in protected area management worldwide. Indeed, at least 50% of the sites of international importance in the region are transboundary, including all the large lakes Shkodra, Ohrid, Prespa and Doirani, many large rivers and important deltas (e.g. Evros River, Buna Delta). Moreover, in the IUCN Strategic Plan for South Eastern Europe, 37 priority sites have been identified for a transboundary cooperation in protected areas development.

11.9. CONCLUSION AND PERSPECTIVE Driven by active tectonic movements, the Balkan Peninsula is a geomorphologically dynamic region with intensive erosion and deposition. Dynamic river systems create a distinct longitudinal sequence of steep gradient headwaters, braided and meandering channel types and deltaic areas. Recent hydromorphological alterations (embanking, straightening, reservoir building) have inhibited or reversed the evolution of deltas and have reduced the recharge of groundwater aquifers. On the other hand, unregulated river sections are prone to floods, and widespread deforestation and wildfires enhance erosion. Overexploitation of water resources for agriculture, in combination with semi-arid conditions and a progressive decline of precipitation due to climate change, has modified most natural flow regimes. Former perennial rivers are now temporary. In addition, large-scale wetland drainage has caused major hydrological modifications, has degraded water quality, and has led to the loss of habitats and species. Pollution from municipal, industrial and agrochemical sources remains a major threat to Balkan freshwater ecosystems. Environmental pressures differ among regions; mining effluents affect mainly Bulgarian and Albanian rivers, industrial pollution is important in Bulgaria, FYR Macedonia and Bosnia and Herzegovina, agricultural pollution is widespread in Greece, Bulgaria and Albania, while urban pollution prevails in all countries except Greece. Today, the aquatic and riparian fauna and flora in many river basins is at risk. Lowland sections are at greatest risk due to changes in agricultural practices, industrialization, tourism and large-scale modifications in headwaters. Environmental decision-making processes are intrinsically complex and require concerns for biodiversity conservation and integrated river basin management. A sound scientific basis is often missing. The WFD demands a reduction of human impacts to establish a ‘good’ water status, however, at present the Directive is only being implemented in Greece and Bulgaria. Overall, there is a

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major lack of hydrological and physicochemical data, and in particular of ecological data, that hinders the establishment of river basin management plans. The development of operational monitoring networks is of pivotal priority. The situation becomes even more complex in transboundary river basins where the establishment of appropriate administrative and a scientific institutional framework are essential. Efforts should be devoted to standardizing and calibrating techniques for measuring chemical and ecological quality among countries sharing river basins. Today, Balkan countries should take advantage of EC and UN assistance in order to efficiently manage, protect and restore their watercourses.

Acknowledgements The authors would like to thank their colleagues at the Institute of Inland Waters (Hellenic Centre for Marine Research), namely Ioannis Karaouzas, Elias Mousoulis, Yorgos Amaxidis, Leonidas Vardakas, Theodora Kouvarda, Argyro Andriopoulou, Maria Koutsodimou and Dimitris Kommatas, who supported the entire attempt for the development of this manuscript. They also whish to thank the Croatian Meteorological & Hydrological Institute, who kindly provided a comprehensive water temperature and level time series, as well as Danillo Mrdak from the University of Montenegro for assisting in compiling the Drin fish data. This book chapter was also made possible by project grants from the E.U. and the Greek General Secretariat of Research & Technology, Ministry of Development.

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FURTHER READING Dynesius, M., and Nilsson, C. 1994. Fragmentation and flow regulation of river systems in the northern third of the world. Science 266: 753–762.

RELEVANT WEBSITES Hydrology Global Runoff Data Centre (GRDC) http://grdc.bafg.de/servlet/is/ Entry.987. Display or http://www.grdc.sr.unh.edu/html/Runoff/index.html. The Global River Discharge Database (RivDIS), UNESCO: http://www. rivdis.sr.unh.edu. Mediterranean Hydrological Cycle Observing System

PART | I Rivers of Europe

(Med-Hycos), World Meteorological Organization: http://medhycos.mpl. ird.fr/en/t1.ovei&gn=ove.inc&menu=projectimp1st.inc.html Hellenic Public Power Corporation: http://www.dei.gr/default.aspx?id=1001&nt= 18&lang=2 Bosnia & Herzegovina, National Meteorological Service: http://www.hydromet.gov.bz/Data_Request.htm Serbia, Republic Hydrometeorological Service: http://www.hidmet.sr.gov.yu/eng/osmotreni/ stanje_voda.php. Bulgaria, National Institute of Meteorology and Hydrology: http://hydro. meteo.bg/indexen.html Albania, Academy of Science, Institute of Hydrometeorology: http://www.academyofsciences.net/institutes/ hydrometereology/. Sediment fluxes World River Sediment Yields Database, FAO: http://www.fao.org/ag/agl/ aglw/sediment/default.asp. Water quality European Environment Information and Observation Network (EIONET), European Environment Agency (EEA): www.eionet.europa.eu. Hellenic Ministry of Rural Development and Food (HMRDF). http://www. minagric.gr/en/1.1.html. Hellenic Ministry for the Environment Physical Planning and Public Works (HME). http://www.minenv.gr/welcome_en.html. Hellenic Centre for Marine Research, Institute of Inland Waters (rivers): http://www.rivernet.gr (in Greek, in English under construction). Hellenic Centre for Marine Research, Institute of Inland Waters (lakes): http://www.lakenet.gr/index_en.php. Serbia, Republic Hydrometeorological Service: http://www.hidmet.sr.gov. yu/eng/osmotreni/kvalitet_voda.php. Biology www.fishbase.org www.ripidurable.eu.

Chapter 12

The Italian Rivers B. Gumiero

B. Maiolini

M. Rinaldi

Department of Evolutionary and Experimental Biology, Bologna University, Via Selmi 3, Bologna 40126, Italy

Natural Science Museum, Via Calepina 14, Trento, Italy

Department of Civil and Environmental Engineering, University of Florence, Via S. Marta 3, Firenze 50139, Italy

N. Surian

B. Boz

F. Moroni

Department of Geography, University of Padova, Via del Santo 26, Padova 35123, Italy

Italian Center for River Restoration, Viale Garibaldi 44/A, Mestre 40173, Italy

Po River Basin Authority, Via Garibaldi 75, Parma 43100, Italy

12.1. 12.2.

12.3.

12.4.

12.5.

12.6.

12.7.

Introduction Biogeographic Setting 12.2.1. General Aspects 12.2.2. Paleogeography Physiography, Climate, and Land Use 12.3.1. Landforms and Geology 12.3.2. Climate 12.3.3. Land Use Patterns Geomorphology, Hydrology, and Biochemistry 12.4.1. Geomorphology 12.4.2. Hydrological Regime 12.4.3. Biogeochemistry Aquatic and Riparian Biodiversity 12.5.1. Invertebrates 12.5.2. Amphibians and Reptiles 12.5.3. Fish Fauna 12.5.4. Birds and Mammals Management and Conservation 12.6.1. Economic Importance 12.6.2. Conservation and Restoration 12.6.3. EU Water Framework Directive Conclusion and Perspective Acknowledgements References

12.1. INTRODUCTION Italy has a surface area of 301 341 km2. The country is situated in southern Europe in the middle of the Mediterranean basin, extending latitudinally from 47 300 to 35 470 N between the Alps and the Mediterranean Sea. Few Italian rivers today can be considered to be in a natural state. Ever Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

since humans have colonized this region, they have strongly interacted with the rivers and their natural dynamics by shaping their morphology and using the landscape. Exploitation of natural resources has been so extensive that today only small areas of the landscape and of the rivers that flow through it can be considered natural (Figure 12.1). In the Adige basin, human presence is recorded from the Paleolithic age, when Homo erectus and H. neanderthalensis lived in the Adige valley during inter-glacial periods. After the last Ice Age (about 10 000 BC), as the climate warmed, seasonal hunting settlements in the valley became common. During the Mesolithic, more permanent settlements were established in the valley, with evidence of exchanges with Adriatic populations and contacts with trans-Alpine populations at the end of this period. Towards the end of the Neolithic, farming communities began to settle and alter the landscape by converting forests to croplands and pastures. Since then, the Adige valley has seen a continuous growth in population size and movements between north and south. Commercial and cultural exchanges increased with the construction of the Via Claudia Augusta by Emperor Claudio (47 AC), which connected the Adriatic port of Altino to Veldidena (now Innsbruck) from where it continued as two routes: Augusta Vindelicorum (now Augsburg) and Castra Regina (now Regensburg) (Turri & Ruffo 1992). Significant human impacts on Italian rivers began in the Neolithic age with the introduction of livestock and agriculture, and subsequent deforestation of large areas that continued for about 4000 years. A dramatic increase in agricultural development and deforestation occurred during the Etruscan–Roman period, that in turn increased sediment transport to rivers and coastline degradation. Since then, human impacts have become progressively dominant on river ecosystems. The first construction of levees along major cities, 467

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FIGURE 12.1 Digital elevation model (upper panel) and drainage network (lower panel) of the Italian selected Rivers.

of canals, aqueducts, irrigation systems, land drainage systems and land reclamation, also date back to the Roman period. During the late Roman Empire, some major hydraulic works were completed, such as the channel diverting the Chiana, a tributary of the Tiber River, from south to north to become a tributary of the Arno River, which increased its catchment area by about 700 km2.

The Middle Age was characterised by periodic stages of rural population growth and agricultural development. The first artificial meander cut-offs were completed along major rivers. Levees were also constructed or reinforced along many rivers near cities, and numerous canals were built for irrigation and land reclamation. Beginning in the 12th century, a series of canals were constructed in the central Po

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Plain (called Navigli) for irrigation and as navigation waterways between major cities (Milan, Turin, Bologna, Venice). In the Renaissance Period, extensive hydraulic developments on the valley floor (river diversions, flow regulation, meander cut-offs, levees) were built for flood protection, navigation, and land conversion for agriculture. The process of land reclamation (‘bonifica’) began to spread along many coastal and internal wetlands. In the beginning of the 18th century, extensive canalization and additional meander cut-offs were completed, and in the 19th century more canals and embankments of the major rivers were constructed. For example, widespread canalization of some reaches of the Arno River upstream of Florence as well as construction of embankments along the Po River, which began in the 12th century, were completed during this period. The late 19th and early 20th centuries were characterised by progressive increases in human impacts such as dam construction, canalization, river diversions, construction of groins and levees, and land reclamation of coastal marshes and lagoons. Further hydraulic developments were completed to reinforce and raise embankments and reduce flood risk, on the Po and Arno Rivers in particular. Finally, in late 20th century, economic development, industrialization and urbanization of river corridors resulted in additional projects for flood protection, flow regulation, and exploitation of river resources (sediment mining). Despite this large and continuous effort for flood protection, some devastating floods still occurred in the last century. For example, the Po River in 1951 broke through the embankments along its lower course, flooding 1200 km2 of land and causing the death of 80 people. The Arno River flood in 1966 inundated Florence. Intensive sediment mining of rivers started after World War II for reconstruction purposes, following the economic development of the country, particularly during the 1960s and 1970s for construction of the first Italian highway system. This process induced dramatic changes in river morphology, causing a phase of intense incision that affected the stability of man-made structures, of ecosystems and coastlines. The increase of flood risk for settlements in alluvial plains has contributed during the last decades to a further increase in river regulation. Most rivers today are embanked or canalized to some extent in areas near cities and urbanised alluvial plains. Italian rivers comprise a diversity of fluvial ecosystems, ranging from Alpine glacier-fed streams to ephemeral Mediterranean streams, and from large rivers such as the Po to spring-fed brooks and artificial canals. They all flow through densely populated areas. Italian rivers are shorter than most other European rivers because of the shape of the Italian peninsula and of the Apennines that separate runoff along two opposite slopes in peninsular Italy. In continental Italy, streams generally have relatively high discharge because of abundant rainfall and runoff from Alpine snowfields and glaciers. The different geographic, morphological and climatic settings of the area determine not only different stream

types but also different kinds of land-use, and the degree of urbanisation, pollution, and impacts on water resources (Negri et al. 2004). Although Italy is rich in water resources, the distribution is uneven, with the majority occurring in the north (65%), 15% in the centre, 12% in the south, and 8% in the main islands (ANPA 2001). Because of this variability, our primary focus in this chapter is the Po River, which forms the largest Italian plain and covers 24% of Italy (Photos 12.1 and 12.2). Italy currently has a population of 57 million with a density of 190 inhabitants per km2. Over 16 million people live within the Po River basin that encompasses 3188 municipalities. Other Alpine rivers considered in this chapter include the Adige, the second longest Italian river, and the Tagliamento because of its relatively pristine condition. The Brenta River also was included because of its historical role in the region and as an example of a river with a mix of natural and regulated reaches. The two slopes of the central Apennines (east towards the Adriatic Sea and west towards the Tyrrhenian Sea) are strongly asymmetrical. The western rivers are longer, more branched and flow in meandering valleys, whereas eastern rivers that flow into the Adriatic Sea have steep slopes, almost linear courses, few tributaries, and are shorter than 100 km. The Tiber and Arno rivers, two major Italian rivers, are good examples of central Apennine rivers that flow to the Tyrrhenian Sea. The Sangro was included as an example of a river flowing from the Adriatic Apennine slope. From the many interesting streams in the southern Apennines, the Amendolea in Calabria was included as a typical ephemeral stream called ‘fiumara’ (Photo 12.3). Last, representative rivers from the two main Mediterranean islands are also presented: the Flumendosa in Sardinia (Photo 12.4), and the Alcantara in Sicily. These rivers illustrate the complex array of Italian river ecosystems (Table 12.1), although we are aware that several minor typologies have been omitted.

12.2. BIOGEOGRAPHIC SETTING 12.2.1. General Aspects The Italian peninsula and its islands form a bridge between Europe and Africa, and represent a colonisation pathway for fauna and flora to and from countries bordering the Mediterranean basin. The wide range of climatic conditions and habitats encompass three main biogeographic regions: Alpine, Continental and Mediterranean (EEA 2005). A further division comprises eight terrestrial regions: Alps, Padanian plane, mountain Apennines, pre-Apennines, Sicily, Sardinia, minor islands and coasts. It is also possible to divide Italy in two phytogeographic regions (Giacomini & Fenaroli 1958): the Eurosibiric (which includes the Alps, the upper Padanian–Venetian plain, and the Friuli plain) and the Mediterranean (which includes most of peninsular Italy and surrounding islands). The Eurosibiric region is characterized by summer rains, whereas rain is

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PHOTO 12.1 Aerial view of the River Po in its middle course, near the ‘Mezzana Bigli’ bridge (Photo: Autorita di Bacino del Po).

scarce in summer in the Mediterranean with drought lasting from two (in the submediterranean and Mediterraneanmontane areas) to six (in the drier stenomediterranean areas) months. The Eurosibiric vegetation is present on the southern side of the Alps and generally corresponds to the central European typology, chiefly in the montane belt. It is characterized by the addition of south-european and submediterranean/ Mediterranean-montane species. As a consequence, plant communities are quite diverse, mainly in the hill belt. For instance, linden and maple forests are composed of several

thermophilic species such as Castanea sativa, Ostrya carpinifolia, Ilex aquifolium, Salvia glutinosa, Symphytum tuberosum, Vinca minor, Asperula taurina. Furthermore, the Festucetalia valesiacae dry grasslands contain several Mediterranean-montane species (Globularia bisnagarica, Astragalus vesicarius, Teucrium montanum, Fumana procumbens, Alyssum alyssoides, Trinia glauca). Phytogeographers usually include also the mountain areas of the northern Apennines (and sometimes the central Apennines) in the Eurosibiric region, leaving only the hill ranges of the Apennines to the Mediterranean region. PHOTO 12.2 The River Po at the confluence of its tributary Ticino (Photo: Autorita di Bacino del Po).

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PHOTO 12.3 The extraordinary scenario of ‘Fiumara’ Amendolea: a sediment river! (Photo: Bruno Boz).

Plant communities of the northern Apennines are similar to those of the Alps, having Vaccinium spp. subalpine heathlands and representing a clear phytogeographic affinity. The beech forests (typical Central–European formation) on the other hand, are poor indicators of phytogeographic affinities because they extend along the entire Apennines and even on the mountains of Corsica and Sicily. These two islands, together with Sardinia, are considered part of the Mediterranean region by most authors. The Mediterranean climatogenic vegetation is represented by submediterranean broadleaf deciduous forests (Quercus cerris, O. carpinifolia, Quercus pubescens, Quercus frainetto, Carpinus orientalis) and stenomediterranean both evergreen (mostly Quercus ilex) and deciduous (Q. pubescens) woods, whereas the Mediterranean-montane conifer forests (Pinus nigra and Pinus laricio) are usually relicts and distributed among the beech forests on dry mountainsides. The high Mediterranean mountains are characterized by thorny cushion-like vegetation of the Irano-Nevadian belt of Pignatti (Pignatti 1979, 1982, 1986).

The floristic characteristics of Sardinia and Corsica place them in the Sardinian-Corsican phytogeographic region, although the ecological characteristics and vegetation of the mountains of Corsica are quite different from those of Sardinia, which has lower elevation. In fact, the vegetation of Corsica mountains is similar in some cases to that of the Alps in having subalpine Alnus viridis shrubs. Sicily belongs to the Sicilian phytogeographical region because of the high number of endemisms. Other less analytical phytogeographic schemes have been developed for the Mediterranean Region. Takhtajan (1986), following Giacomini and Fenaroli (1958), defines a Ligurian– Tirrenic province in juxtaposition to an Adriatic province on the basis of endemic flora shared between the islands and western Italy. The endemic plants of the Ligurian– Tirrenic province are quite numerous (e.g. P. nigra ssp. laricio, Alnus cordata, Quercus congesta, Genista aetnensis, Genista desoleana, Sesleria insularis). On the other hand, the Adriatic province, represented by eastern Italy, is poorly characterised. PHOTO 12.4 Example of a typical Mediterranean river: the lower River Flumendosa in Sardinia (Photo: Bruno Floris).

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TABLE 12.1 General characterization of the selected Italian Rivers Tagliamento Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25%) ecological regions

Brenta

Adige

Po

1469 12 100 6,96 145.6 3.0 2 2

736 73 974 48,60 124.3 8.8 4 2; 54

987 2580 3,44 215.0 6.1 3 2; 54

508 1567 2,24 139.0 8.8 2 2; 54

2.4 14.3 1.7 60.0 13.2 8.1 0.0 0.3

7.6 50.4 3.0 31.0 5.3 2.3 0.0 0.4

3.0 14.5 6.3 42.0 17.1 16.6 0.0 0.5

5.0 42.8 1.5 28.8 10.3 8.6 0.2 1.9

Protected area (% of catchment)

0.2

3.2

16.7

4.8

Water stress (1–3) 1995 2070

1.3 1.5

1.1 1.1

1.2 1.3

2.0 2.0

Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparce vegetation Wetland Freshwater bodies

Fragmentation (1–3) Number of large dams (>15 m) Native fish species Non-native fish species Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person)

2 5 26 6 0 50 24 314

3 31 37 17 2 111 28 905

3 147 44 25 7 224 27 339

Amendolea

Alcantara

Tiber

Arno

Flumendosa

920 1606 0,75 121,1 10,0 2 4

921 147 n.d. 74.2 16.2 2 63; 67

911 556 0,28 61.5 15.1 2 63

506 17 156 8,43 80.2 12.5 2 40

320 8230 3,47 80.5 11.8 2 40

639 1818 0,69 59.2 14.9 1 67

1.0 37.1 2.6 36.4 18.4 4.1 0.0 0.4

0.0 17.2 0.5 46.2 30.2 5.9 0.0 0.0

1.7 25.6 0.0 18.9 49.1 4.0 0.0 0.7

4.8 48.3 1.9 34.9 8.7 0.8 0.1 0.5

5.6 50.2 1.2 39.5 2.9 0.1 0.2 0.3

0.8 14.6 0.0 22.4 59.7 1.5 0.1 0.9

41

80.7

21.9

5.7

2.3

12.3

3.0 3.0

3.0 3.0

2.0 2.0

1.7 1.7

1.2 1.2

1.2 1.2 3 5 8 3 0 51 17 684

1 1 1 1 0 61 13 144

1 0 2 2 0 87 13 858

3 15 20 21 2 238 22 661

3 20 18 17 1 243 24 147

3 6 2 1 0 23 15 989

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For data sources and detailed explanation see Chapter 1. n.d. no data.

3 7 25 11 1 251 26 142

Sangro

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Chapter | 12 The Italian Rivers

Six main zoogeographic districts have been defined for Italy: the Alpine, Padanian, Apennininc, Apulian, Sardinian and Sicilian districts (Ruffo & Vigna Taglianti 2002; Minelli et al. 2005). The Alpine Province corresponds to the Alps orographic system and the Padana Province to the Padano– Veneta Plain. It extends along the Adriatic side of the Apennines, from Romagna to Conero, and represents a transition area between the Alpine and the Apennine Provinces. These are represented by the peninsula and divided into three faunal sectors (northern, central and southern). The Apulian Province includes the territories of Gargano, Murge, and Salento. The Sicilian Province represents the insular extension of the Apennine Region. The Sardinian Province has lower biodiversity than the Sicilian but 6.5% of its species are endemic, most of which belonging to very peculiar troglobitic and stygobitic fauna. In regards to Italian ichthyofauna, Bianco (1987) defined two main ichthyogeographic districts on the basis of different palaeogeographic histories: the Tuscany–Latium district, and the Padano–Veneto district (including the Adriatic side of the Apennines to the Vomano River in Abruzzo). The latter district has higher number of species and of endemites than the former. About 20 species are exclusive to the Padano–Veneto district, four are shared with the Tuscany– Latium district, and 10 are distributed in the entire peninsular Italy. Only six species are exclusive to central or southern Italy. There are 11 taxa endemic to the Padano–Veneto district, five in the rest of Italy, and none in the islands. The distribution of Italian fish fauna has been greatly altered by introduction of non-native species and by the movement of fauna (Zerunian 2002): in the past three decades a high number of fish have been moved, accidentally or not, from one hydrological basin, where they were native to a different one, where they were not present before. Most cases refer to the movement of species from northern Italy to the rest of the country: several of the small Cyprinidae of the Padano–Veneto district are presently found in rivers and lakes of Tuscany, Liguria or Latium, where they compete with local species. Some movements in the opposite direction are known as well, such as Rutilus rubilio now present in some streams and rivers of the northern side of the Apennines. Two Gobiidae, P. martensii and P. nigricans, which are endemic, respectively of the Padano–Veneto region and of the Tuscany–Latium region, are both present today on the Adriatic and Thyrrenic side of central Apennines.

12.2.2. Paleogeography Italy is a relatively young land from a geological point of view. Nearly all of its territory emerged from the recent orogenic upheaval (the Alpine orogenesis), which, although relatively weak, spread into the axis of the south-central Apennines. The result of this orogenic evolution was an extremely complex tectonic movement and the formation of a wide variety of geological features in a relatively small

area. The physical aspect of the country is determined by the presence of the Alps and the Apennines and by the elongate, narrow shape of the peninsula surrounded by the sea. The last glaciation, around 25 000 to 15 000 BC, had a major influence on the evolution of the fluvial systems in Italy. A large part of the Alps was covered by glaciers during the Last Glacial Maximum (LGM), whereas a much smaller area of the Apennines was affected by glaciation. The main alpine valleys were filled by glaciers hundreds of meters thick, whose tongues often reached the present Po and Venetia–Friuli Plains. Besides the presence of glaciers, the lowering of the sea level to about 120 m below the present level caused the emersion of a large area of the Adriatic Sea (up to Ancona). Consequently, the river network developed over a large plain that corresponded to the present upper part of the Adriatic Sea. The response of the fluvial systems to the last glacial– interglacial transition differed from one system to another, but aggradation was the main process during the LGM when large portions of the present plains were built (Castiglioni & Pellegrini 2001). Many rivers after the LGM underwent a dramatic incision phase that caused the formation of terraces and a downstream shift in deposition zones. The latter phenomenon is well documented in the Venetia–Friuli Plain where the incision of the upper portion of the plain corresponds to sedimentation in the lower portion (Fontana et al. 2008). The sea level rose quickly during the early Holocene then slowed later on: 10–11 mm/year between 10 000 and 6800 years BC and to 1.5 mm/year in later periods (Preti 1999). Such sea level changes initially caused an upstream shift of river mouths, whereas sea protraction became the dominant process later on, and caused the formation of the present Po River delta.

12.3. PHYSIOGRAPHY, CLIMATE, AND LAND USE 12.3.1. Landforms and Geology Italy can be divided into three physiographic regions: continental, peninsular and insular. The continental region is connected to central Europe by the Alps and includes the drainage basins of the Po River and those Alpine and Apennine rivers that drain into the Adriatic Sea. The second region is characterized by the Apennine chain that separates the Adriatic, the Tyrrhenian, and the Ionian Seas. The third region includes the two major islands, Sicily and Sardinia, and a number of smaller islands. The Alps extend along east– west direction and mean elevation decreases eastward. The highest peak is Mt Bianco (4807 m asl). The mean elevation of the Apennines is lower than that of the Alps and the highest peak is Gran Sasso (2912 m asl). Apart from the Padanian plane, there are few flat areas and most are tectonic depressions parallel to the axis of the Apennine chain. The remaining few lowland areas of the peninsula are mainly

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along the coastline: Maremma, Agro Pontino and Campania Plains in the central Tyrrehenian coast, Tavoliere pugliese in the south Adriatic coast and Metaponto in the Ionic coast. As a consequence, a large part of Italy is represented by mountains (51%) and hills (29%), while only 20% is occupied by plains. Lowlands cover 23% of the region in the north, 18% in the south and 9% in central Italy. The largest lakes are in northern Italy (Garda, Maggiore, Como, Iseo), formed by cluster-shaped moraine systems. Some lakes in central Italy originated from volcanic craters (Bolsena, Bracciano, Vico). The geology of Italy varies widely, comprising sedimentary, igneous and metamorphic rocks, and Quaternary deposits (mainly fluvial, glacial and slope deposits). Most of the country is tectonically active as a result of a convergent plate boundary accompanied by extensive active volcanism. The geology of northern Italy is characterized by the strong contrast between the Alps and the Apennines, which are separated by the large alluvial plain of the Po River. The Alps are a typical collision chain resulting from the subduction of the European plate under the Adria plate, which is an extension of the African plate. The chain has a double divergence with nappes thrust towards the north and the pre-Alps (southern Alps) overthrust to the south. The geology of central Italy is dominated by the Apennine thrust belt. Rocks are mainly sedimentary, of Mesozoic and Cenozoic age. There are also igneous rocks, especially in the area around Rome (‘Roman Magmatic Province’) and Naples, and some metamorphic rocks are exposed in the Apuane Alps and in southern Tuscany. Sardinia is the second largest island of the Mediterranean. The island, being an ancient region with rocks from the early Palaeozoic, lacks high mountains because of its long erosion history. Granite, schist, tranchite, basalt (called ‘jars’ or ‘gollei’), sandstone, dolomite–limestones (called ‘tonneri’ or ‘heels’) dominate at heights between 300 and 1000 m asl. The Po River originates from Mount Monviso at 2022 m asl and flows towards the Adriatic Sea. Its delta represents an important habitat with high environmental and landscape value. It is the largest Italian watershed (74 000 km2, including the sub-basins Burana-Po, Volano and the Delta) and the longest river (650 km, maximum historical discharge: 10 300 m3/s at Pontelagoscuro in 1951). Its geomorphological, hydrological and biological features vary as it flows from the Alps to the Padanian agricultural plain that is built on Quaternary deposits of the main river and its tributaries. The Po basin can be divided into three areas of different lithology: (1) an Alpine sector of mostly crystalline metamorphic origin; (2) an Apennine sector of mostly sedimentary origin with a high clay component; and (3) a central alluvial area including the Padanian Plain and the Adriatic lowlands. The Padanian–Adriatic basin changed considerably during the Pliocene–Quaternary and is highly asymmetric, with its southernmost part at the edge of the Apennines. The Padanian Plain has thick sediments, in some cases to a depth of 8000 m, and one of the highest

PART | I Rivers of Europe

known sedimentation rates. The regional aquifer is mainly a monostratum despite being subdivided into several layers in some places. The geology of the area is characterised by fluvial, glacial, delta, and lagoon sediments of Quaternary age, with textures ranging from coarse gravel at the foot of the mountains to silts and clays in the lowlands, with varying porosity and permeability. The Adige River is the second longest Italian river and the third largest in catchment area. It drains 12 100 km2 from the west–central Alps to the Adriatic Sea. Originating from a spring near Lake Resia (1550 m asl), it flows south– west crossing the Trentino–Alto Adige and Veneto regions. After 409 km, its delta opens into the sea at Porto Fossone, south of Venice, between the Brenta and Po deltas. The highest peak in the basin is 3899 m asl (Ortles-Cevedale Group). A small area of the upper Adige basin is in Switzerland. Most of the Adige basin is represented by its upper Alpine area, from the source to Verona (about 270 km), as the lowland part of the river has no tributaries. In its lower course across the Padanian plain, the Adige runs almost parallel to the Po. The northern Adige basin is dominated by crystalline rocks of granite and diorite, both being hydrologically impermeable. The middle Adige basin is mainly formed by dolomite rocks laying on a porphyritic impermeable substrate and the lower river flows in an alluvial plain. Between Bolzano and Trento, the porphyritic rocks are 2000 m thick and are intensively exploited for commercial use. The Arno is the largest river of Tuscany. Its catchment is about 8230 km2 (it is ranked 5th among the largest Italian basins) with a basin relief of 1650 m. It originates in the northern Apennines and flows into the Tyrrhenian Sea near Pisa, with a length of about 245 km. The catchment is within the mountain belt of the northern Apennines, which was subject during the last phases of its evolution to an extensional tectonic phase, starting from the upper Tortonian in the west and gradually moving northeast. This phase produced a horst and graben system, aligned in a NW–SE direction, and a sequence of Neogene marine and fluvio– lacustrine sedimentary cycles. The physiography of the basin is strongly influenced by recent (Plio–Pleistocene) faulting that formed several intermontane sub-basins filled with fluvio–lacustrine deposits. From upstream to downstream, these basins include Casentino, Upper Valdarno, Middle Valdarno – Florence Plain, and Lower Valdarno. The Tiber River is the largest river of central Italy and ranked second among the largest basins of Italy. It has a catchment area of 17 000 km2 and a basin relief of 2486 m. It originates in the northern Apennines (Mt Fumaiolo) and runs for 400 km before flowing into the Tyrrhenian Sea 25 km south of Rome. The catchment is within the mountain belt of the north-central Apennines. Like the Arno, the physiography of the basin is strongly influenced by the recent evolution of the Apennine belt, with a compressive phase during the Miocene characterised by overlapping and overthrust faults, followed by an extensional tectonic phase

Chapter | 12 The Italian Rivers

that induced the creation of a series of intermontane basins occupied by extended lakes. During this phase, volcanic activity also occurred in some portions of the basin. As a consequence, four main geological areas can be distinguished: (1) karstic structures in the southeast area of the basin, mainly composed of dolomite and limestones; (2) intermontane basins characterized by marine, coastal and continental sequences; (3) volcanic structures in the southwest area of the basin parallel to the Tyrrhenian shoreline and hosting series of lakes (Bolsena, Vico, Bracciano, Albano and Nemi) generated by the collapse of volcanic structures; and (4) upper Tiber river basin, mainly composed of flysch deposits (Tiber River Basin Authority 2005). The River Tagliamento is located in the Friuli Venezia Giulia Region in north-eastern Italy. The main stem rises at 1200 m asl and the highest peak in the catchment is Mt Coglians (2781 m). The funnel-shaped catchment has an area of about 2580 km2. The mean altitude of the catchment is 987 m asl. Areas above 1000 m asl (ca. 50% of the Tagliamento catchment) are mainly forested, and almost completely unpopulated. The alpine area of Friuli mainly consists of limestone, with a spatial sequence of Silurian, Devonian, Triassic, Jurassic and Cretaceous formations north to south. The prealpine mountains mainly consist of limestone (Jurassic– Cenozoic) and Flysch s.s. (calcareous flysch, molasse). The Friulian plain, an alluvial megafan, consists primarily of Tertiary and Quaternary sediments. The upper plain consists of a vast alluvial aquifer several hundred meters deep, composed of fluvioglacial sediments of high permeability. To the south, the aquifer sediments are intermixed with layers of fine deposits (sand and clay), which reduce permeability and result in upwelling of groundwater (‘Linea delle risorgive’).

12.3.2. Climate Italy has different types of climate due to several factors: the great range in latitude (more than 10 ) and elevation (almost 5000 m), the morphological heterogeneity, and the presence of the sea. The climate is mainly ‘temperate’, but varies from ‘cool temperate’ to ‘subtropical temperate’ and is also ‘cold’ in some areas of the Alps. Precipitation varies widely due to atmospheric circulation (which generally moves from west to east), relief, and distance from the sea amongst other factors. The highest precipitation is >300 cm/ y and occurs in the eastern Alps (330 cm/y at Musi, Isonzo basin, Friuli) and in the Apuane Alps (300 cm/y at Orto di Donna, Tuscany), whereas the lowest precipitation is <50 cm/y and occurs in some areas of Puglia (43 cm/y at Manfredonia, Salso basin), Sicily, and Sardinia. Low precipitation (50–60 cm/y) occurs also in some inner parts of the Alps, such as Val d’Aosta, Valtellina, and in the upper Adige valley. Overall, the average precipitation is 99 cm/y for Italy, and part of the precipitation falls as snow (up to 600 cm/y of snow in some areas of the Alps).

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Mean annual temperature ranges from 10 to16 C, but it can be <0 C in the upper parts of the Alps and >18 C in Sicily or some coastal areas. Usually the coldest and the hottest months are January and July, respectively. Major differences in temperature between the north and south of the country occur in January. A mean temperature in January below 10 C is common in the Alps, whereas it can be 11 C in the coastal areas of Calabria and Sicily. In contrast, differences of a few degrees occur during the hottest months (excluding the highest altitudes): all coastal and flat areas have a mean temperature >22 C in July; for example 24 to 25 C in the Po Plain. Due to the particular position of the peninsula, Italian climate appears highly affected by the influence of environmental change. Significant aspects of global and regional changes include an increase in sea level; reduction of glaciated areas; increase in climate variability; increase in evaporation processes; extension of urban heat islands and growing frequency of high rainfalls. All these conditions increase the risk of land degradation, salinization and deterioration of soil structure that favour frequent slope processes with major consequences for flooding. Mariotti et al. (2002) analysed the hydrological cycle in the Mediterranean during 1948–1998, focusing their work on daily rainfall and evaporation data and the balance of atmospheric water vapour. They demonstrated how the water deficit in the atmosphere correlated positively with the North Atlantic Oscillation (increased by 24% in winter and by 9% on an annual scale). Brunetti et al. (2001) analysed daily rainfall data from 67 locations over 46 years (1951–1996). They found the number of annual rain days decreased and the daily average of the intensity of rainfall increased significantly in winter. In northern Italy, the increase in rainfall intensity is mainly due to extreme events, while in the south average daily rainfall increased. Extreme rain events increased from the beginning of the 1970s, but low threshold events also had the highest and the lowest frequency in the past 120 years. According to the Comitato Glaciologico Italiano, Italian glaciers have been retreating from the beginning of the last century to the 1950s, when a period of expansion started and culminated in the early 1980s. Since then, most glaciers started to retreat again at a mean value of 4.8 m/year, and the mean elevation of 90 representative glacier fronts increased by 18 m/year. The retreat was highest in the Lombardia region, followed by the Triveneto and Piemonte glaciers. In the Po basin, the atmospheric circulation which drives the local climate is strongly dependent on the orographic features of the basin. The Alpine system buffers the Padanian Plain from cold northern winds, and modifies the circulation of the lower atmosphere, inducing changes in wind direction with a characteristic ‘barrier effect.’ The Apennine system buffers the Liguria region from the northern winds and blocks the sea-mitigation effect from reaching the Padanian Plain. It also partially abates the humid

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western winds and reduces the direction of the Atlantic cyclones. Climate is further mitigated by the large preAlpine lakes. Most of the Po basin area has mean temperatures between 10 and 15 C and consists of the lower part of Alpine valleys, the Lake District, part of the Maritime Alps and the Padanian Plain. Lower temperatures (5–10 C) occur in the Alpine and Apennine areas of average elevation, whereas higher values are restricted along the coasts. Elevation rather than geographical setting appears to drive the temperature regime. Five different patterns can be identified: continental, Alpine sub-littoral, western sub-littoral, Padanian sub-littoral, and Apennine sub-littoral. The highest precipitation is recorded in the Lake District, and in areas between 2000 and 2500 m asl. In spring (March–May), strong rains (50–70 cm) occur in the pre-Alpine region around Lake Maggiore, the Dora Baltea valley and the Apennines. In summer (June–August), as much as 40– 50 cm of rain falls in the Lombardia pre-Alps and along the northern ridge of the trans-Padanian valley. At the same period, rain recorded in the lowlands is 15–20 cm and 20–30 cm in the Apennines. Precipitation in the Adige basin ranges from values as low as 40–50 cm/year in Val Venosta to 160 cm/year in the upper Avisio basin. The seasonal distribution of precipitation is also quite different between the upper basin, characterized by a continental climate, and the lower part, with a sub-littoral climate. In the upper area, precipitation is highest in summer and lowest in winter, whereas in the lower basin precipitation is higher in autumn than in spring. Discharge is generally higher in spring–early summer, when snowmelt and rain contribute to total runoff. The intensity of rain is highest in the Lessini mountain range (up to 55 cm in 5 days). The Arno basin lies in the temperate climatic zone with dry summers. Mean annual temperature decreases progressively from the coast towards the inner basin, with a more significant reduction in the middle Valdarno. Monthly temperatures progressively increase from January to July, and then decrease from July to December. Minimum values occur in January–February and maxima in July–August. In general, the annual rainfall pattern is characterised by a summer minimum in July, and two maxima, one in November and another one in late winter. Mean yearly rainfall varies in relation to relief, ranging from 80 to about 180 cm on the Apennine ridge. Gozzini et al. (2007) analysed historical series of hourly precipitation data from two rain gauges in Tuscany: one near the coastline (Viareggio 1945–2002) and one in the inland mountains (Vallombrosa 1930–2005). This analysis showed a modification in the events distribution with a marked increase during autumn (September–November) and a reduction in winter. It confirmed the increase of intense and extreme hourly precipitation in autumn relative to the rest of the year. Temperature data from the Florence weather station confirmed a rise in temperature, in particular the maximum mean annual temperature (0.6–1.1 C/100 years).

PART | I Rivers of Europe

Climatic characteristics of the Tiber basin are similar to those of the Arno basin. Mean annual temperature ranges from 16 C at the sea level to 3.2 C at 2200 m asl The precipitation regime, based on monthly rainfall distribution, can be classified as sub-coastal. It is characterized by two maxima values in autumn and spring (highest in autumn) and two minima values in summer and winter (lowest in summer). Often the precipitation regime reflects a marine precipitation regime with a summer minimum and winter maximum. Mean annual rainfall is about 120 cm, ranging from 70 cm in coastal areas to 200 cm along the central ridge (Tiber River Basin Authority 2005). The climate of the Tagliamento catchment is alpine in the headwaters and mediterranean in the lower reaches, giving the river a flashy flow regime. The steep environmental gradient from north to south is associated with climatic differences; for exmple annual precipitation ranges from 310 to 100 cm per year and mean annual temperature from 5 to 14 C. The southern fringe of the Carnian and Julian Alps frequently receives very intensive rainstorms, resulting in severe erosion, especially in the alpine area. Torrential rainfalls, steep slopes, and extensive sediment sources generate high floods and massive sediment transport rates.

12.3.3. Land Use Patterns Land use has changed considerably over time, with increasing intensity after the Neolithic. For example, in the central Po plain much of the original vegetation cover disappeared during the Bronze Age (Marchetti 2002). Since the Etruscan–Roman period, agricultural activity, together with changes in climate, became the progressively dominant process changing land use patterns. Climate directly affected the intensity of erosion and indirectly influenced land use changes. An initial cold and rainy climate increased the intensity of soil erosion on hillslopes. A climate warming occurred around 300 BC and contributed to the spread of the Romans in the Mediterranean. During the Roman Age, at least 60% of the Po plain was deforested and converted to agriculture. As a consequence, intense soil erosion occurred as documented by the delta increase of large rivers (Po, Arno, Tiber). Centuriation was a typical widespread division of cultivated lands by a regular grid of roads and ditches introduced by the Romans, which started in the 2nd century BC and continued for about four centuries. At the end of the Roman period, migration of Asiatic populations towards the west, in coincidence with a coldhumid climatic change, caused a crisis for agriculture by reducing rural populations and cultivated lands. This situation continued for most of the early Middle Age, being reflected in a slight erosion of the delta of major rivers. Starting in the 10th century and for most of the late Middle Age, the rural population increased and, consequently, the amount of cultivated lands. After a temporary population reduction in the 14–15th century caused by the ‘black

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death’, demographic growth was stimulated by the feudal reorganization occurring in the late Middle Age. Agriculture was also favoured by milder climatic conditions. Deforestation accelerated during the climatic phase known as ‘little ice age’ between 1550 and 1850. Timber harvesting reached a peak in the late 1700s, resulting in considerable delta enlargement. Around the late 19th century, a significant policy change in water management was recorded as hydraulic developments shifted from the valley floor to upland areas with the issuing of the first laws on reforestation (1865, 1877) and construction of weirs along mountain streams. The change in river management increased during the early 20th century with the issuing of new laws (1912, 1923, 1933) encouraging reforestation, slope stabilization, and construction of weirs in upland portions of rivers. Since the end of World War II, Italy has undergone a substantial economic transformation involving industrial growth and development of large urban areas. The proportion of employment in the agricultural sector decreased from 45% of the total labour force in 1951 to 19% in 1971, whereas that of the industrial sector increased from 22% to 43%. This change occurred so rapidly and unplanned that it was impossible to ensure rational land use in accordance with the availability of natural resources, water in particular. During the last decades, economic development associated with industrialization resulted in progressive population migration from rural areas to cities. Abandoned croplands are often overgrown by shrubby vegetation, typical in areas with Mediterranean climate, thus reducing the volume of sediment supplied to rivers. Presently, land use patterns vary within the different physiographic units. Alpine and Apennine mountain areas are dominated by uncultivated lands, forests, and pasture; northern Piedmont and central and southern hilly areas are dominated by vineyards, crops and olives; the Po plain and other alluvial plains are characterised by a variety of cultivated lands, pastures and grasslands; and urban areas occupy a significant percentage of the country and are concentrated along main alluvial valleys and coastal plains. Climate anomalies that have recently occurred in southern Europe and particularly in Italy caused great concern for various water-dependent activities, especially in areas where the natural availability of water has been widely acknowledged as supporting economic development. In the northern plains of Piedmont and Lombardy, where irrigation has been used for centuries, the decrease in average rainfall has caused serious problems for farmers accustomed to withdrawing water from rivers and lakes. In southern regions, rainfall shortages have exacerbated the problem of meeting some essential water demands, including water for potable and domestic use, especially during summer. There are presently 500 storage reservoirs spread across Italy. The impact of water storage has been detrimental to aquatic life, as water withdrawal is particularly intensive in the absence of other resources. Low flows have also increased pollution levels in rivers.

12.4. GEOMORPHOLOGY, HYDROLOGY, AND BIOCHEMISTRY 12.4.1. Geomorphology The geomorphology of the Po River has been impacted in a variety of ways such as narrowing of the riverbed, channelization, removal of side arms, restrictions to water access, alteration of wetland habitats, and interruptions of ecological corridors. Historical analysis shows that the Po channel pattern remained relatively unchanged for about 150 years until the 1950s–1960s (Govi & Turitto 1993). Beginning in the 1950s, human activities have deepened the riverbed by dredging, channelized the river, and reduced its length. There has also been a decrease in sediment supply and the river has become incised and restricted to a single channel. Channel narrowing (up to 50–60%) and slight to moderate incision have been dominant processes in the upper basin, whereas bed-level lowering, up to 4 m, dominates the middle and lower basin (Surian & Rinaldi 2003). Sediment mining has been identified as the main cause of the channel change that took place from the 1950s. Studies carried out in the 1990s suggested that incision at that time should be generally finished, but there are some reaches where the channel will continue to incise, even though sediment mining no longer occurs (Govi & Turitto 1993; Lamberti & Schippa 1994). Under its current morphology, the Po River responses to high flows has yet to be determined because in the last 40 years peak discharge has been lower than any previous maximum flood. Between 1801 and 1951, the Po alluvial plain was flooded once every 10–12 years with flood levels progressively increasing because the embankment system was continuously extended and strengthened (Govi & Turitto 1993). The Adige River basin has been forged by glacier erosion and deposition, with different effects in different geological settings. In metamorphic crystalline areas, the valleys are least incised and have a rather uniform gradient. In calcareous and dolomite areas, valley forms may be quite different with gorges and steep canyons. Despite its wide flood plain, the river lateral mobility is low in the upper reach since the river is constrained by large alluvial fans and has been mostly channelized during the 19th century. The plan morphology of the river is straight, sinuous and, in the lower mountain reach, also meandering. Average slope is 0.016 from the source to Merano and 0.0015 from Merano to Verona (Photo 12.6). Downstream of Verona, the river changes from sinuous to meandering (Photo 12.7). In the last 23 km, the riverbed is slightly below sea level. The consequences of widespread chanalization along the entire river are: (a) a relatively narrow channel that varies from tens of meters to about 200 m, (b) a small number of bars and islands, and (c) low lateral mobility of the channel. The major towns crossed by the Adige are Merano, Trento, Rovereto, Verona and Legnago, whereas the main tributary, the Isarco River, flows through Bolzano.

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In the Arno basin, the main river consists of reaches cut into unconsolidated sediments of intermontane basins, alternating with narrow bedrock-controlled reaches. From the most downstream gorge to its junction with the Era River, the Arno flows through a wide alluvial plain developed on Pliocenic marine deposits. The lower reaches cross the coastal plain of Pisa and form a delta, whose cuspate morphology was developed by the river in the past. From such a physiographic setting, the river can be subdivided into a series of main alluvial reaches (Casentino, upper Valdarno, middle Valdarno–Florence Plain, lower Valdarno–Pisa Plain). At present, channel morphology varies from almost straight with alternate bars (upper and middle reaches) to sinuousmeandering with fixed banks along the lower reach and coastal plain. Channel gradients along alluvial reaches vary from 0.005 (Casentino) to 0.0002 (Pisa Plain). Two dams were built between the Casentino and upper Valdarno. Channel platform and bed elevation are maintained by concrete along the urban areas of Florence and Pisa. Bed sediments are distinctly bi-modal and composed of sand and gravelsized clasts. Mean particle size of the bed material ranges from coarse gravel and pebbles in the upper reaches to fine gravel and medium sand in the lower Valdarno. Most of the present channel morphology is a result of river training and straightening projects. Historically, the first embankments on the Arno were built in Roman times for flood protection of the main towns. The first artificial cut-offs were made in 1340, just upstream of the mouth. Starting in the Renaissance Period, there was an increase in river training works including construction of diversion canals, channel straightening, and meander cutoffs. The first maps of Leonardo da Vinci, dated early 1500, depict the Arno as a braided river with a large channel bed upstream and downstream of Florence, and it was meandering in the lower Valdarno. Between the 18th and 19th centuries, several additional river-training developments were built to provide flood protection and to convert land for agriculture. Starting from the late 19th century, stream channel dynamics have been influenced mainly by reforestation and upland sediment retention as a result of land management laws (1877, 1912, 1923, 1933), sediment mining, especially after World War II, and dams that became operational in 1957 (Figure 12.2). Widespread channel incision occurred during this period, resulting in bed lowering around 2–4 m in the upper Valdarno, between 4 and 6 m in the Florence Plain, and a maximum 5–9 m in the lower Valdarno. Channel incision was related to changes in landuse and land management practices occurred at the end of the 19th century, and more intense bed lowering between 1945 and 1960 from sediment mining and dam construction. The configuration of the Tiber River is strongly influenced by its basin physiography and recent (Plio–Pleistocene) normal faulting. These features caused the river to be NW–SE aligned with short reaches having almost perpendicular orientations. The first upland reach crosses prevailing marly arenaceous hillslopes. The river then flows

PART | I Rivers of Europe

FIGURE 12.2 Arno River: long-term annual sediment transport rates.

through the gorge of Monti Rognosi where Montedoglio dam is now located. It then crosses the Valtiberina, and has a braided morphology. Downstream of this valley, the river flows as a single-thread and crosses a series of intermontane basins derived from normal faulting tectonics before flowing through a NS valley over the fluvio–lacustrine sediments of Tiberino Lake. The river then flows in a SW direction through the calcareous gorge Gola del Forello with Corbara dam downstream of it. After the confluence with the Paglia River, the Tiber flows NW–SE through a valley of volcanic rocks from Monti Vulsini. Here is the confluence with its main tributary, the Nera River. Downstream, the river assumes a NE–SW alignment to the coast near Rome and enters the Tyrrhenian Sea. The river delta has a cuspate morphology since historical times. The history of human impacts on the Tiber is similar to that of the Arno River, except that the lower river was strongly influenced by the development of Rome (Photo 12.8). The first major impact on the river was the construction of embankments for flood protection in Rome. Next, river training, channel straightening and meander cut-offs, and construction of diversion canals occurred with increasing intensity over time. The river experienced severe bed degradation during the 20th century as a consequence of reforestation and upland sediment retention, sediment mining and dam construction. Along the Tagliamento, strong changes in climate, flow energy, sediment calibre and riparian tree species occur (Gurnell et al. 2001; Tockner et al. 2003). The Tagliamento exhibits a characteristic sequence of constrained, braided and meandering river styles (Photo 12.5). The ca. 150 km2 riparian corridor consists of five major landscape elements: surface water, bare gravel, vegetated islands, riparian forest and topographical low areas that are unforested. The first three landscape elements form the active corridor with a total area of 61.7 km2. The river retains an intact riparian margin, with a total area of 32 km2, throughout almost its entire length. Considerable parts of topographically low areas, adjacent to the meandering and regulated sections in particular, are under other land uses, primarily agriculture (Tockner et al. 2003). The active zone of the Tagliamento reaches a maximum width of about 2 km in the upper part of the coastal plain section. In some reaches the river divides into more than 10 channels with a maximum

Chapter | 12 The Italian Rivers

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PHOTO 12.5 The extraordinary richness of fluvial forms of the River Tagliamento (Photo: Bruno Boz).

PHOTO 12.6 The River Adige and its valley in the middle course: evidence of the severe taming of this river (Photo Autorita di Bacino dell’Adige).

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PHOTO 12.7 The River Adige in the lower course, where it forms wide meanders (Photo: Autorita di Bacino dell’Adige).

shoreline length of 22 km/km and a total shoreline length along the entire river corridor of 940 km at around mean water level (based on an analysis of 1:10 000 scale maps). The total stream network length for the entire catchment is 2726 km, corresponding to an average stream density of 0.85 km/km2

12.4.2. Hydrological Regime Italy has three main precipitation regimes. The first one, typical of some rivers in the Alps, is largely snow fed and exhibits peak discharges in summer. The second one, typical of northern Italy in the pre-Alps and northern and centre

PHOTO 12.8 The River Tiber crosses Rome; in the background St. Peter’s Basilica (Photo: Anna Polazzo).

Chapter | 12 The Italian Rivers

FIGURE 12.3 Mean monthly discharge of selected Italian Rivers.

Apennines, has one peak in spring and one in autumn, and low discharge with frequent droughts in summer. The third one, the ‘Mediterranean regime’ typical of southern Italy, has a peak in winter and little precipitation in summer. The runoff ratio varies widely from 68% in the north to 45% in the centre and south. The ratio is 30% for Sicily and Sardinia. For large rivers, the highest ratio is 103% for the Brenta River, northern Italy, and the lowest is 13% for the Bradano River, southern Italy. The rivers also show different hydrologic regimes that reflect these differences in precipitation (Figure 12.3). The Po River has many Alpine and Apennine tributaries. Alpine tributaries have higher and more regular discharge than tributaries from the northern Apennines. These last are characterised by unpredictable and destructive floods in spring and autumn that in turn cause flooding of the Po. Apennine tributaries also have high sediment transport and historically, before extensive river regulation, a high deposition rate shifted the Po channel towards the north. In the Padana Plain, exchanges between surface and ground water are rather complex, with some down-welling dominated streams and others mostly fed by subsurface inputs (up-welling). Soil permeability varies greatly in the basin and impermeable bedrock characterises the Alpine area while permeable alluvial deposits dominate in the lowlands. Thus, headwaters have a diffused superficial runoff, whereas water in lowlands penetrates into the phreatic zone. As the tributaries leave the mountain basins or the pre-Alpine lakes, they undergo substantial change due to water loss for irrigation and down-welling. Hydropower production, canalization, and rice fields have severely altered the entire lowland river ecosystem. About 80 km3 of water flow in the Po River each year (40% of the total volume of all basins in Italy). Average annual precipitation equals 1108 mm (database: 1918– 2006). Maxima values are found in the Alps (>2000 mm) and minima occur in the eastern section of the Plain (<700 mm). After 2003, precipitation has been decreasing due to climatic change and inputs to the river have been the lowest recorded in history.

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The Po and its 141 tributaries have a total length of 6750 km. This length also includes artificial canals in the lower floodplain, built for land drainage and irrigation and are closely connected to the Po river. The large pre-alpine lakes (Maggiore, Como, Iseo, Lugano, Garda and Orta) have a total volume of 130 km3 (Barbanti and Carollo 1993) and regulate the flow of Alpine waters to the lower floodplain. Lastly, water lost by evapotranspiration and aquifer recharge equals 31.2 km3/y. Although the volume of groundwater moving into the aquifer is difficult to calculate, it is estimated at 9 km/y and this value is an underestimate for areas such as the springs in the Padanian Plain. The maximum discharge of the Po River was 10 300 m3/s (1951) and the minimum 168 m3/s (2006) (Autorita di bacino del fiume Po 2006). Historical flood data for the Po is available since the year 700. Low flows, on the contrary, are difficult to analyse due to the lack of continuous monitoring. There is a trend of increasing maximum water levels downstream that is related to the increasing length and height of embankments. As a consequence, floods are more controlled downstream and the flood wave is related to rainfall events in tributary watersheds and to the morphology of lowland reaches. The Po catchment has complex hydrography and orography because of its Alpine and hill-slope waterbodies (Piedmont), Alpine streams regulated by lakes (Lombardia), and Apennine streams (Emilia), all of which have different hydrological regimes. As a consequence, during rainfall events, the flood regime varies along the Po according to the different flow contributions in space and time from tributaries. The largest known floods in the lower river occurred in November 1705, November 1801, October–November 1839, May 1872, October 1872, May–June 1879, and November 1951. In the upper Po (upstream of Piacenza), floods occurred on 17 occasions and mostly in the same areas. The use of surface waters for hydroelectric production is significant in several areas of the Po basin. Although this use does not ‘consume’ or degrade water quality, it has a great impact on the flow regime from flow regulation. There are about 7000 authorized hydroelectric plants in the Po basin; 88% of them are in the Alps and in large rivers in the plains. The volume of water in the 210 reservoirs totals 2000 million m3, and some water from the large lakes is also used for power production. The mean annual hydroelectric production in the basin is around 20 109 kWh, mostly from older power plants. Most of the plants began operation before 1950s. Renovation projects during the last decade often did not include the abstraction schemes in order to avoid renewing concessions. The Adige basin is divided into 26 sub-basins, and the largest one (4202 km2) is the basin of its main tributary, the Isarco River. Headwaters are mainly fed by snowmelt and rain and by 185 glaciers covering about 200 km2. All the glaciers have been retreating over the last 50 years. Hydropower was developed mostly in the 1950s when major dams were built. Today, there are 31 major reservoirs in the basin.

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The largest reservoir is Saint Giustina with a maximum volume of 183 million m3, followed by Lake Resia with 118 million m3. The total capacity of the reservoir system is 571 million m3. They drive 34 hydropower plants with a total potential power of 983 MW and possible energy production equalling 4123 GWh/y. Other 27 smaller hydropower plants can produce >1000 kW each. Due to their high capacity, Saint Giustina and Resia lakes are also used for flood control. In order to decrease peak discharge during floods, a 9873 m long tunnel was built connecting the Adige from Mori (south of Trento) to Lake Garda. This tunnel has a capacity of 500 m3/s and was successfully used during the November 1966 flood, which was the major flood in the last 100 years and caused severe damages in the Adige valley, inundating part of Trento. Other recent floods occurred in September 1960 and 1965, August 1966, October 1980 and 1993, and June 1997. Hydrological characteristics of the Adige River measured at Boara Pisani gauging station, 51 km upstream from the mouth and in operation since 1917, are listed in Table 12.2. The flow regime can be considered natural only until the early 1950s. Since then, a number of reservoirs built for hydroelectric production and irrigation have altered the flow regime. Flow regulation has considerably changed the annual hydrograph of the river and its mean annual discharge. The average discharge was 252 and 205 m3/s, respectively, in 1923–1951 and 1952–2005. The loss of about 20% of the mean annual discharge is due to climate change and growing water demands for agriculture. The hydrologic regime of the Arno River shows a large difference between minimum and maximum mean-daily discharge. Hydrological characteristics (Table 12.2) were measured at San Giovanni alla Vena gauging station, about 37 km upstream from the mouth but recording most of the flow of the basin area (8186 km2), and in operation since 1931. Annual peak discharge ranged from 321 to 2290 m3/s (1931–1966). Five reservoirs retain >1 million m3 in the Arno basin. Four were built between the end of the 1950s and 1960s with a total capacity of about 30 million m3. The 5th and largest (diga di Bilancino, 84 million m3) was finished in 1995 and used for flood control and drinking water supply. Only two of the older reservoirs (La Penna and Levane) are used for hydropower production. Their original capacity was 16 and 4.9 million m3, respectively, but it is now reduced to about 6 million m3 due to sediment filling.

FIGURE 12.4 Arno River: long-term and seasonal (insert) discharge patterns.

Other 15 small reservoirs were built during the 1960s and early 1970s, mainly for agriculture and water supply. Flow regulation from these reservoirs has effects on the hydrologic regime, and additional effects have been attributed to climatic change (Figure 12.4). Rapetti and Vittoriani (1994) analysed the changes in runoff during the interval 1924– 1983, showing a general decrease of about 0.29 cm/year associated with a parallel decrease in rainfall, although at a lower rate (0.18 cm/y). A similar decreasing trend in annual maximum discharge has also been observed. The Arno River flooded Florence sevarl times (8 major floods between 1177 and today) (Caporali et al. 2005). The most catastrophic flooding occurred on November 4th, 1966, and affected most of Italy and inundated some parts of Florence by 5.2 m. The hydrologic regime of the Tiber River is strongly influenced by climatic and geologic conditions of the basin, with large differences between minimum and maximum discharge. Highest values occur in autumn and minima during summer. The mean discharge of the Tiber in Rome is 360 m3/s in February, 217 m3/s in May, 125 m3/s in August, and 250 m3/s in November. Discharge at the river mouth has reached minima values of about 30 m3/s and maxima >300 m3/s. The Tagliamento River is influenced by both Alpine and Mediterranean, snowmelt and precipitation regimes (Ward et al. 1999). As a result, it exhibits a flashy discharge regime with peaks in spring and autumn. However, flow and flood pulses can occur at any time of the year. At Pioverno (catchment area 1866 km2), it has an average discharge of

TABLE 12.2 Flow regime (in m3 sec-1) of principal Italian rivers River

Station

Period

A (km2)

NQ

MQ

HQ

HQ/NQ

Po Adige Arno Tiber

Pontelagoscuro Boara Pisani San Giovanni della Vena Rome

1917–2006 1923–2005 1931–1998 1935–2002

70 000 12 324 81 860 17 375

168 7,3 2,2 60,0

1510 234 90 225

10 300 1700 2290 1500

6131 2329 10 409 25,0

A: Catchment area upstream of gauging station. NQ: lowest measured discharge. MQ: arithmetic mean annual discharge. HQ: maximum annual discharge.

Chapter | 12 The Italian Rivers

approximately 90 m3/s, and the 2, 5 and 10 year floods are estimated to be 1100, 1600 and 2150 m3/s (Maione & Machne 1982). Downstream of Pinzano, the Tagliamento loses a large percentage of its surface flow by infiltration through a vast alluvial aquifer dominated by highly permeable gravel. In the upper part of the Friulian plain (losing zone), surface flow decreases on average by 2.5 m3/s per river km. In the lower part (gaining zone), surface flow increases by 0.3 m3/s per km (D€ oring et al. 2007). Under low flow conditions, the river here lacks surface flow (maximum dry length: 25 km). This is a natural feature of Mediterranean rivers that has been exacerbated by water abstraction.

12.4.3. Biogeochemistry Any assessment of ecological status must be supported by assessments of hydromorphology and chemistry, including pollutants. A general overview of river transport of water, sediments and pollutants to the Mediterranean Sea (UNEP/ MAP 2003; MAP Technical Reports Series 141) showed that most heavy metals such as Cd, Cu, Hg, Pb, Zn are adsorbed on the surface of suspended particles. As a consequence, sediments have an impact on ecological quality that reflects their quality and quantity, and should be part of river monitoring programmes. There are six heavy metals in the Italian list of priority substances. Recent investigations have shown elevated levels of some metals, for example Cd, Cu, Ni, Zn in the Po, Pb, Zn in the Tiber and Cd in the Arno. Direct comparisons are not always possible because of differences in study periods (Fabiani & Yessayan 2005). The major pollution source in the Po basin is organic input that triggers eutrophication in slow-flowing reaches, lakes, and the Adriatic Sea. Specific pollutants are also introduced in waters from agricultural, livestock-related, and industrial activities (such as heavy metals and pesticides). Eutrophication is the most important environmental issue to be resolved in the Po system as it is the major tributary to the Adriatic Sea, where fishing and tourism can be severely damaged by high nutrient inputs. Restoration and conservation of the large pre-Alpine lakes is another priority as they supply water for municipalities and agricultural areas of the Padanian Plain and for tourist activities. Nitrate is the main contaminant in groundwaters, although other substances such as arsenic and pesticides can be important in localized areas. The main source of nutrients in the Po basin is agriculture (nitrogen 46%, phosphorus 60%) and livestock activities (nitrogen 39%, phosphorus 33%). Civil and industrial activities have less impact, contributing 15% of the nitrogen and 7% of the phosphorus to the river. Due to hydrogeological conditions, the high plain (an area of high quality groundwater) is vulnerable to pollutants and to other hazards. The main anthropogenic pollution of groundwater comes from halogenic compounds, nitrate and herbicides (Giuliano & Pellegrini 1993). Recent studies

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showed a significant contribution of diffuse sources that can contaminate groundwater. The amount of nitrogen that leaches into the soil and potentially contaminates phreatic water is 96 000 tons/year, and the total amount of nitrogen transported from surface water to the Adriatic Sea is 167 000 tons/year. This amount corresponds to the values of N load measured in the river at Pontelagoscuro (150 000 tons/year) in 1995. Pollution from point sources is due to deficiencies in sewage systems, civil and industrial wastewater collection, and treatment plants. The potential negative impact of diffused sources on water quality varies among areas, but is on average higher in areas north of the Po than south of it. Livestock bred in the Po basin include 3.2 million cattle, 4.7 million pigs, and 40.4 million poultry, whose wastes together produce 230 000 tons of nitrogen and 144 000 tons of phosphorus. The main diffused source of eutrophication is the incorrect use of fertilizers with a consequent high input of nutrients from agricultural land. In the Padanian Plain and adjacent areas, about 310 000 tons of nitrogen and 90 000 tons of phosphorous are used annually as commercial fertilizers. Pesticide use equals 18 200 tons annually. A further impact is the reduction of natural flow from excessive withdrawal for irrigation in the Apennine basins and for hydroelectric power in the Alpine basins, which increases pollution levels in surface waters. Alteration of riparian zones has also had a significant effect on surface waters. The first documented algal bloom in the Adriatic Sea occurred in 1969. In 1975, a large flagellate bloom caused diffuse anoxic conditions in deeper waters. After 1988, a reduction in the intensity, extent, and duration of summer– autumn algal blooms and other phenomena associated with eutrophication (coloured and bad-smelling water, anoxia in deeper layers, and mortality of benthic organisms) was recorded. Recent analysis shows a decrease of phosphorus in the Adriatic Sea, whereas the concentration of nitrogen remains the same. Nitrogen levels vary with the amount of rainfall and thus with the Po River discharge. The N/P ratio has been increasing and varies seasonally. The average N/P ratio from 1983 to 1990 was around 50 and increased to 130 in 1990–1993, confirming that phosphorous was limiting algal growth. A comparison between years confirms the high inter-annual variability in trophic status of coastal areas and its relationship with the Po River. The water quality of the Adige is rather good and its chemical quality has been improving in the last decade. In the middle basin (Province of Trento), Biological Oxygen Demand between 1991 and 2002 was generally highest in winter, whereas other parameters showed no significant seasonal variation (APPA 1991–2002). According to the biological index used in Italy, the Extended Biotic Index (Indice Biologico Esteso, IBE) (Ghetti 1997), water quality of the Adige ranges between the second and third class (Provincia Autonoma di Bolzano 1995; Provincia di Verona 1997). Average annual values of total nitrogen and total phosphorus transported by the Adige at Trento during 2000–2001 was

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FIGURE 12.5 Arno River: longitudinal distibution of nutrients (nitrate, total P) and biological and chemical oxygen demand (monthly values in the period 2001–2005).

8518 and 417 tons, respectively (APPA 2004). Suspended sediment load measured at Boara Pisani gauging station from 1929 to 1941 and from 1958 to 1971 decreased by 28% from 1 145 930 to 824 720 tons/year because of flow regulation which occurred since the early 1950s. The density of civil buildings in the Arno basin is about 250 h/km2, higher than the 188 h/km2 national average (Arno Water Authority). The basin comprises the main industrial and agricultural areas of Tuscany, and hosts a large number of tourists. Agriculture is mainly represented by vineyards near Florence (Chianti production) and olive trees. The provinces of Florence and Arezzo contribute to 62% of the nitrogen load (Figure 12.5). Average annual total nitrogen and total phosphorus loads to the Tyrrhenian Sea equal around 7500 and 400 tons, respectively (Tuscany Region 2005). In the past 50 years, human pressures on the Tiber River by civil and industrial developments, infrastructure, and hydraulic works have increased in number and size. The Tiber basin hosts several large urban areas, including Rome, with over 3.6 million inhabitants. In the upper and middle reaches, the Tiber has a high degree of self-purification with good water quality. Environmental conditions worsen in the lower section from excessive pollution loads. The effect is stronger where the river crosses urban areas, and reaches a critical threshold downstream of Rome because of inadequate wastewater treatment. Organic pollution of the Aniene River, one of the main tributaries, is quite severe and the ecological integrity of the river is questionable. Finally, waters of the Tiber River have been overexploited. Water withdrawals for industrial and agricultural uses, often illegal, and for hydropower production alter the flow regime by lowering water

PART | I Rivers of Europe

levels. Abstraction of water is one of the main causes of river degradation because the reduction in discharge increases the concentration of pollutants and hinders natural self-purification. The Tagliamento is classified as an ‘alkaline river’ with a pH >7.5, a specific conductance of >250 mS/cm and a predominace of Ca2+ (about 100 mg/L upstream of the confluence with the Fella River), Mg2+ (20 mg/L) and HCO3- (ca. 160 mg/L). The chemical composition of surface waters reflects the geological setting of the catchment. Along the river, specific conductance decreased from 2000 mS/cm in the uppermost headwaters to about 450 mS/cm in the lower reaches. High specific conductance mainly results from the weathering of evaporitic sediments (gypsum). Sulphate concentrations of up to 2000 mg/L are classified as extreme values compared to usual concentrations in perennial world rivers and streams (Tockner et al. 2003). Water quality is high along almost of the Tagliamento corridor (low nutrient and organic matter concentrations). Concentrations of phosphorus and ammonium are very low along the entire river. Concentrations of nitrate (NO3–N), however, increase from upstream to downstream with peak values of over 1.6 mg/L. Dissolved organic carbon (DOC) concentrations are relatively constant at about 1.0 mg/L. Particulate organic carbon (POC) ranges from 0.18 mg/L at low flow to 12.1 mg/L during high flow (Kaiser et al. 2004). There exist several major point pollution sources such as local effluents from villages (e.g. Forni di Sotto), major inputs from mills between Cavazzo and Amaro, water contributed from the Arzino tributary, and agricultural inputs in the Rivis area. However, the self-purification capacity of the river is very high, primarily as a consequence of intensive surface–subsurface exchange processes along the dynamic river–floodplain system. A few river kilometres downstream of pollutant inputs, water quality reverts again back to preimpact conditions.

12.5. AQUATIC AND RIPARIAN BIODIVERSITY The checklist of Italian Flora lists 6711 species, divided into 196 families and 1267 genera. These data not only place Italy first in Europe for the number of species, but also highlight the high diversity of taxonomic types and the high number of endemisms (686 species). Recent investigations emphasized a decrease in biodiversity and the urgent need of environmental conservation and restoration measures to protect native vegetation and fauna. The disappearance of taxa with high natural value is often due to chemical pollution and a reduction or fragmentation of habitats caused by human activities. Flora in spring reaches of the Po River is represented by species associated with clear waters and constant discharge, including thick cushions of epilithic mosses such as Schleicher’s thread-moss (Bryum schleicheri) and the

485

Chapter | 12 The Italian Rivers

fountain apple-moss (Philonotis fontana) associated with the yellow saxifrage (Saxifraga aizoides). Other common phanerogams are the starry saxifrage (Saxifraga stellaris), the bittercress (Cardamine amara) and the marsh marigold (Caltha palustris), belonging to the Cardaminietum amarea association. The two-flower violet (Viola biflora), the chickweed willow-herb (Epilobium alsinifolium) and associations as the Helosciadetum are also common. The epi-metarhithron and hyporhithron reaches comprise brook and stream reaches, characterized by low water temperature, high dissolved oxygen and velocity that reduce deposition of organic and inorganic matter and cause oligotrophic conditions that in turn reduce primary production. These streambeds are dominated by sheer rock, boulders and stones, with acid waters due to the siliceous bedrock. Few areas are dominated by carbonates. Riparian vegetation along these small streams is mainly represented by hygrophilous woods of speckled alder (Alnus incana) along valley bottoms and on detritic conoids. Frequently associated to these woods are several species of willows and the buttercup (Ranunculaceae) and species of Apiacea. The middle Po is mostly epipotamon and comprises transition reaches between mountain and lowland areas. In this section, the Po begins to meander and small islands appear. Current velocity is variable and water temperature warmer and with lower dissolved oxygen. The riverbed becomes dominated by gravel, pebbles and sand. Riparian vegetation is sparse due to frequent changes in discharge and intense erosion and deposition. This condition selects fast colonizers such as curlytop knotweed (Polygonum lapathifolium), lady’s thumb (P. persicaria) and fat hen (Chenopodium album) of the association Poligono–Chenopodietum. Other plants frequently found in these habitats are Epilobium hirsutum, Veronica anagallis-aquatica, Echinochloa crusgallis; Barbarea vulgaris and Xanthium italicum. Where floods are less frequent, more stable vegetation occurs, mainly represented by shrubby willows such as Salix purpurea and Salix eleagnos associated with bouncing bet (Saponaria officinalis) and European dewberry (Rubus caesius). Moving inland from the river margin, hygrophilous forests of golden willow (Salix alba) and black poplar (Populus nigra) develop near inland mature oaks (Quercus spp.). In these reaches, algae increase both in abundance and diversity, and communities are dominated by Cladophoretum glomerateae and Vaucherietum rheobenthicum associations that comprise a variety of Cloroficeae, Xantophyceae and Diatomeae. After the confluence with the Ticino River, the Po enters the lowlands at only 80 m asl. In this rather monotonous and flat agricultural landscape, the Po is a metapotamon reach characterized by oxbows, side channels, meanders, islands and braided sections. The substrate is dominated by sand, clay and mud, frequently impermeable, the flowing water has rather high temperature, low dissolved oxygen and high turbidity. Instream vegetation is emerged and rooted, floating, or submersed and rooted. The most common species are the European white water lily (Nymphaea alba), the yellow

pond lily (Nuphar luteum), the Eurasian water milfoil (Myriophyllum spicatum), the whorl–leaf water milfoil (M. verticillatum), the shining pondweed (Potamogeton lucens), the water chestnut (Trapa natans) and the water violet (Hottonia palustris). In shallow and eutrophic reaches, algal blooms mix with floating water ferns (Salvinia natans), common duckweed (Lemna minor), and European frog-bites Hydrocharis morsus-ranae. In shallow waters along the shore, common species are the common water–plantain (Alisma plantago acquatica), the flowering rush (Butomus umbellatus), the water pepper (Polygonum hydropiper), the common reed (Phragmites australis), the broadleaf cattail (Typha latifoglia), the branched bur-reed (Sparganium erectum), the lakeshore bulrush (Schoenoplectus lacustris), the larger bindweed (Calystegia sepium) and the bittersweet (Solanum dulcamara).

12.5.1. Invertebrates Italy has one of Europe’s highest levels of biodiversity with 47 225 terrestrial and freshwater species of metazoans recorded (Ruffo & Stoch 2006). Endemic species account for about 10% of the Italian fauna and most species are invertebrates with low dispersion ability or living in restricted habitats. The highest rates of endemism can be found among the freshwater epigean fauna such as, for example, the genus Parastenocaris (Crustacea, Harpacticoida) with 90% of the 26 species endemic. Regarding running waters, 49 of 150 species of stoneflies known for Italy are endemic, 72 of 402 species of caddisflies, and 35 of 151 species of water beetles of the family Hydraenidae. About 1000 species are non-native and most are insects introduced accidentally or for biological pest control in agriculture. According to the Checklist and Distribution of Italian Fauna (Ruffo & Stoch 2006), the most endangered freshwater species are stoneflies (79 endangered species), crustaceans (75), mayflies (40), and dragonflies and damselflies (16). Unfortunately, the lack of information regarding the distribution of stream-dwelling taxa suggests that many more species are threatened by habitat loss and pollution. Non-native crustaceans are present in Italian freshwater ecosystems, among which: Cladocera (9 species), Ostracoda (20 species) and Decapoda (4 species) (Occhipinti-Ambrogi 2002). Major ecosystem threats arise from non-native species of crayfish, predominantly Procambarus clarkii and Orctonectes limosus, which are strongly expanding their distribution and competing with the native Austropotamobius pallipes. The latter is distributed from Calabria to northern Italy (Gherardi & Holdich 1999). P. clarkii is widespread and acclimatized in many zones of the Po, Arno and Tevere basins. Froglia (1978) reported a second native crayfish in Italy, Astacus astacus, with small populations inhabiting ponds and slow-flowing rivers in eastern Venezia–Giulia. Machino (1996) recorded the presence of the stone crayfish, Austropotamobius torrentium, in the Italian section of the

486

Danube basin. The river crab, Potamon fluviatile, is still present in central and southern Italy, including Sicily. For northern Italy, there are scattered records of this crab from Liguria, Romagna, Lombardia and Veneto. A massive invasion of freshwater habitats by the zebra mussel Dreissena polymorpha started in 1972 in Lake Garda, and this Caspian bivalve has now colonised most of the Po basin. In the late 1990s, it had colonised many sub-Alpine lakes and rivers such as the Brenta River. In its first part, the Po is a typical alpine lotic system, with coarse substratum, high riverbed slope and cold oligotrophic waters. This environment hosts a rich and diversified benthic fauna, characterised by orophilous and stenothermic elements. Recent studies have underlined the high biodiversity of macrobenthic fauna of the area. Fiftyseven Plecoptera species and 60 Trichoptera species have been reported, with three species of caddisflies (Stactobia alpina, Allogamus periphetes and Consorophylax delmastroi) recently described as new for science (Delmastro 2006). In the upper part, there are many taxa with Alpine distribution, such as Liponeura cinarescens (Diptera Blephariceriidae) and Siphonoperla montana (Plecoptera Chloroperlidae) (Fenoglio 2005). Also Leuctra vesulensis (Ravizza 1988), a Cottian endemism, and Dictyogenus alpinus (Plecoptera: Perlodidae), considered by Aubert (1959) the most representative element of the Alpine stonefly fauna, are present (Fenoglio & Bo 2004). It is well known that human activities shape and modify lotic environments, but recently also mountain and Alpine streams are becoming endangered. Hydroelectric plants and artificial snow production could represent a potential danger for the rich biota of the upper Po river. After 13 km, the river enters the alluvial plain and, in the area of Martiniana Po and Revello (approximately 350 m asl), a highly permeable riverbed produces a substantial hyporheic flow. In the last few decades, drought has become a regular event in this reach due to the presence of dams and irrigation canals (Parco del Po Cuneese). For about 5–10 km, the Po riverbed can completely lack water for many weeks or even months. These ‘supra-seasonal’ droughts are mainly human-induced and affect prealpine lotic systems usually immune to this phenomenon. A recent study underlined that only few macroinvertebrate taxa appear to be able to survive in reaches with intermittent flow, suggesting that the recent increase of droughts will likely cause an impoverishment of benthic communities in prealpine rivers (Fenoglio et al. 2007). The diversity of aquatic fauna in the Adige basin is considerably high, given the wide variety of climatic conditions, which range from the mild areas influenced by Lake Garda to the alpine tundra in the headwaters. Several taxa have decreased in abundance due to habitat reduction caused by flood protection measures and land conversion, and the severe effects of water abstraction and hydropeaking induced by hydropower production. Headwaters above treeline are dominated by midges, mostly belonging to the sub-

PART | I Rivers of Europe

families Diamesinae and Orthocladinae, and blackflies. Stoneflies, caddisflies and mayflies become more frequent with decreasing elevation. The latter become dominant in lower reaches, together with non-insects such as molluscs, isopod and amphipod crustaceans, and oligochaetes (Lencioni & Maiolini 2002). As an example, the most common blackfly in the Adige headwaters is Prosimulium latimucro, followed at lower elevations by Prosimulium rufipes. Other species commonly found are Simulium brevidens, S. carpathicum, S. carthusiense, S. cryophilum, S. vernum, S. auricoma and S. argyreatum (Margoni & Maiolini 2004). Harpacticoid copepods represent the dominant taxon of microcrustaceans in the Adige headwaters, with 18 species identified (Cottarelli et al. 2001, 2005; Maiolini et al. 2005). Among the dominant species, Bryocamptus (Arcticocamptus) cuspidatus, Bryocamptus (Rheocamptus) zschokkei, and Bryocamptus (Arcticocamptus) rhaeticus are most abundant at relatively low altitudes (>2000 m asl), and Hypocamptus paradoxus and Bryocamptus (Arcticocamptus) alpestris are dominant at higher elevations (>2000 m asl). Riparian woodlands have been largely reduced along the entire river corridor and remnant areas suffer from flow regulation and lack of periodic inundations. Nonetheless, the diversity of riparian invertebrates is still rather high in these areas. For example, in one riparian forest along the middle Adige, 56 carabid species were recorded. There also was evidence of a change in biocoenosys from hygrophilous to mesohygrophilous species, due to levees that do not allow flooding of the riparian zone (Boscaini et al. 2000). In regards to freshwater invasive species, the zebra mussel (Dreissena polimorpha) is present in only a few locations in the Adige basin (Dalfreddo & Maiolini 2004), but it is expected to spread throughout most lowland waters. The signal crayfish (Astacus leniusculus) has been recorded in some locations in the province of Bolzano, where the only Italian population of the European crayfish (A. astacus) also occurs (Fureder & Oberkofler 2000). The spiny-cheek crayfish (O. limosus) is present in the middle and lower Adige and related wetlands, threatening the populations of the white-clawed crayfish (A. pallipes), already suffering from diseases and habitat loss. In the Arno River basin, a recent study of Renai et al. (2006) showed that the disappearance of crayfish populations recorded in several streams in Tuscany is not due to habitat degradation or alteration, although, historically, pollution and drought may have had an impact. In Tuscany, the effects of the heat wave of summer 2003, causing near drying of some streams, is considered a probable explanation for the reduction in population abundance and perhaps the cause of some local extinctions. Headwaters that have potentially good physical habitat for crayfish can be adversely affected by reduced baseflow due to abstraction of groundwater for water supply and are at risk of pollution from small domestic discharges. In some years, streams may dry completely and the availability of instream habitat becomes low. When their shelters are exposed to air, crayfish must move into water,

Chapter | 12 The Italian Rivers

especially in hot conditions. Since most shelters are in the banks, moving into the mid channel can leave crayfish vulnerable to desiccation and predation. The macroinvertebrate fauna shows that pollution is not presently a problem. These streams, displaying the ecological requirements for crayfish, are ideal for reintroduction programs, as non-native crayfish (e.g. P. clarkii) were not found. However, a high level of attention towards the problem of invasive species is still necessary. In Tuscany, P. clarkii have become widespread even within some protected areas (Barbaresi et al. 2001). Studies on the biology and growth of the A. pallipes complex should be intensified to improve measures of protection. Surveys also should be conducted on populations following reintroductions, as this may help to improve the success of future introductions or the conservation of the native crayfish. The Tagliamento contains a rich aquatic and riparian invertebrate fauna (Arscott et al. 2005). Along the main corridor, Rust (1998) identified 95 species of carabids, from a total catch of 2633 individuals. Forty-nine of these species (52%) are considered as characteristic for riparian habitats and 26 species (27 %) are listed as endangered (red data list of Austria and Switzerland).

12.5.2. Amphibians and Reptiles Italian amphibians number 40 species, 31 of which are present in the selected rivers (Table 12.2), about 40% of these are endemic to the Apennines and islands, and most belong to the terrestrial genus Speleomantes. Several non-native species have established populations (e.g. Pelophylax kurtmuelleri, Lithobates catesbeianus). In regards to aquatic reptiles, the non-native freshwater tortoise Trachemys scripta has several breeding populations that compete with the European species Emys orbicularis, which is endangered also because of habitat reduction in many areas. Among amphibians, the endemic Sardinian brook newt (Euproctus platycephalus) is present in the Flumendosa basin, and the few populations are considered endangered. There are four species of salamanders, the most widespread being the fire salamander (Salamandra salamandra), common in mountain ranges of continental and peninsular Italy. The Alpine salamander (S. atra) is still frequent in the upper ranges of the central-eastern Alps, while the endemic Lanza’s salamander (S. lanzai) is restricted to a few locations in the headwaters of the Po basin, in the western Alps. Lastly, the spectacled salamander (Salamandrina terdigitata) is common along all the Apennines, mostly between 300 and 900 m asl. The most common newts are: the Alpine newt (Mesotriton alpestris), mostly in the western Alps and northern Apennines, the Italian crested newt (Triturus carnifex) widely distributed throughout Italy, except the islands, the Italian newt (Lissotriton italicus), endemic of the central and southern Apennines, and the smooth newt (L. vulgaris), common from the central Apennines to the lower ranges of the Alps.

487

Toads are represented by the yellow-bellied toad (Bombina variegata) in the central-eastern Alps and by the Apennine yellow-bellied toad (B. pachypus) in the Apennines. There also are some endemic frogs, including the Tyrrhenian painted frog (Discoglossus sardus), considered severely endangered in its home range (Sardinia and smaller Tyrrhenian islands), the Sardinian tree frog (Hyla sarda), still common in Sardinia, Corsica and smaller islands of the Tyrrhenian Sea, the Italian stream frog (Rana italica) has healthy populations throughout peninsular Italy, and the Italian agile frog (R. latastei) is common in the left side of the Po watershed and all the lowlands towards the east (Mazzotti & Caramori 2004; Ruffo & Stoch 2006; Sindaco et al. 2006). The endemic spadefoot toad Pelobates fuscus insubricus lives in northern Italy, has been recently recorded along the Adriatic coast and the Po delta (Mazzotti & Rizzati 2002; Mazzotti et al. 2003; Boschetti et al. 2006). Pelobates fuscus insubricus is a priority species of community interest in need of strict protection, listed in the Annexes II and IV of the Habitat Directive 92/43/EEC, and has been object of conservation ccampaigns (for further information on this species, see Mazzotti, 2007; Crottini & Andreone 2007). Amphibians and freshwater related reptiles are listed in Table 12.3. Thirteen species of amphibians are found in the Adige basin, among these the newts Lissotriton vulgaris and Truturus carnifex, which are common in other parts of northern Italy, have reduced populations. The only priority species, according to the Habitat Directive, is the yellow-bellied toad (B. variegata), still present along the whole Adige valley but endangered because of a reduction in their specific habitats, represented by small, temporary pools in the river floodplains. Reptiles associated with freshwater habitats include the common grass and dice snakes (Natrix natrix and N. tessellata). The European pond terrapin (E. orbicularis) is extinct in the Adige valley (Caldonazzi et al. 2002). Within the Arno basin, predation by Salmo trutta trutta on different species of amphibians caused the decline or even extinction of S. terdigitata, S. salamandra, Mesotriton alpestris apuanus, R. italica, and Bombina pachypus (Stebbins & Cohen 1995). Habitat loss and drought may have also contributed to the decline of these species. Recent biomolecular research (Mattoccia et al. 2005) showed the existence of two genetically distinct and geographically non-overlapping lineages of Salamandrina: the first lineage includes the southern populations which can be ascribed to Salamandrina perspicillata and the second one comprises the central–northern populations of S. terdigitata (Mattoccia et al. 2005). Thirteen amphibian taxa were identified along the Tagliamento with the predominance of Rana latastei and Bufo bufo (Tockner et al. 2006). Amphibian richness within a given habitat was significantly related to distance from islands, fish density and water temperature. Vegetated islands and large woody debris played pivotal roles, directly and indirectly, in maintaining both habitat and amphibian diversity in this gravel-bed river.

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PART | I Rivers of Europe

TABLE 12.3 List of amphibian and reptiles species in the selected Italian Rivers Po Adige Tiber Arno Tagliamento Flumendosa Brenta Sangro Amendolea Alcantara Amphibia Urodela Euproctus platycephalus Salamandra atra Salamandra atra aurorae Salamandra lanzai Salamandra salamandra Salamandra salamandra gigliolii Salamandrina terdigitata Lissotriton italicus Lissotriton vulgaris Mesotriton alpestris Mesotriton alpestris apuanus Triturus carnifex Anura Bombina pachypus Bombina variegata Discoglossus pictus Discoglossus sardus Pelobates fuscusinsubricus Pelodytes punctatus Bufo bufo Pseudepidalea viridis Hyla sarda Hyla intermedia Lithobates catesbeianus Pelophylax kl. esculentus Pelophylax bergeri Pelophylax lessonae Pelophylax ridibundus Rana dalmatina Rana italica Rana latastei Rana temporaria

D X

X

X

X

X

D D X

X

D X X

X

X X

X

D

X D

X D

D

D

X

X

D

D

X

X

D

D

X

X X

X X

X

X

X

X

D

D

D D X

D D X

X D

D X

D X X X X

X X X

X X

X X

X X

X X

X X

X X

X X

D I X X X X X

D I X X X

D I X X X

D

D

D

D

D

X X X

X X X

X X X

X X X

X X X

X D

X D

X

X

X D

D

D X

D X

X

D D I X X X X X D D X

D X

X

Reptilia Testudines Mauremys caspica Emys orbicularis Trachemys scripta

I X I

X I

X I

X I

X

Squamata Natrix maura Natrix natrix Natrix tessellata

X X X

X X

X X

X X

X X

X

X X

X X

X

X X

X – native, I – introduced, E – extinct, D – endemic.

12.5.3. Fish Fauna Knowledge regarding the status of Italian inland fishes is still poor. There are gaps in taxonomy, in knowledges regarding the original distribution of species and the biology of several endemic fishes. However, significant gaps in taxonomy and distribution have been filled for all endemic freshwater fishes in the north-Mediterranean region (Maitland & Crivelli 1996). There are 75 species

or subspecies of freshwater fishes recorded for Italy; 20 are endemic (Ruffo and Stock 2006). Man has intentionally or accidentally introduced 29 species since the Roman Age. Stocking is a practice frequently used to improve the quantity or quality of catches and for long-term benefits on fish stocks. Twelve non-native species have breeding populations in most of Italy, eight breed only in restricted areas, and nine are only locally present or do not breed but are sustained by frequent stocking, such as the

Chapter | 12 The Italian Rivers

rainbow trout. More recently, the distribution of several local species has been artificially expanded to meet the requests of angler associations (Zerunian 2002). There are two distinct fish distribution zones in Italy: the Padana Region and the Italian Peninsular Region. The first includes northern Italy, most of the Marche, the Adriatic coast of Slovenia, and most of the Adriatic coast of Croatia. This area corresponds to the Po River basin during the last Pleistocene ice age. The second area includes all the regions of the Italian peninsula south of a line that joins eastern Liguria to southern Marche. There are eight endemic fishes in the Padana Region: Zanandrea’s lamprey, the Italian redeye roach, the Po nase, the Po loach, the Garda trout, Canestrini’s goby, the Po spring goby, and the Po river goby. Another nine taxa probably originated in the area before extending into adjacent regions: the Adriatic sturgeon, the Italian soufie, the Po bleak, the Italian orange-fin nase, the Italian river barbel, the Italian brook barbel, the Italian spined loach, the marble trout, and the Adriatic lagoon goby. The Italian peninsular region has four endemic species: the Italian orange-fin roach, the South Italian bleak, the Fibreno trout, and the Italian brook goby. The first two are found in both Tyrrhenian and Adriatic hydrographic systems, probably due to a contact route that existed in the recent geological past, and perhaps still today through karstic groundwater systems in some areas of the Apennines. The other two species are found exclusively in the Tyrrhenian side. In the past 50 years, the decline of most species, in abundance and range, has become increasingly evident. In highly industrialised regions, since the 1960s, the high diversity and abundance of species, previously recorded in many water bodies, has been substantially declining, often culminating in local extinction (Zerunian 1992, 2002; Zerunian & Taddei 1996; Zerunian & Gandolfi 1999). To date, five native fish species are considered endangered and 10 as vulnerable. The main anthropogenic factors directly affecting fish populations are probably habitat degradation, fragmentation and water pollution, introduction of non-native species, over-fishing and illegal fishing (Tancioni et al. 2006). Several factors have impaired fish communities in the Po basin. To date, the changes that have occurred in habitat characteristics have not led to extinction of any of the native fishes. However, they have frequently caused both distribution range contraction and population reductions, particularly for those species sensitive to poor water quality. The presence of 25 non-native species, most of which were introduced in the last decades, and the introduction of stocks of native species to improve fishing activities, have lead to critical problems in management (Giussani 1993). The introduction of non-native species has affected the survival of several native species, with a consequent reduction in biodiversity. For instance, numerous non-native fishes such as minnow, whitefish, pikeperch, pumpkinseed, catfish and wels were introduced in the Po for sport fishing, and have

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established stable populations. There are few long-term studies on fish populations in the Po basin. Among these, one refers to the Modena province, in the middle basin, where in 1850 the native fishes included 20 species along with 2 acclimated non-native ones. In 1950, the same number of native species was recorded but the acclimated non-native ones increased to five. In 1985, the native species Knipowtschia punctatissima was no longer recorded, and 8 non-native species were present. In 2000, the native species Alosa fallax became locally extinct while the number of nonnative and acclimated species increased to 14. Of 18 native species, 3 were critically endangered, 5 endangered and 2 vulnerable (Sala et al. 2004). In the Arno River basin, the native Salmo trutta trutta is almost certainly extinct, and existing populations are the results of introductions of populations coming from the Atlantic part of Europe. During the past 20 years, the distribution and abundance of the Arno goby (Padogobius nigricans), one of the few endemic species, have been in constant decrease. The species is now restricted to the Arno upstream of Florence. This reduction is mainly caused by pollution and the Arno goby is now protected by a regional law (LR 56/2000). The soufie (Leuciscus souffia) has also been reduced by competition with stocked trout in the upper basin and are found in lower reaches that are unsuitable for their ecological requirements. In some headwaters where trout stocking was experimentally stopped, soufie populations have expanded. The tench (Tinca tinca) was once widely distributed throughout the basin but is now rare because of habitat loss and pollution. Stocking of this species has been ineffective and the species is the most vulnerable among the native species (Nocita 2002). The European catfish (Silurus glanis) was introduced in the Arno about 20 years ago. Smaller (generally 20–50 cm long) individuals are found in upstream reaches while they are common below Florence where they can reach 120–220 cm in length (Gualtieri et al. 2006). Analysis of gut contents revealed that they feed mainly of Carassius auratus, Alburnus alburnus alborella, Anguilla Anguilla and small crustaceans. The rate of growth in lowland areas is faster than in northern Europe and northern Italy, probably because of good food resources, mainly represented by C. auratus and other native cyprinids. Their impact on the Arno fish community has been severe, especially in respect to eel populations. Eels are a typical species of the Tiber and related wetlands. Fisheries devoted to their capture have a long tradition in the Lazio region. Eel declines occur throughout Europe and in the Tiber recruitment strongly decreased from the mid 1990s. Captures of ‘glass eels’ in the Tiber have been recorded from 1990 and amounted to about 400 kg per season until 1994. Afterwards, densities constantly declined with less than 100 kg caught in recent years (Ciccotti et al. 2004). In Umbria, major threats to fish populations are habitat reduction (dikes, dams and canalization), reduction and

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alteration of natural flow regimes, and pollution. In the Nera basin, which is the most suitable for salmonids, there is on average one fish barrier every 2 km. Only 14 species of the 39 recorded for the Nera basin are native and the other 25 are non-native. Among the recently non-native species are the well and sadly known wels (Silurus glanis L.), ruffes (Gimnocephalus cernuus L.), and false Harlequin (Pseudorasbora parva Temminck and Schlegel). Lesser known non-native species have proven to be a serious problem for fish diversity and conservation: The introduction of rudd (Rutilus erythrophthalmus Zerunian) in lake Piediluco caused the local extinction of Bonaparte’s roach (R. rubilio Bonaparte), while the introduction of the Padanian goby (P. nigricans Canestrini) is increasingly menacing the distribution of the brook goby (Padogobius martensii Gunther) in many streams. In Sardinia, there are 7 native species and 11 non-native ones. Among the most threatened native species is the eel (Anguilla anguilla L.), with decreasing abundance and now absent in several parts of its former distribution. The main cause is the many dams, particularly those on the Flumendosa and Tirso. The delta was the main recruitment site for the species. The twait shad (Alosa fallax Lacepede) is still present in isolated and decreasing populations in some reservoirs, such as Flumendosa. The sea lamprey (Petromyzon marinus L.) was last recorded in 1973 in the Tirso River near Ogliastra. Salmo (trutta) macrostigma Dumeri, once the only salmonid species present in the island rivers, is now restricted to a few isolated reaches due to hybridization with the non-native Salmo trutta trutta and difficulty in reaching upstream spawning areas (Massidda & Orru 2002). The Tagliamento contains a rich fish fauna. Thirty fish species (including six freshwater species indigenous to the Adriatic area and six non-native species), and two lamprey species are present. Species diversity peaks in the lower river section between Casarsa and Latisana where cold-adapted and warm-adapted species co-occurred in different floodplain water bodies (e.g. Thymallus thymallus, T. tinca and Esox lucius).

12.5.4. Birds and Mammals The otter Lutra lutra is one of Italy’s rarest mammals with a highly restricted range. From 1984 to 1993, the species was recorded in 42 waterbodies, with about 125 individuals fragmented into 5 main groups. The largest group occurred in Southern Italy in Pollino Park (Prigioni 1995). Today, the estimated population size is 229–257 otters (Prigioni et al. 2006). To increase the otter population in northern Italy, a reintroduction project in the Ticino River (Po River basin) was started 10 years ago. Three semi-aquatic non-native mammals were introduced to Italy and can be considered successful invaders: coypu (Myocastor coypus), muskrat (Ondatra zibeticus), and American mink (Mustela vison). They represent a risk to biodiversity and cause damage to

PART | I Rivers of Europe

human structures. The coypu is widespread in northern and central Italy, especially in the Po valley. Damage to crops, riverbanks, and aquatic vegetation has been documented throughout the species range, and negative effects on some birds have been noted. The mink is found in three areas after their escape or release from fur farms, and a population has been present in Latium for more than 10 years. The risk of range expansion of the species has increased in recent years, with implications for other species through predation and competition. The muskrat is one of the most successful invaders, and presently it occupies a wider area in Eurasia than in its native range in North America. In Italy, the species is present in Friuli-Venetia Giulia, where colonization from Slovenia began in the 1990s (Bertolino & Genovesi 2005). Bird diversity in the Adige basin is highest at low and intermediate elevations in the main valleys, along remnant riparian woods and wetlands in particular. Among the most interesting breeding birds are the water rail (Rallus aquaticus), little bittern (Ixobrychus minutus), little grebe (Tachybaptus ruficollis), and black kite (Milvus migrans). Along the vertical cliffs of the Adige valley, the peregrine falcon (Falco peregrinus), blue rock thrush (Monticola solitarius), and bommon rock thrush (Monticola saxatilis) are common. In the Trentino province, most of which is in the Adige basin, about 156 breeding birds were recorded between 1986 and 1995 (Pedrini et al. 2005).

12.6. MANAGEMENT AND CONSERVATION 12.6.1. Economic Importance With the development of urbanization and industrial activities, water has become a primary limiting resource, and at times in short supply. As a consequence, increasing conflicts arise between water availability and multi-purpose demands. The Po basin represents an economically strategic area for Italy, with an Internal Gross Product contributing 40% of national production. Most of the Italian industries, including the largest ones, intense agricultural and livestock activities are located in the Po basin. The tertiary sector is also welldeveloped, providing services to factories, hotels, and private and public transport. In this area, water for irrigation is derived from surface waters (83%) and groundwater (17%). In contrast, 80% of the drinking water comes from groundwater, 15% from springs in the mountains, and 5% from surface waters. According to Italian law 183/89 ‘Norme per il riassetto organizzativo e funzionale della difesa del suolo’, the integrated management of the watershed is assigned to the River Basin Authority (RBA). The RBA is an operational unit including all institutions involved in the conservation and development of basin management. The general goal of the RBA is the conservation of the entire basin for the following purposes: (a) hydrological protection of the water ecosystem, (b) safeguard of water quality, (c) optimization of water use, and (d) regulation of land use. An especially relevant

Chapter | 12 The Italian Rivers

problem related to the management of most Italian rivers is the risk associated with floods and solid transport in rivers, and mudslides and avalanches in mountain areas. Italian legislation controls the use of water resources (laws 183/89, 36/94, 152/06), underlining the importance of the preservation of aquatic life (‘environmental use’) which includes the minimal vital flow (MVF). The MVF usually is defined by the RBA. The protection of each river using appropriate minimal flows, therefore, represents further water demands that conflicts with other water uses. The most critical water situations occur in lowland areas and on hills during low-flow periods, when the cumulative effects of hydropower production, flow diversion for irrigation, drinking water supplies, and industrial use are particularly severe. The quantification of the MVF represents a key element for the integrated management of water resources because it takes into consideration the self-purification capacity of the waterbody and the preservation of aquatic habitats. The only navigation network in Italy was developed along the Po River, mainly in the lower reaches (from the confluence with the Ticino River to the Adriatic Sea, about 400 km), and represents the historic Padanian navigation route. This network includes several inland routes, particularly near Milan, meant to access the Adriatic Sea. Today, commercial navigation is limited to Cremona area. Boat traffic on waterways is low and mainly for oil products, liquid gas, kaolin and clays, seeds, flour, timber, and chemical products. The water network is inadequate for the needs of commercial navigation, primarily due to the narrowing of the canals that connect the Po to maritime ports and shallow water levels occurring during low discharge periods.

12.6.2. Conservation and Restoration In Italy, the establishment and management of protected areas is regulated by a national framework law (394/1991) and regional laws. The framework law defines a classification system of protected areas. The government is responsible for the official designation of protected areas and the Ministry of the Environment and Territorial Protection keeps and updates the official register of protected areas and allows national funding for their management. Currently, about 3 million ha are included in the official register of protected areas as nature reserves, and national and regional parks. The protection, management and development of each protected area are regulated by a specific plan. In the context of the EC, Italy in 1977 prepared a list of proposed sites of community importance for the Nature 2000 network, in accordance with 79/406/EEC and 92/43/EEC. The total surface area of the sites, including 50 wetlands of international relevance recognized in accordance with the Ramsar Conservation, covers over 4.5 million ha. In many cases, these sites overlap with sites found in the Italian official register of protected areas.

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Two-hundred and ten protected areas (natural or seminatural) are present within the Po River basin, and cover a surface of about 517 000 ha, which represent 7% of the total Po basin and 26% of the protected lands in Italy. National and regional parks comprise 88% of the total protected areas in the Po basin; the State Reserves 9.4%, wetlands 0.7%, and the remaining ones (natural monuments, oasis, suburban parks) 1%. A total of 46 of the 210 existing protected areas are associated to rivers. The Adige basin includes part of Stelvio National Park (55 094 ha in Bolzano province and 19 350 ha in Trento province) and several regional parks and protected biotopes. The Adamello-Brenta Natural Park includes Lake Tovel, the well-known Red Lake. The blood-red colour appearing in summer, due to algal blooms, stopped in 1964. Because of the peculiar colour and its beauty in the dolomite landscape, the Ramsar Convention included Lake Tovel among the wetlands of international value in 1980. Most probably, the end of the algal blooms was due to a reduction in nutrients, following a decrease in livestock grazing in the watershed and better sewage treatment around the lake (Borghi et al. 2006). Following the European Directive 92/43/EEC Nature 2000, 75 community interest sites were established in the Adige basin, covering a total area of 224 521 hectares. 23 of these, covering a total area of 170 163 ha, are Special Protection Areas (Adige River Basin Authority 2006). More than 222 000 ha of protected areas are included within the Tiber River basin. The main protected areas are the Sibillini Mountains National Park established in 1993 (32 700 ha), the Roman Coastal Area State Nature Reserve (8700 ha), and Castel Porziano Presidential Reserve (3880 ha). Some fluvial parks deserve particular interest such as the middle-lower reach of the Tiber Fluvial Park (7300 ha) and the Nera Fluvial Park (2100 ha). The Tagliamento River retains the most extensive and connected length of dynamic braided river within the Alps, leading it to be described by M€uller (1995) as the ‘last large natural Alpine river in Europe’. Whilst the River Tagliamento is subject to many human influences, these remain less severe than in most other Alpine river systems, allowing much of its river corridor to remain morphologically intact and highly dynamic. Thus, the Tagliamento provides an important braided reference system (Ward et al. 1989; Tockner et al. 2003). At the same time, the Tagliamento is a highly endangered ecosystem. The regional government is planning 14 km2 large flood retention basins in the most natural section. Ca. 30 million m3 of material, mainly gravel, will be excavated. These retention basins should protect urban and rural areas along the channelized downstream section of the river against floods of up to 100-year events. In addition, a planned highway following the main stem of the river and new industrial areas will severely impact the corridor. The future conservation of the Tagliamento will be a benchmark for the European Water Framework Directive

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12.6.3. EU Water Framework Directive River Basin Management Plans include, according to law 183/89, the risk assessment from natural damage due to floods (DHE). This assessment estimates the probability of occurrence of natural and social damages related to DHE. In order to assess the levels of risk related to floods, riparian corridors that are defined and protected by the basin management plans usually have a prominent role. For example, the riparian ecotones of the Po River cover 7300 km2, representing 10.4% of the river basin and about 1100 municipalities. The actual and potential DHE for each municipality shows that 50% of the municipalities are at high or very high risk, and only 13.3% are at moderate risk. River Basin Authorities have also been working for the past few years on river restoration and this issue is still on the agenda as one of the main working tasks. It is recognized by the ecological community that restoration measures within a river basin must be taken at the watershed scale. Local, regional or global actions can be put in practice in order to mitigate the existing impacts after the river basin has been studied from a holistic point of view. With this approach, the River Basin Authorities coordinate multidisciplinary projects aimed at ‘understanding of the ecological functioning of the river, evaluation of the ecological impacts of human activities on instream and riverine habitats and establishing guidelines and suggestions for river restoration and rehabilitation’. In Italy, several laws such as the EU Water Framework Directive 2000/60/EU are dedicated to a coordinated management of the water resource, taking into consideration environmental issues. Law 1989/183 is the most important one regarding land protection and conservation, together with several more laws connected to it. In fact, this law protects the territory, soil and subsoil, infrastructures, water resources, forests, farmlands, and botanical, faunal, and natural resources. According to law 1989/183 to protect water quality, any use of the water resources that might cause an impact must be checked and coordinated by the authorities. The tool to reach these goals is, according to the law, the hydrographical basin plan that includes all the knowledge needed to plan necessary activities such as information on the territory, local rules and regulations, and technical and operational activities. Once the hydrographical basin plan is approved, it represents a compulsory directive to be followed by the administrations, public agencies, and private users. Despite the similarities that exist between law 183/89 and the Water Framework Directive 2000/60/EU, some problems arise when trying to apply the two laws in a coordinated way. The first problem encompasses the correspondence between the administrative hydrographic basins defined by 183/89 and the hydrographic districts defined by 2000/60/ EU. In the first case, the hydrographic basin corresponds to the area of jurisdiction of the administrative authority. In the second case, the two are separated, at least by definition. From this division arises the second problem regarding how

PART | I Rivers of Europe

planning and management can interact and be integrated in timing and responsibility. In Italy, Basin Authorities are responsible for planning and the Regional Authority for management. The relationship between these two agencies is defined in the board of the Basin Authorities, composed of representatives from State and Regions. In this way, planning and management are interactively defined; responsibility for planning is shared and given to the Regions for management. To promote and preserve a unified course of action for the hydrographic basin, the Po Basin Authority has defined technical tools that follow the directions of the EU Water Framework Directive, which will begin in 2009 with integrated river basin management plans.

12.7. CONCLUSION AND PERSPECTIVE Conflicts can be prevented, resolved or mitigated through a participatory, transparent, open and flexible decision process that involves, from the beginning, all stakeholders. This process should be developed around a ‘win–win’ negotiation approach that tries to identify problems and opportunities looking for wide consent. Although the experience on ‘participation’ is increasing in Italy (e.g. Vara project undertaken by the Basin Authority of the river Magra: www.adbmagra.it), no clear position or tools exist at the policy level, and know-how and cultural background are still lacking. The large problems represented by the degradation of rivers and lakes hinder the compatible integration of natural environments and the landscape with the living areas. The present condition of the Italian river basins and the modifications they are undergoing are due to several factors. Two such factors must be analysed prior to any planning and management decision: 1. The qualitative and quantitative aspects of water resources at the basin scale. The strategic importance of water is shown by the progressive reduction in water resources and the strong decrease in water quality, which started in the 1950s with the development of industry, farming and agriculture that produced a large amount of wastes. The impacts on water quality and quantity are due to: (a) the qualitative degradation of surface waterbodies, (b) the overexploitation and degradation of aquifers, (c) the reduction in the ecological function of natural and artificial drainage networks, and (d) the reduction of natural water flow due to excessive withdrawals, incompatible with the natural availability and the selfpurification capacities of the waterbodies. 2. The security level of the region in respect to floods, and avalanches and landslides in mountains and hill areas. Analysis of these critical factors in specific areas allows managers to define limitations and restrictions in land use, and the possible use of water resources and the river environment for sustainable development. The Po basin is one of the most developed urban, industrial, and agricultural areas of Europe, and the river

Chapter | 12 The Italian Rivers

represents a possible starting point for further economic development. Several environmental impacts are widespread in the basin and their regulation and mitigation are not the responsibility of one regional or local agency. Consequently, it is essential to improve the exchange between the management authorities in order to coordinate legislation, planning, and management regarding soil and water protection, and regional and local safety. On the basis of critical needs and past experiences, the Po Basin Authority developed a strategic plan that contains shared strategies to improve safety, maintain and develop waterbodies, riparian belts and the area of the Padanian basin. The plan is, in fact, aimed to promote the cooperation and coordination of actions, the integration of policies and resources, with a final goal of obtaining a sustainable regional and environmental planning tool. A final purpose of the plan is the production of the framework ‘Patto per il Po’, which will define the objectives and actions shared by the main regional institutions and other interested entities in the Po basin.

Acknowledgements Special thanks are due to Maria Cristina Bruno and the personnel of the Adige Water Authority, in particular the Director Nicola Dell’Acqua and Renato Angheben, Fabio Lazzeri, Manuel Montero Ramirez and Franco Zanuso. We also thank Davide Ubaldi, Giuseppe Dodaro, Laura Leone, Silvia Cavalieri, Bruno Floris, Maria Antonietta Dessena, Francesco Meneguzzo, Francesca Ghepardi, Stefano Fenoglio, Stefano Mazzotti and Giuseppe Sansoni, Danilo Colomela, Ileana Schipani, Cesare Puzzi.

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Margoni, S., and B. Maiolini, 2004. Distribuzione altitudinale di Simulidi in torrenti alpini d’alta quota (Trentino, Italia) Studi Trentini di Scienze Naturali, Acta Biologica 80(2003): 63–64. Mariotti, A., Striglia, M.V., Zeug, N., and Lau, K.N. 2002. The hydrological cycle in the Mediterranean Region and inplications for the water budget of the Mediterranean Sea. Journal of Climate 15: 1674–1690. Massidda, P., and Orru, F. 2002. Bacini idrici della Sardegna: laghi artificiali e traverse a maggiore impatto sulla libera circolazione della fauna ittica. Provincia di Modena (Ed.). Passaggi per pesci, Atti del Seminario Tecnico di Modena: 67–74. Mattoccia, M., Romano, A., and Sbordoni, V. 2005. Mitochondrial DNA sequence analysis of the spectacled salamander, Salamandrina terdigitata (Urodela: Salamandridae), supports the existence of two distinct species. Zootaxa 995: 1–19. Mazzotti, S. (eds). 2007. “Herp-Help” Status e strategie di conservazione degli Anfibi e dei Rettili del Parco Regionale del Delta del Po. Quaderni della Stazione di Ecologia del Museo civico di Storia Naturale, Ferrrara, 17. Mazzotti, S., and Rizzati, E. 2002. Prima segnalazione di Pelobates fuscus insubricus (Cornalia, 1873) nel Delta del Po ferrarese (Amphibia, Anura, Pelobatidae). Annali del Museo civico di Storia naturale, Ferrara, 2001, 4: 137–142. Mazzotti, S., and Caramori, G. 2004. Influence of climatic gradients and colonization history on the present of amphibians in the southern Po River Basin. Herpetozoa 17(3–4): 143–152. Mazzotti, S., Penazzi, R., and Lizzio, L. 2003. Nuove segnalazioni di Pelobates fuscus insubricus Cornalia, 1873 nel sistema dei biotopi costieri del ravennate (Amphibia Anura Pelobatidae). Quaderno di Studi e Notizie di Storia Naturale della Romagna 17: 97–103. M€uller, N. 1995. River dynamics and floodplain vegetation and their alteration due to human impact. Archiv fur Hydrobiologie Supplement 101: 477–512. Negri, P., Chiarabaglio, P.M., Vietto, L., Gravina, E., and Cardini, A. 2004. Challenger of River Restoration in Italy: significant experience trends. In: Geres, D. (ed). River Restoration: Principles, Processes Practices. Nocita, A. 2002. Carta Ittica della provincia di Firenze. Ed It Comm. srl Firenze. Occhipinti-Ambrogi, A. 2002. Current status of aquatic introductions in Italy. In: Leppakoski, E., Gollasch, S., Olenin, S. (eds). Invasive Aquatic Species of Europe. Distribution Impacts and Management, Kluwer Academic Publishers, Dordrecht, Boston, London: 311–324. Pedrini, P., Caldonazzi, M., and Zanghellini, S. 2005. Atlante degli uccelli nidificanti e svernanti in provincia di Trento. Museo tridentino di Scienze Naturali, Trento. Studi Trentini di Scienze Naturali, Acta Biologica 2: 80. Pignatti, S. 1979. I piani di vegetazione in Italia. Giornale Botanico Italiano 113(5–6): 411–428. Pignatti, S. 1982. The origins of the flora of Central Italy. In: Pedrotti F., Guide Itin eraire de l’excursion internationale de Phytosociologie en Italie centrale (2–11 juillet 1982). Camerino, Universita degli Studi. Pignatti, S. 1986. La flora dell’Appennino meridionale: distribuzione attuale ed ipotesi sull’origine. Biogeographia 10: 89–100. Preti, M. 1999. The Holocene transgression and the land-sea interaction south of the Po delta. Giornale di Geologia, Serie 3(61): 143–159. Prigioni, C. 1995. Guidelines for the feasibility study of reintroduction of the otter Lutra Lutra in Italy: The project of the Ticino Valley (NorthWestern Italy). Hystrix It. J. Mamm. (N.S.) 7(12): 255–264. Prigioni, C., Balestrieri, A., Remonti, L., Sgrosso, S., and Priore, G. 2006. How many Otters are there in Italy? Hystrix, the Italian Journal of Mammology 17(1): 29–36.

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Provincia Autonoma di Bolzano-Alto Adige, Assessorato alla tutela della natura, del paesaggio e dell’ambiente. 1995. La qualita biologica dei corsi d’acqua in Alto Adige. Annali del laboratorio biologico provinciale. Ed. Provincia Autonoma Bolzano. Provincia di Verona. 1997. Qualit a delle acque superficiali. Monitoraggio dei corsi d’acqua principali della provincia di Verona. Rapetti, F., and Vittoriani, S. 1994. I caratteri del clima. In: Mazzanti, R. (ed). La pianura di Pisa e i rilievi contermini. Mem. Soc. Geogr. It., Vol. L: 103–132. Renai, B., Bertocchi, S., Brusconi, S., Gherardi, F., Grandjean, F., Lebboroni, M., Parinet, B., Souty Grosset, C., and Trouilhe, M.C. 2006. Ecological characterisation of streams in Tuscany (Italy) for the management of the threatened crayfish Austropotamobius Pallipes Complex. Bulletin Francais de la Peche et de la Pisciculture 380– 381: 1095–1113. Ruffo, S., and Stoch, F. 2006. Checklist and distribotion of the Italian fauna Memorie del Museo Civico di Storia Naturale di Verona – 2. Serie. Sezione Scienze della Vita 17 with CD-ROM. Ruffo S., and Vigna Taglianti, A. 2002. Generalita sulla fauna italiana, in: La fauna in Italia (a cura Minelli A., C. Chemini, R. Argano, Ruffo S.), Touring Editore, Milano e Ministero dell’Ambiente e della Tutela del Territorio, Roma: 24–28. Rust, C. 1998. Die o€kologische Bedeutung von Inseln und Schotterb€ anken im Tagliamento (Friaul, Italien) am Beispiel der Laufk€ aferz€ anose (Carabidae, Insecta). Diplomarbeit, ETH-Z€urich. Sala, L., Gianaroli, M., and Tongiorgi, P. 2004. Evoluzione storica e recente dell’ittiofauna modenese. Biologia Ambientale 18: 265–270. Sindaco, R., Doria, G., Razzetti, G., and Bernini, F. 2006. Atlante degli Anfibi e dei Rettili d’Italia/ Atlas of Italian Amphibians and Reptiles. Societa Herpetologica Italica, Edizioni Polistampa, Firenze. Stebbins, R.C., and Cohen, N.W. 1995. A Natural History of Amphibians. Princeton University Press, New Jersey. Surian, N., and Rinaldi, M. 2003. Morphological response to river engineering and management in alluvial channels in Italy. Geomorphology 50: 307–326. Tancioni, L., Scardi, M., and Cataudella, S. 2006. Riverine fish assemblage in temperate rivers. In: Ziglio, G., Siligardi, M., Flaim, G. (eds). Biological Monitoring of Rivers, John Wiley and Sons, Ltd. Takhtajan, A. 1986. Floristic Regions of the World. University of California Press 522 pp. Tockner, K., Klaus, I., Baumgartner, C., and Ward, J.V. 2006. Amphibian diversity and nestedness in a dynamic floodplain ecosystem (Tagliamento, NE Italy). Hydrobiologia 565: 121–133. Tockner, K., Ward, J.V., Arscott, D.B., Edwards, P.J., Kollmann, J., Gurnell, A.M., Petts, G.E., and Maiolini, B. 2003. The Tagliamento River: a

model ecosystem of European importance. Aquatic Sciences 65: 239–253. Turri, E., and Ruffo, S. 1992. Adige-il fiume, gli uomini, la storia. Cierre Edizioni, Verona. UNEP/MAP 2003. 13 Conferenza delle Parti Contraenti la Convenzione di Barcellona per la Protezione del Mare Mediterraneo. Catania 11–14 Novembre 2003. Ward, J.V., Tockner, K., Edwards, P.J., Kollmann, J., Bretschko, G., Gurnell, A.M., Petts, P.E., and Rossaro, B. 1999. A reference system for the Alps: the “Fiume Tagliamento”. Regulated Rivers 15: 63–75. Zerunian, S. 1992. La perdita di diversita nelle comunita ittiche delle acque dolci. In: Ambiente Italia 1992. Lega per l’ambiente/Vallecchi ed., Firenze: 156–169. Zerunian, S. 2002. Condannati all’estinzione? Ed agricole Bologna 220 pp. Zerunian, S., and Gandolfi, G., 1999. L’ittiofauna indigena nelle acque interne italiane: minacce, gestione, conservazione. Atti. Sem I Biologi e L’ambiente oltre il 2000/C ISBA, Reggio Emilia: 95– 110. Zerunian, S., and Taddei, A.R. 1996. Pesci delle acque interne italiane: status attuale e problematiche di conservazione. WWF Italia, Roma,18 pp.

FURTHER READING Giusti, F., and Oppi, E. 1972. Dreissena polymorpha (Pallas) nuovamente in Italia. Memorie del Museo Civico di Storia Naturale di Verona 20: 45–49. Ravizza Dematteis, E., and Ravizza, C. 1988. Les Plecopteres de la vallee superieure du Po (Alpes Cotiennes). Notes faunistiques et ecologiques. Annls Limnol 24: 243–260. Stoch, F., Paradisi, S., and Dancevich, M.B. 1992. Carta Ittica del FriuliVenezia Giulia, ETP, Udine. Ubaldi, D. 2003. La vegetazione boschiva d’Italia – Manuale di fitosociologia forestale. Clueb, Bologna. Vigna Taglianti A., Audisio, P.A., Belfiore, C., Biondi, M., Bologna, M. A., Carpaneto, G.M., De Biase, A., De Felici, S., Piattella, E., Racheli, T., Zapparoli, M., and Zoia, S. 1993. Riflessioni di gruppo sui corotipi fondamentali della fauna W-paleartica ed in particolare italiana. Biogeographia, Lav. Soc. Ital. Biogeogr., (n.s.) 16(1992): 159–179. Vigna Taglianti, A., Audisio, P.A., Biondi, M., Bologna, M.A., Carpaneto, G.M., De Biase, A., Fattorini, S., Piattella, E., Sindaco, R., Venchi, A., and Zapparoli, M. 1999. A proposal for a chorotype classifi cation of the Near East fauna, in the framework of the Western Palearctic region. Biogeographia, Lav. Soc. Ital. Biogeogr., (n.s.) 20: 31–59.

Chapter 13

Western Steppic Rivers A.N. Sukhodolov

N.S. Loboda

V.M. Katolikov

Department of Ecohydrology, LeibnizInstitute of Freshwater Ecology and Inland Fisheries, M€ uggelseedamm 310, D-12587 Berlin, Germany

Department of Hydrology;Odesa State Environmental University, Lvovskaya street 15, 65016 Odesa, Ukraine

Department of Channel Processes, State Hydrological Institute, 23 Second Line V.O., 199053 St. Petersburg, Russia

N.A. Arnaut

V.V. Bekh

M.A. Usatii

Laboratory of Hydrogeology and Engineering Geology, Institute of Geophysics and Seismology, Moldavian Academy of Sciences, Academiei Street 3, 2028 Kishinev, Republic of Moldova

Laboratory of Fish Genetics and Selection, Institute of Fisheries, Ukrainian Academy of Agrarian Science, Obukhivska Street 135, 03164 Kyiv, Ukraine

Laboratory of Ichthyology, Institute of Zoology, Academiei Street 1, 2028 Kishinev, Republic of Moldova

L.A. Kudersky

B.G. Skakalsky

Department of Hydrobiology, Institute of Limnology, Russian Academy of Sciences, Sevastyanov Street 9, 196105 St. Petersburg, Russia

Department of Environmental Chemistry, State Hydrometeorological Institute of Russia, Malookhtinsky Prospect 98, 195196 St. Petersburg, Russia

13.1. 13.2.

13.3.

13.4.

13.5.

13.6.

13.7.

Introduction Biogeographic Setting 13.2.1. General Aspects 13.2.2. Paleogeography and Modern Glaciation Physiography, Climate, and Land Use 13.3.1. Landforms and Geology 13.3.2. Climate 13.3.3. Land-Use Patterns Geomorphology, Hydrology, and Biochemistry 13.4.1. Geomorphology, Channel Form, Floodplains 13.4.2. Hydrology and Temperature 13.4.3. Biogeochemistry Aquatic and Riparian Biodiversity 13.5.1. Phytoplankton, Zooplankton, and Zoobenthos 13.5.2. Fish Fauna, Amphibians and Mammals Management and Conservation 13.6.1. Economic Importance 13.6.2. Conservation and Restoration 13.6.3. Catchment Master Plans Conclusions and Perspectives Acknowledgements References

Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

13.1. INTRODUCTION Five large rivers, Dniester, Southern Bug, Dnieper, Don and Kuban, represent the major fluvial systems of the Western Steppe. Their catchments occupy a vast area in southeast Europe, extending eastward from the Carpathians (22 E) towards the Volga (46 E) and northward from the Crimea peninsula and Caucasus Mountains (42 N) to the Valday Hills (52 N) (Figure 13.1). The significance of these rivers is highlighted by the fact that the Dnieper is the third and the Don is the fourth largest rivers of Europe. Tributaries of these rivers, the Donets, Desna, Prypiat, Byrezina, Sozh, Seym, Belaya and Laba, are also of considerable length and drain relatively large catchments. The territory of the Western Steppe includes many Russian provinces in the north, east and south, and Belarus, Ukraine and Moldova. Although the rivers of Western Steppe originate in different biogeographic regions and hence principally differ by source and hydrologic flow regime, their lower reaches are in the Steppic region and characterized by similar physiography, climate, economy and history (Photos 13.1 and 13.2). Historically, up to the 14th century, the Western Steppe was inhabited by many nomadic tribes that crossed during their migrations from east to west. In 500 BC it was inhabited by Scythians that were replaced later by Venedians, Sarmatians and Alanians between 100 and 300 AD. Between 400 and 600 AD, the steppe was colonized by Slavic tribes moving 497

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PART | I Rivers of Europe

FIGURE 13.1 Digital elevation model (upper panel) and drainage network (lower panel) of the Western Steppic rivers.

northeast from western Europe and the Balkans (Stratanovski 2004). From the 6th to 13th century, the territory was inhabited again by nomads of Asian origin: Cumans (Polovtsy), Khozars, and Mongolian hordes of Genghis Khan’s descendants (Gumilev 1989; Kluchevsky 2000). For instance, Mongolians and Tatars moved through the steppe from 1237 to 1241 in preparation to invade western Europe. Northern areas of the Dnieper and Don were initially inhabited by tribes of

Finnish hunters driven far north by Slavs in the 5th–6th centuries. Slavs settled in the upper Dnieper and Don, cutting forests and using the land for agriculture. They founded the first state now called Ancient Rus (Gumilev 1989) with the capital Kiev. During the 14th–16th centuries, following the defeat of the nomads by the Russians, a large area of the steppe was colonized by ancestors of present day Ukrainians. Expansion of Russians to the Kuban region began in the

Chapter | 13 Western Steppic Rivers

499

PHOTO 13.1 Dnieper River in Kiev (Photo: I. Sirenko, National Ecological Center of Ukraine).

PHOTO 13.2 Don River near Khutor Kalininsky, Rostov Region (Photo: Dr. Yu. A. Rebriev, South Scientific Center of RAS).

mid-18th century and was accelerated by the resettlement of Zaporizhzhya Cossacks after the Catherine II decree. Before the 15th century, the vast grasslands of the steppe were used traditionally by nomads as pastures for domestic animals (mainly horses and camels). Since the 15th century, large areas of the fertile steppe have been converted to agricultural lands (Kluchevsky 2000). Besides the effects of agriculture, rivers of the steppe zone also were impacted by the construction of water mills and impoundments. Intensive industrialization began in the early 20th century with severe direct and indirect effects on rivers and their catchments. During this period, a cascade of large reservoirs used for generating electricity began regulating the hydrologic regime of the Dnieper, Don, and Dniester, and 70–80% of the land was converted to croplands that deforested large areas in the north. Other natural resources such as table salt were mined, and discoveries of rich coal deposits promoted mining in the industrial basin called the Donbas. Industrialization also caused extensive use of steppe water resources for melioration, irrigation, navigation, water supply and

sewage treatment. Unfortunately, the Dnieper watershed and the watershed of its tributary Prypiat became world famous for their industrial and environmental catastrophe in 1986 of the nuclear power plant near Chernobyl. After the collapse of the Soviet Union in 1991, industry and agriculture of the region suffered significant declines, causing dramatic decreases in the economy and demography. Sociologists forecast significant declines (up to 40%) of the population in the next 50 years (Borysova et al. 2005). Six rivers are discussed in this chapter, including the primary rivers Dniester, Southern Bug, Dnieper, Don and Kuban. We also describe in detail the Donets, the largest tributary of the Don, because the Donets experiences the greatest (in the region) pressure from industrialization. These rivers represent the diverse physiographic and biological characteristics of the steppe region. Abbreviated information is also provided for other major tributaries (Photo 13.3): the Dniester tributary Reut, and Dnieper tributaries Teterev, Prypiat, Desna and Psel. General characteristics of these river catchments are presented in Table 13.1.

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PART | I Rivers of Europe

PHOTO 13.3 Kurdgips River, a tributary of the Kuban (Photo: V. Katolikov).

TABLE 13.1 General characterization of the Western Steppic rivers

Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25%) ecological regions Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparse vegetation Wetland Freshwater bodies

Don (excl. Donets)

Donets

Kuban

Dnieper

Southern Bug

Dniester

144 328 053 21.7 47.9 7.2 2 28; 55

151 99 442 5.6 51.7 7.8 2 55

594 62 851 11.4 85.9 9.5 3 25; 55

158 512 293 53 58.5 7.1 5 22; 28

188 63 922 3.4 55.4 8.2 3 22; 28; 55

284 73 230 10.0 60.7 8.4 4 22

1.9 77.0 7.0 11.9 0.5 0.0 0.0 1.7

3.9 81.7 10.5 3.3 0.0 0.0 0.2 0.4

2.5 56.7 1.2 20.0 17.2 0.1 0.1 2.2

1.8 40.9 22.2 19.3 0.0 0.0 14.1 1.7

2.7 73.5 18.2 5.3 0.0 0.0 0.2 0.1

1.8 66.9 5.2 23.7 0.0 0.0 1.3 1.1

Protected area (% of catchment)

3.1

3.3

10.0

3.2

0.6

6.9

Water stress (1–3) 1995 2070

2.9 3.0

2.9 3.0

1.9 2.1

2.0 3.0

1.1 3.0

1.9 3.0

Fragmentation (1–3) Number of large dams (>15 m) Native fish species Non-native fish species Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person)

3 2 64 9 3 33 1659

For data sources and detailed explanations see Chapter 1.

3 3 31 13 6 87 1010

3 1 61 13 2 62 1062

3 6 40 13 18 64 1388

2 1 40 12 4 60 737

3 2 50 7 5 101 582

501

Chapter | 13 Western Steppic Rivers

13.2. BIOGEOGRAPHIC SETTING 13.2.1. General Aspects River catchments of the Western Steppe encompass four biogeographic regions. Although the sources of these rivers are in different biogeographic regions, their lower reaches are all situated in the Steppic region. The upper Dniester and Kuban lay in the Alpine region (Carpathians and Caucasus), whereas the upper Dnieper and its tributaries are in the Boreal region. The upper Southern Bug, Don and Donets, and the middle Dnieper, Dniester, Don and Kuban, are in the Continental region. Seven ecoregions make up the steppic rivers territory, including Carphatian montane forests, Caucasus mixed forests, Central European mixed forests, Crimean Submediterranean forest complex, East European forest steppe, Pontic steppe, Sarmatic mixed forests. The East European forest steppe and Pontic steppe comprise about 80% of the territory and represent the western limit of the great Eurasian steppe that stretches from the Black Sea to Central Asia.

13.2.2. Paleogeography and Modern Glaciation The East European Platform is a crystal block forming the foundation of the Western Steppe. During the Cambrian and Ordovician, its crystalline blocks were covered by shallow seas and subjected to marine sedimentation processes that continued through the Paleozoic and Mesozoic. Presently, the Precambrian basement of the East European Platform is covered by a 1–3 km thick layer of deposits beneath a relatively thin Phanerozoic cover (Salminen et al. 2005). In the late Cretaceous (65 Ma) began a series of glaciations resulting in a reduction in ocean levels, and the appearance of plains and fluvial systems. The Caucasus Mountains bordering the Western Steppe in the southeast were formed 24– 29 Ma because of the collision between Arabian and Eurasian tectonic plates. Glaciation during the middle Pleistocene (0.8 Ma) molded fluvial systems into their contemporary patterns that appeared after the Don glaciation (Alekseev 1996). Catchments of the Dnieper and Don were formed during the last glacial maximum called Late Weichselian (Valday) glaciation (25–15 ka) when Valday end-moraines formed their northern boundaries. Valleys of contemporary rivers represent paleochannels of the late Pleistocene (14–12 ka). Paleolandscape and paleohydrographical reconstruction suggest that these paleochannels were formed by extremely high spring flows, flows an order of magnitude greater than observed today because of permafrost (Sidorchuk et al. 2001). The retreat of ice cover and subsequent reduction of melt-water and permafrost degradation caused a decrease in annual runoff. In the western steppe and forest steppe zones, contemporary annual runoff constitutes only about 10% of the periglacial annual runoff. As a result, large periglacial channels were abandoned and trans-

FIGURE 13.2 The width of the Dniester River floodplain from the source to its mouth.

formed into floodplain lakes and bogs. Indeed, the valleys of Western Steppe rivers can be 10–15 times wider than the widths of meandering belts on modern rivers (Figure 13.2). Periglacial forest steppe in the East European (Russian) Plain between 56 and 59 N consisted of meadow steppe with areas of birch–pine, spruce forest and tundra–steppe communities. Forb periglacial steppes were found south of 51 N. The predominance of steppe and forest-steppe was favourable for large mammals such as mammoth, rhinoceros, bison, and deer (Markova & Simakova 1998). Exploration of the territory by humans for hunting and fishing began in the Mesolithic Age (11–10 ka). Modern glaciation is present on a substantial part of the Kuban’s catchment and significantly influences the climate, hydrology, and the river itself (Lure et al. 2005). The total area of glaciers and firns, using recent estimates, is 203.9 km2 with a total ice volume of 7.5 km3. The number of glaciers is 467. The largest glaciers are in the catchment of the tributary Smaller Zelenchuk. These glaciers are 3.2 to 7.4 km long with areas of 1.9–7.1 km2. Maximal thickness of the ice cover ranges from 50 to 250 m, and an absolute maximum 270 m has been reported for the Marukhs Glacier. The gradients of the glaciers are substantial and vary from 30 to 50 with lesser (5 –12 ) slopes in the valleys. About 12.8 km2 of the total glacier area is covered by moraine substrates. The thickness of moraine cover is high and can be 80–100 cm over the ice at some places. In general, modern glaciation can be characterized as degrading because of systematic reductions in total area and the volume of ice and firns that began, by some estimates, thousands of years ago (Lure et al. 2005).

13.3. PHYSIOGRAPHY, CLIMATE, AND LAND USE 13.3.1. Landforms and Geology Catchments of the Western Steppe occupy a substantial part of the southwest East European (Russian) Plain and make up various landforms with diverse geologies. Morphologically,

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the territory consists of vast flatlands demarcated by the Carpathian Mountains to the west, Valday Hills to the north, Volga Uplands to the east, and Caucasus Mountains to the southeast. The Volyn–Podolsk plateau separates the catchments of the Dniester and Southern Bug, bounded to the northeast by the Dnieper Upland. Catchments of the Dniester and Don are divided by the Central Russian Uplands. The Black Sea and Azov Sea lowlands represent characteristic landforms of the steppe to the south (Alymov et al. 1978). The Dniester and many of its tributaries originate in the middle Beskyd region of the Carpathians where the relief is represented by a series of long parallel gorges with forest-covered slopes (Anuchin 1956). Eastward from the middle Beskyd, mountain gorges are dislocated as a zigzag pattern and are called Gorgany. Here they are intersected by the southern tributaries of the Dniester: the rivers Bystritsa, Strvyazh, Stryi and Lomnitsa. Altitudes of most mountains do not exceed 1000 m asl, although a few rise beyond that elevation (Magura 1363 m, Bukuska 1409 m, Lopushna 1836 m, Syvulya 1818 m, Vysokaya 1808 m). The mountains were formed during the Alpine orogeny in the Tertiary. Their formation was caused by volcanic eruptions and their contemporary relief resulted from two peneplanations that produced several relatively flat surfaces (Glushko & Kruglov 1971). Soils in the mountains are acidic, comprising low fertile brown and light-brown forest soils on mountain slopes and meadow soils in valleys. Northeast from the Carpathians, the Dniester flows through the Volyn–Podolsk plateau. The northwest of the plateau comprises a hilly upland with altitudes of 360– 470 m asl intersected by deep valleys (Kaganer et al. 1969). The area of the Volyn–Podolsk plateau north of the Dniester is called the Transnistrian plateau. Altitudes of the plateau gently decrease from 340–360 to 180–200 m asl, meeting the Bessarabian uplands to the south. The Khotyn uplands, at altitudes up to 460 m asl, run south of the Dniester and separate the Beletskaya steppe from the Reut catchment to the east. Further south of the Beletskaya steppe is the forested plateau called Kodru (reaching altitudes of 428 m asl). These uplands occupy in total >75% of the Dniester catchment (Anuchin 1956). The southern area of the catchment is on the Black Sea coastal basin; a lowland gently sloping towards the Black Sea. Soils on the Volyn– Podolsk plateau are loess covered by humus and grey forest podzols, whereas soils of the steppe part of the catchment are mainly loam sand and clays. Landforms of the Valday Hills in the north are characterized by typical glacial moraines that extend into preglacial uplands (Protasiev et al. 1973). The relief is represented by hills up to 340 m asl separated by river valleys and moraine lakes (Valday Lake, Seliger Lake). Because of sharply shaped landforms and significance of the hills as a boundary of river catchments, they were initially considered a low mountain system. Soils of the Valday Hills are carbonate limestones with coarse fractions of moraine deposits of

PART | I Rivers of Europe

boulders and sands covered by a thin layer of grey forest podzols (Protasiev et al. 1973). The Kuban and many of its tributaries originate in the Caucasus Mountains located in the middle of the Eurasian Plate. The Caucasus Mountains are composed of two separate mountain systems: the Great Caucasus Range (tectonic origin) and Lesser Caucasus Mountains (volcanic origin). The Great Caucasus Range stretches 1100 km east–southeast from the northeastern shore of the Black Sea towards the Caspian Sea and represents a geologically recent formation characterized by peaks of prominent altitudes: Elbrus (5642 m), Dykh–Tau (5205 m), and Koshtan–Tau (5152 m). Areas higher than 2800– 3000 m asl are subjected to permafrost, and the glacier line starts at 2500–3500 m asl. A zone of alpine meadows stretches along altitudes of 2000 m asl. The northern slopes of the Great Caucasus Range are covered by oak, hornbeam and maple at lower altitudes, and by birch and pine forests at higher elevations. The Central Russian Upland stretches about 1000 km southeast from the Valday Hills to the Donets River where it is met by Donetsk gorge. Altitudes of the upland are relatively low, ranging within 200–300 m asl. Soils of the Central Russian Upland consist of erosional loess and loam sands, and the relief is dominated by numerous gullies 50– 100 m deep. The Dnieper Upland lies between the middle reaches of the Southern Bug and Dnieper; an upland characteristically similar to the Central Russian Upland with elevations averaging 250 m asl. The upland is intersected by gullies and valleys of tributaries of the Dnieper and Southern Bug (Alymov et al. 1978). On the eastern side of the Western Steppe, the Don catchment is separated from the Volga catchment by the Volga Upland. Altitudes of the Volga Upland reach 375 m asl near Zhiguli, gently increasing from the Don valley and then steeply dropping towards the Volga. Lowlands occupy the largest portion of the Western Steppe, with the Ukrainian and Belorussian Polesse lowlands in the northwest. Belorussian Polesse stretches about 500 km along the Prypiat River at altitudes of 130– 150 m asl. The relief of the Polesse is mainly flat with some singular moraines and parabolic dunes. Numerous local depressions filled with water form bogs and swamps. Soils of the Polesse are mainly turf and peats, and forests are widespread, covering >30% of the area. The lower Prypiat and Teterev rivers flow through the Ukrainian Polesse (Zhitomir Polesse). Crusts underlying the area approach the surface and form cliffs and small gorges that create torrents and rapids on tributaries of the Prypiat and Teterev (Protasiev et al. 1973; Alymov et al. 1978). In the south extend a chain of uplands including the Podillia (Photo 13.4), Dnieper and Zaporozhian Ridges, including the Azov and Donets Ridges to the north. The Black Sea Lowland stretches from the Danube River mouth in the west to the Don Lowland in the east. The width of the Black Sea Lowland varies from 50 km in the east and west to 180 km in the centre. The Black Sea Lowland lies entirely within the

Chapter | 13 Western Steppic Rivers

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PHOTO 13.4 Canyon and Island Gard on the Southern Bug River – the frontier of Zaporozh Cossacks and recent white water paradise (Photo: I. Sirenko, National Ecological Center of Ukraine).

boundaries of the historical–geographical area known as southern Ukraine, making up almost half of its territory. The Black Sea Lowland includes an area of the Black Sea Depression consisting of thick, almost horizontal layers of sediment, mostly Paleocene and Neocene sea deposits represented by various clays, sands, limestones, sandy clays, and sandy limestones covered with continental deposits of the Anthropogene period (reddish-brown clays, loess, and loess-loams). Presently, the Black Sea Lowland is an accumulative, weakly divided plain, gradually sloping towards the Black Sea and the Sea of Azov. Altitudes of the lowland decrease from 160 m asl in the north to 10–15 m asl in the south. The lowland is dissected by a fairly thin network of river valleys (25–80 m deep) of the Dniester, Southern Bug, Inhul, Inhulets, Dnieper and others (Figure 13.1). Valley slopes are incised by gullies and ravines. The Oleshia Sands (a waterless, sandy plain that was once the Dnieper delta) is a distinctive landscape on the alluvial plain on the left bank of the lower Dnieper. The area around Syvash Lake is also distinctive, being formed as the sea advanced onto dry land. The most variable landscape is on the seacoast, resulting from the interaction of various forces along the sea–land interface.

13.3.2. Climate Geography of the Western Steppe influences the interactions between major air masses governing its climate, including cold and relatively dry Arctic air, moist air from the Atlantic, dry warm (in summer) air from Kazakhstan, and tropical air from the Mediterranean Sea. The convergence and collisions of these air masses produce highly variable weather. Moreover, the eastward extension of the territory and complex orography in the west and southeast add significant spatial variability to the climate (Babichenko 1984).

Winter in the Western Steppe begins with the intrusion of air masses from the Arctic, dominated by the western part of the Siberian anticyclone that produces low temperatures and cold dry easterly winds. Periods of cold weather are periodically interrupted by warm, moist air masses from the Atlantic and Mediterranean Seas that cause precipitation. The Siberian anticyclone influence is greatest in the Don catchment, whereas the upper Carpathian area of the Dniester is affected by air from the Atlantic (Protasiev et al. 1973; Babichenko 1984). Winter begins by early November in the north and by mid December in the southwest. A period of stable air temperatures <0 C last up to 110 days in the northern Don catchment but only for 30 days in the southwest. Mean temperatures in January decrease from southwest to northeast from 2 C to 12 C, and with a minimum of 44 C. Snow cover usually appears in early November (averaging 30 cm deep) in the north and late December (averaging 5–10 cm) in the southwest. Spring begins in mid February or March in the north (Kaganer et al. 1967; Kaganer et al. 1969; Protasiev et al. 1973). During spring, circulation of air masses commonly increases along a meridian convection from southwest to northeast. Development of an Azorean cyclone forces warm moist air masses from the Mediterranean Sea to the northeast, increasing in temperature as they flow over the territory. Spring has the most stable air temperatures, ranging between 4 and 15 C for 40–50 days in the north and 60–70 days in the southwest. In summer, local-scale atmospheric processes dominate. High solar radiation causes strong vertical temperature gradients and decreases the convection produced by the Azorean cyclone. Summer is hot and dry, beginning in mid-May for 140 days in the south and late May for 100 days in the northeast. Mean temperature in July reaches 20 C in the

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northeast and 25–30 C in the south, and with a maximum of 45 C. Autumn is characterized by the gradual replacement of the winter atmospheric circulation. Northern and northeastern anticyclones intrude cold air from the Arctic and Siberia that often causes temperatures <0 C. The most significant decreases in air temperature occur in late September or early October. Autumn typically lasts for 60–70 days with gradual decreases in mean air temperature from 15 to 0 C. Mean annual precipitation is maximal in the west (Carpathians) and southeast (Northern Caucasus) and cumulates about 100 cm at altitudes >800 m asl (Carpathians) and 60– 180 cm (Northern Caucasus). Precipitation varies 50 cm from west to east and from north to south, being only 22 cm on the Black Sea Lowland. Precipitation maximum occurs in summer and the minimum is usually observed during late winter early spring. The longest duration of precipitation occurs in late autumn and winter. Heavy rains and thunderstorms are frequent in late spring and early summer, at times causing catastrophic flooding on the Dniester, Southern Bug and tributaries (Anuchin 1956; Protasiev et al. 1973; Babichenko 1984). Rain caused floods are frequent on the Kuban and its tributaries. Temperature and other meteorological variables have been recorded for the Western Steppe since the beginning of the 19th century (Kiev meteorological station). Air temperatures and precipitation in Kiev, north of the steppe, have slightly increased during the past 150 years (Figure 13.3). In

FIGURE 13.3 Long-term records of annual mean temperature.

PART | I Rivers of Europe

contrast, temperatures have decreased and precipitation slightly increased in this period in the southern steppe, around Odessa. A possible explanation for the increase in temperatures in Kiev, especially evident after 1930, might be a local warming effect from the massive reservoir network on the Dnieper and concomitant industrial development.

13.3.3. Land Use Patterns The Western Steppe was relatively untouched by humans until the 17th century. Earlier, the territory was inhabited by nomadic tribes that used the land as pasture for domestic cattle and for hunting. The first agricultural settlements were developed by the Romans in the western part of the steppe along river valleys of the Dniester. The northern-forested area along the Dnieper was used for timber and agriculture. Land use consisted of a semi-nomadic agriculture of ancient Slavs that burned the forests as fertilizer for crops of millet oats, barley, and wheat, often moving from place to place (Kluchevsky 2000). This land use process eliminated the pristine deciduous and coniferous forests over a large area that stretched as far south as Kiev (Gumilev 1989). Following the appearance and growth of cities, development of the states, and establishment of military control against nomadic invasions, exploration of the steppe occurred rapidly. The union of Ukraine to the Russian Empire, and specific colonization projects by Ekaterina II at the end of 18th century, attracted colonists from Germany that settled and cultivated lands along the Southern Bug and on the southeast area of the steppe (north of Crimea). Zaporizhzhya Cossacks were transferred to the Northern Caucasus in 1792 to colonize the Kuban catchment and resulted in agricultural military settlements that began exploration of pristine steppic lands. By the end of the 19th century, 65–70% of the Western Steppe was used for agriculture (mainly rye, corn, potato and flax). Government organizations began to express concern about preserving the natural steppe at this time, and a national reserve, Askania Nova (33 307 ha), was established in 1898 in the Kherson region (Krutyporokh & Treus 1967). Since the times of Ancient Rus, the southern steppe region has been mined for the rich deposits of table salt by Ukranian salt traders. Intensive industrialization in the mid20th century brought new significant land use changes to the Western Steppe. The Donets and western Don catchments were mined for coal, while the southern Dnieper catchment housed a massive manufacturing industry (Golobutsky 1970). Energy demands of the growing industry resulted in the construction of large hydropower stations on the Dnieper below a vast cascade of reservoirs. The reservoirs flooded 6900 km2 of fertile land, withdrawing it from agriculture (Vishnevsky 2000; Vishnevsky & Kosovets 2003). Subsequently, industrial development and accelerated urbanization have caused even higher water demands, promoting irrigational and water transfers from other watersheds via the Volga–Don and North-Crimea canal systems.

Chapter | 13 Western Steppic Rivers

Presently, the agricultural system of land use is based heavily on the collective farming scheme inherited in the post-soviet period. Although some private farming has developed during the last decade, a significant reduction in agriculture has occurred. Increases in costs for fertilizers and chemicals (pesticides, herbicides) traditionally used during the soviet period have caused a significant reduction in their use today. However, other factors such as industrial growth, degradation of canals and irrigation systems, and inefficient sewage treatment have become more pronounced and are primarily responsible for ground and surface water pollution.

13.4. GEOMORPHOLOGY, HYDROLOGY, AND BIOCHEMISTRY 13.4.1. Geomorphology, Channel Form, Floodplains The Dniester originates from springs (at 760 m asl) in the Carpathians and flows southeast 1352 km towards the Dniester Liman estuary on the Black Sea. It drains an area of 73 230 km2. The river has a mean slope of 1.8%, ranging from a maximum of 39.0% and minimum of 0.01%. Orographical and climatic characteristics subdivide the catchment into a Carpathian mountain area, the Sub-carpathian uplands, the Volyn–Podolsk plateau, and the southeast steppe (Kaganer et al. 1969). A distinctive feature of the Dniester catchment is the absence of large tributaries and, as such, the catchment of the river is stretched along the main river channel. The fluvial network of the Dniester comprises 16 890 rivers with a cumulative length of 42 760 km. Small rivers <10 km long predominate (16 294 rivers). There are 449 rivers with lengths ranging from 10 to 25 km, 86 rivers with lengths <50 km, 45 ranging from 50 to 100 km in length, and 15 rivers ranging from 100 to 300 km in length. River density is highest in the Carpathians at 1–1.5 km/km2, being 0.75 km/ km2 on the Volyn–Podolsk plateau and only 0.2 km/km2 in the steppe. There are no large lakes in the Dniester catchment, and the numerous small lakes are mainly on the floodplain of the lower river represented by oxbow lakes connected to the river by narrow canals. Ponds and impoundments are common along small tributaries of the Dniester. The total area of lakes, ponds, and reservoirs in the catchment is 450 km2 or 1% of its area (Sokolov 1952; Kaganer et al. 1969). Based on the composition of the river valley, floodplain characteristics, and hydraulic and morphometric characteristics of the river channel, the Dniester can be subdivided into three sections. The upper section begins at the river source and flows to the village of Nizhnee, the middle section runs between Nizhnee and the city of Dubossary, and the lower section flows from Dubossary to the Dniester Liman estuary. From its source, the river flows through a narrow

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incised (80–100 m) valley with side-slopes covered with coniferous forests. The river source is a spring 0.5–1 m wide and 1–5 cm deep. However, as it flows downstream it receives water from numerous springs and quickly becomes a swift mountain stream with rapids and waterfalls. Downstream of the city Stary Sambor, the river floodplain widens to 13 km. The river flows through swamps and meadows of the San–Dniester lowlands, braiding and creating numerous side-arms separated by relatively large islands. The width of the river near Stary Sambor is 10–20 m, and further downstream it widens to 50–100 m, being characterized by sequences of riffles and pools with pebble/cobble substrata. River depth varies from 0.5–1.5 m in riffles to 2–5 m in pools. Current velocity reaches 2–2.5 m/s in riffles and 0.3–0.7 m/s in pools. Riverbanks are high (1–5 m) and steep. Downstream of Nizhnee, the river valley narrows to 0.4– 1.5 km, although there are some places such as near the village Bakot where the valley widens up to 6 km because of tributary confluences. Valley slopes are steep and composed of limestone, sandstones, and clays. Downstream of the Mogilev–Podolsk city, the river valley widens to 1.5– 3 km and further downstream it becomes less steep and terraced. The floodplain is on average 50–100 m wide, vegetated with grass and shrubs and used for farming. The floodplain regularly floods about 1–5 m during spring and high rains. The middle section of the river is more sinuous relative to the upper section. The length of some meander loops reaches 12–15 km with a radius of curvature of 2– 5 km. The width of the river upstream of the confluence with the Zbruch River is about 100 m, downstream to the village of Podoima the channel widens to 150–200 m, and further downstream the width increases up to 300–500 m as it enters the backwaters of Dubossary reservoir. Riverbed morphology consists of sequences of riffles and pools spaced at intervals of 5–10 km. Riffles are 0.5–3 km long and 150–250 m wide with slopes ranging from 0.7 to 1.2%. River depth varies from 0.5–1.5 m in riffles to 2.5–5 m in pools. Velocity of the flow ranges from 0.3 to 2 m/s, and the riverbed is composed of pebbles and sands with silt near the banks. Riverbanks are high (2–8 m) and steep, armoured with riprap or protected by levees at some places (Kaganer et al. 1969). Downstream of Dubossary, the river valley broadens from 4 to 6 km near Tighina (Bendery) up to 16 km at the Turunchuk side-arm diversion and 22 km near the Dniester Liman estuary. Southern slopes are steep and elevated while the northern slopes are gently sloping. The slopes are composed of marls, clays and sands and cultivated for vineyards and orchards. The floodplain is 0.5–1.5 km wide downstream Dubossary, widening to 4–6 km near Tighina (Bendery) and 14 km at the Turunchuk side-arm diversion. The floodplain is cultivated for orchards, croplands, and vineyards and protected from flooding by levees 4–6 m above the river. Substantial areas of the floodplain by Kuchurgan and the Turunchuk side-arm are occupied by swamps called ‘Plavni’. The swamps are intersected by narrow channels covered by reeds, canes, willows and other shrubs. Here

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the river channel is sinuous (sinuosity coefficient = 2.5), creating numerous bends with large curvature radii that sometimes connect with the other parts of the channel and oxbow lakes. At river-km 148 the Turunchuk side-arm begins, flowing 58 km downstream to the village Belayevka where it rejoins the Dniester. The Turunchuk is sinuous, 35–75 m wide, 5– 7 m deep, and flow velocities varying from 0.5 to 1 m/s. The riverbed is covered by sand and silt, and the banks are steep. The width of the main river upstream of Turunchuk varies from 100 to 200 m, and downstream it narrows to 50–100 m. River depth in riffles is about 1.5–2.5 m, and 4–8 m in pools. Flow velocity reaches 0.5–0.9 m/s in riffles and 0.2–0.4 m/s in pools. The riverbed is covered by sands and silts that are constantly moving, creating bars, dunes and ripples. Typical riffle-pool sequences disappear downstream of river-km 140 where the river slope is 0.05%. The catchment of the Southern Bug encompasses areas of the Volyn–Podolsk and Dnieper plateaus, and Black Sea coastal basin. On the Volyn–Podolsk plateau, catchment relief is flat and incised by deep valleys of small tributaries (Kaganer et al. 1969). The river begins in the Khmelnitskyy region at 321 m asl, flowing about 806 km southeast before discharging into the Dnieper–Bug estuary on the Black Sea. In total, the catchment area equals 63,922 km2. The catchment is pear-shaped with a narrow upper part, and asymmetric middle and lower areas. Its average slope is 0.4%. Mean annual runoff of the river is 3.4 km3, corresponding to an annual discharge of 108 m3/s. Mean annual turbidity of the river is 0.15 kg/m3. The drainage network of the river includes 11 medium-sized tributaries such as Sinukha, Kodyma, Sob, Rov and Zgar Rivers, and 6638 small rivers having a total length of 20 109 km. River density of the catchment is about 0.33 km/km2. The Southern Bug can be divided into five representative reaches. From the source downstream to the village Novokonstantinov (130 km), the river valley is slightly sinuous, 2–3 km wide, and with low sloping flanks 20–50 m in height. The floodplain is 0.6–1 km wide, swampy, and covered with meadows and shrubs. In spring during high flows, the floodplain is flooded by about 1–2 m for about 10 days. The riverbed is non-uniform and composed of silt and peat. The river channel gradually widens from 5 m to 70–90 m, having a mean depth of 2 m and flow velocity of 0.2 m/s. In the next morphologic reach, the river flows 362 km from the village Novokonstantinov to the city of Hayvoron. The river valley is V-shaped and about 1.5–3 km wide. Sideslopes are steep, ranging from 30 to 80 m in elevation. The floodplain is 0.5–0.8 km wide, flat, and composed of loamsand. The river channel is slightly sinuous, around 70–100 m wide, 2.5–3 m deep, and with mean flow velocities about 0.3 m/s. The riverbed is composed of sand and silt. Between the city of Hayvoron and village Alexandrovka, the river flows through a trapezoidal valley 1.5–3 km wide with steep side-slopes of sand and loam-sand with extrusions of basalt rocks and scree.

PART | I Rivers of Europe

Upstream of the city Pervomaysk, the floodplain is 500– 600 m wide and decreases to 100–150 m downstream of the confluence with the Savranka River. The floodplain is flooded annually to a depth of 3–3.5 m for 10–15 days. The river is mildly sinuous, braided with numerous islands about 100–300 m long and 30–80 m wide. The river has many rapids, mostly between the cities of Hyvoron and Pervomaysk. The mean width of the channel is 100– 150 m, and depth is 0.4–1 m in rapids and 2.5–3.5 m in pools. Mean flow velocity is 0.8 m/s in rapids and 0.2– 0.3 m/s in pools. The riverbed is composed of boulders/pebbles in rapids and sand in pools. The river flows 95 km between the villages Alexandrovka and Novoperekopskoe through a trapezoidal valley ranging from 4.5 to 6 km wide. Valley side-slopes are steep, about 80–100 m high, decreasing at the end of the reach to around 20–30 m. The floodplain, called ‘Bugs Plavni’ is regulated on both sides of the channel at a width of 1.5– 2 km. The floodplain is mildly wet, mostly covered with dense reeds, and partly used as a cropland for rice and vegetables. The river channel is slightly sinuous, 100–170 m wide, 3–4 m deep, and has an average flow velocity of 0.3 m/s. Upstream of the city Voznesensk, the riverbed is sand–silt with developed aquatic vegetation near the banks. The river then flows 39 km downstream of the village Novopetrovskoe to the river mouth. The river valley is 3.5– 5.5 km wide with side-slopes 40–60 m in elevation. The floodplain width ranges from 200 to 700 m and is absent near the river mouth. The floodplain is intersected by vegetated side-arms of the river. The river channel is mildly sinuous, 0.8–2 km wide, and 2–3.5 m deep. Flow direction and speed is governed by the winds from the sea (Sokolov 1952; Anuchin 1956; Kaganer et al. 1969; Alymov et al. 1978). The Dnieper is the third largest river of Europe, with a length of 2201 km and catchment area of 512 293 km2. The river originates in the Valday Hills at 220 m asl. There the river is joined by six tributaries with lengths >500 km: Berezina (613 km), Sozh (648 km), Prypiat (802 km), Desna (1187 km), Psel (806 km), and Inhulets (551 km). The upper Dnieper is a small river flowing in a valley 2 km wide. The river is narrow (max = 30 m), sinuous, and with low banks. The width of the valley gradually widens to 3–10 km downstream of the city Dorogobuzh. Here the river channel is sinuous, ranging from 40 to 125 m in width. Just upstream of the city Orsha, the river crosses a limestone ridge, forming the Kobelyaksk Rapids. The channel narrows to 20 m, slope increases to 0.5%, and flow velocity reaches 0.8–1.0 m/s. A floodplain is absent in the upstream part of the river. Downstream of Orsha, the Dnieper flows south through a wide valley with high banks. Near the city Loev, the floodplain valley widens as the river flows through the Polesse Lowland. At the confluence with the Desna River, the floodplain width ranges from 12 to 14 km. The floodplain is swampy and intersected by side-arms of the river and various oxbow lakes. The channel of the river is unstable, sinuous, and composed of riffle-pool sequences.

Chapter | 13 Western Steppic Rivers

Downstream of the city Kiev, the capital of Ukraine, is the middle reach of the river. The width of the river valley significantly increases and terraces appear on the left side. The floodplain narrows to 2 km near the city of Kanev, gradually increases again downstream to 9 km near the city of Cherkassy. Here the river width ranges from 200 to 1200 m. Downstream of its confluence with the Teasmeny, the river reaches a ridge of basalt rocks. Before the construction of large reservoirs, the river here had six large and 60 smaller rapids. Downstream from Dneprovsky dam, the river splits into two channels that form a large island called Khortitsa where before the 18th century was a military settlement of Ukranian Cossacks, the so-called Zaporozhskaya Sech. The river valley then narrows to only 4 km before widening downstream to 23 km in a 50-km long lowland called Horses Plavni. Near Nikopol, the river valley again narrows to 5 km before widening further downstream to 3–7 km in the lowland called Buzuluk Plavni. The right side of the valley is relatively high with mean altitudes of about 80 m asl. The river valley bottom is filled with a deep layer of alluvial deposits, indicating that tectonic processes lowered the valley and caused development of the lowlands and the river mouth (Sokolov 1952; Kupriyanov et al. 1966; Vishnevsky & Kosovets 2003). The Donets River is a relatively small tributary of the Don River, being 1053 km long with a catchment covering 99 422 km2. The river has 10 tributaries with lengths >100 km; the most important being the Oskol and Lugan rivers. The river originates in the south of the Russian Lowland and flows through the Donets Gorge in the northeast. From its source to Belgorod, the river flows through a 8– 12 km wide valley with steep side-slopes intersected by gullies. Its floodplain is 1 km wide. The width of the upper river is 10 m, slightly sinuous, and the riverbed is composed of silt. The 22-km river reach just downstream of Belgorod enters backwaters from Belgorodskaya reservoir. Another backwater influenced river section is 15-km downstream with the confluence of the tributary Nezhegol River where Pechenezhsk reservoir is found. Downstream of Pechenezhsk dam, the river flows through a wide floodplain and has meandering channel 40–50 m wide, and 1.5–2.0 m deep. The meander wavelength ranges from 250 to 300 m with a radius of curvature of 150 m. The riverbed is sandy. Downstream of the confluence with the Aidar River, the radius of curvature of river meanders increases to 400–500 m with a wavelength up to 1 km and river width of 200 m. Downstream of Kamensk–Shakhtinsk, the river flows through the Donets Gorge. The river valley deepens to 40– 60 m, side-slopes are steep and limit side erosion and force the river to create embedded loops. The riverbed is 3–5 m deep and filled with pebbles and cobbles. Below the gorge, the river flows another 40 km before its confluence with the Don River. Here the valley is 20–26 km wide and has a floodplain 3–4 km wide. The channel has a sandy bottom and follows a sequence of meandering and straight reaches. There are numerous oxbow lakes and side arms in the flood-

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plain. Horizontal deformations mostly cause reshaping of islands and concave banks at an annual rate of 2–3 m/year (Protasiev et al. 1973; Alymov et al. 1978). The Don River is a typical lowland river with a gentle longitudinal profile; its average channel slope is only 10 cm/ km. The source of the river is in the Russian Lowland at 179 m asl. The river flows 1970 km through the Russian Lowland and Azov Lowland before discharging into Taganrog Bay on the Azov Sea. Its catchment covers 328 053 km2 (excluding the Donets catchment), and the Donets (1053 km), Khoper (979 km), and Medveditsa (690 km) are its largest tributaries. The river can be divided into three sections based on hydrology and climate. The upper segment is represented by a reach 1015 km in length that flows from the source to the Kazansk Stanitsa, the middle section is between Kazansk Stanitsa and the city Kalach (1015– 1468 km), and the lower section flows from Kalach to the river mouth (1468–1979 km). The upper segment of the river is weakly sinuous. In the 180 km reach upstream of the confluence with the Voronezh River, the river width widens from 80 to 130 m, and depths can be 2 m in pools. The riverbed is made up of coarse sand and pebble deposits that form riffles, bars and islands. Downstream of the confluence with the Voronezh River, the river channel meanders at wavelengths of 1 km. River width increases up to 160 m, and the floodplain widens from 2 to 6 km. The character of the river changes upstream of the confluence with the Khoper River. The channel is mostly straight, and flows on the right side of the river valley. Downstream of the confluence of the Medveditsa River, the river channel becomes more sinuous. River width increases to 300–350 m, and the floodplain is wide (6– 7 km) and incised with oxbow lakes and side-arm channels. The floodplain is regularly inundated in spring for up to 40 days. The bedforms are typically sandy riffles with alternate bars that move downstream at an annual rate of 15–20 m/ year. The downstream section of the river is on a wide floodplain with a width ranging from 5 to 25 km. Side-slopes of the valley are 20–30 m in elevation and relatively gentle. River width ranges from 400 to 600 m, and river depth is 4–6 m in pools and 0.7–1.0 m in riffles. The reach 300 km upstream of the city Volgodonsk is influenced by the backwaters of Tsimlyansk reservoir. The reservoir was created simultaneously with the building of the Volga–Don canal in 1950–1951. Downstream of the city Rostov-on-Don begins the Don River delta with an area of about 600 km2. The delta comprises a number of side-arms: Perevoloka, Egurcha, Kalancha and Old Don. The river creates a large bar at the entrance to the Azov Sea (Sokolov 1952; Protasiev et al. 1973). The Kuban River is the largest river of the northern Caucasus and originates at the confluence of the mountain streams Ullukam and Uchkulan (1340 m asl) that flow from glaciers on Elbrus Mountain. The river flows 870 km southwest towards the Kuban delta on the Azov Sea and drains an area of 62 851 km2. The river can be subdivided into three

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distinctive sections: a Caucasian mountain area, Subcaucasian upland (southwest steppe), and the Kuban lowlands with the Kuban delta. The fluvial network of the Kuban is composed of 14 516 rivers with a total length of 41 639 km. The largest tributaries are Teberda, Zelenchuk, Laba, Belaya, Pshekha and Pshish. A distinctive feature of the catchment is its strongly asymmetric shape because all major tributaries of the river are on the southern (Caucasian) side. These tributaries are typical mountain streams flowing in narrow and deep valleys with steep slopes. Their channels are embedded in rocks or formed by coarse deposits (cobbles, pebbles, and gravels). A significant area of the Kuban catchment is in the mountains, and 264 km2 or 0.5% of the catchment area is covered by glaciers and permanent snow. In the upper section, the Kuban is a typical mountain stream characterized by steep longitudinal gradients (6%) and high flow velocities (up to 5 m/s). The river valley at the Ullukam–Uchkulan confluence is 1.5 km wide, and the river flows over bedrock covered by cobbles and boulders. The channel width downstream of the confluence is 20 m, widening up to 130 m downstream at Degtyarevsk Khutor. Flow depth is highly variable in this section because of numerous rapids and frequent channel branching. The mountain reach stretches from the river source to the village of Nevinomisk (river-km 701), where the flow is then regulated by Nevinomisk reservoir. Downstream from Nevinomisk, the river enters the lowland, its valley widens, longitudinal gradient decreases, and the current slows. The middle section of the Kuban flows between Nevinomisk and its confluence with the Laba River near the city of Ust-Labinsk. The river flows through a wide valley (up to 10 km). The northern side of the valley is steep and rises 20– 40 m above the valley bottom. The valley has a wide (up to 4 km) floodplain covered by trees and shrubs. The river channel is mildly sinuous along the northern side of the valley but crosses the floodplain at some places. Near the city Kropotkin, the channel has free-flowing meanders. The channel bed is coarse alluvial deposits of gravel and sands. Mobile alluvium produces bedforms of various types, ranging from alternate and point bars to submerged dunes and sand ripples. Width of the channel varies from 70 to 160 m. River depth in riffles is about 0.5–1.5 m and 2–5 m in pools. Flow velocity ranges from 1.5–2.0 m/s in riffles to 0.5– 1.0 m/s in pools. Average slope of the river is 0.6%. The lower section of the river begins downstream of the confluence with the Laba River. Discharge increases substantially, and the river valley and floodplain widen. At certain locations, the floodplain width is 20 km and river width varies from 160 to 200 m. The channel bed consists of alluvial deposits of fine gravel and sand, and only sand downstream of the Pshish confluence. Alluvium transport results in regular sequences of riffles and pools in this section of the river. The river (40 km long) between the villages Voronezskay and Pashkovski was flooded after construction of a 22-m high dam for Krasnodar reservoir (46 km long, 8–

PART | I Rivers of Europe

12 km wide, and 10–16 m deep). Many southern tributaries flow into Krasnodar reservoir. At river-km 116, a side-arm splits from the main channel and is a primary feature of the Kuban delta. The Kuban delta was formed in the sea as a result of alluvial deposition in the lower Holocene. In the past, the main channel of the river has changed many times between various side-arms such as Protoka, Temrukski, Bugazski and Kurkui. Presently, these arms are Plavni. Sea boundaries of the delta correspond to depths of 5–7 m around 3–4 km off shore, and depend on mixing of fresh and salt water. The delta can be divided into two parts based on its hydrology and morphology. The upper section of the delta is presently used for growing rice and is periodically flooded. The lower part is at the interface with sea and comprises Limans and Plavni. In the arms of the delta, velocity varies from 0.2 to 0.4 m/s at low water levels, 0.6–1.0 m/s at medium levels, and 1.2– 1.9 m/s at high water levels. The maximal depth ranges from 1.7 m in riffles to 4.5 m in pools.

13.4.2. Hydrology and Temperature Although the rivers of the Western Steppe have similar climatic, geomorphologic, and hydrological conditions in their downstream areas, their hydrology and temperature regime differ. Specific conditions in the upper watersheds cause distinctive hydrologic regimes between the rivers. In the middle reaches of many rivers, the hydrology is influenced by runoff from large reservoirs, and agricultural and industrial use of river water (Vishnevsky & Kosovets 2003; Loboda 2005). River runoff of the Western Steppe has been recorded since 1880, and long-term records for selected rivers are shown in Figure 13.4. These records show a major difference between the western (the Dniester) and southeastern (the Kuban) parts of the steppe and the rest of the territory. Although most of the steppe rivers have single peaked hydrographs showing spring flooding, the hydrograph of the Dniester and the Kuban show frequent flooding during summer and autumn from rain events. Discharge records of the Dnieper (at Kiev) and Don (near Razdorskay) show the influence of reservoirs on river hydrology; that is a reduction of maximal runoff and an increase in the mean low water discharge (Figure 13.4). The seasonal distribution in river runoff (monthly data averaged over the past 20 years) is shown in Figure 13.5. A comparison of hydrographs for the western part of the territory (Dniester and Southern Bug) and middle and eastern part (Dnieper and Don) indicate a 1-month lag in the appearance of the spring peak. The catchment of the Dniester can be divided into three zones distinguished by patterns in runoff. The Carpathian part is a major area for runoff formation (Vishnevsky 2000), characterized by a large number of floods during the year. These floods are created by intensive precipitation during the warm season and by snowmelt. The Carpathian tributaries of the Dniester comprise only 17% of the catchment area but

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Chapter | 13 Western Steppic Rivers

FIGURE 13.5 Seasonal distribution in discharge.

FIGURE 13.4 Long-term records of monthly mean runoff at selected gauging stations.

contribute 50% to the annual discharge. Significant precipitation together with steep slopes and relatively low temperatures are primary factors causing the high runoff rates (coefficient of runoff is about 0.5–0.6). About 30% of river discharge is contributed by the tributaries of the Dniester draining the Volyn-Podolsk plateau and 20% are formed by the remaining 60% of the catchment area in the steppe. Mean annual discharge increases from 6.2 m3/s near the village Strelki to 318 m3/s near Tighina (Bendery), and remains practically the same until the river mouth. The hydrology of the river is characterized by high discharge during spring (40–50% of the annual runoff), relatively high runoff because of rain events during summer (30–40%), and low discharge during winter (10–20%). During floods (10–12/ year), water levels increase 1–3 m in the upper section of the river, and 4.3–5.8 m in the middle and lower sections. Mean monthly temperature of the water in winter is 0 C, 6– 10 C in April, 12–16 C in May, and 18–20 C in June. Maximal temperatures are found in July, as high as 27– 33 C. Temperature decreases gradually during late July and August and then relatively quickly during September and October. Ice cover develops at the end of December and in January, although the river may not freeze during warm winters (Kaganer et al. 1969). The hydrology of the Southern Bug is characterized by a distinctive high spring flow, low flow in summer with short floods from rain events, and higher flows during autumn and winter. The runoff distribution over the year is non-uniform with 70% of runoff occurring during the spring flood, 18% from low water during summer and autumn, and 12% from winter flows. The mean annual discharge increases 4.7 m3/s at Pirogovtsi (730 river-km) to 108 m3/s at the mouth (0 river-km). Significant runoff comes from two large tributaries (Sinukha at 28.5 m3/s; Inhul at 12.7 m3/s), while runoff from other tributaries is relatively low from 1 to 3 m3/s. In spring, runoff increases sharply at the end of February beginning of March coinciding with ice breakup and usually as a single peak. Water levels can increase by 2–7 m. Flood waters recede at a rate approximately equal to the rate of rising, and summer low flows occur by the middle of May beginning of June. During summer, upstream reaches of the river fall dry, and summer floods usually last on average

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10–15 days and increase water levels by 0.5–1.5 m. Periodic flooding also can occur during winter. The middle and lower river freezes during late November early December. Ice cover can be quite thick; a maximum of 70 cm was reported in 1968 near the village Leletka. Mean monthly water temperature increases to 8–12 C in April, reaches 20–25 C during July and August, and gradually decreases to 8– 10 C during September–October. The hydrology of the Dnieper is mainly associated with landscape and climate processes in the upper catchment. Snowmelt waters in spring contribute 50% to annual runoff, and represent the basis of the water balance of the catchment. Subsurface and groundwater flows make up 27% of annual runoff, and the remaining runoff comes as floods from rains mostly in autumn. In the upper catchment, the spring flood starts in early April or even late March with an abrupt rise in water level. The spring flood peaks in mid April in the upper catchment and early May in the lower catchment. The duration of the spring flood significantly increases with the length of the river, being shortest in the upper catchment. The spring flood increases water levels in the upper catchment, but little rise in water level is seen downstream. Minimal runoff is observed during winter just before the spring flood. Amplitudes in water level significantly vary along the river because of variability in geomorphology of the river valleys and floodplains. In the upper catchment near the city Dorogobuzh, maximal yearly amplitude in the water level is 5.8 m; whereas downstream where the floodplain widens the amplitude decreases to 3.7 m near the Bykhov and to 2.5 m near Kherson. Mean annual discharge increases from 97 m3/s near Smolensk to 1670 m3/s near the river mouth. The specific discharge decreases about twofold from north to south, from 6.9 (Smolensk) to 3.5 L/s km2 (near the mouth). Ice cover develops on the river in the upper catchment during late November. Forming of ice cover is observed during late December in the downstream catchment. Ice cover is unstable, thawing and freezing periodically over winter. Ice cover is gone by early March in the lower catchment and by late March early April in the upper catchment. Ice breakup lasts 5–7 days in the upper catchment and 1–3 days in the lower catchment. High spring floods, low flows during summer with periodic floods from rains, and higher flows during autumn and winter are features of the hydrology of the Donets. Most runoff (60%) occurs during the spring flood, 33% from low water during summer and autumn, and 7% during winter. Mean annual discharge increases from 17.5 m3/s near Ogurtsovo (944 river-km) to 178 m3/s at the mouth (0 river-km). Discharge increases abruptly during late March early April with a distinct peak from the spring flood. Water levels during flooding increase by 2–3 m in the upper catchment and by 7.5 m in the lower catchment. Floods recede at a slower rate than when they begin and summer low flows occur by mid May. Summer floods are normally short, only lasting 5–10 days, and increase water levels by 0.5–1.0 m. Flooding can also occur during winter. The river freezes

PART | I Rivers of Europe

during early December and water temperature during winter is 0 C. Ice breakup occurs during late March, lasting for 2–3 days. Mean monthly water temperature increases to 8– 12 C in April, reaches 20–25 C during July–August, and gradually decreases to 8–10 C during September–October. In general, the hydrology of the Don resembles that of the Dnieper because of their similar geographical position. Soil properties, precipitation, and river regulation distinguish the runoff distributions of the two rivers. Around 50% of the annual runoff of the Don is from snowmelt. Because of karstic geology, the contribution from groundwater to annual discharge is quite high and makes up about 30%. Summer and autumn rains contribute a relatively small proportion, 20%. In the upper catchment, spring flooding starts in late March early April and is characterized by an abrupt rise in water level. The spring flood is maximal in mid April in the upper catchment and early May in the lower catchment. The duration of the spring flood significantly increases along the length of the river. Thus, summer low flows are normally established during May in the upper catchment but in early July in the lower catchment. Floods from rains are usually observed in autumn, and minimal runoff is observed during winter just before the spring flood. Annual amplitudes in water level vary significantly along the river, reflecting changes in geomorphology of the river valley and floodplain. Mean annual discharge of the Don increases from 37 m3/s near Voronez to 687 m3/s near the mouth of the Donets river. Ice cover develops during late November on the upper river, and ice breakup is observed during late December in the lower river. Duration of ice breakup is 5–7 days in the upper river and 1–3 days in the lower river. Ice cover is unstable and can thaw and freeze periodically over winter. Ice cover is lost by early March in the lower river and during late March early April in the upper river. In contrast to all other rivers of the Western Steppe, the catchment of the Kuban River has a significant area influenced by permafrost, glaciers, and permanent snowfields. Melt waters from the glaciers and snow fields contribute significantly to the hydrologic and temperature regime of the river. These melt waters make up 49% of the average annual runoff in the upper catchment, and 32% in the lower catchment. Runoff from rain contributes 27 and 35%, and groundwater delivers 21% and 35%, respectively. Mean annual discharge at the mouth (0 river-km) is 360 m3/s. The runoff is distributed non-uniformly over the year with highest contributions observed during spring and summer (30% and 50% in the upper catchment, 50% and 25% in the lower catchment, respectively). Lower runoff is usually observed in winter and autumn (1% and 10% in the upper catchment, 10% and 15% in the lower catchment, respectively). The flood regime of the river is characterized by an extended period of summer flooding since melt water from snow fields and glaciers adds to the water from periodic rain floods. Hydrology of the lower catchment includes a spring flood from snowmelt in the lowlands and enhanced precipitation. In the upper catchment, the rise in water level

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Chapter | 13 Western Steppic Rivers

TABLE 13.2 Flow regime (in m3/s) of the major Western Steppic rivers A (km2)

River

Station

Period

NQ

MQ

Dniester

Sambor Mogilev-Podolsk Bendery

1946–2000 1983–2000 1945–2000

850 43 000 66 100

0.05 48.6 91.0

10.9 255 318

702 2700 2800

14 000 55.6 30.8

S. Bug

Leletka Podgyre Alexandrovka

1964–2000 1958–2000 1914–2000

4000 24 600 46 200

0.36 2.0 2.6

14.2 61.2 89.3

801 2600 5320

2200 1300 2100

Dnieper

Nedanchichy Kiev Dnieprodzerzhinsk

1972–2000 1966–2000 1964–2000

103 000 239 000 424 000

93.1 12.0 375

Donets

Ogurtsovo Protopopovka Lisichansk

1959–2000 1968–2000 1925–2000

5540 19 400 52 400

1.3 8.1 3.9

Don

Kazanskaya Kalach Razdorskaya

1882–2004 1876–2004 1881–2004

102 000 222 000 378 000

44.4 53.3 44.2

318 675 774

Kuban

Kosta Khegaturov Ladozhskaya Tikhovskaya

1921–2005 1928–2005 1911–2005

3800 19 800 47 500

6.0 2.9 23.4

78.2 128 373

563 1080 1530 17.5 46.7 104

HQ

4150 10 700 9200

HQ/NQ

44.6 890 24.5

1090 774 3310

830 96 850

8280 11 500 13 000

186 216 294

897* 864* 1480*

150 300 63.2

A: catchment area upstream of the gauging station, NQ: lowest measured discharge, MQ: arithmetic mean annual discharge, HQ: highest measured discharge (symbol (*) indicates that discharge records do not include data from the catastrophic flood of 2002).

begins usually in April, peaking in June–July, and receding in September–October. The spring flood begins in late February and often is represented by 2–3 distinctive flood waves that result from the non-uniform distribution of snow in the lowlands and highlands. Although rain caused floods are frequent in autumn, their magnitudes are usually insignificant. Maximum amplitude in water level generally increases downstream from 2 m (village MikoyanShakhara) to 6 m (Ust-Labinsk), and then decreases again downstream of Ust-Labinsk. In the upper catchment, the mean monthly water temperature in winter is 0 C, 4–6 C in May, 10–16 C in June– July, and 16–22 C in August–September. In the lower catchment, the temperature regime is significantly changed by the Krasnodar reservoir. Water in the reservoir reaches higher temperatures earlier and maintains them longer compared to the river before construction. In the Kuban delta, the mean annual water temperature differs little between the different arms, varying from 12.7 C (Slavyansk-on-Kuban) to 12.9 C (Baranikovski). Maximum observed temperatures were 29.9–31.0 C (Slobodka and Temruk) and minimum temperatures reached 0 C. Ice cover develops in the upper catchment only in limited areas near riverbanks. In-stream ice forms intensively and creates backwaters at narrow sections. Complete ice-cover is usually observed downstream of the village Batal-Pashinsk, although not every year and the river can freeze and thaw many times during the winter. Ice cover appears in late December and breakup in early February. Ice cover is often observed on the seashore, Limans and Plavni of the Kuban delta. Winds significantly affect ice

cover development in the delta area, often causing breakups, drifts, and dispersion of ice. The width of ice cover near the northern shores of the delta is 12–13 km (Primorsk– Akhtarsk), and 2 km near the southern shores (Temruk). Ice cover thickness varies from 10 to 25 cm. A summary of the characteristics of the flow regime for selected rivers of the Western Steppe is presented in Table 13.2. For each river, three gauge stations were selected as representative for the upper, middle, and lower parts of each river.

13.4.3. Biogeochemistry According to recent reports, most rivers of the Western Steppe are classified as ‘polluted’ or even ‘very polluted’ (Fashuk 1998; Zubkova & Shlenk 2004; Lure et al. 2005). In general, the tributaries of major fluvial systems are most severely polluted because of their insufficient dilution capabilities. Contamination mainly originates from the agricultural sector, and mining and metallurgical industries in the Donbas and other industrial regions. Lack of sewage treatment facilities, frequent industrial accidents, and leakages from non-official pesticide dumps also are important factors affecting the biochemical characteristics of water resources. Generally the transport of suspended and dissolved substances by rivers of the Western Steppe can be described as follows (Kaganer et al. 1969; Strelets 1987). Turbidity of the rivers increases from north to south, being lowest in the rivers of the Ukrainian Polesse where turbidity is about 10 g/m3. On the left side of the Dnieper catchment, turbidity

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increases to 20–50 g/m3. Values of 150–200 g/m3 have been reported for rivers of the Donbas and rivers of the Azov Lowlands, and highest values of 200–500 g/m3 are found in Carpathian tributaries of the Dniester and in the Kuban and its tributaries. In contrast, mineralization of the rivers is characterized by low values in the Carpathian rivers (200 mg/L), and increasing substantially across the territory from west to east. Mineralization increases from 500– 550 mg/L to 800–900 mg/L across the Southern Bug catchment and reaches a maximum of 1200–1250 mg/L in the Donets catchment. Increases in mineralization of the rivers of the Donbas and Azov Lowlands are derived from water from mines and industrial complexes. A comparison of mineralization over the past 50 years indicates an increase in mineralization of rivers in the Ukrainian Polesse (from 200 to 300–400 mg/L). The diversity of geographical and geological features across the Western Steppe, along with specific patterns of land use and industrial development, produces a diverse chemical composition of the rivers. In general, the rivers can be classified as belonging to the hydro-carbonate calcium group. The Carpathian rivers and rivers of the Polesse are especially rich in HCO3 (30–35%). Sulphate and sodium content are increasing in the eastern part of the territory, especially in rivers affected by mine drainage. Nitrogen, phosphorus, and silicon are high in rivers affected by runoff from croplands, and sewage waters from agricultural and urban water treatment plants. According to a report of the Ukrainian Agrarian Ministry in 1990, the amount of mineral fertilizers used on the territory was 4.25 million tons. This amount was significantly reduced over the last decade and in 2000 the Ministry reported 0.28 million tons of fertilizer being used in the territory. The use of organic fertilizers also was reduced substantially (9 lower). However, the content of biogenic chemicals in the rivers is still high in some places. For instance, concentrations of phosphorus in the Donets near Lisichansk are reported to be as high as 1.5 mg/L. High levels of oils (0.2–0.3 mg/L) are also found in the waters of the Donets. The use of pesticides has been greatly reduced with the loss in agriculture and presently pesticides are undetectable in most rivers in the territory. The Dniester annually transports about 2.5 million tons of suspended sediment and 3 million tons of dissolved substances. Its average turbidity is 250 g/m3 and average mineralization is 300 mg/L. Mineralization decreases during flooding to 150–250 mg/L and increases during low-water to 400–500 mg/L. The composition of mineralization is dominated by HCO3 and calcium. The waters of the Dniester are oxygen rich, especially in the upstream mountainous reaches, ranging from 8 to 15 mg/L. Levels of organic nitrogen (0.76–2.33 mg/L) and total organic matter (10.2– 43.8 mg/L) have increased twofold over the past 20 years. In September 1983, a catastrophic chemical disaster occurred at the Stebniks potassium factory, resulting in about 4.5 million m3 of toxic chloride–fluorine compounds entering the river near the city Truskavets. This toxic spill caused

PART | I Rivers of Europe

almost total destruction of the fishes in the upper and middle Dniester. Because of high flushing rates and a special engineering treatment of the river channel, the level of toxic chemical compounds was reduced to its previous level and analysis of major hydrochemical indices indicate that the Dniester is now considered moderately polluted and polluted (Zubkova & Shlenk 2004). The waters of the Southern Bug are characterized by high variation in mineralization, ranging from 350 mg/L at its source to 1600 mg/L at the mouth. From 1980 to 1983, a shift in ion composition from hydro-carbonate calcium to sulphate– sodium was recorded for the river. Its waters are oxygen rich, concentrations ranging from 7.6 to 13.5 mg/L. The concentration of non-stable organic compounds is low (12.4 mg/L), but the concentration of stable organic compounds is relatively high and bichromatic oxidization is 61.8 mg O2/L. Mean concentration of phosphorus is 0.31 mg/L, NH4 is 0.22 mg/L, and NO3 is 0.17 mg/L. On average, turbidity of the Southern Bug ranges from 50 to 150 g/m3. Chemical composition of the Dnieper reflects the properties of waters coming from its tributaries in the upper catchment. The Dnieper belongs to the hydro-carbonate calcium group. Mineralization during summer ranges from 230 to 280 mg/L in the upper catchment and decreases to 200– 230 mg/L downstream of the city Smolensk where the river crosses a swamp. In the forested steppe zone, mineralization increases due to highly mineralized water from the tributaries Teterev and Desna. Mineralization ranges from 250 to 350 mg/L during winter, decreasing to 70–100 mg/L during spring high flows, and increasing to 200–250 mg/L during summer and autumn low flows. Ion composition is relatively stable along the river and is dominated by HCO3. Average total phosphorus varies from 0.17 mg/L at Nedanichi to 0.24 mg/L near Kherson. The average content of NO3 varies little from 0.14 mg/L (Nedanichi) to 0.16 mg/L (Kherson), whereas NH4 decreases from 0.43 to 0.24 mg/L at these locations. Turbidity of the Dnieper decreases downstream because of clear water entering from tributaries, decreasing from 82 g/m3 near Mohylev to 42.5 g/m3 near Kiev and to 27.5 g/m3 near Verhne–Dnieprovsk because of reservoir effects. Maximal turbidity occurs during spring high flows and minimal values are found in winter. The concentration of suspended sediments significantly increases (from 70 to 240 g/m3) along the Donets due to high loads from tributaries. For instance, average turbidity ranges from 500 to 1000 g/m3 in the tributaries Derkul and Kalitva. The high turbidity results from industrial pollution, and the river has extremely high concentrations of biogenic chemicals. Concentration of phosphorus reaches 1.68 mg/L, and the average concentration of NO3 is 1.88 mg/L. The river also has high levels of oils (0.2–0.3 mg/L). Average oxygen content ranges from 8.3 to 9.2 mg/L and is highest in the upper reaches of the river. In the upper Don, the chemical composition is derived from tributaries flowing through forest steppe having soils poor in chlorides and sulphates. The river water is dominated

Chapter | 13 Western Steppic Rivers

by hydro-carbonate calcium ions the entire year and mineralization ranges from 110 to 490 mg/L. Mineralization is lowest during spring high flows (100–160 mg/L) and is highest during summer low flows when groundwater inputs dominate the system. Dissolved oxygen is sufficiently high during the entire year at 8–12 mg/L (70–100% saturation). Water oxidization is 4–12 mg O/L, and bichromatic oxidization is 7–16 mg O2/L. The biogenic composition of the water is dominated by nitrates, varying during the year from 0.1 to 1.2 mg/L, and the contents of NH4, NO2 and phosphates are low (0.01–0.08 mg/L). The pH varies from 7.0 to 8.3, being highest during summer low flows. In the middle reach of the Don (from Kazansk Stanitsa to the city of Kalach), mineralization is relatively higher than in the upper reach. During spring high flows, mineralization decreases to 150–210 mg/L and then increases to 470– 580 mg/L during summer low flows. The content of dissolved organic matter is low with an oxidization of 4–9 mg O/L. The concentration of biogenic compounds is slightly higher than in the upper part, being dominated by nitrates (0.1–0.4 mg/L). In the lower Don (from Kalach to the mouth), the river flows through steppe with somewhat salty soils. Here the content of dissolved chlorides and sulphates increases and carbonate content decreases. Mineralization ranges from 240 to 390 mg/L during spring high flows and increases up to 480–890 mg/L during summer low flows. Long-term records from monitoring stations on the river show an increase in mineralization over the past 20 years by 20–30%, whereas the content of organic substances has slightly decreased. High variation in biogenic compounds is caused by biological processes in Tsimlyansk reservoir. The waters of the Don are used intensively for agriculture and industry, and have numerous sewage inputs, in particular, from the Voronezh and Donets rivers. Based on reports of Roshydromet, the Don is characterized as being mildly to heavily polluted. In the upper sections of the Kuban, turbidity is relatively low (average value 204 g/m3 near the village Kosta Khetagurov), and non-uniformly increases downstream (930 g/m3 near Temizhbekskay stanitsa, 650 g/m3 near Krasnodar). The origin of Kuban waters explains its distinctive mineral composition. Melt water from snowfields and glaciers increases mineralization and the chemical composition becomes more complex. In the headwaters, the amount of dissolved substances is low: 1–3 mg/L on average. Mineralization increases because of dissolution of carbonate, calcium and magnesium from tributary watersheds. Mineralization is reduced during spring and summer floods and significantly increases, for example up to 1000 mg/L near Armavir, during autumn and winter because of the dominance of groundwater to river flow. Water in the upper Kuban belongs to the hydro-carbonate calcium group. Downstream of Nevinomisk, the composition changes to the sulphate group because of increased groundwater inputs from alluvial deposits. Mineralization varies from 265 to 1015 mg/L. Ion composition includes substantial content of carbonate HCO3 (101–289 mg/L), sulphate (67–417 mg/L), chloride (17–120 mg/L), and calcium

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(41–97 mg/L). The average content of NO3 varies significantly from 0.54 to 8.74 mg/L during the year and along the river, whereas concentrations of NH4 are much lower (0.01– 0.47 mg/L). Waters of the Kuban are oxygen rich, especially in the upstream mountainous sections, and range from 8.6 to 16.6 mg/L. Although organic N and P are detectable in the river at low concentrations, the quality of water in the Kuban, especially in the arms of the delta, is characterized as ‘polluted’ and ‘very polluted’ (Lure et al. 2005). Poor water quality is caused by high loads of metals, phenols, and pesticides transported with sewage and introduced as a result of intensive agriculture development. Pesticides were used quite intensively from 1980 to 1986 and >100 different kinds have entered the Kuban. The total annual volume of pesticides for growing rice in the Kuban delta was 3500 tons. In the 1990s, the volume of pesticides used was reduced fourfold and the area of rice fields was significantly reduced. However, the level of pesticide pollution of water in the mid-1990s was still dangerously high (Lure et al. 2005). More recent observations indicate that concentrations of pesticides in the river have been further reduced to around 0.007–0.008 mg/L. To summarize some of the chemical characteristics of the Western Steppe rivers, Figure 13.6 shows long-term changes in nitrogen and phosphorous content in the Dnieper reservoirs from 1945 to 2005. The data show positive trends in N and P associated with eutrophication in large reservoirs such as Kremenchuk and Kiev. Nitrate distribution along the Don is shown in Figure 13.7, indicating an increase in nitrates

FIGURE 13.6 Dynamics of nitrogen and phosphorus content in the waters of Dnieper Reservoirs.

FIGURE 13.7 Spatial variability in nitrogen content along the Don River.

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PART | I Rivers of Europe

TABLE 13.3 Mean annual discharge and nutrient loads of the major Western Steppic rivers for the period 1997–2000 (Vishnevsky & Kosovets 2003) River Dniester Southern Bug Dnieper Donets

Station

Q (m3/s)

NH4 (tons/year)

NO3 (tons/year)

Ptot (tons/year)

Mogilev-Podolsk Pervomaisk Kherson Lisichansk

255 80 1550 104

2010 908 9287 1213

1287 4995 7821 6166

965 378 11 731 2197

because of eutrophication in reservoirs. Estimates of mean annual loads of N and P transported by the rivers of the steppe are summarized in Table 13.3.

13.5. AQUATIC AND RIPARIAN BIODIVERSITY 13.5.1. Phytoplankton, Zooplankton and Zoobenthos The abundance and composition of aquatic flora and fauna of the Dniester are associated with its relatively high current velocities and turbidity, and reflect the local characteristics of substrate, water temperature, and chemistry. The Carpathian area of the river is characterized by an extremely heterogeneous distribution of phytoplankton (Kuzko 1999). Near the source, the community is composed of only seven species of algae belonging to four systematic groups dominated by blue–green algae and diatoms with a total biomass of 0.032 g/L. The number of phytoplankton species and total biomass increases rapidly downstream, totalling 75 species at river-km 1100 in the lowlands. Phytoplankton diversity increases from the presence of Chlorococcales (52%, Actinastrum hantzschii, Scenedesmus acuminatus, Scenedesmus quadricauda), blue–greens (45%, Oscillatoria, Aphanizomenon), and euglenoids (Euglena, Phacus). Phytoplankton biomass here reaches 46.7 mg/L. Surveys in 1969 and 1995 indicate that total phytoplankton biomass has increased 10, mainly from a 42.3 increase in diatom biomass. In the lower river, phytoplankton comprise 102 taxa with a biomass of 1.62 g/m3. Zooplankton in the Dniester is represented by 79 species of rotifers, 13 species of copepods, and 14 species of cladocerans. The abundance of zooplankton is about 38 000/m3, corresponding to an average biomass of 445 mg/m3. Zooplankton is non-uniformly distributed along the river, being especially scarce in the middle reach because of high turbidity from clay-like substances. Zooplankton composition is dominated by Brachionus calyciflorus, B. angularis, B. bennini, Keratella cochlearis, and Polyarthra vulgaris (Romanenko et al. 1987). Zooplankton in Dubossary reservoir is richer relative to free-flowing parts of the river. In addition to species inhabiting flowing sections, reservoir communities include Asplanchna,

Synchaeta, Acanthocyclops americanus, Daphnia cucullata, and D. longispina. Zoobenthos in the mountainous area of the river is represented by lithoreophilic taxa dominated by chiromonids, stoneflies, caddisflies, and mayflies. The density of benthic fauna here is >9000/m2 with a biomass around 62 g/m2. In addition to species typical of lithoreophilic biocenosis, zoobenthos composition in the middle reach includes psammophilic taxa, particularly abundant are crypto-chironomids. The average density of psammophilic taxa is 1500/m2 with a biomass of 2.9 g/m2. Pelophilic biocenosis inhabit the silty sands and gravels and is represented by >120 taxa, mostly chironomids (4680/m2, 37.3 g/m2). The lower Dniester is colonized by zoobenthos inhabiting clay and silt substrates, comprising 79 taxa. The zoobenthos community is dominated by mayflies and mussels (Dreissena). Phytophilic biocenosis is represented by 137 taxa associated with pondweeds, reeds, and short-husk grasses (Romanenko et al. 1987). Phytoplankton in the Southern Bug is composed of 193 taxa, dominated by diatoms and green algae. Phyto-macrobenthos is represented by 118 taxa, mostly diatoms and blue– green algae. In the main river channel, phytoplankton is scarce and biomass is 4.1 g/m3. In stagnant waters of the river, filamentous green algae Cladophora, Sprirogira and Euteromorpha develop with substantial biomass (1.5–2 kg/ m2). In the lower river, phytoplankton richness decreases to 103 taxa dominated by diatoms and green algae with an average biomass of 1 g/m3. Zooplankton in the Southern Bug is represented by 72 taxonomic groups (Romanenko et al. 1987), dominated by rotifers. Copepods are limited both in species number and biomass. In pools, the composition is enriched by cladocerans. Average zooplankton biomass is 0.5 g/m3 in the middle reach of the river and decreases to 0.1 g/m3 in the lower river. Zooplankton development is high on river reaches with small dams (remnants of mills) with biomass increasing to 2–15 g/m3 during the warm season. The zoobenthic fauna of the Southern Bug is rich and diverse. Four major biocenoses are found, corresponding to stone, sand, clay, and silt riverbeds. The stony riverbeds of the upper and middle reaches of the river provide habitat for mollusks, caddisflies, and mayflies. Total biomass depends on the dominant species and hydraulic characteristics of the particular reach. High biomass of 5–9 kg/m2 has been reported for zebra mussels (Dreissena bugensis). Silt

Chapter | 13 Western Steppic Rivers

riverbeds in pools are less productive and characterized by a zoobenthic biomass of only 5–12 g/m2. Clay riverbeds are more diverse and productive, averaging 0.5 kg/m2 more biomass and 50 taxa dominated by Corophium robustum and Palengia longicauda. In the lower river (from Voznesenks to the mouth), silt riverbeds predominate with 139 species represented, mostly chiromonids, and biomass can be >1.5 kg/m2. Construction of the cascade of reservoirs along the Dnieper substantially altered conditions for phytoplankton development. Soon after construction of Kremenchuk reservoir, the phytoplankton was represented by 350 species decreasing to 260 species 20 years later. In contrast, the total biomass of phytoplankton increased 1.5–7 times, mainly because of blue–greens, diatoms and green algae. In total, the richness of phytoplankton in the river and reservoirs of the Dnieper is around 1192 species. The alga-flora of the upper river is dominated by phytoplankton from the large tributaries Prypiat and Desna. The abundance and composition of phytoplankton in Prypiat has changed over the past 30 years, following large-scale melioration actions on the catchment. The number and biomass of diatoms, blue–green and yellow–green algae decreased, whereas the number of chlorococs increased from 123 to 198 species. Zooplankton of the Dnieper and its reservoirs are diverse and includes about 1000 species of invertebrates, rotifers, polychaetes, crustaceans, and insects. The zooplankton of reservoirs are dominated by infusoria, rotifers, cladocerans, and copepods (Zimbalenskay et al. 1989). For instance, zooplankton in Kremenchuk reservoir is composed of 79 species of which rotifers comprise 47%, cladocerans 36% and copepods 17%. Zoobenthos in the Dnieper and its reservoirs includes around 800 species of invertebrates. Most diverse are the chironomids (120 species), testaceans (108 species), oligochaetes (82 species), and nemathods (56 species). Maximal zoobenthic diversity is found on silt–sand riverbeds where biomass ranges from 3.4 to 240 g/m2. One feature of longterm changes in zoobenthos composition is the spreading upstream of species characteristic of Liman-Caspian fauna (Zhukinskiy et al. 1989). Comparisons of surveys conducted 25 years ago with recent studies indicate that species of the Liman-Caspian fauna are now frequently found even in the tributaries Prypiat and Desna. Phytoplankton of the Donets is composed of 340 species of microscopic plants that includes 131 species of diatoms and 110 species of green algae, of which 78 belong to the family Protococcaceae. Average biomass varies along the river from 0.2 to 0.4 g/L and the maximum reported biomass was 6.7 g/L. Abundance and composition depend on season, annual hydrology, reach-specific hydraulic characteristics, and agricultural and industrial inputs. Diatoms typically dominate in winter and spring and seldom in summer, while Protococcus normally dominates in summer and autumn. Biomass and abundance of zooplankton in the Donets show considerable seasonal and longitudinal variability. In

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summer and autumn, zooplankton communities are dominated by rotifers (Brachionu rubens, Rotatoria) and by copepods (Daphnia) during winter and spring. The zoobenthos is diverse and abundant only in non-polluted reaches of the river. Ponto-Caspian species are represented in the middle reach of the river by 14 taxa, and 19 taxa were identified in the lower river. Dominant species are chironomids, oligochaetes, and bivalve mussels. Sand–silt riverbeds are the most productive habitats with abundances 1800/m2 and biomass of 40–100 g/m2 (Romanenko et al. 1987). In the Don, the phytoplankton communities are dominated by diatoms, green, and blue–green algae (Lysak 2002). Phytoplankton biomass typically ranges from 0.2 to 15 mg/ L, depending on annual hydrologic conditions. Systematic surveys indicate positive trends in both diversity and abundance. Composition of the phytoplankton in the lower river is composed of 214 species, and the most abundant are Chlorophyceae (46%), Cyanophycea and Diatomeae (16%). Biomass near the riverbanks is around 10 g/m3, and in the main channel varies from 0.3 to 18 g/m3. Composition of zooplankton in the Don is dominated by Rotatoria (47%), Cladocera (32%) and Copepoda (21%): Keratella quadrata, Bosmina longirostritis, and Heterocope caspia are the most widespread (Shevlyakova 2002). Their abundance ranges from 600 to 190 000/m3 and biomass from 9.4 to 748 mg/m3. In the lower river, the zooplankton communities comprise 97 species with an average biomass of 0.8 g/m3. Zoobenthos in the upper Don comprises 120 species, including 50 species of chironomids and 30 mussels (Gorelov 2000, 2002). In the upper river, mussel zoobenthos is dominated by Viviparus viviparous, and Unium and Polypedium scalaenum are common in the lower river. In the lower river, the zoobenthic community is represented by 57 species, dominated by Chironomus plumus, Procladius ferrugineus, Dreissena polimorpha, and Lithoglyphus naticolides. In Tsymlyansk Reservoir, zoobenthos biomass varies from 230 to 875 g/m2 (Gorelov 2002). The composition and spatial distribution of phytoplankton in the Kuban partially resembles that of mountain part of the Dnister, whereas the lower section of the river is similar in phytoplankton composition to that of the lower Don. Surveys have shown that in the upper catchment (near Nevinomisk), phytoplankton communities were represented by 24 species belonging to 3 systematic groups dominated by diatoms (Bacillariophyta), and green algae (Clorophyta). Abundance and diversity of phytoplankton increase downstream and especially in the Kuban delta with >200 species being documented. Zooplankton are non-uniformly distributed along the river and are especially scarce in the middle section because of increased turbidity, being dominated by rotifers and copepods. Zoobenthos in the mountainous section of the river are dominated by lithoreophilic taxa (chironomids, stoneflies, caddisflies, mayflies). Downstream of Nevinomisk, the zoobenthos changes to psammophilic taxa, and in the Kuban delta by pelophilic taxa.

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13.5.2. Fish Fauna, Amphibians and Mammals Ichthyofauna of the mountain region of the Dniester consists of 41 species, dominated by trout (Salmo trutta lacustris), barbell (Barbus barbus), and chub (Leuciscus cephalus). The commercial value of these fish is low and mainly an interest to sport anglers. In the middle Dniester, ichthyofauna constitutes 42 species belonging to 8 families. A total of 51 species in 12 families comprise the fish fauna of the lower river, most common are carp (Carassius gibelio), roach (Rutilus rutilus), and gudgeon (Gobio gobio). From the total of 57 species, 5 species are at or near extinction: pearl roach (Rutilus frisii), ide (Leuciscus idus), dnieper barbel (Barbus barbus borysthenicus), burbot (Lota lota) and zingel (Zingel zingel). Nine species (21.4% of the total number) have commercial value in the middle reach, and 12 species (23.5%) have commercial value in the lower river (Usatii 2004). The ichthyofaunae of the Dniester have experienced substantial declines during the last 50 years, as surveys completed in 1948–1949 reported 75 species. After construction of Dubossary dam, sturgeons and many species of semi-migratory fish were lost from the river. Reservoir construction also affected the thermal regime of the river (Dolgy 1993; Usatii 2004). The ichthyofauna of the Southern Bug and Dnieper rivers are quite similar, corresponding to their geographical positions and similarities in geomorphology, climate and land use. Both rivers also flow into the Dnieper-Bug Liman, allowing transitory fish to migrate from one river to the other. As such, a distinction should be made between the DnieperBug Liman and the middle and upper segments of the Southern Bug and Dnieper. Ichthyofauna in the Dnieper-Bug Liman is represented by 69 species. This fauna differs from the upstream segments by the presence of species in the family Clupeidae (Alosa caspia, Alosa pontica, Sprattus sprattus, Clupeonella delicatula) entering the Liman from the Black Sea where they are a valuable commercial fishery. The family Gobiidae (Neogobius kessleri, Neogobius fluviatilis, Neogobius gymnotrachelus) is widely represented by 15 species, and is also an important commercial fishery. The ichthyofauna of the Dnieper-Bug Liman lacks some fish species that are abundant in upper river systems (Zimbalenskay et al. 1989; Zhukinskiy et al. 1989), such as the Dnieper barbel (Barbus barbus borysthenicus) and burbot (L. lota); the latter is a valuable commercial fishery in the river upstream of Zaporizhzhe dam. Ichthyofauna of the Southern Bug, including the Liman section, consist of 52 species, although decreasing to 42 in the middle reach of the river, downstream of the city Pervomaysk (Ambros 1956; Romanenko et al. 1987). In the lower river, vyrezub (R. frisii), danubian bleak (Chalcalburnus chalcoides), and zander (Lucioperca lucioperca are abundant and represent a commercial fishery. Upstream migration for many species is limited by the numerous rapids between Pervomaysk and Voznesensk and by the dam near the village of Alexandrovka. In 2006, construction of another

PART | I Rivers of Europe

large dam (South-Ukranian power station) was completed and a large reservoir has appeared. It is expected that the reservoir will alter the thermal regime downstream. Because of narrow floodplains and no space for constructing fish impoundments, a commercial fishery has not developed in the middle and upper Southern Bug (Romanenko et al. 1987). Little is known about the ichthyofauna in the upper Southern Bug (upstream of Pervomaysk). The Dnieper, including the Liman area, presently provides habitat for 53 fish species (Ambros 1956; Zhukinskiy et al. 1989). Before construction of the cascade of large dams and reservoirs, ichthyofauna of the river comprised 58 species. Transitory fishes, beluga (Huso huso ponticus), sturgeons (Acipenser nudiventris, Acipenser colchicus, Acipenser stellatus), shads (Caspialosa kessleri pontica) were lost in the middle and upper segments of the river after construction. Because of abrupt decreases in current velocity and increases in water depth, many rheophilic fish species (barbel, nase, dace and ide) significantly decreased and some limnophilic fish species (bream, carp, roach, perch and zander) increased in abundance in the reservoirs. Half of the rheophilic species are rare. There were also actions taken to increase the commercial productivity of the reservoirs by introducing new species such as bighead carp (Aristichthys nobilis), silver carp (Hypophthalmichthys molitrix), and white-amure (Ctenopharyngodon idella). At present, the ichthyofauna in reservoirs are dominated by Cyprinidae (28 species), Gobidae (8 species), and Percidae (6 species). Approximately 13 species have no commercial value (e.g. stickleback, loach, spined loach Cobitis taenia, Black Sea chub Leuciscus borysthenicus). Although 43 species have commercial value (carps, roaches, pikes), many are rare in the reservoirs (sterlet, Black Sea shad, Dnieper barbell, vimba) and only 23 species are commercially fished (Black Sea and Azov sprat, bighead carp, silver carp, white-amure, pike, sheat, zander, perch). From 1966 to 1980, the average annual commercial catch in the Dnieper reservoirs was 19 224 tons with 50% of the catch being cyprinids. For comparison, the annual commercial catch in the Dnieper before reservoir construction ranged from 5000 to 6000 tons and carps contributed 20% of the catch. Longterm observations indicate a systematic decrease in the productivity of the reservoirs, with catches from 1976 to 1980 being 1.3 less than the previous five years. The main reasons explaining the decrease in productivity and reduction in commercial catch volume are the adverse conditions for fish spawning such as large and abrupt daily variation in water levels, absence of submerged shallow grasslands, and poor water quality. In the Donets, the fish fauna is represented by 44 species (Romanenko et al. 1987). The ichthyofauna is typical of many rivers of the Azov and Black Sea basins. Most abundant are white bream (Blicca bjoerkna), blue brim, roach, tench (Tinca tinca), perch, chub and pike. The abundance of ichthyofauna has significantly declined over the past 30 years because of poor water quality (industrial sewage and

Chapter | 13 Western Steppic Rivers

accidental oil spills), and poor regulation of commercial and non-commercial fisheries. However, there has been a trend of improvement in recent years with establishment of stricter fishery regulations and introduction of commercially valuable species. Fish faunae of the Don are diverse and, including the estuary of Taganrog Bay in Azov Sea, are composed of 73 species (Tuneakov 1984; Delitsyn 2001; Reshetnikov 2003). Of that number, 64 species are native, 6 were introduced to increase the productivity of the river and its reservoirs, and 3 species were introduced occasionally. Native species include 16 families each containing from 5 to 26 species. Maximal abundance, 44.6% of the total number of native species, is found in the Cyprinidae (26 species). The family Gobiidae (12.5%) is represented by eight species, Percidae (9.4%) by six species, and Acipenseridae and Cobitidae (7.8%) by five species. Carp are not only the most diverse but they comprise the major part of fish stock and commercial catches. Carps inhabit a wide spectrum of ecological niches, being found in the main channel, floodplain impoundments, inundated areas, and lakes. The Cyprinidae: bream, common carp, ziege (Pelecus cultratus), roach, blue and white bream have commercial value. Of the other families, the most widespread are zander, Volga zander (bersh Stizostedion volgenese), sheat, and perch. Introduced species are most commonly represented by bighead carp (A. nobilis) and silver carp (H. molitrix). Both used as a commercial fishery with catches in 2002–2004 from 800 to 1100 tons per year (Mamontov et al. 2005). The most diverse fish faunae are in the upper Don and Tsimlyansk reservoir (Bandura et al. 2000). However, 16 migratory species in the upper and middle segments of the river are absent because of the large dams, and 5 species are absent in the lower Don. The fish faunae of small tributaries of the Don are not diverse, usually represented by 10–15 or fewer species. There also has been a trend of decline here in the past 20 years. The abundance of valuable fishes has significantly declined because of reservoir construction, water abstraction for irrigation and transport and intensive commercial fishing. These changes in the river were particularly harsh for transitory fishes that feed in the Azov Sea and spawn in the river and its tributaries. For instance, star sturgeon (A. stellatus), beluga (Huso huso), and Azov shad (A. pontica) have disappeared in the middle and upper segments of the Don and ship sturgeon (A. nudiventris) and sea trout (Salmo trutta) are extinct. The catchment of the Don has been historically an important fishery region of Russia. In addition to the commercial fishery in the river, tributaries, and reservoirs, there are numerous impoundments on the river used for fish farming and aquaculture (Volovik & Chikhachev 1998). In the Kuban and its delta, the fish faunae are composed of 74 species belonging to 19 families containing 1–35 species of which 61 species are native, and 13 were introduced to increase the productivity of the river and reservoirs (Troitski & Tsunikova 1988; Reshetnikov 2003). Although

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there are certain similarities between the Don and Kuban, peculiarities in the ichthyofauna reflect some distinctive features in geological evolution. Indeed, the fish composition of the Kuban more closely resembles the ichthyofauna of the Terek and the Kuma rivers. It lacks characteristic species such as vyrezub (R. frisii), two species of Cyprinidae (Leuciscus leuciscus, Leuciscus danilewski), whitefin gobi (Gobio albipinatus), and burbot (L. lota). On the other hand, the ichthyofauna of the Kuban includes species absent in the Don such as barbel (Barbus tauricus kubanicum), bekas (Leuciscus aphipsi), and Black sea chub (L. borysthenicus). Although the Kuban River with its delta represents a large freshwater system with valuable potential for commercial fishery, commercial catches on the watershed are low, for example only 151 000 tons in 1990. Most of the commercial catches (up to 50%) were represented by fish in the Cyprinidae family: common carp, bream, silver carp (H. molitrix). Catches of previously traditional species such as roach (Rutilus rutilus), vimba (Vimba vimba) were so severely reduced they practically lost commercial value. Commercial catches of Acipenseridae indicate significant reductions from 259.9 tons in 1998 to only 13.8 tons in 2001 (Lure et al. 2005). Factors contributing to the reduction in Kuban fish abundance and composition are large reservoirs (Krasnodar reservoir) preventing fish migration and transforming the flow regime of the river, along with severe pollution by oil compounds and metals. Long-term records of commercial catches for the Dniester and Dnieper are shown in Figure 13.8, indicating a

FIGURE 13.8 Long-term records in commercial fish catches in the reservoirs of the Dniester and Dnieper Rivers.

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significant reduction of carp in catches on the Dniester River after construction of Dubossary reservoir. The reduction can most probably be attributed to changes in thermal regime and high variation in water level that affected primary spawning areas on the river (Usatii 2004). At the same time, increases in commercial catches of sprat and roach have occurred in the reservoirs of the Dnieper River. Reservoirs on the Dnieper inundated large areas of floodplains that provided favourable conditions for these species. Approximately 19 species of amphibians inhabit the watersheds of rivers of the Western Steppe. They are represented by the following major groups: toads (5), frogs (7), and salamanders (7). Most abundant are the pool frog (Rana lessonae), common frog (Rana temporaria), and common toad (Bufo bufo). Most salamanders inhabit the upper and middle segments of the rivers and are rare in the lower reaches. There has been a general decline in the number and abundance of species, and a reduction of inhabited areas due to degradation and contamination. For example, the firebellied toad population has declined 7–13 times during 1980–1986 in the Don and Donets catchments. Some species of terrestrial and aquatic turtles inhabit southern downstream parts of steppic rivers. Grass snakes (Natrix natrix) are widespread and are found in every river, reservoir, and impoundment. Venomous snakes are represented by adders (Vipera renardi, Vipera berus). River floodplains (Plavni) provide a migration and wintering habitat for about 340 species of birds, of which 100 species also breed. Mammals are represented by 15 species of hunting value, including wild hogs, roe deer, otter, badger, and marten. During the past 10–20 years, some new mammals have been introduced (muskrat, raccoon), while others have become extinct (steppe polecat, wolf).

13.6. MANAGEMENT AND CONSERVATION 13.6.1. Economic Importance Rivers of the Western Steppe have always played a crucial role in the economics of the region and were especially valuable for Slavic settlements along the rivers for fishery, and commercial and military navigation. Navigation was one of the major water resource uses up to the middle of the last century when water resources of the region were exploited for production of electric power, irrigation, and industry (Sokolov 1952). Before construction of Dubossary dam, the Dniester was navigable up to the middle section. At present, navigation is conducted only on the lower 1/3 of the river and mainly for local needs of transporting excavated river deposits (sand/pebbles) to railway terminals. A limited number of cruise ships is used for tourism. There are two large reservoirs on the Dniester: the Dniester reservoir built from 1979 to 1981 near Novodnestrovsk

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(river-km 678), and Dubossary reservoir built from 1954 to 1956 near the city of Dubossary (river-km 360). Dams of the reservoirs are 58 and 23-m high, respectively (Ganay 1990). Backwaters of the reservoirs spread 205 km upstream of Dniester reservoir and almost 128 km upstream of Dubossary reservoir. Maximal volumes of the reservoirs are 3 and 0.49 km3, respectively, with surface areas of 140.8 and 67.5 km2, respectively. About 30% of Dubossary reservoir is already filled by deposited sediments because it intercepts 95% of the rivers solid discharge. After construction of the Dniester reservoir, sediment deposition in Dubossary was significantly reduced. Downstream of Dubossary dam, the riverbed was incised on average 80 cm into the loose alluvium. Besides production of electricity, the dams and reservoirs provide flood control and regulation of water discharge and level. Flood control is also enhanced by the construction of levies along both banks on wide parts of the river floodplain. Levies about 5-m high separate the floodplain used for cropping vegetables, and gardening. A commercial fishery has developed on the lower river, especially in the area of Turunchuk Plavni. Because of numerous rapids, the Southern Bug was never used for commercial navigation. However, it was one of the first rivers of the region that experienced intense pressure of river management. In the 17th century, Germans settled along the river and created 70 small milldams (Kaganer et al. 1969). In the second quarter of the last century, these milldams and small impoundments were supplemented with small electric plants. Although most of the dams were 2–3-m high and located in rapids, the cumulative effect on river regulation was substantial. Flood control was generally of minor concern on the river because of its narrow valley and floodplain; inundated areas are local and usually remote from settlements, and important agricultural and industrial areas. Production of power and use of the river gained a new focus after construction of Tashalyks hydro-nuclear power plant and the creation of a cooling reservoir in the area of socalled Basalt Steppe Pobuzhe is completed. A result of this construction will be a large submerged area that significantly reduces the area of original steppic biocenoses and a unique area of white-water tourism. Construction of this large dam will dramatically change the ecology of the lower river due to alterations in thermal regime, and transport of particulate and dissolved matter. The building of the dam was postponed many times during the past 25 years as argued by ecological organizations. However, as often happens, economics prevailed over ecological reasoning and filling of the reservoir began in 2006. The Dnieper was one of most important commercial waterways in ancient Europe, being a part of the merchants trail from Scandinavia to Greece. Although the river was navigable for vessels similar to the Vikings Drakkars, there were always difficulties to pass Dnieper Rapids (Gumilev 1989). Besides the direct danger imposed by the Dnieper Rapids for vessels, the area near the rapids was frequently used for ambushing merchant

Chapter | 13 Western Steppic Rivers

caravans by steppe nomads. Because of complexity of navigation, the river lost its value as a commercial waterway in Russia. After conquering the Azov steppe, the Don provided a conventional waterway from Central Russia to the Black Sea (Kluchevsky 2000). In the first quarter of the last century, the Dnieper began to be heavily exploited for electrical production. With the construction of the 45-m high Dnieprovsk dam during 1927–1932, Dnieprovsk reservoir at 3.32 km3 in volume and 130 km in length was created and flooded the rapids (Vishnevsky 2000; Vishnevsky & Kosovets 2003). Dnieprovsk dam was the largest European hydroelectric power station at that time (560 MWt). During 1950–1970, a cascade of 5 more large reservoirs and dams was created upstream and downstream of Dnieprovsk dam: Kahovsk reservoir in 1955–1956 (18.2 km3, 230 km long), Dnieprodzerzhinsk reservoir (1956–1962, 2.46 km3, 114 km), Kremenchuck reservoir (1956–1962, 13.5 km3, 149 km), Kiev reservoir (1964– 1966, 3.73 km3, 110 km), and Kanivsk reservoir (1972– 1976, 2.5 km3, 123 km). The total volume of the reservoir cascade is 43.7 km3, producing on average 9–11 billion kWt per year that supply the metallurgical and heavy machinery industries in the region. Dams of the cascade were supplied with sluices to aid navigation that gained a new perspective for the river. Waters of the river also are intensively used for irrigation of semi-arid areas in the southern steppe, and many of the reservoirs were primarily designed for irrigation purposes (e.g. Kahovsk, Kremenchuck). A system of canals transfers water of the Dnieper east to the Donets to supply industry in the Donbas region. Water in the reservoirs is presently used intensively for commercial fishery, and the annual catch in the cascade average about 18 000 tons (Romanenko et al. 1987). Although the Donets is in a region where the demands for water resources are extremely high, the river cannot supply the water in the required quantity or quality. Nevertheless, approximately 51% of the water taken from the river each year is used for drinking water, 41% is consumed by industry, and 8% for irrigation and agricultural needs. Commercial navigation is not developed on the river. There are two relatively large reservoirs controlling the hydrologic regime of the river: the 0.38 km3 Pecheneg reservoir at river-km 843, and the 0.11 km3 Shyastinsk reservoir at river-km 337. Because water resources of the river are limited and insufficient to supply industry, an external water supply was developed through a system of transfer canals from the Dnieper and Don. In 1954, the Donets–Donetsk canal was created to transfer 73 million m3/year for drinking water from artesian ground waters for the industrial center Donetsk. The Donets– Donbas canal was created in 1959 and is capable of transferring up to 1106 million m3/year, and the Dnieper–Kharkov canal built in 1985 transfers 23.9 million m3/year. Commercial fishery on the river is relatively small and is more developed where a system of small impoundments on tributaries of the river houses numerous fish farms (Romanenko et al. 1987).

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In the times of Ancient Russia, the Don functioned as a frontier line between Slavs and steppic nomads. Intensive exploration of its steppic downstream area began in the 18th century when the Don was used for navigation of the first Russian flit built in Voronezh by the decree of the Russian tsar Peter the Great (Kluchevsky 2000). However, commercial navigation was relatively small and significantly increased with construction in 1950 of the Volgo–Don canal system and Tsimlyansk reservoir that improved navigability on the lower river. The Volgo–Don canal is 101 km long, supplied with 13 sluices, 3 pumping stations, and 13 dams. The canal connects commercial navigation between the Caspian, Azov and Black Seas. Tsimlyansk reservoir is a large reservoir sometimes called the Tsimlyansk Sea with a total volume of 23.9 km3 and length of 260 km. Water of the river is used for electrical production and abstracted for irrigation of the arid steppe. Although the energetic resources of mountain rivers in the Kuban catchment are estimated at 2.44 million KWt/h, only a small portion (5–7%) of those resources is currently used (Lure et al. 2005). Electro-energy is produced mainly from small hydroelectric plants on tributaries (Big Zelenchuk, Urup, Laba, Belaya) with the total power production 58 000 million kWt/h. During the last decade, construction of Zelenchuk hydropower plant began with a planned productivity of 320 MWt. A large reservoir was constructed on the Kuban River upstream of Krasnodar in 1975. The dam of the reservoir is 22 m high and 11 km long. Backwaters of the reservoir spread 46 km upstream forming a storage volume of 3.1 billion cubic meters of water. The reservoir was created to achieve two principal goals: to prevent catastrophic floods and to enhance agricultural potential of the region. Presently the Kuban region is a major rice producer in Russia. More than 400 000 tons of rice is produce annually. Waters of Krasnodar reservoir permit irrigation of about 270 000 hectares of land, of which 248 000 is used for rice. The catchment of the Kuban serves as a valuable agricultural region of Russia, specializing in production of wheat, corn, rice, sugarbeet, and vegetables. The volume of water intake for agriculture is 3120.3 million m3 (2001) and was 73% of the total water intake. Although over the past decade, the area of land used for agriculture in the region was reduced almost twofold, the annual consumption of water has changed relatively little suggesting irrational use of water resources (Lure et al. 2005). The Kuban is navigable from the delta upstream to UstLabinsk. The total length of the waterway on the river is 445 km. Navigability of the river is supported by locks on the Krasnodar and Fedorov hydrosystems. Commercial navigation began in 1861 and presently the flit of the Kuban River Steamship company includes 160 vessels that annually transported in late 1980s 10–11 million tons of cargo and 130 000 passengers. Over the past decade, navigation on the Kuban suffered a significant decline because of the general reduction in economy and now cargo transport is only 0.5 million tons per year.

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13.6.2. Conservation and Restoration A peculiar feature of pristine steppe lands is that once disturbed, for example by plowing, they can never be restored. Recognition of this fact near the end of the 19th caused the establishment in 1898 of the Askania-Nova biosphere reserve, 33 520 E 46 270 N (Krutyporokh & Treus 1967). Presently, this soil biosphere encompasses around 11 000 ha of pristine steppe land covered with feather-grass, a park (200 ha) with 150 species of shrubs and trees, and a zoo housing a unique collection of steppe animals and birds, including the Asian wild horse (Equus przewalskii). The reserve also has a biological station with a restoration program for native species such as aurochs (Bos primigenius) and even introduced species from regions with similar environmental conditions such as Asian seiga, American bison and Belorussian wisents. Another large biosphere reserve lies near the city Golay Pristan. The 89 100 ha reserve was established in 1927 with the goal of conserving the Black Sea steppe landscape of feather-grass lands inhabited by migratory birds. A natural reserve of feather-grassed steppe, Elantsk Steppe (1680 ha), was established in the Southern Bug catchment in 1996. A set of natural reserves was established in the area of forested steppe and the Polesse to preserve deciduous woods and swamps. The Polesse natural reserve was established in 1968 in Zhitomir region and occupies 20 100 ha of sphagnum and sedge-sphagnum bogs. The Kanev natural reserve established in 1923 protects 2000 ha of forested steppe. In the past decade, the Rovenski natural reserve (47 000 ha) and Dnieper–Orelsk (3800 ha) were established. Rovenski natural reserve conserves mesotrophic sedge-sphagnum bogs and swamp birch and alder woods, whereas Dnieper–Orelsk reserve is meant to restore hornbeam, oak, and ash-tree forests in the Dniepropetrovsk region of Ukraine. Besides the network of scientific and natural reserves, there are many national parks and natural monuments. The most famous parks in the Dnieper catchment are Sophia Park in Uman (since 1796), Fomichev botanic park in Kiev, Shatski Lakes (49 000 ha), and Desneano–Starogutin park (16 300 ha). The protected area of catchments with steppic rivers in Ukraine comprises 1.5% of its land area. In the catchment of the Kuban and its tributaries are two large biosphere reserves: Teberda State Biosphere Reserve (since 1936, 85 064 ha), and Caucasus State Biosphere Reserve (since 1924, 280 335 ha). The flora of Teberda reserve consists of 1260 species of which 235 are represented by Caucasus endemic species. In the Caucasus Reserve, the flora is represented by >3000 species, including diverse species of alpine meadows (900 species). Diverse populations of ferns (40 species), orchids (>30 species), and rhododendrons (5 species) make a distinctive feature of the flora. Unique fauna of the reserves includes 89 species of mammals, 248 bird species, 15 species of reptiles, and more than 10 000 species of insects.

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In catchments with steppic rivers in the Republic of Moldova exist five scientific reserves (19 300 ha), 130 natural monuments (2900 ha), 63 natural reserves (8000 ha), and 41 protected landscapes (34 200 ha). The Kodru reserve was created to preserve forests typical of Central Europe in western Moldova. Dominant species are Quercus petraea, Quercus robur, and Fagus silvatica. The flora of the reserve includes about 1000 species of plants, and 203 species of terrestrial vertebrates of which 17 species are considered extinct. The Yagorlyk reserve was established with the purpose to conserve steppe landscapes and biocenoses in the Dniester catchment, comprising 719 vascular plants, and 158 vertebrates including 122 birds. In the Dniester catchment, wetlands are mainly represented by floodplain swamps at the confluences of tributaries (Yagorlyk, Trostyanets, Kuchurgan) and marshes at the Dniester mouth. There are eight Ramsar wetlands in the Dniester catchment, including four located directly on the river: Bakotska Bay (48 350 N, 26 560 E, 1590 ha), Lower Dniester (46 340 N, 29 490 E, 60 000 ha), Dniester–Turunchuk area (46 280 N, 30 360 E, 76 000 ha), and the Northern Dniester Liman (46 220 N, 30 120 E, 20 000 ha). Bakotska Bay was created in 1976 as a result of reservoir construction. Wetlands in catchments with steppic rivers in Ukraine (14 total) on the Ramsar list are mainly Sub-Carpathian swamps and lakes, Ukranian Polesse bogs and lakes, and Liman and swamp floodplains in the lower reaches of the rivers. Half of these are in the Dnieper catchment: Desna River Floodplains (52 190 N, 33 230 E, 4270 ha), Polesse Mires (51 310 N, 28 010 E, 2150 ha), Prypiat River Floodplains (51 480 N, 25 150 E, 12 000 ha), Shatsk Lakes (51 310 N, 23 500 E, 21 000 ha), Dnieper–Oril Floodplains (48 320 N, 34 450 E, 2560 ha), Obytochna Spi and Obytochna Bay (46 350 N, 36 120 E, 2000 ha), and Dnieper River Delta (46 340 N, 32 290 E, 26 000 ha). In the Don and its tributary the Donets catchments are found 3 Ramsar sites: Bilosaraiska Bay (46 540 N, 37 200 E, 2000 ha), Kryva Bay (47 030 N, 38 080 E, 1400 ha), and Veselovskoye Reservoir (46 550 N, 41 020 E, 309 000 ha). The Kuban delta, particularly the group of Limans between rivers Kuban and Protoka, is included in the list of Ramsar sites (45 300 N, 37 480 E, 88 400 ha).

13.6.3. Catchment Master Plans Catchments of the Western Steppe occupy four countries of the former Soviet Union. Although formally functioning as international unifications, the countries are in reality independent states with their own environmental regulations and policies. For some of these countries, for example Ukraine and Moldova, integration into the European Union represents a distant strategic goal, and officials are trying to shape environmental legislation in accordance with EU environmental directives. Although in many respects the Water Codes of the countries show correspondence with the European Union Water Framework Directive, major changes and

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Chapter | 13 Western Steppic Rivers

alterations are still necessary. For instance, the Ukranian Parliament is considering adopting a basin management approach, and basin management is now in a test phase in the Dnieper catchment. Principal legislation for the water sector in Moldova is the 1993 Water and Underground Resource Codes that requires all water users to obtain environmental licenses for water use and discharge. The water sector is governed within the institutional framework of the Department of Environmental Protection, the Hydrometeorological Services, and the National Institute for Ecology. Moldova has ratified the ECE Convention on the Protection and Use of Transboundary Watercourses and International Lakes, and established agreements with Ukraine on water management in the Dniester catchment. Priorities for improving water resources management include strengthening institutional capacity in water resources planning and management, improving coordination between various agencies to promote river basin management, promoting environmentally harmless agricultural practices, improving management of groundwater resources, and adjustment of legislation in accordance with the European Union. In Ukraine, water resource legislation is regulated by the Law on Environmental Protection (1991) and the Water Code (1995). Legislation states that ground and surface waters can be allocated for use only in accordance with an ecological approach to water quality management. The use or discharge of water requires a permission of 3–25 years in duration, specifying the volume of the water in use and amount of contaminants to be discharged. Water management is governed by the Ministry of Environmental Protection and Nuclear Safety, the Ministry of Health Protection, and the Committee of Water Resources, Geology, and Hydrometeorology. The water resource management functions on an institutional framework basis, but lacks clear delineation of responsibilities between the various agencies. Under the UNDP/GEF Dnieper Basin Environmental Program Project, Ukraine, Belarus, and the Russian Federation have been working towards establishing a framework for river basin management of the Dnieper. Presently, priority topics of water management in Ukraine include improvements of the hydrological regime of rivers and their watersheds, improvement of the existing institutional framework, and development of a basis for conversion to the river basin framework. The Water Law (1993) and Water Code (1995) formulate the principles and policy directions for water resources management in the Russian Federation. Legislation is established on the principle of state ownership for all natural waters and water bodies and their associated water management structures, and regulates the payments for water usage and pollution. As in other former soviet countries, the framework for management of surface and ground waters is institutional and governed by the Ministry of Natural Resources and Environmental Protection, operating through 17 River Basin Agencies in coordination with the State Committee on

Hydrometeorology and Environmental Monitoring. Water relations with neighbouring states are regulated on the basis of cooperative agreements between states in the management and conservation of transboundary waters, including international conventions. Priority topics in the water sector include implementation of integrated water basin management and strengthening of water quantity and quality monitoring systems, establishing new water pricing structures, taking into account affordability constraints, updating of current standards for quality water bodies, drinking water and wastewater discharges, reducing pollution discharges from industry, and reassessing the operating rules of weirs, particularly in the allocation of spring flows for fish spawning.

13.7. CONCLUSIONS AND PERSPECTIVES Rivers of the Western Steppe drain a large area north of the Black and Azov Seas. Although catchments of the rivers occupying the territory have diverse geomorphologic, climatic, biologic, and economic conditions, the middle and lower segments of the rivers flow through East European forested steppe and Pontic steppe. A basic geographic feature of the region is vast lowland landscapes separated by low hills and intersected by wide river valleys. The river valleys were developed by paleo-flows and substantially exceed the dimensions of contemporary river channels, thereby providing broad floodplains today. The rivers flow southeast from the Carpathian Mountains to the west (Dniester) and from the Valday Hills to the north (Dnieper and Don), and their respective hydrology’s originate from processes in the upper areas of each catchment. The fertile steppe soils are favourable for agriculture, but the semi-arid and arid climate limits cultivation of many agricultural products without irrigation. As such, agricultural exploration of the Eastern Steppe began relatively recently compared to Western and Central Europe. Nevertheless, rates of development were so high during the past 150 years that most pristine soils of the steppe were converted to agriculture. Even harsher pressure on the steppe environment was imposed by industrial development. Large rivers, first the Dnieper, were impacted by a cascade of dams that transformed the middle and lower segments of the rivers into a series of reservoirs. Ground and surface waters were seriously affected by coal mining in the Donbas region, and sewage discharge and accidental spills of toxic contaminants (Dniester and Prypiat rivers). During the industrial revolution, focus on rivers was set on the demands of industry and agriculture, and numerous ecological problems, unfortunately, received little or even no attention. As a result, river and terrestrial ecosystems of the Western Steppe have suffered significant declines. Plowing of pristine steppe lands caused major changes in the flora and fauna of the steppe. Construction of dams altered hydrodynamic and thermo regimes of the rivers, intercepted bedload transport, and dramatically affected the composition and

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abundance of phyto-, zooplankton, benthic invertebrates, and ichthyofauna. Although a growing awareness about ecological problems caused government and other agencies to implement conservation and protection measures of water resources and aquatic ecosystems, they presently do not meet the scale of ecological biodegradation. Economic considerations still dominate decision-making regarding the construction of new engineering complexes. For example, the Ukrainian government decided to continue construction of the Tashalyks hydro-nuclear power station and the large reservoir on the Southern Bug that will cause dramatic ecosystem changes downstream and seriously impact the terrestrial ecosystem of the Basalt Steppe Pobuzhe. The decision for this construction was postponed for more than 25 years, mainly because of the efforts from ecological organizations. At the same time, there are some clear positive changes in the organization of water resources management in the region, particularly the progressively increasing degree of water quality monitoring, hydro-biological monitoring, and regulation of water consumption and wastewater discharge. These measures, together with growing level of environmental education, demonstrates the growing perspective for the preservation and improvement of river ecosystems of the Western Steppe from those expressed even less than a decade ago.

Acknowledgements Professor G.M. Lavrentyeva and Dr. V. Yu. Georgievsky provided valuable materials for the chapter. The authors acknowledge the great help from N.I. Katolikova and M.I. Eremin who compiled the data and prepared illustrations for the Don River. Dr. Yu. A. Rebriev, I. Sirenko, S. Zatsarinniy, V. Rusu, and G. Syrodoev kindly provided photographs of river reaches. V. Gorbenko is thanked for arranging a field trip along the Kuban River. Professor G. N€ utzmann is thanked for the friendly encouragement and permanent support. A. Sukhodolov and N. Loboda appreciate the financial support provided by the Security Through Science Programme of NATO (ESP.NR.EV 982416). N. Arnaut acknowledges the financial support provided by budget program of the Institute of Freshwater Ecology and Inland Fisheries, Berlin.

REFERENCES Alekseev, M.N. 1996. Possible “Cromerian Complex” equivalent sequences in the Russian Plain. In: Turner, C. (ed). The Early Middle Pleistocene in Europe, Balkema, Rotterdam, pp. 273–277. Alymov, A.N. et al. (ed). 1978. Atlas of Nature and Natural Resources of UkSSR, Department Geography of the Geodesy and Cartography Section of the Council of Ministers of USSR, Moscow. Ambros, A.I. 1956. Ichthyofauna of the Dnieper, Southern Bug Rivers and Dniepro-Bug Liman. Ukrainian Academy of Sciences, Kiev. Anuchin, V. 1956. Geography of the Soviet Carpathians. Nauka, Moscow.

PART | I Rivers of Europe

Babichenko, V.N. 1984. Climate. Nature of Ukranian SSR. Naukova Dumka, Kiev. Bandura, V.I., Archipov, E.M, and Yakovlev S.V. 2000. Composition of ichthyofauna of Tsimlyansk Reservoir. In: Biodiversity of Water Ecosystems of South-East Europian Russia. Volgograd, pp. 66–74. Borysova, O., Kondakov, A., Paleari, S., Rautalahti-Miettinen, E., Stolberg, F., and Daler, D. 2005. Eutrophication in the Black Sea region: Impact Assessment and Casual Chain Analysis. University of Kalmar, Kalmar, Sweden. Delitsyn, V.V. 2001. New list of ichthyofauna of reservoirs on the Don watershed. Proceedings of Voronezh State University,Voronezh, pp. 20–26. Dolgy, V.N. 1993. Ichthyofauna of the Watersheds of the Dniester and Prut Rivers. Shtiintsa, Kishinev. Fashuk, D.Ya. 1998. The estimate of antropogene load on the watersheds of Black and Azov Seas. Water Resources RAN 25(6): 694–711. Ganay, I.M. (ed). 1990. Ecosystem of Lower Dniester Under Increased Antropogene Influence, Shtiintsa, Kishinev. Glushko, V.V., and Kruglov, S.S. 1971. Geological Structure and Natural Fuel Resources of Ukrainian Carpathians. Nedra, Moscow. Golobutsky, V.O. 1970. Economic History of Ukranian SSR. High School, Kiev. Gorelov, V.P. 2000. Hydrobiological regime of the southern part of the upper Don. In: Biodiversity of Aquatic Ecosystems of Southern-East European Part of Russia. I. Volgograd, pp. 87–103. Gorelov, V.P. 2002. The state of benthic fish-feeding resources in Tsymlyansk Reservoir (1998–1999). In: Contemporary Studies in Fishery of the Volgo-Don Basins. 50-Ubileum Issue. State Institute of Fishery Conservation, Moscow, pp. 53–56. Gumilev, L.N. 1989. Ancient Rus and the Great Steppe. Mysl, Moscow. Kaganer, M.S. et al. (ed). 1967. Resources of Surface Waters of USSR. Western Ukrainian and Moldavia. Vol. 6(3), Hydrometeoizdat, Leningrad. Kaganer M.S. et al. (ed). 1969. Resources of Surface Waters of USSR. Ukraine and Moldavia. Vol. 6(1), Hydrometeoizdat, Leningrad. Kluchevsky, V.O. 2000. Russian History. Phoenix, Rostov-on-Don. Krutyporokh, F.I., and Treus, V.D. 1967. Askania Nova. Urozhay, Kiev. Kupriyanov, V.V. et al. (ed). 1966. Resources of Surface Waters of USSR. Belorussia and Upper Dnieper 5, Hydrometeoizdat, Leningrad. Kuzko O.A. 1999. Phytoplankton of the upper Dniester. In: Conservation of Biodiversity on the Watershed of the Dniester River. Proceedings of International Conference. 7–9 October 1999. Kishinev, pp. 111–112. Loboda, N.S. 2005. Computations and generalization of characteristics of annual runoff of Ukranian rivers under antropogen influence. Ecology, Odessa. Lure, P.M., Panov, V.D., and Tkachenko, Y.Y. 2005. The Kuban River: Hydrography and Flow Regime. Hydrometeoizdat, St. Petersburg. Lysak, T.B. 2002. Modern structural–functional characteristic of the summer phytoplankton in the Tsymlyansk Reservoir. Contemporary Studies in Fishery of the Volgo-Don Basins. 50-Ubileum Issue, State Institute of Fishery Conservation, Moscow, pp. 29–38. Markova, A.K., and Simakova, A.N. 1998. Distribution of mammals and plants indicator species at the second part of Valday Glaciation. Izvestia RAS. Geographical Series 3: 49–61. Mamontov, Yu.P., Ivanov, D.I., Litvinenko, A.I., and Sklyarov, V.Ya. 2005. Freshwater Fishery of Russian Reservoirs. State Institute of Fishery Conservation, St. Petersburg. Protasiev, M.S. et al. (ed). 1973. Resources of Surface Waters of USSR. Don Region Vol. 7: Hydrometeoizdat, Leningrad. Reshetnikov, Yu.S. (ed). 2003. Atlas of Russian Freshwater Fish, Nauka, Moscow (in two volumes).

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Chapter | 13 Western Steppic Rivers

Romanenko, V.D. et al. (ed). 1987. The Nature of Ukraine. Seas and Freshwater, Naukova Dumka, Kiev, pp. 127–159. Salminen, R. et al. (ed). 2005. Geochemical Atlas of Europe. Part 1: Background Information, Methodology and Maps, Geological Survey of Finland, Espoo. Sokolov, A.A. 1952. Hydrography of USSR. Hydrometeoizdat, Leningrad. Shevlyakova, T.P. 2002. Present state of zooplankton in Tsymlyansk Resrvoir (1996–2001). Contemporary Studies in Fishery of the VolgoDon Basins. 50-Ubileum Issue, State Institute of Fishery Conservation, Moscow, pp. 46–52. Stratanovski, G.A. 2004. Russian Translation of the Herodotus History. OLMA-Press, Moscow. Strelets, B.I. (ed). 1987. The Handbook of Ukrainian Water Resources, Urozhay, Kiev. Sidorchuk, A., Borisova, O., and Panin, A. 2001. Fluvial response to the Late Valday/Holocene environmental change on the East European Plain. Global and Planetary Change 28(1): pp. 303–318. Troitski, S.K., and Tsunikova, E.P. 1988. Fish of the Lower Don and the Kuban: A Manual for Species Determination. Rostov Publishing Haus, Rostov-Don. Tuneakov, V.M. 1984. Fish characteristics of Karpov, Bereslavl, and Varvar reservoirs. Proceedings of State Institute of Protection of Fishery, Vol. 184, Moscow, pp. 86–96. Vishnevsky, V.I. 2000. Rivers and Reservoirs of Ukraine. The State and Management, Vipol, Kiev. Vishnevsky, V.I., and Kosovets, O.O. 2003. Hydrologic Characteristics of Ukrainian Rivers. Nika-Center, Kiev. Volovik, S.P., and Chikhachev, A.S. 1998. Anthropogen changes in ichthyofauna of Azov Basin. In: The Problems of Fishery and Management of Fish Reserervoirs in Azov-Black Sea Basin. Proceedings of AZIF, Rostov-on-Don, pp. 7–22. Zimbalenskay, L.N. et al. (ed). 1989. Invertebrates and Fish of the Dnieper River and Its Reservoirs, Naukova Dumka, Kiev.

Zhukinskiy, L.A. et al. (ed). 1989. Dnieper-Bug Estuarine Ecosystem, Naukova Dumka, Kiev. Zubkova E., and Shlenk D. 2004. Contemporary state of water quality in the Dniester River. In: Integrated Management of Natural Resources in Transboundary Basin of the Dniester River. International Conference, 16–17 September 2004, Kishinev, 4 p. Usatii, M. 2004. Evolutia, conservarea si valorificarea durabila a diversitati ihtiofaunei ecosistemelor acvatice ale Republicii Moldova. http://www. cnaa.acad.md.

FURTHER READING Archipov, E.M., Yakovlev, S.V., and Bogatyrev V.S. 2002. Composition of ichthyofauna of the river Don upstream of Tsimlyansk Dam. In: Contemporary Studies in Fishery of the Volgo-Don Basins. 50-Ubileum Issue. State Institute of Fishery Conservation, Moscow, pp. 62–68.

RELEVANT WEBSITES United Nations Development Program in Russia: http://www.undp.ru Electronic Journal Biodat: http://www.biodat.ru The Nature of the Kuban Region: http://priroda.kubangov.ru Ecological database of the Dnieper River: http://www.dnipro-ecobase.org. ua The Nature of Ukraine: http://library.thinkquest.org Ukranian Server of Hunters: http://www.uahunter.com.ua Ecology of Post-soviet States: http://www.ecologylife.ru Program Wetlands International in Russia: http://wetlands.ru Center for Wild Nature Protection: http://www.biodiversity.ru Transboundary Dniester River Project: http://www.dniester.org

Chapter 14

Rivers of the Central European Highlands and Plains Martin Pusch

Hans E. Andersen

J€ urgen B€athe

Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), M€ uggelseedamm 310, 12587 Berlin, Germany

National Environmental Research Institute (NERI) - University of Aarhus, Vejlsovej 25, 8600 Silkeborg, Denmark

EcoRing, Graftstr. 12, 37170 Uslar, Germany

Horst Behrendt

Helmut Fischer

Nikolai Friberg

Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), M€ uggelseedamm 310, 12587 Berlin, Germany

Federal Institute of Hydrology (BfG), Am Mainzer Tor 1, 56068 Koblenz, Germany

National Environmental Research Institute (NERI) – University of Aarhus, Vejlsovej 25, 8600 Silkeborg, Denmark

Aleksandra Gancarczyk

Carl. C. Hoffmann

Justyna Hachoł

Drawa National Park, ul. Le snik ow 2, 73220 Drawno, Poland

National Environmental Research Institute (NERI) - University of Aarhus, Vejlsovej 25, 8600 Silkeborg, Denmark

Wrocław University of Environmental and Life Sciences, Plac Grunwaldzki 24, 50-363 Wrocław, Poland

Brian Kronvang

Franciszek Nowacki

Morten L. Pedersen

National Environmental Research Institute (NERI) - University of Aarhus, Vejlsovej 25, 8600 Silkeborg, Denmark

Polish Geological Institute, Lower Silesian Branch, Jaworowa 19, 53-122 Wrocław, Poland

Aalborg University, Department of Civil Engineering, Sohngaardsholmsvej 57, 9000 Aalborg, Denmark

Leonard Sandin

Franz Sch€ oll

Matthias Scholten

Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment, 750 07 Uppsala, Sweden

Federal Institute of Hydrology (BfG), Am Mainzer Tor 1, 56068 Koblenz, Germany

Flussgebietsgemeinschaft Weser, An der Scharlake 39, 31135 Hildesheim, Germany

Sonja Stendera

Lars M. Svendsen

Ewa Wnuk-Gławdel

Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment, 750 07 Uppsala, Sweden

National Environmental Research Institute (NERI) - University of Aarhus, Vejlsovej 25, 8600 Silkeborg, Denmark

Drawa National Park, ul. Le snik ow 2, 73220 Drawno, Poland

Christian Wolter Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), M€ uggelseedamm 310, 12587 Berlin, Germany

Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

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526

14.1. 14.2.

14.3.

14.4.

14.5.

14.6.

14.7.

14.8.

14.9.

PART | I Rivers of Europe

Introduction Weser 14.2.1. Biogeographic and Geological Setting 14.2.2. Physiography, Climate, and Land Use 14.2.3. Geomorphology, Hydrology, and Biochemistry 14.2.4. Aquatic and Riparian Biodiversity 14.2.5. Management and Conservation Elbe 14.3.1. Biogeographic Setting 14.3.2. Physiography, Climate, and Land Use 14.3.3. Geomorphology, Hydrology, and Biogeochemistry 14.3.4. Aquatic and Riparian Biodiversity 14.3.5. Management and Conservation Oder 14.4.1. Physiography, Climate, and Land Use 14.4.2. Geomorphology, Hydrology, and Biogeochemistry 14.4.3. Aquatic and Riparian Biodiversity 14.4.4. Management and Conservation Em 14.5.1. Physiography Climate and Land use 14.5.2. Geomorphology, Hydrology, and Biogeochemistry 14.5.3. Aquatic and Riparian Biodiversity 14.5.4. Management and Conservation 14.5.5. Perspectives Skjern 14.6.1. Biogeographic Setting 14.6.2. Physiography, Climate, and Land Use 14.6.3. Geomorphology and Hydrology 14.6.4. Biogeochemistry 14.6.5. Aquatic and Riparian Biodiversity 14.6.6. Perspective Spree 14.7.1. Physiography, Climate, and Land Use 14.7.2. Geomorphology, Hydrology, and Biogeochemistry 14.7.3. Aquatic and Riparian Biodiversity 14.7.4. Management and Conservation 14.7.5. Perspective Drawa 14.8.1. Physiography, Climate, and Land Use 14.8.2. Geomorphology, Hydrology, and Biogeochemistry 14.8.3. Aquatic and Riparian Biodiversity 14.8.4. Management and Conservation Synopsis References

14.1. INTRODUCTION The ecoregion of the central European highlands and plains is drained by some of the main rivers that flow into the Baltic and North Seas, including the Weser, Elbe and Oder rivers. In addition to these rivers, this chapter describes some smaller but peculiar rivers such as the Em (Sweden), Skjern (Denmark), Spree (Germany) and Drawa (Poland) rivers (Figure 14.1a,b, Table 14.1). The landscape of the north-eastern central European plains was mostly shaped by the huge ice cap of the latest glacial period (Weichsel Glacial) that ended 10–12 000 years ago. The northern part of the ecoregion was covered by ice. While the remaining area was reshaped by periglacial processes. The glacial advance partly followed the pattern of the earlier Saale glacial period some 230–130 000 years ago, that completely covered the central European plains. Much of the landscape is therefore dominated by glacial and periglacial geomorphic elements such as moraines, outwash plains adjacent to terminal moraines, different types of lakes (ice-scour lakes, moraine-dammed ribbon lakes, kettle lakes, and glacial drift-plain lakes formed under the ice sheet), large glacial valleys, and large lowland plains consisting of glaciofluvial deposits. The different retreat stages of the glacial sheet produced a sequence of glacial valleys diverting meltwaters towards the North Sea. These valleys are still partially used by some rivers today, including the Elbe, Spree, Warta and Skjern. As river sediments mainly consist of sand, sediment transport occurs nearly continuously, creating ripples or subaqueous sand dunes reaching a crest height of up to 1.5 m. Regional ecological characteristics of the streams and rivers in the ecoregion have been summarized by Petersen and Gislason (1995) and Statzner and Kohmann (1995). As the landscape is relatively young and the sediment load of lowland rivers rather small, there also are numerous lakes interconnected by small to medium-sized rivers. Because the river basins are rarely underlain by solid bedrock, there is a high capacity for infiltration of precipitation and typically little seasonal variation in river discharge. Only the larger rivers originating in the highlands bordering the region undergo major flooding, as exemplified by the great Oder flood in 1997 and the great Elbe flood in 2002. With their relatively constant flow, larger rivers (Weser, Elbe, Oder) have been used for navigation for many centuries and their channels have been modified for navigation via the construction of groynes that narrow the river. Climate ranges from subatlantic in the western Central European Plains to subcontinental in the eastern areas (Table 14.1). In parts of the Elbe and Oder catchments, potential evapotranspiration exceeds precipitation, so that vegetation suffers from significant water stress in summer. There, drought regularly produces extensive periods of low flow that stops navigation for weeks to months during summer. With climate change, an increase in annual precipitation and a shift in ist timing from summer to winter is predicted for the western, subatlantic part of the ecoregion, while in the eastern part no increase in annual precipitation is expected.

Chapter | 14 Rivers of the Central European Highlands and Plains

527

FIGURE 14.1 Digital elevation model (upper panel) and drainage network (lower panel) of Rivers of the Central European Highlands and Plains.

14.2. WESER The Weser River-exhibits a balanced longitudinal sequence of geomorphologically distinctive river sections typical of

the Central European Highlands and Plains. Both headwater rivers (Werra and Fulda) originate in the central German highlands in Thuringia and Hesse, respectively, and are nearly the same size. The river is called the Weser after their

528

confluence, and crosses the highlands (called Oberweser) until it enters Lower Saxony in the north German lowlands (Mittelweser). At the mouth at the North Sea north of Bremen, an estuary is formed called the Unterweser, which is finally followed by a 46 km section that crosses the waddensea named Außenweser. The Weser has undergone severe anthropogenic alterations due to the high population density in the catchment, extensive agriculture, channelization and use for navigation, as well as significant effluent loads from wastewater treatment plants and salt mines. Salinization transformed the former freshwater river into a brackish water river for several decades. In 1992 and 2000, salt–water pollution of the Werra and Weser was reduced and freshwater assemblages have gradually recovered.

14.2.1. Biogeographic and Geological Setting The headwaters Werra and Fulda as well as the upstream part of the Weser (Oberweser) belong to the continental biogeographic region, while the middle and lower Weser (Mittel-, Unter- und Außenweser) belong to the Atlantic region. The Weser was not glaciated during the Weichsel glaciation period. The highlands of central and northern Germany geologically consist of a variety of Palaeozoic and Mesozoic formations. In contrast, the plains of northern Germany are dominated by Neozoic formations that were partially reshaped by Pleistocene glaciations. Following the late Carbon era, the mid-European mainland was bordered by seas in the north and south. A transgression of the Zechstein Sea produced thick salt deposits that are now found in Lower Saxony, Hesse and Thuringia (Feldmann et al., 2002). At the end of the Mesozoic, the Variszic rock mass was covered by three characteristic levels of Sandstone, Shell limestone and Keuper, the so-called ‘Germanic trias’. These deposits now form the spines of several steep mountain chains and escarpments in southern Lower Saxony, Weserbergland and the northern Harz. At the end of the Jura, pressure from the Mesozoic sediments caused deformations of the Zechstein salt-scales underneath, resulting in salt domes and salt anticlines. Tectonic movements at the end of the Cretaceous period caused the development of volcanoes of the Vogelsberg and Rh€ on. In the Quarternary, ice masses of the Elster glacial period extended from Scandinavia to the northern highlands in Lower-Saxony, reaching a thickness of 700–4000 m. The ablating glaciers pushed against the general orographic gradient rising towards the south, producing large icewater reservoirs. These reservoirs remodeled the landscape via glacial erosion and forced several rivers to change their course. One example is the Weser which continues to flow north through the mountain gate of Porta Westfalica. During the Holstein interglacial warm period and the Saale-Fuhne glacial period, the midterrace-gravel was deposited and is a resource in demand today. Glaciers did not reach the Weser catchment during the subsequent Weichsel glacial period. Tundra vegetation that covered northern Germany during a warming climate since

PART | I Rivers of Europe

13 000 years B.C. was first replaced by coniferous forest and then by deciduous forest around 7000 B.C. This landscape was then altered by humans who populated the catchment some 2500 years later (Feldmann et al. 2002; Hantke 1993). Beech, which now dominates forests in most of the catchment, migrated to central Europe during the Bronze age (2000–1000 B.C.). Discontinuities in the longitudinal gradient of the Weser produced during earlier glacial periods were modified later by fluvial erosion, so that nowadays the river shows a balanced longitudinal profile.

14.2.2. Physiography, Climate, and Land Use The Fulda, the left-side headwater of the Weser, originates from the basalt formation of the Rh€on at 850 m asl. The upper river follows a deeply eroded valley, mainly through sandstone formations. In the middle reach, the valley widens near Kassel to a width of 3 km, followed again by a narrow passage through sandstone formations until the Fulda joins the Werra at the city of Hann. M€unden at 117 m asl. The sources of the Werra originate at the border of the Thuringian forest and the Thuringian slate mountains at 800 m asl. From the city of Meiningen, the Werra flows north and follows a line between the Rh€on in the west and the Thuringian forest in the east. Subsequently, the Werra flows through the Zechstein salt deposits until it reaches Hann. M€ unden. From there, the upper Weser section called Oberweser flows through a geological and morphological diverse section of the highlands of Lower-Saxony. North of the city of Hameln, resistant sandstones of the Rh€at formation are crossed in a relatively narrow valley between the Weserbergland and the Wesergebirge. Breaching the Jurassic Malm layers of the Wiehengebirge at Porta Westfalica, the Weser enters the north German lowlands. Here, the river course changed frequently during the Pleistocene, and today crosses quaternary gravels and wetland clays (L€uttig 1974). The northern area of the Weser has a marine climate with average temperatures of 17 C in July and near 0 C in January. Precipitation ranges from 600 to 800 mm/year. In the highlands of the southeast catchment, the climate is more continental with temperatures averaging 17 C in July and 3 C in January. Here annual precipitation averages 800 mm, reaching local maxima of 1600 mm in the mountains. The influence of man on the rivers of the Werra and Weser began with neolithic settlements. In the medieval age, most of the catchment was deforested. Distinctive mammals like aurochs, wisent, brown bear, beaver and otter nearly vanished before the end of the 13th century. Regular forestry started in the 18th century to ensure a sufficient supply of wood. Log driving started in the 12th century, and towpaths were built to move ships and boats upstream. Later, coordinated river training was untertaken with artificial deepenings, bank reinforcements and the construction of barrages. Today, the morphology of the natural river channel and its floodplain is heavily transformed by river training and agricultural use.

Chapter | 14 Rivers of the Central European Highlands and Plains

Industries have been developed in a few cities along the Werra, Fulda and Weser. In the lower Weser, the Mittelland Canal crosses the river near the city of Minden, which connects Berlin with the Ruhr industrial area, thus providing a waterway between the Rhine, Weser and Elbe rivers. At the transition point to the tidal reach, the town of Bremen was founded with its port, which in the 19th century built another port called Bremerhaven 70 km downstream, to enable the access by larger ships. Industrial exploitation of the salt domes (Zechsteinsalzlager) in Hesse and Thuringia by mining and the potash industry since the early 20th century have heavily polluted the Werra and Weser by their salt effluents. The fertile soils of the Mittelweser floodplains have been completely modified for intensive farming. Agriculture and cattle ranching often extend down to the waterline, resulting in the destruction of riverbanks, water pollution by faeces, inputs of fertilisers and pesticides, and elimination of riparian vegetation by browsing. The Oberweser is less affected in that respect. Gravel is extracted in many places along the entire river, resulting in numerous gravel pits in the floodplain that are filled by groundwater and open to potential pollution.

14.2.3. Geomorphology, Hydrology, and Biochemistry The Fulda drains a catchment area of 6941 km2 and has a mean slope of 0.7‰ for 218 km until the city of Hann. M€ unden, where it has a mean discharge of 58 m3/s. The Werra drains a catchment area of 5496 km2 and flows with a mean slope of 0.6‰ for 292 km until it reaches its confluence with the Fulda, where it has mean discharge of 51 m3/s. The Weser, below the confluence of Werra and Fulda at 117 m asl, flows 432 km towards the estuary in the North Sea at Bremerhaven. The river is sectioned into the Oberweser (Rkm 0–204) from Hann. Muenden to Minden, the Mittelweser (Rkm 204–366) from Minden to Bremen, the Unterweser (Rkm 0–74, new counting) from Bremen to Bremerhaven, and the Außenweser (Rkm 74–120) from Bremerhaven to the lighthouse ‘Roter Sand’ within the North Sea. The main tributaries are the Diemel (left-side), Leine (right-side), Aller (right-side), and Hunte (left-side). The largest tributaries, Aller and Leine, bring waters from the western Harz Mountains, which receive up to 1600 mm of precipitation per year. The total drainage area of the Weser is 46 306 km2, ranging from 50 N to 53 N and from 8 E to 9 E. Mean channel slope is 0.48‰ for the Oberweser and 0.16‰ for the Mittelweser. Today, tides run up the river until the barrage of BremenHemelingen with a recent tidal range of 4.3 m (originally 0.7 m).

14.2.3.1 Hydrology The discharge regime follows a pluvio–nival type characterized by high flows in winter and a low water period from

529

June to October. Floods usually occur from December to January and March to April. A distinctive low water period that mainly occurs in the Werra and Oberweser is attenuated by a large reservoir on the Eder River, a left tributary to the Fulda River, to facilitate navigation on the Oberweser. Upstream of the inflow of the Aller River, the Weser has a mean discharge of 208 m3/s, to which the Aller adds 108 m3/s on average. Thus the discharge of the Mittelweser at Intschede/Bremen averages 326 m3/s (mean low water 117 m3/s, mean high water 1210 m3/s). In the Außenweser and Unterweser, tidal amplitudes, and the risk of storm tides, have considerably increased through channel deepening for navigation of even larger ships. Annual precipitation has historically shown an increasing tendency (5% increase from the period 1931–1960 to the period 1961–1990), with a decreasing share in summer and autumn (Engel 1995). Along the river, the Grohnde nuclear power plant at Rkm 125, the Veltheim coal power plant at Rkm 177, the Minden-Petershagen coal powerplant at Rkm 214, and the Landesbergen oil power station at Rkm 252 increase water temperatures by about 5–9 C. Due to these heat inputs, the annual mean temperature of the river increases by 3–4 C in the first 150 Rkm (B€athe 1992; FGG Weser 2003). Annual temperature of the Weser averages 11–16 C, with a maximum temperature of 30 C found in the impoundments of the Mittelweser during hot summer periods. Winter minima are 1–8 C, and since 1996 the freezing of the Weser has again been observed. Formerly, salt wastewaters discharged from the potash industry had essentially prevented the river from freezing.

14.2.3.2 Biogeochemistry The Weser is officially classified as ‘critically polluted’ (beta- to alpha-mesosaprobic), and in some sections even as ‘heavily polluted’ (alpha-mesosaprobic). Better water quality can only be found in the Aller upstream of the inflow of the Leine, and in the lower Fulda (Nieders€achsisches € Landesamt f€ur Okologie 2001). Most reaches of the Werra are classified as moderately polluted (beta-mesosaprobic). Additionally, the Werra has a high nutrient load, as only half of the wastewater produced in the Thuringian Werra catchment area is treated (Th€uringer Landesanstalt f€ ur Umwelt und Geologie 2007). In last decades, the pollution load of the Weser from municipal and industrial point sources has been reduced by the construction of modern sewage treatment works. Since the early 1990s, autotrophic biomass production has increasingly affected water quality through so-called secondary pollution (B€athe & Coring 2002; Herbst 1995). Nitrogen and phosphorus enter the Weser from point (N: 16%; P: 42%) and diffuse (N: 84%; P: 58%) sources. Although the nutrient inputs as well as the loade of the Weser were decreased considerably in the last two decades (N: 42%; P: 49%; Venohr et al., 2008) the present concentrations allow unlimited and occasionally excessive growth of algae.

530

PART | I Rivers of Europe

FIGURE 14.2 Long-term dynamics of phosphorous concentrations and discharge at the Bremen/Hemelingen measuring station (data: FGG Weser).

Algal growth is additionally favoured by inputs of potassium from the potash industry (Coring 2008), and high solar radiation because the riverbanks are mostly without riparian trees. From April until October, the dissolved oxygen (DO) budget of the Werra and Weser is influenced by the biomass and activity of phytoplankton. Impounded sections of the Werra and Weser show significant DO deficits with minima near 1 mg/L at low flow in hot summer (B€athe & Coring 2002; Herbst 1995). Although concentrations have declined since the late 1980s due to improved wastewater treatment, phosphorus concentrations still average 130–150 mg/L in the lower Mittelweser (Figure 14.2), and 200–600 mg/L in the Oberweser. Ammonium concentrations have decreased and now usually do not exceed 0.2 mg/L NH4–N at the Bremen/ Hemelingen monitoring station, whereas nitrate concentrations, which currently range between 2 and 5 mg/L, have only slightly decreased. The Werra and Weser have been heavily polluted by salt effluents from the potash industry in Hesse and Thuringia. Chloride concentrations peaked at 27 mg/L in 1992 and at 9 g/L in 1997 in the Werra at Gerstungen downstream of the mining region (Figure 14.3). Chloride pollution has largely changed the flora and fauna of both rivers (B€athe 1992, 1995,

1996, 1997, 2008; Coring 2008; Deutscher Verband f€ ur Wasserwirtschaft und Kulturbau 1998). The osmotic effects were further aggravated by the fact that chloride discharge was discontinuous and much lower on weekends, thus chloride concentrations varied weekly by several g/L. The ionic composition that resulted in the river differed from that found in natural marine or brackish waters. The high content of potash and magnesia affected most aquatic organisms at sublethal or even toxic levels. For instance, potassium causes toxic effects in aquatic organisms at concentrations >80 mg/L (Halsband 1976). For a long period, maximum salinity values in the lower Werra were higher than those of the Baltic Sea. From 1990 to 1992, a reduction in chloride concentration by 63% was recorded for the lower Werra, and since 2000 the concentration has not exceeded 2.5 g/L Cl at Gerstungen due to improved techniques of salt production and better effluent regulation. The chloride concentration is further diluted to a concentration of 400 mg/L by the city of Bremen some 505 km downstream. Colonization of the river by aquatic biota improved with the decrease in potassium concentrations below 100 mg/L (Deutscher Verband f€ ur Wasserwirtschaft und Kulturbau 1998).

14.2.4. Aquatic and Riparian Biodiversity The first studies on the biodiversity of the Weser were induced by impacts to fishery caused by river training that included several impoundments and gravel abstraction (Keller 1901). Additional impairments in fish populations were caused by wastewater inputs, increasing potassium concentrations, and extensive algal blooms (Buhse 1963, 1974; Halsband 1973). During the 1950s, the extinction of some amphipods was recorded, followed by taxa of Plecoptera, Ephemeroptera, Mollusca, and Bivalvia. In order to provide food for the remaining fish, the invasive Gammarus tigrinus was introduced to the Werra (Schmitz 1960). At the

Chapter | 14 Rivers of the Central European Highlands and Plains

same time, G. tigrinus migrated from the Weser estuary into the Mittelweser and began spreading upstream (Bulnheim and Scholl 1980; Bulnheim 1984). Thus, the aquatic invertebrate assemblages of Weser and Werra changed to groups that could tolerate the brackish water conditions.

14.2.4.1 Phytoplankton, Zooplankton, and Zoobenthos The phytoplankton of the Fulda, the Werra and the Weser is limited by the availability of dissolved nutrients, the presence of numerous impoundments, and water salinity. Phytoplankton assemblages of the Werra consist of 30 species and are dominated by the diatoms Thalassiosira pseudonana, Thalassiosira weisflogii, Cyclotella meneghiniana, and Stephanodiscus hantzschii. Chlorophyll concentrations can increase to >150 mg/L in the lower Werra during summer, and peak concentrations of 625 mg/L were measured in 1995 (Deutscher Verband f€ ur Wasserwirtschaft und Kulturbau 1998). Since 2002, aquatic macrophytes have become abundant in the saline Werra, which is paralleled by a decrease in phytoplankton (Coring 2008). Except for short periods, phytoplankton in the Weser predominantly originates from the Werra. Fast growing diatoms display a high biomass within the free-flowing Oberweser (Photo 14.1). Since zooplankton is found only sporadically, the algal biomass is consumed mostly by macrozoobenthos. In the impoundments of the Mittelweser, much of the phytoplankton settles and is microbially decomposed, creating significant DO deficits. During the growing period from April to October, centric diatoms dominate the phytoplankton along the entire Weser. Besides centric

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diatoms, volvocales and chlorococcales are also abundant. Benthic pennate diatoms enter the water column only during high flows. During low flows, coccale nanoplankton develop after sedimentation of the diatoms. With lower salt concentrations, green and blue–green algae have appeared in the lower Werra since 2004. From 1986 to 1992, a total of 87 taxa of macrozoobenthos has been recorded in the Weser. As a consequence of lower salt concentrations, the number of taxa has now risen to 168. During the high salinity period, native species such as Anodonta spp., Unio spp., Theodoxus fluviatilis, Asellus aquaticus, Gammarus fossarum, Gammarus pulex, Gammarus roeseli, Potamanthus luteus, Ephoron virgo, and several trichopterans were replaced by species from other aquatic ecosystems and only 25% of the earlier freshwater taxa remained (B€athe 1992). Ecological functions of the benthic community were taken over by G. tigrinus, Oligochaeta, Apocorophium lacustre, Potamopyrgus antipodarum, Cordylophora caspia, Chironomidae, and Dendrocoelum lacteum. Besides G. tigrinus, the amphipods Chelicorophium curvispinum, A. lacustre, and Corophium multisetosum were common in the Weser. A. lacustre, a genuine brackish-water species that expanded from the Weser estuary, colonised the Weser up to the city of Hann. M€unden by 1990. Depending on the degree of salinity and phytoplankton biomass, Corophiidae can show high population densities (e.g. A. lacustre at 437000 ind./m2 and C. multisetosum at 4000 ind./m2). According to their halotolerance, A. lacustre today colonises the Unterweser, the Oberweser, and most of the navigable Werra, while C. multisetosum is confined to Mittelweser reaches with low current velocities at lower densities. Originating from the Aller, the freshwater PHOTO 14.1 Weser at Rkm 96 upstream of the city of H€oxter. The river channel is protected here against lateral erosion by perpendicular rip–rap groynes overgrown by grass. The river corridor is bordered by dikes, and the floodplain is mostly used as grassland and crop fields (Photo: J. B€athe).

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C. curvispinum migrated into the Weser at chloride concentrations of 410 mg/L. Today, this species is common throughout the Weser and the navigable section of the Fulda. The halotolerant bivalvia of the Weser can attain high biomasses of 8–47 g/m2 (Dreissena polymorpha), and 0.7– 8.1 g/m2 (Corbicula fluminalis). Since 1998, the invasive amphipod Dikerogammarus is found in the Weser and the navigable Fulda. Low abundances of Trichoptera that appeared since 1993, including Hydropsyche bulgaromanorum, H. pellucidula, Ceraclea dissimilis, Cyrnus trimaculatus, Ecnomus tenellus, Hydroptila spp., Lasiocephala basalis, Polycentropus flavomaculatus, Psychomyia pusilla, Rhycophila dorsalis gr., and Tinodes waeneri, indicate an improvement in water quality in the Weser. Recolonisation of the Mittelweser by Theodoxus fluviatilis, which had disappeared in the early 1960s, also began in 1993. The mussels Anodonta spp. and Unio spp. have spread into the Oberweser since 1995, tolerating salinities of 1.3–2.2‰ (chloride concentrations of 620– 1150 mg/L). Sensitive insects like Caenis luctuosa, Heptagenia sulphurea, Serratella ignita, and Leuctra fusca have returned to the river at a maximum salinity of 2.8‰. Another typical mayfly of the Weser is Ephoron virgo, which returned in 1996 after 40 years of absence.

14.2.4.2 Fish, Amphibians and Mammals The lower Werra and Fulda as well as the upper Oberweser belong to the barbel fish region. Downstream the barbelbream fish region extends from Rkm 44 to Rkm 204 (Buhse 1990). Due to river training, the Mittelweser cannot be assigned to any particular fish region, and today the characteristic fish is the common bream. The first channelisation of the Weser caused a decrease in the numbers of migrating Atlantic salmon, sea trout, Atlantic sturgeon, houting, smelt, allis shad, twaite shad, herring, river lamprey, and sea lamprey (Keller 1901). In the Mittel- and Unterweser, river training still continues to further improve conditions for navigation. After the Second World War, toxic potassium concentrations caused fish kills (Buhse 1963, 1974; Halsband 1973, 1976), and up to 1990 fishery was dominated by roach, European eel, and perch (Nieders€achsisches Landesamt f€ ur Wasser und Abfall 1991). After salinity levels decreased, the ichthyofauna diversity of the Oberweser again increased. Today, 26 species have been recorded in surveys with chub, common dace, roach, European eel, perch, and European bullhead as well as barbel being most common (Figure 14.4).

14.2.5. Management and Conservation The Weser and its tributaries provide important ecological services to society, including drinking water (e.g. for Bremen), sewage removal, water for irrigation, cooling water for power plants and industrial facilities, hydropower, habitat for organisms, and recreation and tourism. Several of these ser-

PART | I Rivers of Europe

vices compete for water quantity and quality. Today, fishery provides little economic benefit. Presently, navigable river sections represent 89 km of the Werra, 109 km of the Fulda, 117 km of the Aller, 97 km of the Leine, and all 487 km of the Weser. The first shipping traffic was recorded in the 12th century. Today navigation is concentrated on the river section between Minden and Bremen, connecting the Mittelland Canal to the seaport of Bremen. From 1906 to 1910, the dam in Bremen/Hemelingen was built to stop the erosion caused by the deepening of the Unterweser. The dam at Doerverden (1907–1913) was built to counteract groundwater lowering caused by increasing drainage of the landscape for farming. Five more dams were constructed (Petershagen 1953, Schl€usselburg 1956, Landesbergen 1960, Drakenburg 1956, Langwedel 1958) to provide sufficient water depth for navigation by large barges. In addition, levees were built, backwaters and streams were straightened, and a reallocation and consolidation of agricultural lands changed former floodplains for modern agriculture. Since 1982, the Mittelweser has been deepened and now provides a water depth of 3 m during low flows to maintain navigation of 1350 tons ships between Minden and Bremen. The Werra is impounded by 58 weirs and the Fulda by 60 weirs. The Flussgebietsgemeinschaft Weser (FGG Weser), as the administrative unit responsible for the river, began studies in the Werra, Fulda, Weser and Aller in 1965. Since 1975, a measuring program was established and then amended by a general ecological planning group in 1996 (Arbeitsgemeinschaft zur Reinhaltung der Weser 1996). This program planned the reintroduction of migrating fish (1996), guidelines for pollution accidents (2002), and a monitoring plan for rivers of the Weser catchment (FGG Weser 2007). A comprehensive evaluation of the environmental condition of the Weser catchment is available to assist in future management plans (FGG Weser 2005). A further decrease in nutrient and sewage loads is a priority in the future management of the Weser. The Weser, Werra, Fulda and Aller have been severely affected by anthropogenic pressures created by multi-purpose uses. The main factors impairing the ecology and ecological services of the

Chapter | 14 Rivers of the Central European Highlands and Plains

Weser system are well known among ecologists and river managers, but still must be appreciated in a socio-economic context. The decrease in sewage and salt loads, as well as the re-establishment of the native fauna and flora, including the investments towards this success, have been widely accepted by society. Future management plans should include flood protection and the restoration of natural river functions and services.

14.3. ELBE With a length of 1094 km, the 8th order River Elbe (Czech: Labe) is the third longest river in central Europe (after the Danube and Rhine). It drains more than half the area of the Czech Republic and more than 25% of Germany. Smaller parts of its catchment also lie in Austria and Poland. Starting from its source in the Czech Giant’s Mountains (Krkonose), several reaches of the river have special touristic interests such as the scenic river canyon in Elbsandsteingebirge that forms the Czech–German border, the riverbanks that add to the scenery of the historic city of Dresden, and the floodplain forests along its middle course. The Elbe is often seen as a river still possessing a natural river bed with active floodplains; for example there are no impoundments on a 622 km stretch from Ustı nad Labem to Geesthacht. Indeed, its banks are still subject to fluvial dynamics and the largest contiguous floodplain forest of central Europe has been preserved along its course. In this river section, intensive biological activity occurs, reflected in significant changes in the composition of riverine dissolved and particular matter, making it an interesting site for limnological research. Most of the river from Pardubice to Hamburg is used for navigation, and the river has 24 impoundments within its first 350 km. The phytoplankton biomass coming from these impoundments, further supported by significant nutrient loads downstream, affects the water quality along most of the river, especially near Hamburg. In the tidal section downstream of Hamburg, the water increasingly mixes with seawater before flowing through the Elbe estuary to the North Sea.

14.3.1. Biogeographic Setting During the Weichsel Glacial period, the northeast Elbe catchment and neighbouring regions were covered by an ice sheet. As the orography in northern Europe is generally inclined northward, meltwaters from the glacier, as well as river discharge, accumulated near the southern front of the glacier and formed large lakes that were precursors of the Baltic Sea. Glacial impoundments that formed in northern Eurasia were probably temporarily connected by periglacial rivers. Parts of such periglacial river valleys are still used by the Elbe and its tributaries like the Havel and Spree. These periglacial rivers were east-west migration corridors, connecting formerly isolated rivers from western Europe to Lake Baikal (Sch€afer 1997).

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14.3.2. Physiography, Climate, and Land Use Below the source pool at 1386 m asl in the Giant’s Mountains, the headwaters of the river form a mountain stream with a scenic waterfall of 35 m. After leaving the mountains, the river enters the Bohemian Cretaceous basin and flows through entrenched valleys, an optimal situation for constructing reservoirs. In the Bohemian basin, the river forms a large bend successively redirecting the Elbe from the southeast to the northwest. Downstream, the Elbe merges near Melnık with the Vlatava (Moldau) River, which exceeds the Elbe in length (430 km versus 367 km), in catchment size (twofold larger) and discharge. Downstream of the confluences of the Vlatava and Ohre (Eger) rivers, the Elbe enters the Bohemian uplands. There, the river valley cuts into volcanic bedrock at the Strekov castle near Ustı nad Labem, where the river is impounded by the last weir in its the Czech segment (Photo 14.2). This section is followed by a scenic river canyon that breaches the Elbsandsteingebirge. After flowing for 365 km, and with about 30% of its final discharge, the river crosses the Czech–German border near the village of Schmilka. The river then flows for another 95 km through uplands and loess-covered lowlands, forming a number of islands. The romantic silhouette of Dresden mirrored in the Elbe has prompted UNESCO to include this valley section in its world cultural heritage list. Downstream of the historic city of Meißen, the river enters the North German lowlands, thus forming the border between the upper and middle Elbe. In the lowlands, the river partially follows ancient glacial valleys formed during the Elster, Saale and Weichsel Glacial periods. The river flows over bedrock only at the cities of Torgau and Magdeburg, which causes significant problems for navigation due to changes in gradient and depth. The discharge of the Elbe increases considerably from inputs by the large right tributaries Schwarze Elster and Havel as well as by the left tributaries Mulde and Saale. Near Magdeburg, the river splits into several branches that were mostly closed in historical times but are partially used at high flows. Downstream of Magdeburg, the Elbe valley widens to 20 km and crosses glacial deposits, and then enters a glacial valley partially used by the Havel tributary today. At the village of Geest-hacht upstream of Hamburg (German Rkm 586), the middle Elbe ends and the river is now influenced by tides of the North Sea. Today the tidal influence is limited upstream by the large weir impounding the Elbe at Geesthacht, which is the only weir within the German river section. The tidal range in the lower Elbe has been largely increased by man through substantial deepening of the channel, which was done to allow passage of large ocean ships to reach the port of Hamburg. This port was mostly built along a 15-km long anastomosing reach of the Elbe bordered by two larger river branches, the Norderelbe and S€uderelbe. Downstream, the Elbe forms a funnel-shaped river mouth that originally included many islands. Today, some rare freshwater tidal areas are preserved in some places. Salt waters from

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PART | I Rivers of Europe

PHOTO 14.2 Elbe near Ustı n.L. (Aussig) with the ruins of the medieval Strekov (Schreckenstein) castle built in the 14th century on a phonolith rock to protect navigation on the river. In the 19th century the castle towering the free flowing river had been a favourite subject of romantic painters, musicians and poets. Upper: Painting by Ferdinand Lepie 1856 (Museum Ustı nad Labem), with the railway line Dresden – Prague which had been completed five years before. Lower: Today’s view with the structures of the weir 10 m in height in front of the silhouette of the industrial town of Ustı. The weir was completed in 1936 to impound the river section in order to improve navigation at low water levels. (Photo: D. Fiker, Ustı).

the North Sea increase salinity downstream of Gl€ uckstadt. At Cuxhaven, salinity reaches a level of 18–30 per mil, and the sandy river shores gradually change into the vast tidal flats bordering the North Sea. Climate in the Elbe catchment ranges from maritime in the northwest to subcontinental in the southeast. Mean air temperature ranges from 8–9 C in the lowlands to 1–3 C on upland ridges. Temperature extremes range between 29 C and +39 C in the German part of the catchment, and between 42 C and +40 C in the Czech part (IKSE 2005).

The mean number of ice days (daily maximum <0 C) per year is 15–30 in the lowlands but reaches 100 on mountain peaks. The mean number of summer days (daily maximum >25 C) per year is 15–50 in the lowlands and 5–20 in the uplands. Precipitation in the catchment averages 612 mm but differs greatly between sub-basins. One third of the catchment receives <550 mm, especially in the sub-basins of the Vlatava, Ohre, Saale and Havel. Precipitation minima are found in the Ohre and Saale catchments with many places receiving only 430–450 mm rainfall per year. Mountain

Chapter | 14 Rivers of the Central European Highlands and Plains

ridges in the catchment receive between 1000 and 1800 mm of precipitation. Highest daily rainfall recorded was 345 mm in Nova Louka in the Iser Mountains in July 1897, and 312 mm in the same region at Zinnwald in the East Erzgebirge Mountains in August 2002 (IKSE 2005). Precipitation mostly occurs in summer (May–October), especially in the upper catchment, while precipitation is highest in winter in high mountain areas where snow cover may reach 150 cm in the Giant’s Mountains (IKSE 2005). There are 25 million people living within the 148 242 km2 Elbe catchment, 75% of which live in Germany and 25% in the Czech Republic. All major urban centers present in the catchment are on the Elbe or a large tributary, including Prague, Leipzig, Berlin and Hamburg. The sewage water produced in the catchment is treated in over 1600 wastewater treatment plants (Behrendt et al. 2004a). Land use in the catchment is dominated by crop fields (51%), forests (29%), other agricultural uses (12%), and settlements and roads (7%). Surface waters make up only 1.3%, but peak in the catchment of the Elde tributary (10%). This catchment includes, besides others, the largest lake within the borders of Germany, Lake M€ uritz. Some 25% of the lower catchment downstream of Hamburg is used as pastureland (Becker & Lahmer 2004).

14.3.3. Geomorphology, Hydrology, and Biogeochemistry 14.3.3.1 Geomorphology The Elbe and its upper tributaries originate in the geologically old upland region of Bohemia and thus exhibit a relatively regular longitudinal profile in channel slope. This profile historically stimulated long-distance navigation on the river. In the German section, the channel gradient decreases to 13–17 cm/km, so that the middle Elbe forms large meanders that have been cut through at various locations since the 16th century. Here, the floodplains are often covered by a layer of clay mostly formed in the time period between medieval forest clearings and the development of a contiguous dyke system along the Elbe. In this section, sedimentation of suspended matter during floods in the floodplain near the river channel has increased the ground level in the valley centre. More distant floodplain areas partially lost drainage capacity and developed into marshes and alder swamps. Some smaller tributaries do not enter the Elbe directly, but flow parallel to the Elbe before entering some distance downriver (Schwartz 2006). At some places, sandy sediments have been developed into dunes by the wind.

14.3.3.2 Hydrology The runoff rate in the Elbe catchment averages 5.5 L km2 s1, and varies from 4 L km2 s1 in the north tributaries of the Elde and Schwarze Elster to nearly 12 L km2 s1 in the St€or

535

catchment in the northwest. With a runoff rate of 5.9 L km2 s1, the Czech part of the catchment contributes a nearly average amount (Behrendt et al. 2004a). The length of yn the river between its source upstream of Spindleruv Ml (Spindlerm€uhle) to the Czech–German border is 367 km, and from there to its mouth at Cuxhaven is 727 km, a total 1094 km. However, the largest tributary of the Elbe, the Vlatava (Moldau) River, has a length of 430 km, thus the total river length equals 1247 km from a hydrological point of view. The flow regime of the Elbe is a rain-snow type. Hence, floods mainly occur in winter, but may also can occur in summer such as the extreme flood in August 2002. Discharge of the Elbe averages 101 m3/s at the gauge station Brandys n. L. just upstream of the confluence with the Vlatava River, and is 336 m3/s in Dresden, 715 m3/s at the gauge station in Wittenberge, and 859 m3/s at the gauge station Zollenspieker just upstream of Hamburg. Total discharge into the North Sea near Cuxhaven is estimated at 870 m3/s (IKSE 2005). The largest tributaries of the river are the Vlatava (mean discharge 154 m3/s), Ohre (38 m3/s), Mulde (73 m3/s), Saale (115 m3/s) and Havel (115 m3/s) rivers. The travel time of river water at mean discharge is 5 days for the 137-km long impounded section from the Elbe’s confluence with the Vlatava River to the Czech–German border. The travel time from the border to Magdeburg is 4 days, from there to Geesthacht (upstream of Hamburg) 4 days, and from there within the deep tidal section of the river to Cuxhaven 26 days (IKSE 2005).

14.3.3.3 Biogeochemistry Along its course, the Elbe changes gradually from a mountain stream rushing over rocks to a gravel-bed river in most of the Czech section and in the upper German part, until finally meandering as a sand-bed river through the lowlands. In the middle Elbe, water depth of the river channel is about 1.5– 2.5 m during mean low water and 3–4 m at mean discharge (B€uchele 2006). Due to impoundments in the Czech section, the river downstream lacks a sediment load and the river is incised in several sections. Depth erosion was quantified being up to 1.6 m within 130 years. In the section downstream of Torgau, erosion actually continues at a rate of 2 cm/year. Depth erosion and subsequent lowering of the water table threatens constructions near the river and hampers navigation over the bedrock outcrop in the channel at the city of Torgau. It also threatens the ecological integrity of the middle Elbe biosphere reserve which aims to protect waterdependent floodplain fauna and flora, and especially the persistence and natural regeneration of characteristic softwood and hardwood floodplain forests. In the lowlands of the Elbe downstream of Lutherstadt Wittenberg, bottom sediments mainly consist of sand and sediment transport continuously occurs at all discharge levels. Here, subaqueous dunes occur at heights of >1.5 m and lengths of several hundred metres (Nestmann & B€uchele 2002). These dunes constantly move and pose difficulties to navigation.

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FIGURE 14.5 Long-term dynamics of the DO concentrations at the measuring station Schnackenburg (Elbe-km 475, 140 km upstream of Hamburg), reflecting the sudden improvement of water quality with the breakdown of east German industry in 1990 (data by Nieders€achsischer Landesbetrieb f€ur Wasserwirtschaft und K€ustenschutz L€uneburg).

The dominance of agricultural land use in the catchment is directly reflected in the nutrient inputs, estimated at 12 354 t/yr P, and 259 950 t/yr N on average for the freshwater section of the Elbe from 1993 to 1997. Nitrogen mainly comes from diffuse sources (73% of total N inputs), as nitrogen inputs from point sources, especially wastewater treatment plants, have been greatly reduced since the late 1980s. Diffuse nitrogen sources are mainly groundwater inputs to small tributaries (114 960 t/yr). The proportion of diffuse phosphorus inputs was 42% during 1993–1997 (Behrendt et al. 2004a, 2004b). Diffuse inputs of phosphorous and nitrogen peaked in the 1970s and 1980s when the massive use of fertilizers created a significant surplus in agricultural areas. In the German part of the catchment, this was drastically changed in 1990 when the use of fertilizer nearly stopped. Since then the use of fertilizers has increased again moderately. For the time period 2003–2005 a reduction of total nutrient inputs to thh Elbe was estimated, which amount to 150000 t/yr (N) and 5000 t/yr (P) (Behrendt pers. comm.). Focal areas of diffuse inputs of phosphorous are upland regions with significant soil erosion and former wetlands that have been drained for crop fields (Behrendt et al. 2004a). Natural values for nutrient concentrations in the

PART | I Rivers of Europe

Elbe system, based on background nutrient immissions, are estimated at <50 mg/L of total phosphorous and <1 mg/L of total nitrogen (Behrendt & Opitz 1999). Up to 1990, water quality of the Elbe was dominated by massive inputs of poorly treated wastewater from adjacent cities and factories, especially by a high content of phosphorus in detergents. The section in and downstream of Dresden was so polluted that no existing degradation level could be assigned using the biological assessment saprobic system. With the breakdown of East German industries and subsequent improvement of wastewater treatment plants, the loading by organic as well as inorganic contaminants has been greatly reduced (Figure 14.5). Transparency of the water now allows extensive growths of planktonic algae (Figure 14.6), and the river has changed from a heterotrophic ecosystem to a highly eutrophic one. It now suffers from substantial ‘secondary pollution’ by autotrophically produced biomass. Planktonic algae are thriving on the high nutrient levels in the river, except for the lowermost section. The phosphorus and silica load of the river in summer mostly appears as algae and detritus. Besides the availability of nutrients, algal growth is further supported by the relatively shallow river channel of the sand-bed middle Elbe in Germany that provides sufficient light for algal growth. Additionally, algal growth is favoured by the constant inoculation of plankton from impoundments in the Czech section of the Elbe. A similar situation is found in nearly all of the tributaries with a catchment size >1000 km2; all exhibit chlorophyll concentrations that exceed the limits set for good ecological status (Behrendt et al. 2004a). Phytoplankton, mostly diatoms, enter the free-flowing section of the Elbe in Germany in high concentrations with a seasonal mean (April–October, 1994–2006) of 45 mg chl-a/L at Schmilka (German Rkm 4), and increasing at Schnackenburg (Rkm 475) to 128 mg chla/L. Maximum concentrations can reach >300 mg chla/L (data by ARGEElbe), and concentrations exhibit high intra- and inter-annual dynamics (Pusch & Fischer 2006). Typically, a spring

FIGURE 14.6 Long-term development of the concentrations of chlorophyll-a and ortho-phosphate at the measuring station Schnackenburg (Rkm 475, 140 km upstream of Hamburg; data by ARGE Elbe).

Chapter | 14 Rivers of the Central European Highlands and Plains

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FIGURE 14.7 Longitudinal changes of chlorophyll-a and nutrient concentrations in the German section of the Elbe during a travel time of the river water of 6–9 days. Starting values at German Rkm 3.9 (Schmilka) are set as 100%. Means are from four Lagrangian sampling campaigns. Samplings were conducted on 26.6.–5.7.2000 at low discharge, on 24.7.–1.8.2005 at medium discharge, on 8.5.–15.5.2006 at high discharge and on 6.8.–15.8.2007 at medium discharge. Extra symbols represent concentrations in the tributaries Schwarze Elster (Rkm 198), Mulde (Rkm 259), Saale (Rkm 291), and Havel (Rkm 438). Data and graph by Federal Institute of Hydrology.

phytoplankton peak occurs in the upper middle Elbe, while in the lower section chlorophyll concentrations remain high, although dynamic, during the growing period (Figure 14.7). Higher chlorophyll concentrations occur due to longer water residence times in dry years, although this pattern can be dampened due to nutrient and light limitation as well as by zooplankton grazing in the most downstream reach. The high primary productivity leads to conspicuous longitudinal patterns in dissolved inorganic nutrient concentrations. Along the course of the river, nitrate, ortho-phosphate and silicate concentrations decrease significantly during summer low-flow situations. Ortho-phosphate–P and silicate–Si concentrations in downstream reaches may drop below 0.01 and 0.15 mg/L, respectively, and limit additional

phytoplankton growth, while nitrate–N rarely falls below 1 mg/L (Figure 14.7) (data by ARGE-Elbe). Hence, the high primary productivity in the free-flowing section of the Elbe shows characteristic seasonal dynamics similar to lakes with a spring bloom, a clear water phase, and summer blooms (Figure 14.8). Due to intensive photosynthesis, DO concentrations are often supersaturated in this section, and pH values can exceed 9. The large biomass of planktonic algae fuels intensive recycling by microbiota, which mostly takes place in the river sediments. Sedimentary microbial activity is not limited to the sediment surface but can reach up to 1 m into the sediment. Microbial activity within the sediments is sustained by a continuous supply of nutrients and substrates FIGURE 14.8 Seasonal course of chlorophyll-a and DO concentrations at Cumlosen (Rkm 470, 145 km upstream of Hamburg) in 1998, with DO saturation concentration added in red, reflecting the river’s marked plankton dynamics (data by Landesumweltamt Brandenburg).

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provided by the fluvial transport of sediments and hydrologic connectivity between sediments and river water (Fischer et al. 2005). Through the intense hydraulic coupling of river water with sediments, a measurable fraction of the river’s load of organic matter is retained, for example 2.5 tons of particulate organic matter per river km in winter (Schwartz & Kozerski 2006). Based on measurements of microbial metabolism in the river sediments using a diving bell, it was estimated that 1.4% of transported organic carbon is degraded per river km. Highest metabolic rates were measured in the oxic uppermost 40 cm of the shifting sandy sediments present in the central river bed. Degradation of organic matter was also high in muddy sediments near the shore in the so-called groyne fields, but the high rates were limited to a shallow superficial layer (Fischer et al. 2005). Retention of nitrogen was estimated at 10–20 tons of NO3–N per river km and year. Besides the mid-stream sediments, high nitrogen retention also occurred at places on the shore where groundwater exfiltrates from the floodplain aquifer (Pusch & Fischer 2006). In spite of the significant retention of organic matter, the production/respiration ratio in the Elbe is often >1 during summer, and large masses of living algae are transported along the river to the estuary. There, the die-off and subsequent decomposition of living biomass can cause severe oxygen deficiency with saturation values of 30% and less (data by ARGE Elbe). In contrast to other rivers, this estuarine zone of DO depletion is in the freshwater tidal section of the Elbe (Bergemann et al. 1996). DO depletion is caused by multiple factors that are related to the high input of algal biomass, long water residence times and river morphology. Due to long residence times, grazing by zooplankton can regulate algal biomass in the lower Elbe. Zooplankton regularly reaches concentrations of >1000 rotifers per litre in the lower middle Elbe (Holst 2006), and >1000 copepods per litre are regularly found in the freshwater part of the Elbe estuary. River morphology also contributes to the algal dieoff because artificially deepened sections (16-m shipping depth) reduce light availability for algae and increase water residence times, particularly within and downstream of the port of Hamburg. Finally, depletion of nutrients (namely silica) can impede the sustainability of a high biomass of living and growing algae in the estuary (BfG 2006). The nutrients which are set free by algal die-off significantly contribute to the eutrophication of the North Sea. Today the ecological status of the Elbe in most of its sections is estimated as moderate based on benthic invertebrates. The status of the fish fauna has been estimated to be even good according to the assement tool applied, while phytoplankton density and communities indicate a poor status (data from ARGE Elbe). The river is still significantly contaminated with heavy metals, and the Mulde tributary and deeper Elbe sediments still show even high concentrations. The Czech section of the Elbe as well as the Mulde and Saale tributaries are still significantly loaded with chlorinated carbohydrates (data from ARGE Elbe).

PART | I Rivers of Europe

14.3.4. Aquatic and Riparian Biodiversity 14.3.4.1 Riparian Flora and Fauna Water-dependent fauna and flora along the Elbe are protected within a series of reserves of differing status. In the Giant’s Mountains, the Czech-Polish Krkonose National Park and biosphere reserve holds elements of subarctic fauna and flora seen as glacial relicts, and boasts 40 ha of peat bogs designated as a Ramsar international wetland site. While most of the central Bohemian river section has been largely transformed, a relict floodplain forest at the confluence of the Vlatava and Elbe rivers still harbours snails and fairy shrimps (Anostraca) typical for floodplains, while the diversity of riverine species is significantly reduced there due to water pollution (IKSE 2005). Along the German river section, 32, Natura 2000’ areas, 10 important bird areas and a large UNESCO biosphere reserve border the river. Along the German lowland section of the Elbe, the biosphere reserve ‘Flusslandschaft Elbe’ extends over 400 km covering 1257 km2 within the L€ander of Sachsen-Anhalt, Brandenburg and Mecklenburg-Vorpommern. In Sachsen-Anhalt, the largest contiguous floodplain forest in Central Europe has been preserved with a large diversity of water-dependent woodland and grassland habitats, including softwood and hardwood floodplain forests (Scholz et al. 2005). It also harbours the only population of beaver that persisted in Central Europe during the 19th and 20th centuries. The beaver population that was reduced to 90 individuals in 1950, has largely expanded and recolonized large parts of north-east Germany (IKSE 2005). In the floodplains, large populations of fairy shrimps (Anostraca) colonize temporary pools formed behind dikes during high water levels. The downstream park section in Brandenburg, Niedersachsen and Mecklenburg-Vorpommern features a 0.5– 3 km wide relict floodplain before the dikes, wet pasturelands behind the dikes, as well as dunes with dryland fauna and flora. It boasts a high density of stork with 500 used nests being regularly counted. The tidal section of the Elbe downstream of Hamburg has along its shores and islands the largest freshwater tidal mudflat in Europe.

14.3.4.2 Fish Communities The current fish and lamprey fauna of the Elbe consists of 94 species of which 34 occur solely in the marine and brackish area (ARGE-Elbe 2000). The river sections with the highest diversity of fish are the brackish water habitat with 59 species, and the middle Elbe harbouring 52 species. Fish assemblages in the estuary are dominated by anadromous species in terms of numbers, mostly by smelt and alvine, although contributing only 7% to species richness (Thiel & Potter 2001). Most species inhabiting the Elbe estuary represent peculiarities compared to other European estuaries. For instance, the alvine is a species listed in the European Habitats Directive, so that special conservation measures must be considered.

Chapter | 14 Rivers of the Central European Highlands and Plains

In total, 17 diadromous fishes occur in the Elbe, of which 10 use the middle Elbe for spawning habitat or migration (Pezenburg et al. 2002). Formerly, large populations of these fish migrated upstream, including the Atlantic salmon, Atlantic sturgeon, European eel and smelt, all of high importance for the fishery (IfB 2004; Von dem Borne 1882). The original populations of the Elbe salmon and Elbe sturgeon, and also the migrating form of the houting, have become extinct since the middle of the 20th century (Pezenburg et al. 2002). Recent measures aimed to reintroduce salmon have succeeded in the first natural reproduction of returning adult salmon in Saxony and Brandenburg (Zahn 2003). Hence, there is hope that this migrating fish will be re-established in the Elbe in time. Additionally, there are attempts to reintroduce the Atlantic sturgeon (Kirschbaum & Gessner 2002) and migrating populations of houting. The Eel stock of the Elbe has also been considerably diminished as part of a European-wide trend (IfB 2004). The upstream migration of glass eel in the Elbe has especially decreased during the last 20 years, as well as in all other estuaries of Central and Western European rivers (Dekker 2003). In order to stabilize and protect the eel populations of the Elbe, a basin wide management plan is needed. Lampreys, especially the river lamprey, were also formerly caught in large numbers in the Elbe and processed as fodder up to the middle of the last century (Thiel & Salewski 2003). The decrease in populations was caused partly by poor water quality, but also by the construction of the weir in Geesthacht upstream of Hamburg that prevented access to spawning habitats upstream (Dierking & Wehrmann 1991; Gaumert & K€ammereit 1993). During the 1990s, river lamprey reappeared in significant numbers in the lower Elbe (Thiel & Salewski 2003). The number of animals migrating upstream also increased after the construction of a by-pass channel that circumvented the Geesthacht weir. Consequently and new spawning habitats were discovered in the Stepenitz tributary (Lill & Winkler 2002). In contrast, sea lamprey, which probably also depend on habitats in tributaries of the lower Elbe, remain rare. Of the 43 native freshwater fishes in the Elbe, 40 occur in the middle Elbe. The rheophilic common dace, ide and asp (Fladung 2002; Scholten 2002) occur regularly and are abundant, while blue bream shows significant interannual variation in abundance. Barbel have increased their populations in the middle Elbe (ARGE Elbe 2005). Other fish such as burbot and vimba, that formerly had large populations (Bauch 1958), have significantly decreased in numbers since. The migrating form of the burbot suffers especially due to the disconnection of its feeding habitats in the lower Elbe from the spawning habitats in the middle Elbe and its tributaries by the construction of Geesthacht weir (Koops 1959, 1960). The spirlin is classified as missing species (Pezenburg et al. 2002). Silver carp, bighead carp, grass carp, brown bullhead, white sturgeon und rainbow trout have been classified as invasive fishes, as these were introduced into the basin of

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the middle Elbe after 1900 (ARGE-Elbe 2000). The status of the whitefin gudgeon is unclear (Scholten 2000; Freyhof et al. 2000). Overall, 13 of 94 fish species of the Elbe have been classified as potentially endangered, rare or endemic. These include euryhaline species such as river lamprey and sea lamprey, allis shad, and twaite shad, Atlantic salmon and houting, but also seven limnic species such as brook lamprey, asp, barbel, whitefin gudgeon, bitterling, weatherfish and spined loach. According to the Habitats Directive (European Union 1992), the member states of the European Union have a special responsibility for their preservation. A network of designated habitats must be developed and engineering measures adapted to meet species conservation goals (FGG Elbe 2004).

14.3.4.3 Macroinvertebrates In the Elbe, 600 species of benthic macroinvertebrates have been recorded (Sch€oll & Fuksa 2000). The most predominant ones are flatworms (Tricladida), snails and mussels (Mollusca), oligochaet worms (Oligochaeta), leeches (Hirudinea), crustaceans (Crustacea), insects (e.g. Ephemeroptera, Trichoptera, Plecoptera, Chironomidae), freshwater sponges (Spongillidae) and bryozoans (Bryozoa). The local composition of invertebrate assemblages is determined by the physical, chemical and biological conditions that gradually change along the river course, as well as by anthropogenic alterations like wasterwater discharge and hydraulic engineering measures. The Elbe headwaters in the Giant’s Mountains are inhabited by the triclad Crenobia alpina as a characteristic coolwater species, which is considered to be a glacial relict. The numerous rivulets that flow together to create the mountain river Elbe exhibit torrential flow, a rocky-stony streambed, high oxygen saturation and low water temperatures, and thus are colonized by a rich stonefly fauna (e.g. Perla spp.). Due to releases of air-borne contaminants (SO2, NOx) from fossil fuel combustion, acid-sensitive species, such as some mayflies (Ephemeroptera) and amphipods (Gammaridae), are rare in these headwaters. Downstream of the mountain area, organic pollution and impoundments affect invertebrate assemblages. In the impoundments, the original rheophilic fauna of the Elbe is mostly replaced by lentic species or generalists. The river section cutting through the Elbsandsteingebirge has a high species richness. In particular, snails (Radix peregra), European fingernail clam (Sphaerium corneum), and caddisflies (Hydropsyche contubernalis) are found. At a few locations upstream of Dresden, unionid mussels (Anodonta anatina, occasionally Unio pictorum) can be found. Between Dresden and Magdeburg, six species of pollution-tolerant leeches (including Glossiphonia complanata) can be found. Near Riesa, some individuals of the Chinese mitten crab (Eriocheir sinensis) have been found, which migrated 600 km from their reproduction sites in the

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tidal Elbe downstream of Hamburg. Between Magdeburg and Geesthacht, the density and richness of triclads, leeches, as well as some insect species strongly decreases by a still unknown reason. This section is dominated by sow bugs (Asellus aquaticus, Isopoda) as well as scuds (Gammarus tigrinus). The stones used in groynes protecting the shores from erosion are predominately covered by sessile species such as Hydrozoa (Cordylophora caspia) and Bryozoa (Paludicella articulata, Plumatella fungosa, Plumatella emarginata and Plumatella repens). Further, the Asian dragonfly (Gomphus flavipes), a typical inhabitant of large, sandy rivers, has been recorded again (after its last record in 1929). The constantly moving sand-bed sediments in the central channel of the Elbe are colonized by the specialized annelid Propappus volki. In the impounded reach upstream of the weir Geesthacht, the zebra mussel Dreissena polymorpha reaches its highest density at 4000 ind./m2. As the life cycle of this species involves a 14-day free-swimming larval stage, the populations at Geesthacht probably originate from the supply of larvae from the Bohemian segment of the Elbe. The number of benthic invertebrate species decreases in the tidal section between Geesthacht and Hamburg. Fluctuating water levels prevent the colonisation of groyne heads by many lithophilic species. Here the shrimp Palaemon longirostris may be found, a brackish water species that often migrates far upstream in rivers. The zone of continuously shifting salinity between Hamburg and Cuxhaven limits the osmoregulation of many organisms, and consequently the area is colonised by a few extremely euryhaline species, such as the crustaceans Jaera albifrons, Gammarus zaddachi and Bathyporeia sp., as well as the hydrozoan Laomedea sp. The density of the barnacle Balanus improvisus increases along the gradient of rising salinity. Populations of the three mud shrimps Chelicorophium curvispinum, Apocorophium lacustre and Corophium volutator are established in the estuaries of the North and Baltic Seas, whereby C. curvispinum tolerates the lowest salinity and C. volutator is found at the highest salinity. North of Cuxhaven, marine species dominate, including the blue mussel, the European green crab and small marine scuds (e.g. Gammarus salinus). Historic records of the invertebrate assemblages in the Elbe reveal a close relationship to the pollution status of the river at a given date, involving a dramatic reduction in species richness with increasing pollution level and decreasing DO content. In particular, insects and large mussels suffered a considerable loss up to the 1980s. Since 1990, numerous species have reappeared that that had not been present for several decades of severe pollution in the Elbe (Figure 14.9). An impressive example is the return of the mayfly species Oligoneuriella rhenana in the Elbe section crossing the Elbsandsteingebirge Mountains at the Czech–German border in 1996. This mayfly is an ecologically sensitive species and characteristic for middle-sized, fast flowing rivers. Some tributaries of the Elbe in the Czech Republic probably served as refugia for this species. Presently, O. rhenana has expanded its range in the river downstream to Magdeburg.

PART | I Rivers of Europe

Current invertebrate assemblages of the Elbe significantly differ from that known from the 19th century due to changes in water quality, hydraulic engineering measures, and navigation. Passing ships can create waves of >30 cm in height at the shoreline, which resuspend fine sediments and dislodge invertebrates (Brunke & Guhr 2006). Additionally, the introduction of new species has altered invertebrate assemblages. In the 1990s, several invasive species appeared, such as the Black Sea isopod Jaera sarsi and the scud Dikerogammarus villosus. These are two typical Danubian species that migrated via the Main-Danube canal, finished in 1992, and then via the Rhine and Mittelland Canals into the Elbe. In particular, D. villosus populated long sections of the Elbe within a short period of time.

14.3.5. Management and Conservation 14.3.5.1 Economic Importance In the Czech part of the catchment, the Elbe and its tributaries are retained in 19 reservoirs with a volume >0.3 million m3 which sum up to 167 million m3. The reservoirs are mainly used to retain floods and to increase discharge at low water levels. The Elbe itself is impounded by 24 weirs that are mostly smaller, except the reservoirs Labska und Les Kralovstvı that hold 11 million m3. Impoundments allow navigation by ships with a draught of at least 2 m within a 170-km section of the river between the uppermost harbour near Pardubice and Ustı nad Labem (IKSE 2005). Thus, the Elbe has been transformed into a chain of impoundments with few free-flowing reaches remaining. Historically, hydropower was used in the upper Elbe to drive mills by the construction of numerous weirs built from wood or stones, which were also used for timber rafting. In 1841, a regular ship connection was established between Prague and Dresden (IKSE 2005). By 1874, a navigation chain line was established between Hamburg and Ustı nad Labem (formerly Aussig), which means that an 668-km iron chain – consisting of 18-cm chain links – was laid on the river bed and used by specially designed steamboats to which barges were tied.

FIGURE 14.9 Historic development of dissolved oxygen content of the Elbe in Magdeburg, and of species richness within selected groups of benthic invertebrates in the river recorded within the whole freshwater section of the river in Germany.

Chapter | 14 Rivers of the Central European Highlands and Plains

Another peculiarity of navigation on the Elbe was the paddle-steamers that still cruise around Dresden as excursion boats. Today, inland cargo transport on the Elbe is limited technically and economically by the fact that planned minimum depth for navigation is only 1.6 m, and that even this depth is not met for more than three months each year (average for in the river section upstream of Magdeburg since 1990; data from the Federal Waterways and Shipping Administration). Barges therefore, often may be only partially loaded, so that cargo transport by barges has greatly decreased since 1990. Near Torgau, water from the Elbe is used via bank filtration to supply drinking water to the urban cities of Leipzig and Halle, both situated in a region receiving low precipitation. The risks produced by major floods on the Elbe have been increased by reducing the former floodplain area to 16% by the construction of levees for use as crop fields (Kausch 1996). After the great flood in 2002 it was widely discussed to leave more space for the river to decrease flood risks. Since then, Elbe dikes have been moved back at only two sites, and other floodplain areas will in the future be used as polders. In contrast, dikes have been raised further in most of the German river segment.

14.3.5.2 Conservation and Restoration Even after considerable improvements in water quality since 1990, the Elbe significantly suffers from anthropogenic pressures such as nutrient inputs, hydro-morphological alterations and navigation. The shores, sediments in the groyne fields of the lower middle Elbe (Photo 14.3), and fine sediments in the lower Elbe are still heavily contaminated by heavy metals and organic contaminants, for

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example some 50 kg of deposited lead (Pb) has been estimated for a typical groyne field (Schwartz & Kozerski 2006). The Czech segment of the river is impounded for most of its length, while the shores of the upper middle Elbe in the German section are mostly fixed by stone rip– rap or by 6900 groynes extending into the river channel. There, vertical erosion is combatted by the addition of 20 000–80 000 t/yr of a sand–gravel mixture into various reaches. As the lower middle Elbe is paralleled by a canal (Elbe-Seitenkanal), which forms an alternative for navigation between Magdeburg and Hamburg, barge navigation on the Elbe and options for river management have been discussed controversially for many years between authorities and initiatives to protect the Elbe (Pusch 2006). Additional controversial discussions relate to river training measures on the Elbe section bordering the UNESCO World Heritage of the Dessau-W€orlitz landscape park, and the construction of an additional Elbe bridge within the UNESCO World Heritage of the Dresden Elbe valley. In many places along the Elbe efforts have already been taken to preserve diverse shoreline structures, to enable fish migration to tributaries, to reconnect oxbow lakes, to replant floodplain forest, and to find alternative ways of shore protection than traditional ones. The lower Elbe has been deepened to 16 m depth to allow the passage of large container ships to the port of Hamburg. These deepening efforts counteract actions to attenuate dissolved oxygen deficiencies that regularly occur there.

14.3.5.3 Perspective The improvement in water quality from the former bad to the present moderate status after 1990 constitutes one of the PHOTO 14.3 The Elbe near the village of Cumlosen (upper right) at Rkm 467–470. The lowland section of the river channel is nearly totally fixed by perpendicular groynes made of stones. On the left bank some broken groynes may be seen, which are less filled with sediment deposits than others. Ancient river channels are visible on the left and right banks; the left side has a hardwood floodplain forest (Photo: Federal Institute of Hydrology).

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most impressive success stories in river management. After alleviation of the formerly dominating saprobic pollution pressure, a set of other significant pressures appeared to be limiting ecosystem structure and function, such as eutrophication, morphological alterations, interruptions of sediment load and fish migration, and hydrodynamic impacts by inland navigation. For instance, even after the construction of a by-pass channel the weir in Geesthacht upstream of Hamburg still forms a major obstacle for fish migration, especially for larger fish species. This hampers the successful re-introduction of migratory fishes such as salmon and sturgeon. Hence, management options for the river depend on its future use for inland navigation and hydropower generation, as well as on more effective retention of diffusive inputs of nutrients from agriculture. While diffuse inputs from agriculture may be reduced by changing agricultural practices, and the retention of effluents by riparian buffer strips, hydro-morphological deficiencies could be considerably improved by redesigning groynes to create overflow shallow shore areas, by re-opening and creation of side channels, by the protection of shallow waters from ship-induced wave action, by the construction of effective fish ladders at weirs, and by moving dikes farther away from the river.

14.4. ODER The Oder (Polish and Czech: Odra) is the sixth largest river flowing into to the Baltic Sea, with an annual discharge volume of 17.3 km3. Being 854-km long, the Oder is the second longest river in Poland (after the Vistula). Only 6% of the catchment area lies in the Czech Republic and 5% in Germany. The Oder catchment stretches from the Sudety Mountains to the Szczecin Lagoon on the southernmost margin of the Baltic Sea. It is asymmetrically shaped, with major left-side tributaries only found in the upper and middle segments of the river. The lowermost left tributary, the Lusatian Neisse (Nysa Łu_zycka), together with the lower Oder forms the German–Polish border. Most of the catchment consists of lowlands, especially in the largest right-side tributary, the Warta River, which exceeds the Oder in length. Downstream of Szczecin (Stettin), the river flows into the Szczecin Lagoon (Zalew Szczeci nski, Oderhaff). Here the river is divided into three branches between the islands of Usedom and Wolin that eventually reach the Baltic Sea in the Bay of Pomerania. From its mouth, the Oder is navigable for ocean ships up to Szczecin, and for inland navigation for a length of 717 km until the small city of Kozle 40 km upstream of Opole. The biogeography of the region is largely determined by the Weichsel glacial period and the post-glacial formation of melt-water lakes in the basin of the Baltic Sea. The postglacial recolonization of the Oder system by aquatic biota therefore followed similar patterns as in the Elbe and Vistula rivers.

PART | I Rivers of Europe

14.4.1. Physiography, Climate, and Land Use The Oder rises in the Sudety Mountains, Czech Republic, at 634 m asl, only 20 km east of the city of Olomouc which borders another major river, the Morava. Headwater streams lie in the Oderske Vrchy Hills near the settlement of Mesto Libava. The Oder first flows southeast, then follows a valley heading northeast, called Moravian Gate, that allows passage between the Sudety Mountains in the west and the Beskid Mountains in the east. The river then passes the city of Ostrava, the second largest urban area in the Czech Republic after Prague, an industrial centre based on coal mining and steel industry. After crossing the Czech–Polish border, the river reaches the upper Silesian lowlands south of the city of Racib orz at an altitude of 200 m asl. The river then flows northwest where it receives several major left-hand tributaries that drain the Sudety Mountains, such as Nysa Kłodzka, Bystrzyca, Kaczawa, Bobr and Nysa Łu_zycka (Lusatian Neisse). The Oder passes through the scenic historic city of Wrocław (Breslau), which was originally built on several islands of the Oder. Near the city of Głogow, the river receives its major right-side tributary in Silesia, the Barycz. The Barycz is a pure lowland river originating between the cities of Ostrow Wielkopolski and Ostrzeszow, and follows a glacial valley with low slope (20–30 cm/km). It drains extensive wetland areas. Near the city of Krosno Odranskie, the Oder receives the left-side tributary Bobr. The B obr is 268 km long, has a catchment area of 5900 m2, and a mean slope of 2.8 m/km. The upper headwaters of the B obr in the Giant’s Mountains (Karkonosze) in the area of Jelenia G ora are adjacent to the Elbe River. The direction of the Oder abruptly changes north at the confluence with the Nysa Łu_zycka (Lusatian Neisse) south of the German city of Eisenh€uttenstadt. The Lusatian Neisse originates in the Czech Jizera Mountains east of Liberec, soon after reaching the border triangle of the Czech Republic, Poland and Germany near the German city if Zittau. For 197 km (of a total length of 254 km) it forms the German–Polish border until its confluence with the Oder. Downstream of the confluence, at 32 m asl, the Oder passes the old Hansa city of Frankfurt (Photo 14.4). At the former Prussian fortress of Kostrzyn, the Warta River joins with the Oder, contributing 40% to its discharge. At 808 km in length, of which 50% is navigable, the Warta exceeds the Oder in length at the confluence. The Warta, together with its right-side tributary, the Notec, drains a pure lowland area of 54 529 km2. The Warta originates near the famous city and pilgrimage place of Czestochowa, then heads north through agricultural landscapes. It flows into Lake Jeziorsko reservoir (42.3 km2 area, 202 million m2) near the city of Lodz, then turns west near the city of Konin, again flows north towards the city of Poznan, and finally flows again west for the rest of its course. It receives the Notec tributary near the city of Gorzow Wielkopolski. The Drawa River (see ch. 14.8) is a tributary of the Notec. The

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Chapter | 14 Rivers of the Central European Highlands and Plains

PHOTO 14.4 The Oder River downstream of the city of Frankfurt. The straightened river channel is fixed by perpendicular groynes and ancient river channels are visible. The river corridor, which is bordered by dikes, has only sparse tree cover because the trees suffer from ice drift that may occur during high water levels in winter (Photo: Oder-Luftbild, Lebus).

lower Wartas valley, up to the confluence with the Oder, harbours a vast wetland protected by the Warta Mouth (Ujscie Warty) National Park. After the confluence with the Warta, the Oder enters the 15 km wide Oderbruch valley, which forms part of the Eberswalde–Toru n glacial valley. The Oderbruch originally formed a vast floodplain with meanders and anabranches of the Oder until the river course was straightened and shortened by 25 km from 1746 to 1753 by order of the Prussian King Friedrich II. The downstream end of the Oderbruch, at only 1.5 m asl, marks the place where the Oder breached the moraines of the Weichselian glacial period to flow to the Baltic Sea. Downstream of Schwedt, the river splits into the West Oder and East Oder branches, encompassing a vast polder wetland which today forms the heart of the German–Polish Lower Oder Valley International Park. The slow flowing river then passes the historic Pomeranian capital and seaport of Szczecin (Stettin) and Lake D˛a bie, which has a surface area of 56 km2. Shortly downstream the river enters the Szczecin lagoon (Zalew Szczeczi nski, Oderhaff) with a surface area of 900 km2 but a mean depth of only 4 m. This lagoon flows into Pomeranian Bay via three channels, first the Peenestrom (which also receives the Peene River) separating the German mainland from the island of Usedom, second the Swina (Swine) separating the islands of Usedom und Wolin (including Kanał Piastowski built 1875–1880), and third the Dwinow channel separating Wolin from the Polish mainland. Flow direction in these three channels may be reversed by northerly winds, and the Swina River has a delta at its southward end. The Swina enters the Pomeranian Bay at the small seaside port city of Swinouj scie (Swinem€ unde). The total length of the Oder is 912 km if the lagoon and Swina sections are included.

Average channel slope is 0.7‰ (K€ohler & Chojnacki 1996). The catchment area upstream of Szczecin equals 118 861 km2, while the total catchment area contributing to Pomeranian Bay is 136 528 km2 (Behrendt & Dannowski 2005). The Warta contributes an area of 54 529 km2 to the Oder catchment. A sub-continental climate dominates most of the Oder catchment and is reflected by cold winters that regularly result in the formation of significant ice cover on the Oder for about one month. Mean precipitation in the catchment is only 587 mm, of which 133 mm contributes to river runoff, which equals 5.0 L km2 s1. While the southern slopes of the Sudety Mountains receive 700 to >1500 mm of precipitation, the Poznan region receives a low of <400 mm (Behrendt & Dannowski 2005). Average July temperature is 18.5 C, average January temperature 1.5 C. Snow cover lasts for 40–60 days, and the vegetation period is 220 days. Land use in the catchment is urban area at 4.0%, arable land 54%, grassland 7.7%, forest 31%, and waterbodies at 1.3% (Behrendt & Dannowski 2005). The sub-basin with the highest forest percentage (54.4%) is the Drawa (see ch. 14.8).

14.4.2. Geomorphology, Hydrology, and Biogeochemistry Based on the physiogeographic division of Poland, the Oder catchment covers six units, including the SudetyMountains, Saxonian–Lusatian Lowlands, Silesian–Cracow Highlands, Central Polish Lowlands, Southern Baltic Lake District, and the Southern Baltic Littoral (Behrendt & Dannowski 2005). The upper river flowing through the Moravian Gate uses a tectonic fault that allows it to cross the geologically old

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PART | I Rivers of Europe

PHOTO 14.5 The Oder River downstream of the city of Frankfurt during the great flood in 1997, with the regular river channel visible in the background. (Photo: M. Pusch).

mountain ridges bordering the Bohemian–Moravian basin to the north. The river is divided into three geomorphologically and hydrologically different areas: the upper Oder from the source to Wrocław, the middle Oder from Wrocław to the mouth of the Warta River, and the lower Oder from the Warta tributary to the mouth into the Szczecin Lagoon. Discharge in the high Sudety basin of the Oder follows a nival regime, while streams in the rest of the catchment have a pluvial-nival regime with highest discharge in March and April. A particular hydrologic characteristic of the Oder is summer floods (Photo 14.5) that occur mainly in August. These are caused by Mediterannean cyclones heading north, which can produce heavy rainfalls in the Erzgebirge and Sudety Mountains (Landesumweltamt Brandenburg 1997). The largest tributary, the Warta, enters the Oder at Rkm ow gauging 618 and contributes on average 224 m3/s (Gorz station, Landesumweltamt Brandenburg 1994). Average discharge of the Oder equals 522 m3/s at the gauge Hohensaaten-Finow at Rkm 665. However, runoff there varies by a factor of 31 between the lowest (111 m3/s, September 1921) and highest (3475 m3/s, April 1888) discharge values recorded (Uhlemann & Eckoldt 1998). At the gauge station Hohensaaten-Finow, the lowest and highest reported water levels were 0.84 m and 7.78 m, respectively. Flow velocity in the lower Oder between Eisenh€ uttenstadt and Schwedt averages 0.36 m/s at mean water level (Landesumweltamt Brandenburg 1994). In the lower Oder, water temperatures range between 0.4 and 28.8 C (Water and Navigation Authority Eberswalde). Summer water temperatures typically exceed 20 C for at least one month, while winter temperatures may fall below 0 C, a situation that leads to the formation of anchor ice. On average, the Oder is patially covered by ice 50 days per year (Sch€ onknecht & Gewiese 1988).

The Oder catchment is populated by 16 million inhabitants, of which 1.5 million live in the Czech Republic, and 0.7 million in Germany. Mean population density is 135 inhabitants/km2. The Oder receives inputs of 11 t/yr of cadmium, 175 t/yr of copper, 113 t/yr of lead and 1190 t/yr of zinc (data for the time period 1993–1997). These result in estimated loads near the mouth of 3 t/yr of cadmium, 67 t/yr of copper, 40 t/yr of lead and 331 t/yr of zinc. In comparison to the Rhine and Elbe, heavy metal loads, especially from sub-basins, of the upper river are high for cadmium and lead (Behrendt & Dannowski 2005). Total nutrient emissions were estimated for the time period 1993 to 1997 at 13,500 t/yr P and 106,000 t/yr N, with 36% of the nitrogen and 61% of the phosphorus being discharged by point sources. In comparison to other large river catchments, loads in the Oder are high for phosphorous, indicating a good potential for further reduction, for example by improvement of wastewater treatment plants. The loads for nitrogen are relatively low, which may be explained by the relatively low percentage of inhabitants connected to wastewater treatment plants and especially by the implementation of P-free detergents in the Polish part of Odra (Behrendt & Dannowski 2005). Diffuse nutrient inputs, especially from agricultural areas, were slightly decreased with the political changes in 1990, with a moderate increase since. A significant proportion of the nutrient load in the river is retained. River loads near the mouth (gauge station Krajnik Dolny) were estimated at 4700 t/yr ammonium-N, 42,000 t/yr nitrate-N, and 5100 t/yr total phosphorus. Accordingly, the Oder has a high eutrophication potential with average nutrient loads of 3.45 mg/L total N and 0.17 mg/L total P. Median dissolved oxygen (DO) concentrations of the Oder are 9–10 mg/L. In periods of high temperatures and low discharge, DO concentrations decrease temporarily to 3–6 mg/L. Due to the general shallowness of the river, it is efficently reoxygenated by physical gas exchange through the water surface.

Chapter | 14 Rivers of the Central European Highlands and Plains

14.4.3. Aquatic and Riparian Biodiversity 14.4.3.1 Fish Communities The fish inventory of the Oder comprises 53 native riverine fish and lamprey species (Wolter & Freyhof 2005). Three native fishes, such as sturgeons and Atlantic salmon, must be considered extinct today. Restoration programs are running for two of these species, Atlantic salmon and Baltic sturgeon (Acipenser oxyrinchus), the latter program headed by the Institute of Freshwater Ecology and Inland Fisheries in Berlin. Salmon disappeared from the river in the middle of the 1840s (Gerhard 1893) and initial stocking programs began in 1869. From 1869 to 1879, 12,000 to 320,000 salmon hatchlings were stocked annually, in total 1,522,600 hatchlings (Gerhard 1893). The first salmons were recaptured in the Oder in 1872 and in the Warta in 1874. In the upper Oder, no salmon were recorded after 1876, while catches in the Warta continuously increased up to 1130 salmon with individual weights of 6–15 kg in 1887 (Gerhard 1893). Heavy pollution from industrial effluents in the upper Oder has been considered as the main reason for the later decline in the abundance of migratory fish (Pax 1917). Interestingly, Jobst (1571) had already emphasized a better taste of fish from the Warta. In Poland, a stocking program for salmon was restarted in 1995, and from 1996 to 1999 between 11,403 and 75,443 hatchlings were stocked annually (Bartel 2001). No returning adults have been reported so far. Eight fishes have been recorded to be much more abundant before river regulation, including river lamprey, sea trout, vimba, nose carp, barbel, burbot, crucian carp, and swamp minnow; the latter two due to the loss of floodplain waterbodies. Most probably, other riverine species with similar habitat requirements also declined, but this is not clearly shown using historical records. The dramatic impacts of river regulation on fish assemblages are evident in the nearly total decline in the populations of barbel, nose carp, and vimba, which are seen as characteristic species for typical riverine habitat conditions. Barbel was one of the most abundant fish, accompanied by nose carp and vimba, and common until the end of the 19th century (von dem Borne 1882). Today, vimba is lacking in the middle and upper Oder, and nose carp as well as barbel are rare. In the middle Oder, there were important spawning sites for long distance migratory species. Today, these reaches are dominated by eurytopic fishes such as common bream, silver bream, and roach. This clearly indicates a human-induced shift in river status from a fast-flowing barbel region to a slow-flowing bream region due to regulation. Accordingly, limnophilic and eurytopic fish occur much more upstream in the river compared to pre-regulation times. Including non-native species, a total of 67 freshwater fish and lamprey species have been recorded in the Oder basin. Non-native species were introduced mainly at the end of the 19th and in the second half of the 20th century. Recently, 11 non-native species have been recorded in the basin, but none

545

has established reproducing populations (Wolter 2007). The immigration of additional species via the Vistula-Oder waterway is expected.

14.4.3.2 Macroinvertebrates Between 1998 and 2001 about 270 species or higher taxa were found in the Oder. Adding earlier surveys conducted since 1992 in the river bordering Germany increases this number to 370 species. The zoobenthos is dominated by Tricladida, Mollusca, Oligochaeta, Hirudinea, Crustacea, Insecta (Ephemeroptera, Trichoptera, Plecoptera, Chironomidae), Spongillidae and Bryozoa. The density of individuals varied from 0 to 10,000 ind./m2 between river reaches, position of a sample in the river, and season. The natural longitudinal gradients in physical and chemical characteristics have been changed by regulation in the Oder, thus most rhithral assemblages have been replaced by potamal taxa or by habitat generalists. This is especially evidient in the middle Oder. Most benthic invertebrates in the Oder are categorized as filter feeders, predators, grazers or sediment feeder. The density of filter-feeders increases from the upper to the middle Oder. In the upper river, the zoobenthic community inhabits the riverbed relatively homogenously. Downstream, zoobenthos is mainly concentrated on large stable rip–rap stones along the banks, in particular sessile and semi-sessile macroinvertebrates. The center of the river where high bedload transport occurs is inhabited by only a few species. Areas without bedload transport that may be found upstream of impoundment weirs deviate from this distribution pattern. In the headwaters of the Oder, the stoneflies Perla burmeisteriana and Leuctra albida were found in epirhithral to metarhithral reaches near the village of Jakubcovice. Typical species also included the caddyflies Hydropsyche saxonica and Potamophylax sp. At Svinov near Ostrava, the Ephemeroptera Baetis buceratus, B. fuscatus, Heptagenia coerulans and Ecdyonurus starmachi indicate that the river has epipotamal character. With the wastewater input from the urban area of Ostrava/Bohumin, the density of leeches increases (Erpobdella octoculata, Glossiphonia heteroclita) and the caddisfly and mayfly fauna are similar to that of large rivers (Baetis rhodani, B. fuscatus, Hydropsyche contubernalis, H. pellucidula). The town of Kozle marks the beginning of the impounded navigable reach of the Oder that extends 185 km upstream of the city of Wrocław (Breslau). The reduction in flow velocity causes the disappearance of most lotic species, and the impounded middle Oder is inhabited by the amphipod Gammarus tigrinus. Immediately downstream of weirs lotic species of the genus Baetis, Hydropsyche and Cheumatopsyche occur at low densities. Downstream of the last weir at Brzeg Dolny, the abundance of characteristic species shows a level that is typica of large rivers: tricladids (Dendrocoelum lacteum, Dugesia lugubris, Dugesia tigrina), snails (Bithynia

546

PART | I Rivers of Europe

TABLE 14.1 General characterization of the Rivers of the Central European Highlands and Plains

Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25 %) ecological regions Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparse vegetation Wetland Surface waters

Weser

Elbe (with Spree)

Oder (with Drawa)

Em

Skjern

193 46 306 10.3 70.1 8.2 3 6; 70

258 148 242 27.4 61.2 8.3 4 22; 70

164 118 861 17.3 58.7 8.2 5 22

195 4460 1.0 59.3 5.9 1 59

Spree

Drawa

49 2490 1.1 89.2 7.6 2 6

92 10 105 1.1 56.6 9.0 3 22

103 3289 0.7 59.2 7.9 2 10; 22

7.4 48.5 12.7 29.3 0.9 0.1 0.7 0.4

6.9 50.9 9.4 29 2.0 0.2 0.2 1.4

4.0 54.0 78 30.9 1.6 0.2 0.2 1.3

1.6 11.4 1.1 74.1 6.2 0.0 0.6 5.2

2.3 75.7 0.7 11.8 6.8 0.0 2.5 0.2

11 39.1 6.2 37.3 2.1 1.3 0.4 2.6

1.1 31.7 4.8 55.3 1.4 1.5 0.1 4.1

Protected area (% of catchment)

0.6

4.3

1.5

0.3

3.1

0.1

3.5

Water stress (1–3) 1995 2070

2.0 2.1

2.0 2.9

2.0 3.0

1.0 1.0

1.0 1.0

2.0 3.0

1.8 2.7

Fragmentation (1–3) Number of large dams (>15 m) Native fish species Nonnative fish species Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person)

3 15 38 5 6 204 23 434

3 86 43 8 17 169 14 068

2 21 53 11 15 135 5583

3 0 29 2 0 16 26 394

2 0 24 2 0 42 34 592

3 1 37 7 2 306 17 237

2 0 39 2 0 30 4551

For data sources and detailed explanation see Chapter 1.

tentaculata, Potamopyrgus antipodarum), and mussels (D. polymorpha, Sphaerium corneum, S. rivicola, and S. solidum) are abundant. Among the five large mussels found Anodonta cygnea, A. anatina, U. pictorum and U. tumidus dominate; Pseudanodonta complanata occurs more rarely. The rip–rap stones are covered with the dwelling tubes of C. curvispinum that locally occur at densities of >100,000 ind./m2. Other sessile, colony-forming species living there are freshwater sponges (Spongilla fragilis), bryozoans (Paludicella articulata), and freshwater polyps (Cordylophora caspia). The insect fauna consists mainly of caddisflies like Hydropsyche contubernalis and H. bulgaromanorum, mayflies (especially Heptagenia sulphurea) as well as midges (Chironomidae). Among chironomids, species of the genus Chironomus, Robackia demeijerei and Glyptotendipes pallens dominate. The dynamic river-sand deposits in the river provide suitable habitat for specialized species like R. demeijerei and Lipinella araenicola. The invertebrate assemblage of the lower Oder differs little from that of the upper river. The constant presence of the snails Viviparus viviparus and Theodoxus fluviatilis is noteworthy, which often reach densities of >100 ind./m2. Another frequent invertebrate is the waterbug Aphelocheirus

aestivalis that preferentially inhabits the gravel-sandy river bottom in areas with average flow velocities. Among the beetles, Limnius volckmari is a typical element of the potamal fauna that inhabit the lower Oder. Between Ratzdorf and Widuchowa other red-listed species attain significant abundances, such as the riverine dragonflies Gomphus flavipes, Gomphus vulgatissimus, Ophiogomphus cecilia, and Calopteryx splendens, as well as the molluscs P. complanata and Sphaerium solidum. Our knowledge about the original benthic invertebrate fauna in the Oder before major anthropogenic impacts is poor. Detectable changes in the zoobenthic community of the river may be generally explained by changes in water quality, river-training, and immigration of new species. The present rating of the water quality of the Oder lies between a saprobic index of 1.8 (headwaters at Jakubcovice nad Odrou) and 2.2 (at Svinov/Ostrava), which corresponds to the quality classes ‘moderately polluted’ and ‘critically polluted’. As the Oder historically never was as heavily polluted as the Rhine or Elbe, some molluscs like T. fluviatilis, P. complanata, and U. tumidus occur in the Oder and never went extinct like in the Elbe. However, more sensitive species, especially some molluscs, stoneflies and mayflies, have

547

Chapter | 14 Rivers of the Central European Highlands and Plains

become extinct in the Oder because of poor water quality. The spread of some of those species listed as typical for the Oder would be seen as a positive sign towards a typical invertebrate assemblage. Besides water quality, river training has also contributed to the changes in the invertebrate community of the river. The construction of groynes and embankments provided habitats for lithophilic species such as Ancylus fluviatilis, B. tentaculata, and D. polymorpha. On the contrary, shortening and fixation of the riverbed has increased flow velocity and erosion, which in turn deteriorated habitat conditions on the river bottom. A total of 21 invasive invertebrates have been recorded (Table 14.2), which is low in comparison with the River Rhine with 30 invasive species. Most of these invasive species arrived in the river at the beginning of the 20th century, for example C. curvispinum, while others arrived later (e.g. G. tigrinus presumably around 1980). Since 2000, the amphipod D. villosus has been found in the Oder, which it had reached via the north German canal system after the completion of the Main-Danube canal in 1992. The cooling water filters of barges have been identified as major vectors, so that further invasions are likely. In contrast, the gender mussel Corbicula that had spread rapidly in the Rhine basin does not seem to spread further east into the sub-continental climate of the Oder system with its cold winter temperatures.

14.4.4. Management and Conservation 14.4.4.1 Economic Importance The Oder has been used early for navigation both in northsouth and east-west directions, as it has been connected early with the Elbe catchment via two canals, the Friedrich–Wilhelm Canal (Spree-Oder waterway, since 1668) and the Finow Canal since 1746. A navigable connection between the Oder and Vistula catchment has existed since 1774 with the opening of the Bydgoszcz (Bromberger) Canal. This 26km long canal connects the Warta tributary Note with the Vistula tributary Brda. This waterway between both river systems is of particular interest from a biogeographic point of view because the Vistula has two connections to the Dnjepr River, and thus to the Black Sea. There is a common floodplain area along the Vistula and Dnjepr headwaters near Svitaz and the Dnjepr–Bug canal (since 1775) between the Vistula tributary Bug and the Dnjepr tributary Pripjat. The first watermills on the Oder have been documented from the 12th century (Reynolds 1983). Early mill dams and fishing weirs impeded navigation in a way that in 1337 King Johann of Bohemia enacted the so called ‘king measure’, a 9.3-m wide minimum opening in all weirs and dams to allow navigation and fish migration along the Oder between Brzeg (Brieg, Rkm 198) and Krosno Odrzanskie (Krossen, Rkm 514) (Bekmann 1751). Although repeatedly confirmed, this edict has never been fully implemented. In the Silesian part of the Oder, seven weirs are mentioned for the year 1375, and 18 for 1550 (Uhlemann & Eckoldt 1998). When nearly the

TABLE 14.2 Invasive benthic invertebrates in the Oder, with geographic origin Species name Cordylophora caspia Dugesia tigrina Ferrissia wauteri Lithoglyphus naticoides Physella acuta Potamopyrgus antipodarum Viviparus viviparus Corbicula fluminea Dreissena polymorpha Branchiura sowerbyi Hemimysis anomala Limnomysis benedeni Echinogammarus ishnus Chelicorophium curvispinum Dikerogammarus villosus Dikerogammarus haemobaphes Pontogammarus robustoides Gammarus tigrinus Obesogammarus crassus Orconectes limosus Eriocheir sinensis

Original ecoregion Pontocaspis North America Southwest Europe Pontocaspis Southwest Europe New Zealand East-Europe Asia Pontocaspis South Asia Pontocaspis Pontocaspis Pontocaspis Pontocaspis Pontocaspis Pontocaspis Pontocaspis North America Pontocaspis North America East Asia

entire river came under Prussian administration in 1742, several meanders were cut off, the longest being the 21-km long cut-off between the villages G€ustebiese and Hohensaaten (1746–1753), which enabled the farming of the Oderbruch floodplain (920 km2) with its fertile soils (Uhlemann & Eckoldt 1998). In total, the main channel of the Oder has been shortened in the section between Rkm 27 and Rkm 666 from a length of 822 to 635 km by 1896. In the 19th century, the river channel was fixed and confined by the construction of 5432 perpendicular groynes and 263 km of shoreline embankments (Herrmann 1930). Further, the natural floodplain was reduced from 3709 to 859 km2 by extensive construction of dikes (Landesumweltamt Brandenburg 1997).

14.4.4.2 Conservation and Restoration In the lower Oder, floodplain areas were also diked but the polders created have always been flooded at least during winter. Under that extensive management regime, many features of unaltered floodplains have been preserved (Dohle et al. 1999). The German/Polish Lower Oder Valley International Park was established extending along 60 km river with an area of 105 km2 in Germany and 60 km2 in Poland. The branched river channels, remnants of the floodplain forest with black poplar, extensive sedge and reed stands, wet meadows and active floodplain areas offer habitats for the breeding, resting and overwintering of many bird species. In total, 161 bird species are breeding there, including, for example white-tailed eagle (Haliaeetus albicilla), osprey (Pandion haliaetus), lesser spotted eagle (Aquila pomarina),

548

goosander (Mergus merganser), spotted crake (Porzana porzana), corn crake (Crex crex), terns, and bluethroat (Luscinia svecica). An especially rare species is the aquatic warbler (Acrocephalus paludicola), a migratory songbird breeding in short sedge beds, which is endangered globally and has its westernmost breeding population on the lower Oder. In autumn, the park regularly harbours 150,000 individuals of migrating geese, duck and swans, as well as 13,000 cranes. During the great Oder flood in August 1997, many fishes, amphibians, birds and mammals living in the Oder National Park were washed away, could not reproduce, or were eaten by predators when fleeing from the rising waters. After the flooding receded, mass concentrations of birds of prey, herons and wading birds were observed, for example 40 whitetailed eagles were seen in the park. However, the event was not catastrophic for the park, but renewed habitats and eventually sustained populations of some riverine and floodplain species, for example in fish (Bischoff & Wolter 2001). The Warta Mouth (Ujscie Warty) National Park covers an area of 80 km2 of mostly grassland vegetation mixed with alluvial willow stands. The southern part of the park near the village of Sło nsk is subject to a water-level amplitude of up to 4 m. The park harbours species typical of river corridors such as the Baltic toadflax (Linaria loeselii), the umbelliferous plant Cnidium dubium, elk, beaver, otter, and 254 bird species of which 174 are breeding. In autumn, up to 200,000 migrating birds may temporarily concentrate there. The park is embedded in a highly forested landscape to the north, east and south, which facilitates movement of larger species to neighbouring parks like Drawa National Park. Like other large European rivers, the Oder has been substantially modified by damming, regulation and other river engineering works. Because the lower Oder forms the border between Poland and Germany, intensive development was limited so that some typical features of large rivers have been preserved. On the other side, the Oder suffers along most of its length from significant inputs of wastewater and diffuse inputs of organic contaminants, nutrients, and heavy metals. The lower Oder and Warta are still free-flowing and are potential sites for the re-introduction of migratory fishes such as salmon and sturgeon. However, such efforts conflict with planned river training works to improve navigation on the Oder during periods of low flow.

14.5. EM The Em River, with a catchment area of 4460 km2, is the largest river in southeast Sweden (river mouth at 63 330 N, 15 420 E). The Em originates in the highlands of Smaland (330 m asl), just north of Lake Storasj€ on near the city N€assj€ o. It flows approximately 220 km before entering the Baltic Sea near the city Em at Kalmar Sound. The Em valley is one of the most valuable watersheds in Sweden, as it is of great national interest for nature preservation, cultural history, and outdoor recreation. The lower river contains

PART | I Rivers of Europe

wetland types that are rare in the European boreal region. The river is well known for its population of European catfish and fast growing Sea trout, and meandering river sections provide valuable habitats for otter. Early settlements dating back 6000 years have been found near large lakes and along the river. With the onset of agriculture and livestock breeding, settlements expanded and moved to higher areas in the landscape some 2000–3000 years ago. The cattle grazed in large wetlands along the river, where flooding by the river provided nutrients that supported good plant growth. Hay was harvested from meadows as a common way to get winter fodder for cattle, almost until today. Before industrialization in the 19th century and urbanization in the 20th century, humans lived from agriculture and forestry in villages or on small farms. From 1750 to 1880 the population increased markedly (by 135%), and subsequently large land areas like meadows, bogs, and marshes were transformed into agricultural fields, and lake water tables were lowered to gain new land. The Em has been an important waterway for transportation, both in summer as well as on the ice cover in winter. Hence, the river has been straightened for timber transport, watermills, sawmills, and power stations. The lower river (county of Kalmar) was declared as a general timber route in 1897, being first used in 1912. About 25 000 m3 of timber was floated down the river each year, and this business lasted until 1963. Timber was also transported on smaller streams, the S€allevadsan, Lillan, and Silveran in particular. Earlier, every village in forested areas had a watermill, thus thousands of watermills existed in the Em catchment. Most of these have disappeared by the 20th century. Today, the river is dammed in >100 locations (Photo 14.6). In total, the streams and rivers in the catchment had 292 fish migration barriers in the mid 1990s.

14.5.1. Physiography, Climate, and Land use The river basin has a hilly topography with sediment filled valleys. Bedrock in the catchment is dominated by poorly buffered granites with low nutrient content, which is resistant to erosion and results in acidic soils. Sedimentary bedrock occurs in the westernmost part of the basin, thus soils are generally nutrient rich, calcareous, and more fertile compared to the east. In the east, porphyric bedrock can be found, and the soil layer is thin or even absent in some areas. Quaternary deposits covering the valley floor are dominated by tills, glaciofluvial material, and are rich in clay or sandy moraines suitable for agriculture. Mean annual air temperature ranges from 3 C in the upper catchment to 7 C in the lower part. The coldest month is December with mean temperatures ranging from 0 C near the coast to 2 C in the upper basin. The warmest month is July, averaging 16–18 C. Annual precipitation peaks in June and July. Freeze-up of lakes in the catchment begins around mid December to January and ice break-up usually

Chapter | 14 Rivers of the Central European Highlands and Plains

549

PHOTO 14.6 Em River with J€arnforsens power plant at J€arnforsen, municipality of Hultsfred, county of Kalmar. The dam is a migration barrier, for example for brown trout (Photo: J. Bergengren).

starts around mid April. The growing season lasts 140–180 days in the north and 180–210 days in the south (Nordic Council of Ministers 1984, Gustafsson & Ahlen 1996). The catchment is located in a mixed deciduous forest region (Illies 1963). This biogeographical region is characterized by mostly spruce and pine forest in the north and deciduous forest in the south. The Em catchment is primarily covered by forest, with coniferous forest dominating at 69%, followed by mixed deciduous forest (19%). Only 12% of the forests consist of pure deciduous tree species, and riparian vegetation is dominated by coniferous trees such as spruce, pine, as well as Silver birch, and Black alder.

14.5.2. Geomorphology, Hydrology, and Biogeochemistry In the Em catchment, six large lakes can be found along the mainstem of the river, that is Storasj€ on, Vallsj€ on, Tjurken, Grumlan, Norrasj€ on, and Fl€ ogen, together with 89 other lakes. The main tributaries of the Em are the Solgenan, Linnean, Silveran, Brusaan, S€allevadsan, Paulistr€omsan, Gnyltan, Saljenan, Gardvedaan, Maran, Moran, N€otan, € Tjustaan, and Lillan. The upper tributaries for example Ovre € had a maximum Solgenan, Kroppan, and Silveran Ovre, discharge <10 m3/s between 1992 and 1997. Tributaries in the middle catchment, for example Silveran Nedre, and Gardvedaan, had a maximum discharge <16 m3/s between 1992 and 1997. The mean discharge in the lower catchment near Emsfors at the river mouth was 30 m3/s between 1926 and 1975. During this period the lowest discharge was 2 m3/s

and the highest was 270 m3/s (UNESCO 2004). Seasonally, the flow regime follows a general pattern with highest discharge in April after snowmelt and low discharge during summer from July to September. Seasonal variation in flow is quite marked, so that large areas along the river are flooded every year. This large variation in flow creates problems for the biota and people living in the valley. Most tributaries within the catchment are slow flowing (<0.2 m/s), and turbulent or fast-flow sections (>0.7 m/s) are rare. Bed sediments in the Em main channel as well as its tributaries are dominated by sand, followed by cobble (5– 50%). This mix of hard and soft sediments is usually supplemented by vegetation cover, mostly by submerged and floating vegetation and phytobenthos. Pebble or rocky sediments as well as dead wood are relatively rare within the catchment. The load of suspended sediments is relatively low in the river and tributaries, ranging from 0.7 mg/L (Silveran in 2006) to 5.6 mg/L (upper Em in 2006). Suspended loads usually peak in July in the lower and middle river. The river as well as Silveran and Solgenan are generally classified as mesohumic (61 mg Pt/L in Solgenan to 86 mg Pt/L in the upper river). Seasonally, the humic content in the streams is usually highest early in the year due to runoff, and is lowest in September. The humic content in the river is a growing problem, as the water colour has intensified by 100% in the last 10–15 years. Mean water temperature in the Em ranges from 0.5 C in winter to 18–20 C in July, with the lowest temperatures typically occurring in the upper river. Long-term records show a slight increase in water temperature in the lower and upper river as well as in Silveran since the early 1990s. However, a decrease in water temperature has been

550

PART | I Rivers of Europe

recorded in Solgean during the last 20 years. Concentrations of chloride and sulphate are low in the Em and the tributaries Silveran and Solgean, ranging 4.8 mg/L (Silveran 2004) to 15.1 mg/L (Solgean 2003) for chloride and 6.6 mg/L (Silveran 2005) to 18.5 mg/L (lower Em 1997) for sulphate. During the last 9 years, both chloride and sulphate concentrations have markedly decreased in the lower and upper river as well as in Silveran. Total ion concentration, measured as conductivity, has also declined during the past 16 years in all streams except for Silveran. The Em and its tributaries Solgenan and Silveran can be classified as mesotrophic to eutrophic, as they exhibit annual averages of 12–53 mg/L total phosphorous and 503–1389 mg/L total nitrogen. The Solgenan has slightly higher total phosphorous content than the Em, but nitrogen content is on average higher in the river than in the tributaries. Concentrations of total phosphorous and nitrogen generally peak in summer. Long-term trends show an increase in nutrient content in the lower river, but a de crease in the middle part since the mid 1980s. In Solgean, total nitrogen has strongly increased during the last 30 years. Saturation of stream water with dissolved oxygen (DO) ranges from 95% to 98% in the Em and its tributar ies Silveran and Solgenan in December and January, and 81–85% in July and August.

14.5.3. Aquatic and Riparian Biodiversity Riparian zones are dominated by wetlands, especially in the lower river. Here, the flora is rich and more continental than in the upper catchment. The Alpine bastard toadflax (Thesium alpinum), a national redlist species, is found in this area. Royal fern (Osmunda regalis), hemp agrimony (Eupatorium cannabinum), flowering rush (Butomus umbellatus), the nationally redlisted wood fescue (Festuca altissima) and great yellowcress (Rorippa amphibia) are relatively common plants along the river. The grey cinquefoil species Potentilla arenaria also has its largest growing site here. Cryptogam species, for instance, Usnea florida, Leptogium cyanescens, Dimerella lutea, and Dichelyma capillaceum (EU Habitats directive species) are common in the wetlands (Olevall et al. 2002). In total, 96 species of higher aquatic plants can be found along the river (Sandin et al. 2003). Water plants are generally sparse and mostly found at sites impacted by nutrient point sources and lack of canopy cover. In the northern and western part of the catchment, mosses like Fontinalis spp. dominate, whereas the eastern and middle parts are dominated by submergent and emergen higher plants. Here, Ranunculus flammula, Potamogeton polygonifolius, Littorella uniflora, and especially Batrachospermum spp. dominate. In the middle northern part, the Yellow pond-lily (Nuphar lutea) is the prevailing plant. Recently, two rare aquatic plants have been found in the catchment, that is the slender naiad (Najas flexilis) in Lake S€ odra Vixen and Nitella

mucronata in Lake Norra Vixen. At some western sites, the neophyte species Canadian waterweed (Elodea canadensis) occurs. Since the Em and its tributaries are generally small streams, phytoplankton growth is low. Red and green algae as well as Cyanobacteria are common in the main channel and tributaries. Diatoms have the highest algae taxa richness and abundance; the most common includes Eunotia and Achnanthes genera as well as Fragilaria capucina, Gomphonema parvulum, Tabellaria flocculosa and Brachysira neoexilis (Sandin et al. 2003). A study of phytoplankton assemblages in 10 lakes within the catchment showed that Cryptophyceae and diatoms were most common. Diatom communities consist mainly of Aulacoseira sp., T. flocculosa, Rhizosolenia longiseta, and Fragilaria spp., whereas Cryptomonas sp. and Chromonas sp. represent the cryptophycean group (Sundberg & Ericsson 2005). Dinophyceans, almost solely represented by Peridinium, Ceratium, and Gymnodinium spp. as well as Cyanobacteria comprised 10% of the total community composition in the lakes. Filamentous, nitrogen-fixing species such as Anabaena sp. and Aphanizomenon sp. as well as potentially toxic and floating Microcystis sp. are common blue-green algae. Snowella spp. and Planktothrix mougeotii also occur in some lakes, especially in Lake Solgen and Lake S€odra Vixen, both have relatively high numbers of Cyanobacteria. Green algae are frequently represented by Pediastrum and Scenedesmus spp., and Dinobryon, Mallomonas, and Synura taxa are the most common gold algae. Nostoc zetterstedtii, an indicator of nutrient poor clear water lakes, has one of its largest populations in the Em catchment. The nuisance flagellate Gonyostomum semen is common in the lakes and comprises 11% of the total phytoplankton biomass. G. semen is invasive in mesotrophic Scandinavian lakes and may form dense blooms in humic lakes with high nutrient content. In most lakes this species is not abundant, but in Lake Grumlan about 70% of total phytoplankton biomass consists of G. semen, and can lead to skin reactions in humans. Long-term studies showed that annual total phytoplankton biomass and number of taxa varied little during the last 15 years, ranging from about 0.05–6 mg/L biomass and 20–55 phytoplankton taxa (Sundberg & Ericsson 2005). Zoobenthos in some sections of the river have high diversity. In a study at five sites (three in the mainstem, two in Silveran, and one in Gardvedaan) (Bostr€om 2005), two sites had high zoobenthos richness compared with a large dataset from southern Sweden. The five sites harboured 43–66 taxa (near the river mouth) and 45–61 taxa (at Kungsbron in the main stem). In 2003, a large inventory of 27 sites was made (Bostr€om & Engdahl 2003), where 9 out of 11 sites sampled in the mainstem contained high taxa richness (41–58 taxa). A number of redlisted and rare species also were found in these studies, for example the amphipod Gammarus lacustris, the odonate Calopteryx splendens, the ephemeropterans Baetis buceratus, Rithrogena germanica, the trichopterans Brachycentrus subnubilus, H. contubernalis, Oecetis notata,

Chapter | 14 Rivers of the Central European Highlands and Plains

P. pusilla, Adicella reducta, Ceraclea nigronervosa, the hemipteran Aphelocheirus aestevalis, the coleopterans Stenelmis canaliculata, Oulimnius troglodytes, Normandia nitens, the dipteran Ibisia marginata, and the gastropods Gyraulus crista, Marstoniopsis scholtzi, Bithynia leachii. In the 22 lake littoral zones studied in 2003, the trichopterans Goera pilosa and Notidobia ciliari as well as the gastropod Valvata piscinalis were found. In the river, seven large mussel species have been found such as the redlisted and protected freshwater pearl mussel (Margaritifera margaritifera) and the thick-shelled river mussel Unio crassus as well as the depressed river mussel (Pseudanodonta complanata). The river also has four other large mussel species, that is painter’s mussel (Unio pictorum), the duck mussel (Anodonta anatina), the swan mussel (Anodonta cygnea), and the swollen river mussel (Unio tumidus). The Noble crayfish as well as the introduced signal crayfish (Pacifastacus leniusculus) are also found in the river. The ichthyofauna of the Em comprises over 30 fish species, including salmon, asp, chub, and trout. The Em is considered the most important water in Scandinavia for the European catfish. The European catfish, requiring a water temperature of 22 C for spawning, is a relict species from a warmer climate period in Sweden and lives on the edge of its climatic range. Its population has declined significantly over the last century in Scandinavia. Today, the catfish occurs only in the lower river, where most are found in quiet parts below the power station dams Karlshammar and Emsfors near the river mouth.Originally, the Em offered extraordinary suitable habitats for Salmon and migratory Sea trout. In the early years of the last century, these fish occurred as high up as Vetlanda in the middle and western part of the catchment. Today, power station dams hinder spawning fish from reaching their original breeding grounds, decreasing access to only 10% of the river length. A recent study (Andersson & Nilsson 2004) showed that biomass as well as the number of sea trout decreased during the last years, although this fish is still dominant in waters of the catchment (County Administrative Board of J€ onk€ oping 2006a). In surveys, cyprinids have been the most common fish in the Em and its tributaries, and include Minnow, Roach, and Tench. Other noteworthy fishes are burbot, Brook lamprey and Alpine bullhead, and the globally redlisted Asp.

14.5.4. Management and Conservation Water of the Em is abstracted by a number of industries, several municipalities and farmers. Fourty-five dams used for hydropower production are found in the upper catchment. During summer, river discharge can be too low for drinking water supply, industry and irrigation purposes, as well as for fish migration. Flooding of floodplains and farmlands regularly occurs during snowmelt. The Swedish Meteorological and Hydrological Institute therefore implemented a water

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management plan for the river to regulate its flow by controlling the outflow of dams and to guarantee a minimum flow of 4.5 m3/s near the mouth. Since the early 19th century, the lower river has been affected by the release of cadmium, nickel and lead from a battery factory 20 km upstream of the mouth. Monitoring programs to reduce pollution levels were implemented at the end of the 1970s, and the heavy metal content has decreased, although cadmium levels are still high. Persistent organic compounds (PCBs) contaminate the catchment, especially the upper basin (Johansson 1996; Olevall et al. 2002). While some factories have been closed for >20 years, and local restoration projects have been carried out, high levels of metal and PCBs are still found locally in river sediments. One of the largest sources of PCBs is contaminated sediments still present in rivers and lakes, especially in Lake J€arnsj€o, which were heavily polluted by emissions from a paper mill in the early 1990s. PCB is considered to be the major factor for the dramatic decline of the otter population in the Em catchment, as in the rest of Europe. In addition, hydromorphological alterations exert major impacts on river biota. Water control measures conducted in the late 19th century to create additional agricultural land, water pollution and the construction of dams have probably contributed to the decline of the European catfish. The decrease in populations of salmon and migratory Sea trout is probably related to the dam of the H€ogsby power station that forms the upper limit of migration in the main channel (County Administrative Board of J€onk€oping 2006a). The salmon population in the lower catchment is one of the few remaining stocks south of the Dal€alven River (middle Sweden) which has a significantly natural reproducing population (County Administrative Board of J€onk€oping 2006b).

14.5.5. Perspectives The Em River is of national importance for nature conservation, as it is a designated Ramsar site since 1999. Part of the catchment is a European Natura 2000 site, and it contains one of the largest continuous wetlands in Sweden. The Em catchment harbours a high level of both plant and animal diversity. There are also good conditions for recreation and tourism, especially sport fishing in the river. The main environmental problems in the catchment relate to water use, as hydropower plants and irrigation hinder fish migration, and historic pollution by heavy metals and PCBs are evident, especially in lake sediments. In 2002, a water management plan was set up for the catchment to guarantee a minimum flow of 4.5 m3/s at river mouth. Environmental and economic sustainability in the catchment is maintained through the River Em Catchment Management Association, including municipalities, the county administrative boards, some 200 landowners, and NGOs.

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14.6. SKJERN The Skjern River originates in glacial moraines that cover the center of the Danish Peninsula of Jutland, then flows West before entering the Ringkjøbing Fjord estuary and finally the North Sea. The Skjern is the largest river in Denmark in terms of discharge, draining an area of 2490 km2 with a length of 94 km from its source in Tinnet. The river network including tributaries is 1526 km long. In the 20th century, the original diverse fauna and flora of Danish streams declined dramatically due to pollution by wastewater from cities, industry and fish farms, and by channelization that aimed to improve drainage of agricultural land. During the 1970s to early 1980s, increasing public awareness of water pollution problems lead to a rapid decrease in discharges of organic matter to surface waters from point sources (Kronvang et al. 2006). Since the mid 1980s, nitrogen and phosphorus loadings of Danish surface waters have been significantly reduced (Kronvang et al. 2005). Since the 1990s, considerable efforts have been made to improve habitat diversity in streams by introducing more environmentally friendly regulations and implementing stream restoration projects. Some of these projects have been carried out locally on short reaches of streams, for example providing spawning gravel for fish. The continuity in some streams was re-established, while in larger projects the restoration included both the stream and adjacent riparian areas, for example by remeandering streams. A large restoration project was conducted by the National Forest and Nature Agency in the lower Skjern.

14.6.1. Biogeographic Setting Denmark, which lies completely within one ecoregion, is a small lowland country with the distance of any location to the seacoast never exceeding 50 km. For this reason, even the largest streams in Denmark are relatively small. The freshwater flora and fauna is generally species poor when compared to other areas within this ecoregion, partly because of dispersal barriers caused by the sea. The glacial history of Denmark is reflected in the dispersal of freshwater organisms and partly explains the higher diversity in western Jutland that remained ice free during the last glaciation 10,000 years ago.

14.6.2. Physiography, Climate, and Land Use Three types of landscapes can be identified in the Skjern catchment, including moraine hills, washout plains and postglacial deposits The washout plains, which consist of deposited sand and gravel, appear as heath plains acting as wider river valleys between old moraine hills. The major river flowing through this landscape is the Skjern. Soils in Danish river valleys are generally dominated by deposits of organic origin, equaling an area of 6700 km2 (15% of Denmark’s

PART | I Rivers of Europe

area). In the Skjern valley, peat as well as fine particulate organic matter and diatom frustules deposited in shallow waters, making up the so-called gytja layers, are found to a depth of 10 m. Historically, these soils have been extensively used because when drained they provide excellent nutrient-rich soils for agriculture. In the entire catchment, soils are dominated by sand (70–80%), 15–20% is sandy loam and 4–8% consist of humic soils. The average yearly measured precipitation in the catchment is 89.2 cm/year (1961–1990) compared with 71.2 cm/ year for the entire country. This corresponds to an actual precipitation reaching the catchment surface of 108 cm/year. The climate is oceanic temperate (annual mean temperature 7.6 C ), so that winters are fairly mild (coldest monthly average temperature 0 C) and wet, whereas summers are cold (warmest monthly average 15 C) with high levels of precipitation. Air temperatures have been increasing 1.5 C since 1874 with half of this increase occurring since the late 1980s. The floodplains of the Skjern River have been farmed for centuries. The meadows provided nutrient-rich farmland in a part of Denmark otherwise dominated by leached sandy soils of little value. The frequent flooding of the river regularly supplied nutrients and organic matter to meadows and fields. Livestock fed on fresh grass in the summer and in winter on hay harvested from the meadows. Farming in this period was largely sustainable. The purchase of winter feed for livestock is a relatively recent phenomenon, and the use of fodder turnips in the region did not start until the turn of the last century. The unpredictability of floods often ruined hay making, so that the river was regulated for the first time in 1901–1902 to reduce flooding. The lower main channel was straightened and summer dykes were built. Despite these efforts, farming was still difficult in large parts of catchment due to wet soils and occasional flooding. Hence, in 1962 the largest drainage project in Denmark was initiated, which comprised the straightening of the lower 20 km of the main channel from the town of Borris to the estuary Ringkøbing Fjord (Figure 14.10). The regulation took 6 years to complete at a total cost that today would correspond to EUR 27 million. Flooding was prevented by large dykes and the groundwater table was lowered by installing pumping stations and drainage ditches. After the regulation, 4000 ha of arable farmland resulted from what were previously meadows and wetlands. The area covered by wetlands was reduced to only 430 ha by the end of 1990s (Svendsen & Hansen 1997). In 1987 the Danish Parliament decided to restore the lower Skjern and its valley. The objectives of the restoration were (1) to restore the nutrient retention capacity of the river and its valley, (2) to restore an internationally valuable wetland and habitats for migratory birds, (3) to promote fisheries in the downstream estuary, and (4) to increase the recreational and tourist values of the area. Most of the project area (19.5 km2) was purchased from the farmers by the Danish Forest and Nature Agency. Local authorities, trade

Chapter | 14 Rivers of the Central European Highlands and Plains

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FIGURE 14.10 The course of the lower 20 km of the River Skjern (left) and the extent of meadows and wetlands along the Skjern (right) mapped in 1871 and after river regulation in 1987.

organisations and interest groups covering outdoor life and environmental protection participated in the entire decision process of the project. The restoration project included remeandering of the river and re-establishment of natural water levels and water level fluctuations in the river and its valley. The main purpose was to enhance living conditions for plants and animals and safeguard high water quality in the river and estuary by enhancing nutrient retention. Construction was initiated in June 1999 and was mostly finished by autumn 2002 with a total cost of EUR 37.7 million; 3.3 million were

granted by the EU LIFE program. This corresponds approximately to the costs of land reclamation in the 1960s. The main activities were the excavation of a new meandering river channel that increased channel length from 19 km to 26 km, the removal of existing dykes, the filling of the old channelised reaches, and the construction of bridges and paths. Whenever possible, one of the original riverbanks was used for the restored river channel. In total, 2.7 million m3 of soil was moved and 40 km of restored river channel was established (Photo 14.7).

PHOTO 14.7 Flooded floodplain of the lower Skjern near its mouth. The bended river course that was newly built in the restoration project, and some remnants of the former straightened channel can be seen (Photo: Poul Toft).

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PART | I Rivers of Europe

14.6.3. Geomorphology, Hydrology and Biogeochemistry Before the first regulation in 1901–1902, the Skjern meandered freely across the floodplain. Its width was between 65 and 100 m and the slope was 20 cm/km in the lower reaches (Rambusch 1900). Near the sea, the river formed a delta with several side channels flowing parallel to the mainstem. After the large-scale regulation in 1968, the width of the river channel was fixed at 45 m at the downstream reach below the Omme River confluence and 30 m at the reach below Borris. By installing embankments, the bank height was raised to 3.5–3.8 m along the regulated reach. With the increase in width and bank height, bankfull discharge increased fivefold at the upstream reach at Borris to 178 m3/ and fourfold to 144 m3/s at the downstream reach. After construction of the new river channel comprising 46 new meanders, average cross-sectional area was reduced by 20– 30%, the dominant depth interval decreased from 100–160 to 40–140 cm (Figure 14.11), and current velocities increased from 30–40 cm/s to around 30–60 cm/s in the middle of the channel. Newly excavated cross sections of the channel were now subject to significant fluvial dynamics. The Skjern is a typical lowland, low energy river with a mean discharge at its mouth of 35.6 m3/s (1920–95), ranging between 35.6 m3/s (1929) and 319 m3/s (extreme snowmelt event in 1970). As most of the catchment is builtup by sandy deposits, most precipitation infiltrates. Hence, the river is mostly fed by groundwater and shows a relatively mitigated flow regime, with minimum flows rarely less than half of mean flow. Mean flow velocity is 0.49 m/s (measured at Ahlergaarde, 1994–1998). In the period from 1925 to 1995, mean discharge increased significantly (Larsen et al. 2005), likely explained by the increase in average precipitation of 0.1 cm/year since 1874 (Cappelen 2007), increased tile drainage and increase in impervious areas (roads, towns). Annual average river temperature is 8 C, and typically ranging during the year between 2 and 16 C. The average (1965–1995) annual suspended sediment load in the river is 5.0 t km2 yr1 (Andersen & Svendsen 1997) compared to 9.5 t km2 yr1 on average in 14 Danish rivers (Kronvang et al. 2006). The suspended matter is fine-grained, and is an important carrier of environmentally harmful adsorbed substances such as phosphorus, heavy metals, and pesticides. The movement of coarse sediment on the stream bed (bed load), averaged during the same period, was 6.5 t km2 yr1. Nitrate transport in the river measured at Ahlergaarde was 1500 t/yr from 1979 to 1995. Nitrate constitutes 80% of the nitrogen in transport. Despite the reduction of nitrate emissions from sewage treatment plants, there was a significant increase in nitrate from 1979 to 1995, reflecting that the main source of nitrogen was diffuse pollution from farmlands. In contrast to nitrogen, phosphorous transport was halved in the same period from around. 80 to 40 t/yr, corresponding to a concentration of 70–80 mg P/L and reflecting the decrease in sewage inputs. Phosphorous levels

FIGURE 14.11 Example of the changes to the cross-sectional profiles in Skjern River. The cross sectional area has generally decreased by approximately 30%. The morphology of the profiles has changed from the constructed rectangular shape to a more natural physical appearance.

in the river in the 1990s were only half of those found in other Danish streams in an agricultural landscape, partly explained by the presence of ochre sediments (FeO(OH)) within the river that result in the formation of ferrous phosphate (FePO4) particles that settle in the channel. Channelisation of the lower Skjern resulted in large amounts of soluble iron (85 000 tons of Fe between 1966 and 1995) being released when the pyrite rich soils in the floodplain were drained and oxidized. This was paralleled by soil shrinking of 1.5 m as organic matter decomposed and was further compressed by heavy farm machinery that rendered soils wetter and more anoxic. After completion of the restoration project, monitoring of the concentrations of nitrogen and phosphorus showed that the retention of N and P is likely to be <10% of the total riverine input to the project area. No effect of the restoration of the river channel could be detected so far. Approximately 4.5 km2 of the river valley will be flooded regularly after restoration, equaling around one month per year. Sedimentation on the floodplain during flooding was measured in winter by means of artificial grass mats, and sedimentation was estimated to add 8 g/m2 total phosphorous and 280 g/m2 of total nitrogen. An annual basis, it is estimated that typical deposition is 5 t P/yr and 13 t N/yr (Ovesen & Damgaard 2005). In the adjacent permanent Lake Hestholm and in flooded parts of the river valley, nitrate from the river water is denitrified to atmospheric nitrogen, which is estimated at 45 tons N in flooded riparian areas and 150 tons N in Lake Hestholm in normal years (Kronvang et al. 2001; Jessen & Andersen 2005).

14.6.4. Aquatic and Riparian Biodiversity 14.6.4.1 Terrestrial Fauna Historically, the lower catchment harboured a rich bird diversity because of the extensive reed beds and wetlands that occurred in the floodplain. Despite changes due to drainage measures, the area remained a bird protection area of

Chapter | 14 Rivers of the Central European Highlands and Plains

international importance as an integral part of Ringkjøbing estuary, which is protected by the Ramsar Convention on wetlands since 1977. It was estimated that >1% of the total international population of whistling swan, whooper swan and pink-footed goose rested in the Skjern River floodplain (Nøhr 1988), and the area was identified as the main resting area for dotterel (Charadrius morinellas) in north Europe. In 1994, 124 bird species were registered in the lower Skjern River valley. Of the 17 species of mammals registered for the Skjern River valley, otter is a key species listed in the Danish Red Book. Prior to the floodplain drainage, the river was considered the primary otter locality in Denmark. In surveys in 1979/1980 and 1991 otters were registered only at a few locations along the river (Madsen et al. 1992). Since then, a marked increase in the occurrence of otter in the restored area has been documented, which parallels the general spreading of otter from northwest Jutland to the rest of the Jutland Peninsula (Madsen et al. 2005). In 1976, eight species of amphibians were found in the catchment as well as all five Danish reptiles (Fog 1993). Habitat loss from extensive drainage of rivers, wetlands and ponds in the catchment probably has had a detrimental impact on both amphibians and reptiles. It appears that the restoration project has improved both the breeding and terrestrial habitats for Common frog and Moor frog, whereas the response of common toad and natterjack toad to restoration remains unclear (Madsen et al. 2005). The habitat improvements are primarily due to the creation of shallow ponds surrounded by non-cultivated land.

14.6.4.2 Terrestrial Vegetation Prior to the drainage, the lower catchment had a high diversity of plants on the wet meadows (Baagøe & Ravn 1895; Mentz 1906). The differences in soil humidity created a range of different habitats and hence a variety of plant communities. The wet meadows were dominated by smooth black sedge (Carex acuta), beaked sedge (Carex rostrata), creeping bent grass (Agrostis stolonifera) and reed sweetgrass (Glyceria maxima), and in open stagnant waters the floating water-plantain (Luronium natans) occurred, but is today highly endangered. This changed completely in the 20th century when meadows were converted into arable farmland. As a consequence, the original flora was lost with the exception of a few areas such as the two bogs Raadensig kær and Albæk, but which were negatively affected by draining and fertilization of adjacent lands. A number of rare plant species such as the water lobelia (Lobelia dortmanna), whitish bladderwort (Utricularia ochroleuca), slender cottongrass (Eriophorum gracile) and string sedge (Carex chordorrhiza) also were impacted. After the restoration project, most of the valley was converted back into meadows and wetlands. The area is grazed by cattle to prevent reed stands or black alder and willow forests from taking over. In total,

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an area of 12 km2 is grazed by 800 cattle, while an additional 3 km2 are mechanically cut. There is an on-going evaluation of the grazing pressure targeted towards achieving an attractive breeding habitat for birds characteristic of meadow ecosystems and an optimal habitat for migratory water birds, according to the designation of the Skjern River valley as a Natura-2000 area.

14.6.4.3 Fish Based on large-scale fish surveys in the 1980–1990s, 26 fish species were found in the Skjern River. In Denmark, Siberian sculpin, a IUCN red list species, is only found in the Skjern catchment. Similarly, the Skjern harbours the largest natural populations of grayling and salmon in Denmark. Common whitefish occurs in Jutland and can be found in high densities in the Skjern. Two non-native fish, rainbow trout and brook trout, were found in the river and were probably introduced by accidental releases from Denmark’s 400 fish farms. The Skjern is one of five Danish rivers where original salmon populations still exist, as shown by comparisons of DNA analyses of preserved salmon scales from fish caught in 1913, 1930s and 1950s (Nielsen et al. 1997). In 1989, the number of spawning salmon was estimated at 125–2000 ind./ year (Dieperink & Wegner 1989). By rod catches, about 300–500 salmon were caught per year in the 1950s, while this number decreased to 10 per year from 1977 to 1985 (Miljøstyrelsen 1994). Sea trout followed the same downward trend as salmon, with rod catches decreasing substantially from 500–700 to 50 per year in the same period. The reasons for the decline in salmon populations in the catchment are a general degradation in water quality as a consequence of high concentrations of ochre, habitat loss through dredging, channelisation, and fishing pressure, especially in the estuary. To reduce fishing pressure, commercial fishing in the estuary and river was substantially restricted since 1996, and fishing is now prohibited during winter in the river. Over the last 20 years, the number of salmon returning from the sea to the Skjern to spawn has increased from about 100 to 1000 salmon annually (Figure 14.12). This increase was primarily caused by stocking of juveniles and by restrictions on commercial fishing

FIGURE 14.12 Annual spawning migration of salmon into Skjern River from 1984 to 2004 (modified from Koed et al. 2006).

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rather than by the restoration project. The number of migrating salmon smolts was estimated at 5800 and 26 200 in 2000 and 2002, respectively, and for trout smolts at 7100 and 8500 using tagging-recapture methods (Koed et al. 2006). The mortality of radio-tagged smolts during their migration in the Skjern was estimated at 50% for salmon and 25% for brown trout. Great cormorants and grey herons caused, respectively, 16% and 14% of the mortality of radio-tagged salmon and trout smolts in 2002.

14.6.4.4 Aquatic Macroinvertebrates The first recorded macroinvertebrates samples from the Skjern can be dated back to 1912. When comparing samples through time, there has been a marked change in taxonomic composition (Jensen 1995). Three species of mayflies (Ephemeralla ignita, Caenis rivulorum and Heptagenia fuscogrisea) have become more abundant over time, while all other mayfly species have declined and four species have not been recorded since 1957 (Baetis buceratus, B. digitatus, Paraleptophlebia werneri and Siphlonurus alternatus). A similar trend can be seen with respect to stoneflies where Isoperla grammatica and Taeniopteryx nebulosa have become increasingly more abundant, while most other species have decreased in abundance (e.g. Perlodes microcephala) or completey disappeared (Siphonoperla burmeisteri). The decline in populations of mayflies and stoneflies likely reflect the increased pollution and habitat degradation that occurred in the Skjern through the 20th century. Despite these species declines and losses, the Skjern is today considered to harbour one of the most taxa-rich macroinvertebrate faunas in Denmark. Mayflies (Ephemeroptera) and stoneflies (Plecoptera), and to some degree caddisflies (Trichoptera), include species that are rare or absent from other parts of the country. Several species such as the mayfly Brachycercus harrisella and the stonefly Isoptena serricornis have good populations in the river but are threatened by extinction at a national level. The Skjern is also the main locality for the green club-tailed dragonfly (Ophiogomphus cecilia). After completion of the restoration project, the shortterm effects of restoration on river habitats, macrophytes and macroinvertebrates were examined in surveys within the restored section of the river, while upstream reaches that remained unaltered were used as a control. Two years after the restoration, macroinvertebrate diversity and abundance had reached pre-restoration levels. Species richness was 63 before the restoration in 2000 and 76 after the restoration in 2003. Before restoration, blackflies (Simuliidae) was the dominant taxon, and about twofold more abundant than non-biting midges (Chironomidae). In 2003, the three most dominant taxa, Orthocladiinae, the caddisfly Brachycentrus maculatus, and the mayfly Heptagenia sulphurea, were almost equally abundant. The riffle beetle Elmis aenea and the mayflies Baetis spp. (six species including the dominant

PART | I Rivers of Europe

B. rhodani and B. niger) and Heptageniidae (two genera and five species including the dominant Kageronia fuscogrisea, H. sulphurea, and H. flava) increased in numbers after the restoration.

14.6.4.5 Aquatic Macrophytes Most streams in the catchment are vegetated by emergent and submergent macrophytes. Of these, the Atlantic/subatlantic species Flowing water-plantain and the river waterDropworth are both nationally and internationally regarded as being endangered and have their main Danish populations in the Skjern River. Historically, river water-dropworth occurred in most reaches in the lower river (Baagøe & Ravn 1895). After large-scale regulation in the 1960s, river waterdropworth was lost from the mainstem but remained in tributaries. Similarly, the number of Pondweed species found in the lower river declined from 13 species in the 1890s to only two in the 1970s (Wiberg-Larsen 1978). The decline of Pondweed species has been a general trend in Danish rivers and can be directly related to eutrophication, disturbance by channelisation, and weed cutting in channels (Riis & SandJensen 2006). After restoration, the species richness of aquatic macrophytes increased from 28 in 2000 to 40 in 2003. Reed Sweet-grass and Floating Sweet-grass and reed dominated the macrophyte community before restoration. The re-meandered channel and the edge habitat were dominated by Canadian waterweed and burreed (Sparganium emersum).

14.6.5. Perspective The history of the Skjern River and its catchment shows similarities to the majority of streams and rivers in the northern lowlands of Europe. Large-scale changes in land use have increased the loads of nutrients and organic matter in streams. The hydrological regime and hydromorphology have been impaired directly through channel modifications to secure drainage of fields and prevent flooding. Some of the impacts date back to human activities at a time when food scarcity was a significant problem for rural populations. When industrialised farming was introduced, the view was deeply imbedded in society from farmers to policy makers that the only service that the Skjern River should provide was to transport water to the sea as efficiently as possible. A number of scientists predicted the negative consequences even before the channelisation work was initiated, estimating the economic gain of the reclaimed land to be small compared to the loss of ecological integrity and services. The lower Skjern differs from other lowlands rivers of its size in the respect that it has been restored by the largest project of its kind to date in Europe. It will probably never be fully known what irreversible losses in biodiversity were caused by the short period of intensive agricultural use.

Chapter | 14 Rivers of the Central European Highlands and Plains

14.7. SPREE The Spree River is in the east Elbe catchment and borders the Oder catchment. With a length of 380 km, the Spree is a small river, but rather well known as the governmental center in Berlin lies on its banks. It shows typical hydrological and ecological features of a lowland river of the central plains, which though has undergone severe transformations by its use for production of lignite and drinking water, the removal of wastewater, as well as for navigation and recreation. The multiple uses of the Spree contrast with low water availability in the catchment, from both natural and anthropogenic reasons. Therefore, and stimulated by major concerns about the integrity of the river ecosystem, the hydrology and ecology of the Spree have been intensively studied for decades. The Spree constitutes today one of the best known and most intensively managed rivers of the world (K€ ohler et al. 2002a).

14.7.1. Physiography, Climate, and Land Use 14.7.1.1 Physiography The Spree’s source is in the Lusatian highlands near the boundary triangle of Germany, the Czech Republic and Poland at 480 m asl on the slope of Mount Kottmar (583 m asl) only 6 km from the Czech border. Mount Kottmar, which lies east of the small city of Ebersbach, seems to have been a holy place in early medieval times. The river’s name was first mentioned in the year 965, and probably is related to the indogermanic linguistic root ‘spread’. The Lusatian highlands are made up of granite partially overlain by tertiary and quaternary deposits (Driescher 2002). Within its catchment of 10,105 km2, the general flow direction of the Spree is northwest. As the mouth of the Spree at BerlinSpandau is at 30 m asl, the average slope along its 380-km long channel is around 1‰. The Spree loses 300 m in altitude along its upper segment that ends at the city of Bautzen. The historic skyline of this city is mirrored in the Spree that passes the city walls in a steep valley before entering the Bautzen reservoir. Once the river enters the lowlands, the slope decreases from 5‰ in the highlands to 0.09‰. Concomitantly, the aspect gradually changes from a rushing upland stream to a slow-flowing lowland river downstream of the city of Cottbus. In the highlands, the catchment comprises a dense, multiple-branched network of streams. In contrast, in the lowlands, which mostly consist of sandy glacial deposits, precipitation easily infiltrates so that the density of stream channels is much lower. After leaving the highlands, the middle Spree first crosses the Wrocław-Magdeburg glacial valley produced by the meltwaters of the Saale glaciation period. There, the Spree joins with its second largest tributary, the Schwarzer Sch€ ops, that drains an area adjacent the Neisse River. In the Lusatian lignite mining region near Boxberg, the stream network has been largely altered or even lost, first through

557

lowering groundwater levels on an area of 250 km2 and second by physically removing these landscape elements by huge excavators used to remove the sandy deposits that cover the lignite layers. Mining pits square kilometres in size and depths up to 120 m have been created to access the 10– 16 m thick layers of lignite. The Spree flows by the small city of Spremberg and then breaches through a major moraine produced by the Weichsel glacial period, regionally called ‘Lausitzer Grenzwall’. There, the Spree has been dammed to create Spremberg reservoir. After passing the ‘Lausitzer Grenzwall’, the Spree enters the Glogow-Baruth glacial valley, thereby by changing to northwest flow direction. In this section, the river slope reaches a minimum, as the difference in river altitude between the city of Cottbus und Lake Neuendorfer See (70 km channel length) is only 15 m. Due to the low slope, the river forms a unique network of anastomosing channels with a total length of 1300 km within an extensive wetland area, the Spreewald. Any agricultural and other transports performed on this channel network used traditional wooden barges until the early 20th century. The Spreewald is also fed by the third largest tributary to the Spree, the Malxe River. In its lower segment, the Spree changes its direction several times, as it again follows glacial valleys or is guided by the arrangement of sandurs and glacial ground moraines. The river crosses several lakes such as Lake Neuendorfer See, the northern tip of Lake Schwielochsee, Lake D€ameritzsee and Lake M€uggelsee. Additionally, the river closely flows by a number of smaller lakes that are connected to the river. Just downstream of Spreewald, the Spree originally split into two branches for 10 km, the main Spree and the Pretschener Spree. The latter historically may have had more flow than today’s main Spree channel. Downstream of Lake Neuendorfer See is the Krumme Spree (‘bended Spree’), which had extensive meanders before it became straightened and channelized from 1906 to 1912. After the river passes the northern tip of Lake Schwielochsee, it follows glacial meltwater channels northward and reaches the Berlin glacial valley east of the city of F€urstenwalde. In the section between F€urstenwalde and Berlin, called ‘M€uggelspree’ (Photo 14.8) several large paleo-meanders can be seen, which were used by a precursor river of the Spree that received glacial meltwaters, and nearly being the size of today’s Elbe River as deduced from meander radii. In the area of Lake D€ameritzsee, the Spree originally split again, this time forming three branches that discharged not only into Lake M€uggelsee (the only route today), but southwest into Lake Seddinsee and Lake Wernsdorfer See (Driescher 2002). The Spree then merges with the largest tributary of the Spree, the Dahme River (catchment size 2186 km2) that enters the Spree in Berlin–K€openick. The city of Berlin, and its former twin city of C€olln on Fischerinsel Island, were founded at a place where the Spree split into two channels, which facilitated the use of a ford, and

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PART | I Rivers of Europe

PHOTO 14.8 The Spree upstream of Berlin in summer of the dry year 2003, when discharge in this reach (called M€uggelspree) fell below a level of 5 m3/ s for 2 months. Due to extensive gowth of aquatic macrophytes that create hydraulic roughness, the water level in the river remains constant even if flow velocity decreases to 10 cm/s (Photo: M. Pusch).

later the construction of a bridge. Even today, Berlin still boasts more bridges than Venice. After crossing Berlin from east to west, the Spree joins the Havel River near the citadel of Berlin-Spandau, which flows to a large extent within riverine lakes. Despite the fact that the length of the Havel and its discharge are <50% of that of the Spree (mean discharge 15 m3/s versus 38 m3/s at the confluence at Berlin-Spandau), the resulting river is called Havel. The Havel then flows through the city of Potsdam, heads west and northwest to its confluence with the Elbe River near the city of Havelberg.

14.7.1.2 Climate Climate in the catchment is mostly sub-continental with relatively low annual precipitation and hot and dry summers. Mean annual temperature at Cottbus, which is on the middle Spree, was 8.9 C (time period 1961–1990), with only 564 mm of mean annual precipitation and maximum precipitation in summer. Within the catchment, precipitation decreases from 600 to 1000 mm in the headwaters to 500 mm near the northeast margin of the catchment, including the lower Spreewald, which is one of the driest regions within Germany. Climatic water balance in this region is negative from April to September (Kaden et al. 2002). Due to limited water availability and multiple uses of its water, the Spree is seen as especially susceptible to climate change. This assumption became evident during a recent sequence of dry years (2000, 2003, 2006) that significantly affected the hydrology, ecology and public uses of the river.

14.7.1.3 Land Use In the early medieval age, the Spree catchment was mainly inhabited by Slavic tribes that mainly built their villages and fortifications near rivers and lakes, for example at the confluence of the Dahme and Spree Rivers in Berlin–K€openick. Slavic identity, culture and language are still maintained by the minority of the Sorbs settling along the Spree in upper and lower Lusatia. Most of the pristine forest in the catchment was cleared with the German immigration wave during the 12th and 13th centuries, so that in the 14th century the catchment became even less forested than today (Driescher 2002). Deforestation probably caused substantial increases in erosion in the catchment, sediment and nutrient exports from the catchment, as well as in river discharge. In contrast to many other rivers in central Europe, the floodplain along the lower Spree was not covered by a clay layer due to anthropogenically enhanced erosion, as the transported sediments were retained in the Spreewald wetland as well as in riverine lakes. Today, the Spree catchment upstream of Berlin has a population density of 100 inhabitants/km2, and thus represents a relatively sparsely populated region within Germany. The population density decreases from 150 to 200 in the upper catchment to 55 inh./km2 in the lower catchment near Berlin (Driescher & Behrendt 2002). The Spree catchment upstream of Berlin has a relatively high percentage of forest at 41.5%, 43.4% crop fields, 4.6% settlements and 2.2% surface waters. In the upper river, over one third of the agricultural areas are drained. Most of the Spree has been profoundly influenced by lignite mining activities in the Lusatia region. The production

Chapter | 14 Rivers of the Central European Highlands and Plains

of lignite was forced during World War II, and afterwards was further developed to consist the main energy resource of the former German Democratic Republic. The mining industry was accompanied by power plants and other industries. Largescale mining involved the digging of pits at depths up to 120 m, which was possible only after the lowering of the groundwater. This resulted in the creation of a large-scale groundwater lowering funnel with an extent of 2100 km2 and the removal of 9 km3 of static groundwater (Pusch & Hoffmann 2000; Kaden et al. 2002). For the production of 1 ton of lignite, 8 tons of water had to be pumped out of the mining region. This resulted in an artifically increased discharge in the Spree for several decades until the political change 1990. Then the demand for lignite and electricity produced from it dramatically decreased with the shrinkage of east German industry. Abandoned mining pits refilled with groundwater with a pH of 2.5 produced by sulphuric acid originating from mine remnants. Hence, the pits are refilled as much as possible with water from the Spree to increase the chemical buffering capacity in the new lakes. Water is abstracted at a large scale from the middle segment and redirected into the pits, that is the emerging Lusatian Lakeland. Hence, the discharge of the Spree has been transformed from an artificially enhanced discharge until 1990 to an artificially lowered discharge regime since the mid-1990s.

14.7.2. Geomorphology, Hydrology, and Biogeochemistry 14.7.2.1 Geomorphology In its upper segment, the Spree flows through relatively steep upland valleys where it is impounded by numerous mill weirs still partially used for hydropower generation. Only short reaches are preserved that give an impression of the original features of an upland stream. After entering the lowlands, extended sections of the Spree have been trained or even shifted to adapt the river course to the needs of lignite mining. Historic maps show that branched river channels had developed in the section of Cottbus. The Spreewald wetland originally consisted of a huge forest of black alder in lowland forest peat up to 2.5 m thick. The bog area encompassed by the numerous river channels was frequently flooded and impeded agricultural use. This situation was profoundly changed by the creation of reservoirs and canals in the 20th century that prevented flooding. In the lower river reaching from the Spreewald to Berlin, the river course originally formed large meanders. Aerial photographs of the M€ uggelspree floodplain revealed that the radii of abandoned meanders that are still visible varied between 50 and 250 m, indicating varying discharge conditions that might be linked with changes in climate or land use, for example with the clearcutting of forests in the medieval age. From meanders that were cut off in historical times, and from some historic records, it can be deduced that

559

FIGURE 14.13 Course of the Spree River 10 km upstream of Berlin based on maps from 1779 (blue) and today (black lines), floodplain margins shown as dashed line (Historic map ‘Brouillon Plan ’, Staatsbibliothek Berlin).

the natural river channel was much shallower than today. The lowest areas of the channel bottom incised by 2.0 m into the floodplain. Fallen trees and macrophyte stands probably created a diverse flow pattern within the channel and created high hydraulic roughness (Hilt et al. 2008). Therefore, sediment transport probably was low. The lower Spree does not receive a sediment load from its upper catchment because of the disruptions by the Spreewald and riverine lakes. Floods carrying driftwood, or drifting ice in winter, probably favoured bank erosion and provided sources of sediment in the lower river. It is still a matter of speculation what proportion of the river bottom was covered originally by gravel entrained by bank erosion, and which would have provided valuable habitat for invertebrates and fish. To shorten the duration of annual flooding of floodplain meadows, meanders of the Spree have been cut since the late 18th century (Figure 14.13). In the 20th century, in the river downstream of Spreewald >40 meanders of the Spree were cut to increase the river’s flow capacity, which shortened the river by 20 km. The shortening of the channel resulted in significant incision of the riverbed, and a subsequent lowering of the floodplain aquifer by 1.0–1.5 m on the ‘Krumme Spree’ section. Channelization enabled more reliable use of floodplain areas for meadows, but the lowering of the groundwater table caused by the channelization made agricultural use of areas neighbouring the floodplain impossible (Andreae 1956). Today, a large portion of the riverbed is covered by shifting sands, which are only sparsely populated by benthic invertebrates. In summer, the river is dominated by masses of submergent aquatic macrophytes, which thrive because of high nutrient concentrations, the lack of floods that would potentially uproot them, and the lack of riparian trees in many places.

14.7.2.2 Hydrology Based on the average amount of precipitation in the Spree catchment (678 mm, years 1951–1996), it is estimated that 87% of that amount may be lost through potential evapotranspiration. Hence, the relatively high proportion of

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PART | I Rivers of Europe

TABLE 14.3 Shift in the mean discharge of the River Spree at several gauging stations during the 1990s. The shift was caused by a large reduction in groundwater production in the lignite mining region and concomitant start of water abstraction to fill abandoned mining pits. Gauging station

Bautzen Cottbus Beeskow Berlin-Sophienwerder

Location

Upstream of mining region Downstream of mining region Lower catchment Near river mouth

Discharge (m3/s) 1971–1997

1997–2007

2.6 18.7 25.8 36.4a

2.5 9.4 13.2 25.1

surface waters in the catchment does not reflect high water availability, but rather the long residence time of the surface waters. Due to the flat orography and unconsolidated bedrock in most of the catchment, the flow regime of the Spree is highly mitigated in comparison to other rivers of similar size in Central Europe (Kaden et al. 2002). Any quantitative hydrological analyses of the Spree are hampered by the fact that there are several sites of water abstraction, redirection and input in the catchment, which have changed over time and thus give inconsistent gauging records. The large-scale pumping of groundwaters from the Lusatian mining region has increased mean discharge at Cottbus by 6 m3/s. With the sharp decrease in lignite production in the early 1990s, hydrological conditions in the lower Spree have profoundly changed because former inputs of groundwater to the river were replaced by water abstractions. While mean discharge of the upper Spree at Bautzen (Saxony) did not significantly change, the mean discharge at Cottbus (Brandenburg), which is directly downstream of the mining region, was reduced by half from 18.7 m3/s (1971–1997) to 9.4 m3/s (1997–2007) (Table 14.3). Due to low runoff in the lower catchment, the gauging station at Beeskow 100 km downstream showed a similar reduction in discharge. Even at its mouth to the Havel River in Berlin-Spandau, the mean discharge of the Spree decreased by 31% (Table 14.3). The entire lower section, that is 250 km of river, has been affected by this shift from an artificially elevated discharge regime to an artificially lowered discharge regime. In some aspects, this large-scale flow reduction can be taken as a model case study on the effects of flow reduction expected for other rivers due to climate change. The ecological integrity of the river is especially affected by the concomitant decrease in minimum flows (Pusch & Hoffmann 2000; Pusch & K€ ohler 2002). During hot summers, the evapotranspiration rate of the Spreewald biosphere reserve causes a reduction in river discharge by up to 7 m3/s in this area. This reduction results in flows approaching zero for several weeks in the downstream river reach called ‘Krumme Spree’ (Figure 14.14). Further downstream, evaporation of water in Lake M€ uggelsee and indirect abstraction of drinking water from river via bank filtration results in a similar situation in Berlin. As urban reaches of the Spree receive treated waste-

Specific runoff (L km2 s1) 1997–2007

9.5 4.1 2.4 2.7

water, even a reversal of flow direction may occur locally. The hydrological situation has been especially tense in the recent series of dry and hot years (2000, 2003, 2006).

14.7.2.3 Nutrients and Pollution The Spree was historically polluted by urban sewage, by wastewater produced by the many small factories (cloth industry) in the upper catchment, and by the effluents from the mining industry along the middle river. For some time groundwater pumped from the lignite mining area was discharged directly into the river, which was heavily polluted by flocculating iron oxides that covered the riverbed with an inorganic mud layer. Additionally, the river was loaded by nutrients released from fish ponds and agriculture. Today, the discharge of poorly treated wastewater has been largely reduced, but locally still causes critical loadings in impounded headwaters. Following the political change in 1990, total inputs of total phosphorous and total nitrogen into the Spree were 68% and 46% lower, respectively, than in the 1980s (Behrendt 2002). Based on the river catchment model MONERIS, it is estimated that non-point pathways of nutrient input are still prevailing for phosphorous and nitrogen. Within the river, these nutrients are subject to sedimentation and intensive biological metabolism. Thus, around 50% of the phosphorous and nitrogen inputs are retained, with the

FIGURE 14.14 Long-term decrease of the Spree River discharge in summer due to gradual abandonment of lignite mining activities in the catchment, with recent minima in 2000, 2003 and 2006 additionally caused by extraordinary dry and hot years.

Chapter | 14 Rivers of the Central European Highlands and Plains

actual retention efficiency dependent on hydraulic properties, loads, and biological metabolic activities (G€ucker & Pusch 2006). The present concentration of total phosphorous, averaging 100 mg/L is still two- to threefold higher than estimated background concentrations (Gelbrecht et al. 2002), and allows intensive growth of aquatic plants. During the period of artificially elevated discharge and highest nutrient loading, the Spree was a plankton-dominated river (B€ ohme 1994), but shifted around 1995 to a macrophyte-dominated river. The production of large amounts of autochthonous biomass due to eutrophication is regarded as a ‘secondary pollution’ of the river. This biomass fuels intensive metabolism of organic matter, which mainly takes place in the uppermost sediments (Fischer 2002; Fischer et al. 2002a, 2002b). Suspended particles are retained, depending on discharge, at a rate of 9–33% per river kilometer (Wanner & Pusch 2001, 2002), and may be even higher in reaches with dense macrophyte stands. In the Krumme Spree section, a population of 5 million unionid mussels together with 120 million zebra mussels caused a significant improvement in water quality by removal of suspended algae and other particles from the water column (Pusch et al. 2001). However, the mussel populations have decreased by 93% since then, probably due to the reduction in flow. With reduced flows, phytoplankton can grow better in riverine lakes and be retained more efficiently within the river channels downstream of the lakes. Enhanced retention of organic matter is followed by increased microbial degradation, which may produce severe deficiencies in dissolved oxygen (DO). Reduced flow velocity and DO availability can lead to the loss of sensitive lotic invertebrate and fish species. Hence, flow reduction due to water abstraction and climate change aggravates existing problems of water quality that arise from the secondary pollution produced by eutrophication (Pusch & K€ ohler 2002).

14.7.3. Aquatic and Riparian Biodiversity 14.7.3.1 Terrestrial Fauna Although being subject to multiple pressures, the Spree and its floodplain still harbour many rare birds that depend on aquatic and semi-aquatic habitats such as kingfisher (Alcedo atthis), crane (Grus grus), bittern (Botaurus stellaris), black tern (Chlidonias niger), white stork, black stork (Ciconia nigra), osprey, marsh harrier (Circus aeruginosus) and corn crake (Beutler 2002). Besides breeding species, the Spree valley and its floodplains flooded in spring offer resting areas for migratory birds such as bean goose (Anser fabalis), white-fronted goose (Anser fabalis), whooper swan (Cygnus cygnus), goldeneye (Bucephala clangula) and goosander. The lower Spree, tributaries, and associated lakes harbour a stable population of otter (Lutra lutra). For otters, the river has special importance during cold winters when lakes entirely freeze and some spots remain open on the river. In the

561

1970s, American mink (Mustela vison) that escaped from fur farms colonized the Spree. The presence of this invasive species makes the potential reintroduction of the European mink (Mustela vison) difficult. Another invasive species, the bisam rat (Ondatra zibethicus), lives on the Spree, partially feeding on aquatic macrophytes and unionid mussels (Beutler 2002). In the lower Spree, 12 species of amphibians and six species of reptiles have been recorded (Beutler 2002). Among them, a relict population of European pond turtle (Emys orbicularis) and scattered populations of firebellied toad are most noteworthy. The European pond turtle need sunny water bodies with dead wood present near the shores to allow them to warm themselves. A sunny sandy hillslope should be nearby where they can lay eggs. Adult turtles are long-lived, but are regrettably often killed in fish traps. The firebellied toad is a continental species that needs sunny floodplain areas that are flooded during May and June for the development of tadpoles. Due to the drainage of most floodplains, the firebellied (Bombina bombina) toad now rarely occurs in its original habitats, but does in man-made ponds and other types of waterbodies.

14.7.3.2 Aquatic Fauna Originally, the upper Spree were classified as a trout and grayling zone, the middle and part of the lower river as barbel zone, and some of the lowermost sections as bream zone. Even after the recent improvement in water quality, the construction of numerous impoundments and other alterations in hydromorphology limits the restoration of the natural zonation of fish species today (Wolter et al. 2002). In addition, the numerous weirs prevent the longitudinal migration not only of former migratory species but also potamodromous species (Baade & Fredrich 2005). Today, the most abundant fishes in the Spree are roach, perch, silver bream, bleak, common bream, gudgeon, rudd, pike, European eel and ruffe. Six species of the river’s original fishes are missing. Rheophilic fishes have declined substantially with the receding discharge, and recently represent only 4–21% of the fish assemblages in the middle and lower Spree (Wolter et al. 2002). In the river and adjacent waterbodies, 440 species of benthic macroinvertebrates have been identified (including chironomids; Pusch et al. 2002). Due to sparse historic records, losses in this inventory can be estimated only for some groups. The invertebrate fauna clearly differs between the highland segment, the Spreewald section, the lower river, and the urban section in Berlin. Rheophilic species make up 70% of the fauna in the upper river, 50% in the middle segment, and 20% in the lower river. Invertebrate assemblages are still affected by pollution in some headwaters. In most of the river sections, flow velocity, availability of stable bottom substrates and secondary pollution by eutrophication are the most important habitat factors

562

(Brunke et al. 2001, 2002). In sections most severely affected by the reduction in flow, lotic fauna may be almost totally replaced by lentic fauna that tolerate reduced dissolved oxygen content. In the Spree, the large populations of unionid mussels and zebra mussels can significantly improve water quality in the river by the removal of suspended particles, including planktonic algae, from the water column (Pusch et al. 2001). Filtration activity of some unionid mussels (especially Unio tumidus, U. pictorum and A. anatina) may be significantly hampered by the colonization of their shells by zebra mussels. However, zebra mussels and unionids seem to coexist in the Spree. Infestation of unionid shells by zebra mussel seems to be limited by the fact that unionids spend a major part of the year fully buried in sediments, which is not tolerated by zebra mussels (Schwalb & Pusch 2007). Despite the human alterations of the river, a number of rare invertebrate species have survived, especially in the Spreewald biosphere reserve, such as the thick-shelled river mussel, the European fingernail clam, the Asian dragonfly, and the green club-tailed dragonfly.

14.7.3.3 Aquatic Vegetation The river, riverine lakes, and oxbow lakes are inhabited by 55 species of submerged or floating aquatic macrophytes (K€ orner & Pusch 2002). The middle and lower river have been dominated by macrophytes since the mid-1990s. Here, aquatic vegetation is dominated by arrowhead (Saggitaria sagittifolia), strapweed (Sparganium emersum), yellow water-lily, common water-crowfoot (Ranunculus aquatilis) and sago pondweed (Potamogeton pectinatus). Water chestnut (Trapa natans) and water soldier (Stratiotes aloides) are of special cultural and ecological interest (K€ orner 2002). Water chestnut reaches its northern limit in distribution here. Historically, water chestnut occurred in large populations on the river and its floating rosettes even hampered navigation on the river. The nuts produced by this plant were harvested by monks, and more recently also fed to pigs. Today, the riverine Lake Neuendorfer See again holds a significant population of water chestnut. The sword-like leaves of the water chestnut are half-submerged, half-emerged during summer, and its stands may be used for nesting by black tern. This plant also hosts the aquatic caterpillars of the butterfly Paraponynx stratiotarum and serves the southern hawker (Aeshna viridis) as exclusive substrate to lay its eggs (K€ orner 2002). Phytoplankton development in the Spree is favoured by the fact that the river, including riverine lakes, exhibits a travel time of up to several weeks, which enables phytoplankton with a doubling time of one to several days to reach significant populations (K€ ohler 1994; K€ ohler et al. 2002b). The river is constantly inoculated by phytoplankton flushed from Spremberg reservoir, as well as by phytoplankton from riverine lakes. During periods of low flow, phytoplankton

PART | I Rivers of Europe

development may be reduced due to deposition of diatoms and grazing by zooplankton. During summer, filtration activity of mussels, shading by aquatic macrophytes, and retention by epiphytic biofilms lead to significant decreases in phytoplankton downstream of riverine lakes (Welker & Walz 1998).

14.7.4. Management and Conservation 14.7.4.1 Economic Importance Since the 13th century, hydropower of the Spree and its tributaries was used by numerous water mills. In later centuries, the Spree gained major importance as a navigational waterway. With improved construction, the river channel was deepened and canals built to connect it to other navigational waterways. The annual flood period of floodplain meadows also was shortened during winter or spring. Due to low precipitation, there is substantially less water available for each inhabitant than for other Central European rivers (Figure 14.15). Each cubic meter of river water of the Spree is subject to multiple uses, all managed by the regional environmental agencies of Berlin and Brandenburg. Three major reservoirs have been built in the catchment, which serve to mitigate water shortages during summer, to control flooding (especially in Spreewald), to provide cooling water for lignite powerplants, and for recreation. The Bautzen reservoir holds 49 million m3 of water. On the tributary Schwarzer Sch€ops, the Quitzdorf reservoir retains 25 million m3 of water. The dam of the Spremberg reservoir is at the site where the Spree cuts into the glacial moraine called ‘Lausitzer Grenzwall’. The dam is 20 m high and retains a 7-km long lake holding 42 million m3 of water (Driescher 2002). In numerous places within the catchment, tributaries have been impounded to create fishponds, for example in upper Lusatia or near Peitz/Cottbus where a pond of 7.2 km2 is found (Driescher & Behrendt 2002). These fishponds need a certain net supply of water that is evaporated and also release water enriched with nutrients. In the river crossing the Lusatian mining area, water is abstracted to refill mining pits, and a constant minimum

FIGURE 14.15 Potential water resources available for citizens living in various river catchments in Germany, expressed as mean river discharge per capita.

Chapter | 14 Rivers of the Central European Highlands and Plains

discharge of 8 m3/s is left for the river at Cottbus, except during major floods that cannot be fully redirected into mining pits. In the Spreewald biosphere reserve, boating on the river is a major tourist attraction and supports a major business. The luxuriant wetland forest within the Spreewald biosphere reserve has an evapotranspiration potential of 5– 8 m3/s, so that on hot summer days – together with water abstractions for agriculture – the minimum discharge of 8 m3/s at Cottbus is reduced to 1 m3/s or less downstream of Spreewald. Near the city of F€ urstenwalde, a 19-km reach of the Spree is used as a part of the Oder-Spree navigational canal, where a significant part of the river discharge is abstracted even during drought periods to allow shipping on the canal. The M€ uggelspree, which is the section of the Spree directly upstream of Berlin, and lakes downstream are favourite sites for anglers and boating, including motorboats, sailing boats and kayaks. Within the city of Berlin, the river is again used as a navigational waterway for cargo and tourist ships, which significantly affect littoral biota by the hydrodynamic effects of ship-induced waves (Gabel et al. 2008). The inland harbour of Berlin (Berlin–Westhafen) can be reached through canals from the Oder as well from the Elbe, Weser and Rhine systems, and thus links Berlin with ocean harbours, for example at Hamburg. Berlin gets two thirds of its drinking water supply from the Spree and Havel, which is produced from wells built along the shores, for example Lake M€ uggelsee via bank filtration. To assure the quality of drinking water, the removal of wastewater, and the use as cooling water, a minimum discharge of 8 m3/ s in the Spree at its inflow to Berlin is necessary (RehfeldKlein 2002). In recent years, this value has not been reached for several weeks or even months due to the flow reduction in the river. The urban reach of the Spree is used as cooling water for electric power generation, and it still receives some tertiary-treated wastewater with relatively low residual concentrations (G€ ucker et al. 2006) and stormwater runoff from the streets (Rehfeld-Klein 2002). Due to the design of the canals of Berlin, most treated wastewater enters the Havel River downstream of Berlin. It is envisioned to reopen the upstream part of the urban Spree for bathing after further progress in the retention of stormwater runoff.

14.7.4.2 Flood Control Even though infiltration capacity of the sandy soils dominating the lowlands is high, the Spree can produce significant winter or spring floods from snowmelt or heavy rains. Large summer floods may also occur. Such flood risks in the catchment have been managed in multiple ways, such as by deepening river channels, building levees, construction of the Bautzen, Quitzdorf and Spremberg reservoirs, use of some lakes in the newly created Lusatian lake district for water retention, and by the construction of several canals that can

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serve as additional discharge routes (flood canals in the Spreewald, Dahme flood canal connecting the Spree to the Dahme River, and Oder-Spree canal).

14.7.4.3 Conservation and Restoration The hydrological and ecological characteristics of the Spree are different than any other river in the region, a fact giving high priority to its conservation. Valuable habitats within the Spree floodplain and adjacent wetland areas, including areas linking these habitats, have been assigned legal conservation status. From the Spree highland valley upstream of the city of Bautzen down to Berlin, 40 nature reserves and Natura 2000 areas occur and are legally protected (Zimmermann et al. 2002). These protection zones mainly cover the river channel, adjacent oxbow lakes and ponds, lowland bogs, remnants of softwood and hardwood floodplain forests, reed areas, wet meadows with diverse vegetation, and dryland vegetation in dune areas. The preservation of aquatic and terrestrial biological diversity in these areas will largely depend on the future management of the river, especially flood dynamics, and minimum flow rates and water levels during drought periods. Hydrological dynamics not only provide aquatic habitat diversity, but also shape floodplain vegetation. For many reserves, stabilization of groundwater levels by closure of drainage ditches would be necessary to stop degradation of bogs, or to even re-initiate peat growth. In the Spreewald UNESCO biosphere reserve, as on many other reserves along the Spree, a special challenge is the protection of valuable habitats that were created by former agricultural practices, such as wet meadows that are extensively grazed or mowed only once a year. Recent reductions in river discharge influenced the structure and function of the river ecosystem for a distance of 230 km in various ways (Pusch & K€ohler 2002). Reduced flow velocity and DO availability has lead to the loss of sensitive lotic invertebrate and fish species from that reach. In free-flowing river reaches, lower discharge is paralleled by lower water levels, which are followed by lower groundwater levels in the floodplain up to a distance of several hundred meters. Water levels in the river also affect floodplain habitats. Management and restoration strategies must be developed to mitigate the ecological effects of flow reduction (Gr€unert et al. 2002; Pusch & K€ohler 2002). The restoration approach is based on (i) an ecologically defined minimum flow level, supplemented by (ii) ‘ecological’ floods in the river to provide minimum discharge dynamics, and (iii) the restoration of a shallower river bed. The restoration of a shallower riverbed would counteract most of the problems produced by flow reduction that have been mentioned above. With a shallower riverbed, flow velocity would be higher even at low flows, and physical reaeration would be more efficient.

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In contrast, an alternative strategy that foresees the construction of more impoundments, as discussed for the Spreewald biosphere reserve, would only stabilize groundwater levels in the floodplain, but worsen problems concerning water and habitat quality.

14.7.5. Perspective For many people in Berlin seeking recreation, for example by swimming or boating in the lower Spree, the river represents a piece of ‘pure nature’. This impression has arisen by the green river margins with lush vegetation and clear water. Only with good knowledge of the system is it recognized that the lush stands of common reed and cat-tail root within rip–rap stones protecting the shores from erosion were rarely present before 1995 and do not represent a typical shoreline vegetation of a dynamic river. Similarly, mass development of submerged macrophytes clearly indicates eutrophication and lack of shading by riparian trees. The large plant biomass may produce critical depletion of dissolved oxygen (DO) during the night. Anglers will notice that typical riverine fishes are lacking. A synopsis of the ecological situation of the river reveals the unexpected situation that even after significant efforts and success to improve its water quality after 1990 the ecological integrity of Spree system today is again at the brink. Due to flow reduction, there is a real risk that the river will lose basic riverine features such as a mixed water column providing DO to benthic assemblages, a typical riverine invertebrate fauna contributing to the ‘self-purification’ of the river, and a self-reproducing lotic fish fauna. It seems that the decrease in river discharge – in combination with significantly altered channel morphology – may produce as severe ecological effects as pollution did earlier. Hence, the Spree gives an impressive example of how the unsustainable exploitation of a resource – which in this case was the static groundwater resources in the Lausitz region – may hide existing socio-ecological problems but inevitably produces an unwelcome legacy for future generations. These then must find ways to reinstate a self-regulating system that includes key features of hydrology, geochemistry and ecology.

14.8. DRAWA The Drawa River in northwest Poland is one of the few lowland rivers in the ecoregion that still exhibits many natural features along major portions of the river. These include fluvial dynamics of the river channel, connectivity to many natural lakes, extensive surrounding forests that are not managed on the riverbanks, and a diverse aquatic fauna. As the river flows through scenic lake areas and steep moraine valleys, it is considered to be one of the most beautiful rivers in Poland. These features are protected and further developed by the Drawa National Park, which has the otter as its

PART | I Rivers of Europe

symbol. As there are no dams present between the lower Drawa and the Baltic Sea, the Drawa forms an important potential site for the reintroduction of endangered migratory fish such as salmon and sturgeon.

14.8.1. Physiography, Climate, and Land Use The Drawa flows roughly southward through northwest Poland, draining a catchment area of 3289 km2 (Kondracki 1994). It discharges into the Notec River near the small city of Krzy_z Wielkopolski, which runs west and enters the Warta River near Gorzow Wielkopolski, a large tributary to the Oder River. Along its course of 199 km, the Drawa flows through the Polish provinces (voivodhips) of West Pomerania, Wielkopolska and Lubuskie. The Drawa basin comprises 472 lakes with a total area of 156 km2 (Pasławski 1981), many of them in glacial troughs. Of these lakes, 178 exceed a surface area of 10 ha each, 25 lakes 100 ha each (Janczak 1996), and 390 are interconnected by streams and rivers. The Drawa originates in Krzywe Lake (53 420 3300 N, 16 0 8 4600 E) at 160 m asl in the Drawa lake district, a scenic landscape comprising 47 lakes >1 ha. Downstream of the source, the river is mostly bordered by agricultural areas, while the bottom of the small river valley is little used. The upper river until the small city of Drawno changes the direction of flow several times and thereby joins 18 lakes (Kaczanowska et al. 2004, Rz˛e tała and Jagus 2007), the largest ones being Lake Drawsko (surface area 18 km2, max. depth 80 m, second deepest lake in Poland) and Lake Lubie (14 km2, 46 m) (Pasławski 1996). Additional numerous lakes are connected through tributaries. The lower river meanders through a deeply incised valley lacking fluvial lakes. This section is within the Drawa National Park and its adjacent buffer zone dominated by the Drawa forest (800 km2), while the valley bottom is often used as meadows. Here the river receives its major tributaries Korytnica and Płociczna (left side) and Mierz˛e cka Struga (right side) (Janczak 1996). The Drawa catchment was formed by glacial and periglacial processes in the Weichsel Glacial period. The highest altitude (223 m asl) is reached at its northernmost edge by the moraines of the Pomeranian stage. There, the Drawa rises in a small glacial valley, the so-called Valley of Five Lakes (near the road Połczyn-Zdroj-Czaplinek), and subsequently flows through various clear lakes. The Drawa then drains the western part of a vast outwash plain (sandur) that developed south of the moraine belt. This plain that gently slopes to the south is locally interrupted by loamy moraine deposits formed as post-lake hummocks (Rz˛e tała and Jagus 2007). Isolated ice masses produced numerous thaw hollows as well, which are now often filled by kettle lakes or peat bogs. Near postglacial channels, sediments filling cracks in the dead ice formed kames ridges (Wnuk-Gławdel et al. 2006). Hence, the catchment now exhibits a diverse orography,

Chapter | 14 Rivers of the Central European Highlands and Plains

which is partially reflected in the diversity of lake types. Shallow lakes situated in the ground moraine and oval kettle lakes contrast with the deep ribbon lakes Drawsko, Lubie and Siecino that exhibit complex morphometry, long shore lines and many peninsulas and islands, for example Lake Drawsko with 74 km of shoreline and 14 islands. Forced by some smaller morain belts, the Drawa first flows west, but then follows the general slope of the sandur to the south. Together with several other rivers neighbouring to the east, the Drawa is an exception in the central and east European lowlands where most river systems flow directly to the North and Baltic Seas. As the middle part of the Drawa’s valley is accompanied to the west by a section of the Pomeranian stage moraines, the valley was probably pre-formed by postglacial meltwater. The valleys of the Drawa and Płociczna Rivers are incised in their lower courses by up to 30 m into the surrounding sandur. The glacial gullies formed parallel to them by glacial scour or outwash beneath the ice sheet are now partially filled with lakes, including the gullies of the Lakes Płociowe, Marta, Jamno and others. The lowermost section of the Drawa valley breaches through a local moraine belt bordering the Toru n-Eberswalde postglacial stream valley, where the Drawa then discharges into the Notec River (Kondracki 1994) The Drawa catchment lies in a transition zone between the sub-atlantic and sub-continental climate types, having relatively low annual temperature amplitudes and moderate drought periods, but late springs with ground frosts and long warm autumns. Average annual temperature is 7.9 C. The warmest months are July and August with average temperatures of 17 C, the coolest month is January at 2 C. On average, there are 32 days with an average temperature below 0 C, and five days of 30 C or more (Wnuk-Gławdel et al. 2006). Annual precipitation is 592 mm, and there is rain on 172 days per year on average. The length of the growing season varies between 200 and 230 days from north to south (Kozmi nski et al. 2001). In 1237, the Drawa was mentioned for the first time in a deed of the Duke of Great Poland Vladislav Odonic under the name Drava. German settlers who subsequently moved in called it Drage. The linguistic sources of the name are traced back to Indo-European and early Slavonic sources meaning ‘to be in a hurry’, referring to the rushing flow of the river. From the late 14th century to 1772, the lower Drawa and its tributary Płociczna formed the borderline between the German Electorate of Brandenburg and the Kingdom of Poland, a situation that may have contributed to the preservation of the area. The Drawa also served as military defensive line, as German fortifications were built both in the 14th century and before World War II. Today the Drawa still forms the borderline between three voivodhips. The wilderness along the Drawa was first colonized to a significant extent by Cistercian monks in the 14th century, who cut parts of the forest, drained marshes and built water mills. In the 16th century, a local squire founded a dozen

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small villages to populate the area, leading to a mosaic of fields, pastures and forest. Tar distilleries (e.g. at Dragetheerofen 10-km upstream of the river mouth) and glass smelting works (from the 17th century on) were run near the river (Wnuk-Gławdel et al. 2006). From the medieval ages until 1979, the Drawa served as a waterway for timber rafting (Wnuk-Gławdel et al. 2006). In 1662, its banks were stabilized, the riverbed was deepened in shallow reaches, and tree trunks were removed. From about 1850, timber rafting mostly supplied a sawmill operating on the lower Drawa (Drageschneidem€uhl). Today, remains of rollways used as river ports for preparing timber rafting can be seen on the banks (Rz˛e tała and Jagus 2007). In the 19th century, a system of irrigation canals was built to bring water to the meadows in the valley. Today, the river is used for hydropower and tourist purposes. At the end of the 19th century, a long-term decrease in the population started and pasture land formerly used for sheep farming as well as fields on poor soils were abandoned. Today, the population density is relatively low, and farmlands are found only on patches of moraine clays (e.g. in the region of Drawno). As abandoned farmland was transformed into pine plantations, and because of historical forestry strategies, pine forests now cover extensive areas (Kujawa-Pawlaczyk and Pawlaczyk 1997). In the Drawa catchment, there are numerous small point sources and diffusive inputs of nutrients threatening water quality (Wozniak 2000). Despite new sewage treatment plants and existing ones being refurbished, inputs of domestic sewage still enter the river. Additionally, a pig farm near Drawno as well as crop fields situated adjacent to the river channel are still threats to water quality. Tourism may also impair water quality by camping in uncontrolled places, excessive development of tourist facilities, for example at Lake Lubie, or through disposing bait used for angling.

14.8.2. Geomorphology, Hydrology, and Biogeochemistry Surface features are composed of Quaternary siliceous sandy deposits 140 to 180 m thick, which overlay Tertiary and older bedrock layers (Nowacki 1999). These porous sediments, which exhibit a filtration rate of 3 104– 1 104 m/s, contain a 10, 20 m thick usable uppermost water bearing horizon. This aquifer is usually well protected by covering layers some 10–50 m thick, which increase in thickness to the north and also comprise clay layers. Within the aquifer, there exist regional channel structures from north to south. Due to the high infiltration capacity of deposits and a high evapotranspiration rate, parts of the catchment lack surficial drainage systems. The average slope of the river channel is 0.61‰, ranging between 0.79‰ in the uppermost section until Lake Lubie to 0.47‰ in the lowermost section downstream of the hydropower station Kamienna. Channel slope locally peaks for

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1 km at 2.67‰ within the gorge called ‘hell’ below Lake Lubie. In the upper catchment, the river network is rather irregular and joins the subcatchments of several lakes. In total, the river flows for 38.5 km within lakes. Hence, the slope of fluvial sections is somewhat higher than lentic sections, reaching 1.07‰ in the uppermost section (Pasławski 1996). In the southern part of the cachment, the drainage system is better developed with less flow through lakes and having two large tributaries, the Płociczna (catchment area 450 km2) and the Mierz˛e cka Struga (585 km2). The Drawa flows through 18 lakes with a total area of 42 km2 and capacity of >700 106 m3. The Drawa catchment supplies an area-specific runoff of 6–8 L/km2/s (mean value for Poland is 5.5 L/km2/s). Numerous springs can be found in the upper Płociczna and Korytnica Rivers (delivery 7–29 L/s), and numerous smaller ones in the area of Drawa National Park along the Płociczna and Drawa rivers that drain the first water bearing horizon (Nowacki 1999). Infiltration of water has been observed in the area of Lake Czarne and Lake Ostrowieckie. River discharge (mean, minimum and maximum annual flows 1961–2000) increases longitudinally from 0.46 (0.05–0.5) m3/s at Stare Drawsko on Lake Drawsko to 4.2 (0.4–18.8) m3/s in Drawsko Pomorskie near Lake Lubie, to 9.3 (2.6–9.3) m3/s in Drawno, and to 21.5 m3/s (8.0–46.0) at the gauging station Drawiny near the mouth (Pasławski 1981; Nowacki 1997). The largest tributary, the Płociczna, has a discharge of 3 m3/s at its mouth.

PART | I Rivers of Europe

The annual flow regime is a rainy oceanic type, with maximum flow occurring in April and May, and minimum flow in July and August (Pasławski 1981; Nowacki 1997). The Drawa’s flow regime shows the least seasonal variation among all rivers in the Oder basin. This stable flow regime is due to the fact that the river is mainly fed by groundwater from numerous springs. Further, hydrological extremes are significantly mitigated by subsurface storage as well as by surficial storage within the numerous lakes connected to the fluvial system. Interannual variation in water levels at the gauging station Drawiny also are quite moderate. Maximum, mean and minimum water levels vary between wet and dry years by 100, 49 and 38 cm, respectively (Pasławski 1996). Water levels in the Drawa may significantly increase (up to 120 cm upstream of Drawno) by the luxuriant growth of aquatic plants during summer, so that maximal water levels can be observed even at minimum flows during summer. Despite its stable hydrology, the Drawa, and especially its tributaries Płociczna and Korytnica, exhibit significant fluvial morphodynamics that shape the valley slopes and the relief of the riverbeds. River bends frequently cut the erodible moraine slopes, producing sandy scarps or sheer walls of morainal clay (Photo 14.9). The riverbed alternates between shallow rapids and pools with depths from 1.5 to 2.5 m, and backwaters are frequently encountered. Sediments consist of stones, gravel, sand or organic mud (Wozniak 2000). Fallen trees, which are mostly not removed, play a special role in diversifying streambed

PHOTO 14.9 The Drawa seen from one of the steep erosional banks formed in the area of the National Park where the river broke through glacial moraines (Photo: M. Bylina).

Chapter | 14 Rivers of the Central European Highlands and Plains

morphology. The lowermost section between the confluence of the Prostynia to the Drawa’s mouth shows special fluviomorphological diversity, with depth varying from 0.5 m in riffles to 2.5 m in pools at a channel width of 20–30 m (Nowacki 1997). Water temperatures are mitigated by the high proportion of subsurface runoff contributing to river flow. For the same reason, ice rarely forms on the Drawa. Maximal water temperatures in the Drawa are in July (22.6 C in July 1952), and the lowest (0.2 C) in December, January, and February. The highest changes in water temperatures within one month occur in May (11.0 C), and the lowest in February (0.4 C) (Pasławski 1981; Nowacki 1997). In the second half of the 19th century, large-scale land reclamation efforts were started to drain meadows, irrigate dry areas, and build fishing ponds. Today, the remains of dry reservoirs, dikes, barrages and culverts can be seen, as well as canals several kilometers long such as the Kanał Sicinski between lakes Sitno and Głusko. The Drawa was also influenced by the channelization of the Notec River conducted in the years 1891–1896, when the river was shortened by 23.2 km. As a result, a considerable decrease in the water table and an enlargement of the Drawa catchment were observed. The drainage of wetlands first resulted in increased agricultural productivity for some years, which then fell again as a result of soil mineralisation, ground lowering by 0.4–0.8 m, and subsequent secondary swamping (Nowacki 1999). Water quality in the Drawa was significantly affected by the input of domestic sewage from the villages along the Drawa, for example from the small cities of Złocieniec and Drawsko Pomorskie, which also caused pollution of cadmium and carbolic acids that affected the water quality of Lake Lubie. Downstream of Drawno, water quality was less affected. According to monitoring surveys conducted by the Chief Inspectorate for Environmental Protection in Szczecin, water quality has remarkably improved since the 1990s in terms of concentrations of bacteria and nitrate (Nowacki 2002). At present, many reaches of the Drawa are assigned to the first water class, although lake outflow reaches are significantly loaded by algae flushed from lakes. Below the small cities of Złocieniec, Drawsko Pomorskie and Drawno, the Drawa is still moderately loaded with bacteria as well as phosphorus and nitrogen, and effluent standards are partially not met. Just downstream of Drawno, water quality is threatened by a large pig farm where liquid manure is poured on fields in the immediate vicinity of the Drawa. Water quality, which is also monitored by the Chief Inspectorate for Environmental Protection, is moderately impaired by eutrophication in lakes on the Drawa and its tributaries. The mesotrophic lakes in the area, which hold populations of the stoneworts Chara aspera, Chara fragilis, Chara jubata, Chara rudis and Chara tomentosa, are all groundwater-fed, including lakes Marta, Piaseczno, and

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Du_ze within the Drawa National Park (Nowacki 2002). Several lakes in the park are dystrophic. Lake Czarne, which is surrounded by forest, is meromictic. There are many lakes that are strongly eutrophic and develop phytoplankton blooms. The medium-sized lakes M˛a kowarskie downstream of Kalisz Pomorski and W˛a sosze near Złocieniec even have bad water quality (Nowacki 2002). Monitoring of water quality in groundwaters conducted by the Polish Geological Institute at some scattered observation wells show that the first level of groundwaters contains not only significant concentrations of iron (0.5– 3.5 mg/L) and manganese (0.1–3.6 mg/L), but also elevated concentrations of nitrates and nitrites. These waters directly supply water to rivers, lakes, swamps, and springs. Deeper groundwaters contain waters of the highest quality, as these are protected against pollution by thick clay layers, and thus are used for drinking water supply (Nowacki 2002).

14.8.3. Aquatic and Riparian Biodiversity In the extensive protected areas in the Drawa catchment, rare species still occur that depend on habitats maintained by the dynamic natural processes that are limited outside protected areas, such as slumps and landslides on river banks or dead trees falling into the river channels that shape the river channel and enhances the diversity of aquatic habitats.

14.8.3.1 Flora The Drawa valley exhibits a high diversity of plant communities. The area of the Drawa National Park has nearly 80 plant communities mentioned in the European Habitat Directive. These are, among others, rich beech and swamp alder forests, marsh meadows, parts of coniferous forests and marsh birch woods, wet and fresh meadows, fens, stonewort meadows in lakes, pond weeds of eutrophic lakes, spring vegetation, stands of great fen-sedge, and peat fens (Wnuk-Gławdel et al. 2006). The Drawa forest, which extends from Lake Lubie to the Notec River, mainly consisted of beech, while today pine dominates and beech forests may be encountered in the valley of the Drawa and west. Fragmented remains of beech and oak-beech forests are now actively managed in the area of Drawa National Park, while some other parts are completely left to natural processes. The shores of lakes and rivers are accompanied by alder forests, which often grow on former meadows, and in some cases rare riparian elm forests (Ficario-ulmetum minoris). One of the most precious natural features in the Drawa valley are peat bogs of several types, which – even if formerly used as meadows – still harbour their characteristic flora (Wozniak 2000) such as menyantes, cranberry, cottongrass species, white beak-sedge (Rhynchospora

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alba), sundew species, marsh violet, dwarf marsh violet (Viola epipsila), fen orchid (Liparis loeselii), lesser panicled sedge (Carex diandra), stands of great fen sedge (Cladium mariscus), acid bog springs with common sedge and sedges forming hummocks including fibrous tussock sedge (Carex appropinquata) and Carex caespitosa. The peat bog called ‘Sicienko’ on the southern edge of Sitno Lake is one of seven locations in Poland where the inconspicious boreal shrub leather leaf (Chamaedaphne calyculata) grows, which marks its most south-western distribution point in Europe (Wnuk-Gławdel et al. 2006). The Drawa and its tributaries are often colonized by water buttercup species, arrowhead, burreed and pondweeds. In sections of the Drawa with stony bottoms and fast current, stones are frequently overgrown by the rare red alga Hildebrandtia rivularis, which indicates good water quality (Wnuk-Gławdel et al. 2006).

14.8.3.2 Fauna Among the 40 species of mammals recorded in the park, many are related to aquatic or wet habitats. This holds especially true for the numerous beaver and otter, the European water shrew (Neomys fodiens), European polecats (Mustela putorius), and for elk (Alces alces) that sporadically walk through the park (Kujawa-Pawlaczyk 2004; Wnuk-Gławdel et al. 2006). The presence of 10 species of bats is remarkable, as well as a small population of wolves in the Drawa Lakeland that use the Drawa valley as a migration corridor to reach a neighbouring population in the Notec Forest. More than half of Polands avifauna can be observed in the Drawa valley. Some 150 species were recorded in the Drawa National Park only, with 120 of them nesting there (Kujawa-Pawlaczyk 2004). In the forests along the Płociczna, there are populations of Tengmalm’s owl (Aegolius funerus), red-breasted flycatcher (Ficedula parva) and crane, and near Ostrowieckie Lake nests of eagle owls, white-tailed eagles and ospreys can be found. Near their preferred types of waterbodies green sandpiper (Tringa ochropus), kingfisher (Alcedo atthis), dipper (Cinclus cinclus), grey wagtail (Motacilla cinerea), mallard (Anas platyrhynchos), goosander, common goldeneye (Bucephala clangula) as well as great crested crebe (Podiceps cristatus) have stable populations (Wnuk-Gławdel et al. 2006). The Nature 2000 Protection Area established in the middle and lower Drawa constitutes one of the most important refuges for eagle owls (Bubo bubo) and some other birds of prey, and is used as a wintering area by whooper swans (up to 150 individuals) and as resting habitat in autumn for migrating cranes. The herpetofauna of the Drawa National Park includes 20 species, 13 species of amphibians and seven species of reptiles, which are most of the species found in Poland. The most remarkable species found are great crested newt,

PART | I Rivers of Europe

smooth snake and the very rare European pond turtle (Wnuk-Gławdel et al. 2006). The ichthyofauna is the most precious natural element harboured by the Drawa basin. In the Drawa, its tributaries and lakes, 42 fish, 41 fish species from 11 families (incl. Cyclostoma) are found, which is among the richest fish fauna in Poland (Wnuk-Gławdel et al. 2006). In the Drawa River alone, 27 fish species were recorded, and 28 in the Płociczna. Moreover, the Drawa is one of the few rivers in the country that harbours all three biological forms of trout, such as brown trout (S. trutta m. fario in rivers and S. trutta m. lacustris in lakes) and sea trout (Salmo trutta m. trutta). Apart from extremely threatened species, such as river lamprey and brook lamprey, salmon and sea trout, there are numerous and relatively stable populations of species that are rare at the national scale, including brown trout, grayling, minnow and bullhead. Among the most interesting fish living in Ostrowieckie Lake (the largest lake of the park) are lake trout, vimba, common whitefish and vendace. The Drawa was the natural spawning ground of one of the last native populations of salmon until it became extinct in the 1980s as a consequence of habitat loss due to flushing the reservoir at Kamienna, as well as by overharvesting and possibly by a viral disease (M75). Within the nation-wide migrating fishes regeneration programme, fry and smolts of this species are released into the lower Drawa and Płociczna every year. Their return to the places of spawning grounds is evident by spawning nests of adults that are annually catalogued by ichthyologists. Two years after the reintroduction had been started in the Drawa, the presence of 37 nests was observed. The numbers of nests have decreased since 2003 with only four nests observed in 2006. The decline is mainly attributed to intensive marine and coastal fisheries as well as to poaching in the Notec and Drawa Rivers. In 2007, the reintroduction of Baltic sturgeon (Acipenser oxyrinchus) was started, which reproduced in the river until 1936. The first release was carried out with the cooperation between Inland Fisheries Institute in Olsztyn and the Institute of Freshwater Ecology and Inland Fisheries in Berlin (Gessner & Bartel 2000). The reintroduction of sturgeon into the Drawa is a long-term process requiring international cooperation, as the first returns of sturgeons from the Baltic Sea to the Drawa for spawning are expected not earlier than 10 years after release (Kolman et al. 2007). Among invertebrates, 65 species of caddisflies (Trichoptera) have been described in Drawa National Park. One of the recorded subspecies Hydropsyche contubernalis borealis is new for Poland, whereas three species Crunoecia irrorata, Ceralea annulicornis and C. dissimilis have been noted for the first time in the Pomeranian Lakeland. The most precious communities of caddisflies inhabit springs, rivers and dystrophic lakes (Wnuk-Gławdel et al. 2006). In the middle and lower course of the Drawa, a rich

Chapter | 14 Rivers of the Central European Highlands and Plains

fauna of mayflies (Ephemeroptera) has been noted, for example this is the site where Rhithrogena semicolorata and C. rivulorum are found in the Polish lowlands. The presence of the sensitive Baetis calcaratus indicates good water quality (Agapow 1998). The dragonfly and damselfly (Nehalennia speciosa) (Odonata) fauna of the park comprise 47 species, the most valuable ones colonizing peat bogs and lakes with low trophic status such as the pygmy damselfly (Nehalennia speciosa), subarctic darner (Aeshna subarctica elisabethae) and Siberian winter damsel (Sympecma paedisca) (Wnuk-Gławdel et al. 2006). Aquatic molluscs are represented in the National Park by 20 species of water snails and 19 bivalves. The fingernail clams Sphaeriidae are especially rich, represented by the pea mussels Pisidium hibernicum and Pisidium moitessierianum (Agapow 1998). Six native species of unionid mussels have been found, such as the swollen river mussel that dominates in rivers, but also endangered species like the thick-shelled river mussel, swan mussel and depressed river mussel.

14.8.4. Management and Conservation 14.8.4.1 Economic Importance For many centuries, the Drawa has been an economically important transport route for timber. At present, it is only used for tourist purposes (canoeing) and for small-scale hydropower production. On its whole course, the Drawa is a well-known tourist attraction for kayaking and canoeing (Rz˛e tała and Jagus 2007), although mostly used only for weekend tourism. Any boating is forbidden in the National Park from 15th March to 30th June to protect nesting birds. Intensive kayaking tourism and the development of holiday resorts on the riverbanks are major threats to the river. Additionally, the excavation of sand and gravel from the Drawa channel (Wozniak 2000) and fish farming ponds may affect the integrity of the river ecosystem. On the river there exist two hydropower stations at Borowo (downstream of Lake Lubie, built in 1917, storage height 9 m) and at Kamienna (just upstream of the confluence of the Drawa and Plocicna rivers, built in 1899, storage height 8 m), with an installed capacity of about 1 MW each. Both stations interrupt sediment transport and form serious migration barriers for fish and other water organisms. At the Kamienna station, the existing fish ladder does not work because the lower entrance is too far from the turbine outlet. Downstream migration is hampered, as a significant proportion of fish do not survive passage through the turbine of Kamienna (Bartel et al. 2002). A possible emergency flushing of the sediments accumulated upstream of the Kamienna stations forms a serious pending threat to the river. As the Drawa and its tributaries exhibit a rather stable discharge regime, there

569

is little risk of flooding, so that no preventive activities are undertaken.

14.8.4.2 Conservation and Restoration Major parts of the Drawa catchment are protected by the Drawa National Park, the Drawski Landscape Park, the European ecological network Natura 2000, or by other categories foreseen by the Polish Environmental Protection Act. A major goal of these conservation activities is to stop eutrophication processes in surface waters. Within the Drawa catchment, there exist 15 nature reserves covering an area of 5.5 km2 that mainly protect wetlands and peat bogs harbouring stands of rare plants or nesting sites of birds. Additionally, eight protected landscape areas covering 2574 km2 have been established to protect ecological corridors (Kaczanowska et al. 2004). The Drawa National Park, which covers an area of 114 km2 plus 356 km2 of buffer zone, was created in 1990 as one of 23 national parks present in Poland today (Matczak et al. 2004; Wnuk-Gławdel et al. 2006). It is mainly dedicated to protect the pristine forest, wetland and freshwater habitats that remain along the valleys of the Drawa and Płociczna, and fulfils the requirements of IUCN II category. Among these habitats, 14 are included in the Annex I to Habitat Directive as ‘biotopes of special importance of Europe’ (Matczak et al. 2004). These habitats include meso-oligotrophic lakes with stonewort, natural eutrophic lakes with pondweed, dystrophic lakes, rivers with water buttercup, wet and fresh meadows, Corynephorus grasslands and heathlands, raised bogs, calcareous fens with great fen sedge and Davall’s sedge, acidophilous beech forest (Luzulo-Fagetum), rich beech forest (Asperulo-Fagetum), alluvial forests (Alno-Padion), and Cratoneuron petrifying springs. Among the 924 species of vascular plants recorded in the park (Pawlaczyk & Łukaszewski 1997), some of the greatest botanical peculiarities are water-dependent, such as leather leaf and fen orchid. The ichthyofauna constitutes another precious natural element, which includes 42 species of fish from 11 families and two species of jawless fish. Eight species are under strict protection. The Drawski Landscape Park, which covers an area of 414 km2 in the area of Lake Drawsko, was established in 1979 and is dedicated to protect the most valuable parts of the Drawa Lake District having the highest moraine hills of that region, geological peculiarities, cultural monuments, and 48 lakes partially surrounded by pine and beech forests (Kaczanowska et al. 2004). The precious flora of the park includes the rare aquatic and semi-aquatic plant species Lobelia dortmanna, Isoetes lacustris, Litorella uniflora, Myriophyllum alterniflorum and Nuphar pumila. It also harbours 140 species of breeding birds and rich vertebrate and invertebrate faunas, and the ichthyofauna is especially remarkable.

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In the Drawa catchment, there are four protected areas within the European Ecological Network ‘Natura 2000’. The ‘Wilderness Forests upon Drawa’ area (Lasy Puszczy nad Draw˛a, 1868 km2) embraces a part of a large forest complex on the sandur plain in the middle and lower Drawa and is one of the most important habitats for birds in Poland. The ‘Drawa Mainstem’ area (Ostoja Drawska, 1407 km2) comprises a part of the Drawa Lakeland with over 50 lakes offering habitats for least 23 bird species from the Annex I to the Birds Directive. The ‘Lake Lubie and the Drawa Valley’ area (Jezioro Lubie i Dolina Drawy, 132 km2) comprises Lake Lubie as well as portions of the Drawa and Studzienica valleys with a variety of swamp forests and wetland areas, including scattered Sphagnum mires and dystrophic lakes. Lake Lubie harbours Mysis relicta and Pallasea quadrispinosa, two crustacean species that represent rare postglacial relicts. The ‘Drawa Forest Ranges’ area (Uroczyska Puszczy Drawskiej, 658 km2) covers a partially nearly pristine forest complex accompanying the nearnatural river courses of the middle and lower Drawa and Płociczna.

14.9. SYNOPSIS Most catchments in the Central Highlands and Plains were remodelled by the Weichselian glaciation, which covered Scandinavia and a major part of the Central European lowlands bordering the Baltic Sea. It ended 17 000 years before present in the area of Berlin and around 10 000 years before present in central Sweden. Biological colonization that followed the re-warming took several thousands of years, so that, for example beech arrived in the described region clearly after humans. Further, the salt content of the Baltic Sea remained unstable until 4000 years before present. At that time, man already populated the area and influenced inland waters and coasts increasingly, as these were preferred sites for settlement. There, migratory fishes were a source of valuable food that appeared regularly and was relatively easy to catch. In the medieval age, riverine systems were significantly altered by deforestation, contruction of mills and fishing weirs, heavy fishing pressure especially on migratory fishes, and by partial extinction of large mammals foraging in floodplains such as wisent and aurochs. Largescale deforestation led to massive changes in hydrology, nutrient budgets, particulate transport, and charactristic riverine and riparian habitats. In major regions of east Germany, deforestation peaked in the 13th century, which resulted in the formation of a clay layer of 1.5 m height on average (max. 4.0 m) and which still covers the floodplain along the lower Elbe. In the modern era, cities started to massively pollute the rivers flowing through them, and straightening of river channels increasingly became technically feasible. The

PART | I Rivers of Europe

FIGURE 14.16 Historic course of dissolved oxygen (DO) concentrations in major rivers of central Europe (Graph: Federal Institute of Hydrology).

latter resulted in the drainage of vast wetlands and the channelization of most streams and smaller rivers in the lowlands. With the introduction of industrialised farming methods in the 20th century, it became a deeply imbedded view in society from farmers to policy makers that the major service that streams and rivers should provide was to transport water and wastewater to the sea as efficiently as possible. Streams and rivers also became heavily polluted by the discharge of urban wastewaters, with the regional situation depending on population density and the mode of industrial development. A collation of historic data shows that the Oder and Danube rivers were never as heavily polluted as the Rhine or Elbe (Figure 14.16). Preservation efforts were mostly restricted to the construction of wastewater treatment plants to avoid massive impairment in water quality, which would have also jeopardised drinking water supply in some places. Only since the last quarter of the 20th century have further ecosystem services and protection aspects become more considered in the management of streams and rivers, including the retention of floods, the preservation of active flood plains, the provision of habitats and migration routes for fish, and the metabolic functions of rivers leading to their ‘selfpurification’. In many catchments, the problems of pollution with heavy metals, organic micropollutants, or eutrophication from diffuse agricultural inputs are still unresolved or even considered. Moreover, the importance of Central European rivers for aquatic biodiversity is often not seen, especially concerning large rivers that contain rare ecosystems, but underlie various uses and modifications. As the large rivers in Central Europe are all connected by shipping canals, these form avenues for invasive species that are able to cope with the disturbed habitat conditions (Figure 14.17). The example of the restoration project on the Skjern River is to date the largest of its kind in Europe was initiated because it was seen that the economic gain of the reclaimed land was small compared to the loss of ecological integrity and nature values. Many of the negative impacts are now being reversed, although it is still unknown if the

Chapter | 14 Rivers of the Central European Highlands and Plains

571

FIGURE 14.17 Spread of the invasive crustacean Dikerogammarus villosus in Germany, which especially benefited from the opening of the navigational canal between the Danube and Main rivers in 1992 (Sch€oll 2007).

restoration succeeded in the long-term stabilization of endangered populations or if lost species will recolonise the catchment from other refuges.

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PART | I Rivers of Europe

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Chapter | 14 Rivers of the Central European Highlands and Plains

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Chapter | 14 Rivers of the Central European Highlands and Plains

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RELEVANT WEBSITES http://www.fgg-weser.de – River Basin Commission Weser. http://www.ikse-mkol.org – International Commission for the Protection of the Elbe River (ICPER). www.pla.cz – Povodı Labe, Czech Elbe Catchment Authority. http://www.arge-elbe.de/ – Working Committee Elbe, with monitoring data on the Elbe segment in Germany. http://www.mkoo.pl/index.php – International Commission on the Protection of the Oder against Pollution (ICPOaP). http://www.eman.se – Emaf€orbundet (Em river committee). http://swamp.osu.edu/Academics/PDFs/EcoE07.pdf – Description of the Skjern River restoration project. http://www.berlin.de/sen/umwelt/wasser/ogewaesser/index.shtml – Monitoring data of the Spree in Berlin. http://www.dpn.pl/ – Drawa National Park.

Chapter 15

Rivers of the Boreal Uplands Jan Henning L’Ab ee-Lund

Jon Arne Eie

Per Einar Faugli

Norwegian Water Resources and Energy Directorate, Post Office Box 5091 Majorstua, N-0301 Oslo, Norway

Norwegian Water Resources and Energy Directorate, Post Office Box 5091 Majorstua, N-0301 Oslo, Norway

Norwegian Water Resources and Energy Directorate, Post Office Box 5091 Majorstua, N-0301 Oslo, Norway

Svein Haugland

Nils Arne Hvidsten

Arne J. Jensen

Agder Energi Produksjon AS, Service Box 603, 4606 Kristiansand, Norway

Norwegian Institute for Nature Research, Tungasletta 2, N-7485 Trondheim, Norway

Norwegian Institute for Nature Research, Tungasletta 2, N-7485 Trondheim, Norway

Kjetil Melvold

Vegard Pettersen

Lars-Evan Pettersson

Norwegian Water Resources and Energy Directorate, Post Office Box 5091 Majorstua, N-0301 Oslo, Norway

Statkraft Energi AS, Lilleakerveien 6, Post Office Box 200 Lilleaker, N-0216 Oslo, Norway

Norwegian Water Resources and Energy Directorate, Post Office Box 5091 Majorstua, N-0301 Oslo, Norway

Svein Jakob Saltveit Freshwater Ecology and Inland Fisheries Laboratory, Natural History Museum, University of Oslo, Post Office Box 1172 Blindern, N-0318 Oslo, Norway

15.1. Introduction 15.2. Physiography, Land Use and Hydrology 15.2.1. Geology and Land Forms 15.2.2. Land Use 15.2.3. Hydrology 15.3. Aquatic and Riparian Biodiversity 15.4. Glomma river 15.4.1. Physiography, Climate and Land Use 15.4.2. Geomorphology, Hydrology and Biochemistry 15.4.3. Management and Conservation 15.5. Numedalslagen river 15.5.1. Physiography, Climate and Land Use 15.5.2. Geomorphology, Hydrology and Biochemistry 15.5.3. Management and Conservation 15.6. Mandalselva river 15.6.1. Physiography, Climate and Land Use 15.6.2. Geomorphology, Hydrology and Biochemistry 15.6.3. Management and Conservation 15.7. Suldalslagen river 15.7.1. Geomorphology, Climate and Land Use 15.7.2. Hydrology and Water Quality Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

15.7.3. Management and Conservation 15.8. Lærdalselva river 15.8.1. Physiography, Climate and Land Use 15.8.2. Geomorphology, Hydrology and Biochemistry 15.8.3. Management and Conservation 15.9. Jostedøla river 15.9.1. Physiography, Climate and Land Use 15.9.2. Geomorphology, Hydrology and Biochemistry 15.9.3. Management and Conservation 15.10. Stryneelva river 15.10.1. Physiography, Climate and Land Use 15.10.2. Geomorphology, Hydrology and Biogeochemistry 15.10.3. Management and Conservation 15.11. Orkla river 15.11.1. Physiography, Climate and Land Use 15.11.2. Geomorphology, Hydrology and Biochemistry 15.11.3. Management and Conservation 15.12. Namsen river 15.12.1. Physiology, Climate and Land Use 15.12.2. Geomorphology, Hydrology and Biochemistry 15.12.3. Management and Conservation 577

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15.13. Vefsna river 15.13.1. Physiography, Climate and Land Use 15.13.2. Geomorphology, Hydrology and Biogeochemistry 15.13.3. Management and Conservation 15.14. Conclusions and Perspectives

15.1. INTRODUCTION In Europe, the Boreal forest ecosystem centres around 60 N. The northern limit is roughly along the July 13 C isotherm and the southern limit along the July 18 C isotherm. This chapter covers rivers within this region along the western coast of the Scandinavian Peninsula that drain into the Skagerrak or North Sea. A total of 173 major rivers belong to this region of which 10 rivers have been selected to illustrate major characteristics (Figure 15.1, Table 15.1). Although a general climate regime for the Boreal Uplands exists, a great variety of micro-climates occurs that significantly affects local vegetation. The south-eastern and northern watersheds are dominated by birch, pine and spruce, whereas western watersheds are dominated by birch. Watersheds in the Boreal Uplands can be divided into three main groups. Most watersheds contain rivers having considerable gradients, intermediate discharge (annual mean 20–40 m3/s), lakes in the headwaters in mountain regions, and some are even glacier fed. The second group consists of large watersheds mainly situated in the southeast. These rivers are characterized by relative high discharge (>100 m3/s) and long stretches with low gradients; large deep lakes are common. The third group comprises small watersheds in coastal areas. Here rivers have low discharge (<5 m3/s), respond quickly to fluctuations in precipitation, and have intermediate gradients. Rivers of the Boreal Uplands have been of significant importance to humans for centuries as reproductive areas for Atlantic salmon, as a transport medium for timber, and for hydropower. Stone carvings of Atlantic salmon dated from 7000 BP for several rivers document their vital importance for the people. Written documents from 1164 also show the long tradition and importance of catching salmon in boreal rivers. Although probably occurring earlier, rivers used for timber transport are documented from 1500 and were especially important in south-eastern and central areas. Hydropower development began in the early 1900s.

15.2. PHYSIOGRAPHY, LAND USE AND HYDROLOGY

cambrian rock in the southeast is part of the old Baltic shield, a large plate of welded rocks of different origin and age (800–2500 million years old). In the Devonian period (420–360 million years ago), tectonic movement brought the Baltic shield in contact with the Greenland plate, pushing up sea sediments along the contact zone and creating the Caledonian range throughout the Boreal Uplands. A period of crushing, folding and erosion followed, leaving a relatively flat continent. In the Permian period (290–250 million years ago), tectonic activity in continental Europe caused a rift in the area to the west and north of the present Oslo fjord. The subsequent lifting of the Baltic shield and flattening of the Caledonian range in the early Tertiary period (65–1.6 million years ago) laid the foundation for the present topography. Ice ages in the Quaternary period (the last 2–3 million years) dramatically altered the paleo-landscape. Glaciers and their melt waters were major forces transforming the boreal landscape. Continental ice sheets left their footprint in the form of major fjords and valleys with steep lateral gradients, glacier-scoured lake-filled basins in high elevation areas, significant amounts of fluvial sediments in valleys, and large expanses of exposed bedrock smoothed by the moving glaciers. The thickness of material left behind during the Quaternary period varies significantly, although in general the thickness in the Boreal Uplands is sparse and bedrock is often exposed. The upper reaches of rivers draining south-eastern areas of the Boreal Uplands contain thick layers of moraine material. The most characteristic moraine in the Boreal Uplands is the Ra moraine, created 10 600 BP by glacier advancement. It is most pronounced in the southeast and consists of parallel rows of ridges with moraine gravel and cobbles. It is found in coastal areas on both sides of the Oslo fjord and in more distant areas from the coast in the southwest. The last ice age reached its maximum in 18 000 BP with an ice thickness of 3000 m in Scandinavia. The weight of the ice depressed the land and resulted in a marine limit that can be considerably higher than the present sea level. Elevation of the marine limit is highest in Oslo (220 m asl) and Trondheim (175 m asl) regions and declines to <10 m in the southwest and to 50–60 m in the north. The landform varies dramatically from low relief in the east to steep relief in the west and north. Relief is most pronounced along the fjords in western Norway where altitudes of 1100 m can be found within a horizontal distance of <1 km from sea level. Consequently, most rivers and watersheds are often small. However, valleys have lower slopes in the more inland areas of fjords and rivers are larger due to the larger watersheds.

15.2.1. Geology and Land Forms

15.2.2. Land Use

The main geological feature of the Boreal Uplands is the Precambrian bedrock and remnants of the Caledonian anticline formation (Holtedahl 1960; Ramberg et al. 2008). Pre-

The Boreal Uplands is sparsely populated and most inhabitants are in small communities and towns of <50 000 people (Table 15.1). Some people also inhabit the

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Chapter | 15 Rivers of the Boreal Uplands

FIGURE 15.1 Digital elevation model (upper panel) and drainage network (lower panel) of Rivers of the Boreal Uplands.

confined floodplains along river corridors. Hydropower was prerequisite for the establishment of several industrial communities in the early 1900s. For instance, production of inorganic fertilizer in Rjukan began when the Vemork hydropower plant was built in 1910. The altitudinal gradient of the fjords was essential when smelting plants were built in Odda (1906), A rdal (1908), Sauda

(1915), Høyanger (1916) and Mo i Rana (1925). Today, 40% of freshwater areas are affected by hydropower development, providing an annual production of 121 TWh of a potential 205 TWh for all watersheds combined. Presently, 285 parts of or whole watersheds in the Boreal Uplands are protected by a special Protection Plan for Rivers.

580

TABLE 15.1 General characterization of the Rivers of the Boreal Uplands

Numedalslagen

Mandalselva

Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25%) ecological regions

743 41 963 22.2 71.8 1.0 3 60; 62

794 5554 3.5 81.3 2.8 2 60; 62

542 1817 2.6 153.1 4.5 3 60; 62

Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparcely vegetation Wetland Freshwater bodies

0.3 5.4 43.1 29.0 0.5 17.7 1.7 3.0

0.2 2.0 50.2 28.0 0.0 14.2 2.4 3.0

Protected area (% of catchment)

5.3

Water stress (1–3) 1995 2070 Fragmentation (1–3) Number of large dams (>15 m) Native fish species Nonnative fish species Large cities (>100 000) Human population density (people/km2) Annual GDP ($ per person)

Stryneelva

Jostedøla

Orkla

Namsen

961 1462 3.4 134.3 2.4 1 62

1256 1188 1.1 87.8 1.2 1 62

985 537 1.0 134.7 2.3 1 62

1148 865 1.9 116.1 2.2 1 62

712 3053 2.1 90.4 0.8 2 60; 62

487 6273 9.6 120.4 1.1 2 60; 62

0.0 0.0 30.9 50.5 0.0 17.2 0.0 1.4

0.0 0.0 18.1 5.5 0.0 72.0 0.0 4.4

0.0 0.0 17.9 2.1 0.0 78.3 0.0 1.7

0.0 0.0 16.5 2.7 0.0 78.1 0.0 2.7

0.0 0.0 15.2 0.9 0.0 83.6 0.0 0.3

0.0 3.2 64.2 3.3 0.0 22.8 60 0.5

0.0 1.5 49.4 13.7 0.1 31.9 0.0 3.5

0.0 0.0 37.3 18.4 7.4 33.2 1.0 2.7

25.1

11.9

29.7

0.0

27.3

43.1

25.4

11.0

16.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

1.0 1.0

3 17 28 0 0 14 34 228

3 5 11 3 0 13 37 548

3 8 10 4 0 10 38 266

3 4 6 1 0 6 38 400

3 3 8 3 0 2 34 250

For data sources and detailed explanation see Chapter 1.

Suldalslagen

3 8 4 0 0 3 44 118

Lærdalselva

3 3 4 1 0 2 40 977

1 0 5 0 0 6 41 564

3 2 2 0 0 2 41 708

Vefsna 635 4119 6.3 131.6 -0.2 2 62

2 0 7 1 0 4 34 017

PART | I Rivers of Europe

Glomma

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Chapter | 15 Rivers of the Boreal Uplands

15.2.3. Hydrology The hydrological cycle is influenced by several factors such as solar influx, rotation of the earth, distance from the ocean, topography, and general atmospheric circulation patterns. In the Boreal Uplands, topography and distance from the ocean vary considerably among watercourses. In general, the mean annual precipitation is highest in the west and north with values exceeding 4000 mm. In the east and in inland areas of large fjords, the mean annual precipitation is <1000 mm. The maximum and minimum mean annual precipitation during 1961–1990 was 6944 and 128 mm, respectively. Runoff is not evenly distributed throughout the year and can be divided into specific runoff regions (Gottschalk et al. 1979). In coastal areas, with a so-called Atlantic regime, the lowest runoff occurs during May–August and runoff is similar during the other months. The inland regime, situated between the Atlantic and the mountain regime, is characterized by low runoff in winter (January–March), a marked increase due to snow melt in April and May, and low values in summer that increase from August until winter begins. The geographical variation in precipitation is reflected in the flow regime of the rivers (Figure 15.2). In some rivers, the period of recording covers several years prior to and after development of hydropower schemes. Hydropower development has resulted in a significant reduction in the ratio between flood and minimum discharge.

15.3. AQUATIC AND RIPARIAN BIODIVERSITY In general, rivers and catchments of the Boreal Uplands contain few species compared to other European regions. The following taxa are obligate or strongly connected to fresh water with number of limnic species is given in brackets: Porifera (5 species), Mollusca (51), Crustacea (233), Ephemeroptera (48), Plecoptera (35), Odonata (48), Trichoptera (199), amphibians (6), and native fish (32). Within these taxa, 121 species (23%) are categorized as critically endangered (38), endangered (21), vulnerable (17), near threatened (54) or data deficient species (22) (Kalas et al. 2006). The low biodiversity is due to the prehistoric environment. During the Weichselen glacial stage, the present Boreal Uplands were ice covered. In the post-glacial Holocene, the climate rapidly became warmer and the ice front retreated 120–150 m/year (Sørensen 1982). With the withdrawal of ice, rivers gradually became available for aquatic organisms but colonization took place through brackish water or large lakes. An illustration of the colonization process of boreal rivers is given for freshwater fish (Huitfeldt-Kaas 1918). The first group of fish consisted of species able to survive in salt water (e.g. Atlantic salmon, brown trout, Arctic char), and they are found in most west-coastal rivers today. The ice sheet then retreated rapidly around 8300 years BC and

allowed salt water to inundate the exposed land. The Yoldia Sea was created in the southern part of the present Baltic Sea. The salt content of the Skagerrak during this period was a barrier for a second group of freshwater fish to migrate westerly. Species in this group are therefore found in large eastern rivers that were in contact with the Yoldia Sea. In 7500–6000 years BC, the temperature increased markedly and large pines were found in the east that indicated summer temperatures at least as high as today (Birks 1990). The land responded to the reduced weight of ice and started to rise. The first important result was the establishment of the large freshwater Ancylus Sea situated in the present Baltic Sea. The first group of fish (e.g. Arctic grayling, whitefish, pike, perch; called the Finnmark fish) colonizing rivers and lakes were able to survive at lower water temperatures than those entering at a later stage (e.g. cyprinids, vendace, ruffe; socalled the Mjøsa-Storsjø fish). The flora, on the other hand, is best explained by the nunatak hypothesis suggesting that parts of the present flora are survivors from pre-glacial or interglacial times (Dahl 1998). Rivers of the Boreal Uplands have previously been divided into three groups based on boreal vegetation zones (Petersen et al. 1995). First are low-gradient streams in former deciduous forests that now are extensively used for agriculture and overlap with the nemoral vegetation zone (south and west). Second are low-gradient streams in mixed-coniferous forests heavily interspersed by clear and humic lakes, and ponds and wetlands that overlap with the boreal-nemoral vegetation zone (southeast). Finally, highgradient streams in coniferous and deciduous forests of the boreal vegetation zone (southeast and north). In Norway, systematic data collection of the different Atlantic salmon fisheries began in 1876 (Hansen 1986), resulting in >100 years of catch data for most large rivers. A total of 463 distinct populations of Atlantic salmon is recognized (Hansen et al. 2005). The populations have been categorized into extirpated (45 populations), endangered (28), vulnerable (54), reduced production (73), healthy populations (252), and unknown status (11). Physical alterations including hydropower, acidification, and pollution such as from agriculture activities, along with parasites and nonsustainable harvests, are major factors affecting the fisheries.

15.4. GLOMMA RIVER 15.4.1. Physiography, Climate and Land Use The Glomma River basin is in the southeast of the Boreal Uplands and consists of two main branches, Glomma and Gudbrandsdalslagen. The Glomma originates as a small tarn north of the old mining town Røros about 950 m asl and flows into lake Aursunden 691 m asl (44 km2). From the lake outlet west of Aursunden, the river forms rapids and waterfalls and a small hydropower station was built in 1896 to provide electricity for the copper mines. The river then flows over small rapids through a sparsely populated forest valley

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PART | I Rivers of Europe

FIGURE 15.2 Flow dynamics of 10 selected boreal rivers. Name of gauging station and recording period are indicated.

for almost 200 km to about 200 m asl. On this stretch, 10 large tributaries enter the main river, mainly from the west. The river Atna is the largest. From the east, the river Rena enters the Glomma at A mot. The Glomma then flows south-

ward for about 170 km through an agricultural landscape to lake Øyeren 100 m asl (85 km2). The inlet at Øyeren forms one of the largest inland deltas in Scandinavia. Downstream of Øyeren, the river enters a gorge and falls 80 m in about

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Chapter | 15 Rivers of the Boreal Uplands

PHOTO 15.1 Old buildings along the stream Glitra in the upper reaches of Gudbrandsdalslagen in the Glomma river system. (Photo: J.H. L’Abee-Lund).

20 km. The last 70 km of the river are low gradient and wide, having lake-like characteristics. Near the sea it forms the 21 m Sarpsfossen waterfall. The Glomma enters the sea at the town of Fredrikstad (59 N; 11 E). The length of the river is 618 km and it is 8th order in size. Approximately 30% of the catchment is situated above 1000 m asl (i.e. tree line) and 40% between 500 and 100 m asl. There are about 1000 lakes (>1 km2) in the catchment area of Glomma. The river Gudbrandsdalslagen originates from lake Lesjas2 kogsvatn 611 m asl (4.3 km ). The lake has two outlets. The river Rauma starts in west and flows northwest to the town of A ndalsnes. The river from the eastern outlet is rather small, flows through an agricultural landscape and is mostly channelized. After about 60 km it enters a gorge for >5 km and has many rapids. The river then flows >120 km through the typical U-shaped Gudbrandsdalen valley with few rapids to lake Mjøsa. This lake is the largest in Norway at 123 m asl (369 km2) and one of the deepest in Europe at 453 m maximum and 150 m mean depth. Gudbrandsdalslagen is fed by many tributaries originating at more than 2000 m asl in western Norway (Photo 15.1). Some tributaries are glacier fed, and most drain typical fjord lakes at 900–1000 m asl. The highest lake in Norway, lake Gjuvvatn 1835 m asl (0.5 km2), is on the tributary Bøvri. From Mjøsa, the river flows to Vormsund were it merges with the Glomma 30 km upstream of lake Øyeren. The Gudrandsdalslagen is 358 km long and is 7th order in size. Climate varies considerably along the Glomma from upper glacial regions in the northwest to the lowlands in south. The climate can be described as summer warm and winter cold, and with low precipitation based on records (1961– 1990) from the meteorological station at Lillehammer (226 m asl). Mean annual temperature is 2.9 C, averaging 9.3 C and 14.7 C in January and July, respectively. Mean annual precipitation is 720 mm of which 34% occurs during late summer (July–September). One of the driest places in Norway with an annual precipitation of 300 mm is in the upper valley of Gudbrandsdalen, and one of the places with the lowest winter temperature is at Røros ( 50.4 C).

Approximately 600 000 of Norway’s 4.5 million inhabitants live within the Glomma catchment. Highest population densities are generally along the primary and secondary rivers where 10 towns have >10 000 inhabitants each. The lower river basin is more densely populated than elsewhere and has large areas of agriculture. A total of 230 000 persons receive their drinking water from the Glomma. Forest areas of the catchment consist of 50% spruce forest, 35% pine forest and 10% deciduous forest. Spruce forests are most common in the lower catchment and in the Gudbrandsdalslagen catchment, whereas pine is most common in the Glomma catchment (Grønlund 1999). Widespread forestry has resulted in the drainage of 1–3% of lands covered by forests, and more than 17 000 km roads built in forest areas. Areas below 600 m asl are used for agriculture with a dominance of livestock in upper reaches and grains in areas below the marine limit at 125 m asl. The most important agricultural areas for grains and vegetables in Norway are near Mjøsa and Øyeren. About 90 000 da agricultural lands are irrigated with water from the Mjøsa. Mountain areas are important for reindeer (Rangifer tarandus) farming and leisure activities. Areas near tree line that were previously used for farming are now used for grazing cattle.

15.4.2. Geomorphology, Hydrology and Biochemistry Bedrock in the upper Glomma consists of metamorphosed sedimentary rocks of Cambro-silurian age. Bedrock in the middle section, as in the Atna River, consists mostly of slowly weathering light feldspar quartzite. In the lower section, bedrock consists of gneiss and granite. Bedrock in the northwest Gudbrandsdalslagen consists almost entirely of basic Precambrian rocks that are part of the large Caledonian thrust complex known as the ‘Jotundekkene’. This complex resulted in high mountains in the area with summits >2000 m asl. Norway’s highest mountain Galdhøpiggen

584

2469 m asl is found here. During the last glacial retreat, large lakes were formed between the ice divide and water divide. Shore lines and lake sediments show the history of the lakes of which lake Glamsjø resulted in the most well-known canyon in the Boreal Uplands. A low pass in the mountain ridge between the Glomma valley and Rendalen valley probably became free of ice during the final stage in the estab lishment of these lakes. Glamsjø flowed across this pass, forming the famous Jutulhogget canyon. Water with large quantities of variously sized sediment flowed south. Sedimentation processes resulted in coarse material in the upper reaches, whereas smaller sediments were transported downstream to form large glacio–fluvial deposits. Fine particulate matter from the rivers deposited in the marine environment along large areas in the lower Glomma watershed as ice had suppressed the land during the Quaternary. The marine limit is 125 m asl in this area and is almost identical with Mjøsa and the town of Elverum. Hydrology of the lower Glomma is characterized by high flows during snowmelt in May–June. In addition, flow is quite high throughout the year due to river regulation. Occasionally, there are high floods due to rainfall in autumn (Figure 15.2). The flow regime is the same in the upper and lower Glomma, whereas the melting season lasts until July in the Gudbrandsdalslagen. At the mouth of the Glomma, the mean annual discharge is 704 m3/s (specific discharge 16.8 L s 1 km 2). The largest floods in recent years were observed in early June 1995 and early June 1967 with daily discharges of 3580 and 3542 m3/s, respectively. There are a number of observations of large floods before the gauging station was installed at Solbergfoss in 1901. The largest flood occured in late July 1789 was called ‘Storofsen’ and increased the water level in Mjøsa by 10 m compared to 8 m from the 1995 flood. In Øyeren, the water level increased 15 m in 1789, whereas it increased by 8 m in 1995. The reduction in water level was a result of several measures to reduce flood damage in the lower Glomma. Water temperature of the Glomma varies through the year and along the river. During winter (December until late March), temperature ranges from 2 to 0 C, increasing to 8–23 C in summer. Summer temperatures seldom exceed 8 C in the upper river, whereas it is 15–20 C in the lower river. Temperature slightly increases downstream during winter (November–March) and gradually increases during summer. Daily temperature fluctuations in summer decrease significantly along the river because of the increase in total discharge along the river and the presence of lakes that buffer temperature extremes. Water quality differs between the Glomma and Gud brandsdalslagen, as well as longitudinally. Gudbrandsdalslagen is characterized by low conductivity, moderate anthropogenic activity, and slight acidity. Although moderately affected in the river, nutrient surplus over time resulted in eutrophication of the Mjøsa since the early 1960s. Blooms of the bluegreen algae Tychnema bourrelly were common. Algal blooms caused several problems from leisure activity

PART | I Rivers of Europe

and gill netting to the distribution of water for drinking. In 1976, measures were taken to reduce the input of nutrients and pollutants to the lake. Over 1000 million NOK from local and national authorities was invested to build new and renovate older sewage treatment plants. Since the beginning of the 1980s, the algal situation has improved and now the lake is comparable to that in the early 1950s. However, occasional blooms of the diatom Tabellaria fenestrat in autumn indicates that the Mjøsa is unstable, and a surplus load of pollutants or climate change may result in marked changes in the plankton community. Restrictions have been set on the daily human intake of fish caught in Mjøsa. Fish in all trophic levels are affected by toxins. Piscivorous fish (pike, brown trout) may have unacceptably high levels of mercury and PCBs, and planktivorous fish (vendace) and benthic fish (burbot) have high levels of flame retardants (PBDE) (Husø & Thomsen 2006). Thermo-stable coliform bacteria are found near towns at 2–9 colonies/100 mL. In the upper water layer, average total phosphorous is 4 mg/L. The Glomma upstream of the confluence with Gud brandsdalslagen is not influenced by glaciers and the water quality is good. In the lower reaches, concentrations of ions increase due to agricultural inputs and leakage from ancient marine sediments. Transport of suspended material is considerable in the river, where lake Øyeren annually receives 300 000 tons of clay, silt and sand. The transport of larger material is estimated at 100 000 tons annually (Berge 2002). Two of the most intensively studied lakes in the Boreal Uplands are in the catchment. The ecosystem of the subalpine lake Øvre Heimsdalsvatn (1090 m asl) on the Gud brandsdalslagen was monitored from 1968 to 1974 (Vik 1978), and the Atna watershed including lake Atnsjøen (701 m asl) on the Glomma has been monitored annually since 1985 (Sandlund & Aagaard 2004).

15.4.3. Management and Conservation There are records of many catastrophic floods in the history of the Glomma. In 1789, ‘Storofsen’ caused the death of 68 people and >6000 cattle, and 5000 buildings were destroyed. Numerous people immigrated to northern Norway after the flood. The Øyeren was regulated in 1863 to increase the discharge capacity from the lake. However, flooding continued to cause problems and a governmental committee suggested in 1915 that the only way to reduce flooding was to increase the reservoir capacity in the upper catchment and increase the discharge capacity from Øyeren even more. In addition, government-financed construction of dykes along low riverbanks has occurred for decades. Around 30 of the largest lakes in the upper and middle catchment were proposed as reservoirs to reduce flood problems. Between 1917 and 1988, 25 of these reservoirs were constructed and resulted in a total storage capacity of 3568 million m3 or 16% of the annual run-off. Reservoir levels in the mountains are regulated 10–30 m, whereas reservoirs in

585

Chapter | 15 Rivers of the Boreal Uplands

the lowland are regulated 2–6 m. The Mjøsa is the largest regulated lake with a 3.6 m annual amplitude in water level. Annual electrical production is approximately 10 TWh (9% of Norway’s total electrical production) generated from about 50 power stations (2364 MW installed effect). From written sources, we know that coordinated log floating in the Glomma began in 1580. In 1921, a maximum volume of 2.7 million m3 timber was transported down the Glomma and its tributaries. The last log floating occurred in 1985. Although the rivers have lost their importance for timber transport, forestry is still important in the catchment. Several large sawmills are found along the river, and Borregard in the town of Sarpsborg is a world leading company producing wood-based chemicals. The River Continuum Concept predicts that shredders should dominate forested headwaters of rivers, grazers in the middle reaches, and gatherer–collectors in lower reaches. Data of benthic invertebrates from the Glomma support this concept for large rivers in the Boreal Uplands (Lillehammer & Brittain 1987). Similarly, the fish fauna changes dramatically from the upper to lower reaches. A total of 28 species of freshwater fish has been recorded in the Glomma River basin, and the Øyeren has the highest fish species diversity in the Boreal Uplands with 24 species recorded. Cyprinids dominate in number of species and biomass. Six red-listed freshwater fish species are found in the Boreal Uplands. Two of the three red-listed species found in the Glomma are restricted to this watershed. The asp inhabits the Øyeren and the four-horned sculpin is found in the deep waters of Mjøsa. The fish community of Mjøsa consist of 20 species of which salmonids are dominant. Brown trout achieve weights >13 kg and are among the largest in Europe. The number of species decreases markedly further upstream and in Atnsjøen only five species are found. Brown trout and Arctic grayling dominate running water fishes, whereas Arctic char and whitefish dominate fishes in lakes in the upper reaches. Fish passages are associated with run-of-the-river hydropower plants upstream of Øyeren. Fishless lakes have been documented in 24 cases. Atlantic salmon are able to migrate 45 km up to Vama through a side branch as the mainstem is dammed at Sarpsfossen. The inlet delta in the Øyeren has a high diversity of vascular plant and birds (Berge 2002). A total of 50 vascular plant species is recorded, in addition to 275 species of other aquatic species. Substantial numbers of wading birds, swans, geese and ducks use the delta during their spring migration. A total of 260 different bird species have been recorded. Seven species are most numerous at 1000–7000 individuals recorded annually and make the delta ecologically important. Around 40 zooplankton species have been recorded in the oligotrophic lakes (17 species of rotatoria, 9 species of copepods, 11 species of cladocerans) (Halvorsen et al. 2004). The rotifers are dominated by Polyartra vulgaris, Kelicottia longiospina and Conochilus unicornis. Among crustaceans, Cyclops scutifer and Bosmina longispina are dominant, while Holopedium gibberum, Daphnia longispina and Arctodiap-

tomus laticeps are common. Rotifers constitute 80%, copepods 15%, and cladocerans 5% of the total zooplankton number. In terms of biomass, cladocerans make up 60%, copepods 30% and rotifers 10% of the total. The zooplankton community (exemplified by Limnocalanus macrurus, Daphnia cristata, Eudiaptomus gracilis and Cyclops lacustris) in Mjøsa is richer in species number than lowland lakes in general. The biomass of crustaceans in Mjøsa is higher than in other oligotrophic lakes in the Boreal Uplands. Mountain areas in the upper Gudbransdalslagen and Glomma are protected through national parks. Reserves have been established in several inlet deltas, of which the inlet delta at Øyeren has achieved status as a Ramsar area. A total of 26 tributaries and 7 individual river reaches have been protected through the Norwegian Protection Plan for River Systems, and represent a watershed area of 14 630 km2.

15.5. NUMEDALSLA GEN RIVER 15.5.1. Physiography, Climate and Land Use

The Numedalslagen River begins as the outlet of lake Nord mannslagen 1244 m asl (10.9 km2) on the Hardangervidda plateau and initially flows northeast. It flows through 4 large lakes on its way to the lakes Palsbufjorden 749 m asl 2 (19.6 km ) and Tunhovdfjorden 736 m asl (25.5 km2). The terrain is open and above tree line in the upper catchment. No major waterfalls are present. From Tunhovdfjorden the river turns southeast, descending abruptly to the lake Norefjorden at 265 m asl (3.9 km2). The distance from Norefjorden to the river mouth near the town of Larvik is 170 km (59 N; 10 E). The Numedalslagen is 358 km long and is 7th order in size. The river varies in character. For several kilometres the river can be of low gradient only to become high gradient for short stretches. Four major rapids are found along the 72 km from Hvittingfoss waterfall 80 m asl to the river mouth. Three large tributaries arise from the Hardangervidda plateau. Two merge with the Numedalslagen on the plateau – the river Djupa from lake Langesja 1204 m asl (10.8 km2) and the river Heinelva from lake Halnefjorden 1129 m asl (13.7 km2). The third and largest tributary, Uvdalselva from Lake Skarvsvatn 1117 m asl (3.7 km2), merges with the Numedalslagen at Norefjorden. The climate can be described as summer warm and winter cold with low precipitation based on records (1961–1990) from the meteorological station at the town Kongsberg 168 m asl. Mean annual temperature is 4.5 C, averaging 6.5 C and 15.6 C in January and July, respectively. Mean annual precipitation is 820 mm of which 33% occurs during late summer (July–September). A total of 73,400 people inhabit the watershed. Most people live in or near the towns Larvik (56%) and Kongsberg (31%) 95 km from the river mouth. The remaining people live mostly along the river corridor. Historically, alpine dairies were common in the upper catchment where cows were moved from low altitude

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farms to alpine regions in mountain areas. The development of intensive agriculture has lead to a decline in this traditional farming. The wide and open landscape along the Nume dalslagen is used intensively by farmers. Agriculture is especially pronounced in the lower catchment in areas with marine sediments. The marine limit is at 176 m asl about 5 km upstream of Kongsberg. Marine sediments are most pronounced downstream of Kongsberg. Forestry has historically played a significant role within the catchment, although it plays a lesser role today. Industrial activity is restricted to Kongsberg and Larvik.

15.5.2. Geomorphology, Hydrology and Biochemistry Bedrock in the watershed upstream of Kongsberg is from the Precambrian period. Downstream of Kongsberg, bedrock is dated to the Permian. Moraine sediments are found in thick layers in the upper catchment, otherwise this layer is thin or even absent. The well-known Ra moraine, created 10 600 BP by glacier advancement, is 5 km upstream of the Numedalslagen mouth. In the lower Numedalslagen, winter flows are high due to river regulation. While normally the highest flow is during snowmelt in spring and early summer (April–June), high floods often occur in autumn (Figure 15.2). In the upper basin, the flow regime is characterized by high flows during snowmelt in spring and early summer (May–June) and low flows in winter. Rain caused floods are infrequent and small in the upper catchment. In the upper Numedalslagen at the inlet into Palsbufjorden 2 (catchment area 1330 km ), the mean annual discharge is 29 m3/s (specific discharge 22.1 L s 1 km 2), and at the outlet in the fjord the mean annual discharge is 111 m3/s (20.0 L s 1 km 2). At Kongsberg (4265 km2) there are continuous flow data since 1912. The greatest floods during this period were in mid May 1916 and in late June 1927 with daily discharges of 1192 m3/s and 1198 m3/s, respectively. The greatest flood in recent years was in October 1987. Rainfall was especially heavy in the lower catchment that autumn and the recorded discharge was 582 m3/s at Kongsberg. River regulation has reduced the frequency of floods. Water temperature in the lower Numedalslagen (from Norefjorden) varies seasonally and longitudinally. In the lower Numedalslagen, water temperature ranges from 2 to 0 C from December until late March, increasing to 12– 18 C in summer. Temperature gradually decreases downstream during winter (November–March) and gradually increases during summer. This temperature pattern is mainly due to hydropower development in the river with several major storage reservoirs found upstream of Norefjorden that buffer extremes in temperature. In small tributaries in the upper basin, water temperature remains near 0 C from late October until late April, increasing to 20 C in summer. In the upper Numedalslagen at the inlet into Palsbufjorden,

PART | I Rivers of Europe

winter river ice conditions have been recorded since 1973, showing that the river is more or less completely ice covered from late December until mid March or even April. Ice cover begins in mid October and remains until late April in most years. Similar ice conditions are also found on Palsbufjorden. Water quality of the Numedalslagen varies seasonally and longitudinally. Human impacts and erosional processes gradual increase downstream as shown for Tot-P, bacteria and turbidity (Figure 15.3). Significant annual variation is due to flow conditions during sampling and inputs of new sources along the river corridor, as evident in Tot-P concentration in the lower reaches at Bommestad. During autumn 1997 and 2000, several landslides under the marine limit caused erosion and new sources of phosphorous. Turbidity values vary in a similar way. The content of thermo-stable bacteria illustrates a worsening trend in water quality. Skollenborg is 5 km downstream Kongsberg, and presently the water quality does not reach the criteria for bathing and leisure (<100 TBK/100 mL). Bacteria counts in the lower Numedalslagen are mostly acceptable.

15.5.3. Management and Conservation

The beginning of timber transportation on the Numedalslagen is unknown. The establishment of the first ‘town’ in the Boreal Uplands in the late 700s was here in Skiringsal at Kaupang near the mouth of Numedalslagen. It is believed that 400–600 people inhabited Skiringsal in the 800s. Close vicinity to Europe, a secure harbour for trade, and timber for

FIGURE 15.3 Trends in total phosphorus, termo stabile coliform bacteria and turbidity at Bommestad, Skollenborg and Bjønno situated 6, 90 and

Chapter | 15 Rivers of the Boreal Uplands

boat-building were probably factors of importance. Skiringsal is known from the time of King Alfred the Great in the late 800s. The earliest existing Norwegian documents are from the 1500s and give a good description of timber trading in area around the mouth of Numedalslagen (Bergstøl 1964; Traen et al. 2001). The use of water for timber milling was introduced in the Boreal Uplands in the early 1500s. The combination of large forests and power from the river to split timber was a corner stone in the establishment of the only County (Laurvigen County) in the Boreal Uplands in 1671. Iron production was another important industry for the County, beginning in the 1620s. Huge amounts of coal were needed for the production of iron. Timber was cut up to the tree line at Dagali and Skurdalen (900 m asl, 270 km from the river mouth). The maximum annual quantity of timber floated on the river occurred in 1918 at 360 000 m3. A sub stantial decline in using the Numedalslagen for timber transport has occurred since 1920 and timber transport activity ceased in 1979 (Traen et al. 2001). In July 1623, a young shepherd found a silver nugget near one of the rapids on the Numedalslagen. Mining for silver started the next year and King Christian IV decreeded the establishment of Kongsberg. The river provided power and transported needed timber. The silver mine was temporarily closed 1805–1820 and finally closed in 1957. Maximum annual production of silver was 8.5 tons in the first period (1771) and 12 tons in the second period (1920s), and a total of 1300 tons of silver was produced. The first hydropower plant was built in 1910 on the 41 m high Labrofoss waterfall 5 km downstream of Kongsberg. Its purpose was to provide power to the nearby pulp mill. In 1917, construction of the first large reservoir in the upper basin took place. Tunhovdfjorden reservoir was completed in 1920 and provided water to four 25 MW turbines in Nore I plant. The dam was 30 m high and 278 m long. The reservoir impounded three small lakes and had a volume of 352 mil lion m3. Thereafter, the major reservoirs Palsbufjorden (1927), Rødungen (1928), Halnefjorden (1940) and Sønstevann (1967) and some smaller reservoirs (1960– 1980) were built. Halnefjorden and Sønstevann are on the Hardangervidda plateau. Later, the storage capacity of several reservoirs grew by increasing the height of the dam as well as facilities for lowering the reservoir. In river stretches with low gradient from Rødberg to Hvittingfoss, 7 run-ofthe-river-projects were built during 1910–1982. Presently, the catchment contains 13 hydropower plants with a total installed capacity of 606 MW and an annual potential production of 2147 GWh. A total of 11 native and three non-native species of freshwater fish are reproducing in the watercourse. The introduction of the non-native Arctic char is well known. Some specimen was released in 1910 into the lake Breidvatn 1161 m asl that drains into the river Heinelva. Thereafter, the char migrated downstream and developed populations in all lakes, including Kravikfjorden 262 m asl just south of Norefjorden. The non-native gudgeon was recorded for the

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first time in 1991 and reproduces in the river (Eken & Borgstrøm 1994). Two additional non-native species (brook char, pink salmon) have been recorded, but there is no documentation of reproducing populations. Most recorded species inhabit the downstream stretches, and a gradual decline in species number occurs upstream. Cyprinids (except European minnow) use the river up to Kongsberg. Pike are found up to 50 km upstream of Kongsberg to a widening of the river named Bergsjø. Perch and whitefish inhabit Norefjorden 75 km upstream of Kongsberg. Brown trout is the only species occurring naturally in the upper high mountain areas. However, the present status of brown trout in the mountain areas is due to fish stocking in prehistoric times (6000 BP) (Traen et al. 2001). Atlantic salmon is the most important fish species in the watershed. Based on the annual catch, Numedalslagen is one of the five best salmon rivers in the Boreal Uplands. Atlantic salmon can migrate up to Hvittingfoss. During 1876–2003, the mean annual catch of anadromous salmonids (brown trout and Atlantic salmon) was 17 tons (Figure 15.4). Since 1972, Atlantic salmon made up 98% of the catch. The salmon population is dominated by grilse with an average weight during 1990–1999 of 3.8 kg. The fishing methods for salmon have a long tradition in Numedalslagen, being developed in the 12–13th century. Historic fishing techniques make up approximately 60% of the annual catch of which fishing with a net from an anchored timber raft is the oldest method known (Photo 15.2). With the construction of Tunhovdfjorden reservoir in 1917, the first sampling of bottom fauna and fish took place. The goal was to assess the effect of the impoundment on aquatic organisms. Sampling of the bottom fauna was conducted a few years after the reservoir was filled, whereas the study of the fish community continued almost every decade up to the 1990s. The study of Dahl (1926) was the first to describe the detrimental effects of the impoundment on aquatic organisms in the Boreal Uplands. Two major changes have taken place in the fish community of Tunhovdfjorden. First, a piscivorous feeding behaviour has become an important characteristic of the brown trout population. Second, despite fish becoming a significant component of the brown trout diet, the overall growth pattern has remained unchanged. Age specific mean length is the same in 1990s as it was prior to impoundment. However, the individual growth pattern has changed dramatically after impoundment as the CVof age specific length has increased for each age group. This implies an increased number of both slow and fast growers (L’Abee-Lund et al. 2002). The fresh water mussel Maragitifera margaritifera is clas sified as a vulnerable species (Kalas et al. 2006). The distribution of the species is restricted to discrete river stretches downstream of Hvittingfoss. A large population is documented at Hvarnes (30 km from the river mouth) (Simonsen 2005). The upper watershed has several tributaries little affected by human activities. As they are characteristic of larger areas and contain river features of general interest, they have been

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Numedalslagen has been assessed using the protocol developed by the EU Water Framework Directive (Berge et al. 2004). A total of 198 water bodies have been identified of which 31 are heavily modified. The latter group is associated with hydropower development. Run-off and waste from agriculture and towns are major sources of pollution. Two mountain areas, Blefjell and Skrim, are affected by acidification as are some small tributaries throughout the watershed. There is no clear trend that good ecological status of rivers will be achieved by 2015. However, six counties along the river have agreed upon a sustainable strategy for economic, social and ecological interests.

15.6. MANDALSELVA RIVER 15.6.1. Physiography, Climate and Land Use The Mandalselva River basin originates in south Setesdalsheiene at 600–800 m asl. The upper basin is characterized by many small lakes and three main tributaries (Skjerka, Monn and Logna) merge in lake Øre 259 m asl (3.8 km2) to make the Mandalselva (Photo 15.3). The river flows south to the town of Mandal (58 N; 7 E). The Mandalselva is 137 km long and 6th order in size. The river varies in character from low to high gradient within short stretches. The climate can be described as summer warm and winter mild with high precipitation based on records (1961– 1990) of the meteorological station at Mandal 138 m asl. Mean annual temperature is 6.7 C, averaging 0.5 and 14.8 C in January and July, respectively. Mean annual precipitation is 1534 mm of which 26% occurs during late summer (July–September). Historically, small-scale dairy operations were common in the valley, but the development of intensive agriculture has lead to a decline in the number of full time farmers. Forestry also played a significant role within the catchment, but has lesser importance today. Presently, the majority of people (13 000) inhabiting the Mandalselva catchment are in the town of Mandal. The remaining population (5000) inhabit rural areas of the catchment.

15.6.2. Geomorphology, Hydrology and Biochemistry FIGURE 15.4 Nominal catches of Atlantic salmon and anadromous brown trout in six boreal rivers (Source: Statistics Norway).

protected through the Norwegian Protection Plan for River Systems. Six tributaries belong to this protection group, representing a watershed area of 446 km2. In addition, the watershed of Numedalslagen upstream of the waterfall God farfoss upstream of Palsbufjorden, covering an area of 1330 km2, was protected by the establishment of Hardangervidda National Park in 1981.

The Mandalselva is situated over Precambrian bedrock of gneiss and granite. Areas of bare rock in combination with scarce amounts of glacio–fluvial and moraine sediments in high elevation reaches give Mandalselva low buffering capacity against acid precipitation. The river corridor consists of reaches alternating between material of glacio–fluvial, fluvial and moraine origin. The marine limit is 10 m asl. The flow regime of Mandalselva is characterized by frequent fluctuations in discharge. On average, highest flows

Chapter | 15 Rivers of the Boreal Uplands

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PHOTO 15.2 This very old fishing method for Atlantic salmon is still in use in Numedalslagen (Photo: J.H. L’Abee-Lund).

are during snowmelt in April–May and from rainfall in October–November. Flow is relatively high throughout the winter due to river regulation. Floods can occur in all seasons, but rain caused floods in autumn are the largest (Figure 15.2). At the river mouth, mean annual discharge is 84 m3/s (specific discharge 46.1 L s 1 km 2). The gauging station Kjølemo (1757 km2) has been in operation from 1896. The largest floods observed were in October 1929,

November 1931 and October 1987 with daily discharges of 682, 675 and 675 m3/s, respectively. Water temperature of Mandalselva downstream of lake Øre varies seasonally and longitudinally. Water temperature ranges from 2 to 0 C from December until late March, increasing to 14–18 C in summer. Temperatures remain constant downstream during winter (November–March) and gradually increase during summer. Daily temperature

PHOTO 15.3 The upper regions of Mandalselva is characterized by bare rock and scarce amounts of glacio–fluvial and moraine sediments (Photo: S. Haugland).

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fluctuations increase significantly along the river due to hydropower development with major storage reservoirs up stream of lake Øre (Haverstad power stations). The reservoirs buffer the river from extremes in temperature and reduced the yearly temperature amplitude downstream of lake Øre. In small tributaries (e.g. station Kosana;) in the upper basin, the water temperature remains near 1 C from late November until late April, increasing to 20 C in summer. After hydropower regulation only a limited amount of river ice occurs on Mandalselva during winter. From midDecember until late April, ice is present on the lakes and reservoirs in the upper Mandalselva catchment. In Norway, southernmost areas in general, and the Mandalselva catchment in particular, are severely affected by acidification due to high rates of sulphur deposition and slow weathering bedrock. Water quality in the Mandalselva is strongly affected by acid rain. Acidity in the river varied from pH 4.5–5.0 during the 1980s until the mid 1990s. Acidification started around 1900 and peaked in the 1970s. In 1985, a large liming program was initiated in Norwegian salmon rivers. In Mandalselva, acid mitigation measures started in 1997. The program was initiated to improve water quality so that salmon could reproduce successfully, that is by buffering the acid- and aluminium-rich water. The method involves continuously liming with 0–0.2 mm calcite powder released from dispensers that are automatically controlled for discharge and downstream pH using a feedback system. Using this method, pH is now >6.0 and levels of aluminium are no longer toxic to aquatic organisms. Upstream of liming activities, pH is still <5.0 for long periods although water quality has improved generally. In recent years, large areas of the Mandalselva have experienced extreme growths of Juncus bulbosus. This small plant, common in the southwest Boreal Uplands, is normally of little importance. However, when growth conditions improve, the plant can fill the water column up to 3 m in depth. Such extreme growths of J. bulbosus have been recorded in other catchments in the region, and the problem seems to be increasing. The excessive growth lowers habitat conditions for natural biota and limits traditional activities like fishing, bathing and boating. Several hypotheses have been presented to explain the overgrowth such as hydropower development, climate change, acidification and liming. Recent research suggests that the N:P ratio in the water may play a role (Mjelde 2004). Between 1992 and 2005, 3 million NOK has been invested to reduce the problem by cutting the plant and dredging the river substrate to reduce habitat for the plant.

15.6.3. Management and Conservation For centuries, the river was important for all kinds of transportation. People used boats in summer and sleighs in winter to transport goods for sale in Mandal. Timber transportation was the most important use of the Mandalselva. The maximum annual quantity of timber transported on the river was

PART | I Rivers of Europe

in the early 1870s at 80 000 m3. A marked decline in transport took place later, and in 1900 the amount was 40 000 m3. The main causes for the decline were the construction of small sawmills and farmers manufacturing timber for building materials. The first hydropower plant, Tungefoss was built in 1918 to supply power for a small Molybdenum mine. Until the early 1930s, power needs were covered by small local plants and from other power plants in towns. Construction of the first large reservoir took place in 1932, impounding several small lakes with a volume of 124 million m3. It used a 334 m high waterfall and generated 80 MW. The construction of reservoirs ended with the Juvann reservoir being completed in 1961. Juvann has a volume of 142 million m3 and uses a 154 m high waterfall for the Logna powerplant. From 1950 to 1985, Haverstad, Bjelland, Laudal and Smeland power plants were built. At present, the catchment contains seven hydropower plants with a total capacity of 348 MW and a potential annual production of 1700 GWh. Historically, Mandalselva was an important producer of the freshwater mussel Margaritifer margaritifera, and several tributaries had large populations (Dolmen & Kleiven 1997). Because the mussel is vulnerable to poor water quality, acidification in the 1900s decimated the species within the first half of the century. A total of 14 species of freshwater fish of which four are non-native have been recorded in the watercourse. Most species inhabit the downstream stretches of the river, and a gradual decline in species presence occurs upstream. In much of the watershed, trout populations were severely reduced by acidification and even lost from most lakes in the upper basin. Brook trout tolerate lower pH than brown trout and was therefore introduced to many lakes. Today, brook trout is disappearing and brown trout are re-establishing as the water quality gradually improves due to liming and reduced acidification. During the 1990s, European minnow and rudd were found reproducing in the lower basin, and represent a threat to native fish populations. Mandalselva was one of the top 10 Norwegian salmon rivers before acidification led to catastrophic decline and extinction of native salmon in the 1960s (Figure 15.4). During 1876–2003, the mean annual catch of anadromous salmonids (Atlantic salmon and brown trout) was 5.1 tons. As the water quality is now acceptable due to liming, a large program for re-establishing salmon is being carried out. More than 1 500 000 fry (length of 4–6 cm) and 29 000 smolts (length of 10–14 cm) were stocked after 1997. These fish are offspring of wild salmon caught in Mandalselva. In addition, >500 000 eyed eggs were planted in the upper river, based on broodstock from the nearby river Bjerkreimselva. The salmon can migrate 45– 50 km up river to spawn. The upper reaches of the catchment area within the Setesdal Vesthei Ryfylke Nature protection area. The tributary

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Chapter | 15 Rivers of the Boreal Uplands

PHOTO 15.4 The river Suldalslagen is calm for most of its 22 km length (Photo: S.J. Saltveit).

Kosana (220 km2) has been protected through the Norwegian Protection Plan for River Systems.

15.7. SULDALSLA GEN RIVER 15.7.1. Geomorphology, Climate and Land Use

The headwaters of the Suldalslagen River are located at Solfonn 1674 m asl on the Hardangervidda Plateau. From there, the river flows southwest to lake Røldalsvatn 380 m asl (7.4 km2) and south to Lake Suldalsvatn 69 m asl (28.8 km2). The River Suldalslagen starts at the outlet of lake Suldalsvatn and flow for 22 km to the inland of the Ryfylkefjord (59 N, 6 E). Approximately three quart of the catchment area is above tree line at 600–700 m asl and can be considered high-mountain areas. It is a 7th order system and is the longest (112 km) and largest river system in southwest Boreal Uplands (Photo 15.4). Bedrock in the catchment is to a large extent crystalline, mainly granite. In some places the bedrock is covered by the Caledonian fold belt’s deep eruptive rocks, while in other places Cambrio-siluric slate has been preserved in the zone between the shear layer and the bedrock. The landscape is a result of glacial abrasion and sediment erosion and transport. The marine limit in the area is 80 m asl. Suldalsvatn has steeply sloping banks. Suldalslagen flows through a broad uniform valley, divided into two characteristic sections. The lower part is dominated by marine sediments, while the upper part is composed of glacio–fluvial deposits and

moraines. Its waterfalls, rapids and quieter sections provide diversity, excitement and dynamism to the cultivated landscape. Occasionally, steep wooded mountainsides rise up on both sides of the valley, culminating in several characteristic peaks and creating distinctive geographical areas. The climate can be described as summer warm and winter mild with high precipitation based on records from 1961 to 1990 at the meteorological station at Mo (58 m asl). Mean annual temperature is 5.9 C, and averages 2.5 C and 14.7 C in January and July, respectively. Mean annual precipitation is 1970 mm of which 25% occurs during late summer (July–September). Around 3900 people live in the district of Suldal whose administrative centre is Sand. The river flows through an area of intensive, mixed farming. The valley floor in Suldal is mainly used for husbandry, while the side-slopes are used for forestry. The belt of natural vegetation along the banks of the Suldalslagen has been replaced by farmland in many places. The reduced flood risk due to river regulation means that land previously exposed to periodic flooding has now been brought under cultivation. Suldalslagen and its tributary streams are used indirectly (groundwater) as a source of water for Suldal’s inhabitants. In addition, the river is used for irrigation and as a source of water for farm animals.

15.7.2. Hydrology and Water Quality

The flow regime of the Suldalslagen is strongly influenced by hydropower developments in the catchment. At the outlet of Suldalsvatnet, the flow is completely regulated

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(Figure 15.2), while downstream the flow regime is modified by runoff from mostly unregulated areas. The latter is most pronounced during the frequent periods of rainfall or snowmelt in autumn and winter. At the river mouth, the mean annual discharge before regulation was 108 m3/s (specific discharge 73.7 L s 1 km 2), but now it is reduced to 57 m3/s following regulation. The gauging station Suldalsoset, 1302 km2, has been operated since 1904. The largest floods observed were in early October 1943 and early December 1953 with daily discharges of 684 and 664 m3/s, respectively. After regulation, the largest flood was in early June 1997 with a discharge of 292 m3/s. Water temperature in Suldalslagen ranges from 4 to 0 C from November until late March, increasing to 10– 14 C in summer. From the outlet of Suldalsvatn to the river mouth, temperature gradually decreases by 2 C in winter (November–March) and gradually increases by 1 C during summer. The various reservoirs in the catchment mostly buffer extremes in temperature, but the temperature regime is still dependent on river discharge. From mid December until late April, ice can be found on the lakes and reservoirs. Ice production in the river is limited and there are usually 6–41 days of ice cover per year. The area is, in general, vulnerable to acidification, especially through episodes in sea salt deposition. River regulation has increased the risk of acidification, as more acidic water has been transferred into the catchment. For example, water transfer from reservoir Blasjø 930–1055 m asl led to an average decrease in alkalinity in Suldalsvatn from 1986 to 1993 (Figure 15.5). Today, the alkalinity has increased due to reduced precipitation of acidic compounds. In addition, the power plant diversion from Suldalsvatn to the sea has reduced river flow and increased the contribution from more acidic catchments below the dam. Besides the low values in 1994 from sea salt deposition, the river has been limed since 1990 and shows little impact from acidity.

FIGURE 15.5 Alkalinity (mean S.D.) in Suldalsvatn 1981–2003.

PART | I Rivers of Europe

15.7.3. Management and Conservation The river is affected by two major hydropower schemes. The Røldal–Suldal scheme (550 MW) built in the late 1960s is located in the upper catchment and uses 788.4 km2 of the river basin. The Ulla–Førre scheme (2045 MW), completed during the 1980s diverts water from an additional 674.6 km2 to Suldalsvatn. In recent years, there has been a growing interest in the construction of micro and mini power plants on smaller tributaries. Based on discharge during 1970– 1999, the theoretical annual production from hydropower in the whole catchment is 8900 GWh. There are 120 taxa of phytobenthos; Cyanophyceae (28), Chlorophyceae (32), Chrysophyceae (1), Rhodophyceae (3) and Bacillariophyceae (53). Quantitatively, filamentous green algae dominate benthic algae. These algae establish on carpets of liverworts and can cover 100% of the riverbed in places where the cover of liverworts is also high. Benthic algae show relatively high species diversity for all taxonomic groups associated with clean water. A numer ous acidic-sensitive species in the river show that Suldalslagen is little affected by acidification. The number of species has slightly increased after regulation due to more stable flow conditions. Mosses and liverworts are included among the macrophytes. A total of 17 mosses and liverworts have been recorded, dominated by Fontinalis spp. and carpets of liverworts such as Marsupella aquatica and Scapania undulata. Polytrichum commune is also common in the carpets of liverworts in river sections were sedimentation is high. Callitriche hamulata and Juncus supinus are the dominating species of submergent macrophytes. The high density of moss in Suldalslagen after regulation can be attributed to a reduced frequency of large floods, increased winter low flows, less ice cover, and by that no ice-jams. Quantitatively, there probably has been a slight increase in C. hamulata and

Chapter | 15 Rivers of the Boreal Uplands

J. bulbosus due to better substrate conditions such as reduced flow and greater sedimentation. The zoobenthos is dominated by chironomids, mayflies, stoneflies, caddisflies and simuliids in summer (Saltveit & Bremnes 2004). Fourteen species of stoneflies have been recorded. The four most common species are Amphinemura borealis, A. sulcicollis, Diura nanseni and Leuctra fusca. Except for Capnia atra and Taenipteryx nebulosa, recorded as rare, all the species have been recorded during the study period. Seven mayfly species have been recorded. Baetis rhodani dominates and Ephemerella aurivilli is common and has been recorded throughout the study period. The other species are rare. At least 15 species of caddisflies has been recorded from the river, although only a few are abundant. The most abundant species, Polycentropus flavomaculatus, is only abundant in the outlet of Suldalsvatn. The chironomid fauna is the most species rich at 33 species. Oligochaeta consist of 10 species, of which 3 are recognized as abundant. Only one gastropod is present, being rare but found on every sampling occasion. There was a marked increase in zoobenthos density after 2001 from river regulation that reduced spring floods. This density change was attributed to changes in water temperature and discharge, and no changes in composition occurred. Liming also contributed to a strong increase in acid-sensitive species, namely two important mayflies, snails and small mussels. Simuliids and stoneflies were negatively affected by the increase in liverworts, while some oligochaete families and some mayflies showed a preference for moss. Four fish species are present, dominated by Atlantic salmon and anadromous brown trout. Suldalslagen has anadromous fish along its entire length, and is well known for its large salmon. The largest fish ever caught (1913) weighed 34 kg. Atlantic salmon spawn late compared to other rivers of the Boreal Uplands, from mid-December with a peak in early January (Heggberget 1988). Juvenile fish grow slow and Atlantic salmon juveniles spend, in general, 3–4 years in the river before smolt transformation. The average smolt age has decreased from 3.5 years in 1998 to 2.8 years in 2003 due to increases in water temperature. In general, the density of 0+ fish varies significantly among years, whereas densities of 1+ and 2+ age classes are stable but low. Various reasons explain the density variation in 0+ Atlantic salmon. Strong and sudden flow reductions in 1980–1984 and 1989 dramatically reduced juvenile fish density due to stranding. Low densities in 1994–1999 are due to a lack of spawners. A partial density-dependent relationship in Atlantic salmon showed that higher egg densities give rise to more 0+, 1+ and 2+ fish. There is high mortality in both 0+ to 1+ salmon and trout because nursery areas during winter are probably limiting. Nursery areas can also be limiting for 1+ and older fish on account of sand, moss and fine material. For the whole period of record, a density reduction through time was observed for 1+ and 2+ Atlantic salmon.

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Increased moss cover affects the bottom structure. Areas with dense mats of mosses held lower densities of Atlantic salmon juveniles than areas where mosses had been removed. No differences in densities of 0+ salmon were found between areas with and without Fontinalis. It was concluded that the relative increase in mosses in Suldalslagen had a negative impact on juvenile Atlantic salmon fish density (Heggenes & Saltveit 2002). There are, on the other hand, no indications of effects from acid water on juvenile fish populations in the river. Nominal catches of Atlantic salmon and anadromous brown trout exhibit large annual variation, but averaged 2.5 tons from 1876 to 2003. A dramatic decline occurred in 1993 with only 1275 kg being caught (Figure 15.4). The yield remains low, but a slight increase is apparent after 1998 when the catch was at its lowest. From 1979 to 2005 there has been a significant decline in the mean size of Atlantic salmon larger than 3 kg. The mean size declined from 10 kg in 1984 to 4 kg in 1997. A slight increase in mean size is now apparent; being 6.5 kg in 2005, partly due to increased catches of stocked salmon. Suldalslagen is one of Norway’s most well-monitored rivers, with a broad research and development program. Various water flow schemes were tested during 1990–2003 to achieve a generally accepted flow regime that benefited both hydropower and Atlantic salmon. To improve upstream migration, two fish ladders were constructed at the Sandsfossen waterfall in the lower reaches of the river, and variation in summer flows was practiced. Different flushing floods have been tested to reduce sedimentation and the growth of phytobenthos and macrophytes. In addition, salmon fry and smolt have been stocked and the river limed. Stocking was undertaken to compensate for an estimated annual loss of 20 000 smolts of Atlantic salmon (Saltveit 2006). The annual contribution to angling catches from stocked hatchery fish varied from 7 kg in 1996 to 730 kg in 2005. Along the riverbank there are a large number of wellpreserved historic sites, including mills, drying houses, vats and waterwheels. The northernmost sections of the catchment lie within the Hardangervidda Plateau National Park, and there are several conservation areas (Kvanndalen and Dyraheia landscape conservation areas and Drotningheia nature reserve) within the catchment area, making it an area of environmental and cultural importance. Suldalslagen has been used in a number of demonstration projects for the EU Water Framework Directive. Suldalslagen is one of 15 river systems included in an international pilot study whose aim is to assess different European guidelines. The river system has not been given a final assessment, but a trial assessment characterized it as ‘Heavily Modified’. Ecological impacts are mainly caused by the altered flow regime. A full restoration of the natural regime is considered unrealistic due to high costs; although it may be possible to mitigate the adverse effects of flow regulation by restoring parts of the flood regime.

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15.8. LæRDALSELVA RIVER 15.8.1. Physiography, Climate and Land Use The Lærdalselva River basin arises in the Fillefjell and Hemsedal mountain areas at 1920 m asl. Two rivers Mørkedøla and Smedøla merge at Borlaug and form Lærdalselva which flows west 44 km to the ocean at Lærdalsøyri in the inland of Sognefjord (61 N; 7 E). The total river length is 80 km and Lærdalselva is 6th order in size. Most (85%) of the catchment area is situated above 900 m asl. Lærdalselva is one of the most renowned Norwegian Atlantic salmon rivers. The river is the largest Atlantic salmon river in Sognefjord with a natural anadromous section of 24.7 km, which has been expanded by fish ladders to 41 km. Lærdalselva is geographically situated in a zone with a marine climate, but due to high mountains surrounding the valley the climate is continental. The climate can be described as summer warm and winter mild with little precipitation based on records (1961–1990) at the meteorological station at Tønjum 36 m asl. Mean annual temperature is 5.9 C, and averages 2.5 C and 14.7 C in January and July, respectively. Mean annual precipitation is 491 mm of which 32% occurs during late summer (July–September). A total of 2000 people inhabit the catchment, of which 1200 live in village Lærdalsøyri. The Lærdalselva has always been an important passage between eastern and western Norway, and many historic roads through the narrow valley still exist. Agricultural activity dominates the landscape, mostly growing vegetables, fruit, and berries with a special emphasis on raspberries and cherries. Industrial activity is insignificant.

15.8.2. Geomorphology, Hydrology and Biochemistry The river flows through a steep narrow valley. The steeper torrential parts have large stones and boulders. The wide, broad lower parts are dominated by gravel and sand, often in large terraces deposited during different changes in sea level. The marine limit is 125 m asl, and bedrock is dominated by Mylonitt-gneiss. Even when precipitation is low in the valley, it is threefold higher in the mountains that feed the river. The flow regime of the Lærdalselva is characterized by high flows from snowmelt in May, June and July (Figure 15.2). Rain caused floods in summer and autumn are rare and relatively small, and flows are low in winter. Regulation of lakes in the catchment increased winter flows and decreased summer flows, but did not change annual flows in the natural anadromous fish section. Above this stretch, discharge is reduced throughout the year. At the river mouth, the mean annual discharge is 36 m3/s (specific discharge 30.6 L s 1 km 2). Gauging stations in the lower reaches has been operated since 1961, and the largest observed flood was recorded at Sælthun (23 km from river mouth), 790 km2, in early June 1972 with a daily

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discharge of 391 m3/s. However, observations from other stations indicate that the flood in late June 1939 is probably the highest in Lærdalselva since 1900 when observations started. Due to flow regulation in Lærdalselva, water temperature in the lower part (7.2 km downstream of the outlet of production water) is less than the temperature measured upstream at the abstraction point in June–August. Between October/November and March/April the pattern is reversed. Eight kilometre upstream of the intake, water temperature remains near 0 C from late October until April, increasing to 13–18 C in summer. Water temperature extremes in the river are buffered by the reservoirs. Winter river ice condition has not been mapped, but one can expect ice in the river upstream of the outlet of the tailrace from the hydroelectric turbines. Only slight changes in temperature due to regulation have been recorded 12 km downstream from the power station outlet (Brooks et al. 1989). The river and its tributaries are used indirectly (groundwater) as a source of water for inhabitants, irrigation and farm animals. Environmental conditions are considered satisfactory and agricultural runoff is not considered a problem.

15.8.3. Management and Conservation The first hydropower plant, Borgund, was built in 1970– 1974. The main reservoir is Eldrevatn 1105–1116 m asl, which naturally drains into and reduced the flow of the tributary Mørkedøla. Stuvane power plant, built in 1988, uses the head between the power station outlet at Sjurhaugfoss and Tønjum, and is mainly used during winter as most of the water from the outlet at Sjurhaugfoss is used for instream flow during summer in the natural anadromous stretch. Total installed capacity is 274 MW with an annual potential production of 1266 GWh. The algal community is characterized as species poor, dominated in 1982 by the filamentous green algae Ulotrix sp. The low richness is mainly due to cold water, low nutrient content and stable flow conditions. The dominant aquatic moss is Fontinalis antipyretica. Zoobenthos is dominated by chironomids, mayflies (7 species), stoneflies (17 species) and caddisflies (10 species). Species diversity is low and mainly consists of tolerant species. Rare or red-listed species have not been recorded (Gladsø & Raddum 2000). Baetis rhodani, Ephemerella aurivilli and Amaletus inopinatus dominate the mayfly fauna. Capnia atra, Amphinemura borealis, A. sulcicollis and Leuctra fusca dominate the stoneflies. The most abundant caddisflies are Rhyacophila nubila, Polycentropus flavomaculatus and Apatania sp. The non-native European minnow has established populations in addition to four native species. The dominant fish species are Atlantic salmon and anadromous brown trout. In 1989, the first specimen of European minnow was found at Hegg, 40 km from the river mouth (Saltveit 1993), and it has not moved far downstream. The mean annual catch of Atlantic salmon and brown trout during 1876–2003 was

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6.6 tons (Figure 15.4). Since 1969, Atlantic salmon comprised 81% of the catch. The mean weight of salmon during 1990–1999 was 5.6 kg. Sættem (1995) estimated a 50% reduction in the average number of large salmon in the river in the 20-year period after regulation. Fishing was abandoned from 1997 to 2000 due to the finding of the parasite Gyrodactylus salaris. Juvenile fish density has been estimated since 1980, although not continuously. The highest densities of Atlantic salmon were found in the first period with total juvenile densities exceeding 150 fish per 100 m2. Low densities of juvenile Atlantic salmon was evident in 1996, when G. salaris was first registered and after 1999 when the river was re-infected. Brown trout densities show large variation, although being more stable throughout the recording period. There are no differences in growth, smolt age (3.5 years) and smolt size of Atlantic salmon due to regulation (Brooks et al. 1989). No estimates on juvenile fish density exist prior to regulation. Since 1996, the Lærdalselva has been highly affected by the monogenic parasite G. salaris. This parasite is a serious threat to natural juvenile production, causing reduced Atlantic salmon juvenile densities and smolt production, reduced angler catches, and a reduction in size of adult spawners to 6% of normal size (Gabrielsen et al. 2004). Conservation and restoration is mainly directed towards mitigation for possible effects on Atlantic salmon from flow regulation and attempts at eradicating G. salaris. The anadromous section was increased to 41 km by building four fish ladders and a stocking program was initiated (Saltveit 1998). Despite these measures, catches of adult salmon declined, probably because the brood-stock material was taken from an already limited spawning population (Saltveit 1993, 1998). Due to size selectivity, the ladders were mostly negotiated only by male grilse (Saltveit 1993). In 1997, a treatment with rotenone was initiated to eliminate G. salaris by killing all fish present in the river during the treatment. The rotenone treatment failed and the river was re-infected in 1999. In 2003, an in situ experiment with aluminium as an alternative treatment was started. The river was re-infested again in autumn 2007.

15.9. JOSTEDØLA RIVER 15.9.1. Physiography, Climate and Land Use The Jostedøla River basin is on the northern side of Sognefjord. Almost 30% is covered by glaciers, and 70% is over 800 m asl and only 3% below 300 m asl. Eleven glacial arms flow from the glacier Jostedalsbreen, the largest glacier of the European mainland. In addition, there are many small glaciers in the cirques and on mountain sides. Unlike the European Alps, the relief is more subdued with an extensive plateau at 1200–1500 m asl. The glacial valley Jostedal has a deeply incised surface. The Jostedøla catchment has been visited by scientists from all over the world for over 250 years.

The river length is 69 km and Jostedøla, originates as the outlet of lake Styggevatn 1150 m asl (8.3 km2; 58 km from river mouth) and flows southward before entering Sognefjorden at the village Gaupne (61 N; 7 E). In the upper 20 km, the river slope is 47 m/km and the river changes between rapids and waterfalls. Further downstream, the river is low gradient with an overall slope of 6 m/km, although rapids and waterfalls are still present. The Jostedøla is 5th order in size. The climate can be described as summer warm and winter cold with high precipitation based on records (1961– 1990) at the meteorological station at Myklemyr 98 m asl. Mean annual temperature is 3.4 C, averaging 7.1 and 14.0 C in January and July, respectively. Mean annual precipitation is 1350 mm of which 25.7% occurs during late summer (July–September). Approximately 1500 persons inhabit the catchment, of which 1100 persons live in Gaupne. The countryside of Jostedalen has provided a livelihood for people for centuries. Hunting and farming have been the basis for communities close to Jostedalsbreen. Agricultural activity dominates land use in the valley, but old traditional summer farms are not in use today. The area is well known, and 50 000 people visit the area each year to view the glaciers and experience nature.

15.9.2. Geomorphology, Hydrology and Biochemistry Bedrock is extremely old and belongs to the Caledonian chain. The northern part of the catchment is dominated by granites. Various kinds of gneiss are common. In the eastern part, bedrock is overthrusts of phyllite and mica schist. The overthrust was formed as a result of large movements in the earths crust in the Palaeozoic. Two main fissure systems are present in the area, one going north–south (the main valley) and the other east–west visualized by the tributaries. Ice ages in the Quaternary dramatically altered the paleolandscape. The Jostedal valley offers spectacular scenery, mainly shaped by glacial erosion. Glacial faults and fractures underneath the glaciers have favoured erosional forces, carving out valleys, hanging valleys, cirques and mountain passes from the ancient mountain plain. Cross-section profiles indicate a transition from the open U-shaped valley to deeply eroded, narrow and canyon like areas. The marine limit is 99 m asl. Glacier volumes in the area have been subject to large variation over postglacial time. The geological features produced by the melting Nigardsbreen, an outlet of the glacier Jostedalsbreen, from west to the Jostedal valley has been monitored since 1710. From 1710 to 1748 the glacier advanced almost 3000 m. A period of retreat followed and until 1988; the retreat was 4.5 km. Creation of a lake took place between the glacier and the distinct moraine ridge after 1936. Since 1988, the glacier has advanced 240 m. The response time for Nigardsbreen is 20–30 years. Thus, large amounts of

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PHOTO 15.5 The Nigard valley with lines illustrating the front of the glacier in 1750, 1850, 1930 and in 1990 when photo was taken. (Photo: B. Wold).

snow at the end of the 1980s will be evident at the glacier tongue after 2010 (Photo 15.5). Measurements taken after 1968 indicate an average of 11 800 metric tons of material are deposited annually on a delta at the inlet of the lake, whereas 10 500 metric tons of suspended material flows into the lake itself. Only 22% of this material is transported by the glacial river down to Gaupne (Østrem et al. 2005). Upstream of the junction of the river from lake Nigards vatn and Jostedøla in the main valley is Fabergstølsgrandane, the largest remaining active sandur of the European mainland. This very dynamic area displays major ecological gradients, extending from pioneer plants and primitive fauna that live at the edge of the glacier in the north to the more developed and diversified flora and fauna in the south. Extensive changes in water level have significant consequences on the vegetation. Species tolerating regular flooding are found on the banks of rivers, whereas those that do not are at higher levels. The flow regime of Jostedøla is characterized by high flows throughout the summer (June–August), due to the high coverage of glaciers in the catchment, and normally low

flows in winter (Figure 15.2). Normally, the highest floods occur in late summer or early autumn due to rainfall combined with melting of the glaciers. At the river mouth, the mean annual discharge is 60 m3/s (specific discharge 69.4 L s 1 km 2) (Photo 15.6). The gauging station at Myklemyr, 575 km2, has been operated since 1978. The largest floods observed were in mid-August 1979 and in late August 1997 with daily discharges of 409 and 327 m3/s, respectively. During the flood in 1979, the river rose 5 m in 16 h in one of the valleys near the outlet in the fjord. Since 1989, some discharge is diverted through the hydropower plant and is not registered at Myklemyr. Hydropower development has resulted in a marked reduction in mean annual discharge from 60 to 35 m3/s at the outlet to Sognefjorden. Water temperatures of Jostedøla are characterized by relatively low summer temperatures (4–7 C, June–August) due to large amounts of glacier melt water in the river (Figure 15.6). A slight increase in temperature occurs along the river (between the stations at Faberstølen and Myklemyr). The unregulated Jostedøla has even lower summer temperatures. Water temperatures in the rivers Breelvi and Krundøla that

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PHOTO 15.6 (a) The situation at the outlet of Jostedøla at Gaupne in 1974 in an early phase of hydropower development (Photo: P.E. Faugli). (b) The situation at the outlet of Jostedøla at Gaupne in 1990 after the fulfilment of the hydropower development (Photo: P.E. Faugli).

flow into Jostedøla are also low in summer due to large amounts of glacier melt water. The decrease in water temperature from mid June in the river Breelvi is most probably due to an increased amount of glacier melt water that kept low temperatures in lake Nigardsvatn. Between October/November and March/April, water temperature remains near 0 C and the river is ice covered (Figure 15.6).

15.9.3. Management and Conservation The first hydropower scheme was put into operation in 1978. In 1989, the dam at lake Styggevatn was completed and the Jostedal hydropower station was operational in 1990. Styggevatn has an annual fluctuating water level of 90 m and a total head of 1163 m. A tunnel from Styggevatn penetrates the mountain such that all tributary waters from the east are diverted as water supply to the turbine. Tributaries west of the main valley have not been affected and they contribute the main river water. At present, the catchment contains two hydropower plants with a total installed capacity of 398 MW and an annual potential production of 1249 GWh.

The cold microclimate in Jostedøla makes the river a unique habitat for aquatic organisms. Upstream of Fabergstølsgrandane, four chironomid species new to science have been recorded (Schnell & Sæther 1988; Sæther 1990). Taking into consideration the extreme ecological conditions that many chironomid species can tolerate, it is reasonable to believe that species in this genus may have been the first organisms to colonize the rivers. These species may well be the remains of an ancient original fauna that existed along the perimeter of the mainland ice sheets after they retreated some 9000 years ago. The low water temperature in Jostedøla makes the river of little importance for production of anadromous fish species. Only two fish species are present in the watershed. The nominal catch of Atlantic salmon is <100 kg/year, and the catch of anadromous brown trout may exceed 500 kg in some years. The glacial retreat area of Nigardsbreen has been protected as a Nature reserve since 1983. Jostedalsbreen National Park was established in 1991 and includes all tributaries on the western side of the valley and its glaciers.

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FIGURE 15.6 Mean water temperature (black line, shaded area illustrates min and max values) in three boreal rivers. Vefsna: Vefsna I at 10 km from the river mouth (Kvalfors), Vefsna II at 63 km (Elsvasselva), Susna I at 85 km (Ivarrud), Susna II at 96 km (A slia), and in the tributary Mjølkelva 90 km. Stryneelva downstream of Strynevatn and in the tributaries Erdalselva 25 km and Hjelledøla 24 km from the river mouth. Jøstedøla: Jostedøla I at 13 km (Myklemyr) from the river mouth, Jostedøla II at 22 km (Fabergstølen), and in the tributaries Breelvi 12 km and Krundøla 15 km.

15.10. STRYNEELVA RIVER 15.10.1. Physiography, Climate and Land Use The Stryneelva River basin is in the innermost part of the Nordfjord in western Norway (62 N; 7 E). Several glaciers, including a part of the largest glacier in continental Europe, Jostedalsbreen, are located within the catchment. The low catchment is dominated by the long, narrow and deep lake Strynevatnet 29 m asl (area 21 km2, max depth 230 m), a typical west Norwegian fjord lake surrounded by high mountains. Both the valley and the fjord were formed by glaciers during the ice age, and today the lake is a continuation of the

fjord, being separated by the 9 km river. The river is 54 km long and 5th order in size. The Stryneelva drainage consists of four main valleys (Glomsdalen, Videdalen, Sunndalen and Erdalen), all draining to Strynevatnet. From Strynevatnet, the river Stryneelva first flows rather rapidly, but later it becomes more tranquil in several meanders until the outlet to the sea at the village Stryn. The delta is used for industry and settlement. Downstream of Strynevatnet, and also partly on the shores of the lake, the bottom of the valley is dominated by agriculture. Valley side-slopes are mostly covered by deciduous forest. They are rather steep, and hence the distance to alpine areas is short. Tree line is at 800 m asl. More than 50% of the

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catchment is >600 m asl, and the highest mountains reach 2000 m asl. The climate can be described as summer warm and winter mild with intermediate precipitation based on records (1961–1990) at the meteorological station at Oppstryn 201 m asl. Mean annual temperature is 5.7 C, averaging 1 and 13.5 C in January and July, respectively. Mean annual precipitation is 1137 mm of which 24% occurs during late summer (July–September). About 3000 people inhabit the catchment, of which about 2200 live in the village Stryn at the river mouth. Almost the entire population lives in the lowlands in the main valley, <100 m asl.

15.10.2. Geomorphology, Hydrology and Biogeochemistry Three of the four largest tributaries to Strynevatnet are strongly influenced by drainage from glaciers. Hence, they are characterized by high summer flows, low winter flows, and considerable transport of sediments. Because of this, the rivers have a green to grey colour in summer. Sediment transport has resulted in several highly developed fluvial formations such as deltas, river plains, and sand banks. Such formations are especially noticeable in the Sunndalen valley. The flow regime of the Stryneelva is characterized by high flows throughout the summer (June–August), due to the high coverage of glaciers in the catchment, and normally low flows in winter (Figure 15.2). There are high floods both in summer due to snowmelt and melting from glaciers, and in autumn due to rainfall. At the river mouth, the mean annual discharge is 32 m3/ s (specific discharge 59.8 L s 1 km 2). The gauging station Strynevatn (484 km2) has been operated in the period 1902–1924 and since 1967 except 1994. The highest observed floods were in early October 1908 and in early July 1914 with daily discharges of 217 and 192 m3/s, respectively. The average summer temperature in Stryneelva (downstream of Strynevatnet) increases from 8 C in early June to 12.5 C in mid August (Figure 15.6). Stryneelva is relatively warm during winter and water temperature seldom drops to 0 C; average winter temperature is 2 C. Water temperature of the rivers Erdalselva and Hjelledøla that drain into Strynevatnet is characterized by relatively low summer temperatures (6–8 C, June–August) due to glacier melt water. Erdalselva also seems influenced by groundwater as shown by its high winter temperature.

15.10.3. Management and Conservation The Stryneelva catchment is protected through the Norwegian Protection Plan for River Systems. The Jostedalen Natural Reserve, including the glacier Jostedalsbreen, which is the largest glacier in continental Europe, is partly

located in the catchment. One of the largest nature reserves with warm adapted deciduous forest (including elm and linden) in Norway is located at Flo on the northern shore of Strynevatn. Five fish species are present in the watershed (Jensen 1983). Economically as well as recreationally, Atlantic salmon and anadromous brown trout are by far the most important. In addition, resident brown trout, Arctic char, eel, and three-spined stickleback are present. Arctic char are found only in Strynevatn. Anadromous fishes can ascend the Stryneelva up to Strynevatn and 5 km further upstream to the river Hjelledøla where there is an impassable waterfall. Upstream of this waterfall, resident brown trout is the only fish present. Stryneelva is famous for its Atlantic salmon sport fishery, both for the large size of the salmon and as a special area with spectacular surroundings. Conditions for sport fishing are well arranged, among other things by fish quays; and the river holds several highly attractive fishing spots. Normal catches are 100–300 salmon annually, with average weights of 7.5 kg. Mean annual catch in the period 1884–2003 was 2 tons of which Atlantic salmon made up 58% in 1979–2003. The relatively high incidence of brown trout in the catch can be attributed to the relative low water temperature. The common frog (Rana temporaria) is the only amphibian present in the catchment. The common toad (Bufo bufo) has been found further west in the same fjord system (Dolmen 1983), and may be present in the Stryneelva as well.

15.11. ORKLA RIVER 15.11.1. Physiography, Climate and Land Use The Orkla River originates as the outlet of Orkelsjøen 1064 m asl (2 km2) and flows north into the Trondheimsfjord (63 N; 10 E). The total river length is 182 km and the second largest of the 43 rivers draining into this fjord. The river has several major tributaries and few small lakes. Orkla is 7th order in size. The catchment is narrow with a Vshaped profile in the south and the river has numerous rapids. Further north the valley is wide and U-shaped, and the river has a gentle slope (6 m/km) and meanders. The climate can be described as summer warm and winter cold with low precipitation based on records (1961–1990) at the meteorological station at Meldal 142 m asl. Mean annual temperature is 3.5 C, and averages 6.4 C and 13.1 C in January and July, respectively. Mean annual precipitation is 915 mm of which 28% occurs during late summer (July–September). A total of 17 000 people inhabit the catchment with 60% living in the town Orkanger at the river mouth. The remaining population lives almost exclusively along the river corridor. The wide and open landscape along the river is used intensively by farmers. Agriculture is especially pronounced in the lower watershed in areas with marine sediments. Remnants of farms dated back to 500 BC– 1000 AD are documented.

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15.11.2. Geomorphology, Hydrology and Biochemistry The catchment is in the Trondheim region and is characterized as a broad axial depression in which metamorphosed Cambro-silurian sediments have been preserved from erosion. At Løkken, the largest pyrite deposit is found in Norway as an elongated lens-shaped body of 2 km length in the greenstones of the Støren group. In the south and north, small bodies of acid bedrocks of mainly granite are present. Moraine sediment is present in thick layers in the valleys, otherwise this layer is thin or absent. The marine limit is 175 m asl 50 km upstream of Orkanger. In Orkla, the winter flow is quite high due to hydropower regulation. Normally the highest flow is during snowmelt in early summer (May–June), but rain caused floods in late summer and autumn are also quite common (Figure 15.2). At the river mouth, the mean annual discharge is 67 m3/s (specific discharge 22.0 L s 1 km 2). At Bjørset dam (2317 km2), there are continuous flow data since 1912, but the gauging station was closed in 1974. Now the station Syrstad (2278 km2) is the main gauging station in the lower Orkla. The highest floods observed were in mid June 1944 and in late August 1940 with daily discharges of 1256 and 1133 m3/s, respectively. Flow regulation has reduced the frequency and magnitude of floods. Water temperature of the river is quite variable both longitudinally and seasonally because of flow regulation. Water temperature is dependent on climate and the amount of production water added to the river. In general, three major hydropower stations along the river, and a large storage reservoir at higher elevation, decrease summer temperatures and increase winter temperatures in the river. Large daily fluctuations in temperature occur. In the lower Orkla, water temperature ranges from 2 to 0 C from December until late March, increasing rapidly to 12–18 C in summer. As for water temperature, ice conditions during winter are quite variable along the river and through time. Usually ice was present in the upper river before establishment of the first hydropower station at Ulset. For the next 30–35 km, the river is mostly ice free due to the input of two hydropower stations. Some ice may be found in the lower 40 km of the river. The mining industry at Løkken resulted in toxic run-off that substantially contaminated the small creek Raubekken with copper and zinc. One consequence was the characteristic red colour that is reflected in the name (‘The Red Creek’). Three kilometres downstream of the confluence of Raubekken and Orkla, high values of copper and zinc were still evident until 1982. A significant reduction began in 1982 as a consequence of different remedial measures taken in the mining area (Jensen et al. 1998). A reduction in heavy metal pollution has occurred in the lower Orkla (17 km) and spawning and rearing areas for Atlantic salmon are now present.

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Water quality is slightly alkaline (pH 7.3–7.4) and relatively high in ions (conductivity 50–90 mS/cm). The content of phosphorus in the river increased after filling of the reservoirs. In 1980 (before regulation), the average content of phosphorus was 4 mg/L, a short time after regulation (1982) the phosphorus content increased to 10–14 mg/L. After 1987, phosphorus decreased and varied between 3.5 and 6 mg/L between 1990 and 1999.

15.11.3. Management and Conservation Special geology caused mining activity at Kvikne in the south and at Løkken in the north. Kvikne copper mine started about 1630 and is one of the oldest copper mines in Norway. The mine was rich in copper and produced about 7000 tons of copper until the mining venture abruptly ended in 1789 when the ‘Storofsen’ flood filled the mine with water. Near the copper mine is a steatite pit mine with >2500 years of pottery history. The pyrite deposit at Løkken initiated 300 years of mining industry. Mining for copper started in 1654, and up to 1845 a total of 11 300 tons of copper had been produced. From 1908 to the termination in 1987, the mine produced 480 000 tons of copper, 480 000 tons zinc, 460 tons silver, and 4.8 tons gold. River substrate is a valuable resource for construction needs. During 1977–1987, 1 million m3 of gravel was removed from the river between the mouth and Svorkmo, a distance of 15 km. The excavation lowered the river bottom up to 2 m in some places and exposed clay of marine origin. The river is channelized in these areas, whereas previously it was wide and gravel dunes were common. The Orkla was subject to major hydropower development during 1978–1985. Two of the four reservoirs were established by damming the tributaries Inna and Grana. These manmade reservoirs (6.5 km2 surface area, 650– 800 m asl) have amplitude in annual water-level fluctuation of 35 and 40 m, respectively. Each reservoir feeds hydropower plants with a total installed capacity of 265 MW. In addition, a run-of-the-river project has been built at Svorkmo (55 MW installed capacity) 17 km from the river mouth. Total annual potential production for all hydropower facilities is 1371 GWh. A total of seven fish species are recorded in the catchment. One of these, the non-native European minnow, has established reproducing populations. The European minnow was recorded for the first time in 1965. Atlantic salmon is the most important species both in number and value. The distribution of Arctic char is restricted to some small lakes in the mountains. Atlantic salmon may migrate up to Stoin at 260 m asl and 88 km from the river mouth. During 1876– 2003, the mean annual catch of anadromous salmonids (Atlantic salmon and brown trout) was 8.2 tons (Figure 15.4) of which Atlantic salmon comprised 93% of the catch in 1983–2003. The salmon population is dominated by grilse and 2-sea-winter fish, and mean individual weight during

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1990–1999 was 4.5 kg. Angling for salmon provides an annual income of 5–7.5 million NOK to the region. Studies of the Atlantic salmon population in the Orkla started in 1979 with a focus on timing of smolt migration and quantification of smolt production (Hvidsten et al. 2004). The annual smolt production has varied between 4 and 10.8 smolts per 100 m2 with an average of 6.5. Nineteen years of data give a unique opportunity to describe and quantify a number of processes regulating smolt production. High levels of phosphorous and high minimum flow during winter contributed to an increased smolt production, whereas increased smolt age due to altered water temperatures reduced smolt production. Hydropower development has led to a net increase in smolt production of 10–30%. Most Atlantic salmon smolts leave the Orkla between May 12 and June 3, although migration takes place from late April to mid June. Discharge and water temperature are the two most important factors affecting the timing of Atlantic salmon smolt migration. Increases in both variables stimulate smolt to migrate. The common toad (Bufo bufo) and smooth newt (Triturus vulgaris) have been recorded but appear in very low numbers. The smooth newt is near threatened according to the Norwegian red list (Kalas et al. 2006). The tributary Svorka (catchment area of 320 km2) has been protected through the Norwegian Protection Plan for River Systems. Svorka drains a variable habitat of bogs and coniferous forest. In the south, the elevation reaches 1200 m asl and the river shows high variability of meanders along low slope stretches and rapids and waterfalls in steep gradient stretches such as in canyons. Several nature reserves have been established; lake Urvatn (coniferous forest; 1.8 km2) and Litlbumyran (wetland; 1.6 km2). The Orkla has been subject for assessment according to the method developed by the EU Water Framework Directive (Jonsson et al. 2004). A total of 135 water bodies have been identified in the Orkla catchment of which 37 are characterized as heavily modified. These systems are in the lower reaches of the Orkla where gravel excavation has taken place and with hydropower development (reservoirs, water intake, and river stretches downstream of these encroachments).

15.12. NAMSEN RIVER 15.12.1. Physiology, Climate and Land Use The Namsen River originates as the outlet of lake Store Namsvatn 455 m asl (39.5 km2) and initially flows north for 10 km. The river then bends southwest and reaches the ocean at the town of Namsos (64 N; 11 E). Store Namsvatn is fed by tributaries arising from small glaciers in Bjørgefjell National Park at 1350 m asl. In addition to Store Namsvatn, one large lake (Tunnsjøen, 100 km2) and seven smaller lakes are found along three major tributaries. The Namsen is 229 km long and 8th order in size.

Two major tributaries merge with the Namsen from the east: 80 km from the river mouth Tunnsjøelva (annual mean discharge 16 m3/s) originating from lake Tunnsjø 358 m asl, and 45 km from the river mouth Sanddøla (annual mean discharge 62 m3/s) originating from lake Sandsjøen 409 m asl (15.1 km2). The third major tributary Bjøra (annual mean discharge 36 m3/s) flows from the north and merges with the Namsen 25 km from the river mouth. The Bjøra drains five small lakes (6–203 m asl) in a low elevation area. The slope of the river is steep in the upper reaches where the elevation is reduced by 190 m over 16 km. Further downstream, the Namsen is mostly tranquil with three waterfalls (Trongfoss 19 m, Aunfossen 29 m, Fiskumfoss 35 m). The slope of the lower reach is 50 m over 45 km. Lower reaches of the Namsen catchment are in the boreal rainforest. This ecosystem has its main European distribution in this area. The forest is connected by ravines below the marine limit and consists almost completely of spruce intermixed with swamps. A high number of epiphytic lichens are found in the rainforest of which several have a geographical distribution restricted to this specific type of forest. The climate can be described as summer mild and winter cold with high precipitation based on records during 1961– 1990 at the meteorological station at Skogmo (35 m asl). Mean annual temperature is 3.3 C and averages 7.5 C and 13.8 C in January and July, respectively. Mean annual precipitation is 1375 mm of which 26% occurs during late summer (July–September). A total of 10 200 people inhabit the rural areas of the catchment. In addition, a part of the town Namsos (3000 inhabitants) is recognized as belonging to the catchment. Namsos was established as a port of shipment for timber and attained status as town in 1845. Agricultural activity dominates present land use in the catchment, especially in the lower Bjøra and 45 km upstream of the Namsen. The marine limit is at 165 m asl. Forestry has played an important long-term role for the people in almost the entire catchment. Industrial activity is insignificant.

15.12.2. Geomorphology, Hydrology and Biochemistry Bedrock in the lower reaches (45 km) is from the Precambrian period. Further upstream, bedrock is quite heterogeneous and consists mostly of metamorphic rocks created during the Caledonian period. The bedrock is mostly covered by a thin and non-continuous cover of moraine material. On average, the flow in the Namsen and its tributaries is highest during snowmelt in May and June (Figure 15.2). The largest floods are rain caused, sometimes combined with snowmelt in autumn and winter. Flow is relatively high throughout the winter due to hydropower development in the upper catchment. At the river mouth, mean annual discharge is 304 m3/s (specific discharge 48.5 L s 1 km 2). The largest floods since 1961 at the gauging station Bertnem (5163 km2) were

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recorded in late November 1961 and in early December 1962 with daily discharges of 2741 m3/s and 2811 m3/s, respectively. Based on observations further up in the basin, these were the two highest floods in the river since 1908. Leakage from the abandoned Skorovas mine is the only known pollutant in the watershed except run-off from agricultural activity. Leakage of copper reached its maximum in 1993 with 100 mg/L in 1993, but has decreased to <20 mg/L in 2002.

15.12.3. Management and Conservation Due to climatic conditions and elevation (tree line at 700 m asl, 60% of the watershed is below 600 m asl and only 5% above 900 m asl), forests in the watershed have been characterized as productive. The Namsen has been very important in the transportation of timber up to 1970s. The annual volume of timber varied from 100 000 to 600 000 m3 with the highest figures in 1950–1960s. The Skorovas mine near Tunnsjø was in operation from 1952 to 1984. The total production was 7–8 million tons of ore containing copper and zinc. The first hydropower plant was built during 1941–1946 to use the 35 m waterfall Fiskumfoss. Afterwards, another 7 plants have been put into operation. Two major lakes in the watershed, Store Namsvatn and Tunnsjø, are regulated with amplitudes of 14 and 5 m, respectively. Store Namsvatn is dammed at its natural outlet and the water is now diverted through a tunnel and a turbine to lake Limingen. This lake naturally drains into Sweden and is regulated with 8.7 m amplitude. Most of the water is returned to the Namsen via a tunnel into Tunnsjø. Total installed capacity is 290 MW with an annual potential production of 1740 GWh. In total, eight native and three non-native species of freshwater fish inhabit the catchment. Among the non-native species, pink salmon have been caught by anglers, but there are no indications that reproduction has occurred. Whereas the non-native grayling and European minnow have established reproducing populations. Of the native species, Atlantic salmon is the most important fish in the watershed. Three watercourses in the Boreal Uplands contain populations of Atlantic salmon that complete their lifecycle in freshwater. The Namsen is one of them, but contrary to all other known European populations of non-anadromous Atlantic salmon, the population in Namsen lives exclusive in running water (Berg 1985). Compared to anadromous Atlantic salmon, which may reach 30 kg in Namsen, the non-anadromous type may exceed 300 g. Anadromous Atlantic salmon inhabit the Namsen to the Fiskumfoss waterfall 72 km from the river mouth. The non-anadromous population naturally inhabited the 87 km reach of the Namsen between Fiskumfoss and a steep waterfall at 290 m asl. The present distribution is reduced to 46 km due to hydropower development and the building of weirs that reduced the amount of the preferred habitat, that is rapids. The formation of the non-anadromous

PART | I Rivers of Europe

population of Atlantic salmon took probably place in the early phase of deglaciation prior to the establishment of the waterfall at Trongfoss as a migration barrier around 9500 BP (Kjemperud 1981). The mean annual nominal catch of anadromous salmonids (brown trout and Atlantic salmon) is 14 tons (Figure 15.4). Since 1969, Atlantic salmon comprised 92% of the catch. Although specimens often reach 20 kg, the average weight of salmon is 4 kg. The freshwater mussel Margaritifera margaritifera (Vul nerable, Kalas et al. 2006) is found in several tributaries. Except the vigorous population in the Bjøra, their status is unknown. The smooth newt Triturus vulgaris (Near threat ened, Kalas et al. 2006) has been recorded at Trones 140 m asl 106 km from the river mouth. The species has been found only at one location further north, in the Vefsna watershed. The upper catchment is situated within Børgefjell National Park established in 1963. Two major (Bjøra, 557 km2; Sanddøla, 1580 km2) and three smaller tributaries (Lindseta, 224 km2; Rekarvasselva, 18 km2; Nesa, 273 km2) have been protected through the Norwegian Protection Plan for River Systems.

15.13. VEFSNA RIVER 15.13.1. Physiography, Climate and Land Use The Vefsna River basin is in the northern reach of Boreal Uplands. The river mouth is at the town Mosjøen, at the innermost part of Vefsnfjorden (66 N; 13 E). The main river originates inside Børgefjell National Park at 1700 m asl and at the Swedish boarder at 1300 m asl. One tributary (Skarmodalselva) originates about 20 km inside Sweden. Several small glaciers lie within the catchment. The name of the main river is Vefsna, but upstream of the confluence with the tributary Unkra, 88 km from the sea, the name is Susna. Two large tributaries, both flowing north, merge with Vefsna at 42 km (Svenningdalselva) and 60 km (Store Fiplingdalselva) from the sea. Vefsna is 161 km long and 7th order in size. Starting at the Swedish boarder, the Susna flows west and then turns north to the village Hattfjelldal, 78 km from the sea. At Hattfjelldal, the Vefsna turns sharply west for 36 km, then turns sharply north again at Trofors. At Trofors, the Vefsna flows into the Svenningdalen valley and merges with Svenningdalselva, its largest tributary in the catchment. From Trofors, the Vefsna flows north for 42 km to the sea. The river is rather steep, with an average gradient from Hattfjelldal to the sea of 2.6 m/km. The river flows over several waterfalls on its way to the sea. The most famous is Laksforsen waterfall (16 m) 29 km from the sea, and near the main road between southern and northern Norway. Historically, the Vefsna has been a vital nerve of the district. In the past, the river was used for transport, especially for timber. The river also has been important for harvesting Atlantic salmon. The first British anglers arrived in

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the 1850s, and made their mark on the landscape along the river for the next century. At various times, the Vefsna was among the best salmon rivers in Norway. However, in the mid 1970s the parasite Gyrodactylus salaris invaded the river and killed most of the juvenile salmon. Hence, salmon catches have decreased considerably. The lower catchment is dominated by conifer forest. In the west, the tree line for coniferous forest is at 400 m asl, while birch reach 550 m asl. Pine is found on dry places, and near the river are birch, alder, willow and mixed forest. In the east, the forest reaches higher elevations, with the coniferous tree line about 500 m asl, and birch as high as 800 m asl. The terrain is alpine at elevations >700 m asl in the west and 1000 m asl in the east. The climate can be described as summer mild and winter cold with intermediate precipitation based on records (1961– 1990) at the meteorological station at Mosjøen (10 m asl). Mean annual temperature is 3.6 C and averages 5.7 C and 13.4 C in January and July, respectively. Mean annual precipitation is 1745 mm of which 23% occurs during late summer (July–September). About 15 000 people live within the catchment and about 10 000 of these in the town Mosjøen. Hence, the watershed is generally sparsely populated. The most important industries are agriculture (including forestry), industry, and trading. The largest working place is a melting factory for aluminium in Mosjøen.

15.13.2. Geomorphology, Hydrology and Biogeochemistry The western part of the catchment consists of strongly transformed bedrocks from the Cambro-silurian time period, while the eastern catchment has little transformed bedrock from the same period. Along the Susendalen valley, a wide limestone belt goes from south to north, and strongly influences the water quality with higher values of total hardness, calcium, alkalinity, pH and conductivity in the main river (Koksvik 1976). These values are rather high compared to most other Norwegian rivers. The flow regime of the Vefsna is characterized by high flows in early summer (from mid-May to mid-July) and low flows in winter (Figure 15.2). This is especially pronounced in the eastern part of catchment. In the whole catchment there occasionally occur large floods in autumn and in winter in the west. Little regulation occurs in the basin and mainly consists of water transfer to Røssaga in the northeast and does not influence flows in the main river. At the river mouth, the mean annual discharge is 181 m3/s (specific discharge 43.8 L s 1 km 2). The largest floods observed at Laksfors (3650 km2) were in late November 1961 and late May 1984 with daily discharges of 1678 and 1527 m3/s, respectively. Flow records started in 1908, but are lacking between 1931 and 1952. Water temperature of the Vefsna varies both longitudinally and seasonally. In the Vefsna, water temperature is near

0 C from November until late April, increasing rapidly to 12–16 C in summer. Temperature gradually increases downstream in summer (Figure 15.6). In small tributaries in the upper catchment (Mjølkelva), water temperature is 5 degree lower than in the main river in summer due to inputs of glacier melt water. This affects the mainstream temperature for at least 6 km downstream of the outlet of Mjølkelva. Due to the long periods of water temperature near 0 C, the river is ice covered most of the winter.

15.13.3. Management and Conservation The Vefsna is the largest river in Norway that is not protected against hydropower development. Except the water transfer of seven small tributaries to a neighbouring watershed in the east, the river is unaffected by physical encroachment. The catchment contains several protected areas. In addition to Børgefjell National Park, five nature reserves have been established (Skjørlægda 75.3 km2, Fisklausvatnet 38.5 km2, Skarmodalen, Simskarmyra 5.0 km2 and Bjortjønnlimyra). Even more valuable is probably the size of the entire catchment combined with its pristine nature and the large elevation gradient from 1700 m asl to the sea. In total, this constitutes a large landscape diversity, both geologically and biologically. The status for protection of Vefsna is currently under a governmental study. Seven native fish species are present in the river of which Atlantic salmon and anadromous brown trout have been most important. The non-native European minnow has established reproducing populations. According to official statistics, the average annual nominal catch of Atlantic salmon and anadromous brown trout was about 4 tons between 1876 and 2003. Mean weight of Atlantic salmon caught in 1990–1999 was 3.8 kg. Originally, the salmon could reach Laksforsen waterfall about 29 km from the sea. But following a comprehensive building of fish ladders since the 1870s, salmon can ascend through a number of waterfalls and obstacles up to 330 m asl. In this way, 126 km of the river became accessible and the salmon population increased considerably. The Vefsna was an important river for Atlantic salmon in Norway. In the middle of 1970s, the parasite G. salaris invaded the river, resulting in a dramatic reduction in the salmon population (Johnsen & Jensen 1988). The parasite is most probably a recent invader of Norwegian rivers, and its distribution is associated with fish stocking from infected salmon hatcheries (Johnsen & Jensen 1991). As a measure against the parasite, the fish ladder at Laksforsen waterfall has been closed since 1992. The intent is to prevent salmon spawning upstream of the waterfall, which is impassable without the fish ladder, and thereby eliminate both salmon and the parasite from the upper stretches of the river. Finally, stretches downstream of the waterfall will be treated with rotenone or other chemicals to kill the parasite, as has been done in several other rivers (Johnsen et al. 1999).

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In addition to Atlantic salmon, the lower river holds a large population of anadromous brown trout. Today, they can migrate only up to Laksforsen waterfall. Stationary populations of brown trout are present in all lakes and running waters in the catchment. Arctic char are present in one lake (lake Unkervatn; 321 m asl) near the boarder of Sweden. Grayling were originally reported from the upper catchment near the Swedish boarder (Huitfeldt-Kaas 1918). They have not been observed in the upper river for at least 50 years, and today are probably distributed only in the lower river. In the upper reaches, some tributaries originally flowing east to the Ancylus Sea (9000–7500 years BC) have been redirected and now flow to the Atlantic Ocean. A connection between the river A ngermannelv in Sweden and the Vefsna through the flat valley of Harrvassdalen permitted the spreading of grayling into the Vefsna (Øksendal 1992). This grayling population has since been isolated and may be why the parasite fauna of the Vefsna grayling population is considerably poorer than in more eastern populations (Ieshko et al. 2001). The European minnow was introduced to several lakes in the tributary Svenningdalselva in the 1960s, probably by anglers who used them as live bait for brown trout (Hesthagen & Sandlund 1997). The minnow has spread downstream and is now present in the lower river. Two amphibians are present in the catchment, the common frog (Rana temporaria) and smooth newt (Triturus vulgaris). The smooth newt has been found in three small lakes in the lower Vefsna and is the most northerly observation of this species in the world and the only known locality for smooth newt in northern Norway (Dolmen 1983). The smooth newt is a Red List species in Boreal Uplands (Near threatened, Kalas et al. 2006), and since the locality in the Vefsna is the northern distribution limit for this species, it is of special concern. The Børgefjell National Park is the most important habitat for polar fox (Alopex lagopus) in Norway, and is the most threatened mammal in the country.

15.14. CONCLUSIONS AND PERSPECTIVES Rivers of the Boreal Uplands vary greatly in size and hydrological regime. The most typical feature of all rivers is their importance in valleys as landscape elements and as key economic centres. The small coastal catchments may experience the same human perturbations as the large continental catchments. However, due to their size, the effects of perturbations on, for example, biodiversity may be more pronounced than in the large catchments. To reduce perturbations and maintain catchments for coming generations, 285 landscape elements representing parts of or entire catchments are protected through a special Protection Plan for rivers. The purpose of the Protection Plan is to protect the dynamics and diversity of catchments within an elevation aspect from fjords to mountains. The protection is first related to hydropower development, but the different elements

PART | I Rivers of Europe

of special interest and the reason for their protection will also be considered in terms of other perturbations. The catchments in southern part of the Boreal Uplands have been seriously affected by long-range pollution. Acid precipitation and the acidification of lakes and rivers have resulted in eradication of 9600 populations of six common fish species in Norwegian lakes (Hesthagen et al. 1999) and the Atlantic salmon population in 25 rivers (Hesthagen & Hansen 1991). Liming has been introduced as an effective mitigating measure and, at present, some 3000 water bodies are limed to improve water quality for fish. The reduction in sulphur deposition since 1980 has helped reduce the need of liming in less affected areas. Atlantic salmon has been central to culture and settlement in the Boreal Uplands, and to protect areas for the wild salmon 52 national salmon watersheds and 28 national salmon fjords were established in 2007. At present, two major challenges exist. A major interest in building small hydropower schemes (installed effect <10 MW) has taken place in the last few years. These are built on tributaries to larger rivers in areas where the topography is steep, that is in the south, west and north Boreal Uplands. Thus, the use of rivers for hydropower has changed from large projects (>40 MW) appearing up to the 1990s to a voluminous activity in building small schemes since then. The second challenge is related to floods and the use of land near river corridors. Major floods in later years have revealed a situation where human activity has taken place in areas that should have been left for the river. Problems arise in areas where the river corridor is a major part of the area available for human activity. In a changing climate with more precipitation and frequent floods, the ongoing mapping of flood risk areas demonstrate that substantial flood protection work is needed to keep communities along river corridors safe. Long-term data series are often requested by scientists and authorities, but such data exist for few areas. Hydrology and catch statistics of anadromous salmonids are outstanding examples of long-term data sets (>100 years). Unfortunately, long-term data sets are mostly equivalent to 10–20 years and the willingness to maintain them seems to have a negative trend, even though most parties recognize their importance. Catchments of the Boreal Uplands are managed according to several governmental acts. Several of these acts have been passed in later years. Thus, the trend of increased understanding of rivers as an important agent in society is settled in laws, and thereby gives us the possibility to have a wider perspective of the use of rivers and their corridors.

REFERENCES Berg, O.K. 1985. The formation of non-anadromous populations of Atlantic salmon, Salmo salar L., in Europe. Journal of Fish Biology 27: 805–815. Berge, D. (ed). 2002. Environmetal Surveys of Øyeren 1994–2000. Main report, Akershus Fylkeskommune, 60 pp. (In Norwegian). Berge, D., Berge, J.A., Barton, D., Gaut, A., Tjomsland, T., Rygg, B., Turtumøygard, S., Øygarden, L., Kraft, P. and Dahl, E. 2004.

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Characterization of the Numedalslagen Watercourse and Neighbouring Coastal Areas. Norwegian Institute for Water Research. Report 4784, 140 pp. (In Norwegian). Bergstøl, T. 1964. The History of Numedalslagen. Frithjof Salvesens Trykkeri, Mandal, 344 pp. (In Norwegian). Birks, H.J. 1990. Changes in vegetation and climate during the Holocene of Europe. In: de Boer, M.M., De Groot, R.S. (eds). Landscape-ecological Impact of Climate Change, IOS Press, Amsterdam, pp. 133–157. Brooks, R.J., Nielsen, P.S., and Saltveit, S.J. 1989. Effect of stream regulation on population parameters of Atlantic salmon (Salmo salar L.) in the River Lærdalselva, Western Norway. Regulated Rivers 4: 347–354. Dahl, E. 1998. The Phytogeography of Northern Europe (British Isles, Fennoscandia and Adjacent Areas). Cambridge University Press, Cambridge, UK, 297 pp. Dahl, K. 1926. Untersuchungen im Tunh€ovd €uber die Nahrungsverh€altnisse des Fischbestandes vor und nach der Anstauung. Archiv f€ ur Hydrobiologie 18: 85–98. Dolmen, D. 1983. A Survey of the Norwegian Newts (Tritutus, Amphibia); Their Distribution and Habitats. Meddelelse fra norsk viltforskning 3, 72 pp. (In Norwegian). Dolmen, D., and Kleiven, E. 1997. The mussel Margaritifera margaritifera in Norway 2. – Vitenskapsmuseet, Norwegian University of Science and Technology. Zoologisk Notat 228, (In Norwegian). Eken, M., and Borgstrøm, R. 1994. First report of Gobio gobio from Norway. Fauna (Oslo) 47: 120–123. Gabrielsen, S.E., Barlaup, B.T., Skoglund, H., Gladsø, J.A., Mo, T.A. & Sættem, L.M. 2004. Assessment of the fish population in the river Lærdalselva autumn 2003. Densities of juvenile Atlantic salmon and brown trout during 1991–2003. Freshwater and Inland Fisheries Laboratory, University of Bergen. Report 128, 34 pp. (In Norwegian). Gladsø, J.A., and Raddum, G.G. 2000. Rotenone Treatment and Effects on the Zoobenthos in the River Lærdalselva. Freshwater and Inland Fisheries Laboratory, University of Bergen. Report no. 113, 74 pp. (In Norwegian). Gottschalk, L., Jensen, J.L., Lundquist, D., Solantie, R., and Tollan, A. 1979. Hydrological regions in the Nordic countries. Nordic Hydrology 10: 273–286. Grønlund, A. 1999. Natural resources and land use in Glomma watershed. Hydra Report 3, 22 pp. Halvorsen, G., Dervo, B.K., and Papinska, K. 2004. Zooplankton in Lake Atnsjøen 1985–1997. Hydrobiologia 521: 149–175. Hansen, L.P. 1986. The data on salmon catches available for analysis in Norway. In: Jenkins, D., and Shearer, W.M. (eds.). The Status of the Atlantic Salmon in Scotland, ITE Symposium 15, Institute of Terrestrial Ecology, pp. 79–83. Hansen, L.P., Fiske, P., Holm, M., Jensen, A.J., and Sægrov, H. 2005. Status of Atlantic salmon in Norway 2004. Directorate for Nature Management. Report 4, 42 pp. (In Norwegian). Heggberget, T.G. 1988. Timing of spawning in Norwegian Atlantic salmon (Salmo salar). Canadian Journal of Fisheries and Aquatic Sciences 45: 845–949. Heggenes, J., and Saltveit, S.J. 2002. Effect of aquatic mosses on the juvenile fish density and habitat use in the regulated River Suldalslagen. River Research and Application 18: 249–264. Hesthagen, T., and Hansen, L.P. 1991. Estimates of the annual loss of Atlantic salmon, Salmo salar L., in Norway due to acidification. Aquaculture and Fisheries Management 22: 85–91. Hesthagen, T., and Sandlund, O.T. 1997. Changes in the Distribution of European Minnow in Norway: Reasons and Effects. Norwegian Institute for Nature Research, Fagrapport 13. 16 pp. (In Norwegian with English summary).

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Hesthagen, T., Sevaldrud, I.H., and Berger, H.M. 1999. Assessment of damage to fish populations in Norwegian lakes due to acidification. Ambio 28: 112–117. Holtedahl, O. 1960. Geology of Norway. Norges geologiske undersøkelse 208: 1–540. Huitfeldt-Kaas, H. 1918. The distribution and immigration of freshwater fish species in Norway. Centraltrykkeriet, Kristiania (In Norwegian). Husø, G.M., and Thomsen, C. 2006. The pollution in lake Mjøsa – action plan. Vann 41108–117, (In Norwegian). Hvidsten, N.A., Johnsen, B.O., Jensen, A.J., Fiske, P., Ugedal, O., Thorstad, E., Jensas, J.G., Bakke, Ø., and Forseth, T. 2004. Orkla – A National Reference Watercourse for Assessment of Atlantic Salmon. Norwgian Institute for Nature Research. Fagrapport 79. 94 pp. (In Norwegian with summary in English). Ieshko, E.P., Johnsen, B.O., Shulman, B.S., Jensen, A.J., and Schurov, I.L. 2001. The parasite fauna of an isolated population of grayling, Thymallus thymallus (L.) in the River Vefsna, northern Norway. Bulletin of the Scandinavian Society for Parasitology 11: 37–41. Jensen, A.J. 1983. The Plan of Developing the Stryn Watercourse for Hydropower Production: effects on fish. Directorate for Nature Management, Reguleringsundersøkelsene. Report 15. 64 pp. (In Norwegian). Jensen, A.J., Grande, M., Korsen, I., and Hvidsten, N.A. 1998. Reduced heavy metal pollution in the Orkla River, Norway: effects on fish populations. Verhandlungen Internationale Vereinungen f€ur theoretische und angewandte. Limnologie 26: 1235–1242. Johnsen, B.O., and Jensen, A.J. 1988. Introduction and establishment of Gyrodactylus salaris Malmberg, 1957, on Atlantic salmon, Salmo salar L., fry and parr in the River Vefsna, northern Norway. Journal of Fish Diseases 11: 35–45. Johnsen, B.O., and Jensen, A.J. 1991. The Gyrodactylus story in Norway. Aquaculture 98: 289–302. Johnsen, B.O., Jensen, A.J., and Møkkelgjerd, P.I. 1999. Gyrodactylus salaris and Atlantic Salmon in Norway, Status in 1999. Norwegian Institute for Nature Research, Oppdragsmelding 617. 129 pp. (In Norwegian with English summary). Jonsson, B., Andersen, J-E., Østdahl, T., Bekkby, T., Christie, H., Gaut, A., Størset, L., Magnussen, K., and Aure, J. 2004. Characterization of the Orkla River System. Norwegian Institute for Nature Research, Statkraft Grøner and Eurospatial. Report. 70 pp. Kalas, J.A. Viken, A ., and Bakken, T. (eds). 2006. 206 Norwegian Red List, Artsdatabanken, Norway, pp. 461. Kjemperud, A. 1981. A shoreline displacement investigation from Frosta in Trondheimsfjorden, Nord-Trøndelag, Norway. Norsk geografisk Tidsskrift 611–15, (In Norwegian). Koksvik, J.I. 1976. Hydrography and Invertebrates in the Vefsna Watercourse 1974. Det Kgl. Norske Videnskabers Selskab, Museet. Rapport Zoologisk Serie 4. 96 pp. (In Norwegian). L’Abee-Lund, J.H., Aass, P., and Sægrov, H. 2002. Long-term variation in piscivory in a brown trout population: effect of changes in available prey organisms. Ecology of Freshwater Fish 11: 260–269. Lillehammer, A., and Brittain, J.E. 1987. Longitudinal zonation of the benthic invertebrate fauna in the river Glomma, Eastern Norway. Fauna norvegica Serie A 8: 1–10. Mjelde, M. 2004. The status of Juncus bulbosus in lake Øvre and Nedre Lundetjenn. Norwegian Institute for Water Research. Report 4881, 17 pp. (In Norwegian). Øksendal, K.M. 1992. The Grayling Population in the River Vefsna. A rbok for Norsk Skogbruksmuseum 13: 130–142 (In Norwegian). Østrem, G., Haakensen, N., and Olsen, H.C. 2005. Sediment transport, delta growth and sedimentation in lake Nigardsvatn, Norway. Geografiska Annaler 87: 243–258.

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Petersen, R.C., Gıslason, G.M., and Vought, L.B.-M. 1995. Rivers of the Nordic countries. In: Cushing, C.E., Cummins, K.W., Minshall, G.W. (eds). River and Stream Ecosystems, Elsevier, Amsterdam, pp. 295–341. Ramberg, I.B., Bryhni, I., Nøttvedt, A. & Rangnes, K. 2008. The making of a land - Geology of Norway. Geological Society of Norway, Trondheim, pp. 624. Sæther, O.A. 1990. A review of the genus Limnophyes Eaton from the Holarctic and Afrotropical regions (Diptera, Chironomidae, Orthocladiinae). Entomologica Scandinavica Suppl. 35, pp. 1–139. Sættem, L.M. 1995. Spawning stock of Atlantic salmon and anadromous brown trout in 10 rivers in Sogn and Fjordane, Norway, during 1960– 1994. Directorate for nature management. Utredning 7108, (In Norwegian). Saltveit, S.J. 1993. Abundance of juvenile Atlantic salmon and brown trout in relation to stocking and natural reproduction in the River Lærdalselva, Western Norway. North American Journal of Fisheries Management 13: 277–283. Saltveit, S.J. 1998. The effects of stocking Atlantic salmon, Salmo salar, in Norwegian rivers. In: Cowx, I.G. (ed). Stocking and Introduction of Fish, Fishing News Books, Blackwell Scientific Publications, Oxford, pp. 22–34. Saltveit, S.J. 2006. The effects of stocking Atlantic salmon, Salmo salar, in a Norwegian river. Fisheries Management and Ecology 13: 197–205. Saltveit, S.J., and Bremnes, T. 2004. Effects on Zoobenthos and Fish of Different Flow Regimes in Suldalslagen. Sluttrapport. Statkraft, Sul-

PART | I Rivers of Europe

dalslagen-Miljørapport. Report 42, 137 pp (In Norwegian with summary in English). Sandlund, O.T., and Aagaard, K. (eds). 2004. The Atna River: Studies in an alpine-boreal watershed, Kluwer Academic Publishers, pp. 207. Schnell, Ø.A., and Sæther, O.A. 1988. Vivacricotopus, a new species of Orthocladiinae from Norway (Diptera, Chironomidae). Spixiana Suppl. 14, pp. 49–55. Simonsen, L. 2005. The Mussel Margaritifera margaritifera in the Rivers Numedalslagen, Daleelva and Herlandselva. Den Grønne Dalen. Report 1–16 (In Norwegian). Sørensen, R. 1982. Preboreal-Boreal Glacier Smelting in South-East Nor way. Department of Geology, Agricultural University, A s. Report 17: 1–68 (In Norwegian). Traen, E., Bjørvik, T., Sjulstad, S., and Grønseth, J. 2001. The Life Along the River Numedalslagen. Villmarskfoto/Bokprosjekt Lagen, Hof. 317 pp (In Norwegian). Vik, R. (ed.) 1978. The lake Øvre Heimdalsvatn – a subalpine freshwater ecosystem. Holarctic Ecology 1: 81–320.

RELEVANT WEBSITES www.seNorge.no www.environment.no

Chapter 16

Baltic and Eastern Continental Rivers Henn Timm

Małgorzata Łapi nska

Maciej Zalewski

Estonian University of Life Sciences, Institute of Agricultural and Environmental Sciences, Centre for Limnology, 61117 Rannu, Tartumaa, Estonia

Department of Applied Ecology, University of Ł od z, 12/16 Banacha Str., 90-237 Ł od z, Poland

Department of Applied Ecology, University of Ł od z, 12/16 Banacha Str., 90-237 Ł od z, Poland International Institute Polish Academy of Sciences – European Regional Centre for Ecohydrology under the auspices of UNESCO, 3 Tylna Str., 90-364 Ł od z, Poland

Vaida Olsauskyte_

Ricardas Skorupskas

Agrita Briede

European Commission, Joint Research Centre, Institute for Environment and Sustainability; Via E. Fermi 2749 21027 Ispra (VA), Italy

Vilnius University, M.K. Ciurlionio g. 21, Vilnius 03101, Lithuania

Institute of Biology, University of Latvia, Miera Str. 3, 2169, Latvia

Ivars Druvietis

Gertr ¸ ude Gavrilova

Elga Parele

Institute of Biology, University of Latvia, Miera Str. 3, 2169, Latvia

Institute of Biology, University of Latvia, Miera Str. 3, 2169, Latvia

Institute of Biology, University of Latvia, Miera Str. 3, 2169, Latvia

Gunta Spri¸nge

Ritma Gaumiga

Marina M. Mel’nik

Institute of Biology, University of Latvia, Miera Str. 3, 2169, Latvia

Latvian Fish Resources Agency, Daugavgrivas 8, Riga, 1048

Pskov Department of GosNIORH, Gorkij Street 13, Pskov, Russian Federation

¸

Jurij V. Aleksandrov Pskov Department of GosNIORH, Gorkij Street 13, Pskov, Russian Federation

16.1. 16.2.

Introduction Vistula River 16.2.1. Human History 16.2.2. Physiography and Climate 16.2.3. The Little Vistula 16.2.4. The Upper Vistula 16.2.5. The Middle Vistula 16.2.6. The Lower Vistula 16.2.7. The Narew River 16.2.8. The Bug River 16.2.9. The Pilica River 16.2.10. Land Use 16.2.11. Navigation 16.3. Biodiversity 16.3.1. Cyanobacteria and Algae 16.3.2. Zooplankton 16.3.3. Macrophytes 16.3.4. Riparian Vegetation 16.3.5. Macroinvertebrates Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

16.3.6. Fish 16.3.7. Amphibians and Reptiles 16.3.8. Birds 16.3.9. Mammals 16.3.10. Nature Protection 16.3.11. Human Impacts and Special Features 16.4. Nemunas River 16.4.1. Human History 16.4.2. Physiography and Climate 16.4.3. Land Use 16.4.4. River Geomorphology 16.4.5. Climatic Conditions 16.4.6. Hydrology 16.4.7. Temperature Regime and Hydrochemistry 16.4.8. Major Tributaries 16.4.9. Biodiversity 16.4.10. Human Impacts and Special Features 16.4.11. Water Quality 16.4.12. Protected Areas 607

608

16.5.

16.6.

PART | I Rivers of Europe

Western Dvina River 16.5.1. Introduction 16.5.2. Historical Perspective 16.5.3. Biogeographic Setting 16.5.4. Physiography and Climate 16.5.5. Landscape and Land Use 16.5.6. Hydrology and Temperature 16.5.7. Biogeochemistry 16.5.8. Aquatic and Riparian Biodiversity 16.5.9. Human Impacts and Conservation Narva River 16.6.1. Historical Perspective 16.6.2. Physiography and Climate 16.6.3. Landscape and Land Use 16.6.4. Major Tributaries and Lakes 16.6.5. Biodiversity 16.6.6. Human Impacts and Special Features Acknowledgements References

16.1. INTRODUCTION In this chapter, we focus on four major rivers that flow into the eastern Baltic Sea (Figure 16.1, Table 16.1). From west to east, these are the Vistula (catchment area: 193 000 km2, length: 1068 km), Nemunas (99 000 km2, 937 km), Western Dvina (84 000 km2, 1005 km), and Narva (56 000 km2, ca 650 km). Other larger rivers in this region are the Pregolja (15 500 km2, 187 km), Venta (11 800 km2, 346 km), Lielupe (17 600 km2, 310 km), Gauja (8900 km2, 452 km), P€arnu (6900 km2, 144 km) and Luga (14 000 km2, 353 km). All these rivers are meandering, lowland rivers fringed by vast floodplains. They drain the eastern continental plains and Baltic area. This area includes eastern Poland, Lithuania, Latvia, Estonia, western and central Belarus; the Kaliningrad and Pskov regions as well as the western Leningrad region in Russia. The area belongs to the Central European mixed forest and North Atlantic moist mixed forest biomes. It is bordered by the Carpathian montane coniferous forests in the southwest and Scandinavian and Russian taiga in the east. The eastern Continental and Baltic catchments are under marine and continental influence with an average annual air temperature of 5–6 C in the north and 7–9 C in the south. Average annual precipitation is 450–900 mm in the lower and middle Vistula (up to 1500 mm in the southern mountains), 520–800 mm in the Nemunas, 600–800 mm in the Western Dvina and 560–640 mm in the Narva catchments. Precipitation exhibits large interannual fluctuations. Snowmelt contributes 1/6 (Vistula), 1/3 (Narva), 2/5 (Nemunas), and 1/2 (Western Dvina) to the total annual discharge. Rainfall contributes 1/6 (Western Dvina), 1/4 (Nemunas) and 1/3 (Narva) to total flow, while the remaining contribution is by groundwater.

All rivers are regulated to some extent, modifying flow regimes and suppressing the migration of fishes. The Upper Vistula has been converted into a chain of dams and the Włocławek reservoir intersects the lower river. In the middle Nemunas, the Kaunas hydroelectric power station was built. Three major hydropower stations occur along the Western Dvina and a large hydroelectrical power plant is near the mouth of the Narva River.

16.2. VISTULA RIVER The Vistula (Wisła in Polish) (Photo 16.1) starts at Barania Gora (Beskid Mountains) and flows for 1047.5 km northwards where it discharges near Gdansk into the southern Baltic Sea. It drains an area of 192 980 km2. Around 87% are in Poland (54% of the country) and the remaining part in Belarus, Ukraine and Slowakia. The Bug, Narew, San and Dunajec are large transboundary tributaries to the Vistula. The Vistula has a 1858 km2 delta (Czarnecka 1983; Stachy 1986; Grzesiak & Domanska 2006). Hydrogeomorphologically, the basin is divided into the Little, Upper, Middle, and Lower Vistula (MS, 2005). Geographically, the basin belongs to the Eastern and Central Plains with a small proportion in the Carpathians. The Vistula is a lowland river with 50% of its basin at an altitude of 100–200 m asl and only 7% at 400–1000 m. Overall, its average channel slope is 1 m/km. Mean annual discharge (1951–1995) of the river is 1060 m3/s with a large interannual variation (annual mean: 409–3710 m3/s) (Fal et al. 2000).

16.2.1. Human History In the Vistula basin, human history dates back to the early Stone Age. The river has been an important trade route in central Europe, in particular during Roman times. Navigation began already in the 10th century. The 16–17th century was called the ‘Golden Century’ for the Vistula. Timber, grain, salt, building material, and more recently coal, were major trading goods. The first hydraulic structures and flood protection measures were established between the 15th and 18th centuries (Styczynski 1973; Piskozub 1982). The Partitions of the Polish-Lithuanian Commonwealth (in 1772, 1793, and 1795) were performed by the empires of Prussia, Russia and Austria. During those times, the Vistula became a main transport artery in Europe. New waterways such as the Bydgoski, Augustowski and Dnieprza nskoBu_zanski (i.e. King Canal) canals were constructed for specific political interests. The King Canal was built after the first partition to avoid Prussian duty on cargo for the free city of Gdansk. It directed the Polish transport to the Black Sea via the Dnieper and Pripyat’ Rivers. The Baltic Sea–Vistula– Dnieper–Black Sea water route was one of the most ancient trade-routes, the so-called ‘Amber Road’, on which goods were transported between northern Europe, Greece, Asia and

609

Chapter | 16 Baltic and Eastern Continental Rivers

FIGURE 16.1 Digital elevation model (upper panel) and drainage network (lower panel) of Baltic and Eastern Continental Rivers.

Egypt. Later, Prussians constructed the Bydgoski Canal to direct lower river transport via the Warta and Oder Rivers to Szczecin on the Oder estuary and then to the Baltic Sea, thereby avoiding duty control in the city of Gda nsk (Piskozub 1982; Encyklopedia PWN 1999). The Austrian Empire expanded its control to the upper Vistula up to the San confluence (1772) and near Warsaw

(1795). Prussia occupied the lower Vistula up to the city of Torun during the first, to the city of Płock during the second (1793), and to Warsaw during the third partition. The eastern tributaries (the Bug and Narew Rivers) were included in Russian empire. While the Prussians regulated the lower Vistula and the Austrians started to engineer the upper Vistula, the Russians did not engineer rivers under their influence.

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PART | I Rivers of Europe

TABLE 16.1 General characterization of the Baltic and Eastern Continental Rivers Luga

Narva

Western Dvina

Nemunas

Vistula

Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25%) ecological regions

69 14 373 n.d. 63.2 4.5 2 59; 60

86 56 113 12.3 62.0 4.8 2 59

160 83 746 20.4 64.1 5.1 1 59

140 98 757 25.0 63.1 6.4 2 22; 59

209 192 980 33.4 60.9 7.6 4 22

Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparce vegetation Wetland Freshwater bodies

0.5 7.2 9.2 69.1 0 0.0 12.1 1.9

0.6 18.7 8.2 49.3 2.9 0.0 12.3 8.0

0.7 24.4 14.6 44.7 2.3 0.0 10.7 2.6

1.2 46.1 7.6 32.6 1.9 0.0 8.6 1.5

2.9 52.4 11.0 28.3 0.8 0.1 3.3 1.2

Protected area (% of catchment)

7.9

10.9

8.0

5.2

2.6

Water stress (1–3) 1995 2070

1.0 1.8

1.0 1.0

1.0 1.1

1.0 1.1

1.0 3.0

Fragmentation (1–3) Number of large dams (>15 m) Native fish species Non-native fish species Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person)

2 n.d. n.d. n.d. 0 24 2083

2 0 41 3 2 18 3041

3 3 43 2 2 32 2598

3 1 48 6 4 52 2680

2 3 55 19 21 114 3789

For data sources and detailed explanation see Chapter 1. n.d.: No data.

PHOTO 16.1 Vistula River (Photo: Roman Kujawa).

Chapter | 16 Baltic and Eastern Continental Rivers

When Napoleon Bonaparte restored the Polish state as the Duchy of Warsaw (1807), the middle and lower Vistula basin, except the Pomorze region, was moved under Polish control. In the mouth of the Vistula, Gda nsk again received free city status that was lost to the Prussians during the second partition. At the Congress of Vienna (1815), the autonomy of the Polish kingdom was re-established. Between 1815 and 1830, the development of the Vistula (e.g. as a transport route) was again blocked by Prussian duty in Gda nsk. This led to the construction of Augustowski Canal that connects the Vistula via the Czarna Ha ncza River with the Nemunas River (Piskozub 1982). In 1918, after WWI, the entire Vistula came again under Polish control and major navigation measures were planned between Przemsza and Gda nsk. Before WWII, several major reservoirs were constructed in the headwaters, mainly for flood protection (e.g. Ro_zn ow reservoir on Dunajec). The main channel was regulated and embanked (mainly in the upper and lower river). After WWII, the Upper Vistula Cascade (consisting of six dams) and a large dam (Włocławek) (one of eight planned in the Lower Vistula Cascade) were built. The middle Vistula remained free-flowing, although plans for 32– 36 dams were made (till the year 2000) (Piskozub 1982). Today, 13 large reservoirs (>15 m, >50 million m3) are found in the whole basin (Grzesiak & Doma nska 2006).

16.2.2. Physiography and Climate The Vistula starts in the Beskid Mountains (Silesian Beskid) at Barania G ora (1106 m asl). The Black (Czarna Wisełka) and White (Biała Wisełka) Vistula form the 106 km long Little Vistula (Mała Wisła). The ‘proper’ Vistula starts at the confluence with the Przemsza River and is a lowland river that crosses the Polish plains and discharges into Vistula lagoon at Gda nsk Bay. The Little Vistula has a mountainous near-natural character, while the upper Vistula (to Dunajec River) is mostly regulated and to San River outflow regulated is 54%. The middle Vistula (Dolina Srodkowej Wisły) and lower river down to the Włocławek reservoir have retained a near-natural character (channel width: 600–1200 m, valley width: up to 10 km). The section downstream from Silno (Rkm 720) to the Baltic Sea is regulated (Gacka-Grzesikiewicz 1995). The Carpathian and Beskidy Mountains consist mainly of Mesozoic rocks (65–230 million years BP). At the foothills of the Carpathian Mountains (upper and lower Silesia), Mesozoic and Tertiary sediments contain abundant coal, salt and sulphur deposits (http://www.pgi.gov.pl). During the late Quaternary, ice sheets covered 20–90% of the catchment, blocked the main outlet and created several marginal streams. High floods during the Holocene caused intense erosion and deposition, and subsequent shifting and avulsion of river channels. Thousands of lakes and hillocks in the central and northern basin are remnants of retreating glaciers. Deforestation and soil cultivation in the 5th century BC locally increased soil erosion. The present Vistula floodplain has been shaped by large-scale deforestation of the Car-

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pathian Mountains in the 17th century (Starkel 1987, 1990, 1991, 1997, 2001). Between the 6th and 13th century, the river had a relatively narrow channel with well-developed meander beds. During the Medieval period (14–15th century), climate change led to an increase in peak floods. During the Little Ice Age (16–19th century), frequent floods modified the river from a meandering to a braided type. Channel regulation and construction of reservoirs have further modified the river back to a meandering type (Florek 1997; Starkel 2001). In addition, increasing human impacts over the last two centuries have significantly increased soil erosion (Starkel 2001; Starkel et al. 2006; Gregory et al. 2006). From upstream to downstream, the Vistula passes the Carpathian Mountains (Silesian Beskids), the sub-Carpathian basins, the Polish Uplands (Wy_zyna Małopolska and Wy_zyna Lubelska) and the Polish Lowland (Nizina Mazowiecka) (Kondracki 2002). According to the Polish soil classification system (Systematyka gleb Polski 1998), there are 35 soil types and 78 sub-types. Most of the soils have developed from post-glacial rocks and only a small area is covered by massive rock derived soils. The dominating soil types (82% of the territory) are brown soils, acid brown soils, grey brown podsolic soils, rusty soils and podsolic soils. Remaining area is covered mainly by chernozem soils, rendzina soils, black soils and alluvial soils (Białousz 1994; FAO 2003; IEP 2003). All other soil types originate mostly from sedimentary, postglacial, tertiary and cretaceous rocks. The Scandinavian glacier covered the Polish territory three times and shaped the oldest soils in the southern part of the Vistula basin (Mindel glaciations) and the youngest in its northern part (Wurm glaciations) (FAO 2003; IEP 2003). According to a soil map of Poland, derived from the SOVEUR database (FAO/ISRIC 2000) using the FAO Revised Legend (FAO 1988) as a classification system, the soils of Carpathian part of Vistula basin (Figure 16.1) are mainly dystric cambisols and umbric leptosols. In the upper part of Vistula basin, stagnic luvisols and haplic podzols dominate, with some significant patches of haplic chernozems, calcaric cambisols and cambic arenosols. In the middle Vistula basin, besides stagnic luvisols and haplic podzols, the significant area is covered by haplic luvisols and by cambic arenosols. In some patches are also gleyic phaeozems (e.g. near Warsaw). In Narew basin a significant area is covered by terric histosols and in its upper part by eutric podzoluvisols. In the lower Vistula basin, haplic and stagic luvisols, cambic arenosols and eutric cambisols dominate. Along the main Vistula channel and its tributaries, alluvial soils dominate – eutric fluvisols (SIEP 1998; FAO/ISRIC 2000) The average annual temperature ranges from 5–6 C (Little Vistula) to 8–9 C (Upper Vistula) and decreases to 7–8 C further downstream (Leszczycki 1994). The average annual precipitation in Poland is 600 mm but extends up to 1500 mm in the mountains (Little Vistula region). The upper Vistula receives 600–900 mm and the

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middle section 450–500 mm. Further downstream, precipitation increases again (500 mm in the delta). In winter, 50% of the precipitation is snow (Leszczycki 1994). The river exhibits two flow peaks, one in spring (February–April) during snowmelt, and another in summer (June–July) as a consequence of heavy rains in the mountains. Low flows occur in early autumn (September–October). The river freezes for a month in the south and for about 3 months in central and northern Poland.

16.2.3. The Little Vistula The Little Vistula in its upper part (Czarna and Biała Wisełka) is 106 km long mountain river, with catchment area 1748 km2 and mean recorded discharge 20.1 m3/s. Its average valley slope is 22% and a river channel slope more than 5% (Wr obel 1995; Gacka-Grzesikiewicz 1995; Fal et al. 2000). The river valley is 0.5–15 km wide and the channel is up to 90 m wide. Average annual water temperature is 10.2 C (summer average: 16.6 C) (Tuszko 1977). Two reservoirs have been built on the river for water supply and flood control (Wisła-Czarne at Rkm 98.6, and Goczałkowie at Rkm 38 of the navigable Vistula below Przemsza River) (http://www.imgw.pl/internet/otkz/zapory/pl/wisla/). In this area, there are many fish-ponds for intensive farming of Cyprinus carpio. The area is densely inhabited. Small woodlands are mainly broadleaf forests of a dry-ground character. Downstream of Goczałkowice reservoir, Little Vistula has a lowland character with an average valley slope of 0.30% and valley width 4–10 km. The channel is almost completely regulated, having an average width of 400 m and average gradient ca 0.04% (Gacka-Grzesikiewicz 1995).

16.2.4. The Upper Vistula The Upper Vistula from the mouth of the Przemsza River to the mouth of the San River (Rkm 0 to Rkm 280, catchment area 31,847 km2, mean recorded discharge 284 m3/s), flows through the Oswi˛e cim Dale, the Krak ow Gate, and the Sandomierz Dale. Its average valley slope is 0.31%, average valley width from 1 to 20 km. Channel width is from 90 to 170 m and its average gradient is about 0.04% (Gacka-Grzesikiewicz 1995; Fal et al. 2000). The channel is fringed by flood embankments (right bank: 100%, left bank: 70–100%; Gacka-Grzesikiewicz 1995). Average annual water temperature is 10.2 C (Tuszko 1977). About 25% of the catchment is intensively industrialized (Buszewski et al. 2005). The Upper Vistula has six dams (Dwory, Smolice, Ł˛a czany, Kosciuszko, D˛a bie and Przew oz), allowing the use of barges up to 1000 tons. The main items transported are gravel, sand, and soon coal (http://www.rzgw.krakow.pl).

16.2.5. The Middle Vistula The Middle Vistula (from Rkm 280 km to Rkm 550, catchment area 84,540 km2, mean recorded discharge 1060 m3/s)

PART | I Rivers of Europe

extends to the mouth of the Narew River (Gacka-Grzesikiewicz 1995; Fal et al. 2000). The river flows through the Małopolska Vistula Gorge, Mazowsze Lowland, and Warszawa Dale. Average valley slope is 0.27%. The river valley is 1–20 km and the channel 250–350 m wide. Average river gradient is 0 03–0 02%. Embankments fringe the main channel (right bank: 60–85%, left bank: 85%). Average annual water temperature is 10.2 C (summer: 16.6 C, winter: 3.1 C) (Tuszko 1977). About 50% of the catchment area covers agriculture (Buszewski et al. 2005). Up to the city of Płock, the river has a natural braided appearance with numerous sand bars and vegetated islands. The banks and flood terraces are covered by shrubs and willow-poplar forests, meadows, pastures and arable land. Peatland and heathland cover 26% of the Małopolska Vistula Gorge (http://www. mos.gov.pl/natura2000). The Kampinos Forest near Warszawa has high conservation value (Gacka-Grzesikiewicz 1995). The city of Warsaw is the most populated and industrialized area in this reach.

16.2.6. The Lower Vistula The Lower Vistula (from Rkm 550 to delta, catchment area 194376 km2, mean recorded discharge 1060 m3/s) extends from the Narew mouth downstream to the Baltic Sea. It passes Płock, Torun, Fordon, and Grudzi˛a dz Dales, the Kwidzyn Valley and the suławy Delta. Average valley slope is 0.20% decreases to 0.09% in the delta. Lower Vistula river gradient is about 0 02–0 012% to 0 002% in delta (Backiel & Penczak 1989; Gacka-Grzesikiewicz 1995; Fal et al. 2000). The river valley is 3–20 km wide and channel width is 1500 m between Rkm 621 and 675 km and decreases to 260–360 m further downstream. Embankments fringe the channel over most of its length. The distance between the embankments is 1250–1500 m (but only 110 m in the delta) (Gacka-Grzesikiewicz 1995). About 25% of the catchment area has an agricultural and industrial character (Buszewski et al. 2005). Average annual water temperature is 12.4 C (summer: 16.5 C, winter: 2.8 C) (Tuszko 1977). At Rkm 675, Włocławek dam was constructed as a multipurpose dam (hydropower, water supply, flood control, irrigation, water transport, and recreation) that impounds the Vistula up to Rkm 632 (Płock area). Włocławek Reservoir parameters are as follows: construction time – 1970, dam height – 24 m; reservoir: volume – 376 million m3, surface – 70,4 km2, length 60 km. The main hydrochemical characteristics (mean annual concentration) in the Vistula River mouth cross section in 2001 were as follows: water flow: 1315.0 m3/s, water temperature: 11.9 C, Chl a: 25.2 mg/L, dissolved matter: 491.2 mg/ L, suspended matter: 13.8 mg/L, colour: 25.3 mg Pt/L, turbidity: 1.83 mg SiO2/L, pH: 8.08, conductivity: 738.4 mS/cm, dissolved oxygen: 10.7 mg/L, BOD5: 3.7 mg/L, COD-Mn: 8.48 mg/L, COD-Cr: 24.4 mg/L, NH4–N: 0.31 mg/L, NO2– N: 0.019 mg/L, NO3–N: 1.63 mg/L, Kjeldahl N: 1.05 mg/L, total N: 2.7 mg/L, PO4–P: 0.086 mg/L, total P: 0.181 mg/L,

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chlorides: 99.0 mg/L, sulfates: 54.3 mg/L, total hardness: 257.7 mg/L, Ca: 85.7 mg/L, Mg: 11.2 mg/L, Na: 47.6 mg/L, K: 4.76 mg/L, Fe: 0.05 mg/L, Mg: 0.006 mg/L, Zn: 0.015 mg/ L, Cd: 0.00001 mg/L, Cu: 0.0041 mg/L, Pb: 0.0013 mg/L, Hg: 0.0001 mg/L, Cr: 0.0003 mg/L, Ni: 0.0035 mg/L, Al: 0.031 mg/L, phenols: 0.003 mg/L, Coli index: 0.363 (Niemirycz et al. 2004).

16.2.7. The Narew River The Narew (Photo 16.2) (called Naura in former Prussia and Lithuania, and Nara in Belarus) drains western Belarus and northeastern Poland. It has catchment area of 75 175 km2; (72% in Poland) and length of 484 km (36 km in Belarus). It starts at 159 m asl in the northeast Białowie_za Forest (Dzikie Bagno – Wild Marsh) and enters the Vistula near Modlin (67 m asl). Downstream of Zegrzy nski (D˛e be) reservoir, where the Bug River enters, it is called the Narwio-Bug (Encyklopedia PWN 1999). The upper Narew contains one of the largest natural floodplains in Europe. The Narew basin includes some of the most diverse and natural landscapes in Poland (Narew, Biebrza and Białowie_za National Parks). In 1995, Biebrza Park was designated as a wetland site of global importance protected by the Ramsar Convention. The most important area of the Park is covered by Czerwone Bagno (Red Marsh), which is under strict protection. The park is drained by the 155 km long Biebrza River (7057 km2), a main tributary of the Narew. Two large multipurpose reservoirs (Siemian owka and Zegrzy nski) have been built along the Narew. The Siemian owka (constructed in 1991) is a 13.5 km long reservoir (volume: 79.5 mill. m3). The Zegr-

zynski (D˛e be) (built in 1963) is a 40 km long reservoir with volume 0.09 km3 (http://www.imgw.pl/internet/otkz/zapory/ pl/). The main hydrochemical characteristics of the Narew river (3 km upstream from the mouth) for years 2003–2004 are as follows: dissolved oxygen: 9.73 mg/L, BOD5: 2.5 mgO/L, CODMn: 11.22 mg/L, CODCr: 31.64 mg/L, NH4–N: 0.16 mg/L, NO2–N: 0.02 mg/L, NO3–N: 0.55 mg/ L, total N: 2.34 mg/L, phosphates: 0.29 mg/L, total P: 0.15 mg/L, chlorophyll a: 39.34 mg/L (sources: http://www. eea.europa.eu). The main hydrochemical characteristics of the Biebrza River (8.5 km upstream from the mouth) for years 2003–2004 are as follows: dissolved oxygen: 7.56 mg/L, BOD5: 1.89 mgO/L, CODMn: 11.86 mg/L, CODCr: 43.91 mg/L, NH4–N: 0.07 mg/L, NO2–N: 0.02 mg/ L, NO3–N: 0.93 mg/L, total N: 1.96 mg/L, phosphates: 0.18 mg/L, total P: 0.09 mg/L, chlorophyll a: 1.24 mg/L (sources: http://www.eea.europa.eu).

16.2.8. The Bug River The 772 km long Bug River is the longest left-bank tributary of the Narew. The Bug crosses parts of the Ukraine (184.4 km) and forms borders between Ukraine and Poland (185 km), and between Belarus and Poland (178 km). Its catchment area is 39 400 km2 (22% in Ukraine, 29% in Belarus, 49% in Poland). The human population in its catchment area is 2.0 million in the Ukraine, 0.5 million in Belarus, and 1.1 million in Poland. The river starts at 311 m asl in eastern Roztocze in the Lviv region (Ukraine). The average catchment elevation is 183 m asl. It enters into Zegrzynski (D˛e be) reservoir. In the upper section, the basin PHOTO 16.2 Narew River, a tributary to Vistula (Photo: Małgorzata Łapinska).

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is about 70–100 km wide, in the lower section up to 120 km. The Ukrainian section of the river has two big dams (Sosn owka and Dobrotw or). In the Polish section, local groynes, ripraps and lateral embankments occur (Dombrowski et al. 2002). The Bug still has a near-natural style along most of its length. It is characterized by a complex riverbed and contains numerous mid-channel and lateral bars as well as oxbow lakes and semi-natural terraces. Both the channel and flood terraces are of high ecological value. In contrast, the flood terrace of the Vistula is strongly modified due to embankments (Dombrowski et al. 2002). The main hydrochemical characteristics of the river at the city of Wyszk ow (33.8 km upstream from the mouth) are as follows: pH: 7.3–9.1, HCO3: 232 mg/L, SO4: 11–71 mg/L, Cl: 16–40 mg/L, Ca: 61.8–124.3 mg/L, Mg: 5.1–19.9 mg/L, NO3–N: 2.52 mg/L, NO2–N: 0.098 mg/L, total N: 2.47– 5.53 mg/L, PO4–P: 0.03–0.58 mg/L, total P: 0.15–0.61 mg/ L, Fe: 0.01–0.1 mg/L, BOD5: 1.4–18.6 mgO/L, CODMn : 6.4–22.7 mg/L, NH4–N: 0.13–1.18 mg/L, total hardness: 196–390 mg/L, dissolved oxygen: 6.2–15.7 mg/L, conductivity: 740 mS/cm (Bo_zek et al. 1998 cited in Dombrowski et al. 2002).

16.2.9. The Pilica River The 319 km long Pilica in central Poland is the largest leftbank tributary of the Vistula (catchment area 9273 km2). The river starts at 350 m asl in the Krak ow-Czestochowa Uplands, near the village of Wola K˛a cikowa. The Pilica enters the Vistula near the village of Potycz (Rkm 457). The main tributaries are Luci˛a z_ a and Wolborka (left bank), Czarna and Drzewiczka (right bank) (http://www. wikipedia.pl, Encyklopedia PWN 1999). In 1973, the 21 m high Sulej ow reservoir (volume: 77.4 mill. m3) was created at Rkm 138.9. It is a multipurpose reservoir used for hydropower generation, water supply, flood control, irrigation, water transport and recreation (http://www.imgw.pl/internet/otkz/zapory/pl/wisla/index.htm). Its annual phosphorous load, mostly from non-point sources, exceeded 8 g/m2 (Zalewski et al. 2000; Zalewski 2002; Zalewski & WagnerŁotkowska 2004). The main hydrochemical characteristics of the Pilica River 1.6 km upstream from the mouth) for years 2003–2004 are as follows: dissolved oxygen: 11.07 mg/L, BOD5: 2.44 mgO/L, CODMn: 5.83 mg/L, CODCr: 19.76 mg/L, NH4–N: 0.27 mg/L, NO2–N: 0.01 mg/ L, NO3–N: 0.97 mg/L, total N: 2.17 mg/L, phosphates: 0.17 mg/L, total P: 0.10 mg/L, chlorophyll a: 5.20 mg/L (sources: http://www.eea.europa.eu). In Sulej ow reservoir on the Pilica, the most abundant invertebrates are Oligochaeta, Chironomidae, Ceratopogonidae, Bivalvia and Gastropoda. Maximum benthos density and biomas was noted in autumn season 20 000 nska & Skrzypski individuals/m2 and 5500 mg/m2 (Puczy 2007).

PART | I Rivers of Europe

16.2.10. Land Use The Vistula basin is covered by 49% arable land, 27% forests, 16% extensively used meadows and pastures, 2.5% waterbodies, 1.4% orchards and 7.3% urban and other areas (Bielecka & Ciołkosz 2004; Grzesiak & Domanska 2006). Intensive deforestation already started in the 14th century (Białkiewicz & Babinski 1980; Romanowski et al. 2005; Van der Sluis et al. 2007). During the last 150 years, natural coniferous and broadleaf forests have decreased along the main riparian corridor, while the proportion of riparian softwood forests, undefined forests and grasslands have increased. Today, the Vistula corridor contains about 27% semi-natural riparian forests (Olson et al. 2001) The Kampinos Forest near Warsaw is the most important one. A considerable decrease in wet hay-meadows (mown once per year), psammophilous grasslands, and heathlands has occurred, while wet Calthion meadows have increased in the area since 1830. A recent increase in willow-poplar alluvial forests and shrubs is a consequence of natural riparian forest regeneration (Romanowski et al. 2005; Van der Sluis et al. 2007). Construction of Włocławek reservoir (1968–1970) resulted in a strong decrease in seasonally flooded meadows and pastures. On Pleistocene terraces, forests have been converted into arable land and lower swampy areas were converted into meadows. The riverbed was considerably widened and the channel area increased from 110.5 km2 in 1830 to124.9 km2 in1985 (Romanowski et al. 2005; Van der Sluis et al. 2007). The Kampinos Forest, the Niapołomice Forest and other NATURA 2000 sites along the Vistula form the major faunal refugia in Poland, and the river itself serves as an ecological corridor of European importance (Kajak 1992, 1993; http://www.mos.gov.pl/natura2000).

16.2.11. Navigation The Vistula is navigable along almost its entire length (941 km), although major sections of the river do not meet the standards required for modern navigation. From the Baltic Sea to Bydgoszcz (where the Bydgoszcz Canal enters), the river can accommodate medium-size river vessels (CEMT class II). Further upstream, the river is often too shallow for larger barges. However, major future potential for navigation exists, in particular if the east–west connection via the Narew– Bug–Mukhovets–Pripyat’–Dnieper waterways would be reactivated (Piskozub 1982).

16.3. BIODIVERSITY 16.3.1. Cyanobacteria and Algae In the upper Vistula, Hanak-Schmager (1974) identified 374 algae and zooplankton taxa including 41 Cyanophyceae, 22 Flagellata, 3 Pyrrophyta, 6 Heterokontae, 8 Chrysophyceae,

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162 Bacillariophyceae, and 80 Chlorophyceae. In addition, 14 Schizomycetes and Myxomycetes, 7 Ciliata, 1 Suctoria, 20 Rotatoria, 8 Cladocera, and 2 Copepoda were identified. The phytoplankton of the upper Vistula was studied by _ Bucka (2002), and Zurek et al. (2002), and reviewed in depth by Bucka (2004) and Bucka & Wilk-Wozniak (2007). In unpolluted headwaters, diatoms (Fragilaria arcus) and green algae (Stichococcus spp.) dominated. Chrysophytes (Kephyrion spp.) and rhodophytes (Audouinella sp.) were also common. Further downstream, the more tolerant species Melosira varians, Navicula lanceolata and Fragilaria ulna occurred. Severe pollution between Rkm 117.6 and 185.2 km was indicated by the predominance of cyanobacteria. Between Rkm 248.2 and 336.7, where organic pollution decreased again, Chlorococcales associated with cyanobacteria (e.g. Microcystis spp., Anabaena spp., Woronichinia naegeliana) dominated (Bucka 2002, 2004). In Goczałkowice reservoir, algae blooms were caused by Aphanizomenon flos-aquae, Microcystis aeruginosa and _ Anabaena spiroides (Paj˛a k 1986; Zurek & Bucka 2004). In this reservoir, 55 algae taxa including cyanophytes (3 taxa), chlorophytes and desmids (27), diatoms (21), euglenophytes (3) and heterokontophytes (1) were identified (Bucka 2004). Density ranged from 2.5 to 6.5 106 algae/L and biomass from 5.0 to 14.6 mg/L (Dembowska & Napi orkowski 2000). Cyclotella meneghiniana was the most dominant diatom (30% of total algal abundance, 60% of total biomass). Phytoplankton density decreased from Płock (Rkm 633) to sections near the Włocławek dam (Rkm 675). Composition changed from a predominance of diatoms (Rkm 633) to green algae (Rkm 675). Due to a short retention time (4–5 days), Włocławek reservoir maintains a rheolimnic character. Blue-green algal blooms were so far absent due to low nutrient and good oxygen conditions (Dembowska & Napi orkowski 2000). Diatoms formed up to 90% of the phytoplankton community in the middle and lower Vistula, by predominating Stephanodisus hantzschii, C. meneghiniana, and green algae (Dembowska & Napi orkowski 2000). Between 1994 and 2000, 441 taxa were recorded, mainly Bacillariophyceae (192 taxa), Chlorophyta (164), Cyanophyta and Euglenophyta (Dembowska 2002). In the Vistula delta and in the adjacent Baltic Sea, the first bloom of the toxic species Nodularia spumigena and A. flos-aquae was recorded in 1994. These blooms are a consequence of the high pollution level in the Vistula (Niemkiewicz & Wrzołek 1998; Andrulewicz et al. 2004). Blooms of blue-green algae, including potentially toxic species, represent a serious problem in this area (Rybicka 2005). Toxic algal blooms (mainly A. flos-aquae and M. aeruginosa) are common in Sulej ow reservoir (Pilica River) (Zalewski et al. 2000; Tarczy nska et al. 2001; Rakowska & Rakowski 1992; Izydorczyk et al. 2005; Jurczak et al. 2005). Between 1979 and 1980, 543 phytoplankton taxa were identified there (Rakowska & Rakowski 1992; Galicka et al. 1992, 1998; Tarczy nska 1998). The mean water retention time of this shallow eutrophic reservoir is 30 days and

favours algae blooms (Wagner & Zalewski 2000; Tarczy nska et al. 2001; Rakowska et al. 2005). In spring (1999–2001), the phytoplankton community was dominated by diatoms such as Cyclotella sp., Asterionella formosa, Tabellaria flocculosa, Fragilaria crotonensis, F. capucina, and F. ulna (up to 98% of all individuals). Biomass was up to 16 mg/L. Summer diatom blooms were as high as 53 mg/L (in 2000) in the riverine section of the reservoir. In the lacustrine part, cyanobacterial blooms, mainly by M. aeruginosa, M. wesenbergii and A. flos-aquae, varied from 5 (in 2000) to 189 mg/L (2001) (Izydorczyk 2002).

16.3.2. Zooplankton Zooplankton of the Vistula and its main tributaries is dominated by rotifers, copepods and cladocerans. In the lower Vistula, including Włocławek reservoir, a total of 128 zooplankton species (85 Rotatoria, 22 Cladocera, and 21 Copepoda) were reported. Density ranged from 2 to 6917 individuals/L (average 395 individuals/L). The most abundant Rotatoria were Brachionus angularis, Brachionus calyciflorus, and Keratella cochlearis. The Włocławek dam significantly altered the community. In the reservoir, the average zooplankton abundance and biomass were 533 individuals/L and 114 mg/L (dry weight), respectively (Dembowska & Napiorkowski 2000; Napiorkowski 2002). The zooplankton community of Sulejow reservoir was dominated by Daphnia cucullata (biomass up to 41 mg/L). In years with low Daphnia densities, Bosmina coregoni dominated (biomass up to 28 mg/L). Leptodora kindtii can eliminate 11–60% of the Daphnia biomass (Wojtal 2000).

16.3.3. Macrophytes The Vistula riverbed is often colonized by species of the phytosociological class Phragmitetea, characterised by Sagittario-Sparganietum, Typhetum angustifoliae and Glycerietum maximae (Gacka-Grzesikiewicz 1995; Matuszkiewicz 2001; Zaj˛a c & Zaj˛a c 2001). The main channel is inhabited by Potamogeton crispus, Potamogeton pectinatus, P. pusillus, Ceratophyllum demersum, Callitriche verna, Myriophyllum aquatilis, Batrachium circinatus, the protected species Batrachium aquatilis, as well as by the nonnative but abundant species Elodea canadensis. Oxbow lakes have diverse and dense macrophyte beds. Phragmition, Phalaridetum arundinaceae and Sparganio-Glycerietum fluitantis are the most important associations. In addition, Caltha palustris, Iris pseudoacorus, and the non-native Acorus calamus occur there. The most abundant Vistula channel macroflora are terophytes of the phytosociological class Bidentetea tripartiti, the alliance Chenopodion fluviatile and the association Xantio-Chenopodietum. There occur typical species of bare sand bars and vegetated islands, thus representing early ecological successions (Gacka-Grzesikiewicz 1995, http://www.mos.gov.pl/natura2000).

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16.3.4. Riparian Vegetation Riparian zones in the Vistula basin mainly consist of willowpoplar forests (Salicetum albae, Salici-Populetum) and shrubs (Salicetum triandro-viminalis) with Populus alba, P. nigra, Salix alba, S. fragilis, S. triandra, S. viminalis, Alnus glutinosa and Fraxinus excelsior as predominant species. These areas, actually often replaced by meadows, are of high protection priority (91E0-1 type in EU-Council directive 92/ 43/EEC). Large lowland rivers in the Vistula basin are typically fringed by ash–elm forests (Ficario-Ulmetum typicum) with F. excelsior, Ulmus minor and Quercus robur as dominant species. The abundance of A. glutinosa, Ulmus glabra and Ulmus laevis has decreased. Larger complexes remain in the area of the Sandomierz Dale near Warsaw, (Kampinos Forest) and as small refugia in the lower Vistula (Gacka-Grzesikiewicz 1995, http://www.mos.gov.pl/natura2000). Headwater riparian zones include Dentario glanduloseFagetum intermixed by patches of Calamagrostio villisae-Pinetum (Gacka-Grzesikiewicz 1995, http://www.mos.gov.pl/ natura2000). In the lower Vistula, between the cities of Płock and Bydgoszcz, natural patches of riparian vegetation occur. For example, downstream of Włocławek dam, sand islands are colonized by B. tripartiti and Isoeto-Nanojuncetea. Some islands and riparian areas are covered by the association Salicetum triandro-viminalis. Riparian communities may include also Salicetum albo-fragilis and Populetum albae. Patches of floodplain forests are formed from Ficario-Ulmetum minoris, Violo odorotae-Ulmetum minoris and Alno-Ulmion. The near-natural Narew valley includes 13 different habitat types listed in Annex I of the EU-Council Directive 92/ 43/EEC. The Biebrza River valley contains diverse plant communities including mire woods, alder swamps, sedge and reed beds. The largest part is covered by mires and quaking bogs (Caricion lasiocarpae, Caricetum appropinquatae), purple moorgrass meadows and coniferous mire woods. The Bug valley includes many endangered habitat types: inland dunes with Corynephorus and Agrostis grasslands, natural eutrophic lakes with Magnopotamion and Hydrocharition; muddy river banks with Chenopodion rubri and Bidention vegetation, European dry heaths, alluvial meadows, alluvial forests with A. glutinosa and F. excelsior, riparian mixed forests with Q. robur, U. laevis, U. minor, F. excelsior and F. angustifolia (http://www.mos.gov.pl/natura2000). Similarly, natural euthrophic lakes, dry heathlands, and alluvial forests, and riparian mixed forest are important habitats in the Pilica valley.

16.3.5. Macroinvertebrates About 600 macroinvertebrate taxa have been identified in the Vistula River and its reservoirs. Chironomidae (152 taxa), Oligochaeta (64), Trichoptera (57), Ephemeroptera (50), and Mollusca (50) are the most species-rich groups. The

PART | I Rivers of Europe

species composition of many group is not completely known (Kownacki et al. 1994; Kownacki 1999). In addition, pollution and the construction of reservoirs has reduced the number of taxa and changed the species composition. The free-flowing Little Vistula is characterized by high taxonomic diversity of taxa like: Ephemeroptera, Trichoptera, Chironomidae (mainly Orthocladiinae) and Simuliidae (Mikulski 1950; Kownacki 1995). Atmospherically acidified streams of Czarna and Biała Wisełka are dominated by Plecoptera (approximately 50% of abundance), Diptera (20%), Oligochaeta (up to 10%) and Trichoptera (7%) with minor addition of Hydracarina, Coleoptera, Megaloptera, Lepidoptera, Osctracoda and Mollusca (Szcz˛e sny 1995, 1998). Wisła-Czarne reservoir is dominated by Oligochaeta (Limnodrilus hoffmesteri and Tubifex tubifex) and Chironomidae (mainly Procladius spp., Ablabesmyia sp., Prodiamesa olivacea, Dicrotendipes spp., Chironomus spp.) (Krzy_zanek 1991). The upper Vistula near Krakow revealed a typical rhithral community after WWII (Starmach 1948). Dumnicka & Kownacki (1988) recorded a drastic shift toward a dominance of Oligochaeta (63–99% of abundance). Today, Oligochaeta, particularly Limnodrilus hoffmeisteri, form up to 99% of the bottom fauna in the Upper Vistula Cascade. In unregulated reaches, Hirudinea, Gastropoda, Amphipoda, Simuliidae, Chaoboridae, Psychodidae and Coleoptera were also noted (Kownacki 1988). Benthos density for upper Vistula at reference vs. polluted sites was as follows: Oligochaeta 8,250 individuals/m2 vs. 102 434, Ephemeroptera 286 vs. 0, Trichoptera 22 vs. 231 (Fleituch et al. 2002). The middle Vistula zoobenthos included Oligochaeta (13 taxa), Hirudinea (6), Gastropoda (14), Bivalvia (11), Amphipoda (4), Isopoda (2), Ephemeroptera (12), Trichoptera (10), Chironomidae (40), Coleoptera (20), and Hydracarina (1) (Kownacki 1999). The lower Vistula harbours Oligochaeta (12 taxa), Hirudinea (9), Gastropoda (6), Bivalvia (10), Amphipoda (3), Isopoda (3), Ephemeroptera (27), Heteroptera (10), Trichoptera (5), Chironomidae (17), Coleoptera (1), and Hydracarina (23) (Kownacki 1999). As expected, many groups (e.g. water beetles) have almost been completely neglected in benthic studies. _ Włocławek reservoir includes 30 taxa (Zbikowski 2000): Chironomidae (10 taxa, dominated by Chironomus spp. and Procladius spp.); Oligochaeta (11 taxa, mainly L. hoffmeisteri, L. claparedeanus, Potamothrix hamoniensis and T. tubifex) and Mollusca (9 species, mainly Sphaeriidae). In the former Vistula riverbed, mean density exceeded 100 000 individual/m2 and mean biomass was 650 g/m2. In the flooded section, mean density was ca 70 000 individuals/ m2 and mean biomass ca 300 g/m2. Oligochaeta constituted 80% of the total abundance, and molluscs 60% of the total biomass. In Sulejow Reservoir on Pilica River Oligochaeta, Chironomidae, Ceratopogonidae, Bivalvia and Gastropoda were most abundant. Maximum bentos density and

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Chapter | 16 Baltic and Eastern Continental Rivers

biomass was noted in autumn (20 000 individuals/m2 and nska & Skrzypski 2007). 5,500 mg/m2) (Puczy Hypodryas maturna, Lycaena dispar and Lycaena helle that occur in the Biebrza River marshes (http://www.mos. gov.pl/natura2000) are among the invertebrates listed in Annex II of the EU-Council directive 92/43/EEC.

16.3.6. Fish Fifty-five native fish species were reported in the Vistula basin. Most of them have their origin from the Ponto-Caspian region (Backiel 1965, 1983; Backiel & Penczak 1989; Bryli nska 2000; Witkowski et al. 2004). Around 32% of these species are considered endangered (Głowacinski 1997, 2001; DZ. U. Nr 130, poz. 1456. 2001; Witkowski et al. 2004). The Vistula fish fauna has still good status due to its high habitat diversity (Backiel & Penczak 1989; Backiel 1995; Backiel et al. 2000; de Leeuw et al. 2007). The Vistula basin also harbours 19 non-native fishes (Cyprinus carpio, Carassius auratus gibelio, Ctenopharyngodon idella, Mylopharyngodon pireus, Pseudorasbora parva, Hypophthalmichthys molitrix, Hypophthalmichthys nobilis, Ictalurus nebulosus, Umbra krameri, Coregonus peled, Coregonus muksun, Hucho hucho, Salvelinus fontinalis, Oncorhynchus mykiss, Micropterus salmoides, Perccottus glenii, Neogobius fluviatilis, Neogobius gymnotrachelus, Neogobius melanostomus) (Witkowski et al. 2004; http://www.nobanis.org). Hucho hucho, which historically occurred in the Vistula was reintroduced from the Czarna Orawa River, a tributary of the Danube, to the Dunajec River. Fish community of Vistula upstream part consists of Salmo trutta fario and Cottus poecilopus (Czarna Wisełka) with addition of Phoxinus phoxinus (Biała Wisełka) (Kołder 1964; Szcz˛e sny & Kukuła 1998). The most commonly encountered species in Vistula Carpathian tributaries are: Salmo trutta fario, Esox lucius, Rutilus rutilus, Alburnus alburnus, Leuciscus cephalus, Leuciscus leuciscus, Barbus barbus, Chondrostoma nasus, Gobio gobio, Cottus gobio and Perca fluviatilis (Backiel 1995) There were 19 fish species noted in the upper Vistula _ upstream of Krak ow (Rkm 70) (Zurek 1994). Leuciscus cephalus (<25% abundance, >50% biomass), Carassius carassius (<20%, 10%), Alburnus alburnus (<20%, 5%), Rutilus rutilus (<15%, <10%), Esox lucius (2%, <15%), Barbus barbus (<10%, 1%) predominated. Less common (<2% abundance) were: Perca fuviatilis, Alburnoides bipunctatus, Leucaspius delineatus, Rhodeus sericeus amarus and about 1% of Abramis brama, Blicca bjoerkna, Tinca tinca and Gymnocephalus cernuus. Non-native species included Cyprinus carpio and Carassius auratus gibelio (<2% abundance). The middle and lower Vistula have 36 species. Detailed information, based on electrofishing over a 560 km distance, is provided by Wisniewolski et al. (2001). Between Rkm 332 and 398.5, 21 species were recorded. L. cephalus (40% of biomass), Rutilus rutilus (13%) and A. alburnus (13%) predominated. E. lucius, Leuciscus idus,

Abramis brama and Sander lucioperca were additional important species. Between Rkm 482.8 and 527.2, 25 species occurred. Perca fluviatilis, R. rutilus, E. lucius, A. alburnus, L. leuciscus, A. brama and L. cephalus dominated. However, in commercial catches the bream is a dominant species (20– 80% of catch) (Backiel & Penczak 1989; Wisniewolski 2002). The fish fauna of Włocławek reservoir included 17 species. Tinca tinca (56% of total biomass) and P. fluviatilis (27%) dominated (Wisniewolski et al. 2001). Gobio albipinnatus, Lampetra fluviatilis, A. aspius, Rhodeus sericeus amarus, Misgurnus fossilis, Cobitis taenia, Cottus gobio, Pelecus cultratus and Salmo salar are included in the Annex II of the EU-Council directive 92/43/EEC. P. cultratus is an important fish in the Vistula delta (http://www.mos.gov.pl/ natura2000). The Narew River and its tributaries include 36 native species. R. sericeus amarus, M. fossilis and Eudontomyzon mariae are listed as endangered species (Penczak et al. 1990a,b, 1991a,b, 1992; Marszał & Penczak 2002; Wisniewolski 1995; Wisniewolski et al. 2004a; Sych et al. 1990; Szlakowski et al. 2004, http://www.mos.gov.pl/natura2000). Biebrza tributary was studied in detail by (Witkowski (1984a,b); Kozikowska (1984); Wisniewolski et al. (2004b); Szlakowski et al. 2004; Winter et al. 2008; Winter 2007). The Bug River harbours 46 native species, including the endangered species G. albipinnatus, A. aspius, R. sericeus amarus, M. fossilis, Sabanejewia aurata, C. taenia and C. gobio. Other important species are Abramis sapa, Alburnoides bipunctatus, B. barbus, Chondrostoma nasus and Silurus glanis (Wałecki 1964; Zhukov 1965; Wisniewolski 1995; Danilkiewicz 1997; Dombrowski et al. 2002; http:// www.mos.gov.pl/natura2000). The Pilica River is one of the most important rivers in sense of conservation of the fish fauna in Poland. It has 38 native species including lamprey Lampetra planeri, A. aspius, R. sericeus amarus, M. fossilis, C. taenia and E. mariae. Other important endangered species are A. bipunctatus, C. nasus and S. glanis (Penczak 1968, 1988, 1989; Backiel & Penczak 1989; Penczak et al. 1995; Penczak et al. 1996, http://www.mos.gov.pl/natura2000). The fish biomass was 450 kg/ha in the Vistula and Narew reservoirs, 1380 kg/ha in Włocławek reservoir and 600 kg/ha in the Zegrzynski (D˛e be) and Siemianowka reservoirs (Wisniewolski 2002).

16.3.7. Amphibians and Reptiles The Vistula and its main tributaries include a rich herpetofauna with Triturus cristatus, Bombina bombina and Emys orbicularis as species of high conservation value. Other important amphibians are Sicista betulina, Bufo bufo, B. calamita, B. viridis, Hyla arborea, Pelobates fuscus, Rana arvalis, R. esculenta, Rana lessonae, Rana ridibunda, R. temporaria and Triturus vulgaris. Important

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reptiles include Coronella austriaca, Lacerta agilis, Natrix natrix, Anguis fragilis and Vipera berus (Głowacinski 2001; DZ. U. Nr 130, poz. 1456. 2001; http://www.mos. gov.pl/natura2000).

mals there are Alces alces, C. capreolus, Cervus elaphus, Lepus capensis, M. martes, Meles meles, Mustela erminea, Mustela nivalis, Mustela putorius and Sciurus vulgaris (http://www.mos.gov.pl/natura2000).

16.3.8. Birds

16.3.10. Nature Protection

The Polish avifauna includes 444 species (Komisja Faunistyczna 2005), of which 320 (among them 180 breeding species) are recorded from the Vistula valley. The Vistula valley is important for migrating water and marshland birds from Scandinavia and Siberia. The middle and lower sections are of European importance, in particular the reach between the mouth of the San River and Płock (Gacka-Grzesikiewicz 1995). The most endangered birds along the Vistula are purple heron (Aredea Ardea purpurea), night heron (Nycticorax nycticorax), pintail (Anas acuta), kentish plaver (Charadrius alexandrinus), little gull (Larus minutus), common tern (Sterna hirundo), sandwich tern (S. sandvicensis), whiskered tern (Chelidonias hybridus) and black-headed gull (L. ridibundus) (mainly in the Mazowsze region). Sand bars, islands and willow and poplar forests are the key habitats for these species. All sections contain several species that are included in the Annex I of EU-Council Directive 79/409/EEC. The density of wintering and wading birds in the lower and middle river is 20 000 individuals/100 km (Gacka-Grzesikiewicz 1995). In the Narew valley, 179 bird species were noted. The Narew, Bug and Pilica Rivers comprise endangered species Ciconia nigra, Crex crex, Sterna caspia, S. hirundo and S. albifrons (http://www.mos.gov.pl/natura2000).

The Vistula River is a S–N and W–E oriented ecological corridor of pivotal importance, connecting the Southern Carpathian region with the Baltic Sea and the Eastern European regions via the Bug and Notec Rivers with the Warta–Oder River system (Gacka-Grzesikiewicz 1995). The protected area covers about 25% of the catchment: 6% of upper (10 567 km2), 11 % of the middle (18 896 km2) and 8% of the lower Vistula (13 640 km2) (Buszewski et al. 2005). A total of 13 Ramsar wetland sites have been designated here, covering 125 760 ha (status 27 March 2007, http://www.ramsar.org/). For example, the Ramsar sites include Narew River National Park, Biebrza National Park, Poleski National Park, Dru_zno Lake, Karas Lake and Łuknajno Lake. UNESCO Biosphere Reserves in the Vistula basin include Babia Gora, Białowieski National Park, Łuknajno Lake, Kampinos Forest, West Polesie, Eastern Carpathians and Tatra Mountains (http://www. unesco.org/mab/). The most important NATURA 2000 bird areas in the Vistula valley are the 24 767 ha Upper Vistula Valley, 6419 ha Małopolska Vistula Gorge, 28 061 ha Middle Vistula Valley between D˛e blin and Płock, 58 732 ha Włocławska Vistula Valley, 34 909 ha Lower Vistula Valley between Włocławek and Przegalina and 1014 ha Vistula Delta (MS, 2005, http://www.mos.gov.pl/natura2000). Another important Vistula basin NATURA 2000 site is the Upper Narew Valley with the Biebrza Marshes (one of the largest wetlands in central Europe). In this valley, the largest little affected bogs and fens of central and western Europe occur. The Biebrza River, with numerous meanders and oxbow lakes of different succession stages, still has a natural character. The process of active peat formation takes place in large areas (http://www.mos.gov.pl/natura2000). Numerous meanders and oxbow lakes also occur in the Middle Bug valley (http://www.mos.gov.pl/natura2000). The 260 km long Lower Bug valley is covered by dry and extensively used pastures. Swamps are situated mainly near tributary confluences. The Bug harbours many sand bars and islands with willows and poplars. The 80 km long and 1– 5 km wide, protected Pilica valley is locally covered by xerothemic vegetation and dense forests. The river has many meanders, numerous islands, and central and lateral sandbars. After the construction of Sulejow reservoir in 1973, the average discharge decreased by 25%. According to soil humidity and land use, the grasslands nearby range from xerothermic to marshy habitats.

16.3.9. Mammals In the lower Vistula valley, some mammals of high conservation value occur, such as Barbastella barbastellus, Myotis myotis, Castor fiber, Canis lupus and Lutra lutra. Common mammals include Eptesicus serotinus, Myotis daubentonii, Myotis nattereri, Nyctalus noctula, Pipistrellus nathusii, P. pipistrellus, Plecotus auritus and Plecotus austriacus (http:// www.mos.gov.pl/natura2000). In the Vistula delta, C. fiber is common. Important typical mammals in the Małopolska Vistula Gorge area are M. nattereri and P. austriacus (http://www.mos.gov.pl/natura2000). The Narew basin harbours around 40 mammal species. B. barbastellus, Myotis dasycneme, M. myotis, C. fiber, C. lupus and L. lutra are of high conservation value. M. dasycneme, one of the most endangered bats in Poland inhabits the Biebrza River valley. The site is also an important refuge for L. lutra and C. fiber. In the Bug valley, beaver, otter, Capreolus capreolus, E. serotinus, Martes martes and S. betulina are typical mammals. Beavers recolonized the Pilica River valley in 1984, followed by otters in mid-1990s. Other still recorded mam-

Chapter | 16 Baltic and Eastern Continental Rivers

Old oak forests and large patches of alluvial forests in the Pilica valley are of high conservation value (http://www.mos. gov.pl/natura2000).

16.3.11. Human Impacts and Special Features 16.3.11.1 Pollution The main threats to the Vistula River are point and non-point pollution, water abstraction, flow regulation and sediment loads. The Vistula River basin is inhabited by more than 22 million inhabitants. Over 50% of them inhabit urban areas. Population density is the highest in the Little Vistula basin (379 inhabitants/km2, in the area of Katowice, Gliwice), Upper Vistula basin (215 inhabitants/km2, in the area of Krak ow ), compared to the average density (114 inhabiow in the upper tants/km2) in the entire catchment. Krak course (756 000 inhabitants), Warsaw in the middle section (1 700 000 inhabitants) and Gda nsk in the delta (456 000 inhabitants) are the most important urban areas in the catchment (GUS 2007). The Vistula River serves as a major source for industrial and municipial water and as a main recipient of sewage, of which 70% is insufficiently treated or untreated (Dojlido & Wojciechowska 1989). In 2005, 1 096 000 m3 of municipal and industrial wastewater entered the river (987 000 m3 treanska 2006). In ted, 109 000 m3 untreated) (Grzesiak & Doma particular, the upper Vistula near Krak ow and the middle Vistula near Warszawa are heavily polluted (Figure 16.2, water quality classification after Dz. U. Nr 32, poz. 284. 2004). The lowest water quality occurs in the upper Vistula, but the main tributaries also are highly polluted (Figure 16.2).

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A total of 1452 (52%) running water bodies (according to EU-WFD 2000/60/EC) in the Vistula basin are classified as not endangered by water abstraction or by pollution, 762 (27%) are potentially endangered and 592 (21%) are endangered (MS, 2005). The most threatened waterbodies are in the industrialized upper (near Krakow) and middle (near Warszawa) reaches. These areas are also heavily affected by non-point pollution. In the lower basin, the Vistula is polluted by many point sources (e.g. near Gdansk) (Niemirycz 1997; Niemirycz et al. 2004). The water quality of theVistula, Bug, Narew and Pilica Rivers is often poor because of aquaculture (salmon and carp). Low water quality in the main Vistula and its tributaries urgently require the construction of sewage treatment plants, the restoration and protection of riparian zones, and better water and landscape management (especially in agriculture) (Kajak 1992; Laenen & Dunnette 1997; Nienhuis et al. 1998; Romanowski et al. 2005; Van der Sluis et al. 2007). Modern, biologically oriented approaches, for example, an ecohydrological approach (Zalewski 2000; Zalewski & Wagner-Łotkowska 2004; Zalewski 2006), are particularly recommended. The Vistula discharges high nutrient loads into the Baltic Sea. On average, it transports 833 000 tons of sediment per year to the delta (1946–1995). About 90% of suspended material in the upper Vistula was supplied by mountain tributaries (Łajczak 2003). Gravel transport caused an additional sediment load of 30 tons/km2/year in the upper Vistula, 20 tons/km2/year in the middle Vistula near Warsaw, and 10 tons/km2/year in the lower reach near Tczew (GackaGrzesikiewicz 1995). Increased sediment load, enriched with nutrients, together with the deposition of heavy metals, due to industrial development in the upper Vistula–Silesia FIGURE 16.2 Water quality of the Vistula and its major tributaries (after Grzesiak & Domanska 2006).

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TABLE 16.2 Total annual load (tons per year) of pollutants discharged by the Vistula River into the Baltic Sea (after MS, 2005) Parameter BZT5 ChZTCR Total nitrogen Nitrate Ammonium Organic nitrogen Total phosphorus Phosphate Zinc Copper Lead Nickel Chromium Mercury Cadmium

Total load (tons/year) 141 143 1 018 895 147 480 96 513 6119 43 971 7065 3119 683 156 29 72 17 2 1

region, led to degradation in water quality during the 20th century (Zober & Magnuszewski 1998; Wilk 2005). The total annual load of the Vistula basin to the delta is 113 969 tons of total N and 8575 tons of total P. Up to 50% came from non-point sources (Table 16.2) (Rybi nski & Niemirycz 1986). Point sources provided 19 348 tons of total N, 2201 tons of total P, 24 892 tons of BOD, 86 607 tons COD and 41 468 tons of suspended solids (MS, 2005). Many large tributaries in the Vistula basin, including the Narew, Bug and middle mainstem, remained morphologically and hydrologically in a semi-natural state. However, they are often heavily polluted, suggesting that good ecological status of these rivers (according to the EU-WFD 2000/60/ EC) can be achieved only by reducing the pollution load (Dombrowski et al. 2002). To improve overall ecological river status, a holistic ecohydrological strategy, including the elimination of point pollution sources and the limitation of non-point sources using proper landscape management, have been successfully implemented in some sections of the Vistula basin, e.g. Pilica basin with Sulej ow Reservoir (Wagner & Zalewski 2000; Łapi nska et al. 2001; Zalewski 2002; Zalewski & Wagner-Łotkowska 2004; Zalewski 2006).

lead, 2100 tons of nickel, 190 tons of cadmium, 51 tons of polyaromatic hydrocarbons, 46 tons of mercury, 1.5 tons of chloroorganic pesticides and 0.55 tons of pesticides (Bojakowska 1999). Damming has caused a progressive decline in migratory fishes. Almost all anadromous and catadromous fishes in the Vistula River are considered as threatened, (Bontemps 1976; Backiel 1985; Wozniewski 1999). Effective fish-passes are indispensable for potamodromous migratory species (e.g. nase, barbel and grayling). The nase, C. nasus L., was one of the most abundant rheophilic species in the Vistula until the 1960s. Today, it is one of the most threatened rheophilic fish in Poland (Witkowski et al. 1999; Heese 2000; Kaczkowski 2004) because Włocławek dam has stopped its migration. Similarly, the migration of Vimba vimba was ceased because of the dam (Backiel & Bontems 1996). Sturgeon (Acipenser sturio), razorfish (P. cultratus) and natural populations of salmon (S. salar) disappeared in the Vistula almost a century ago. Sea trout, eel, reintroduced Atlantic salmon and lampreys are seriously endangered (Backiel & Penczak 1989). Before the construction of Włocławek dam, several fishes were commercially important, e.g. bream (41% of total catch), sea trout (11%), vimba (11 %), barbel (6.5%), pike (5%), zander (4%) and asp (3%). Today, bream, roach and silver bream contribute 95% of the total commercial catch (Wisniewolski 2002). Changes in the fish community also occured in dammed tributaries. The abundance of obligatory riverine species (B. barbus, L. cephalus, L. leuciscus, Gobio gobio, C. nasus) was drastically decreased in the Pilica River (Penczak & Kruk 2000). Nase, barbel and dace became almost extinct; chub and gudgeon are now considered vulnerable (Kruk & Penczak 2003). The significant influence of Siemian owka and Zegrzynski (D˛e be) reservoirs on the Narew River fish community is also documented (Penczak et al. 1990a). There are several projects, concepts and scenarios, how to avoid harmful effects of Włocławek dam. These comprise building a new large dam downstream (at Nieszawa) that considers the mitigation of environmental impacts (HydroprojektWarszawa 2004; Romanowski et al. 2005; Van der Sluis et al. 2007; Zalewski et al. 2005), constructing the Lower Vistula Cascade that will include 7 new dams, or removal of the _ existing dam (KERM 2000; Fiedler-Krukowicz & Zelazo, 2000; WWF 2001; Majewski 2002).

16.3.11.2 Damming and Channelisation Intensive regulation and channelisation of the Vistula started at the end of the 19th century. The construction of groynes that narrowed and deepened the channel was most intensive in the mid 20th century. Damming started in 1930 with most dams used for water supply, power production, flood protection and navigation. According to the Polish Geological Institute, the accumulated sediments in Włocławek reservoir contain 36 600 tons of mineral oils, 15 000 tons of zinc, 7600 tons of chromium, 4200 tons of copper, 2200 tons of

16.3.11.3 Non-Native Species Many non-native species inhabit the Vistula basin (http:// www.nobanis.org). The most important and often invasive non-native crustaceans are Gammarus tigrinus, Dikerogammarus haemobaphes, Pontogammarus robustoides, Obesogammarus crassus and Orconectes limosus; the mollusc Dreissena polymorpha; the fishes C. carpio, Ctenopharyngodon idella, Hypophthalmichthys molitrix, H. nobilis, Salvelinus fontinalis, Oncorhynchus mykiss, Pseudorasbora

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parva, Ictalurus nebulosus, Perccottus glenii, Neogobius fluviatilis, N. gymnotrachelus and Neogobius melanostomus; the bird Phasianus colchicus; the mammals Castor canadensis and Mustela vison; and the plants E. canadensis, Bidens frondosa, Xanthium albinum, Fallopia japonica, Impatiens glandulifera and Solidago canadensis. Almost 35% of the Polish fish fauna are introduced nonnatives (Witkowski et al. 2004). The Chinese Amur sleeper (P. glenii), a fish that originates from eastern Siberia, and three Ponto-Caspian goby species (N. melanostomus, N. gymnotrachelus and N. fluviatilis) are considered as invasive species (Kostrzewa & Grabowski 2003, http://www.nobanis. org). P. glenii was first observed in Poland in 1993 in an oxbow lake of the Vistula River near D˛e blin. Since then, it has spread in both the Vistula and Bug Rivers (Danilkiewicz 1996, 1998; Kostrzewa et al. 2004). Aquaculture plays a major role in introducing cyprinids such as C. carpio, C. idella, H. molitrix and H. nobilis. For recreational and commercial reasons, S. fontinalis and O. mykiss were introduced (Witkowski 1996; Backiel 1995). The goby species most probably reached the Vistula through artificial channels joining the Ponto-Caspian and Baltic basins. The round goby (N. melanostomus) was probably transported with ballast waters along the Volga River– Lake Beloye–Lake Onega–Lake Ladoga–Neva River–Baltic Sea route. It was first found in 1990 near the Hel Peninsula, then colonized the Vistula lagoon, parts of the Vistula River and the Gulf of Gda nsk. The racer and monkey gobies (N. gymnotrachelus, N. fluviatilis) arrived most probably through the Dnieper–Pripyat’–Bug–Vistula river corridor. The racer goby was first recorded in 1995 in the Bug River.

In the Vistula River, it was first noted in 2000 and the monkey goby in 2002 (Danilkiewicz 1996, 1998; Kostrzewa et al. 2004). The northern and central corridors are considered the major invasion routes of Ponto-Caspian species. One of most spectacular entry through these corridors was by the zebra mussel D. polymorpha. These routes have probably also been used by few alien amphipods that have almost completely replaced the native species in the Vistula and Oder Rivers. During the last decades of the 20th century, the non-native gammarids G. tigrinus, D. haemobaphes, P. robustoides and O. crassus invaded the lower Vistula River and its delta. In the brackish Vistula lagoon, the progressive decline of native Atlantic-boreal species Gammarus zaddachi and Gammarus duebeni were most likely caused by these non-natives. Pollution and eutrophication of the lagoon have favoured the spread of these non-native species. Now, the alien amphipods continue spreading towards western Europe through connecting waterbodies (Ja_zd_zewski 1980; Bij de Vaate et al. 2002; Ja_zd_zewski et al. 2002; Grabowski et al. 2006).

16.4. NEMUNAS RIVER The Nemunas originates in the Minsk Uplands (Belarus) and flows into the Curonian lagoon in the eastern Baltic Sea. The catchment (98 757 km2) drains parts of Lithuania (48% of the total area) and Belarus (46%) as well as small areas of Poland, Russia and Latvia. The total length is 937 km. Around 462 km are in Belarus, 17 km along the border

PHOTO 16.3 Nemunas at Merkine (Photo: Ricardas Skorupskas).

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between Belarus and Lithuania, 475 km in Lithuania, and for 99 km the river forms the border between Lithuania and the Kaliningrad enclave (Russia) (Kilkus 1998; Gailiusis et al. 2001). The entire catchment is in the eastern continental ecoregion. The catchment is bordered by the Venta, Lielupe and Western Dvina in the north, the Dnieper in the east, the Pripyat’ (a tributary to the Dnieper) and the Bug (a tributary to the Vistula) in the south, and the Pregolja in the southwest. The longest and largest tributaries in Belarus are the Scara (lengh: 325 km, area: 6730 km2) and Katra (109 km, 2010 km2) Rivers (Nacianaliny Atlas Belarusi 2002). The main tributaries in Lithuania are the Merkys, Neris (with Zeimena and Sventoji), Nev_ezis, Dubysa, Sesup_e, Jura and Minija Rivers (Photo 16.3).

16.4.1. Human History The first human settlements in the Nemunas valley date back to the post-glacial period. In Neolithic times, the upper Nemunas was colonized by hunting and fishing tribes. Later, the upper and middle Nemunas were mostly populated by Baltic tribes, but as early as the 11–12th centuries these settlements included Slavoniane. The Nemunas and Neris Rivers served as important trad routes that linked main towns and smaller settlements. The high banks were well suited for the construction of castles and fortresses, providing excellent defensive positions (Kilkus 1998; Palutskaya 2003). River engineering for removing snags and deepening the main channel already began in the 16th century. In the 19th and early 20th century, a regular steamboat connection between Kaunas (Lithuania) and the eastern Prussian frontier, as well as between Grodno (in contemporary Belarus) and Druskininkai (Lithuania), were established. Due to the rapid development of railways, the importance of the Nemunas and its tributaries as transport routes were significantly diminished later. After WWII, Belarus, Lithuania and eastern Prussia (the latter forming the present Kaliningrad region of Russia) fell under control of the Soviet Union. Since the early 1990s, the former frontiers between Lithuania, Belarus and Russia have been re-established (Palutskaya 2003).

16.4.2. Physiography and Climate The landscape has been strongly shaped by the Medininkai (Pripetskoe) and Nemunas (Paazerskoe) ice cover during the Dneprovskij, Valdaiskij and Sozskij glaciations. As a result, the entire catchment is virtually covered by a 100–200 m thick layer of moraine deposits. The last glaciation had a particularly strong influence upon the contemporary morphology of the river basin. Deposited coarse till formed hills, finer materials (sand, clay sand, fine gravel) were blanketed over large areas. From SW to NE, the whole central basin is traversed by the Baltic Moraine Ridge. The highest river terraces were formed 12–10 kyrs BP, the middle terraces 10–8 kyrs BP, and the lowest about 8 kyrs BP. The upper

PART | I Rivers of Europe

course was already formed before, and the middle and lower courses during and after, the last glacial period. The rugged hilly relief surrounding the basin is the result of processes accompanying the recession of glaciers (Geology of Lithuania 1994; Nacianaliny Atlas Belarusi 2002; Palutskaya 2003). The Minsk Uplands are between the upper courses of the Nemunas and Neris Rivers. The upper and middle parts of the basin are surrounded by the Novogrudok (Nau gardukas), Volkovyjsk and Zemaitija hills, the Augustow (Augustavas) hollow, as well as by the mid-Lithuanian, Karsuva, Uznemun_e and Pajurio lowlands. The prevailing altitude of the hills is 150–200 m asl, and the valley floor is at 100–150 m asl. The catchment is covered mainly by moraine and sandy loams intermixed by peat formations. Loams prevail in the northwest (Minija, Jura, Dubysa and Nev_ezis tributaries) and south of the Baltic Moraine Ridge. Sand and sandy loams dominate in the upper Nemunas basin, Jura basin, eastern Dubysa basin, lower Neris basin, south of Kaunas (between the Nemunas and Esia) and locally in the Minija basin. Sandy-muddy deposits cover the Nemunas delta (Geology of Lithuania 1994).

16.4.3. Land Use Over 50% of the catchment has been converted into agricultural land, meadows and pastures. Forests cover 37% of the basin in Belarus, 30% in Lithuania and 17% in Russia. Forests belong to the North Atlantic moist mixed type with pine, birch, alder, aspen and oak as dominant species (Kilkus 1998).

16.4.4. River Geomorphology The Nemunas is a large lowland river that starts at 179 m asl near Minsk in Belarus. First, it flows westwards to Grodno, then turns north by crossing the Baltic Moraine Ridge and finally turns again west from Kaunas to the Baltic Sea. The upper basin (Minsk, Brest and Grodno regions) drains 32 983 km2, including 27 large tributaries. The 300 km long middle course extends from the Katra tributary to the confluence with the Neris River in Kaunas, draining 38 272 km2 including 11 large tributaries. The lower 200 km long section drains 24 914 km2 including 19 large tributaries. The delta starts 48 km upstream of the mouth. The Atmata branch is considered the main delta channel. The largest island in the delta is Rusn_e (area: 45 km2). Several tributaries such as the Sysa and Minija (3 km from the sea) enter the delta (Kilkus 1998; Nacianaliny Atlas Belarusi 2002). The average water depth varies from 1 m (upper section) to 3 m (lower reach). The mean channel width ranges from 100–150 m (upper course) to 200–400 m (lower course). The slope is 0.64, 0.69 and 0.2 m/km in the upper, middle and lower courses, respectively. The mean coefficient of meandering is 1.86 (upper course), 2.26 (middle course) and 1.21 (lower course) (Gailiusis et al. 2001).

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16.4.5. Climatic Conditions In the upper and middle reaches of the Nemunas, the climate is of a temperate continental type. The Baltic Sea provides rather unstable weather conditions and thaws are frequent in winter. The average annual air temperature varies between 5.5 and 6.5 C. Average temperature is 4.5 to 9 C in January and 17–19 C in July (with maxima of 30–37 C). Annual precipitation ranges from 520 to 800 mm. Precipitation is higher in the hilly areas and fluctuates considerably from year to year with an interannual variation of up to 40% (Kilkus 1998).

16.4.6. Hydrology The total annual discharge of the Nemunas is 25 km3. The main water sources are snowmelt (40% of the annual mean), groundwater (35%) and rain (25%). Hence, discharge peaks in spring (41–46% of total annual flow), followed by autumn (19–22%), winter (17–21%) and summer (15–18%). Floods are common in spring, but may also occur in summer and autumn. Spring floods usually start in March. The water level can rise 2–3 m in the headwaters and delta and up to 10 m in the middle reach (Kilkus 1998). The spring flood usually lasts for 60 days and peak discharge exceeds 5–10 times the mean discharge. Extreme floods occurred in 1829 and 1958.

16.4.7. Temperature Regime and Hydrochemistry In Lithuania, the mean summer water temperature is 17– 18 C (average value since 1945) and decreases from upto downstream. In winter, the Nemunas can partially freeze. In the downstream section, ice cover starts mid-December and lasts between 48 and 98 days. However, during warm winters the Nemunas may remain completely ice-free. Hydrochemical characteristics in the downstream part of the Nemunas are as follows (annual average in 2005): pH: 8.2, HCO3: 129.3 mg/L, SO4: 76.5 mg/L, O2: 8.7 mg O2/L, oxygen saturation: 79%, BOD7: 4.3 mg O/L, CODCr: 29 mg O2/L, CODMn: 9.8 mg O2/L, NH4–N: 0.11 mg N/L, NO2–N: 0.02 mg N/L, NO3–N: 1.1 mg N/L, total N: 2.22 mg/L, PO4–P: 0.05 mg P/L, total P: 0.15 mg/L, conductivity: 557 mS/cm and total hardness: 7.8 mg-eq./L (Lithuanian Environmental Protection Agency, http://aaa. am.lt/VI/files/0.356876001144137886.xls).

16.4.8. Major Tributaries Tributaries of the Nemunas described below are listed from upstream to downstream (Gailiusis et al. 2001). The Merkys, a right-bank tributary, is the longest river in southeast Lithuania. Merkys is a fast-flowing river, with a channel slope of 0.10–0.12%. Pine forests cover 40% and

swamps 10% of the basin. Annual precipitation is 700– 750 mm. In contrast to other Lithuanian rivers, water temperature peaks in June and does not exceed 18 C. Merkys normally does not freeze in winter. Because of high forest cover and low human impacts, the river is relatively unpolluted. Snow melt provides 35% to the annual runoff. The Neris (called Vilija in Belarus) is the longest and largest right-bank tributary of the Nemunas. It starts near the Minsk highlands in Belarus. It has 10 tributaries longer than 50 km. About 56% of the river basin is situated in Lithuania. The riverbed slope is 0.02–0.03%. Forests cover 28%, wetlands 10% and lakes 2.5% of the basin. The Neris has two large right-bank tributaries: the Zeimena and the Sventoji. The Zeimena is one of the least polluted rivers in Lithuania. Groundwater contributes 60% to its total runoff. Forests cover 31% and lakes 6.4% of the basin. Annual precipitation in the Sventoji catchment is 750 mm and its mean discharge is 56.5 m3/s. Groundwater contributes 40%, snow 32% and rain only 28% to total runoff. The Sventoji basin includes 658 lakes (>0.5 ha). Three of them are larger than 10 km2. The Nev_ezis, a large right-bank tributary of the Nemunas, just after the mouth of the Neris, is the most important midLithuanian river. The mean slope of the riverbed is only 0.035% (0.007% in the lower section). The basin is affected by major anthropogenic activities (Panev_ezis and K_edainiai, both with 150 000 inhabitants). The Dubysa enters the Nemunas from right after the Nev_ezis. It drains an elongated N–E oriented catchment that is dominated by agricultural activities that pollute the river. Forests cover only 13% of the basin. The second-largest left-bank tributary of the Nemunas (the largest is the Scara in Belarus), the Sesup_e River, originates in the Suduva Hills in Poland, drains the central lowlands of Lithuania and flows for 60 km through the Kaliningrad region before joining the Nemunas at Smalininkai, 85 km from the sea. Lakes >0.5 ha cover 2% of its basin (total area: 68 km2). Wetlands include 8.4% and forests 15% of the catchment. The Jura River enters the Nemunas from the right, 81 km upstream from the sea. Annual precipitation in its basin can be as high as 900 mm, and rainfall dominates annual runoff (50%). The Minija (the last rightbank tributary) is a lowland river in northwest Lithuania. Annual precipitation in its basin is comparatively high (960 mm) and rainfall forms 55% of annual runoff. Floods are common, particularly in spring. Larger cities and industrial centres are absent.

16.4.9. Biodiversity Between 1968 and 1999, 455 phytoplankton taxa were identified by sampling 177 Lithuanian rivers in the Nemunas basin. Diatoms (42% of all species), chlorophytes (34%) and blue-green algae (13%) had the most species. The most common genera were Oscillatoria (6 species), Phormidium (8), Anabaena (5), Dinobryon

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(5), Aulacoseira (7), Cyclotella (6), Cymbella (15), Fragilaria (19), Gomphonema (13), Gyrosigma (8), Navicula (24), Nitzschia (17), Pinnularia (12), Surirella (14), Synedra (4), Phacus (10), Trachelomonas (12) and Ankistrodesmus (7) (Kostkeviciene_ et al. 2001). All in all, 45 macrophyte species were found in the Nemunas. In small rivers (catchment area <100 km2), 18 species including the common Veronica anagalis-aquatica, Nuphar luteum, E. canadensis, Berula erecta and Potamogeton x meinshauseni were observed. In medium-sized rivers (100–1000 km2), 32 species occurred. Fontinalis antipyretica, N. luteum, P. pectinatus, Potamogeton lucens, P. natans, Potamogeton perfoliatus, P. x cf. nitens, P. x meinshauseni, P. x cf. salicifolius, Sagittaria sagittifolia, Schoenoplectus lacustris, E. canadensis, Sparganium emersum, Amblystegium riparium, B. erecta and Butomus umbellatus were common. In large rivers (catchment area >1000 km2), 32 species occurred. In addition to the common species in mediumsized rivers, Spirodela polyrhiza, Myriophyllum spicatum, Agrostis stolonifera, Batrachium sp. and Chara contraria dominated (Sinkevicien_e 2005). In 1999, 87 macrozoobenthic species were identified in the Lithuanian part of the Nemunas, including 18 Ephemeroptera, 21 Chironomidae, 15 Mollusca, 4 Plecoptera, 7 Trichoptera, 4 Coleoptera, 1 Heteroptera, 5 Odonata, 5 Hirudinea and 7 higher Crustacea (Bubinas & Jagminien_e, 2001). Fifty-four fish species were recorded in the Nemunas basin. The most common fish in the middle reach was bream (A. brama). According to data published by the Grodno Oblast Committee for Natural Resources and Environmental Protection, bream contributed 45–90% of the total catch during the last few years in the Belarus part of the Nemunas. Silver bream and roach were the second and third most abundant species. Other common species were pike, perch, asp and barbel (Palutskaya 2003). Neither the Nemunas or its tributaries have high commercial fishery value. Salmonids (Atlantic salmon and sea trout) have disappeared in the catchment due to the construction of Kaunas hydropower station that closed access to upstream spawning areas. Salmon is considered an endangered species in the Nemunas basin and is included in the Red Data Books of Belarus and Lithuania. Seasonal salmon migration still continues through the Neris River that enters the Nemunas downstream of Kaunas dam (Gaigalas 1996; Nacianaliny Atlas Belarusi 2002). There are no records of salmon migration beyond the Belarus border. Five endangered bird species (spotted eagle, white-tailed eagle, great snipe, corncrake and aquatic warbler) occur in the Nemunas basin. The most important bird area in Lithuania is the Nemunas Delta Regional Park. On their way from the Arctic via Europe to Africa (and back), migrating birds pass the Nemunas delta. Another bird protection area has been designated near Lake Zuvintas in Lithuania, where key species are the common buzzard, grey heron and white stork (Palutskaya 2003).

PART | I Rivers of Europe

16.4.10. Human Impacts and Special Features The Nemunas River is heavily influenced by urbanisation, agriculture and the introduction of non-native species. Amelioration and damming of tributaries have also caused significant impacts. The largest cities in the basin are Grodna (317 000 people) in Belarus, and Vilnius (554 000), Kaunas (360 000) and Panev_ezys (116 000) in Lithuania. Smaller towns include Lida (100 000) and Maladzecna (98 000) in Belarus and Alytus (70 000) and Marijampol_e (71 000) in Lithuania and Tilze (43 000) in Russia. In the middle reaches of the Nemunas, Kaunas hydroelectric power station (223 km from the mouth) was built (1959–1961), forming the reservoir between Prienai and Kaunas. Dam operation can cause large daily discharge fluctuations (120–600 m3/s), seriously impacting the downstream ecosystem (Kilkus 1998). In the Neris–Vilija river system, 26 dams with a total storage capacity of 9.5 million m3 occur. In 1976, the Neris was dammed in Belarus near Vileika to form a 67 km2 reservoir with a storage volume of 260 million m3. Today, the mean discharge below Vileika reservoir is 12 m3/s (Kilkus 1998).

16.4.11. Water Quality According to the national quality system, the upper reaches of the Nemunas, near the town of Stolbcy (in Belarus), were classified as relatively clean (Palutskaya 2003). Between Mosty to Grodno, the river was moderately polluted, mainly due to petrochemicals and heavy metals. Downstream of Grodna, the concentration of petrochemicals was 60 times higher than the maximum allowed level. There are 610 small industries in the Belarus part of the Nemunas basin, mainly dairies, cheese producers, machine-repair, flax factories, distilleries and small meat-processing units. The Environment Protection Agency in Lithuania assessed the Nemunas as moderately polluted or polluted according to their water quality classification based on macroinvertebrates (Biotic Index) and phytoplankton (Saprobic Index) (Palutskaya 2003, http://aaa.am.lt). The main pollutants were organic matter from agriculture and sewage, as well as petrochemicals from urban areas. Low water quality was particularly observed downstream of Panev_ezis along the Nev_ezis, and at Alytus and Kaunas along the Nemunas. According to the Saprobic Index, the highest quality occured upstream of Alytus (near the Belarus border) and in the section upstream of the Kaliningrad region (near Smalininkai). Compared with the Nemunas, the Lithuanian part of the Neris has higher water quality (slightly polluted or unpolluted according to the Saprobic and Biotic Indices), although the largest city in the entire basin (Vilnius) is located here. In the lowermost Russian section, the Nemunas was considered moderately polluted, mainly due to paper mills near Sovetsk (Tilze_ ) (Palutskaya 2003). High concentrations of ammonium, nitrate, nitrite, BOD5 and iron were measured just upstream of the river mouth.

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16.4.12. Protected Areas The Belarus part of the Nemunas basin includes Narocanskij National Park (created in 1999, area: 94 000 ha), around 20 protected areas of national importance with limited public access, and 68 areas of local importance (Nacianaliny Atlas Belarusi 2002). In Lithuania, about 5% of the Nemunas catchment is protected. It includes three national parks: Dz ukijos (created in 1991, area: 55 900 ha), Aukstaitijos (1974, 40 000 ha) and Traku˛ (1991, 8300 ha); one biosphere reserve (Zuvintas Bird Protection Area, 1949, 18 493 ha); Cepkeliai (1974, 11 212 ha) and the Viesvil_es reserves (1991, 3216 ha). The Kaliningrad region (Russian Federation) includes three national protected areas (Palutskaya 2003).

16.5. WESTERN DVINA RIVER 16.5.1. Introduction The 83 746 km2 Western Dvina River (Daugava in Latvian) is a transboundary river that drains parts of five countries (Russia: 21% of the total catchment, Belarus: 38%, Lithuania and Estonia: 13%, Latvia: 28%) before it enters the Baltic Sea in the Gulf of Riga. The river is 1005 km long; 325 km are in Russia, 328 km in Belarus and 352 km in Latvia. The largest tributaries in Russia are the Toropa (length: 174 km, area: 1950 km2) and Meza Rivers (259 km, 9080 km2), in Belarus the Kasplja (136 km, 5410 km2), Obolja (148 km, 2690 km2), Disna (178 km, 8180 km2) and Drissa Rivers (183 km, 6420 km2) and in Latvia the Dubna (105 km, 2780 km2), Aiviekste (114 km, 9160 km2) and Ogre Rivers (188 km, 1730 km2) (The Encyclopaedia of Latvia’s Nature 1994–1998, http://www.rubricon.com). The catchment is

bordered by the Narva (Velikaja) and Volhov (Lovat’) Rivers in the northeast, the Volga in the east, the Dnieper in the south and southeast, the Nemunas in the south and southwest, the Lielupe in the west and the Gauja in the north (Photo 16.4).

16.5.2. Historical Perspective Records of paleolithic people living in the Western Dvina basin date back to 100 to 40 kyr BP. After the last glaciation (20–18 kyr BP), a new immigration began. In the 9th millennium BC, the region became occupied by hunting tribes from southern Europe, while in the 6–5th millennium BC new tribes arrived from the east. In the 3rd millennium BC, ancestors of Livs, Estonians and Finns (Finno-Ugric tribes) immigrated. Early Baltic tribes – the ancestors of Latvians and Lithuanians – arrived in the 2nd millenium BC. The Western Dvina was a main trading route from Varangians to Greece, the so-called route of the Vikings. Slavonic tribes arrived at the Western Dvina between the 5th and 7th century, when Kriviches had their center in Polatsk. Polatsk and Vicebsk were the main towns between the 9th and 11th centuries in the territory of contemporary Belarus. In 1201, Riga was founded by German Christians at the mouth of the river. Germans conquered the land, and between the 13th and 16th century it belonged to the Livonian Order. After the Livonian War, the Polish-Lithuanian Empire took control of the eastern river basin (Trans-Dvina), while the western part remained independent. Russia occupied the area at the beginning of the 18th century after the Northern War. Then the lower reaches of the Western Dvina belonged to the Latvian Republic (1918–1940), and the middle and upper reaches to the Soviet Union. After the WWII, the PHOTO 16.4 Western Dvina near Daugavpils (July 2005, Photo: Ivars Druvietis).

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Soviet Union controlled the Latvian territory until Latvia regained its independence in 1991 (Apinis 2000). Today, commercial inland navigation along the Western Dvina is absent except for the first 10 km from the Baltic Sea, which serves as the entrance for deep-sea vessels to the port of Riga. Three major hydropower plants prevent navigation in the lower river. An old canal north of Riga, built around 1900, links the Western Dvina with the Gauja River. It was used for timber floating but is now derelict.

16.5.3. Biogeographic Setting The Western Dvina basin belongs to Ecoregion 15 (Baltic Province). In accordance with the Northern European classification, Latvia is in the Baltic geobotanical province, which is divided into western and eastern Baltic sub-provinces and eight geobotanical regions (Illies 1978). The recent river valleys were mainly formed after the recession of the ice cover 10–11 kyrs BP. All Latvian rivers, including those in the Western Dvina basin, are divided into three geological types: (i) carbonate riverbeds mainly consisting of Devonian sediments, (ii) sandy riverbeds consisting of quaternary sediments and (iii) organic sediments built of post-glacial sediments. The Western Dvina valley has been formed by (1) glacial meltwater gradually deepening the river, (2) several changes in tributary glacier basins and sea level changes in the Baltic Sea and (3) earth crust movements and climate change (Daugava River Basin 2003).

16.5.4. Physiography and Climate Latvia, situated in the western East European plain, is covered by a thick (500–2000 m) layer of sedimentary rocks on top of crystalline basement. The basement is composed of metamorphosed and dislocated pre-Cambrian rocks, while sedimentary rock cover is mainly composed of carbonate (hemogenic, chemical settling) and ground-generated (clastical, ruin) formations. Geologically, the Western Dvina basin is covered by a 200 m thick layer of glacial deposits. These deposits originate primarily from the Weichselian (Latvian) glacial period and are characterised by till, sandy till and glaciolacustrine sand. After the ice age, alluvial sediments (ancient and contemporary), and peat and lake sediments were deposited (Kurss & Stinkule 1997). The climate is controlled by the Atlantic Ocean (lower basin) and by a continental influence (upper basin). The lower basin has mild winters and cool summers, while the upper part exhibits high seasonal variation. The average annual precipitation ranges from 600 to 800 mm, with higher values in the lower basin. The average number of days with precipitation is 140–220/year. The hydrological regime of the Western Dvina is mainly driven by the hydrometeorological conditions outside of Latvia (i.e. in Russia and Belarus) (K¸lavi¸ns et al. 2002).

PART | I Rivers of Europe

16.5.5. Landscape and Land Use The Western Dvina basin is situated in the hemi-boreal vegetation zone, a transition zone from the boreal (taiga) to the nemoral zone. Forests are dominated by scotch pine and spruce intermixed with broad leaf trees. Large areas of the basin are still covered by meadows and bogs (Table 16.1). The land use in the basin is characterized by a complex mosaic structure. According to the CORINE Land Cover base, the basin is mainly covered by agricultural (48%) and forested land (45%) (Daugava River basin, 2003). The Western Dvina basin has an elongate shape and thus large tributaries are absent. It starts as the outlet of Lake Dvineca in Russia where the channel is about 6–8 m wide. At the Belarus–Latvia border, the river flows in a 0.5 km wide old valley and the channel is up to 200 m wide. In the lower reaches (in Latvia), channel width ranges from 370 to 750 m and water depth from 5 to 15 m. There, the river is fringed by expansive floodplains (3–4 km wide) containing multiple oxbow lakes that have been formed during the last 3000–5000 years. In the lowest section (up to 22 km from the sea) the water is brackish. In Latvia, the Western Dvina can be divided according to geomorphic, hydrological and ecological features into three parts: (1) the upper part from the Belarus border to P¸lavi¸nu reservoir, (2) the middle part formed by a cascade of reservoirs and (3) the lower part beginning 30 km from the mouth. The Western Dvina valley in Latvia (particularly in the P¸lavi¸nu–Aizkraukles stretch) has a two-level form. A relatively wider valley in the upper part has been formed in till and clay. The V-shaped lower level valley lies in dolomite and is narrow (0.3–0.6 km wide) and deep (up to 30 m in the vicinity of Staburags and Koknese). More downstream, the depth of the river valley exceeds 50 m (Eberhard 1972; The Encyclopaedia of Latvia’s Nature 1994–1998).

16.5.6. Hydrology and Temperature The Western Dvina has a snowmelt dominated flow regime with long lasting floods in spring. Snowmelt water contributes 50–55% and groundwater 30–35% to the total annual discharge. Late summer rains can cause additional flow peaks, while flow remains low during mid-summer and winter periods (about 15% of total annual discharge). In winter, a 20–40 cm ice layer covers the river. The average river network density within the basin is about 830 m/km2, but varies within the basin (The Encyclopaedia of Latvia’s Nature 1994–1998; K¸lavi¸ns et al. 2002). Records of flow in the Western Dvina date back to the early 19th century. Regular hydrometrical observations started in 1906 at the gauging stations Daugavpils and Jekabpils. Discharge in late March early April can reach 2000 m3/s in the mainstem and up to 200 and 100 m3/s in the large tributaries Aiviekste and Dubna, respectively. A second flow peak generally occurs from autumn floods (Ziverts 1996). The annual river discharge remained relatively constant

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between 1881 and 2004, although winter discharge (December–February) exhibited a significant increase during this period.

16.5.7. Biogeochemistry The chemistry of the Western Dvina in Latvia is controlled by the headwaters in Russia because they contribute most to annual discharge. The Aiviekste and Ogre are the most important tributaries in Latvia. Upstream of the town Jekabpils, the Western Dvina remains relatively unaffected. Mean values (1995–2002) are: pH: 7.8, HCO3: 151 mg/L, SO4: 27.5 mg/L, Cl: 9.9 mg/L, Ca: 43 mg/L, Mg: 10.9 mg/L, NO3–N: 0.82 mgN/L, NO2–N: 0.007 mgN/L, Ntotal: 1.95 mgN/L, PO4–P: 0.038 mgP/L, total P: 0.058 mgP/L, Na: 5.6 mg/L, K: 2.7 mg/L, BOD7: 1.90 mgO/L, CODSO4 : 37:0 mg=L; NH4–N: 0.10 mg/L, total hardness: 3.1 mg-eq./ L, oxygen saturation: 80% and conductivity: 362 mS/cm (K¸lavi¸ns et al. 2002). The Western Dvina substantially influences the water and material balance in the Gulf of Riga, Baltic Sea. It contributes 66% of the total phosphorus, 49% of the total nitrogen, 53% of the mineral substances and 64% of the organic matter (expressed as CODCr) to the Gulf of Riga. Nitrate and nitrite concentrations have remained relatively constant in time, while the ammonium concentration has significantly decreased over time (K¸lavi¸ns et al. 2002; Figure 16.3). Similarly, COD exhibited a decreasing trend, partly as a consequence of decreasing human impacts since 1991.

16.5.8. Aquatic and Riparian Biodiversity Aquatic and riparian biodiversity data are only available for the middle and lower river in Latvia. A total of 480 algae species have been identified from the Western Dvina, among them 65 cyanophytes, 20 chrysophytes, 131 bacillariophytes, 11 pyrrophytes, 15 euglenophytes, 3 xanthophytes and 235 chlorophytes (Kumsare 1967, 1974). The Western Dvina has a rich benthic invertebrate fauna, the richest of all rivers in Latvia, due to its high habitat and ecosystem diversity. More than 440 species are found in the Latvian section of the Western Dvina, including 94 caddisflies, 53 chirono-

mids, 35 mayflies, 73 oligochaetes, 69 molluscs, 13 leeches and 107 others (Reports of the Institute of Biology 1970– 2004). A total of 109 aquatic vascular plant species have been found in the river (Reports of the Institute of Biology 1970–2004). A total of 43 fish and lamprey species (41 native and 2 non-native species) are reported for the Western Dvina, among which Atlantic sturgeon is extinct. Thirty species are freshwater and seven are diadromous species. The following sources were used to obtain fish data for the Western Dvina: Mansfelds (1936); Prieditis (1950); Sloka (1956); Birzaks and Mitans (1999); Gaumiga (1982); Mitans (1973); Plikss & Aleksejevs (1998); Red Data Book of Latvia (2003) and The Fish Monitoring (2003). In addition, 10 amphibians, one reptile (N. natrix), and three water-living mammals (L. lutra, C. fiber and Arvicola terrestris) are reported from the Western Dvina. Nine fish are included in the 92/43/EEK, ANNEX II of the European Union. Abramis ballerus, Coregonus lavaretus, P. cultratus and S. glanis are included in the Latvian Red Data Book (2003). The amphibians T. cristatus Laurenti and P. fuscus are included in the Council Directive 92/43/EEC, ANNEX II. They are also included in the Red Data Book of Latvia (2003), together with Bufo viridis. Among mammals, L. lutra. and C. fiber. are included in the Council Directive 92/43/EEC, ANNEX II and L. lutra is also included in the Red Data Book of Latvia. Among vascular plants, 10 species (Alisma gramineum, Callitriche hermaphroditica, Catabrosa aquatica, Ceratophyllum submersum, Elatine hydropiper, Lemna gibba, Pilularia globulifera, Potamogeton rutilus, Potamogeton trichoides and Scirpus radicans are included in the Red Data Book of Latvia. The mussel U. crassus is included in the Council Directive 92/43/EEC, and also in the Red Data Book of Latvia. In addition, Lithoglyphus naticoides, Ancylus fluviatilis, Gyraulus crista, Myxas glutinosa, Musculium lacustre and Theodoxus fluviatilis are included in the Red Book of Latvia (1998). The Western Dvina has been colonized by non-native species. The main non-native fish is Carassius auratus (The Fish Monitoring 2003), and the most important nonnative vascular plant is E. canadensis. Among benthic invertebrates, several mysid shrimps (Limnomysis benedeni, Mesomysis kowalewskyi) as well as amphipods (P. robustoides, Chaetogammarus warpachowskii) and the zebra mussel (D. polymorpha) have been introduced to the Western Dvina (Reports of the Institute of Biology 1970–2004).

16.5.9. Human Impacts and Conservation

FIGURE 16.3 Long-term trend of ammonium in the Western Dvina River.

In Belarus, the river can be considered moderately polluted. In the middle and downstream sections, surface waters and groundwater are influenced by point pollution sources. The main sources are municipal and industrial wastewaters, storm water overflows, fish farms, landfills and large-scale farms (Daugava River Basin 2003). The point sources

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constitute 18–32% of the total pollution load. The remaining contribution is mainly from diffuse sources. The largest settlement in the Russian part of the basin is Nelidovo (28 000 inhabitants); in Belarus Vitsebsk (342 000), Navapolatsk (101 000) and Polatsk (79 000); in Latvia Daugavpils (110 000), Rezekne (37 000), Jekabpils (27 000), Ogre (26 000) and near the mouth the city of Rıga (732 000) (http://data.csb.lv). There are three major hydropower stations along the river, Rıga 35 km from the mouth, K ¸ eguma 70 km from the mouth and P¸lavi¸nu 107 km from the mouth (total storage ¸ eguma rescapacity: 1 km3, total surface area 101.9 km2). K ervoir, with an area of 24.8 km2 and a maximum capacity of 0.157 km3 was constructed before WWII in 1939. Since the WWII, P¸lavi¸nu reservoir (1967), with an area of 34.9 km2 and a full capacity of 0.51 km3 and Rıga reservoir (1974), with an area of 42.2 km2 and a full capacity of 0.339 km3 were constructed (Ziverts 1996). The natural dynamics in the lower Western Dvina has been notably changed by the operation of these hydropower dams. In Latvia, protected areas cover 2370 km2 of the Western Dvina basin. They include two nature reserves, five areas of protected landscapes, 13 nature parks, 89 nature reserves, parts of Gauja National Park, 27 dendrological plantations and 30 geological and geomorphological nature monuments. Internationally important bird areas, mainly wetlands, cover 93 km2 (0.3 % of the total basin area) (www.varam.gov.lv). According to the EU directive 2000/60/EC (WFD), the Western Dvina Project (2000–2003) elaborated a Management Plan for the river catchment. The objectives of the project were to develop a water management model in compliance with the EU requirements (Daugava river basin 2003).

PART | I Rivers of Europe

16.6. NARVA RIVER The 56 113 km2 large Narva basin (Narova in Russian) drains parts of Russia (50% of total catchment), Estonia (33%), Latvia and Belarus (small parts). It enters the Gulf of Finland in the eastern Baltic Sea. The catchment area has an elongate SSE to NNW shape. It extends from 56 N to 59 300 N and from 26 E to 30 E. The average annual discharge is 400 m3/s. It is the fourth largest river in the Baltic and Eastern central region, after the Vistula, Nemunas and Western Dvina. Lake Peipsi-Pihkva (Pskovsko-Cudskoe in Russian; area: 3555 km2, length: 140 km) splits the basin into two parts: the Velikaja River (the Large in Russian, 430 km long) upstream of the lake and the ‘proper’ Narva River (77 km long) downstream of the lake. The lake is called Peipsi in the following text. Thus, the maximum length of the river, including the lake, is approximately 650 km (Photo 16.5). The catchment of the Velikaja River (25 200 km2) covers approximately half of the whole basin, although its average annual discharge (38 km upstream of Lake Peipsi) is only 137 m3/s (34% of the total discharge). The large tributaries of the Velikaja are Sorot’ (right bank, 80 km), Sinjaja (left bank, 195 km), Utroja (left, 176 km) and Cereha (right, 145 km). The V~ohandu (162 km) and the Emaj~ogi (228 km with Lake V~ortsj€arv and upstream part) discharge into Lake Peipsi from the west and the Pljussa (285 km, basin area 6550 km2, mean discharge 50 m3/s) into Narva reservoir from the south. The Narva River is bifurcated at its mouth. A 26 km long branch (the Rosson River) connects the river with the Luga River (353 km, 14 373 km2) that discharges into Luga Bay in PHOTO 16.5 Narva River between Narva (left, Estonia) and Ivangorod (right, Russia) (Photo: Henn Timm).

Chapter | 16 Baltic and Eastern Continental Rivers

the Gulf of Finland (east of the Narva mouth). The flow direction in the Rosson branch depends on the water level and wind direction. The Narva catchment is entirely found in the Eastern Continental ecoregion and belongs to the East European Plain, mainly the Velikaja River–Lake Peipsi lowlands. The catchment is surrounded by the Rivers Luga, Selon’ and Lovat’ (the last two belong to the Neva catchment) in the east, the Western Dvina in the south and the Gauja and P€arnu in the west (Pihu & Raukas 1999).

16.6.1. Historical Perspective The shores of the fish-rich Lake Peipsi attracted humans as early as the Mesolithic period (8–5 kyr BC) (Miidel & Raukas 1999). During the Neolithic period (5000–2000 years BC), a typical comb-ceramics attributed to Finno-Ugric tribes was widely distributed in the basin. At the end of the 3rd millennium BC, tribes of a boat-axe culture (ancestors of contemporary Baltic tribes) that were familiar with animal husbandry and primitive tilling reached Estonia from the south. At the end of the 1st millennium BC, Slavonic people arrived at the southern and eastern shores of Lake Peipsi. The first urban-like settlements near Lake Peipsi were Tartu (on the Emaj~ ogi River to the west) and Pskov (Pihkva in Estonian), near the southernmost part of the lake. Between 1219 and 1227, Estonia west of Lake Peipsi was occupied and christianised by Germans. After the Livonian War (1554–1583), south Estonia was provisionally occupied by Polacks until the entire area was incorporated into the Swedish Kingdom in 1625. The Great Northern War (1700– 1725) ended the Swedish dominance and the entire area became under Russian influence. Contemporary Estonia achieved actual independence in 1920, but was again reincorporated into Russia (Soviet Union) in 1940. In 1991, Estonia was re-established as an independent state. The areas south and east of Lake Peipsi were partly part of the KievRussia state in 862 and of the Pskov Republic between 1348 and 1510. Afterwards, the area belonged to the Russian Empire and its successor, the Soviet Union (1922) and finally to the Russian Federation (1991). The Velikaja–Narva River is navigable from Pskov to Narva and from Narva to the Gulf of Finland. Although this navigation route has been interrupted in the lower reach (historically by waterfalls, today by a dam), the occurrence of large lakes (Peipsi, V~ ortsj€arv) has increased the importance of the system as an important waterway. The Emaj~ogi River is navigable from Lake V~ ortsj€arv to Lake Peipsi.

16.6.2. Physiography and Climate The river is within the eastern part of the Baltic Shield (East European lowland). It is a typical lowland river with a low relief (surrounding uplands are between 150 and 300 m asl) upland and a large uniform central plain (Velikaja–Lake Peipsi Lowland). The basin has been formed at an ancient

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bottom of an ice lake. The north catchment is covered by Vendian, Cambrian and Ordovician rocks. In the south, bedrock consists of Devonian rocks. Quaternary sediments cover the central basin and are >50 m thick. After the last glaciation, >7 kyr BP, the river broke through as the outflow of ancient Lake Peipsi and flowed into the Gulf of Finland (Miidel & Raukas 1999). The main valley (Velikaja–Lake Peipsi lowland) is surrounded by low-relief moraines that have been formed during major glaciations. The Luga uplands (maximum altitude 204 m asl) are in the east and the Latgale uplands (289 m asl) are along the southern margin of the drainage network of the Velikaja River. The Bezanitsy (339 m) and Sudomskaja (293 m) uplands are in the south catchment. In Estonia, the Pandivere uplands (166 m) are in the north and the Haanja (317 m) and Otep€a€a (217 m) uplands in the west (Pihu & Raukas 1999). These uplands receive higher precipitation and have longer snow cover than the lowland areas. The soils of the west catchment consist mostly of carbonate (in the north calcaric cambisols and luvisols, in the south stagnic luvisols and haplic podzols) and are gravelly, sandy, or peaty. Gleyzols, podzols and histosols occur near Lake Peipsi (Pihu & Raukas 1999). The basin is influenced both by marine and continental climate where the difference in mean air temperature between the warmest and coldest month is 25 C. The climate in the lower reach, near the city of Narva at the mouth of the river, is moderately cool with short summers. Mean annual precipitation (1966–1998) is 642 mm (Estonian Encyclopedia 11 2002). The mean annual air temperature at Narva is 5– 6 C, with a minimum of 6.5 C in January and a maximum of 16.5–17 C in July. Mean duration of snow cover is 124 days. About 70% of the annual precipitation evaporates (450–470 mm). The mean runoff ranges between 10 and 25 L/s/km2 in karstic mid-Estonia, and is as low as 4–6 L/ s/km2 in southeastern Estonia where deep water horizons are formed. The south basin is wet and moderately cold due to the influence of the Baltic Sea (Geography of Pskov Region 1996). Mean annual precipitation is 557 mm, of which 66% falls in summer (May–October). Snow appears in October– November and melts in April–May. Southern or southwestern winds prevail (National report on strategies 2003). Snow, rain and springwaters contribute equally to the total annual discharge of the river. However, groundwater dominates (50%) in karstic areas of Estonia while snowmelt water (40%) dominates north of Lake Peipsi. Upstream of Lake Peipsi, snow contributes >50% to the annual flow, while groundwater is most important in the headwaters of Velikaja and Alolja. Ice cover on Lake Peipsi lasts on average >100 days (from December to April). The duration of ice cover in the lower river is highly variable. Lakes (Lake Peipsi in particular) cover 7% of the catchment. The volume of Lake Peipsi is 25 km3 (about twice the annual runoff of the Narva River) (N~oges 2001). Due to the N–S orientation of the basin (380 km), and different temperature regimes in valleys and uplands, snowmelt lasts for an

630

extended period in spring. Hence, water supply to the lower Narva is relatively stable throughout the year. The river water level, upstream of Lake Peipsi, fluctuates on average by 1.5 m. The coastal area is flat and an even small increase in water level by 50 cm can cause intense coastal erosion.

16.6.3. Landscape and Land Use The basin belongs to the northern Atlantic moist mixed forest, a forest zone of the eastern Baltic geobotanical subprovince (Miidel & Raukas 1999). The north basin consists of up to 70% conifer and mixed forests. Further south, the forested area decreases to 30–40%, and the proportion of deciduous trees (birch and aspen) increases. Vast grasslands dominated by common reed and various sedges fringe the river and lakes. Sphagnum swamps are common in the north catchment, particularly around Lake Peipsi. The Velikaja basin consists of undulating hills with a mean altitude of 119 m asl, reaching 200–250 m in the upper and 30–50 m in the lower basin (National report on strategies 2003). Bedrock consists of Devonian limestone and sandstone covered by moraine sediments (up to 50–70 m thick in the upper basin). Mires cover only 2% of the basin. The upstream area is rich in lakes that cover 4% of the area. Land cover of the Narva basin in northern Estonia consists of 35% agricultural land, 50% forests, 6% wetlands, 7% waterbodies and 1% urban areas and mines (K. Pachel unpublished data). In the Estonian basin, agriculture is mainly restricted to the Pandivere uplands and areas around the city of Tartu. The southern region (upstream of Lake Peipsi) includes 30% forests and natural grasslands, up to 70% agricultural land and 2% wetlands (Miidel & Raukas 1999). Barley, wheat, potatos, rape, vegetables, milk and pork are the main agricultural products (Estonian Encyclopedia 11 2002).

16.6.4. Major Tributaries and Lakes The Velikaja drains an area of 25 200 km2. Its mean discharge is 132 m3/s (National report on strategies 2003). The Velikaja flows first for 25 km south, crosses 21 small lakes, turns west and then north before it flows into Lake Peipsi. The river forms a forked delta in the lake, fringed by floodplains. In the first 200 km, from its source to the town of Opocka, the main channel is 20–30 m wide, 1–1.5 m deep and water velocity averages 0.1–0.6 m/s (up to 1.7 m/s). Downstream of Opocka, the channel widens to 100–200 m and is 2–3 m deep. The delta starts 3 km upstream of Lake Peipsi. There, the channel is 200–300 m wide, 3–4 m deep, with mean water velocity 0.1–0.2 m/s. Large riffles mainly occur between Opocka (225 km upsteam of Lake Peipsi) and Pskov (33 km). Near Pskov, water depth in the river reaches 11 m. Larger tributaries of the Velikaja are Sorot’ (starts at Lake Mihalkinskoe, basin area: 3910 km2, length: 80 km), Sinjaja

PART | I Rivers of Europe

(starts at Lake Osveja, 2040 km2, 195 km), Utroja (starts in Latvia, 3000 km2, 176 km) and Cereha (3230 km2, 145 km). The average slope of the Velikaja (from its source to Lake Peipsi) is 0.2 m/km. The slope of the lower Narva River (downstream of Lake Peipsi) is 0.4 m/km. Downstream of Lake Peipsi, the natural channel of the Narva is 200–900 m wide and surrounded by floodplains and oxbow lakes. Between Permisk€ula and Kuningak€ ula (Rkm 585–590), large riffles occur. The fluctuating water level of the lake, as well as glacio-isostatic uplift, have induced meandering and sedimentation upstream of the rapids. Water depth is up to 5 m but reaches a maximum of 16 m near the city of Narva. Mean water velocity is 1 m/s (up to 3 m/s) and decreases to 0.5 m/s in the lower section (Loopmann 1979; Jaani 2000). Like all other north Estonian rivers, the Narva has a convex longitudinal profile because it must pass the Baltic Cliff that extends along the southern shore of the Gulf of Finland (Miidel & Raukas 1999). About 15 km upstream of the mouth, the Kreenholm Island divides a waterfall (western part: 3.5 m, eastern part: 6.5 m). Since 1956, the river has been dammed at this location, and a 3 km long reach, including the waterfalls, falls dry because water is directed through the hydropower plant into a new channel. The mean discharge of the river at the river mouth (1902– 2005) is 391 m3/s, corresponding to a total annual discharge of 12.3 km3. About 30% of the total discharge occurs in spring, 28% in summer, 22% in autumn and 20% in winter (O. Kovalenko and A. Reihan, unpublished data). Discharge has been recorded at the outlet of Lake Peipsi since 1902 (except 1918–1920 and 1944–1945). The gauging station is 77 km from the river mouth, and the catchment area at this site is 47 815 km2 (85% of the total area). There, the average annual discharge ranged between 161.3 m3/s (1973) and 603 m3/s (1924). The mean value for 1902–2005 at this gauging station was 331 m3/s. The lower Narva carries relatively clear water (on average 4 mg/L suspended solids). The sediment input to the Gulf of Finland is only 130 tons/day. Average maximum water temperature can be as high as 20 C in summer (July– September) but usually does not exceed 16–18 C (1992– 2005, U. Leisk, unpublished data). The hydrochemical characteristics near the city of Narva are (mean annual values): pH: 8, HCO3: 153 mg/L, SO4: 21 mg/L, Cl: 13 mg/L, Ca: 41 mg/L, Mg: 9.6 mg/L, Fe: 0.17 mg/L, NO3–N: 0.20 mgN/ L, NO2–N: 0.006 mgN/L, NH4–N: 0.075 mg/L, total N: 0.61 mgN/L, PO4–P: 0.029 mgP/L, total P: 0.055 mgP/L, BOD7: 2.18 mgO/L, CODMn: 11.1 mg/L, total hardness: 2.61 meq./L, oxygen saturation: 83%, conductivity: 292 mS/cm (according to U. Leisk, unpublished data). Water quality in the lower Narva has been monitored since 1992. No significant trend can be detected during the last 20 years. The total P concentration remained mostly below 0.08 mg/L indicating good to very good water quality, and total N concentration is <1 mg/L, also indicating good quality (Leisk & Loigu 2004). In Lake Peipsi, however, nutrient concentrations have increased during the last 30

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Chapter | 16 Baltic and Eastern Continental Rivers

years and this increase was most probably highest in the 1970s, when monitoring was lacking (Kangur et al. 2003). During unfavourable periods, that is, high temperature or low water levels, cyanobacteria blooms and fish kills occur in the lake. The Emaj~ ogi (Mother River in Estonian) is the largest western tributary of the Narva, with a mean discharge of 71 m3/s at its confluence (1922–2005, O. Kovalenko, unpublished data). Its southern main branch starts in the Otep€a€a Hills; it has a total length of 228 km and total relief 85 m. The longitudinal profile of the upstream part is typically concave (Miidel & Raukas 1999). The river flows first southwest and turns after 30 km northwards and flows into the shallow (mean depth 2.8 m) large (270 km2) eutrophic Lake V~ ortsj€arv. The mean channel width ranges from 10 m (upper part) to 65 m near the lake inlet. Mean water depth ranges between 1.2 and 4 m (Loopmann 1979). Mean annual discharge upstream of Lake V~ ortsj€arv is 8–10 m3/s. Downstream of the lake, a large left-bank tributary, Pedja River, joins the Emaj~ ogi before it flows eastward and finally flows into Lake Peipsi. Downstream of Lake V~ ortsj€arv, the water colour becomes greyish to greenish-yellow and transparency is low. Upstream of Lake Peipsi, large bogs drain into the Emaj~ ogi changing its colour to dark brown. Until 6000 BC, the lower Emaj~ ogi (between Lakes V~ ortsj€arv and Peipsi) served as the outflow from Lake Peipsi and flowed west. Today, the river has a gentle slope (0.037 m/km) and a low velocity (0.2 m/s), and it flows east. During peak flow in spring, the flow direction may again reverse between Lake V~ ortsj€arv and the Pedja River. The total annual discharge of Emaj~ ogi is 2.26 km3. Mean water depth varies between 1.4 and 11 m, and mean channel width ranges from 20 m (at the otflow of Lake V~ ortsj€arv) to 100 m (at the mouth). The water level fluctuates between 1 and 3 m (Riikoja 1956). Spring water contributes 36% to the total annual discharge, followed by summer (28%), autumn (22%) and winter (20%) (A. Reihan, unpublished data). Between Lake V~ ortsj€arv and Lake Peipsi over 50 oxbow lakes, covering a total area of 110 ha, exist. Both oxbows and bog lakes serve as important fish-spawning and bird habitats and are protected. The hydrochemical characteristics of the lower Emaj~ogi (upstream of Tartu in 1992–2005) are as follows (mean annual values): pH: 8; HCO3: 222 mg/L; SO4: 23.6 mg/L; Cl: 8.7 mg/ L; Ca: 63 mg/L; Mg: 17.2 mg/L; NO3–N: 1.04 mgN/L; NO2– N: 0.007 mgN/L; Ntotal: 1.90 mgN/L; PO4–P: 0.016 mgP/L; total P: 0.056 mgP/L; Fe: 0.45 mg/L; BOD7: 2.86 mgO/L; CODMn: 13.0 mg/L; NH4–N: 0.124 mgN/L. Total hardness was 4.52 mg-eq./L, oxygen saturation 86% and conductivity 393 mS/cm (U. Leisk unpublished data). The Emaj~ogi has a similar pH and total P, but a higher alkalinity, conductivity, BOD7 values and higher nitrate, NH4–N and total N concentrations than the lower Narva. The entire Narva basin contains more than 3000 lakes, of which 2500 are in the Velikaja catchment. Lake Peipsi (3555 km2) is the 4th largest lake and largest hard-water

eutrophic lake in Europe. The northern Lake Peipsi area is mesotrophic while the southern part (called Lake Pihkva, Pskovskoe in Russian) is highly eutrophic. Velikaja is the main tributary to Lake Peipsi and contributes about 33% to the total inflow. The average water level of the lake is 30 m asl (Miidel & Raukas 1999). After the whole basin became isolated from the proglacial Baltic Ice Lake (in the present Gulf of Finland), its southern part fell dry in the Younger Dryas. At the end of the Pre-Boreal, the lake level was >10 m lower than today. As a consequence, the Velikaja River and its tributaries flowed directly into the larger northern part of contemporary Lake Peipsi. The subsequent rise in water level was mainly caused by glacio-isostatic uplifts, which was faster in the north than in the south. At present, the lake continues to expand southward. The northern part of the depression is rising at a rate of 0.2–0.4 mm/year, whereas the southern part is sinking at a rate of 0.8 mm/year. Large areas surrounding the lake have become swamps. Along the northern shore, the water level remains more or less stable due to rocky outcrops at the outflow of Lake Peipsi (lower Narva). During the last 7000 years, the water level has increased by 50– 60 cm per 100 years (Miidel & Raukas 1999). Lake V~ortsj€arv (270 km2) is a shallow, eutrophic, unstratified hardwater lake (mean depth <3 m). Low water depth and resuspension of bottom sediments by waves lead to a high turbidity during summer.

16.6.5. Biodiversity 16.6.5.1 Phyto- and Zooplankton A total of 337 phytoplankton species, including 120 chlorophytes, 80 diatoms and 55 blue-green algae were identified from the Velikaja River (Mel’nik unpublished data). Ristkok (1994) noted 44 blue-green algae species, 14 diatoms and 9 other planktic algae from the Emaj~ogi River. Tiny flagellates (Cryptomonas and Rhodomonas) dominated in the spring phytoplankton bloom in the Narva and Emaj~ogi Rivers (Tuvikene et al. 2005). The centric diatom Stephanodiscus cf. neoastraea dominated in summer and the blue-green A. flos-aquae in autumn. Phytoplankton biomass decreased downstream, of Lake Peipsi. Based on chlorophyll a concentrations, the lower Narva can be classified as mesotrophic. The influence of Lake V~ortsj€arv on the Emaj~ogi was shown by a dominance of the lake-dwelling blue-green algae Limnothrix planktonica during summer and autumn (Tuvikene et al. 2005). More than 500 algae taxa were identified in Lake V~ortsj€arv (Haberman et al. 2004). Filamentous cyanobacteria (L. planktonica, L. redekei) dominated. In the southern part of the lake where the main river enters, diatoms predominated during the entire year. Lake Peipsi harbours 1000 algae species and common eutrophic species dominate (Pihu & Haberman 2001). The oligo-mesotrophic Aulacoseira islandica is characteristic during the cool

632

period. Gloeotrichia echinulata, Anabaena spp. and A. flos-aquae cause algal blooms in summer. Since 1909, no major change in the dominant species composition was observed. Seasonally, three phytoplankton maxima occurred in the northern part and between one and two maxima in the southern part of the lake. The mean chlorophyll a content is 17.6 mg/m3, indicating meso- to eutrophic conditions in the northern part and eutrophic to hypertrophic conditions in the southern part of the lake. In contrast to the lake, the Narva reservoir is poor in phytoplankton due to a rich macrophyte vegetation and the fast turnover of its water (>30 times per year) (Kangur et al. 2002). Phytobenthos was primarily studied in the headwaters. A total of 133 diatoms was identified in Emaj~ ogi, and 81 taxa in the Pedja and P~ oltsamaa tributaries (Estonian Rivers 2001). Achnanthidium minutissimum was the most common diatom. In the Velikaja River, 107 species of zooplankton were recorded. Upstream sections were most species rich (101 taxa). Among Cladocera, D. cucullata, Daphnia longispina, Chydorus sphaericus, Bosmina longirostris; among Copepoda, Mesocyclops oithonoides, Mesocyclops leuckarti and Eudiaptomus graciloides; and among Rotatoria, Asplanchna priodonta, K. cochlearis and Keratella quadrata prevailed (Mel’nik unpublished data). Ristkok (1994) recorded 178 rotifers, 84 cladocerans and 42 copepods in the Emaj~ogi basin. In Lake Peipsi, 290 zooplankton taxa including 181 rotifers, 57 cladocerans, 28 copepods and 23 ciliates were observed (Pihu & Haberman 2001). Species typical for oligo-mesotrophic waters (e.g. Conochilus hippocrepis, C. unicornis, Kellicottia longispina, Bosmina berolinensis) as well as for eutrophic waters (K. cochlearis, D. cucullata, B. coregoni) occur. Holopedium gibberum, an indicator of oligo-mesotrophic conditions and listed in the Estonian Red Data List (Estonian Red Data Book (1998)) occurred between 1909 and 1964, but disappeared afterwards. In summer, zooplankton biomass averaged 3.0 g/m3. Zooplankton of eutrophic Lake V~ ortsj€arv consists of at least 268 taxa (172 rotifers, 47 Cladocerans, 14 Copepods, 34 protists). Several species have disappeared, mainly due to eutrophication. At the same time, species typical for eutrophic waters (Anuraeopsis fissa, Keratella tecta, Trichocerca rousseleti) have increased in number. The mean average biomass is only 0.9 g/m3 (Haberman et al. 2004). The Narva reservoir is species poor and small rotifers dominate (Kangur et al. 2002).

16.6.5.2 Macrophytes A total of 86 higher plant species have been recorded in the Velikaja River. In the tributaries, higher numbers (40–50) were found in slow flowing sections fringed by wide floodplains (e.g. Issa, Sinjaja, Cereha). There were fewer species (up to 30) in upstream fast-flowing areas (Mel’nik unpublished data). Timm (1967) studied the macrophytes of the lower Narva. At the outlet of Lake Peipsi, Sparganium sp.,

PART | I Rivers of Europe

Equisetum limosum, S. sagittifolia, P. lucens and Batrachium sp. dominated. In the middle course, P. perfoliatus and B. umbellatus prevailed. Slow-flowing downstream reaches were species rich with S. sagittifolia, B. umbellatus, Lemna sp., P. perfoliatus, Nuphar lutea, Cladophora sp., P. lucens, S. lacustris, Lemna trisulca and Sparganium sp. being most abundant. According to Ristkok (1994), 51 higher water plant species and 9 macroalgae species were recorded for the Emaj~ogi. The most widespread species in its lower part were Phragmites australis, Glyceria maxima, B. umbellatus, Sparganium erectum, S. lacustris. Typhoides arundinacea and P. australis often form dense belts. Occasionally, Salix bushes co-occur or have replaced reed. S. sagittifolia was the most common species along the entire river, followed by P. perfoliatus, P. pectinatus and N. lutea (T. Trei unpublished data). For Lake Peipsi, more than 100 taxa have been recorded. At the end of the 1980s, macrophytes occupied 3–4% of the northern lake and 7–8% of the southern part. P. perfoliatus, P. australis and S. lacustris were the predominant species. In the late 1980s, a marked decrease in species diversity and an expansion of emergent plants, particularly of reed, were observed (Pihu & Raukas 1999). In Lake V~ortsj€arv, 114 macrophyte species occupied 19% of the lake area in 1997. Their distribution was constrained by strong wind and wave actions. M. spicatum was the most dominat species. Anthropogenic activities have led to an expansion of reeds and M. spicatum and a decline of charophytes (Haberman et al. 2004). In the upper Emaj~ogi River, 40 macrophytes were found, among them N. lutea, Equisetum fluviatile and Sparganium sp. prevailed. In the Pedja River, 42 species (among them Myosotis scopioides, S. lacustris, N. lutea, T. arundinacea) and in the P~oltsamaa River 38 species (N. lutea, S. erectum, T. arundinacea, Rorippa amphibia, Alisma plantago-aquatica, G. maxima, S. lacustris) were recorded (Estonian Rivers 2001). The Estonian Red Data List includes the following species listed from the Emaj~ogi-Narva River: Subularia aquatica, E. hydropiper, Najas flexilis, A. gramineum, Sparganium angustifolium, S. gramineum and Isoetes lacustris.

16.6.5.3 Benthic Invertebrates In the Velikaja River, 228 species of macrozoobenthos were found. Among them, chironomids are most species rich (Ablabesmyia lentiginosa, Chironomus plumosus, Cryptochironomus gr. defectus, Einfeldia carbonaria and Procladius choreus being common). Among oligochaetes, L. hoffmeisteri and Potamothrix hammoniensis prevail. Large mussels such as Anodonta and Unio are common (Mel’nik, unpublished data). Timm (1967) studied the macrozoobenthos along four transects in the lower Narva in 1962. Just below Lake Peipsi, chironomids dominated in number and molluscs (D. polymorpha, Planorbis sp., Pisidium sp.) in biomass. Between Lake Peipsi and Narva reservoir, chironomids, oligochaetes and Molanna angustata prevailed both

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Chapter | 16 Baltic and Eastern Continental Rivers

in abundance and biomass. Downstream of the city of Narva, oligochaetes (Tubifex newaensis, Potamothrix moldaviensis) were most numerous and molluscs (Viviparus viviparus, U. crassus, D. polymorpha) were most important in biomass. In the lower river, T. newaensis prevailed both in total abundance and biomass. In October 2006, zoobenthos of the lower Narva was restudied near the same stations as in 1962. Immediately downstream of Lake Peipsi, Hydropsyche contubernalis and D. polymorpha dominated. Between Lake Peipsi and Narva reservoir, chironomids and Radix ovata prevailed. Downstream of the city of Narva, Unio tumidus dominated in biomass while all other animals were rather rare. Finally, near the river mouth, T. newaensis and V. viviparus had the highest abundance and biomass, respectively. According to Ristkok (1994), 504 species of true waterdwelling macroinvertebrates were found in the Emaj~ogi and its tributaries. Common oligochaetes were P. hammoniensis, L. hoffmeisteri, L. claparedeanus, Spirosperma ferox and T. tubifex; leeches included Glossiphonia complanata, Erpobdella octoculata and Piscicola geometra and molluscs were dominated by D. polymorpha, Sphaerium corneum and Unio pictorum. In the upper Emaj~ ogi and tributaries of the lower Emaj~ ogi, 171 macroinvertebrates (ostracods included, chironomids excluded) were found (Estonian Rivers 2001). At least 421 macrozoobenthos taxa occur in Lake Peipsi (Pihu & Haberman 2001). C. plumosus and P. hammoniensis dominated in the profundal and D. polymorpha in the sublittoral. Between 1964 and 1998, the mean abundance of macrozoobenthos in the lake was 2671 individuals/m2 and the mean biomass was 12.9 g/m2 (excluding large molluscs). The average number of molluscs was 312 individuals/m2 and biomass was 244 g/m2. In the shallow littoral, the non-native amphipod Gmelinoides fasciatus dominated, while caddisflies H. contubernalis, Ecnomus tenellus and Athripsodes cinereus were also common. The mean abundance of macrozoobenthos in Lake V~ ortsj€arv (1973–2001) was 818 individuals/m2 and mean biomass was 6.6 g/m2 (Timm 1973; Haberman et al. 2004). C. plumosus formed 73% of the mean total biomass (excluding Unionidae). In the profundal, P. hammoniensis was abundant. The stony littoral was dominated by Gammarus lacustris and several caddisflies. In addition, Psychomyia pusilla was common. The sandy bottom was dominated by unionids (Anodonta anatina, U. tumidus, U. pictorum) (Timm, unpublished data). In Narva reservoir, D. polymorpha and G. lacustris prevailed before the 1970s (T~olp 1969). More recently, the gammarid (G. fasciatus) became the dominant macrobenthic species (Kangur et al. 2002). Estonian Red Data Book (1998) includes the following invertebrate species that inhabit the catchment of the Narva River: the snails Anisus vorticulus, Bithynia leachii and M. glutinosa, the mussels U. crassus and Pseudanodonta complanata, the gammarid Pallasea quadrispinosa, the mayfly Polymitarcys virgo, the odonates Cordulegaster boltoni, Epitheca bimaculata, Libellula fulva, Onychogomphus for-

cipatus, Ophiogomphus cecilia, Aeshna viridis and Sympecma paedisca, the water beetles Graphoderus bilineatus, Oreodytes rivalis and Dytiscus latissimus, the caddisflies Odontocerum albicorne and Semblis phalaenoides and the chironomid Corynocera ambigua.

16.6.5.4 Vertebrates 16.6.5.4.1 Fish The Narva River is open to migrating fishes for only the first 14 km, downstream of a natural escarpment and a hydroelectric dam. A total of 39 native fish species and two lamprey species have been registered for the whole basin (Mikelsaar 1984). A. bipunctatus inhabits some tributaries. Common non-native species that do not reproduce naturally (Coregonus peled, O. mykiss) are not included. Historically, the lower Narva has been the spawning area for several anadromous fishes, such as salmon, the migrating form of brown trout, vimba bream, smelt and most probably sturgeon. Today, only lamprey have commercial importance among the migrating fishes and the salmon population is stocked and sparse. According to Ristkok (1994), 34 native fish and lamprey species and also three non-native species (C. peled, C. carpio, O. mykiss) were found in the Emaj~ogi and its tributaries. In Lake Peipsi (Pihu & Haberman 2001), 33 fish and one lamprey were recorded. Main commercial fishes are smelt, perch, pikeperch, roach, bream, pike and until the 1990s also vendace. Annual fish catches are 25–31 kg/ha. Today, the lake is a smelt–bream–pikeperch waterbody. Lake V~ ortsj€arv is permanently inhabited by 31 fish and one lamprey species (Haberman et al. 2004). The lake belongs to the pikeperchbream type. Bream, pikeperch, eel and pike are the main commercial fishes. Eel elvers (Anguilla anguilla) that cannot cross the dam in the lower Narva were introduced into the lake (44 million between 1956 and 2001). The Estonian Red Data List (1998) includes A. sturio, C. lavaretus maraenoides, S. glanis, Thymallus thymallus, Salmo trutta trutta, A. bipunctatus, Coregonus albula, C. gobio, Lampetra planeri, Osmerus eperlanus, A. aspius, C. taenia and M. fossilis. Fauna of the upper Velikaja and its tributaries is similar to other sections within the basin. C. auratus has formed selfbreeding populations in upstream lakes. Specimens of O. mykiss, C. peled and also Aristichthus nobilis, H. molitrix and C. idella escaped from artificial fisheries and can be sampled in the streams. 16.6.5.4.2 Amphibians Around Lake Peipsi, nine amphibians are found, among them warty newt, common spadefoot, green toad and marsh frog are rare, while smooth newt, common toad, common frog, moor frog and edible frog are abundant. Near Lake V~ortsj€arv, Rana lessonae was also found. B. viridis, T. cristatus, P. fuscus and R. ridibunda belong to the Estonian Red Data List.

634

16.6.5.4.3 Birds Lake Peipsi is on the East Atlantic migration route for arctic waterfowl. The lake shores and main tributaries are important autumn resting areas for Bewicks swans, whooper swans, bean goose, white-fronted goose and goldeneye. Divers, tufted duck, scaup, long-tailed duck, velvet scoter and common scoter are important waterfowl. Among passerine species, the most numerous are chaffinch, brambling, starling, linnet, siskin and redpoll (Pihu & Raukas 1999). 16.6.5.4.4 Mammals American mink have entirely destroyed the population of European mink, and almost the population of another nonnative species, the muskrat (that was introduced into Estonia in 1947). In the 1950s, beaver was reintroduced in the basin of Lake Peipsi and is now widespread.

16.6.6. Human Impacts and Special Features 16.6.6.1 Pollution The Narva is influenced by urban, agricultural and oil shale mining activities, as well as by the introduction of non-native species. Amelioration of tributaries and damming have also significant by impacted the river. The largest settlements in the catchment are Pskov (Pihkva in Estonian) upstream of Lake Peipsi (200 000 inhabitants), Tartu along the lower Emaj~ ogi (100 000 inhabitants) and Narva and Ivangorod along the lower Narva (combined 80 000 inhabitants). According to Stalnacke et al. (2001), Estonian rivers transport 240 tons/year P and 6500 tons/year N into Lake Peipsi. The Russian rivers transport 670 tons/year P and 14 040 tons/year N. Agriculture contributes most to N and P loads, followed by point sources (urban areas). Phosphorus and nitrogen loads decreased between 1980 and 2000. Tartu, on the lower Emaj~ogi, discharged its unpurified wastewaters into the river until 1999, although almost 100% of the wastewater has been treated since 2003. In 2002, the mean BOD7 in the Emaj~ ogi was 2.6 mgO2/L upstream and 2.8 mgO2/L downstream of Tartu, indicating high quality. Total P was 0.042 mgP/L upstream and 0.082 mgP/L downstream of Tartu. NO3–N decreased from 1.24 to 0.74 mg NO3–N since 2003. Phosphate concentrations are still higher than desired. Concentrations of heavy metals were very low in the water and bottom sediments in 2001. According to older records (Riikoja 1956; T~ olp 1956), macrozoobenthos of the Narva at Tartu was typical for a polluted river, being inhabited by C. plumosus, Asellus and Eristalis taxa. The biological status of the lower Emaj~ogi River, based on macroinvertebrates, was evaluated from 1998 to 2002 (H. Timm, unpublished data). According to the British ASPT-index, water quality was significantly lower downstream than upstream of Tartu. However, in 2002 sensitive species such as T. fluviatilis, Aphelocheirus aestivalis, Brachycentrus subnubilus were again found down-

PART | I Rivers of Europe

stream of Tartu, probably indicating the efficiency of wastewater purification. Kangur et al. (2002) observed relatively low total N (0.38– 0.79 mgN/L) and total P (0.02–0.078 mgP/L) concentrations in Narva reservoir. The city of Narva (on the Estonian side) and the city of Ivangorod (on the Russian side) are just downstream of the outlet of Narva reservoir, 19–13 km upstream from the Baltic Sea. Ammonium (0.04 mgN/L near outflow from Lake Peipsi, 0.075 mgN/L downstream of cities) and total P (0.038 mgP/L near outlet of Lake Peipsi, 0.055 mgP/ L downstream of cities) concentrations are much higher downstream of the two cities. In addition to wastewaters derived from the two cities, two large electrical power plants discharge into Narva reservoir. They bring water from ashwater sedimentation ponds having a pH of 12–13 and a water temperature 4 C higher than the upstream river (U. Leisk, unpublished data). The average annual pH is similar in the Narva and Lake Peipsi (pH: 8.0). The difference in water temperature was also probably neutralized in the reservoir. The transport channels from the mines and power plants support a rich fish fauna and have been used for fish farming. According to Tuvikene et al. (2005), nutrient concentrations in the Emaj~ogi are higher than in the Narva. Nitraterich groundwaters that enter via the Pedja River from the Pandivere Upland create high N concentrations in the Emaj~ogi during spring. Nutrient concentrations in the lower river remained relatively constant between 1990 and 2006.

16.6.6.2 Dams A 9 m high dam of a hydroelectrical power plant was constructed in 1956–1957, 18 km upstream of the mouth of the Narva River. As a consequence, the old channel, with its 6.5 m high natural waterfall as well as important spawning areas for salmonids, was destroyed. Moreover, a regulated flow regime (hydropeaking) caused by the plant operation makes spawning by remaining fishes ineffective. Eel elvers that were able to climb the natural barrier are not able to pass the new dam. Numerous smaller dams have been constructed along the tributaries, although their number was much higher 100 years ago.

16.6.6.3 Non-native species The first occurrence of zebra mussel (D. polymorpha) in Lake Peipsi was reported before WWII (Pihu & Haberman 2001). Today, D. polymorpha has the highest biomass of all species in the lake, particularly in the 3–8 m deep sublittoral (Pihu & Raukas 1999). Its density in offshore areas (1985– 1988) was 864 individuals/m2 and its biomass 687 g/m2. In the sublittoral, density reached 1200 individuals/m2 and biomass 900 g/m2. The biomass of zebra mussel exceeds the biomass of all other invertebrates, zooplankton and fishes combined. The zebra mussel is also very abundant in the Narva River between Lake Peipsi and Narva reservoir. It

635

Chapter | 16 Baltic and Eastern Continental Rivers

occurs in Lake V~ ortsj€arv and the Emaj~ ogi River, but is less abundant. The freshwater gammarid (Gmelinoides fasciatus) was introduced in Lake Peipsi from a Siberian population (Panov et al. 2000). It was first found in 1972 and established itself successfully in the littoral zone by 1990, replacing the native population of Gammarus lacustris. In 2004–2005, G. fasciatus formed at least 70% of the total abundance of macroinvertebrates in the shallow littoral of the lake (H. Timm, unpublished data). It is also a common species in the lower Narva between Lake Peipsi and the reservoir, and in the lower Emaj~ ogi up to the city of Tartu. G. fasciatus is also found in the lower Velikaja, upstream of the mouth of the Sinjaja River. In the lowermost stretch of the Narva River, two abundant non-native crustaceans, Paramysis intermedia and Chelicorophium curvispinum were observed in 2007 (H. Timm unpublished data). After building the hydroelectrical dam near the city of Narva, young eels are regularly introduced into Lake V~ ortsj€arv. The Amur sleeper (P. glenii) was recently observed in the cooling waters of the Narva thermoelectric station (J€arvek€ ulg & Tambets 2005) and near Pskov.

16.6.6.4 Nature Protection In Estonia, Alam-Pedja and Emaj~ oe-Suursoo, protection areas include the main channel of the Emaj~ ogi River with oxbow lakes and large bogs. The protection areas of Otep€a€a, Haanja, Karula, Puhatu, Agusalu and Muraka comprise some tributaries and fringing mires (Estonian Encyclopedia 11 2002; Pihu & Haberman 2001). Lake V~ ortsj€arv and Lake Peipsi are important bird migration areas and some parts in Lake Peipsi are important whitefish and vendace spawning habitats. In Russia, 19 sites of conservation interest (SCI) are located within the Narva basin. They include two federal sites of conservation interest (Sebezsky and Remdovsky reserves).

Acknowledgements For the Vistula, the authors thank Klement Tockner for editorial help and to Wiesław Wisniewolski, Andrzej Witkowski, Jan Bocian, Zbigniew Kaczkowski, Mirosław Przybylski, Piotr D˛e bowski, Jan Kotusz, Krzysztof Kukuła, and Grzegorz Zi˛e ba (co-workers and experts of FAME project – Development, Evaluation and Implementation of a Standardized Fish-based Assessment Method for the Ecological Status of European Rivers for their inputs. A Contribution to the Water Framework Directive. Contract no.: EVK1-CT-2001–00094) for support with fish and environmental data, and to Roman Kujawa for the photograph of the Vistula River. For the Western Dvina, the authors thank all members of the Laboratory of Hydrobiology and Laboratory of Botany of the Institute of Biology, University of Latvia, who conducted the River Daugava studies. Further, we thank

the Latvian Fish Resources Agency for the possibility to use fish monitoring data. For the Narva River, we thank the Pskov Department of the Federal Governmental Scientific Enterprise ‘State Research Institute for Lake and River Fisheries’ (GosNIORKh) for the Velikaja River data, Ulle Leisk (Tallinn Technical University) for hydrochemical data, Alvina Reihan (Tallinn Technical University), Mari Sepp and Olga Kovalenko (Estonian Hydrometeorological Institute) for discharge data, Karin Pachel (Estonian Environment Information Centre) for land use and pollution data, and Tiiu Trei (Estonian University of Life Sciences) for macrovegetation data. The work was also supported by two research projects of the Estonian University of Life Sciences: SF 0170011508 and SF0170006s08.

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FURTHER READING Resources of surface waters in S.S.S.R 1972. T. 4, vyp. I: Estonija, Leningrad (in Russian). Virbickas, J., and VirbickasT. 1996. Fish stock in lakes and reservoirs of Lithuania. Zuvininkyste Lietuvoje II, 253–258. “Petro ofsetas”, Vilnius (in Lithuanian).

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RELEVANT WEBSITES http://aaa.am.lt : Lithuanian environmental protection agency. http://aaa.am.lt/VI/files/0.356876001144137886.xls : Lithuanian environmental protection agency. http://earthtrends.wri.org/ : Water Resources eAtlas, Watersheds of Europe, E27 Vistula. http://pan.cultland.org/ : European Thematic Network on Cultural Landscapes and their Ecosystems. http://www.nobanis.org/ : North European and Baltic Network on Invasive Alien Species (NOBANIS). http://www.atlas-roslin.pl/ : Atlas roslin naczyniowych Polski (Vascular plants of Poland photoflora). http://www.aquadocinter.org : International Portal for Water Managers. http://www.eea.europa.eu : European Environmental Agency. http://www.imgw.pl/internet/otkz/zapory/pl/ : Institute of Meteorology and Water Management (IMGW).Dams Monitoring Centre (OTKZ). http://www.mos.gov.pl/ : official site of Ministry of Environment RP. http://www.mos.gov.pl/natura2000/ : European Ecological Network NATURA 2000, official site of Ministry of Environment RP. http://www.pgi.gov.pl/ : Polish Geological Institute home page. http://www.ramsar.org/ : The Ramsar Convention on Wetlands. http://www.worldwildlife.org/science/ecoregions/biomes.cfm : Conservation Science, Biomes and Biogeographical Realms.WWF. http://www.unesco.org/mab/ : UNESCO MAB Convention on Biological Diversity.

PART | I Rivers of Europe

http://www.fao.org/ : Food and Agriculture Organization of the United Nations. http://www.limnos.ee/index.php?alam=2 : Estonian University of Life Sciences, Institute of Agricultural and Environmental Sciences, Centre for Limnology. http://www.keskkonnainfo.ee/english : Estonian Environment Information Centre. http://www.envir.ee/index.aw/set_lang_id=2 : Estonian Ministry of the Environment, Water Department. http://www.stat.gov.pl/gus/ : The Central Statistical Office of Poland. http://www.kzgw.gov.pl/ : Country Water Management Board. http://www.rzgw.gliwice.pl/ : Regional Office of Water Management in Gliwice. http://www.krakow.rzgw.gov.pl/. : Regional Water Management Board in Cracow. http://www.rzgw.warszawa.pl/. : Regional Water Management Board in Warsaw. http://www.rzgw.gda.pl/ : Regional Water Management Board in Gdansk. http://www.gios.gov.pl/ : Main Inspectorate of Environmental Protection. http://www.gios.gov.pl/ : Main Inspectorate of Environmental Protection. http://www.wios.lublin.pl/ : Voivodeship Inspectorate of Environmental Protection in Lublin (Report 2005). http://www.wios.warszawa.pl/ : Voivodeship Inspectorate of Environmental Protection in Warsaw (Report 2006). http://www.gios.gov.pl/ : Main Inspectorate of Environmental Protection. http://www.wikipedia.pl : the free encyclopedia on-line.

Chapter 17

Rivers of Turkey Nuray (Emir) Akbulut

Serdar Bayarı

Aydın Akbulut

Hacettepe University, Faculty of Science, Department of Biology, 06532 Beytepe, Ankara, Turkey

Hacettepe University, Faculty of Engineering, Hydrogeological Engineering Section, 06532 Beytepe, Ankara, Turkey

Gazi University, Faculty of Science and Arts, Department of Biology, 06500 Be¸sevler, Ankara, Turkey

Yal¸cın S ¸ ahin Eski¸sehir Osman Gazi University, Faculty of Science and Arts, Department of Biology, 26480 Me¸selik, Eski¸sehir, Turkey

17.1. 17.2. 17.3. 17.4. 17.5. 17.6. 17.7. 17.8. 17.9. 17.10. 17.11.

Introduction Historical Perspective Geology of Turkey General Characterization of Turkish Rivers Climate Land Use Patterns Geomorphology of River Basins Hydrology and Temperature Water Quality Biodiversity Management and Conservation Acknowledgements References

rises from west to east. Anatolia is fringed by the Pontid Mountains along the Black Sea and the Taurid Mountains along the Mediterranean Sea. In eastern Anatolia, the two mountain ranges converge and form the eastern highlands, called Anti-Taurus. Mount Agrı (also known as Ararat) is Turkey’s highest peak at 5165 m asl. The mountain ranges comprise the vast Central Anatolian Plateau (1200 m asl), a rugged land of flat hills, plains and steppes. The plateau includes two major endorheic basins, the Konya basin (Konya Ovası) and the Great Salt Lake basin (Tuz G€ ol€ u). Lake Van (area: 3755 km2) is the largest lake at 1550 m asl on the eastern edge of the Anatolian plain. It drains an endorheic basin. South of Anti-Taurus, a plateau extends towards the Syrian border, and the elevation decreases from about 800 to 500 m asl.

17.1. INTRODUCTION Turkey (26–45 E, 36–42 N) is a transcontinental country encompassing an area of 784 000 km2. About 97% of the country is in Asia Minor (Anatolia) and 3% in Europe (Thrace). The population was 68 million in 2000, corresponding to a density of 87 ind/km2. The current population growth rate is 1.4% (http://nkg.die.gov.tr; Turkey’s Statistical year book 2005). Istanbul (10 million people), Ankara (3.5 million), Izmir (2.5 million), Bursa (1.4 million), Adana (1.2 million) and Gaziantep (1.1 million) form the largest urban areas. Today, about 66% of the Turkish population lives in cities. Turkey is surrounded by the Mediterranean, Aegean, Marmara and Black Seas, with a total coastal length of 10 765 km. The mean altitude of Turkey is 1130 m asl, compared to 330 m asl in Europe. While the European part constitutes a relatively mature low-lying fertile land, Anatolia Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

17.2. HISTORICAL PERSPECTIVE For thousands of years, Turkey has served as the cultural ‘bridge’ and melting pot of the European, Asian and African continents. It has been subject to human migration and settlement throughout its long history. In Anatolia, early human occupation can be traced back to 50 000 BC (Karain Cave near Antalya). Farming appeared about 11 000 years ago in Central Anatolia, and then in Greece some 8000 years ago. Around 500 years later, farming villages were founded in the Balkans and Central Europe (Balter 2004). Around 10 000 years BP, Catalh€ ¸ oy€uk, in the Konya basin, was the largest Neolithic settlement in Central Anatolia and is the world’s oldest farming community yet discovered (Ergener 2002). Wild ancestors of the seven ‘founder crops’ harvested by the world’s first farmers have all been traced to southeastern Turkey and northern Syria. The settlement of Catalh€ ¸ oy€ uk, 643

644

with a population of 10 000 people, is considered the major source of Indo-European speaking people. The Kurgans, nomadic warriors that lived on the steppes north of the Black Sea, were an important second source. The availability of vast land areas and water resources at that time favoured the formation of various tribes. Water resource projects such as spring capturing, aquaduct construction, dam building and the establishment of an irrigation network began as early as 2000 BC and continued during the eastern Roman Empire. Ancestors of the present Turkish nation were nomadic tribes that became organized in Central Asia in the 4th century (Mc Carthy & Mc Carthy 2003). After migrating to Anatolia in the 10th century, several large Turkish states scattered throughout the country established the Ottoman Empire in the 12th century. The largest water resource development project during the Ottoman period was probably the draining of Bey¸sehir Lake for agriculture in the Central Anatolian Konya plain by a 210 km canal. Hydraulic developments in Turkey date back to the Hittites, Urartus, Greeks and Romans. Later, the Seljuks and Ottomans constructed fountains, cisterns and irrigation and diversion structures. Seven dams constructed between the 17th and 19th century near Istanbul for drinking water were highly important developments. Water resource regulation and development began with the foundation of modern Turkey in 1923. In 1936, the large Cubuk-1 ¸ dam was built to supply water for the city of Ankara. In 1953, the State Water Works (DSI), modelled after the USA Bureau of Reclamation, was founded (www. dsi.gov.tr). Today, the DSI employs 25 000 people of whom 5000 are engineers and technicians. Since the beginning of the Turkish Republic, 544 large dams (>15 m) including the Atat€ urk (817 km2), Keban 2 2 (675 km ), Karakaya (268 km ) and Hirfanlı (263 km2) have been built. In 1995, the hydropower capacity in Turkey was 9900 MW, corresponding to 30% of the total hydropower potential. The southeastern Anatolia Development Project (GAP using Turkish initials) is the largest project undertaken by Turkey and one of the largest in the world. The project began in the 1950s with the construction of the Keban dam in the upper Euphrates River. Between 1980 and 1986, the Turkish government established GAP as the primary regional development program in the country that included 13 major projects, primarily for irrigation and hydropower generation. The project envisions the construction of 22 dams and 19 hydroelectric power plants on the Euphrates and Tigris Rivers and their tributaries. The project plans to develop the longignored southeastern Turkey with its large population and high levels of unemployment and political instability. The project also has major conflict potential both locally through the resettlement of people, destruction of historic sites and environmental and social impacts and internationally through the sharing of water resources with Iraq and Syria. Turkey, the southeast in particular, is an internationally known biodiversity hotspot.

PART | I Rivers of Europe

17.3. GEOLOGY OF TURKEY Turkey mostly consists of a mosaic of agglomerated geologic units that once formed the paleo-ocean Tethys. Turkey is one of the most tectonically active regions in the world with a long history of major earthquakes. The continental collision between the African and Eurasian plates resulted in complex deformations of the ‘Mediterranean Earthquake Belt’, including Turkey. Both paleotectonic and neotectonic phases are responsible for the tectonic evolution of Turkey. Since the late Tertiary, compressional and extensional tectonic stresses have resulted in the uplift of Anatolia by >2500 m in the west and >4000 m in the east, and enclosing the Central Plateau at 1200 m asl (Figure 17.1). Geologically, Turkey is part of the Alpine belt that extends from the Atlantic Ocean to the Himalayan Mountains. This belt started to form in the early Tertiary (65 million years ago) when the Arabian, African and Indian plates collided with the Eurasian plate (Rice et al. 2006). Since the late Tertiary, Turkey has been moving toward the Eurasian plate whose resistance splits Turkey along a northwest direction, forming eastwest extending horst-graben structures in the west. The geomorphologic evolution of Turkey includes pre- and post-Miocene phases that constrained the paleo- and neotectonic phases. The Central Anatolian Plateau owes its present morphology mainly to erosional processes before the Miocene, whereas the rest of the country continues to evolve by ongoing uplift processes. The evolution of river basins and development of major river valleys are a result of these geological processes.

17.4. GENERAL CHARACTERIZATION OF TURKISH RIVERS Because of its complex geologic, geomorphic and climatic settings, Turkey has many rivers that enter the surrounding seas and neighbouring countries of Iraq, Iran and Armenia (Figure 17.1). Overall, 26 main drainage basins, including 4 endorheic basins lacking an outflow to the sea, occur in Turkey. In this chapter, we focus on 16 catchments, although the Terek and Kura Rivers are covered only marginally because of limited available information (Table 17.1). We also briefly describe the endorheic basins. Turkish river basins can be generally characterized by the following. The Euphrates, Kızılırmak, Kura and Aras drain large basins (each >90 000 km2). Most other rivers drain catchments <30 000 km2. Specific runoff (L/m2/year) is highest in rivers that drain the Pontid and Taurid Mountains because of high precipitation and low evaporation rates. Rivers that drain into the eastern Mediterranean Sea (Seyhan, Ceyhan) and some eastern Anatolian rivers (Euphrates, Tigris) also have high specific runoffs. The basins of northeastern Turkey (Coruh, ¸ Aras), Central Anatolia (Sakarya, Ye¸silırmak, Kızılırmak) and the Marmara region rank second in specific runoff. Total and specific runoff is low in the

645

Chapter | 17 Rivers of Turkey

FIGURE 17.1 Digital elevation model (upper panel) and drainage network (lower panel) of Rivers of Turkey.

closed Anatolian basins because of low precipitation and high evaporation rates. The Aegean basins (G€ oksu, Gediz, Smaller and Greater Meander) also exhibit low specific runoffs (Photos 17.1–9). Turkey is drained by 107 major rivers, each with a catchment area >1500 km2. Kızılırmak is the longest river (1355 km), followed by the Euphrates (Fırat; 1263 km in

Turkey), Tigris (Dicle; 523 km in Turkey), Seyhan (560 km), Aras (548 km in Turkey), Ye¸silırmak (519 km), Ceyhan (509 km), Coruh ¸ (442 km in Turkey), Gediz (400 km), Susurluk (321 km), Greater Meander (307 km) and Smaller Meander (174 km). Of these, the Euphrates, Tigris, Meri¸c, Coruh, ¸ Aras and Asi are transboundary rivers (www.dsi.gov.tr).

TABLE 17.1 General characterization of the Rivers of Turkey Tigrisa Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25%) ecological regions Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparce vegetation Wetland Freshwater bodies Protected area (% of catchment) Water stress (1–3) 1995 2070 Fragmentation (1–3) Number of large dams (>15 m) Native fish species Non-native fish species Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person)

1451

Euphratesa Asi 1383

530

Ceyhan

Seyhan

1010

1329

57 614 127 304 6573 21 982 21.33 31.61 1.17 7.18

G€ oksu 1276

Greater Smaller Gediz Meander Meander 831

406

20 450 10 500 24 976 3586 8.01 0.31 3.03 1.19

577

Sakarya Kızılırmak Ye¸silırmak Coruh ¸ 965

1160

1213

1850

Terek Kura Aras (with Aras) 993

1269

18 000 58 160 78 180 36 114 19 872 43 795 193 803 1.95 6.40 6.48 5.80 6.30 n.d 17.1

1555 98 718 4.63a

65.8

55.9

71.4

61.9

54.5

57.0

67.3

71.0

67.8

51.4

45.7

49.8

69.0 71.9

52.7

46.4

12.6

11.0

16.8

12.2

10.9

11.8

13.5

15.5

13.9

10.6

9.5

9.2

5.5 6.6

8.7

8.3

4

7

3

3

5

3

3

2

2

5

5

3

5

6

5

30; 71

29; 31

31

29; 31; 65

19; 65

65

1; 3

1; 3

1; 3

3; 49

19; 49

49

16

16; 55 7; 16; 30

30

0.0 37.7 26.7 21.5 12.8 0.0 0.1 1.2

0.1 30.6 31.4 17.8 18.6 0.0 0.1 1.4

0.0 46.0 0.4 4.6 46.6 0.0 1.1 1.3

0.1 37.2 1.1 5.0 56.0 0.0 0.0 0.6

0.1 31.9 0.0 9.3 57.8 0.0 0.0 0.9

0.0 13.8 0.0 4.7 80.5 1.0 0.0 0.0

0.1 25.5 0.0 5.5 67.8 0.0 0.1 1.0

0.2 14.8 0.2 4.7 79.9 0.0 0.1 0.1

0.1 15.0 0.2 5.2 78.5 0.0 0.2 0.9

0.4 44.6 4.9 16.5 32.8 0.0 0.1 0.7

0.1 56.0 5.9 7.0 30.4 0.0 0.0 0.6

0.1 43.7 15.3 9.7 30.7 0.0 0.0 0.5

0.0 28.4 11.7 30.7 27.7 0.0 1.4 0.1

2.2 43.7 2.1 30.8 18.8 1.6 0.2 0.6

0.6 41.8 14.1 24.4 17.3 0.1 0.3 1.4

0.5 37.1 25.4 21.2 13.6 0.1 0.4 1.7

0.0

0.0

0.0

0.0

0.0

0.5

0.0

0.0

0.0

0.0

0.1

0.0

0.3 13.9

5.5

6.1

3.0 3.0

3.0 3.0

2.8 3.0

3.0 3.0

3.0 3.0

1.3 2.9

2.8 3.0

1.7 3.0

2.7 3.0

1.9 3.0

2.1 2.9

2.9 3.0

1.3 2.0 2.2 2.0

2.9 3.0

2.9 3.0

3

3 11

3 49

3 4

3 17

3 18

3 7

3 12

3 11

3 13

3 63

3 87

3 66

3 4

2 n.d

3 n.d

3 2

46 2 2 65

42 1 6 57

52 3 1 182

35 3 2 91

29 3 1 92

23 3 0 73

37 4 3 83

28 2 0 253

24 3 1 113

63 5 4 97

52 3 3 58

49 3 1 60

14 2 0 37

n.d n.d 3 76

33 8 3 74

28a 1a 1 72

1311

1535

2196

2167

2711

3131

2726

4134

3065

3327

2260

1967

1934

1062

1267

1266

n.d.: No data. Mean annual discharge from Ana¸c and Celiker (2004). a Only Turkey. For data sources and detailed explanation see Chapter 1.

Chapter | 17 Rivers of Turkey

647

PHOTO 17.1 Ye¸silırmak River at Amasya (Photo: Aydın Akbulut).

The Ergene basin is a subcatchment of the Meri¸c catchment (see Balkan Chapter) that originates in Bulgaria and forms the political boundary between Greece and Turkey. The Ergene drains an undulating terrain (catchment area: 14 560 km2) covered by paleogene, neogene and quaternary bedrock. The main stem of the Ergene River (total length: 280 km) is fed by >10 tributaries that mostly originate in the Istranca Mountains (NE Thrace). The most important rivers that drain into the Aegean Sea include the Greater Meander (Menderes) (catchment area: 24 976 km2), the Gediz River (18 000 km2) that enters the Aegean Sea just north of Izmir and the Smaller Meander (Menderes) (area: 3586 km2). Other important rivers are the Bakır¸cay, Karamenderes and Havran and are not covered in this chapter. The Aegean rivers start in western Anatolia with either partly developed basins or along sinking valley bottoms from horst-graben tectonics along the Aegean coast. The basins are mainly of metamorphic, tertiary-sedimentary and volcanic-sedimentary bedrock. The mean relief of the Aegean river valleys is <500 m, whereas the catchment relief can be up to 1500 m. The geomorphic term ‘meander’ originates from the Greater Meander with its sinusiodal shape in the lowlands of the Aegean valley. The G€ oksu, Lamas and Tarsus are the main rivers in the eastern Mediterranean area. The G€ oksu drains a mountainous area (10 500 km2) in the Central Taurid Mountains with a catchment relief of 3000 m. Neogene sedimentary and karstic carbonate bedrock dominates the basin. The 824 km Sakarya River, named Sangarios in ancient Greece, is the third largest river in Turkey and drains a catchment of 58 160 km2. It originates from five springs in

the western Anatolian Plateau (known as ancient Phrygia), the so-called Sakarba¸sı. The catchment consists mostly of neogene-lacustrine and volcanic-sedimentary bedrock in the headwaters, whereas paleogene and mesozoic bedrock of metamorphic and detritic origin dominate in the lower part. Its major tributaries are the Porsuk, Kirmir, Ankara, G€ oyn€ uk and Mudurnu Rivers. The mean basin relief is 1160 m. The Kızılırmak River (Red River) is Turkey’s longest river at 1355 km. Starting at Kızıldag in the Sivas province, it flows across the Central Anatolian plain, cuts through the Pontid Mountains and enters the Black Sea near the town of Samsun. The catchment (area: 78 180 km2) includes sedimentary, magmatic and metamorphic bedrocks from the Mesozoic to Neogene periods. The name – Red River – is derived from the high concentration of suspended clay particles that causes its characteristic reddish colour. The 519 km long Ye¸silırmak River (Green River) drains a 36 114 km2 catchment (5% of Turkey) that contains a complex mosaic of sedimentary, magmatic and metamorphic bedrock formed during the Mesozoic to Neogene periods. Originating in the Central Anatolian Plateau, the river first flows through inter-mountain valleys before it cuts through the Pontid Mountains and enters the Black Sea. Two major tributaries, Cekerek ¸ (length: 256 km) and Kelkit (320 km), join the Ye¸silırmak river. The Pontid Mountains are up to 3000 m high, although most of the basin is at 1000 m asl. The 560 km long Seyhan River (basin area: 20 450 km2), called Sarus River in ancient times, originates in the TahtalıMountains (Sivas and Kayseri provinces). It cuts through the Taurid Mountains, passes the Cukurova ¸ coastal plain, and finally enters the Mediterreanean Sea, forming a vast delta.

648

PART | I Rivers of Europe

PHOTO 17.2 Aras River at Ani Ruins (Kars) (Photo: Ali Demirsoy).

The low-lying plain consists of quaternary and neogene sediments. The headwaters (maximum elevation: 3500 m) primarily consists of mesozoic carbonates and ophiolitic bedrocks as well as neogene sediments and volcanicsedimentary bedrock. Major tributaries of the Seyhan River are the G€ oksu, Zamantı, Cakıt ¸ and K€ ork€ un Rivers. The Ceyhan River, formerly Leucosyrus, was one of the great rivers of ancient Asia Minor. It drains a mountainous catchment (21 982 km2) in the eastern Taurids that consists primarily of paleozoic, mesozoic and tertiary bedrock. Karstic carbonate rocks are also widespread. The 510-km long river originates at an elevation of 3000 m asl. Flowing in a southwestern direction it passes through the Cukurova ¸ floodplain and delta before it enters the Mediterranean Sea at _ the Bay of Iskenderun.

The Asi River, or Orontes, originates in Lebanon near Balbek, flows northward between the Lebanon and AntiLebanon Mountains, crosses northwestern Syria and passes Antakya in Turkey before it drains into the Mediterranean Sea. In ancient times, the Asi formed an important corridor between Asia Minor and Egypt. The Turkish part of the Asi is in the northeast Amik plain where tributaries from Syria and Turkey enter the main stem. While the plain is dominated by quaternary alluvium, surrounding heights are formed mainly by ophiolitic, detrital and carbonate rocks of Paleozoic to Tertiary age. The Euphrates (Fırat) drains the largest basin in Turkey (catchment area: 127 304 km2). It begins in the highlands northeast of the Anti-Taurid Mountains (peaks: >3000 m) and forms a large ‘C’ before entering Syria at 300 m asl.

Chapter | 17 Rivers of Turkey

649

PHOTO 17.3 Asi River at Hatay (Photo: Ali Demirsoy).

The region is tectonically active, with major faults running throughout the Anti-Taurid Mountains. The Karasu and Murat Rivers are its major tributaries in Turkey. The basin is mostly covered by neogene volcano-sedimentary bedrock. The Tigris River (Dicle), draining southeastern Anatolia, is one of the largest rivers in Turkey with a catchment

area of 57 614 km2. The Batman, Garzan, Botan and Hezil Rivers are its major tributaries in Turkey. The rectangular basin drains a mountainous area with peaks >3000 m asl. Sedimentary and karstic carbonate rocks of Paleozoic to Tertiary origin cover the basin. Metamorphic rocks dominate in the headwaters. The Tigris is the

PHOTO 17.4 Ceyhan River near Adana (Photo: Aydın Akbulut).

650

PART | I Rivers of Europe

PHOTO 17.5 Coruh ¸ River at Artvin (Photo: Aydın Akbulut).

second largest basin within the GAP project in southeastern Turkey. It enters Iraq at 300 m asl and forms, together with the Euphrates, the Shatt-el-Arab in southern Iraq before entering the Persian Gulf. The Coruh ¸ River is one of the most important rivers in northeast Turkey. It drains a mountainous catchment (area: 19 872 km2) that consists primarily of mesozoic and

neogene volcanic bedrock. The 446 km long main stem of the Coruh ¸ is fed from the Mescit Mountains (3250 m asl) and flows in a northeast direction before entering the Black Sea in Georgia (24 km of the river are in Georgia). The Aras River drains a mountainous catchment (area: 27 548 km2 in Turkey, total 98 718 km2) that is covered

PHOTO 17.6 Euphrates at Ili¸c in the province Erzincan (Photo: Aydın Akbulut).

651

Chapter | 17 Rivers of Turkey

PHOTO 17.7 Sakarya River Adapazarı (Photo: Aydın Akbulut).

mainly by neogene-sedimentary, volcano-sedimentary and volcanic rocks. The Aras originates from mountains exceeding 3000 m asl in the west. It then joins the Arpa¸cay, a major tributary draining the northern basin, forming the Turkish–Armenian boundary, before entering Iran and flowing towards the Caspian Sea in Azerbaijan.

at

17.5. CLIMATE The climate of Turkey is dominated by various weather trajectories that (i) originate either from the Atlantic Ocean and move across the Balkans and the Mediterranean Sea, (ii) originate from Russia and move across the

PHOTO 17.8 Seyhan River at Adana (Photo: Aydın Akbulut).

652

PART | I Rivers of Europe

PHOTO 17.9 Tigris River at Hasankeyf in the province Batman (Photo: Ali Demirsoy).

Black Sea, or (iii) enter the country from the Persian Gulf through Iraq. Most precipitation falls from late autumn to early spring. The Pontid and Taurid Mountains form major orographic barriers. Annual precipitation ranges between 1000 and 2000 mm along the coast and mountains, decreasing towards the Central Plateau. In Central Anatolia, mean annual precipitation ranges from 350 to 500 mm, in eastern Anatolia from 600 to 900 mm, and in the Marmara and Aegean regions from 600 to 800 mm. Near the Mediterranean Sea, annual precipitation ranges between 800 and 1000 mm, and peaks in winter (Kadıoglu 2000). Turkey has four major climatic zones: (i) Continental, (ii) Black Sea, (iii) Mediterranean Sea and (iv) Marmara Transitional. The Continental climate zone may be further subdivided into Central, East, Southeast Anatolian and Thrace sub-types. The sub-types define different annual precipitation and temperature regimes. The Continental climate is characterized by winter-dominated precipitation and extreme variation in annual temperature. The Black Sea climate zone is characterized by mild summers and winters along the coast but cold, snowy winters in the uplands. It receives precipitation in all seasons. The Mediterranean climate zone is characterized by hot dry summers and wet mild winters. In the Marmara area, a transitional climate type with Continental, Black Sea and Mediterranean Sea climates prevails. Continental Thrace, Black Sea and Marmara transitional climates dominate in the northwest and northeast Ergene basin. Long-term mean annual precipitation is around 700 mm, with a minimum of 500 mm in the northwest corner. Mean annual temperature ranges between 13 and 15 C in the various sub-basins. The Aegean basins (Gediz, Smaller and Greater Meander) are characterized by a Mediterranean climate with a mean annual precipitation ranging from 500 to 700 mm and a mean air temperature from 11 to 19 C.

The G€oksu basin is characterized by a Mediterranean climate. Long-term mean annual precipitation ranges between 400 mm (headwaters, lee side of the Taurid Mountains) and 1100 mm (coastal area). The mean annual temperature varies from 15.5 (coast) to 9 C (headwaters). Black Sea, Marmara transitional and Continental Central Anatolian type climates prevail in the lower, middle and upper Sakarya basin, respectively. Mean annual precipitation ranges from 1100 (Black Sea area) to 500 mm (continental inland area). Mean annual temperature increases from 9 (headwaters) to 15 C (near the mouth). The upper Kızılırmak basin, comprising about 67% of the basin, is in the dry Continental Central Anatolian climate region. The lower section has a more humid climate. Mean annual precipitation (air temperature) in the inland and coastal zones are 400 (7 C) and 700 mm (15 C), respectively. About half of the Ye¸silırmak Basin is in the Continental Central Anatolian climate region, whereas the lower reach has a Black Sea climate. Long-term mean annual precipitation ranges from 500 to 800 mm in the upper and lower basin, respectively. Mean annual temperature ranges from 9 (upper basin) to 15 C (lower basin). In the lower Seyhan basin, a Mediterranean climate prevails with hot dry summers and mild wet winters. Mean annual rainfall is 650 mm and most precipitation occurs December through May. Longterm mean annual precipitation ranges from 800 (coastal zone) to 400 mm (uppermost reach). In the lower reach, the mean temperature is 19 C with a maximum of 44 C and a minimum of 6.4 C. The upper Ceyhan basin is characterized by a Continental East Anatolian climate, whereas the lower reach has a typical Mediterranean climate. Long-term mean annual precipitation and air temperature are 500 mm and 7 C (upper catchment) and 700 mm and 19 C (lower catchment), respectively. The Turkish part of the Asi River has a

Chapter | 17 Rivers of Turkey

Mediterranean climate with a rainy season between November and April. Mean annual precipitation and temperature ¨ demis et al. 2007). are 1120 mm and 18.1 C, respectively (O Continental East and Southeast Anatolian climatic regimes prevail in the Euphrates and Tigris basins. These basins are mainly fed by winter precipitation that is released during the spring snowmelt. Long-term mean annual precipitation decreases from 900 (Murat tributary) to 500 (central part) to 400 mm (southern part). The porous limestone underlying the Eurphrates basin absorbs significant portions of the snowmelt. Rain runoff is released gradually during the summer and autumn. Mean annual temperature ranges from 3 (headwaters of Euphrates) to 19 C (Syrian border). The northern part is known for its extreme temperatures, from 35 to +38 C. About 67% of the Coruh ¸ basin is along the southern flank of the East Black Sea mountain ridge where a Continental Eastern Anatolian climate dominates. Long-term mean annual precipitation ranges between 500 and 1600 mm in the upper and lower basin, respectively. Mean annual temperature is 7 (headwater) and 15 C (mouth). The Aras basin has a Continental East Anatolian climate with cold dry winters. Long-term mean annual precipitation ranges from 300 (eastern part) to 500 mm (western part). Mean annual temperature ranges between 3 and 9 C.

17.6. LAND USE PATTERNS Turkey has 28 million ha of arable area, 20 million ha of forests and 15 million ha of pasture. At present, 4.9 million ha are irrigated and the economically irrigated land is estimated at 8.5 million ha. Some 51% of the remaining forests are considered to be productive, whereas the other forests are unproductive or highly degraded due to overexploitation. Most forests are in the Black Sea, Mediterranean Sea and Aegean Sea regions (Kaya & Raynal 2001). The forests belong to the Euro-Sibirian (Black Sea and Marmara), Irano-Touranian (Inner, Eastern and Southern Anatolia) and Mediterranean (other areas) floristic regions. Plains covered by alluvial sediments cover 19 million ha, or 24% of the land area of Turkey. Turkey has reached its limit of cultivated land with about only 2 million ha of land remaining for additional cultivation (WCD 2000). No significant increases in the total area of cultivated land have occurred in the last three decades. However, there have been important changes in the allocation of cultivated lands to different crops. The area under field crops increased from 15 million ha in 1960 to 19 million ha in 1990. This increase was partly due to the increase in the total cultivated area and partly due to the decrease in fallow lands. Fallow lands covered nearly 8 million ha until 1980, declining to 5 million ha by 1990. Fruit and vegetable lands have increased three-fold between 1960 and 1990, while vineyards have decreased by about 40%, from 0.8 million ha in 1960 to 0.6 million ha in 1990. On the other hand, the area

653

used for olive trees has increased by about 50% from its level of 0.6 million ha in 1960 to 0.9 ha in 1990 (WCD 2000). The Ergene basin has been converted to agricultural lands in lowland areas and to grasslands at higher elevations. Conifer and deciduous forests are restricted to the Istranca Mountains. The lowlands of the Ergene basin are subject to frequent flooding. The Aegean catchments (Greater and Smaller Meanders, Gediz) have been almost completely transformed into agricultural land. Animal grazing is restricted to a few areas in the headwaters. Heavy industry exists around the urban cen_ ters of Izmir, Aydın, Manisa and Denizli. Mountainous areas still contain rich conifer and deciduous forests. Coastal areas have been intensively developed for the tourist industry. The Eastern Mediterranean area, including the G€ oksu basin, contains large relatively unspoiled forested mountains and alpine meadows. Coastal areas constitute an important section of the Turkish Riviera with intensive tourism. The coastal plains contain major greenhouse facilities and fruittree plantations. Industrial complexes have been developed around the city of Mersin. The Sakarya basin has been mostly converted into agricultural lands, meadows and pastures. Deciduous and conifer forests are restricted to the Black Sea Mountains. The Kızılırmak basin covers mostly the Central Anatolian Plateau. Meadows and pastures for animal grazing and large plains for agriculture dominate. The lower areas, passing through mountains, include conifer and deciduous forests. Neogene gypsum formations, mainly in the Sivas province, have caused an increase in salinity and therefore limit the water use for agriculture and domestic purposes. Further downstream, inputs from tributaries reduce salinity. The inner mountain plains of the Ye¸silırmak basin (Niksar, Erbaa, Tokat, Amasya) are used as meadows and pastures. Conifer and deciduous forests cover mountainous areas. Agriculture dominates in the plains, whereas high altitude plains are used for animal grazing. The upper Seyhan catchment is covered by immature plains suitable for cultivation and meadows for animal grazing. Woodlands and forests (conifer and deciduous) extend mostly along the southern slopes of the Taurid Mountains. Animal grazing predominates in the Taurid Mountains. Downstream of the Seyhan dam, 85 km from the mouth, the river flows through the large urban area of Adana before being diverted to irrigate (so-called Lower Seyhan Irrigation Project) the most fertile plains in Turkey, the Tarsus (80 000 ha) and Y€uregir plains (130 000 ha) (Onur et al. 1999). Since the year 2000, high value cash crops such as citrus and vegetables have become important in these plains. Other crops such as maize and soybean are also important. Cotton production, once dominant in this area, shifted to the Harran plain after the completion of the Atat€urk dam. Industrial production has increased since 1950, where about 40% of the GDP in the Adana province results from industrial production today, mainly from the metal and textile industries.

654

PART | I Rivers of Europe

In the Ceyhan basin, the coastal plain and intra-mountainous plains (e.g. Elbistan) have been partly converted to agricultural land. Animal grazing is widespread in the mountains and inland steppe. Conifer and deciduous forests cover mountain slopes. Human impact, in historical times limited to deforestation, has become more severe during the last century with the construction of dams and the start of extensive agricultural activities. The Asi basin is used intensively for agriculture because of its fertile soils. In Turkey, 60% of the basin is classified as agricultural land. Here, 460 000 people reside and 50 000 ¨ zdilek & Sang€un 2007). cows, sheep and goats graze (O About 12 000 ha of the Amik plain, Hatay, are irrigated and plans exist to irrigate up to 50 000 ha. In this region, 61% of the population depends on agriculture, fishing, stock breeding and forestry. About 200 industrial complexes are found in the Turkish part of the basin that discharge pollutants into the river. In the Euphrates basin, a rough topography and harsh climate have limited human impacts from deforestation in historic times. Before the establishment of large-scale irrigation schemes in the last decades, agricultural land use was restricted to small areas fringing the main stem that contain enough water throughout the year. Animal grazing in the Anatolian steppe was the main economic activity in the past. In the eastern Tigris basin, animal grazing, except for small-scale cultivations in intra-mountain valleys, is the main activity. In the western basin, a much flatter topography and the presence of wide plains allow irrigation, which will fundamentally convert land in the near future into agricultural land. To develop land and water resources in the Euphrates and Tigris basins the ‘Southeastern Anatolian Project’ (G€ uneydo gu Anadolu Projesi, GAP) was developed. GAP is an integrated socio-economic development project that not only aims to develop land and water resources but to also increase education and healthcare for an area of 75 000 km2.

The total cost of the project is estimated to be 32 billion USD and about half of the planned work has been completed. Following the partial realization of the irrigation network within GAP, land use practices dramatically changed. Accordingly, soil salinity has become a problem in those parts of the basin where proper irrigation practices have not yet been implemented. The Coruh ¸ basin is covered largely by woodlands and forests (conifer and deciduous), whereas meadows and pastures are restricted to topographically favourable areas. Agriculture is restricted to narrow strips along streams and rivers. Because of the harsh climate, land use in the Aras basin is restricted largely, since historical times, to animal grazing. While mountains are covered by woodlands and conifer forests, the slopes are used as meadows and pastures. Agriculture is restricted to surroundings of large settlements and to the fertile Igdır plain along the Aras main stem near the border.

17.7. GEOMORPHOLOGY OF RIVER BASINS The development of river basins has been strongly affected by palaeogeographic conditions. Ongoing tectonic uplift and faulting as well as the cooler Pleistocene climate have been the main drivers of the hydrogeomorphic development of the river basins. During the neotectonic period, continual uplift has increased erosion in the highlands. Increased sediment deposition in the lowlands has led to the formation of vast coastal plains and deltas (Table 17.2). Furthermore, many rivers have been strongly affected and redirected by various types of faults that were created or reactivated by tectonic activity. Historical settlements such as Troy and Ephesus, once near the sea, are now many kilometres away from the coast. Being located in the temperate climate zone, the role of glacial erosion in shaping river valleys has long been

TABLE 17.2 Ten of the largest river deltas of Turkey Delta forming river

Area (km2)

Average temperature ( C)

Population (People/km2)

Arable + Pasture (%)

Protected (%)

Terek Kura Seyhan Kızılırmak Ceyhan Gediz G€ oksu Greater Meander Sakarya Smaller Meander

4026 4175 1903 474 176 72 96 94 43 27

11.6 15.5 17.1 11.1 17.6 16.0 15.4 15.9 11.4 16.0

46 78 116 126 118 258 106 118 174 256

76.1 17.6 46.8 3.8 61.0 70.4 17.9 91.5 25.0 3.3

3.3 20.6 <0.1 <0.1 <0.1 <0.1 53.6 <0.1 <0.1 <0.1

Average annual temperature (1961–1990). Human population density: people per km2. Protected: National parks, Ramsar sites, National nature reserves, and other nationally protected areas. For data sources and detailed explanation see Chapter 1.

Chapter | 17 Rivers of Turkey

regarded as a marginal process, except in the high mountain ranges. However, recent findings in different parts of Turkey provide clear evidence of strong glaciation during the Last Glacial Maximum (21 000 BP), and again during the early Holocene cooling (9000 BP) (Zreda et al. 2005). Deep valleys and gorges that are characteristic for many basins have been strongly shaped by glacial scouring and erosion. Enhanced river discharge rates combined with rapid uplift during the Quaternary pluvial periods seem to be critically important for the present morphology of many river basins. Turkish lakes show great variation in origin, surface area, water type and depth. Lake Van is the largest soda lake globally with a surface area of 3740 km2. Tuz Lake is the largest evaporite lake in Europe (area: 1640 km2). Moreover, nine lakes with a surface area between 100 and 650 km2, seven lakes between 40 and 50 km2, and 15 lakes between 10 and 40 km2, occur in Turkey. Most lakes are shallow (<10 m) and exhibit large cyclic water level fluctuations. Many inland lakes were much larger during the cool and wet Quaternary periods. A remarkable example during that period was the formation of the large (>4000 km2) and deep (20 m) palaeo Konya Lake that disappeared around 16 000 BC. Four smaller lakes and marshes remained in sub-depressions but they dried up around 9000 BC (Roberts 1983). The most ancient archaeological sites in Anatolia, Catalh€ ¸ oy€uk near the palaeo Konya Lake and Hacılar near Lake Burdur (west of Konya Lake), are two typical former settlements along ancient lakes. In Turkey, over a million ha of wetlands or shallow lakes have been irreversibly lost during the 20th century, mainly since 1960, for land reclamation, flood control and irrigation (Turan & Beklio glu 1989). A distinct feature of most Turkish rivers is the formation of vast deltaic landscapes (Table 17.2). Ten of the largest deltas cover a total area of about 11 000 km2, although the exact delineation of delta boundaries remains difficult. High sediment yield, low coastal erosion, a moderate tidal range and a shallow coastal topography favoured the formation of deltas. These deltas are ecologically and economically critical landscapes, and many of them have high conservation value. In addition, deltaic areas are highly fertile areas and have been transformed into cropland. However, the construction of large dams in upstream river sections has reduced sediment transport. Presently, over 90% of the sediments are now retained in these impoundments. As a consequence, the deltas are shrinking due to a deficit in sediment input and subsequent coastal erosion. For example the Seyhan River Delta increased on average 2.8 ha per year up to 1954. This process began to reverse with the construction of two large dams and an area of 101 ha was lost between 1954 and 1995 due to coastal erosion (Cetin ¸ et al. 1999). The morphologic development of the Ergene basin is controlled by the relative resistance of various lithologies against erosion. Metamorphic and magmatic rocks of the Istranca Mountains force the Meri¸c River to flow southwards where many tributaries then join the main stem. The smooth topography and fertile soils have resulted in the transforma-

655

tion of the formerly forested catchment into agricultural land. Extensive agricultural activity and industrial development have caused severe impacts in the basin. Along the Aegean coastal zone, ongoing active north– south directed extentional tectonics resulted in the formation of several east–west river valleys. Consequently, all Aegean River valleys such as the Gediz, Greater and Smaller Meanders have been formed by horst-graben tectonics. Because this process has been occurring since the late Miocene, topographic outcrops have been largely erased leaving the present mature/sub-mature morphology. During the past several thousand years, the Gediz River has frequently changed its lower course. Today, it forms a large delta (Table 17.2). Until 1886, the delta was about 50 km west of Izmir. In 1886, the river was diverted to prevent silting up of Izmir harbour. In 1963, the course of the river had been changed again by human interference and, as a result, the wetland has increased in salinity. The G€oksu River has a steep topography (almost 3000 m over a distance of 40 km) that extends northwards to the enclosed Konya basin. The catchment is characterized by deep valleys and gorges carved into neogene sedimentary and carbonate bedrocks. The mountainous area had limited human impacts historically (except some forestry). The geomorphologic development of the Sakarya basin is rather complicated. In the past, the upper and middle basin most likely drained into the Marmara Sea as two separate river systems when topographic gradients were much steeper. The middle section then captured today’s upper reach, turning towards the Black Sea along north trending younger valleys that developed along the tectonically disrupted zones by the North Anatolian fault system. The basin has been subject to intensive human impact since historical times, which has intensified during the last century. Many dams have been built along the Sakarya River and on its tributaries to regulate flows. The geomorphic development of the Ye¸silırmak basin has been mainly controlled by the northern Anatolian dextral strike–slipe fault zone along which the river developed. The headwaters flow northwest along fault zones before entering the main stem, which flows in a northeastern direction. Deep valleys and gorges occur along these streams. The river forms a large alluvial floodplain before entering the Black Sea. The Ye¸silırmak Delta is a large wildlife conservation area. The Ye¸silırmak basin has been subject to major human impacts since historic times. Large parts of the Kızılırmak basin are in the geomorphologically mature Central Anatolian Plateau. Here, the valleys developed as slightly undulating lands. In the lower reaches, the main stem and its tributaries follow tectonically shaped, relatively deep narrow valleys. The river forms a large alluvial floodplain before entering the Black Sea. The Kızılırmak basin has been subject to intense human impacts since historical times. Prior to the Pliocene, the upper and lower Seyhan basin drained into different directions (north and south). Both

656

systems then merged to form the present drainage system that enters the Mediterranean Sea. The north basin formed on sub-mature land before the main stem cut through the mountain ridge with 1000 m deep canyons. Narrow deep valleys and gorges are typical in the middle basin. The Seyhan River leaves the mountains at 400 m asl and flows 60 km along the coastal zone before entering the sea. Catchment deforestation dates back to historic times. Other human impacts on river morphology were limited until recently, where the construction of dams began in the late 1950s. The geomorphic development of the Ceyhan basin has been controlled by the uplift of Asia Minor. In the upper basin, intra-mountain plains were formed within pull-apart type tectonic basins. The main stem then cuts through the Taurid Mountain ridge before meandering through the fertile Cukurova ¸ coastal plain. Narrow deep valleys and gorges are characteristic in the mountains where karstic processes also shape riverbed formation. In the lower basin, the Seyhan and Ceyhan Rivers were channelized between 1948 and 1953, and more drainage work was initiated in the 1960s to prevent malaria. The Asi River is nested in the Amik plain, which is a pullapart type tectonic basin formed by the differential movements of the southwestern strands of the East Anatolian fault zone. The plain is bounded by northeast trending heights and is open to the Mediterranean Sea in the southwest. Along this tectonic trench, the Karasu and Afrin (Bur¸c) Rivers join the Asi in its lower reach where once the so-called Amik Lake existed in a tectonic depression. From a geomorphological point of view, the Amik depression appears to have captured the main stem and its major tributaries during the Plio-quaternary. The Euphrates River begins in the highlands of the northern Anti-Taurus Mountains. This region is tectonically active with major fault zones traversing the Anti-Taurus. The major tributaries of the Euprates, Karasu and Murat, follow a roughly westward route along intra-mountain valleys with a relief of about 1500 m. At their confluence with the main stem around the Keban dam, the Euphrates flows southeast and then southwest before entering Syria. The geomorphic development of the Tigris basin has been primarily controlled by the uplift of the Anatolian Plateau and the formation of volcanic-sedimentary units. The main stem of the Tigris follows an east trending topographic low bounded valley between the Taurids in the north and the Mardin anticline in the south. The Tigris receives other tributaries that drain karstic carbonate rocks of the Taurid Mountain ridge. The mean relief in the western and eastern basins is <1000 m and 2000 m, respectively. Narrow deep valleys and gorges are characteristic channel forms of the Coruh ¸ basin, although flat areas are found locally. The upper valley was glacially scoured during the Plio-quaternary. Two major tributaries, Tortum and Oltu, join the main stem around Rkm150. The thalweg gradient becomes steeper after the city of Artvin where the river starts to cut through the Black Sea Mountains. The Coruh ¸ basin

PART | I Rivers of Europe

had limited human impacts during historical times. Deforestation and acid mine (copper) drainage started to show impacts in the last century. The Aras basin, in the northeastern high Anatolian Plateau, forms the upper reach of a major drainage system that developed towards the Caspian Sea. The upper basin, which also includes the highest mountain in Asia Minor (Mt A grı, 5165 m asl), was glacially scoured during the Plio-quaternary. From the confluence of the main stem and Arpa¸cay River, the Aras flows through relatively mature topography that forms the Igdır plain. The Aras basin had limited human impacts historically, although deforestation and overgrazing were common.

17.8. HYDROLOGY AND TEMPERATURE The total mean annual runoff of all Turkish rivers is 186 km3, corresponding to an average runoff coefficient of 0.37 (total annual precipitation: 500 km3). Exploitable water resources, including groundwater (69 km3), are about 1500 m3 per capita, but this is predicted to decrease to 1000 m3 by 2030 due to an increase in the human population. The human population is expected to increase from 73 million in 2006 to 100 million in 2030 (www.dsi.gov.tr; Bayazıt & Avcı 1997). The present per capita water potential is nearly the same as in the neighbouring countries Iraq (2000 m3/year) and Syria (1400 m3/year). In Turkey, the minimum and maximum annual surface runoff rates are 27 (Afyon basin in Central Anatolia) and 889 mm (Black Sea drainage basins), respectively. Mean annual water temperature ranges from 8.5 (Aras River) to 17.2 C (Asi River). On average, water temperatures of western and southern catchments are 3.7 C higher than water ¨ demi¸s & temperatures of central and eastern catchments (O Evrendilek 2007). The Tigris has the highest water temperature of all eastern Anatolian rivers. Turkey has a gross annual hydropower potential of 433 TWh, almost 14% of the capacity of all Europe (Evrendilek & Ertekin 2003). Almost 50% of the gross potential is technically exploitable, and 28% is economically exploitable. Currently, 34% of this economically exploitable potential is already used. A total of 120 power plants have an installed capacity of 11 588 MW (35% of the present electricity demand, Table 17.3). Thirty-four hydropower plants are under construction (total capacity: 3305 MW) and 329 more plants are projected (capacity: 19 700 MW). By 2020, more than 480 power plants are expected to be in operation. While these power plants generate energy necessary for the economic development of the country, they also create major long-term environmental impacts on Turkish rivers. All major rivers are already heavily fragmented, retain large amounts of sediments and exhibit an altered flow and thermal regime. In addition to the dams constructed for hydropower generation, there exist several hundred large dams primarily

657

Chapter | 17 Rivers of Turkey

TABLE 17.3 Turkey’s largest hydropower plants (after Bayazıt & Avcı 1997, www.dsi.gov.tr) Dam

Year

River

Installed power (MW)

Energy (GWh/year)

Atat€ urk Karakya Keban Altınkaya Oymapınar H. Ugurlu Sır K€ okl€ uce Aslanta¸s G€ ok¸cekaya Gezende Menzelet

1995 1987 1975 1988 1984 1982 1991 1988 1984 1973 1990 1989

Euphrates Euphrates Euphrates Kızılırmak Manavgat Yesilirmak Ceyhan Yesilirmak Cehan Sakarya Ermenek Ceyhan

2400 1800 1330 700 540 500 283 90 138 278 159 124

8900 7354 6000 1632 1620 1217 725 588 569 562 528 515

used for irrigation and flood control. Turkey, with more than 650 large (>15 m) dams, has the second highest number of large dams in all Europe (after Spain). Over the past 30 years, a significant decrease in discharge has been detected in the Mediterranean, Aegaen, Marmara and Central Anatolia regions (Figure 17.2). The minimum flow during the dry summer months (July–September) is particularly affected by increasing water demands and climate change (Topalo glu 2006). Between 1995 and 2002, the average decrease in the mean annual flow rate was 4 m3/s and the average annual water temperature increase was ¨ demi¸s & Evrendilek 2007). 0.2 C (O The Ergene River is regulated by five multi-purpose dams constructed during the last two decades. Mean annual discharge and specific runoff are 1.3 km3 and 2.9 L/s/km2, _ 2000, 2003). Mean, maximum and minirespectively (EIE mum flow rates are 33.3, 582.6 and 0.2 m3/s, respectively (Station-105, 9 m asl, catchment area at station: 10 195 km2). During hot summers, the river almost dries up due to water abstraction for irrigation. Mean daily water temperature ranges from 1.0 to 33 C (annual mean: 13.3 C). The river has a flashy flow regime – peak floods exceed mean flow by a factor of 18 – due to low soil permeability and limited storage capacity of existing reservoirs. Flooding has been controlled by new dykes and dams since the late 1990s. The increasing surface storage capacity has led to an increase in minimum water temperature by 5 C since the late 1980s. At the same time, specific conductance of the river has increased from 1000 to 4000 mS/cm. Because of the low topographic gradient, Aegean rivers possess little appreciable hydropower potential. Even so, many irrigation dams have been constructed. The mean annual discharge of Aegean rivers is 9.1 km3. Specific runoff varies between 3.6 and 7.4 L/s/km2. The mean, maximum and minimum flow rate (1985–2002) of the Greater Meander River, the largest Aegean river, is 33.5, 171.9 and 0.1 m3/s, respectively (Figure 17.2). Water temperature ranges from 4 to 28 C (annual mean: 16.3 C). Floods having a discharge five times the annual mean occur every 5 to 10 years. In

summer, Aegean rivers suffer from water scarcity due to the absence of adequate groundwater recharge, and an increasing use of water for irrigation and household consumption. Along the Gediz River, one large (Demirk€opr€u) and three smaller (Lake Marmara, Afsar and Buldan) reservoirs have been constructed for hydropower generation and irrigation. The Demirk€opru reservoir provides water for 125 000 ha of irrigated land (total irrigated land in the basin: 150 000 ha). With the exception of the G€oksu and Tarsus, the Eastern Mediterranean rivers are partly unregulated, although several feasibility projects for hydropower production are currently being undertaken. Mean annual discharge and yield of the basins in this region are 11.1 km3 and 15.6 L/s/km2, respectively. Long-term (1970–2002) data at gauging station 1714 on the G€oksu River near the Mediterranean Sea is presented as an example of river hydrology in the eastern Mediterranean basin. The mean, maximum and minimum flow rates observed at this station are 95.2, 691.6 and 17.2 m3/s, respectively. The mean, maximum and minimum stream water temperatures are 15.4, 30 and 4 C, respectively. The flow regime of the Sakarya River has been altered by dams to generate hydropower and to supply water for domestic use and irrigation. Mean total annual discharge and specific runoff are 6.4 km3 and 3.6 L/s/km2, respectively. Mean, maximum and minimum discharge rates (1964– 1999) are 166.3, 842.9 and 10.0 m3/s, respectively. Seasonal water temperature ranges from 1 to 28 C (annual average: 13 C). Since 1990, the maximum temperature has increased mainly due to the construction of reservoirs. Floods exceeding five times the mean discharge still occur about every 5 years. The flow of the Ye¸silırmak is regulated by dams (Almus, H. Ugurlu and S.Ugurlu are the largest dams). Mean total annual discharge and specific runoff are 5.8 km3 and 5.1 L/s/km2, respectively. Mean, maximum and minimum discharge rates are 63, 415 and 4 m3/s, respectively (1970–1999, Station-1413 at 301 m asl, 2/3 of the total basin area, Figure 17.2). The maximum discharge ever recorded was 1914 m3/s. Water temperature ranges from 2 to 26 C (annual mean: 11.9 C).

658

PART | I Rivers of Europe

FIGURE 17.2 Long-term discharge data for selected Turkish Rivers.

Long-term observations indicate that floods exceeding mean flow by a factor of 7 occur on average every 3 years. The discharge of the Ye¸silırmak has been dramatically modified in recent years due to the construction of hydro-

power plants. The Suat Ugurlu dam, commissioned in 1979, is 40 km upstream from the mouth. It is not equipped with a fish pass, which limits the upstream migration of sturgeons. It has been shown that sturgeons are much less successful in

Chapter | 17 Rivers of Turkey

using fish ladders than salmonids. Downstream of the dam, the Ye¸silirmak remains relatively uneffected, although there are plans to dredge the riverbed for flood protection. The lower section receives waste waters from municipal and agricultural sources. There are also plans to divert water downstream of the Suat U gurlu dam for irrigation of farmland. Many dams (e.g. Hirfanlı, Kesikk€ op€ u, Kapulukaya, Geling€ ull€ u) have been built in the Kızılırmak River basin to regulate flow for hydropower production, irrigation, domestic water supply and flood control. Mean annual discharge of the basin is 6.5 km3. The basin yield (2.6 L/s/ km2) is relatively low due to the semi-arid climate in large areas of the basin. Based on long-term observations (1972– 1997) at Station-1528 (301 m asl, area: 57 000 km2), the mean, maximum and minimum flow rates are 115, 392 and 15 m3/s, respectively. The mean, maximum and minimum stream water temperatures observed at a nearby station are 12, 27 and 3 C, respectively. Since the basin is largely regulated, flood peaks rarely exceed 2.5 times that of mean flow. Long-term temperature records show no trends during the past three decades. The Kızılırmak is not used for navigation but it is an important source for hydroelectric power. The Kayseri metropolitan municipality is now working on a new project to divert water through Kayseri City. Prior to construction of the Seyhan (total storage capac¸ (1.6 km3) dams the total annual ity: 0.8 km3) and Catalan discharge of the Seyhan River was 8.0 km3 (average specific discharge: 12.3 L/s/km2, Figure 17.2). At Station-1818 (130 m asl, catchment area: 13 846 km2), located upstream of the two dams, the mean, minimum and maximum discharge rates (1970–2002) are 148, 52 and 1119 m3/s, respectively. Annual domestic use is 0.1 km3 and annual abstraction for irrigation amounts to 1.44 km3. The mean, maximum and minimum water temperatures are 15, 27 and 2 C. Long-term temperature records indicate a decrease in maximum and an increase in minimum water temperature since the early 1980s. The Ceyhan has a mean annual discharge of 7.2 km3. The mean, maximum and minimum flow rates are 223, 1712 and 24 m3/s, respectively (1965–1999, Station-2004 at 15 m asl, Figure 17.2). A high infiltration capability of karstic rocks in the mountains results in a relatively high basin yield at 10.7 L/s/km2. The mean, maximum and minimum water temperature is 17, 27 and 7 C, respectively. The hydrology of the Ceyhan has been altered during the last four decades. The Ceyhan Aslanta¸s Project (CAP) is a major catchment development scheme. The 95 m high, earth-filled Aslanta¸s dam, has a 13.8m3/s capacity gated spillway. The capacity of the reservoir is 1150 Mm3, and its surface area is 49 km2. The dam was completed in 1984 and serves for irrigation, flood control, and hydropower generation. As a consequence, annual peak flood in the river has been largely reduced. At Demirk€ opr€ u, near the Syrian border, the discharge of the Asi River can be as low as 0.9 m3/s during the summer

659

and high as 160 m3/s during the rainy season (Figure 17.2). A large dam has been constructed in Syria, leading to a decrease in discharge in Turkey. The average annual discharge at Demirk€opr€u decreased from 30 m3/s at the beginning of the 1980s to <15 m3/s today. Due to insufficient surface water, saline groundwaters are used for irrigation, which has caused a secondary salinization of the fertile soils. Maximum water temperature can be as high as 31 C during the dry months and as low as 8 C during the rainy season. Near the sea, the average annual water temperature ranges from 14.6 to 22 C. On the Euphrates, at the confluence of the Karasu and Murat tributaries, the large Keban dam (675 km2) was constructed. Further downstream are the Karakaya (268 km2) and Atat€urk (817 km2) dams. While all dams are for hydropower generation, the Atat€urk dam also provides water through a 26 km long, double-tunnel system to irrigate the vast S ¸ anlıurfa plain. The mean annual discharge and yield of the Euphrates in Turkey is 31.6 km3 and 8.3 L/s/km2, respectively. Long-term (1977–1999) records at the gauging station at the Turkish-Syrian border (340 m asl, area: 100 702 km2) show the mean, maximum and minimum flow rates are 817, 3352 and 50.9 m3/s, respectively (Figure 17.2). Before dam construction, the annual flood peak was four times the average flow, which has been greatly reduced during the past 15 years. The mean, maximum and minimum water temperatures observed at this station are 13, 21 and 6 C, respectively. The annual temperature amplitude was reduced from 20 C before the mid-1980s to 10 C today. The construction of large dams (Devege¸cidi, Kralkızı, Dicle and Batman) built within the scope of the GAP project now regulate the flow in the Tigris basin. The mean annual discharge and yield of the Tigris basin is 21.3 km3 and 13.1 L/s/km2, respectively (Figure 17.2). Long-term (1968–1993) records near the Turkish–Syrian border (370 m asl, area: 38 280 km2) shows mean, minimum and maximum flow rates of 537, 34 and 4450 m3/s, respectively. The mean, maximum and minimum water temperatures observed at this station are 16, 30 and 0 C. Long-term temperature data show no trends during the last three decades. Turkey contributes 89% to the total discharge of the Eurphrates River at the mouth but only 50% to the Tigris discharge. The Euphrates is thus more vulnerable to the supply of water for downstream countries (Syria, Iraq). The Coruh ¸ basin is still largely unregulated, although several feasibility projects for hydropower production are currently being undertaken. The Coruh ¸ has a high hydropower potential (9 109 kWh), making it one of the most important rivers in northeastern Turkey. Eleven dams are planned for the river, of which two dams (Bor¸cka and Muraltı) are almost completed and the Deriner dam is operational (Ertun¸c & Cetin ¸ 2007). The mean annual discharge and yield of the basin are 6.3 km3 and 10.1 L/s/km2, respectively. Based on long-term records (1967–2002) measured near the Turkish–Georgian border (57 m asl, area: 19 654 km2), the mean, minimum and maximum discharge

660

rates are 210, 38 and 1211 m3/s, respectively (Figure 17.2). The mean, maximum and minimum water temperature is 10, 24 and 3 C. Long-term records show that peak flows exceeding eight times the annual mean occur about every 6 years. Long-term temperature records indicate a decrease in the maximum and an increase in the minimum water temperature since the early 1990s. The hydrology of the Aras basin in Turkey is mostly unregulated. The large Arpa¸cay dam is located along a major tributary. The Aras has a snowmelt dominated flow regime with a mean annual discharge and yield of 4.6 km3 and 5.3 L/s/km2, respectively. Long-term (1967–1993) records measured at 1140 m asl (area: 8873 m2), show a mean, maximum and minimum discharge of 58, 513 and 8 m3/s, respectively. The mean, maximum and minimum water temperatures at this station are 7.8, 21 and 3.0 C. Annual peak flow is 10 times that of the average discharge. A long-term temperature trend indicates a decrease in the maximum water temperature while the minimum temperature remains relatively constant.

17.9. WATER QUALITY The water quality of Turkish rivers shows a wide variability, being influenced by both natural and anthropogenic factors. Natural factors affecting the water quality of these rivers include the precipitation to evapotranspiration ratio, the annual distribution and type of precipitation, topography that determines water residence time and erosion rate, and land use that affects vegetation type and cover. Anthropogenic influences have become more evident since the 1970s, particularly in regions where agricultural and industrial water use had increased. Rivers most susceptible to natural pollution include the Kızılırmak, Greater Meander and Coruh. ¸ Tertiary evaporite deposits in the upper Kızılırmak basin cause relatively high chloride and sulphate concentrations in the river that are diluted downstream. Because of active tectonics, Turkey has numerous hydrothermal springs throughout the country. While spring effluents adversely affect water chemistry, oxidation and sorption to sediments and dilution from tributaries reduce these effects. A similar process also is observed in streams affected by acid mine drainage. Anthropogenic pollution of Turkish rivers is caused mainly by domestic (sewage) and industrial waste waters, and from irrigation return waters. While in large cities administrated by metropolitan municipal authorities domestic waste water is treated before being released into nearby streams, facilities for water treatment do not occur or are out of use in many smaller towns. The effects of untreated domestic waste waters on rivers decrease downstream because of the natural breakdown of chemicals and dilution from tributaries. Despite sewage treatment facilities, domestic pollution seems to be increasing in rivers that flow near _ large cities, such as Ankara, Izmir and Eski¸sehir. Increasing

PART | I Rivers of Europe

industrial pollution is observed in streams near heavily in_ _ dustrialized areas of large cities such as Izmit, Izmir and _Istanbul. Although strict laws to protect water resources have been in place for decades, monitoring networks have not been established to enforce the operation of treatment systems. Increasing water use for agriculture has begun to affect stream water quality in some parts of the country. While intensive fertilizer use appears to have little influence on streams adjacent to farmlands, nitrogen compounds in underlying aquifers are increasing in some areas. These increases in nitrogen compounds in groundwater have yet to be detected in streams, but are likely to appear in the future. Further, because increasing groundwater use for agriculture (75% of the national reserve) is rapidly depleting this resource, new measures such as drip irrigation are now being favoured by governmental organizations. These measures are expected to reduce the pressure on surface and groundwater resources, in terms of quantity and quality. Presently, water pollution is highest in small streams of the coastal plains where year-long cultivation is common because of the favourable climate. In these areas, extensive use of agrochemicals, particularly in greenhouses, influences soil and water quality, although the number and scope of studies to determine the magnitude of those problems is limited. Overall, surface and groundwater pollution in Turkey is increasing, yet not fully appreciated. Other factors affecting the water quality in rivers include the construction of large dams and climate change. Regulating the natural flow regime of rivers by dams traps sediments, increases water residence time for sorption and degradation of chemicals and reduces the annual variation in water temperature. Climate change also seems to be affecting the rivers of Turkey. Field observations in many basins indicate a slight rise in water temperature. While the variation in annual precipitation is still within the longterm range, the relative contribution of snow to total annual precipitation has been reduced. Visual observations indicate a reduction in the amount of snowfall. Permanent snowfields at high elevations are more and more contracting or disappeared completely over the past decades. Such changes in the snow regime lowers groundwater recharge, which is important for sustaining surface flows in streams in summer, particularly in karstic basins such as in the Taurid Mountains. The increase in periodic rainfall has also increased the frequency of episodic floods over the past few decades. Starting in the 1970s, systematic water quality measurements have been conducted by associated governmental au_ in many rivers of Turkey. These thorities (i.e. DSI_ and EIE) systematic measurements include some physical parameters (temperature, conductivity, pH), major ions (Ca, Mg, Na, K, Cl, SO4, alkalinity) and other constituents (boron, sodium absorption ratio, residual sodium carbonate, sediment load), but not other environmentally important parameters such as nutrients, agrochemicals and trace elements. Long-term measurements recorded at the most downstream water

Chapter | 17 Rivers of Turkey

quality stations in major river basins show that minimum, maximum and mean values are highly variable. For example mean water temperature among stations varies between 7.8 and 17.2 C, with an overall mean temperature of 13.4 C (Table 17.1). The lowest mean stream water temperature occurs in the Aras (7.8 C) and eastern Black Sea basins (8.5 C), and highest values are found in the Asi (17.2 C) and Ceyhan (16.6 C) basins. Stream water temperature is controlled by latitude and mean basin elevation. Similar variation is also observed in pH (range 4.6–10.8, mean: 8.1) and conductivity (range 38–4520 mS/cm, mean: 1418 mS/cm) values. The mean pH in rivers of Turkey is typical of freshwaters in equilibrium with atmospheric carbon dioxide. The long-term mean pH ranges between 7.8 (eastern Black Sea basin) and 8.4 (north Aegean basin). The low pH observed in streams of the eastern Black Sea basin is probably due to extensive soil organic activity from the moist climate (precipitation 2000 mm). While in many river basins, the long-term mean low pH value is around 7.0, lowest values are found in the eastern Black Sea (5.7), Coruh ¸ (4.6) and Aras (5.1) basins. These low values are associated with the drainage of acid mine deposits that are common in these regions. In all river basins, except the Konya closed basin in Central Anatolia, the long-term mean alkalinity is below 5 mg HCO3 /L. Alkalinity varies between 0.0 and 26.1 mg HCO3 /L. High alkalinity values (25 mg HCO3 /L) observed in the Konya closed basin are associated with the prevalence of carbonate bedrocks, low discharge rates and high summer temperatures that force carbonate precipitation. A similar process exists in the Ergene basin where temperature to water mass ratio favours high alkalinity. While the long-term mean conductivity is 600 mS/cm for rivers of Turkey, there is a remarkable variation among streams. Highest conductivity values are found in the Ergene and Kızılırmak basins (1400 mS/cm), mostly as a result of salinization (in Ergene) and dissolution of evaporitic (gypsum and halite) bedrock (parts of the Kızılırmak). During high flow, conductivity is in general <300 mS/cm. Long-term low mean conductivity values are found in the eastern Black Sea basins (38 mS/cm), Coruh ¸ (122 mS/cm) and Aras (58 mS/ cm), mainly because of the underlying volcanic bedrock. In terms of major ions, CaCO3 waters dominate most rivers. In some rivers such as in the Ergene, Smaller Meander, Kızılırmak and Afyon basins, NaCl facies are dominant, particularly during the dry season. This shift in water type is associated mostly with the extensive return of irrigation waters, dissolution of evaporitic minerals, and the natural or anthropogenic discharge of hydrothermal waters. Many streams in Turkey fall into the C2S1 salinity class, indicating moderate total dissolved solid concentration and low salinity risk. Eastern Black Sea rivers that belong to the C1S1 class have the best water quality in terms of major ions. Streams in the Ergene, Smaller Meander, Greater Meander, Kızılırmak and Asi basins are C3S1 types, indicating low salinity risk but high total dissolved solid concentrations.

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Depending on topographic, geomorphic and geologic conditions, the mean sediment yield is 155.3 tons/year/ km2, while the minimum and maximum values are 9.0 and 611.0 tons/year/km2, respectively (Figure 17.3). In general, sediment yields are controlled primarily by the mean elevation of the respective basin. Low sediment yields (<100 tons/year/km2) are found in western Turkey (e.g. Ergene, Smaller and Greater Meander) where the mean elevation is relatively low, or in closed basins (e.g. Afyon, Konya and Van Lake) with a relatively flat topography. Moderate sediment yields are observed in the Sakarya, western Black Sea, Ye¸silırmak, Kızılırmak, Seyhan and Ceyhan basins). Rivers in the eastern part of the country have the highest sediment yields. Highest sediment yields are found in the Tigris (611 tons/year/ ¸ (401 tons/year/km2) and Euphrates (357 tons/ km2), Coruh 2 year/km ). Because of the widespread prevalence of hydrothermal springs and associated deposits throughout Turkey, stream water quality is influenced by elevated boron concentration, an element harmful for plants. Boron levels are <0.2 mg/L in many basins, but concentrations as high as 0.5 mg/L have been recorded in waters of the Gediz, Smaller Meander, Greater Meander and Kızılırmak basins. High boron levels (1 mg/L) have been observed in the Susurluk basin south of the Marmara Sea where the main river passes through ore (Colemanite) deposits. In the early 1990s, the Ergene River shifted from a CaCO3 dominated river type to a NaCl dominated type probably because of intense agricultural and industrial activities. The mean, maximum and minimum pH is 8.1, 10.8 and 7.1, respectively. During the same period, the mean, maximum and minimum values of alkalinity (mg/L HCO3) and conductivity (mS/cm) were 6.8, 22.7, 0.0 and 1396, 4520, 302, respectively. Based on observations at Station-105, the annual sediment load carried by the river is 241 000 tons or 25 tons/km2. Records at Station-706 (1985–2002) indicate a CaCO3 type water in the Great Meander River, being representative of most Aegean rivers. The mean, maximum and minimum values of pH are 8.3, 8.8 and 7.5, respectively. For the same period, the mean, maximum and minimum values of alkalinity (mg/L HCO3) and conductivity were 5.6, 12.3, 1.4 and 1216, 2200, 491 mS/cm, respectively. High conductivity values observed in the river are mostly due to impounding of stream water during summer. Based on records at Station706, the annual sediment load carried by the Great Meander is 397 781 tons (41 tons/km2). The low topographic gradient of the Aegean basins seems to be the reason for the relatively low sediment yield. In the Sakarya basin, records at Station-1243 (1983– 2002) indicate a CaCO3 type water with mean, maximum and minimum pH of 8.1, 9.2 and 7.4, respectively. During the same period, the mean, maximum and minimum values of alkalinity (mg/L HCO3) and conductivity (mS/cm) are 4.1, 6.8, 1.0 and 670, 994, 127, respectively. Based on long-term

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PART | I Rivers of Europe

FIGURE 17.3 Long-term sediment load data for selected Turkish Rivers (tons per day).

records at this station, the mean annual sediment load carried by the river is 3.04 million tons (280 tons/km2). In a typical year, dry and wet period sediment loads vary from 40 000 to 140 000 tons/year.

Long-term records of the Ye¸silırmak (Station-1413) indicate a CaCO3 water type where mean, maximum and minimum pH is 8.1, 10.3 and 6.9, respectively. Long-term mean, maximum and minimum values of alkalinity (mg/L HCO3)

663

Chapter | 17 Rivers of Turkey

and conductivity (mS/cm) at this station are 4.8, 11, 0.1 and 614, 2250, 255, respectively. At Station-1413, the annual sediment load is 2.87 million tons (150 tons/km2). Long-term records at Station-1503 indicate a CaCl2/ NaCl type water for the Kızılırmak River, in part due to leaching of evaporitic bedrock and strong evaporation. Mean, maximum and minimum pH of 8.0, 8.8 and 7.2, respectively, occur in the river. Long-term mean, maximum and minimum values of alkalinity (mg/L HCO3) and conductivity (mS/cm) at this station are 2.8, 11.2, 0.6 and 1406, 1830, 178, respectively. At Station-528, the annual sediment load is 4.47 million tons (146 tons/km2). Representative for the eastern Mediterranean basins, records of the G€ oksu River at Station-1714 (1983–2002) indicate a CaCO3 type water with mean, maximum and minimum pH of 8.1, 8.6 and 7.2, respectively. During the same period, the mean, maximum and minimum values of alkalinity (mg/L HCO3) and conductivity (mS/cm) were 2.9, 5.1, 0.8 and 332, 2285, 204, respectively. The maximum conductivity value observed at this station is most probably an outlier. The annual sediment load carried by the G€oksu at Station-1714 is 1.7 million tons (176 tons/km2). Based on long-term records (1970–2002), the Seyhan River is dominated by CaCO3 type water (pH: 7.1–9.5, mean: 8.1). During the same period, the mean, maximum and minimum values of alkalinity (mg/L HCO3) and conductivity (mS/cm) were 2.9, 5.6, 0.4 and 383, 848, 188, respectively. Based on records at Station-1818, the annual sediment load carried by the river is 2.096 million tons (151 tons/km2). Records at Station-2004 (1984–2002) indicate a CaCO3 type water in the Ceyhan River. The mean, maximum and minimum pH was 8.2, 8.6 and 7.0, respectively. During the same period, the mean, maximum and minimum values of alkalinity (mg/L HCO3) and conductivity (mS/cm) were 3.8, 6.5, 1.5 and 467, 755, 263, respectively. Records at Station2004 show that the annual sediment load carried by the river is 2.22 million tons (185 tons/km2). Long-term data (1965– 1999) indicate reduced sediment transport rates after the mid-1980s due to flow regulation and retention of sediments behind dams. More than one million people discharge their untreated waste water into the Asi River, although there are ongoing treatment plant projects for the city of Antakya and several ¨ zdilek & Sang€ smaller urban areas (O un 2007). Due to intense agriculture, nitrate and chloride concentrations are high in the river. For example specific conductance increased from about 790 to 1200 mS/cm from 1984 to 2002. Further, many industrial complexes discharge 500 000 m3 of waste water into the river. Based on long-term records (1977–1999) at Station2170, the Euphrates River has a CaCO3 type water with a mean, maximum and minimum pH of 8.1, 8.3 and 7.5, respectively. For the same period, the mean, maximum and minimum values of alkalinity (mg/L HCO3) and conductivity (mS/cm) were 2.8, 5.6, 1.4 and 361, 546, 257,

respectively. Water chemistry measures show little problems with salinity except on some farmlands. The annual sediment load carried by the river is different before and after the mid-1980s. Prior to the construction of dams, sediment loads were as high as 700 000 tons/day were observed at Station-2170, but loads were reduced to <100 000 tons/day after regulation. The overall mean annual sediment load of the river during the recording period was 2.87 million tons (357 tons/km2). Long-term (1972–2002) water quality data for the Tigris basin are based on data from Station-2605 just downstream of Diyarbakır, the largest city in the region. Records at this station indicate a CaCO3 type water with a mean, maximum and minimum pH of 8.0, 9.6 and 6.5, respectively. For the same period, the mean, maximum and minimum values of alkalinity (mg/L HCO3) and conductivity (mS/cm) were 3.3, 8.2, 0.1 and 459, 823, 250, respectively. The annual sediment load carried by the river at Station-2605 is 22.56 million tons (611 tons/km2). Based on long-term records (1971–2002) at Station2315, the Coruh ¸ River is a CaCO3 type water with a mean, maximum and minimum pH of 7.9, 8.8 and 4.6, respectively. The lowest pH value was observed in August 1985 and may be associated with an episodic acid mine drainage. During the same period, the mean, maximum and minimum values of alkalinity (mg/L HCO3) and conductivity (mS/cm) were 2.1, 5.5, 0.3 and 293, 925, 122, respectively. Based on observations at Station-2315, the annual sediment load carried by the river is 7.15 million tons (401 tons/km2). Long-term (1984–2002) water quality data of the Aras basin is available for Station-2418 on the Arpa¸cay River. The stream is dominated by a CaCO3 type water with a mean, maximum and minimum pH of 8.1, 9.2 and 5.1, respectively. During the same period, the mean, maximum and minimum values of alkalinity (mg/L HCO3) and conductivity (mS/cm) were 2.9, 6.9, 0.1 and 310, 559, 58, respectively. Based on records at Station-2402, the annual sediment load carried by the Aras is 2.71 million tons (306 tons/km2).

17.10. BIODIVERSITY Turkey connects two continents and, consequently, has served as a major migration and mixing corridor for plants and animals. Although Turkey can be considered as part of the Palaearctic region, it contains many Oriental and Aethiopian faunal and floral elements that immigrated from the South after the Pleistocene (Kosswig 1955). On the other hand, species from the Caucasus, Alps, Balkans and even from Central Europe moved southwards after the last glaciation (e.g. Salamandra salamandra, Triturus vittatus, but also freshwater fish like Rutilus, Alburnus and Cobitus). Other intruders of northern origin, the Angara elements, emigrated from the cold steppes of Eastern Sibiria. Turkey is rich in biodiversity, including a high proportion of endemic species. In particular, southern and southeastern

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Anatolia contains several local biodiversity hotspots within the large Mediterranean global hotspot area (Yılmaz 1998; Medail & Quezel 1999). Steep topographic gradients cause a great variety of climate and landscape types. For example, the Seyhan and Ceyhan Rivers originate in the Taurid Mountains and flow into the Mediterranean Sea forming a large alluvial plain. The mountains and sea are connected over short distances, as are continental and Mediterranean climates. Saltmarshes, lagoons, dunes, riverbeds and coastal woodlands create a diverse patchwork of contrasting landscape elements. Seven major ecoregions can be distinguished that mainly reflect climatic variation. The larger river basins such as the Kızılırmak, Sakarya and Euphrates drain five or even more ecoregions (Table 17.1). We provide below a short overview of the species diversity in the different catchments. Repeated citations to data sources are avoided but a complete list is provided at the end (for more details see Akbulut 2004). For fish, recently published checklists are taken into consideration (Kuru 2004; _ Erk’akan et al. 2002; TCV ¸ 2005; Innal & Erk’akan 2006; Erk’akan et al. 2007). Amphibia data are from Demirsoy (2006). Some information on climate and ecoregions were taken from Atalay (1997, 2002). Sediment information is _ (2000, 2003) and from http://www.dsi.gov.tr/. from EIE Turkey has a rich macroinvertebrate fauna, although limited information on their distribution and composition is available. Plecoptera are represented by 93 species and 9 subspecies, belonging to 19 genera (Kazancı 2008). Trichoptera have been studied in great detail by Sipahiler & Malicky (1987) and Sipahiler (1989, 1994, 1996, 1999, 2000) and the known number of Trichoptera is 402 species (Sipahiler personal communication). The presently known number of Ephemeroptera species is between 100 and 120 (Kazancı 2001; Tanatmı¸s 2002). According to G€ ulen et al. (2002), the number of Ostracod species is 149, with 66 freshwater and brackish species and 83 marine species. Odonata are represented by 37 genera, 111 species and 26 subspecies (Demirsoy et al. 1995). The number of Hydrachnella (Acari) is 144 of which 50 species are reported from inland waters ¨ zkan 2002a,b). The species number of Chironomidae is (O given as 195 (¸Sahin 2002). The Simulidae are represented by 34 species (¸Sirin 2002). Oligochaeta species recorded from different aquatic ecosystems in Turkey is 94; 1 lumbriculid, 1 haplotaxid, 46 naidids, 38 tubificids, 6 enchytraeids, 1 lumbricid and 1 criodrilid (Arslan 2006). About 244 gastropods have been identified. Out of these, 73 species occur both in freshwater and brackish water (Yıldırım 2002). The number of currently recognized taxa reached 80 (Yıldırım et al. 2006). In any case, we can expect that the number of species in the individual groups is much higher than actually reported. The Meri¸c River (and the Ergene River) contains 26 fish species, 20 species are native. Ten amphibia species are listed for this river and all of them are listed as threatened. Rana ridibunda ridibunda is a common species in this area but its population is decreasing due to hunting pressures to export the meat to other countries, especially during the

PART | I Rivers of Europe

¨ terler et al. (2003, 2004) studied the reproduction period. O epipelic algae and diatoms along the Tunca River, a major tributary of the Ergene. Ye¸silmen & Kırgız (1996) investigated the amphipod fauna in Kırklareli City, and Kavaz et al. (2003) studied the distribution of macroinvertebrates along the Tunca River. G€uher (1999) reported 32 cladocerans, 19 copepods from Erikli, Hamam and Pedina Lakes in the Igneada/Kırklareli region in 1993–1994. Among them, Ceriodaphnia megops (Cladocera) was first recorded for Turkey. A total of 47 different lakes, ponds, streams, rivers and other bodies of the Thrace region were surveyed from 1996 to 1998. In total, 39 zooplankton species were identified with 10 species being new to the region (G€uher 2000). Camur ¸ & Kırgız (2000) identified 4 isopods from 60 different localities ¨ zkan & Kırgız (1995) studied the Chironoin the region. O ¨ zkan (2002a,b) identified in 1995– midae in the region, and O 1996 five species new to the Turkish fauna. They included Corynoneura scutellata (Ergene River), Beckidia zabolotzkii (Meri¸c River), Robackia demeijerei (Meri¸c and Sazlıdere Rivers), Parachironomus arcuatus (Meri¸c and Ergene Rivers) and Parachironomus longiforceps (Meri¸c River). The Gediz River contains 33 fish species, 24 are native, 3 are introduced and 6 are endemic (Capoeta bergamae, Chondrostoma holmwoodii, Cobitis fahirae, Cobitis vardarensis kurui, Knipowitschia mermere and Barbatula bergamensis). Nine amphibians are listed for this river, all of them are considered as threatened. Gezerler and Aysel (1999) identified 153 algae taxa in the Gediz Delta; 44 were Cyanophyta; 65 Bacillariophyta; 36 Chlorophyta and 8 Euglenophyta. Ustaoglu et al. (1999) found 10 species of zooplankton in the river. The Smaller Meander River contains 28 native, 2 introduced and 7 endemic fishes (Capoeta bergamae, Cobitis fahirae, C. vardarensis kurui, Knipowitschia longecaudata, Petroleuciscus (Leuciscus) smyrnaeus Knipowitschia ephesi and Barbatula germencica). Seven amphibians are listed, six of them are threatened and one species is listed as rare (S. salamandra salamandra). Aysel et al. (1998) recorded 137 algae taxa in the delta of the Smaller Meander (Kazang€ ol), with 20 new records for Turkey. Kazancı et al. (1999) conducted a study on phytoplankton in the river and found Cyclotella ocellata to be dominant, while Cyclotella, Nitzschia, Coelastrum and Scenedesmus were dominant in the Greater Meander River. The Greater Meander River has a rich fish fauna with 37 native, 4 introduced and 12 endemic species (Aphanius anatoliae anatoliae, Aphanius chantrei, Capoeta bergamae, Cobitis vardarensis kurui, C. fahirae, Barbatula germencica, Barbatula cinica, Chondrostoma holmwoodii, Hemigrammocapoeta kemali, P. (Leuciscus) smyrnaeus, Pseudophoxinus meandricus and Pseudophoxinus meandri). The Gediz River and its tributaries (G€uzelhisar and Bakır¸cay) are the most important rivers in the northern Aegean region. In a detailed survey by Balık et al. (1999), 88 aquatic species were identified including 12 Rotifera, 5 Gastropoda, 2 Lamellibranchiata, 9 Oligochaeta, 2 Hirudinea, 18

Chapter | 17 Rivers of Turkey

Cladocera, 2 Ostracoda, 6 Copepoda, 2 Decapoda, 1 Isopoda, 2 Ephemeroptera, 3 Chironomidae, 21 fishes, 1 amphibian and 3 reptiles. S ¸ ahin (1987) described the Chironomidae fauna from 312 different sampling points in western Turkey. A total of 70 species were recorded for the first time for Turkey and the species Ablabesmyia aequidensi S ¸ ahin, Potthastia alternis S ¸ ahin and Thienemanniella brevidensi were new records for science. Ustao glu et al. (1996) recorded the Rotifera fauna and Ustao glu et al. (1997) the Cladocera and Copepoda fauna of the G€ um€ uld€ ur stream. Gezerler and Aysel (1999) recorded 153 phytoplankton species, with Bacillariophyceae being dominant. The Sakarya contains at least 72 fish species; 63 are native, 5 are introduced and 4 are endemic (Aphanius anatoliae anatoliae, Aphanius villwocki, Cobitis simplicispina and Seminemacheilus lendli). Thirteen amphibian species are listed for the Sakarya, 11 are threatened or near threatened, one species is rare and two subspecies are endemic (Triturus vulgaris kosswigi, Bombina bombina arifiyensis). Demirdizen (1996) identified the gastropods of the basin. Cabuk ¸ et al. (2004) investigated the composition, abundance and seasonal distribution of the gastropod fauna in the upper Sakarya River and related it to environmental conditions. They found 16 species with abundances being positively correlated to temperature and dissolved oxygen. Arslan & S ¸ ahin (2004) identified 34 aquatic Oligochaeta species, with the genera Paranais, Spericaria and Allonais being new for Turkey. The Simuliidae are represented by 25 species (¸Sirin &S ¸ ahin 2005). Atıcı & Yıldız (1996) identified 103 diatoms. Yıldız (1987a, b) recorded 125 algal species from the Porsuk ¨ zkıran (1994) River, a tributary of the Sakarya. Yıldız & O found Cyclotella meneghiana and C. ocellata as important species in the main stem and tributaries. Other common algae were Synedra ulna, S. capitata, Cocconeis placentula, Diatoma vulgare, Achnanthes lanceolata, Amphora ovalis and Cymbella lanceolata. Because the Porsuk is heavily polluted by industrial and domestic waters, Cyanophyceae were predominant (Yıldız 1987b). The Ye¸silırmak River contains 53 fishes, including 49 native, 3 introduced and 1 endemic. Nine amphibians are listed and all are threatened (Demirsoy 2006). Duran (2004) studied the growth rate of Gammarus pulex (L.) in the river. Soylu & G€ on€ ulol (2003) investigated the seasonal dynamics of the phytoplankton, finding Bacillariophyta as the dominant plankton group. Pabu¸ccu and Altuner (1999) studied the algae of the river in Tokat city. In addition, there are data available on the phytoplankton from the Suat U gurlu and Hasan U gurlu reservoirs (G€ on€ ulol & Obalı 1998a, 1998b). In Suat U gurlu Lake, the seasonal variation in toxic micro-algae that produce phytoplankton blooms was studied. Pediastrum simplex, Pandorina morum and Ceratium hirundinella, which consume high levels of phosphate, produced blooms in summer, whereas winter blooms were formed by Asterionella formosa, Cyclotella planktonica and Melosira granulata, which require higher nitrate concentrations.

665

In total, 60 fishes are listed for the Kızılırmak River, of which 52 species are native and 5 are endemic (A. chantrei, Aphanius danfordi, C. simplicispina, S. lendli and Barbatula kosswigi). Nine amphibians are listed and all of them are threatened. Studies on economic fish stocks in the Kızılırmak basin have been carried out by Erk’akan & Akg€ul (1986). Ekmek¸ci (2002) studied the production of Capoeta tinca in the Kızılırmak basin, and related it to the physical and chemical characteristics of the river, in particular to its high natural salinity. Although Kızılırmak is the longest river in Turkey, few studies on primary producers exist. Algae communities have been studied in the cities of Sivas and Kayseri ¨ zkıran 1991; Hasbenli & Yıldız 1993; Dere & (Yıldız & O Sıvacı 1994). The diversity and density of epipelic, epilithic and epiphytic algae were quite similar (Hasbenli & Yıldız 1993). A. ovalis, Cymbella ventricosa, D. vulgare, Navicula cryptocephala and Nitzschia palea were the most common epipelic species followed by Chlorophyceae, although the density of Cyanophyceae was highest. K€uc¸ €uk et al. (2007) studied the fish fauna of the G€ oksu River. In total, 23 native and 3 introduced fish species belonging to 7 families and 1 endemic species Seminemacheilus ispartensis were identified. Aya¸s & Kolankaya (1996) investigated the heavy metal concentration in benthic sediments and soil samples and found that Hg and Pb levels were high and accumulated in the food chain. Water, sediments and soil samples in the G€oksu Delta contained high levels of Hg and Pb. The level of Hg in various environments was higher than the level of Pb. Nickel levels were found high in water, sediments and soil samples, but nickel did not accumulate in the organisms. The concentrations of Cd and Cr were below detection level. Aya¸s et al. (1997) determined organic pesticide residue in various environments such as waters, sediments and soils and in organisms such as blue crabs (Cullinectes supidus), fish like grey mullet (Mugil cephalus) and carp (Cyprinus curpio) and waterbirds like coot (Fulica atra), mallard (Anas plutyrynchos) and little egret (Egretta gurzettu) from 1991 to 1993 at G€oksu DeltaTa¸sucu. It was observed that various environments and organisms in G€oksu Delta were contaminated by 13 different organic pesticides and their residues. Ergene et al. (1999) investigated the chromosome structure of Clarias lazera living in wetlands in the G€oksu River and found 25 systematically important meristic and morphometric characters of C. lazera. Ergene et al. (2007) studied nuclear abnormalities in peripheral erythrocytes of three fish species from the G€oksu Delta (Turkey) and genotoxic damage in relation to water pollution. The results of this study indicate that the lagoons of G€oksu Delta contaminated with genotoxic pollutants and that the genotoxicity is related to the agricultural activities and to the discharge of anthropogenic waste waters. A total of 33 fishes were listed in the Seyhan River, including 29 native, 3 introduced and 4 endemic species. Eight amphibians were listed and two of them (Rana holtzi, T. vittatus cilicensis) are endemic. G€oksu et al. (1997) identified 17 Rotifera and 9 Cladocera from the river. Kandemir

666

et al. (1994) identifed 100 algae in the river at Adana, with a high proportion of Bacillariophycea. Alada g et al. (2006) studied the zooplankton fauna of the Catalan ¸ reservoir, reporting eight species of Cladocera and two species of Copepoda. In total, 39 fishes are listed for the Ceyhan River, including 35 native, 3 introduced and 2 endemic. Eight amphibians are listed, six as threatened. T. vittatus cilicensis is endemic to the Ceyhan and S. salamandra salamandra is listed as very rare. Populations of Salmo trutta macrostigma were investigated in the Fırnız stream, a tributary of the Ceyhan (Kara & Alp 2005). The age distribution ranged between 0 and 9 years. The condition factor of brown trout ranged from 1.13 to 1.85. A total of 15 prey groups were identified in the diet of brown trout. Bozkurt et al. (2002) reported 36 rotifer species for the Asi River. G€ oksu et al. (2005) reported 15 species of Cladocera and 7 species of Copepoda in the river. Among them, Bosmina longirostris, Nitocra hibernica and Cyclops vicinus were common. S ¸ en et al. (1996) studied the diatoms of the Asi River. Species of Navicula and Nitzschia were abundant. In general, epipelic algae had higher abundances in the upper river while epipsammic algae were more abundant in the lower river. In total, 49 fishes are found in the Euphrates River, including 42 native, one introduced and 6 endemic species (Erk’akan et al. 2002; Kuru 2004; TCV ¸ 2005; Erk’akan et al. 2007). Nine amphibians are listed with five species being threatened. Neurergus strauchii strauchii and Neurergus strauchii barani are endemic amphibians (Demirsoy 2006). Kuru (1975) studied the fish fauna of the Euphrates–Tigris, Kura–Aras, Lake Van and Black Sea River basins. The zebra mussel, Dreissena polymorpha Pallas, is one of the most important fouling organism in these freshwater ecosystems. Recently, this species, although native to Turkish freshwaters, has caused important technical and economic damage to the Atat€ urk dam and other hydropower plants along the river. Tosuno glu et al. (1999) investigated the pollution of the Karasu River, the most important river of the Erzurum plain (headwaters of the Eurphrates), and found it heavily contaminated by industrial waste waters. Saler et al. (2000) studied the seasonal variation of rotifers in the K€ om€ urhan region of the Euphrates. Akbulut & Yıldız (2005) identified 65 rotifer species from 17 different freshwater sites in the Euphrates basin, 9 were new for Turkey. Saler and S ¸ en (2001) studied the seasonal dynamics of rotifers in the Zıkkım River that flows into Lake Hazar. Altuner & G€ urb€ uz (1991) studied the epipelic algae of the Karasu River in the basin. They identified 145 algae with Cymbella affinis, C. ventricosa, Navicula cryptocephala, Synedra ulna, Nitzchia palea and Amphora ovalis as most common. According to Cetin ¸ and S ¸ en (1998), a total of 104 diatom taxa can be found. Cyclotella ocellata Pantocksek, C. k€ utzingiana Thwaites (Centrales), Asterionella formosa Hassall and Fragilaria crotonensis Kitton (Pennales) were the most abundant planktonic diatoms in

PART | I Rivers of Europe

Keban reservoir. The seasonal growth of diatoms showed a clear relationship with temperature and silica concentration in the lake. G€urb€uz and Kıvrak (2002) used epilithic diatoms to evaluate the water quality in the Karasu River. A total of 55 fishes are known from the Tigris River, including 46 native, 2 introduced and 7 endemic. Six amphibians are listed, of which 5 species are threatened and one (Neurergus crocatus) is rare (Demirsoy 2006). Yılmaz & Solak (1999) investigated the feeding behaviour and seasonal dynamics of Capoeta trutta (Heckel 1843) in the Tigris River. S ¸ ahin (1980) studied the Elazıg and found only 3 subfamilies of Chironomidae. In total, 31 genera and 41 species were identified, with Ablabesmyia ya1vacii, Paratendipes demirsoyus, Thienemanniella munzuri and Cardiocladius ekingennis being new species to science. The aquatic ¨ nt€ Oligochaeta have almost been neglected in Turkey. O urk & Arslan (2003) collected oligochaetes from the G€um€ us¸ River and its tributaries, with Rhyacodrilus coccineus being a new record for Turkey. The algae of the Tigris have not yet been studied, except for Devege¸cidi reservoir. The water of this lake comes from the Cay, ¸ Hatun and Ay¸se Rivers, all tributaries of the Tigris; and a total of 112 taxa belonging to 5 divisions were identified, with 29 species of Cyanophyta, 5 Euglenophyta, 45 Chlorophyta, 5 Pyrrhophyta and 28 Bacillariophyta (Baykal et al. 2004). The epilithic algae of Zap Suyu (tributary of Tigris) showed Rhopalodia gibba was most abundant (Akbulut A. personal comunication). Bekleyen (2006) reported 17 cladocerans and copepods from Devege¸cidi Lake. In total, 16 fishes are listed for the Coruh ¸ River, of which 14 are native and 2 species are introduced. The number of fish species changed to 18 by the addition of two new Capoeta species (Turan et al. 2006a, 2006b) Ten amphibian species are recorded and all are threatened (Demirsoy 2006). Yıldırım and Aras Sıtkı (2000) examined 913 specimens of C. tinca (Heckel 1843) in the Oltu Stream, Coruh ¸ basin, from 1994 to 1996. Their age ranged from 1 to 7 years. Males reached sexual maturity at age two and females at age three. They spawned between May and July when the water temperature averaged 16 C. Fecundity was 5561 eggs per female and was related to fork length, total weight, age and gonad weight. Yıldırım et al. (2001) examined the age, growth and reproduction of 627 barbels (Barbus plebejus escherichi Steindachner 1897) in the Oltu, a tributary of the Coruh. ¸ Barbels reached sexual maturity at fork lengths between 11.5 and 13.8 cm (2–3 years old, males) and between 13.7 and 16.0 cm (3–4 years old, females). Females produced between 1260 (3rd age group) and 8450 (7th age group) eggs per female. Spawning occurred between May and July when the water temperature was between 14 and 19 C. The fatty acid (FA) composition of wild Salmo trutta labrax (Pallas 1811) was studied in the Kazandere River in the Coruh ¸ region. The results showed that the highest total saturated fatty acid content was in muscle (37.2%), while the lowest value was in eggs (27.1%) (Aras et al. 2003). Atıcı & Obalı (1999, 2000) recorded 106 algae species from the

Chapter | 17 Rivers of Turkey

upper Coruh. ¸ The benthic algae community was dominated by Diatoma hiemale var. mesodon, Ceratoneis arcus, Fragilaria capucina, Synedra ulna, Gyrosigma acuminatum, Navicula lanceolata, Gomphonema parvalum, Hantzscnia amphioys, Nitzschia linearis and N. hungarica. Thirty fish species are listed for the Aras River, including 28 native, one introduced and one endemic species. Six amphibians are listed and all are threatened (Demirsoy 2006). The salmonids of the Coruh ¸ and Aras basins were first investigated by Aras (1974). The ecology of Barbus plebejus escherichi in the Coruh ¸ River was studied by Solak (1978, 1988). The ecology of Barbus mursa mursa and Barbus plebejus lacerta in the Kura-Aras basin was studied by Solak (1989a, 1989b). The age, growth and reproduction of Acanthalburnus microlepis was studied in the Ya gan region of the Aras River (T€ urkmen et al. 2001). Capoeta capoeta capoeta was studied in detail by Yanık et al. (2002). Altuner (1988) reported 113 diatoms from the Aras. Achnanthes affinis and Surirella ovata decreased markedly in summer, Cymbella affinis and Gomphonema olivaceum decreased slightly, but Navicula cryptocephala dominated in summer. The diatoms of Lake Cıldır, ¸ on the tributary Arpa¸cay, were studied by Akbulut & Yıldız (2002). The most dominant taxa were Cyclotella meneghiniana, Aulacoseria granulata, Melosira varians and Navicula spp.

17.11. MANAGEMENT AND CONSERVATION During the last several decades, accelerating industrial, economic and agricultural development, along with an increasing population and internal migration to cities, has created a tremendous pressure on water resources and associated aquatic ecosystems. These developments not only increased water demands but also caused major water pollution parallel with the amount of use. Although attention has been paid to the proper management and conservation of water resources in Turkey since the late 1950s, many attempts have not been succesfull, mainly because of poor communication among the relevant authorities. Recently, it was recognized that there is an urgent need for better coordination among the different governmental organizations that are in charge of the management and conservation of water resources. It appears that the conservation issue has been neglected by water management organizations, whereas conservation agencies have been suppressed by the increasing need for water use. Water management policies carried out thus far in Turkey have resulted in the loss of many ecologically valuable water bodies because the interrelation between groundwater and surface waters has been underestimated (Bayarı et al. 2005). It now is recognized that overexploitation of one type of resource could have tremendous adverse effects on the other resource. More critical management policies that threaten the sustainable use of rivers include inter-basin water diversions to meet increasing irrigation demands in neighbouring

667

basins and the construction of numerous hydropower plants to meet increasing energy needs. All these activities create additional water management and conservation problems in downstream sections of the associated rivers. Establishment of water authotorities that undertake both management and conservation functions in each individual basin seems to be a plausible initial step for a better solution to the problem. For decades, water quality degradation has been an important issue in the Ergene basin. Proper agricultural practices are required for sustainable crop production as well as for maintaining the rich freshwater biota. The decrease in summer flow has further increased the pressure on the aquatic ecosystem. The Meri¸c River Delta in the Saros Bay of the Aegean Sea is one of the most important nature conservation areas in Turkey. However, increasing salinity in the Ergene forms an important threat to this ecosystem. The Aegean rivers are not fully regulated yet to meet increasing demands for irrigation, flood control and hydropower generation. However, numerous projects are planned and being implemented to meet these increasing needs. A local fishery is common in many reservoirs and pristine headwaters. The Gediz Delta, Marmara Lake (6800 ha), Smaller Meander Delta (2700 ha), Greater Meander Delta (9400 ha), Bafa Lake (12 280 ha) and I¸sıklı Lake (7300 ha) are among the most important nature conservation areas in the Aegean basins. The Sakarya River, near the city of Ankara, has experienced a long history of regulation beginning in the late 1930s. G€ok¸cekaya, Sarıyar, Porsuk, Cubuk-1 ¸ and -2, Kurtbogazı, Bayındır, Dodurga, Camlıdere ¸ and Asartepe are the major dams in the basin. Today, the Sakarya provides water for domestic and irrigation needs, generates hydropower and is regulated for flood control. The Sakarya is not navigable because of its large seasonal flow variation. Fishery still plays a local economic role. Sapanca Lake (area: 4700 ha), Mogan Lake (973 ha, protected area), Sarıyar reservoir (8400 ha, wildlife conservation area) and Sarıkum Lake (785 ha, nature conservation area) are among the major conservation areas in the basin. The Porsuk and Ankara Cayı ¸ tributaries are heavily polluted due to increasing industrial and agricultural activities in Ankara and Eski¸sehir. The Ye¸silırmak River has changed dramatically in recent years as a result of the construction of hydroelectric power plants. There are currently two major dams in operation, both commissioned in 1979. The lower dam (Suat Ugurlu dam) is 40 km from the sea. It is not equipped with a fish bypass, and therefore limits the upstream migration of sturgeons. Between this dam and the sea, the Ye¸silırmak has been less influenced from engineering and channelization than the Kızılırmak River. It is understood that flood prevention work will, in the future, be confined to deepening the natural riverbed. It is believed that this part of the river receives significant municipal and agricultural pollution. There are also plans to divert much of the water below the Suat U gurlu dam into canals for irrigation of farmlands, which will reduce the quantity of water in the main channel. Apart from dams constructed for local irrigation needs, seven major

668

dams have been built in the Ye¸silırmak basin since the late 1960s for hydropower and irrigation/domestic water use. Navigation is possible mostly at the delta, and local-scale fisheries are limited to reservoirs. The Ye¸silırmak Delta (3000 ha) and Yedikır reservoir (593 ha) are two protected wildlife conservation sites. The total water resource potential in the Kızılırmak basin has been mostly exploited by many dams built since the early 1960s. Navigation is limited and local-scale fishery occurs mainly in impounded sections. The Kızılırmak Delta is the most important wildlife conservation area in the basin. Other areas include T€ od€ urge Lake (750 ha), Palas Lake (2720 ha), Seyfe Lake (10 700 ha), Hirfanlı reservoir (26 300 ha) and Sultan Reedfield (17 200 ha). Kızılırmak Delta, Sultan Reedfield and Seyfe Lake are among the main Ramsar sites in Turkey. Several projects for hydropower generation along the G€ oksu River are either in the planning or financing stage. Steep river gradients and a highly variable annual flow does not allow navigational use. The G€ oksu and its tributaries provide opportunities for fishing and rafting. The G€oksu Delta, located to the west of the Cukurova ¸ plain, is one of the most important wetland sites for waterfowl and waders in Europe (Yılmaz 1998). A total of 327 bird species, including the largest number of Marmaronetta angustirostris known in Turkey, 215 insects and 302 plants have been identified. Although it is one of the special protected areas in Turkey, it has been put under increasing pressure from intensive agricultural and tourism-related activities. There is an urgent need to monitor surface and groundwater quality. The Seyhan River possesses considerable potential for generating hydropower and supplying irrigation water. These needs have been satisfied to a great extent in the coastal plain after the Seyhan (1956) and Catalan ¸ (1997) dams were built. Additional large dams and hydropower plants are planned or have been constructed in the mountainous parts of the basin. Like in most other mountainous river valleys in Turkey, water sport and a recreational fishery are becoming increasingly important. The Akyatan Lagoon (14 700 ha), at the mouth of the river, is an important wildlife conservation area (Ramsar site). This area will experience increasing chemical stress in the future by water that returns from the irrigated Cukurova ¸ plain. In the mountainous parts of the basin, several nature conservation areas exist. Although eight major dams have already been built along the Ceyhan River, many others are at planning/feasibility stages to fully exploit its hydropower and irrigation water potential. Fishing in reservoirs and rafting in pristine parts of the river are becoming emerging activities of economic importance. Two major sites of ecological conservation within the Ceyhan basin are A gyatan Lagoon (2200 ha) and Yumurtalık Lagoon (16 430 ha), a nature conservation area and a Ramsar Site, both along the Mediterranean coast. Implementation of the GAP project has already started to increase per capita revenue in the Euphrates basin. Once dry, arid agricultural lands are turned into fertile farms, agricultur-

PART | I Rivers of Europe

al settlements are then turned into industrially productive regions. Recently, total export from the GAP region has increased to 3 billion USD. Apart from region-wide socio-economic development, hydropower plants in the GAP region provides about half of Turkey’s hydro-electrical energy production. Hazar Lake (7000 ha) in the upper Euphrates, and Keban (12 500 ha) and Atat€urk reservoirs (81 700 ha) are among the major nature conservation sites in the basin. Construction of dams under the GAP project provided large freshwater areas, a particularly important need for migratory birds. Construction of new dams under the GAP project has resulted in socio-economic development in the Tigris basin. Substantial increases in irrigation water increased agricultural production, while industrial development increased around large cities like Diyarbakır. The Tigris basin does not have a legally protected nature conservation site, probably because there is restricted environmental pressure due to limited development in the region. About 27 dams and hydropower plants are planned for the Coruh ¸ River and its tributaries to meet increasing energy demands expecting to reach 10 500 billion kWh. Among these, Muratlı dam and hydropower plant was put into operation in 2005. The Coruh ¸ and its tributaries provide many opportunities for fishing and rafting, an activity that has became widespread in the last decade. Part of the Coruh ¸ basin is within the Caucasian terrestrial ecologic region, although the basin does not have a legally protected area. The Kar¸cal Mountains located to the east of Artvin comprises an ecologically important area in the basin. The Aras River and its tributaries are planned to be used for generating hydropower and provide irrigation water. Preliminary planning suggests hydropower production of 2 billion kWh/year and irrigation of lands covering over 400 000 ha. Cıldır ¸ Lake, in the northern basin, is a pristine ecosystem. The lake needs protection against domestic pollution from nearby settlements. Rivers in the enclosed basins with a semi-arid Anatolian climate are invaluable water sources that supply human needs and sustain local lakes and marshes of ecological importance. The surface water potential is insufficient and groundwater constitutes the main water resource, which has been dramatically depleted over the last few decades. Numerous groundwater dependent lakes and reedfields (440 591 ha) provide nesting sites for local and migrating birds. Overexploitation has caused a groundwater level decline rate of 1 m/year in the Konya closed basin where the main source of groundwater is from paleorecharge up to 40 000 years BP (Bayarı et al. 2004). Because of limited flows, many of the streams in the enclosed Van Lake basin have low economic importance. Regardless, water resource developments have been constructed or planned to regulate flow for irrigation and flood control. Pristine areas of streams, particularly in upper reaches, provide opportunities for fishing. Van (390 000 ha) and Er¸cek (9520 ha) Lakes host migratory birds and are ecologically important water bodies.

Chapter | 17 Rivers of Turkey

Acknowledgements _ We grateful to Prof. Ali Demirsoy, Prof. Ibrahim Atalay, Dr. Naime Arslan and Prof. F€ usun Erk’akan for their help to _ (General Directorate improve the text, and thanks to EIE of Electrical Power Resources Survey and Development Administration) and DSI_ (General Directorate of State Hydraulic Works) for providing various data.

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PART | I Rivers of Europe

Kadıoglu, M. 2000. Regional variability of seasonal precipitation over Turkey. International Journal of Climatology 20: 1743–1760. Kandemir, (Cevik), ¸ F., G€oksu, M.Z., Sarıhan, E. 1994. Seyhan Nehrinin (Adana Merkez il¸ce Sınırları I¸cinde Kalan B€olgesindeki) Planktonik Algleri ve Mevsimsel Degi¸simi, XII. Ulusal Biyoloji Kongresi, sf. 189–194 Edirne. Kara, C., and Alp, A. 2005. Feding habits and diet composition of Brown Trout (Salmo Trutta) in the upper streams of River Ceyhan and River Euphrates in Turkey. Turkish Journal of Veterinary and Animal Sciences 29: 417–428. Kavaz, E., Kırgız, T., and Camur-Elipek, ¸ B. 2003. Tunca Nehri Bentik Macroomurgasızlarının Nitel ve Nicel Dagılımları (€ozeti yayınlanmı¸s € unleri Sempozyumu,2–5 Eyl€ul, sempozyum bildiri). XII. Ulusal Su Ur€ Elazıg. Kaya, Z., and Raynal, D.J. 2001. Biodiversity and conservation of Turkish forests. Biological Conservation 97: 131–141. _c Kazancı, N. 2001. Ephemeroptera (Insecta) Fauna of Turkey. T€urkiye I¸ Suları Ara¸stırma Dizini VI. Imaj pres, Ankara 72 pp. _c Suları Kazancı N. 2008. Plecoptera (Insecta) Fauna of Turkey. T€urkiye I¸ Ara¸stırma Dizini IX, 49 pp. and figures. Kazancı, N., Girgin S.,D€ugel M., Oguzkurt D., Mutlu B., Dere S ¸ ., Barlas M., ¨ z¸celik M. 1999, T€urkiye I¸ _c Suları Ara¸stırmaları Dizisi IV (ed. N. and O Kazancı): K€oycegiz, Bey¸sehir, Egirdir, Ak¸sehir, Eber, Corak, ¸ Kovada, Yarı¸slı, Bafa, Salda, Karata¸s, Cavu¸ ¸ sc¸ u G€olleri, K€uc¸ €uk ve B€uy€uk Menderes Deltası, G€ull€uk Sazlıgı, Karamuk Bataklıgı'nın Limnolojisi, Cevre ¸ _ ¸ sitliligi. Imaj Yay. 372 s. Ankara. Kalitesi ve Biyolojik Ce¸ Kosswig, C. 1955. Zoogeography of the Near East. Systematic Zoology 4: 49–73. _ and G€uc¸ l€u Serkan, S. 2007. The fish fauna of K€uc¸ €uk, F., G€um€us¸, E., G€ulle, I., the G€oksu River (T€urkiye): Taxonomic and zoogeographic features. T€ urkish Journal of Fisheries and Aquatic Sciences 7: 53–63. Kuru, M. 1975. The Systematic and Ecological Study of Freshwater Fish living in Dicle-Fırat, Kura-Aras, Van Lake and Black Sea River Basin. Collegium thesis, Erzurum, 62 pp. Kuru, M. 2004. Recent systematic status of Inland water fishes of Turkey, € Gazi E G.U. gitim Fak€ ultesi Dergisi, cilt 24, sayı 3: 1–21. Mc Carthy, J., and Mc Carthy, C. 2003, Who Are The Turks? Educational Resource Guide, A Publication of American Forum for Global Education, ISBN 0944675-71-9, 120 Wall Street, Suite 2600, New York10005, 284 pp. Medail, F., and Quezel, P. 1999. Biodiversity hotspots in the Mediterranean basin: Setting global conservation priorities. Conservation Biology 13: 1510–1513. ¨ demi¸s, B., and Evrendilek, F. 2007. Monitoring water quality and quantity O of national watersheds in Turkey. Environmental Monitoring and Assessment 133: 215–229. ¨ demi¸s, B., Sangun, M.K., and B€uy€ukta¸s, D. 2007. Temporal variation in O water quantity and quality of Orontes River, Turkey. Asian Journal of Chemistry 19: 711–723. ¨ nt€urk, T., and Arslan, N. 2003. A preliminary study for the determination O on the Oligochaeta and Chironomidae fauna of G€um€us¸ Stream (Mar€ unleri Sempozyumu Bildirileri, Elazıg, din–Kızıltepe). XII. Ulusal Su Ur€ pp. 82–86. Onur, A.K., Ekemen, E., Soyupak, S., and Yurteri, C. 1999. Management strategies for the Lower Seyhan Catchment. Water Science & Technology 40: 177–184. ¨ terler, B., Kırgız, T., and Albay, M. 2003. Tunca Nehri Epipelik Algleri O € unleri Sempozyumu,2–5 Eyl€ul, Elazıg. (Poster). XII. Ulusal Su Ur€ ¨ Oterler, B., Kırgız, T., and Albay, M. 2004. Tunca Nehri Diyatomeleri ve Mevsimsel Degi¸simleri (Poster bildiri) I. Ulusal Limnoloji Calı¸ ¸ stayı, 17– 20 Mayıs, Sapanca/Adapazarı.

Chapter | 17 Rivers of Turkey

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ve T€ urkiye Zoocografyası “Hayvan Cografyası” Meteksan, Ankara 1007 pp. Yıldırım, A., and Aras Sıtkı, M. 2000. Some reproduction characteristic of Capoeta tinca (Heckel, 1843) living in the Oltu Stream of Coruh ¸ Basin. Turkish Journal of Zoology 24: 95–101. Yıldırım, A., Erdo gan, O., and T€urkmen, M. 2001. On the age, growth and reproduction of the barbel, Barbus plebejus escherichi (Steindachner, 1897) in the Oltu Stream of Coruh ¸ River (Artvin-Turkey). Turkish Journal Zoology 25: 163–168. Yıldırım, M.Z., Koca, S.B., and Kebap, I. 2006. Supplement to the Prosobranchia (Mollusca: Gastropoda) fauna of fresh and brackish waters of Turkey. Turkish Journal of Zoology 30: 197–204. Yıldız, K. 1987a. Diatoms of the Porsuk River, Turkey. Do ga Turkish Journal of Biology 11: 162–182. `Yıldız, K. 1987b. Porsuk Cayının ¸ Bacillariophyta Dı¸sındaki Algleri. Do ga Tu. Botanik D 11: 204–210. ¨ zkıran, U. € 1991. Kızılırmak Nehri Diyatomeleri. Do Yıldız, K., and O ga Turkish Journal of Botany 15: 166–188. ¨ zkıran, U. € 1994. Cubuk Yıldız, K., and O ¸ Cayı ¸ Diyatomeleri. Turkish Journal of Botany 18: 313–329.

PART | I Rivers of Europe

Yılmaz, K.T. 1998. Ecological diversity of the Eastern Mediterranean region of Turkey and its conservation. Biodiversity and Conservation 7: 87–96. Yılmaz, F., and Solak, K. 1999. Dicle Nehri’nde Ya¸sayan Capoeta trutta (Heckel.,1843)’nın Beslenme Organizmaları ve Bu Organizmaların Aylara ve Ya¸slara G€ore Degi¸simleri. Turkish Journal of Zoology 23: 973–978. Zreda, M., Ciner, ¸ A., Bayarı, S., Sarıkaya, A. 2005. Remarkably extensive early Holocene glaciation in Turkey. EGU 2005, 24–29 April 2005 Vienna, Geophysical Research Abstracts, v 7. (06068).

RELEVANT WEBSITES http://nkg.die.gov.tr. http://www.ipcc-data.org/obs/get_30yr_means.html. http://gis.ekoi.lt/gis/. http://edcsns17.cr.usgs.gov/glcc/tablambert_euras_eur.html. http://sea.unep-wcmc.org/wdbpa/. www.dsi.gov.tr

Chapter 18

Ural River Basin Margarita I. Yarushina

Tatjana V. Eremkina

Klement Tockner

Russian Academy of Science, Ural Division, Institute of Plant & Animal Ecology, Street of 8 March 202, 620144 Ekaterinburg, Russia

Ural Institute of Water Biological Facility, Yasnaja Street 1, 620086 Ekaterinburg, Russia

Institute of Freshwater Ecology and Inland Fisheries (IGB), M€ uggelseedamm 310, 12561 Berlin, Germany

18.1.

18.2.

18.3.

18.4. 18.5. 18.6. 18.7. 18.8.

Introduction 18.1.1. Historical Perspective and Cultural Aspects 18.1.2. Biogeographic Setting and Physiography 18.1.3. Palaeogeography Physiography, Climate, and Land Use 18.2.1. Physiography 18.2.2. Climate 18.2.3. Land Use Patterns Geomorphology, Hydrology, and Biogeochemistry 18.3.1. Geomorphology 18.3.2. Flow and Temperature Regimes 18.3.3. Sediments and Nutrients Biodiversity Management and Conservation Sakmara River Ilek River Conclusion References

18.1. INTRODUCTION The Ural, named Schajyq in Kazakhstan, is the 3rd longest (length: 2458 km) and 8th largest (catchment area: 253 000 km2) European river. It is a transcontinental river that forms the geographic boundary between Europe and Asia, and drains parts of Russia and Kazakhstan. Currently, the Ural is the only large free-flowing river feeding the Caspian Sea. Vast floodplains border the middle course of the river, and its delta is among the largest in Europe. Despite its size and potential ecological importance, the Ural is one of the least studied large European rivers. In this chapter, we provide an overview of catchment characteristics and Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

ecological conditions of the Ural, and we briefly discuss future management and conservation requirements.

18.1.1. Historical Perspective and Cultural Aspects Archaeological studies of ancient burial sites and settlements showed that the Ural paleolandscape was strongly affected by humans already during the late Bronze epoch (2000 years BC). The character of buried paleosols suggests the presence of forests during that period. Human activity as well as a progressively dryer climate after the last glaciation transformed the former forests into the present steppic landscape (Plekhanova & Demkin 2005). Today, the Eurasian steppe covers a vast belt of grasslands that start in Central Europe (Great Hungarian Plains) and spread across eastern Europe and central Asia (27 E to 127 E; 46 N to 55 N; Chibilev 1998). For thousands of years, the Eurasian steppe was an important migratory corridor and melting pot for people and cultures. The corridor of the Ural River served as the entrance gate for Asian people to Europe. Between the 6th and 4th century BC, the nomadic Sarmaty tribe lived in the lower Ural catchment, while the Ugorsky tribe inhabited the headwaters. The earliest known record of the Ural River is by the Greek historian and geographer Herodot. The river’s name changed during history from Likos, Daik, Daih, Dzhaih, Ruza, Yaik, Yagak, Yagat, Ulus, and finally to Ural. At the beginning of the 13th century the Mongols appeared on the banks of the Ural River. The Mongol Empire (1206–1405) was the largest contiguous empire in history, covering over 33 million km2. In 1236 the Ural catchment became part of the Golden Horde state that was established after the beginning of the break up of the Mongol Empire. In the mid-16th century, during the late period of the Nogai Horde, new nomadic tribes appeared along the banks of the Ural (at that time the Ural was called ‘Yaik’). The Kalmyks 673

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founded the first Cossack settlements. In 1552 and 1556, with the conquest of the khanats of Khazan and Astrachan (in the Volga delta) by Ivan IV (‘Ivan the Terrible’), the Russian Empire started to expand towards the Central Asian Steppe. The first Russian colonists on the Ural were the free Don and Volga Cossacks. The main Cossack fortification, the Yaitsky township, was founded in 1614 at the mouth of the river Chagan. The history of the Ural catchment is undeniably connected with the history of cultural disorder and human uprising. Stepan Razin and Emelyan Pugachev (national heroes in Russia) placed their troops on the banks of the Ural. There were two main uprisings in the 17th–18th centuries against the Tsarist Government when the troops of Razin and Pugachev crossed the river. In 1775, the Yaik was named Ural from the edict of Catherine II after the suppression of Pugachev’s uprising. Simultaneously, Yaitsky, the important township along the lower Ural, was renamed as Uralsk; and after the break-up of the Soviet Union as Oral because it is in the present Kazakhstan. The Ural area is characterized by a unique history of society-river interactions. The whole life style of the Ural Cossacks focused on the Ural River and the sustainable utilization of its sturgeons. There were fishery laws, fishery atamans (commanders), and the sturgeon was on the Cossacks coat of arms (Lagutov 2008). The natural wealth of the Ural has been studied by renowned scientists such as V.N. Tatischev, P.I. Rychkov, P.S. Pallas, I.I. Lepehin, E.A. Eversmann and N.A. Severtcov. The beauty and greatness of the Ural was described by famous poets and writers such as A.S. Pushkin, T. Shevchenko, V. I. Dal’, and A.K. Tolstoy.

18.1.2. Biogeographic Setting and Physiography The Ural rises in the Ural Mountains near Mount Kruglaya and flows south along their eastern flank. At Orsk it cuts westward across the southern end of the Ural Mountains, past Orenburg, and turns south again across a lowland semi-desert landscape before entering the Caspian Sea (Figure 18.1). The catchment includes 800 tributaries with lengths >10 km each, and 29 tributaries with lengths >100 km each. The largest tributaries are the Ilek and Sakmara Rivers. The headwater area lies in the blazed-pleated zone of the southern Ural Mountains, hilly South Zauralie, and low-mountain-hilly Mugodzhary (part of the Eastern plains). The Obshy Syrt Hills along the right bank separate the Ural from the Volga River basin. The Podural’skoe chalky plateau extends south of the central basin and is located mainly in the catchment of the Ilek. The plateau drops abruptly towards the Prikaspiyskaya lowlands. The Ural River, with its main tributaries Sakmara and Ilek, drains nine different ecoregions. The main ecoregions from north to south include the Ural mountain forests, the Eastern European steppe, the Kasakh steppe (including the

PART | I Rivers of Europe

Kazakh demi-desert and Kasakh forest steppe), the Pontic steppe, and the Caspian lowland desert. The Ural delta is entirely located within the Caspian lowland desert ecoregion. Soils change from chernzems and dark-chestnut soils in the northern mountain forests and forested steppe zones to brown desert soils and solonchaks (i.e. strongly saline soils) in the semi-desert and desert zones. The forest cover in the catchment is low (16% in the headwaters, 1–2% in the middle and lower parts (Leonov & Nazarov 2001) (Table 18.1). Before entering the Caspian Sea, the Ural forms a vast treelike delta, one of the largest in Europe (area = 8600 km2). Despite a low population density (24 people/km2), the upper section of the delta has been almost completely converted into irrigated cropland. The lower section still contains seminatural wetlands of international importance. The lower Ural catchment is a relict of the so-called Ponto-Caspian basin. During the Tertiary, the Ponto-Caspian basin included the modern Caspian and Black Seas and was connected to the Mediterranean Sea. Fluctuations of the proto-Caspian Sea in the Neocene determined the modern geomorphology of the region. In the middle Pliocene, the sea receded and only two smaller lakes remained as relicts of the ancient Pontic Sea. In the upper Pliocene, the so-called Akchagylian Sea expanded and covered Turkmenistan. Aridization and erosion continued in the Quaterny, combined with continuing sea level fluctuations and aeolic relief formations (Kosarev & Yablonskaya 1994). The sea level in the Caspian Sea fluctuates considerably, with amplitudes of 6 m during the past 2500 years. A rapid rise has occurred since 1978 (>2 m). Industries and townships have greatly expanded in recent decades and hence water level rises are causing great economic damage, pollution, and an upsurge of interest in the cause of these fluctuations (Dumont 1998; Glantz & Zonn 1997). The recent increase in water level has caused flooding of much of the coastal region, including the Ural delta, and is endangering coastal wetlands. The flooding has also impacted the oil exploitation infrastructure along the Caspian shore.

18.1.3. Palaeogeography The modern river valleys in the Ural catchment have relict characteristics. During glacial and interglacial periods their location, morphology, and flow regime frequently changed. With the melting of glaciers on the Russian plain, the discharge increased and previously temporary rivers became permanent. During this humid period, the Caspian Sea expanded northwards and inundated parts of the present Ural delta and the lower river course. The largest expansion occurred more than 20 000 years ago at the beginning of the late Pleistocene. The Caspian (or Hvalynsky) Sea flooded the entire Precaspian lowlands. On the Volga, the sea expanded upstream to the confluence with the Kama River. On the Ural, the sea expanded upstream to the confluences with the Utva, Irtek and Kindelya tributaries. During the Valday glaciation (18–22 000 years BP), the

Chapter | 18 Ural River Basin

FIGURE 18.1 Digital elevation model (upper panel) and drainage network (lower panel) of Ural River Basin.

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PART | I Rivers of Europe

TABLE 18.1 General characterization of the Ural River Basin

Mean catchment elevation (m) Catchment area (km2) Mean annual discharge (km3) Mean annual precipitation (cm) Mean air temperature ( C) Number of ecological regions Dominant (25%) ecological regions

Ural (with Sakmara and Ilek)

Sakmara

Ilek

Delta Ural

209 252 848 10.6 32 4.8 9 43; 55

327 29 489 4.4 39.6 3.4 4 28; 55

226 42 001 1.3 30.6 4.9 2 43

18 8586 n.d. 17.7 9.1 2 15

0.2 45.3 27.8 29.4 1.6 0.0 0.0 0.7

0.2 67.3 2.7 24.7 5.1 0.0 0.0 0.0

0.2 32.7 38.8 27.7 0.3 0.0 0.0 0.3

0.0 3.7 45.3 3.7 47.3 0.0 0.0 0.0

1.2

0.0

0.1

0.0

1.9 1.9 1 0 33 n.d. 1 17 2205

2.0 2.0 3 0 29 n.d 1 12 2205

2.1 2.3 n.d. 0 n.d. n.d. 1 24 n.d.

Land use (% of catchment) Urban Arable Pasture Forest Natural grassland Sparse vegetation Wetland Fresh water bodies Protected area (% of catchment) Water stress (1–3) 1995 2070 Fragmentation (1–3) Number of large dams (>15 m) Native fish species Nonnative fish species Large cities (>100 000) Human population density (people/km2) Annual gross domestic product ($ per person)

2.1 2.1 3 1 59 3 5 15 2205

For data sources and detailed explanation see Chapter 1. n.d.: No data

Hvalynsky Sea receded from North Precaspy. During the lowest water level of the Caspian Sea, the Ural and Emba Rivers formed a common delta. Today, many rivers between the Emba and Ural Rivers are sinking and becoming isolated. Only a few hundred years ago the Kaldygayty, Byldyrty, Olenti Rivers still were tributaries of the Ural. Nevertheless, the present river valleys of the Uralo-Embinsky interfluvials form peculiar oases within the (semi-) desert Pricaspy plain.

18.2. PHYSIOGRAPHY, CLIMATE, AND LAND USE 18.2.1. Physiography The Ural originates at 637 m asl in the foothills of the Nazhimtau and Uytash Mountains in Bashkiria, Russia. The river can be divided into an upper, middle and lower course, and the delta area. The upper catchment is orientated north–south and extends from the source downstream to Orsk. Five permanent springs feed a marshy headwater valley. After flowing through a narrow and deep mountain gorge, the river enters the Zauralisky Plain. Two major reservoirs are located along the upper Ural: the Verhneuralisky (area: 75.5 km2; storage volume:

601 106 m3) and Magnitogorsky (area: 33.4 km2; storage volume: 189 106 m3). In the middle section, the river flows for 850 km from East to West. At Uralsk (Oral), the river again turns south and forms the lower course. The Ural catchment has an asymmetric shape (Figure 18.1). The river network density is 35 and 25 m/km2 in the right bank and left bank catchments, respectively. The orographic rightside tributaries originate in the mountainous areas of Ural-tau, Krykty and Irandyk. The elevation of these mountain ridges ranges from 600 to 1000 m asl. The largest right tributaries of the Upper Ural are Mindyak (850 km2), Maly Kizil (1900 km2), Yangelka (730 km2), Bolshoy Kizil (1870 km2), Hudolaz (1170 km2), Urtazymka (1800 km2), Tanalyk (3980 km2), and Guberlya (2510 km2). Their headwaters are densely forested. The Iriklinsky reservoir, one of the largest in Russia (area: 260 km2; maximum volume: 3.25 km3), starts 70 km upstream of the city of Orsk. It was constructed between 1955 and 1959 as a multi-purpose reservoir to protect the city of Orsk against flooding, to support commercial fishery and for irrigation (Chibilev 2002) (Photos 18.1 and 18.2). The left-side tributaries of the upper Ural, except the River Or’, originate in the steppic hills of Urals–Tobolsky. From upstream they are Gumbeyka (area: 3700 km2),

Chapter | 18 Ural River Basin

677

PHOTO 18.1 Ural River headwater section (Photo: A.A. Chibilev).

Zingeyka (1410 km2), Bolshaya Karagayka (3250 km2), Suunduk (6210 km2), and Bolshoy Kumak (7170 km2). These tributaries exhibit a gentle slope, and most of them fall dry at the surface during low flow. The River Or’ (18 610 km2), one of the largest tributaries of the Ural, rises in the northern part of the Mugodzharsky Mountains (350– 400 m asl), flows first north before turning towards the main stem of the Ural. The middle and lower sections of the Or’

are fringed by vast floodplains containing countless temporary oxbow lakes. The Ilek River is the largest tributary of the Ural and drains the western part of the Mugodzharsky Mountains in Orenburg Oblast. Two main cities are located along the banks of the Ilek River: Alga and Aqt€obe. The Ilek has a highly variable flow regime with peak discharge during snowmelt (Figure 18.2). During low flow conditions the water of the Ilek becomes too PHOTO 18.2 Ural River at the Iriklinsky reservoir (Photo: A.A. Chibilev).

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PART | I Rivers of Europe

FIGURE 18.2 Seasonal discharge patterns of the Ural (upper panel) and the Ilek (lower panel) Rivers.

salty for drinking. The wide river valley is formed between two terraces. The lower terrace is covered by a complex network of temporary backwaters and oxbow lakes. The Utva River (catchment area: 4900 km2) enters the Ural 95 km downstream of the confluence with the Ilek. The last tributary before the delta is the Barbastau River (area: 1190 km2). The deltic area starts about 165 km from the mouth at the settlement of Kushumskoe where the Kushum channel diverts a high proportion of the spring floodwater towards the sea. In the upper delta area a vast irrigation system has been developed. In the lower section, additional Ural water is diverted into various delta channels. The Ural delta covers a total area of around 8600 km2. The delta width increases from 10 to 15 km at the upstream end to up to 60 km before entering the Caspian Sea. The lower delta starts at the town of Guriev. The main channel of the Ural is called the Golden Arm that forms a shipping canal before entering the Caspian Sea. It is artificially dredged to maintain a minimum water depth for commercial traffic. Due

to the decline in water flow during the past decades the mouth of the Ural River is becoming increasingly silted. The annual deposition of alluvial sediments is about 800 000 m3 (Government of Kazakhstan 2002).

18.2.2. Climate The Ural catchment has a continental climate with an average annual air temperature of 4.9 C (9.1 C in the delta). Air temperature exhibits large seasonal and diel amplitudes. For example, the annual amplitude (mean daily temperature) in the headwater area (at Iriklinsky reservoir) is up to 82 C (Solovych et al. 2003). Average annual precipitation is 320 mm and evaporation exceeds precipitation by at least a factor of two (Table 18.2). The upper Ural and upper Sakmara catchments are located in the Sibirian taiga zone. The number of frost-free days is 104 days in the upper catchment (at the town Verchneuralsk) and 184 days in the lower catch-

TABLE 18.2 Climatic characterization of the upper, middle and lower sections of the Ural catchment

Upper Ural Middle Ural Lower Ural

Temperature ( C)

Precipitation (mm)

January (minimum)

July (maximum)

April–October (IV–X)

November–March (XI–III)

Annual average

+38 to +40 +39 to +42 +42 to +43

202–241 176–247 102–130

95–101 106–157 61–120

303–339 282–404 164–250

37 to 34 to 27 to

46 37 34

Snow cover (cm)

Vegetation period (days)

27–35 30–35 0–25

104–136 138–145 153–184

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Chapter | 18 Ural River Basin

ment (at Guriev). In the upper and middle catchments, snow cover lasts on average 4–5 months. The lower catchment remains snow-free for most of the winter.

18.2.3. Land Use Patterns The Ural catchment is rich in natural resources. The Sarmat tribes were already associated with husbandry and cattle breeding and they developed copper mines and melted iron ore. For thousands of years, various caravans passed through the Ural area. In 1640, at the mouth of the Ural, the town Guriev was founded as a commercial fishery. During that period dense forests fringed the rivers. In 1734 the Verhneuralsky pier was constructed in the upper Ural, from which boats and timber were floated downstream to Orenburg. Clear cutting and timber floating changed the morphology of the river. Further development of the Ural catchment was linked to rapid human occupation. Forest clear-cutting, claiming of land, and irrigation have modified the hydrological regime of the river. As a consequence, the Ural River bed started to gradually aggrade. In the 20th century the construction of artificial water bodies and abstraction of water for industrial and public demands modified the seasonal flow regime. Today, seven reservoirs exist in the Ural catchment. Along the main Ural are the reservoirs Verhneuralskoe, Magnitogorskoe and Iriklinsky. The Aktyubinskoe reservoir is on the Ilek, the Verhne–Kumakskoe along the Bolshoy Kumak, the Kargalinskoye at Djaksy along the Kargala, and the Chernovskoye is on the Chernaya River. Water abstraction and surface retention lead to a 1.2–1.3 km3 reduction in the total annual flow. During dry years, annual flow reduction can be up to 2.2 km3 and, except during the spring flood, little water reaches the Caspian Sea during a dry year. The Ural increasingly suffers from heavy pollution (in particular the Ilek), from siltation in the delta, and from water abstraction for industry and agriculture. Important industries include blackening and colours metallurgy, mining (leading to high metal concentrations of Fe, Cu and Zn), natural gas exploitation, large-scale crop production, and livestockbreeding. Large collective farming operations have historically contributed substantial loads of fertilizers and pesticides to the Ural. However, the near-natural flow regime in the middle and lower river limits human exploitation of vast floodplains, thereby creating landscapes of high conservation value. The floodplains along the lower river in Kazakhstan, as well as the northern shore areas of the Caspian Sea, have already been declared as protected zones.

18.3. GEOMORPHOLOGY, HYDROLOGY, AND BIOGEOCHEMISTRY 18.3.1. Geomorphology The overall relief of the Ural is 670 m (source: 637 m asl, mouth: 26 m asl) and the average catchment elevation is 186 m asl. The average gradient of the main stem is

0.00045 m/m in the upper catchment (upstream of Orsk), 0.00018 m/m between Orsk and Uralsk (middle section), and 0.00003 m/m in the Caspian plain. The ancient valley of the Ural is filled with friable alluvial sediments that are tens of meters thick. Three distinct terraces were formed along the corridor. The upper terrace is mainly built of yellow-borax loam, the middle terrace contains numerous oxbow lakes and depressions, and the lower terrace is covered by shrubs and abundant large wood deposits. The upper corridor exhibits a sequence of narrow gorges and 1.5–3 km wide floodplains. Near the city Novotroitck, the river flows through the narrow Orsky gate gorge. In the middle section, the valley gradually widens. Upstream of the Ilek tributary, the river divides into two arms called ‘Razdory’. Downstream of the confluence with the Ilek, the river meanders through a 12–18 km wide floodplain and chalky mountains border the left bank. At the confluence with the Irtek, the Ural enters the territory of Kazakhstan. Downstream of Uralsk, the Ural enters the Caspian plain with a wide flat floodplain. At Guriev, the delta area, composed of multiple channels and natural and artificial levees, begins. The first delta channel ‘Peretaskin’ splits from the Ural 5.5 km downstream of Guriev. At 11 km downstream two major branches, Yaitcky and Golden canals, are formed (channel depth: 2–10 m). The Ural exhibits a meandering river style, with a sinuosity of 1.5–2.0 over most of its length. The riverbed is wide and shallow, with frequent shoals (water depth: 10–70 cm) and scour holes of up to 8–10 m deep. Banks are typically 2.5–5.0 m high. During low flows, the average width of the wetted channel is 60 m at Orsk, 80–100 m at Orenburg, and 160–200 m at Uralsk. The middle section of the Ural is bordered by a vast floodplain (total area: >5600 km2). The average width of the floodplain is 12–13 km, and is up to 20 km wide near the mouth of the Kindel’ River (Bespalov & Os’kina 2006). Forests, mainly black poplar (Populus nigra), cover about 25–30% of the total floodplain area. With an area of 830 km2, the black poplar forests along the Ural are among the largest in Europe. In addition, oak (Quercus robur), elm (Ulmus laevi), white poplar (P. alba), and white willow (Salix alba) are important floodplain trees. The floodplains along the Ural are ecologically unique systems. Since the Ural catchment was not glaciated, these floodplains served as important refuge areas for both warm- and cold-temperature adapted species.

18.3.2. Flow and Temperature Regimes In 1911/1912, the first water level recorders were installed along the Ural at Orenburg and Kushumsky, 60 km downstream of Uralsk. Since then, a total of 230 recorders have been installed in the entire catchment, but continuous data on water flow and water level are unfortunately missing. The Ural contributes about 5% to the total river input (300 km3/ year) to the Caspian Sea (Volga River: 80%; Terek, Sulak, Samur and Kara Rivers: 11%; Iranian tributaries: 4%). The

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Ural is a typical snow-fed river with a maximum flow in spring (80–90% of the annual flow) and low flow during the rest of the year (Drabkin 1971). Occasionally, small floods may occur in summer and autumn. Total average annual flow is 10.6 km3, although interannual variation is high. For example, the total annual flow was 24 km3 in 1957 but only 2.6 km3 in 1967. The total average annual discharge increases from 1.77 km3/year in the upper catchment (Iriklinsky reservoir) to 2.68 km3/year at Orsk, 7.73 km3/year after the confluence with the Sakmara, 9.24 km3/year after the junction with the Ilek, and finally to 10.6 km3/year at Uralsk. Downstream of Uralsk, the river loses 20% of its flow through evaporation while traversing the 800 km preCaspian (semi-)desert. About 72% of the annual runoff is produced in the Russian confederation although this part covers only 36% of the catchment area. The Ural exhibits the highest seasonal and annual flow fluctuations of all major European rivers (Figure 18.2). The ratio of the maximum to minimum flow (river regime coefficient) is around 1300; one to two orders higher than for most continental rivers. The maximum discharge ever recorded was 18,400 m3/s (spring 1942). During the spring flood, the river can laterally expand for 1–2 km in the headwaters, 18–20 km in the middle section, and up to 35 km in the lower section. Discharge decreases to <50 m3/s during the rest of the year. The average water velocity is 10 km/h during floods and 4–5 km/h during low flows. The alluvial character of the river valley (depth of the water-saturated layer: 8–20 m) facilitates large exchange between surface and subsurface flows. The right bank tributaries exhibit the smallest seasonal flow variation since they are primarily fed by groundwater. In contrast, left side tributaries exhibit a flashy flow regime, with peaks in spring and dry periods during the rest of the year (e.g. Ilek, Figure 18.2). The Ural freezes for 4.5–5 months. Ice break-up occurs within a few days in spring because air temperature rises rapidly. Ice jams are formed in outer meander bends but last only a few days because of the rapid rise in water during the spring flood. The maximum thickness of the ice cover is 1.5 m (average: 0.8–0.9 m). In the headwaters, the formation of extensive bottom ice can also lead to ice jams, creating major flow fluctuations even during the low flow winter period. In the downstream section, the 0.6–0.8 m ice cover lasts for up to 120 days and ice break-up is often caused by strong winds. Ice hummocks of 4 m and higher are formed along the seashore. During the spring flood, the water level increases to 3 m in the headwaters, 6 m at Orenburg, and 9–11 m at Uralsk. The average water level fluctuations in the lowland and delta regions are as low as 2.5 m. During the rising limb of the spring hydrograph, the water level increases 20–40 cm/day (maximum daily increase: 3 m). During the decreasing limb of the spring hydrograph, the water level decreases 5–10 cm/ day (maximum: 50 cm). The spring flood lasts between 15 and 25 days. The spring flood carries about 70% of the annual flow, compared to 12–20% in June and July, and

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about 8–18% during the rest of the year. The construction of the Iriklinsky reservoir has greatly altered the seasonal flow regime of the Ural downstream to Oldenburg. Seasonal water level fluctuations decreased from 5 to 8 m before construction to 0.5–1.5 m today. In addition, maximum seasonal flow now occurs between November and January compared to April–May before regulation. The thermal regime of the Ural differs from most European rivers. After ice break up, water warms rapidly and reaches 7–8 C by the end of April (upper and middle section), 14 C in May, and 22–25 C in summer (29 C at Guriev). Upstream of Orsk, the Iriklinsky reservoir leads to an average annual water temperature decrease of 1.0–1.5 C (Drabkin 1971).

18.3.3. Sediments and Nutrients The long-term average concentration of total suspended solids (TSS) is 310 g/m3. During the spring flood, the TSS increases to 2400 g/m3, but can be as low as 0.5 g/m3 in winter. Summer and autumn rains can cause brief increases in TSS. The high turbidity of the Ural is a consequence of easily erodable black soils as well as massive bank erosion during the spring flood. During the rising spring flood, large amounts of sediment (97% of total annual flux) are transported downstream, thereby reducing water transparency and primary production. The annual specific load (kg/ha/year) of Ptot, Ntot, DiSi, and DOC are 0.12, 1.63, 1.37 and 3.64, respectively (Leonov & Nazarov 2001). The average P-concentration is lower in the Ural than in other Russian rivers such as the Volga, Oka and Don. Maximum inorganic N concentration is 4 mgN/L. In addition, the Ural is relatively rich in organic components of N (DON) and P. The ratio between the annual inputs of dissolved organic forms (DOC, DON, DOP) is 523:85:1 for the Ural (Volga: 115:7:1). The ratio of the inorganic forms of Si, N, and P is 143:17:1 (Volga: 142:26:1). The largest amount of nutrients is delivered into the Caspian Sea during the spring flood, while during summer (June–August) 27– 37% of the annual input of P, 22–43% of N, 35% of DiSi, and 45% of DOC are discharged into the Caspian Sea. The Ural basin suffers from heavy pollution. In the Russian Federation, major pollution sources are the industrial complexes in Magnitogorsk and the Orenburg Oblasts. In Kazakhstan, the cities of Uralsk and Atyrau discharge municipal wastewater into the river. Data from 1990 to 1999 show that on the Russian–Kazakhstan border (village of Yanvartsevo), the concentrations of copper and phenol exceed the maximum concentration by a factor of 10–12, whereas the concentrations of hexachlorane and lindan were 1–18 times higher than the permissible levels (Government of Kazakhstan 2002). Other pollution sources include surface water runoff, particularly during floods, carrying away pollutants from sewage infiltration fields, as well as seepage from sewage ponds. Surface runoff from oil extraction sites on the Caspian coast carries oil products into the river.

Chapter | 18 Ural River Basin

18.4. BIODIVERSITY The vast riverine floodplains along the Ural provide habitats for endemic, relict, rare, and endangered plants and animals (e.g. the salmonid Stenodus leucichthys is endemic to the Caspian area). The white-tailed sea eagle (Haliaeetus leucogaster), the Russian desman (Desmana moschata), the European beaver (Castor fiber), wild boar (Sus scrofa), otter (Lutra lutra), saiga antilope (Saiga tartarica), among many others, still occur in viable populations along the corridor. The Ural River, including its delta, has a rich fish fauna with 59 native, three non-native, and one extinct species (Berg 1916; Shaposhnikova 1964; Kozmin & Matjuchin 1964; Reshetnikov 2003). The composition is similar to the fish fauna in the Volga River. Commercially important species in the upper and middle reaches include bream, pikeperch, roach and other whitefishes. In the lower section, anadromous species such as Caspian roach (Rutilus rutilus caspicus) are important. The most important fishes in the Ural are the sturgeons (Huso huso, Acipenser gueldenstaedtii, A. stellatus stellatus, A. nudiventris, A. ruthenus). Caspian sturgeons historically spawned in the Volga, Ural, Kura, Terek and Sulak Rivers, but dams have been constructed except along the lower and middle Ural and limit migration and dispersal. The Ural is now the only river where sturgeons still reproduce naturally in large numbers. Today, 1100 ha of spawning grounds remain in the Ural. Nonetheless, the annual yield in the Ural decreased from 15,000 tons at the beginning of the 19th century to 5000 tons in the 1930s, to 2000 tons in the 1960s, gradually increased again to 10’000 tons in the 1970s, and then collapsed with 280 tons in 2000 (Chibilev 1987; Lagutov 2008). The main reasons for the decline in catch are intensive sport fishing, poaching, pollution and flow alteration. For comparison, in the Volga River the potential spawning area declined by dam constructions (particularly by the Volgograd dam) by 90%, from 2290 ha before regulation to 372 ha at present (Caspian Environmental Programme 2002; Barannik et al. 2004). Further, 11 species of amphibians are reported from the upper Ural catchment (Vershinin 2007). Along the river, 650 phytoplankton species have been identified with diatoms (273 taxa) and green algae (208 taxa) being the most diverse groups. A total of 72, 133 and 75 zooplankton species have been recorded in the upper, middle and lower sections, respectively. The benthic community is rich, in particular in the middle meandering floodplain section. For example, the benthic fauna of the Ural includes 24 species from 7 families of Malacostraca, 13 species of Gammaridae and 5 species of Mysidae (Tarasov 1995). Species in the families Pseudocumidae and Janiridae inhabit only delta water bodies. The peculiar hydrodynamic character of the Ural (i.e. extreme seasonal fluctuations) has limited the upstream dispersal of Malacostraca.

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In recent times, however, an intense immigration of salt tolerant Caspian species into the middle and lower Ural has been observed. Recently, the immigration by Paramysis intermedia up to Orsk (Orenburg district), P. ulskyi up to Orenburg, and Niphargoides obesus up to Uralsk were caused by acclimatisation, navigation, and a reduction of water flow, and hence an increase in salinity. In general, the proportion of salt-tolerant benthic species is increasing at the mouth. Overall, the hydrobiology of the Ural and its tributaries has been given only little attention (e.g. Shell 1883; Bening 1938; Kiselev 1954; Drabkin 1971; Baturina 1983; Baturina & Poryadina 1984; Solovych et al. 2003).

18.5. MANAGEMENT AND CONSERVATION The Ural is a large international and transcontinental river. Its catchment encompasses one of the most important industrial–agrarian regions in Russia. The main industrial centers of Magnitogorsk, Orsk and Orenburg are located in the upper and middle sections. The Ural is navigable in the lower and middle sections. However, due to extended low-flow periods, barge traffic is not a profitable business. Further, the Ural corridor has a yet unexploited potential for recreation and environmental tourism. Since the 17th century, the Ural has played an important role for fishery in Russia. After heavy regulation of the Volga River, in particular by the construction of the Volgograd dam, the Ural provides the most important spawning ground for sturgeons. At the end of the 1970s, the Ural contributed 33% to the global sturgeon catch, and 40% to the production of black caviar worldwide. After the break-up of the Soviet Union in 1991, sea fishing (in the open Caspian Sea), illegal hunting, and trading led to a major decline in sturgeon populations. Today, sea fishing is again banned. More recently, sedimentation of the river mouth and pollution have caused a 50% reduction in spawning areas (Verina & Peseridi 1979; Secor et al. 2000). Today, about 2500 sturgeons migrate annually up the Ural for spawning (Pikitch et al. 2005). Almost the entire catchment of the Ural lies in the semiarid and arid climatic zone, and agriculture heavily depends on irrigation. It is the most important consumer of water and there is an urgent need to apply more advanced irrigation techniques to reduce water loss from disfunctioning systems. In the Ural catchment, a network of protected nature reserves, national parks, national monuments, and wildlife reserves have been created. However, protected areas, mainly in the category of national monuments, cover only 1% of the total area. Further, the shallow brakish coastal zones between the mouths of the Ural and Volga are extremely worthy for protection; their ecological state heavily depends on the water quality and quantity of these two major inflowing rivers. Overall, the conservation and sustainable management of the unique ecosystems along the Ural corridor

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and along the coastal shore areas are of regional and global importance.

18.6. SAKMARA RIVER The 750 km long Sakmara River, the largest right-bank tributary (catchment area: 29 500 km2), joins the Ural near the city of Orenborg (riverkm 1344). It originates at 600 m asl in the hills of Ural–Tau. The Sakmara catchment exhibits a complex geology with layers of gypsum and karstic relief, including many large karstic craters up to 5 m deep and 15–25 m wide. The catchment has a harsh climate with cold winters, heavy snow, and cool summers. The average temperature in January is 15 to 17 C and in July 17–20 C. Snow cover lasts for 170–190 days. Annual rainfall is between 400 and 700 mm. Average specific discharge is 8 L/s/km2. Tributaries of the Sakmara, except the Salmysh River, are steep mountainous rivers (Photo 18.3). The Sakmara has a highly asymetric catchment (left bank: 5010 km2; right bank: 24 490 km2). On the left bank, the only large tributary is the Kuragan (catchment: 800 km2), a steppic river that drains the Guberlinsky Mountains. The Sakmara is the largest free-flowing river remaining in the entire Ural basin. In general, the catchment is covered by dense forests (Table 18.1) dominated by birch, aspen-birch, and pine. The Obshy Syrt mountain range (400–600 m asl) separates the Sakmara from the Belaya catchment. This mountain range is covered by pine, oak, lime, elm and Norway maple (Acer platanoides). The western part of the catch-

PART | I Rivers of Europe

ment is covered by feathergrass steppe (200–300 m asl). The Bolshoy Ik River is the largest tributary of the Sakmara with an average annual discharge of 45 m3/s. The Bolshoy Ik flows through a karstic landscape with many caves and subsurface lakes. The headwater valley of the Sakmara is 2–5 km wide, followed by a narrow gorge through crystalline schist downstream of the Yuluk tributary. Downstream of the Urman– Zilair tributary, the river meanders through a 3 km wide valley forming large oxbow lakes and natural levees. The Sakmara disproportionately contributes to the total discharge of the Ural River. Although the Sakmara covers only 1/8 of the total Ural catchment, it contributes almost 40% (4.4 km3/year) to the total discharge. The Sakmara still has an unaltered flow regime and therefore may serve as a major reference system for Steppic Rivers. The Sakmara is partly fed by groundwater reducing the seasonal and interannual flow variation. It is a snow-fed river with maximum discharge in spring (70% of total annual discharge). During spring floods, discharge can exceed 5300 m3/s. In the lower section, seasonal water level fluctuations are up to 6 m (upper section: 3–4 m). The water is enriched in hydrocarbonates and calcium. The concentration of TSS reaches 2260 g/m3 during spring floods. Concentrations of nitrate (up to 4.0 mg N/L) and phosphorous (0.003–0.17 mg P/L) are similar to concentrations found in the Ural River. Thirty-three fish species have been recorded from the Sakmara. Further, 120 phytoplankton taxa including 81 diatoms, and 71 zooplankton taxa have been identified. The benthic community is dominated by chironomids (53 species identified thus far).

PHOTO 18.3 Sakmara River (Photo: V. Vershinin).

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Chapter | 18 Ural River Basin

18.7. ILEK RIVER The 600 km long Ilek River is the largest tributary of the Ural and drains an area of 42 000 km2. It originates at 350 m asl on the western slopes of the Mugodzhary mountains and enters the main stem downstream of Orenburg (riverkm: 1125). Bed sediments change from pebble–sand in the upper section to sand–clay in the middle and the lower sections, forming extensive shoals and highly erodable banks. The channel width is 10–15 m in the upper, 20–30 m in the middle, 30–60 m in lower section. The river valley is 2–4 km wide in the upper and 5–7 km in the lower section. Riverbanks are 3–5 m high and the floodplain contains numerous oxbow lakes. The Ileksky oxbow lakes are the largest and deepest in the Ural catchment. The floodplain is mostly occupied by aspic meadows and shrubs. Trees had been cut by nomadic tribes. Hydrological observations on the Ilek River began in 1932 but continuous data records are absent (Figure 18.2). Similar to the Sakmara River, the Ilek has a characteristic snowmelt flow regime, although total discharge is 3.4 times less than the Sakmara. From mid-November until mid-April, the Ilek is covered by ice (maximum thickness: 0.5–0.8 m). The Ilek River remains the most polluted river in the Ural–Caspian basin. High concentrations of boron and chromium from former tailing ponds of chemical plants enter the river via ground water (Water Resources Committee of RK 2002). The main source of boron pollution along the Ilek is the former Aktubinsk Kirov chemical plant that released untreated wastewater into the river. The second major pollution source is the Alginsk chemical industrial complex that pollutes the river with hexavalent chromium (Chromium(VI)). Twenty-nine fish species are reported from the Ilek River. However, almost nothing is known about the hydrobiology of the river, with only 5 phytoplankton, 16 zooplankton, and 7 benthic species having been recorded (Drabkin 1971).

18.8. CONCLUSION The management issues of prime importance in the Ural catchment include (i) the restoration of the contaminated Ilek River and its adjacent riparian zone, (ii) the dredging of the Ural River mouth to remove deposited sediments, (iii) the improvement of a monitoring network (hydrological and ecological network), (iv) defining and maintaining environmental flow conditions in the main stem and in the tributaries (at present 23% of the total annual flow is abstracted for irrigation), (v) the upgrading of water intakes for the fishery industry, and (vi) the protection of the sturgeon populations and their natural reproduction sites. For the successful development of management strategies we need a sound scientific basis. Major efforts are required to improve our knowledge about the present and future pressures on the entire basin because the Ural River – and in particular the

Sakmara tributary – can serve as a reference river for the steppic zones of Eastern Europe and Central Asia.

REFERENCES Barannik, V., Borysova, O., and Stolberg, F. 2004. The Caspian Sea region: environmental change. Ambio 33: 45–51. Baturina, V.N. 1983. Composition of the phytoplankton of Iriklinsky reservoir. Orenburg. VINITI (In Russian). Baturina, V.N., and Poryadina, S.N. 1984. Flora of Algae of the Ural River and Oxbow Lakes in Borders of Orenburg Region. VINITI, Orenburg (In Russian). Bening, A.L. 1938. Materials of Hydrobiology of the Ural River. Unpublished report by the Kazakhstan’s branch of AS USSR 11: 153–257 (In Russian). Berg, L.C. 1916. Freshwater Fishes of Russia. Moscow. AN. (In Russian). Bespalov, V.P., and Os’kina, N.V. 2006. The effect of soil hydrological conditions on the growth of natural and artificially planted oak (Quercus robur L.) stands on the floodplain of the Ural River in its middle reaches. Eurasian Soil Science 39: 410–422. Caspian Environmental Programme. (2002). Transboundary Diagnostic Analysis for the Caspian Sea. Vol II, CEP, Baku. Chibilev, A.A. 1987. The River Ural. Hydrometeoizdat, Leningrad (In Russian). Chibilev, A.A. 1998. Steppes of Northern Eurasia. IS UrO RAN, Ekaterinburg (In Russian). Chibilev, A.A. 2002. Iriklinsky Reservoir. Gazprompechat, Orenburg (In Russian). Drabkin, B.S. (ed). 1971. Hydrobiology of the Ural River. Yuzhno-Uralsky Book Publishing House, Chelyabinsk (In Russian). Dumont, H.J. 1998. The Caspian Lake: History, biota, structure and function. Limnology & Oceanography 43: 44–52. Glantz, M.H., and Zonn, I.S. (Eds.) 1997. Scientific, environmental, and political issues in the Circum-Caspian region. NATO ASI Series. Kluwer Academic Publisher. Dordrecht, The Netherlands. Government of Kazakhstan. 2002. Identification of priority issues in seven major river basins in Kazakhstan. Committee for Water Resources of the Ministry of Natural Resources and Environmental Protection. Atyrau, 9 August 2002. Kiselev, I.A. 1954. Algae of water bodies in the middle and lower catchment of river Ural at the borders of Chkalovsky’s and West-Kazakhstans regions. Report by the Zoological Institute of AS USSR XVI: 532–575 (In Russian). Kosarev, A.N., and Yablonskaya, E.A. 1994. The Caspian Sea. SPB Academic Publishing, The Hague (NL). Kozmin U.A., and Matjuchin V.P. 1964. About the Fish Fauna of the Iricla Reservoir. Works of the Ural GOSNIORCH. Vol. 6 (In Russian). Lagutov, V. (ed). 2008. The rescue of sturgeon species in the Ural River Basin. Springer, The Netherlands. Leonov, A.V., and Nazarov, N.A. 2001. Nutrient input into the Caspian Sea with river runoff. Water Resources 28: 656–665. Pikitch, E.K., Doukakis, P., and Lauck, L. 2005. Status, trends and management of sturgeon and paddlefish. Fish and Fisheries 6: 233–265. Plekhanova, L.N., and Demkin, V.A. 2005. Ancient soil disturbance in river valley within the steppe zone of the southeastern Urals. Eurasian Soil Science 38: 973–982. Reshetnikov, Y.S. (ed). 2003. Atlas of Russian Freshwater Fishes. 2nd edition, Reshetnikov, Y.S. (ed). Nauka, Moscow Two Volumes (In Russian).

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Secor, D.H., Arfjev, V., Nikolaev, A., and Sharov, A. 2000. Restoration of sturgeons: lessons from the Caspian Sea Sturgeon Ranching Programme. Fish and Fisheries 1: 215–230. Shaposhnikova, G.H. 1964. Biology and Distribution of Fish in Rivers of Ural’s Type. Nauka, Moscow (In Russian). Shell, Y.K. 1883. Materials for Botanical Geography of Uphimsky’s and Orenburg’s Huberns. Printing-house of Emperor’s University, Kazan’. Solovych, G.N., Raimova, E.K., and Osadchaya, N.D. 2003. Hydrobiological Characteristics of the Iriklinsky Reservoir. UrO RAN, Ekaterinburg (In Russian). Tarasov, A.G. 1995. Crustaeofauna (Malacostraca) of the Ural River. Zoologichesky Zhurnal 74: 24–34. Verina, I.P., and Peseridi, N.E. 1979. On the sturgeon spawning ground conditions in the Ural River. Sturgeon Culture of Inland Waters. Caspian Fisheries Institute, Astrakhan, pp. 33–34 (In Russian). Vershinin, V.L. 2007. Amphibians and Reptiles of the Ural River. UrO RAN, Ekaterinburg (In Russian).

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Water Resources Committee of RK. 2002. Water resources of Kazakhstan in the new Millennium. http://www.undp.kz/library_of_publications/files/ 2496-19223.pdf.

RELEVANT WEBSITES United Nations Development Program in Kazakhstan: http://www.undp.kz Environment and Sustainable Development in Central Asia and Russia: http://www.caresd.net Specially Protected Areas: http://oopt.kz Regional Environmental Center for Central Asia: http://www.carec.kz/ GEF Small Grants Program in Kazakhstan: http://gefsgp.un.kz Program Wetlands International in Russia: http://wetlands.ru/ Central Asian Mountain Program (CAMP): http://www.camp.elcat.kg Center for Wild Nature Protection: http://www.biodiversity.ru Caspian Environmental Program: http://www.caspianenvironment.org

Chapter 19

European Rivers: A Personal Perspective Alan G. Hildrew

Bernhard Statzner

School of Biological & Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK

CNRS, Biodiversit e des Ecosyst emes Lotiques, 304 Chemin Creuse Roussillon, F-01600 Parcieux, France

19.1. 19.2.

19.3.

19.4.

19.5.

First Impressions A Closer Look: Quantitative Patterns Among River Basins 19.2.1. Socioeconomics 19.2.2. Runoff Ratio 19.2.3. Fish Diversity The State of the Continent 19.3.1. Bad and Good News 19.3.2. Flow Regulation, Impoundments, Abstraction and Connections 19.3.3. The Future Policy – What we Should do 19.4.1. Are Rivers Particularly Problematic? 19.4.2. Conserve or Restore? 19.4.3. ‘Technical Fixes’ Science – What we Need to Know Acknowledgements References

19.1. FIRST IMPRESSIONS In our finale chapter to this book about European Rivers, we chose simply to give our personal reactions on reading drafts of all the other Chapters in sequence – something perhaps few other people will do with what is essentially an impressive work of reference. A more ambitious and extensive synthesis of the information available remains a much larger job for the future, once all the data have been reconciled. We start with these ‘first impressions’ of what this book does and does not do, and then take a ‘closer look’ at some preliminary patterns in those data that were consistently available to us (beyond analyses already presented by the editors in their ‘Introduction’). We then give a personal take on the ‘state of the continent’ from a river ecologist’s point of view, indicate what might be some policy lessons at this continental scale and, finally, point out some scientific loopholes and future research possibilities. Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.

Most people with an interest in rivers will share a love of wild places and creatures and a respect for the power and grace of water in the landscape. We have to admit to a distinct, albeit unscientific, feeling of sadness at all that has been lost from Europe’s river systems. The statistics are mind blowing – 95% of riverine floodplains and 88% of alluvial forests gone, >6000 large dams in Europe, only one out of the 20 largest rivers remains free-flowing, 95% of the biomass of benthic animals in the Rhine made up of nonnative species, the near extinction of the beluga sturgeon – the gloomy list goes on and on. We should not have been surprised, these stories are well known and repeated everywhere, but the accumulated information in this book is undeniably powerful. Yet much of beauty and interest remains, and rivers are incredibly resilient. We may not be able, nor even want, to restore everything to a more pristine state, yet river systems still provide us with much that is both vital and fascinating. We need to treat them with respect and intelligence if this is to continue, and to do that we still require an increased understanding of how river ecosystems work in a crowded and changing world. So there is a great scientific, managerial, political and cultural challenge in dealing with rivers – and this book begins to bring together much of the background information necessary for doing so in Europe. The reader certainly finds lots of detail on the climate, geology, hydrology, geography and biology of Europe’s greatest – and many of its smaller – rivers. What are particularly useful are references to the non-English language and ‘grey’ literature. There is an enormous amount of information in these sources, which are poorly known internationally, and summaries such as this, plus an indication of where to find more detail, are valuable. Some of the most fascinating insights are the inclusion in each chapter of details of the human history associated with rivers. Rivers have been the corridors of exploration and migration, the boundaries and icons of great empires and cultures, and the sources of wealth of European peoples for thousands of years. Of course we knew this, but this book really brings it home. Books collecting together information about particular sets of rivers are 685

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not new. For instance, this one follows on from a sister work about the Rivers of North America (Benke & Cushing 2005), while Whitton (1984) produced a much earlier compendium on the ecology of European rivers and Cushing et al. (2006) attempted a global synthesis in the context of the river continuum concept. However, ‘The Rivers of Europe’ is the most comprehensive, cross-disciplinary and contemporary source of information about the river systems of our continent. This book has been an enormous undertaking, but even it cannot do everything and what the reader does not find here is also revealing. For instance, it tells us about the disparate value put on researching and monitoring river systems throughout Europe. This is evident from the data about the hydrology and the physicochemical environment of even the greatest European rivers (rich, detailed and long term in some cases, sketchy in others) but particularly about biology, where emphasis was put on water column organisms and processes in some, and on benthic systems in others. This only partly reflects the size of the river concerned – we naturally expected a greater focus on the benthos of small rivers and the plankton of large ones – but also the scientific heritage in different parts of the continent. The rivers of the former Soviet Union were apparently subjected to a great deal of research effort on the plankton and productivity of the water column of the many reservoirs, but rather less on the overall ecology of the rivers themselves. There is also a striking lack of information on ecosystem processes – that are such a focus of modern basic research elsewhere. At the continental margins and on islands (e.g. Britain and Ireland, Fennoscandinavia, Spain and Portugal, Italy and Greece), there are of course many smaller river systems with independent outflows to the sea and small drainage basins (in contrast to the enormous catchments of the large continental rivers). This has presented a problem of choice to the authors and editors. Those rivers that were picked out for mention drain only a fraction of the total land surface and others had to be excluded. In some cases much is known of the many rivers that are NOT included, but this information is of course not given here. Nevertheless, all the great rivers of Europe are dealt with – some so great that they had to be ‘broken up’ and treated as separate sub-systems – making for an extremely impressive collation. Finally, this is evidently a book about rivers and not their headwater streams. It concentrates on the mainstream of rivers and their major tributaries. Even where there is a great deal of ecological information about particularly well-studied streams that lie within the catchments dealt with – this has not been presented. Two obvious examples are the German Breitenbach, a tributary ultimately of the Weser and formerly the subject of long-term research by the Max Planck Institute for Limnology, and the Oberer Seebach in Austria (within the Danube basin), previously the subject of long-term research by the Austrian Academy of Sciences. So this book does not tell us everything, but it does tell us a great deal.

PART | I Rivers of Europe

19.2. A CLOSER LOOK: QUANTITATIVE PATTERNS AMONG RIVER BASINS Each chapter of this book presents a broadly consistent set of information in the first table. These tables characterize whole catchments (or sub-catchments of the larger basins) via data on physics, land-use (including protected areas), other human impacts, the number of ecoregions, biological (fish species richness) diversity and socioeconomics (for the largest rivers, some of these data are summarized in Table 1.1 of Chapter 1). We have taken these data at their face value although, not surprisingly, there are some gaps and inconsistencies. However, we were able to ask some ostensibly simple questions, to which our preliminary analysis can provide answers using varying subsets of the 164 catchments/subcatchments included in the book. These cover some of the socioeconomic drivers at work in river catchments, and factors affecting water balance and fish diversity.

19.2.1. Socioeconomics Managing European river catchments to meet the requirements of the EU’s Water Framework Directive (WFD) will be so costly (Anon. 1998; Kaika & Page 2003; Page & Kaika 2003) that its successful implementation might well depend partly on the economic wealth generated within catchments or sub-catchments. To assess this ‘catchment wealth’, we calculated a catchment-specific gross domestic product [CAS-GDP ($/km2/year)], doing so when possible for the smallest available sub-catchments of larger river basins. Across the 151 catchment units where data are available, this indicator ranges from zero (an arctic island with neither human inhabitants nor an economy – ignored in further analyses) to 31.8 million US $, with 50% of the catchments generating <0.3 million $/km2/year. The poorest remaining catchment is that of the Komagelva, followed by the Geithellnaa, Varzuga, Mezen, Vestari-J€okulsa, Pechora and Onega; apparently the wealthiest (perhaps surprisingly) is that of the Mersey, followed by the Thames, Lower Rhine, Trent, Aare, Rhine Delta and Neckar (see Figure 1.2 of Chapter 1 for the location of these catchments). The frequency distribution of catchment wealth is skewed heavily toward the lower end and approximates a normal distribution when log-transformed (Figure 19.1a). This frequency distribution suggests that the level of human wealth in many European river basins is so low that one might expect financial constraints (at least unless there are subsidies) on the implementation of the WFD, and that emphasis would be placed on economic growth rather than the ecological status of rivers. Catchment-specific gross domestic product is a composite indicator of catchment wealth that combines both human population density and per capita (‘person-specific’) gross domestic product. A plot of these two variables (Figure 19.1b) indicates that catchments with a very low human population density (and therefore a potentially low anthropogenic impact on rivers) can have a relatively rich

Chapter | 19 European Rivers: A Personal Perspective

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FIGURE 19.1 Socioeconomic patterns across 146–150 (note that the varying N here and elsewhere relates to data availability) catchment units [entire catchments (from headwaters to river mouth) or smaller subcatchments of larger whole basins]. (a) Frequency distribution of the catchment-specific gross domestic product (CAS-GDP). (b) Plot of human population density (HU-DENS) versus ‘person-specific’ (i.e. per capita) gross domestic product (PES-GDP). (c–f) Plots of CAS-GDP (N = 146) versus (c) mean annual air temperature (MA-TEMP) (R2 = 0.291, P < 10 11), (d) mean annual precipitation (MA-PREC) (R2 = 0.173, P < 10 6), (e) density of large (>100 000 inhabitants) cities (CI-DENS) (R2 = 0.297, P < 10 11) and (f) person specific discharge (PES-DIS) (R2 = 0.393, P < 10 15).

(per capita) population (e.g. Suldalslagen, Jostedøla, Stry neelva, Lærdalselva, Orkla, Mandalselva, Numedalslagen). Other catchments have a moderately high human population density (and thus potentially perturbed rivers) and either wealthy (e.g. Aare, Alpine Rhine) or poor (e.g. Smaller Meander, Asi, Iskar, Vah, Vistula, Velika Morava, Prut) human

populations. Finally, catchments with the highest human population density (and potentially the highest human impact on rivers) have populations of overall intermediate wealth (e.g. Mersey, Thames, Lower Rhine, Trent, Rhine Delta, Neckar, Ouse). Obviously, the economics of implementing the WFD must vary among these basins.

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Beyond the historical and sociopolitical reasons that affect current economic patterns across Europe (outside the scope of this preliminary analysis), climatic gradients might explain some of the variation in catchment wealth. For instance, we anticipated that catchment units with extreme temperature and/or precipitation would be relatively poor, because such extremes might limit human density and/or per capita wealth (at least historically). Indeed, the wealthiest catchment units apparently do have an intermediate mean annual air temperature (Figure 19.1c) and mean annual precipitation (Figure 19.1d) (note that both variables are logtransformed in Figure 19.1). However, the gradient of these two climatic variables toward the upper end is too short for us to observe a clear decrease in CAS-GDP along temperature or precipitation extremes. Land-use descriptions for the catchment units facilitate an assessment of what type of human activities (urban versus agriculture) might account for catchment-specific wealth. We find that urban development, as described by the density of large (>100 000 inhabitants) cities in river basins (Figure 19.1e) rather than by the simple percentage of urban land, explains most of the variation in wealth. This suggests that, for a similar percentage of urban areas in a catchment, fewer, larger cities contribute more strongly to catchment wealth than more numerous but smaller towns and cities. If true, this could have consequences for strategic catchment management. Furthermore, log-transformation of both variables in Figure 19.1e is not sufficient to linearize their relationship. Thus, above a certain threshold, economic wealth in a catchment does not increase with the density of cities, presumably because a high density of large cities incurs costs at an accelerating rate, detracting from catchment wealth. Finally, we might expect that the economic wealth of catchment units should increase with the availability of water provided by river discharge, given that policy in many parts of Europe aims to increase water supply for human uses (see above). To assess this point, we calculated a per capita discharge for our catchment units, to capture a maximum potential water use from the main river per person per day. Somewhat to our surprise, catchment wealth actually declines with increasing per capita discharge (Figure

19.1f), suggesting that high economic wealth is the cause of reduced water availability, and that the pre-emption of river discharge by humans in modern Europe (perhaps nearing its completion at the catchment scale) is a surrogate for general economic development. In this context, the Meuse, Loire, Adour, Trent, Garonne and Thames now provide so little discharge per person and day (0.1–0.5 m3) that water withdrawals for domestic, industrial and other uses (in urban areas around 0.3–0.6 m3/person/day; Simonovic 2002) can barely be met and that local water resources are fully exploited. A regression model including mean annual air temperature and precipitation, the density of large cities and per capita discharge as independent variables explains 71.3% of the variability in catchment-specific GDP (Table 19.1). In this model, the partial P-value of the air temperature is much higher (i.e. indicating lower significance) than the partial P-values of the other three variables. Repeating this exercise with ‘person-specific’ (i.e. per capita) wealth, the same four independent variables explain only 35.3% of the variation (Table 19.1); air temperature contributes insignificantly to this model. Finally, the four independent variables explain 88.3% of the variation in human density in the catchment units; all four variables are highly significant (P < 10 6 to P < 10 15). Thus, the historical relationship between wealth in catchment units and temperature, precipitation, the density of large cities and per capita discharge may have been shaped primarily through the potential dependence of human population density on the natural environmental variables. This further suggests that, through their potential effects on human density, such factors simultaneously affect human stress on rivers and catchment wealth, which should have also implications for the implementation of the WFD. The data provide the opportunity to address two other socioeconomic questions. First, is the percentage of the catchment area that is protected related to catchment wealth? While the relationship is not quite significant, the fraction of protected areas does tend to decrease with catchment wealth (P = 0.068). Second, is the percentage of arable (i.e. devoted to crops) land in catchment units (CROP-AREA) related to

TABLE 19.1 Regression models describing socioeconomic patterns across 146 catchment units illustrated in Figure 19.1 Model items

Dependent variable log CAS-GDP

Intercept log (MA-TEMP + 10) log MA-PREC log (CI-DENS + 1) log PES-DIS R2 P-value

0.084 0.687 (0.903) 1.13 0.42 (0.007) 2.36 0.26 (<10 15) 5124 854 (<10 7) 0.381 0.055 (<10 9) 0.713 <10 15 a

a Here and elsewhere in equations: parameter estimate standard error (partial P). See Figure 19.1 legend for acronyms

log PES-GDP

log HU-DENS

1.24 0.60 (0.041) 0.298 0.365 (0.415) 1.54 0.23 (<10 9) 1782 750 (0.019) 0.118 0.048 (0.016) 0.353 < 10 11

1.16 0.40 (0.004) 1.43 0.24 (<10 7) 0.819 0.150 (<10 6) 3341 492 (<10 9) 0.499 0.032 (<10 15) 0.883 <10 15

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TABLE 19.2 Regression models describing various patterns in socioeconomics, runoff and fish diversity Socioeconomics CROP-AREA = 29.7 24.9 (0.236) + 59.8 17.0 (<10 3) log (MA-TEMP + 10) R2 = 0.538, P < 10 15)

14.5 1.8 (<10

12

) log CROS-DIS (N = 142,

Runoff RUN-RAT = 0.759 0.367 (0.041) 0.435 0.185 (0.020) log (MA-TEMP + 10) + 0.466 0.112 (<10 4) log MAPREC 0.108 0.028 (<10 3) log CAT-AREA 0.107 0.043 (0.015) log (CROP-AREA + 1) 0.243 0.062 (<10 3) log (URB-AREA + 1) (N = 128, R2 = 0.530, P < 10 15) Fish diversity log TOT-FISH = 0.668 0.154 (<10 4) + 0.236 0.031 (<10 10) log CAT-AREA 0.411 0.059 (<10 9) RUN-RAT (N = 109, R2 = 0.707, P < 10 15) log (NONNAT-RAT + 1) = 0.0952 0.0338 (0.006) + 0.00541 0.00077 (<10 9) MA-TEMP + 0.0318 0.0079 (<10 3) log PES-GDP (N = 109, R2 = 0.345, P < 10 9) Notations: CAT-AREA: catchment area (km2); CROP-AREA: cropland area in catchment unit (%); CROS-DIS: cropland specific river discharge (m3/km2/day); MAPREC: mean annual precipitation (cm); MA-Temp: mean annual air temperature ( C); NONNAT-RAT: non-native fish species ratio (proportion); PES-GDP: person-specific gross domestic product ($/person/year); RUN-RAT: runoff ratio (proportion); TOT-FISH: total fish species richness (Species No.); URB-AREA: urban area in catchment unit (%).

climate and/or the potential supply of water from rivers for irrigation? As in the case of catchment wealth, we might expect less arable land at the extremes of temperature and precipitation (MA-TEMP/MA-PREC). In addition, we anticipated less arable land where water supply from rivers for irrigation is limited [as for people, described via a ‘croplandspecific river discharge’, CROS-DIS (m3/km2/d)]. These expectations were not supported by the data (see model in Table 19.2). Rather, in this model, the percentage of arable land increases monotonously with increasing mean annual air temperature and decreasing potential riverine water supply (for irrigation), whereas mean annual precipitation does not contribute significantly (P = 0.707). Thus, as in the relationship between economic wealth and per capita river discharge, the greater percentage of arable land in catchment units seemingly is the cause of reduced water availability. That is, the development of irrigation agriculture is apparently more or less up to the limits of water supply within the catchments concerned. This now leads us to consider water budgets within these catchments.

19.2.2. Runoff ratio The runoff ratio (defined as mean annual runoff as a proportion of mean annual precipitation) is one indicator of the water balance in a catchment. For its analysis, we focus on entire river basins or, if possible, on smaller functional hydrological units in the upstream parts of larger catchments (ignoring downstream sub-catchments of larger rivers). In the 142 catchments having the necessary data, the runoff ratio ranges from 0.009 to 2.37, and 50% of catchments have a runoff ratio <0.44. Again, the frequency distribution of this variable is skewed toward the low end, while a few catchments actually have a runoff ratio >1 (Figure 19.2a); that is apparently they have more runoff than precipitation. Almost all the catchments with a runoff ratio >1 are

from the Arctic or other cold northern regions, perhaps indicating that climate change has already disturbed the water budget, the amount of meltwater from glaciers not being compensated for by contemporary precipitation. The hydrology of these northern rivers is so different from that of the rest of Europe that we ignore all catchments with a runoff ratio >1 in the analysis here. Among the variables characterising the catchments, there are several that are known to affect the runoff ratio because they indicate mechanisms such as evapotranspiration, soil infiltration and groundwater abstraction (Burt 1992; Gustard 1992). Most obviously, the runoff ratio should decline with air temperature, a relationship that is supported by the data in this book (Figure 19.2b). However, the scatter in this plot is considerable, as many other factors may intervene. The runoff ratio also increases with mean annual precipitation (Figure 19.2c), perhaps indicating an increase in direct surface runoff in areas with high precipitation. However, the scatter in this relationship is even greater than in the case of Figure 19.2b. Catchment area is an indicator of the path length a raindrop has to travel from the headwaters before leaving the catchment downstream and, therefore, the runoff ratio decreases with catchment area (Figure 19.2d). Because of the negative relationship between the percentage of arable land in a catchment and the cropland specific discharge (m3/km2/day, see above), we expected that the former would be a major variable relating to the runoff ratio. Indeed, the percentage of cropland in the catchments is more significantly related to the runoff ratio than any other variable available, but the pattern of the relationship is somewhat surprising (because it is a step function, see Figure 19.2e). As long as the cropland area in a catchment does not exceed 25%, the runoff ratio is relatively high. Above that threshold, the runoff ratios scatter across the entire range, suggesting that (depending on other factors) using land to grow crops may have a variety of different consequences for the water budget, including a more or less

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FIGURE 19.2 Runoff yield patterns across 128–142 functional hydrological catchments [entire catchments or smaller, sub-catchments (situated upstream) of larger, entire catchments]. (a) Frequency distribution of the runoff ratio (RUN-RAT). (b–f) For catchments with RUN-RAT <1 (N = 128), plots of RUNRAT versus (b) mean annual air temperature (MA-TEMP) (R2 = 0.158, P < 10 5), (c) mean annual precipitation (MA-PREC) (R2 = 0.113, P < 10 3), (d) catchment area (CAT-AREA) (R2 = 0.138, P < 10 4), (e) cropland area (CROP-AREA) (R2 = 0.260, P < 10 9) and (f) urban area (URB-AREA) (R2 = 0.153, P < 10 5).

complete use of river discharge in heavily irrigated areas. Finally, urbanization affects runoff ratios in a complicated way because (i) groundwater extraction for water supply lowers the water table, (ii) supply pipes leak, (iii) sewers can drain groundwater, (iv) impervious surfaces prevent groundwater recharge and (v) sewage treatment plant effluents and sewer overflows produce instream discharge (Statzner & Sperling 1993). Overall, these potential factors seem to reduce the runoff ratio (Figure 19.2f). There is some indication, however, that in catchments with a very large

fraction of urban development, the runoff ratios may increase. Combining the five independent variables from Figure 19.2 to model the runoff ratio (Table 19.2), the model conserved the direction (+ or ) of the individual relations shown in Figure 19.2. However, it explained only 53.0% of the variability in runoff ratio. Therefore, we checked whether the remaining variables not included in the model could explain more of this variation, with the prior expectation that the actual water stress would do so. Indeed, including

Chapter | 19 European Rivers: A Personal Perspective

estimates of water stress (though only for 1995) increased the variability in runoff ratio explained (but only by 1.9%). Other variables available for the analysis did not explain significantly more of the variability the runoff ratio.

19.2.3. Fish diversity Large-scale analyses of the species richness of running water fish typically consider entire catchments (from headwaters to river mouth), because fish richness is difficult to compare

691

between entire catchments and their subcatchments (e.g. Oberdorff et al. 1997). Overall, 110 of the catchments treated in this book are entire river basins [note that fish richness data in the Introduction were based on an independent dataset (K. Tockner, personal communication)]. The total number of fish species in the catchments ranges from 0 in a small arctic stream (ignored in the subsequent analysis) to 131 in the Danube, with 50% of the catchments having <33 fish species. The frequency distribution of total fish species richness is skewed toward the low end (Figure 19.3a). A plot of FIGURE 19.3 Fish diversity patterns across 109 entire catchments. (a) Frequency distribution of the total fish species richness (TOT-FISH). (b) Plot of the native (NAT-FISH) versus the non-native (NONNAT-FISH) fish species richness (R2 = 0.320, P < 10 9). (c and d) Plots of TOT-FISH versus (c) catchment area (CAT-AREA) (R2 = 0.575, P < 10 15) and (d) runoff ratio (RUNRAT) (R2 = 0.552, P < 10 15). (e and f) Plots of the proportion of non-native fish (NONNAT-RAT) versus (e) mean annual air temperature (MA-TEMP) (R2 = 0.245, P < 10 7) and (f) personspecific (i.e. per capita) gross domestic product (PERS-GDP) (R2 = 0.037, P = 0.046).

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native versus non-native species richness indicates a positive relation between them and illustrates that the Danube (having the greatest richness) stands out from all other catchments (Figure 19.3b). This supports the view that the commonly observed positive correlation between the largescale richness of native and non-native fish species may be related to co-varying factors such as catchment size (Leprieur et al. 2008b). In addition, the plot illustrates that there has been as yet no obvious positive or negative effect of non-natives on native fish species richness. This pattern supports the view that assemblages of European stream fish are not saturated, because the glaciations eliminated many species (Oberdorff et al. 1997). As a consequence, introductions by humans or invasions of catchments by species originating from elsewhere (often from glacial refugia; e.g. Leprieur et al. 2008b) have hitherto been neutral for the richness of the native fish species. As expected, total fish species richness increases with catchment area (Figure 19.3c), but the log-transformation of these variables results only in an approximate linear relation (typical for species richness–area relationships). Furthermore, the slope (0.366 0.030) of the log–log relation in Figure 19.3c is relatively high and its intercept ( 0.0956 0.1300) relatively low, presumably because our data include a wider range (particularly toward the Arctic) of catchments than previous European studies of this relationship (Oberdorff et al. 1997; Reyjol et al. 2007). Therefore, we searched for variables explaining the residuals in the species richness–area relationship in Figure 19.3c, starting with variables indicating the strength of human impact [catchment or per capita wealth, human population density, land-use (urban, arable land, relative and absolute protected area), water stress in 1995, fragmentation, number of large dams or cities]. None of these variables significantly explain the residuals; that is, the obvious effects of dams/ fragmentation on particular fish species reported in the chapters of this book do not produce statistically robust response patterns in the overall fish species richness across European catchments. Neither did the relative and absolute area of open water in the catchment or the number of ecoregions in the catchment (i.e. other potential sources of variation in species richness) explain the residuals of that relationship. Likewise, catchments on islands have similar residuals as the mainland catchments (U-test: P = 0.0196). Among the other variables available, the runoff ratio explains most of the residuals, as the total fish species richness decreases with it (Figure 19.3d). Thus, the model combining catchment area and runoff ratio explains 70.7% of the variability of the total fish species richness (Table 19.2). In this model, runoff ratio is seemingly a synthetic variable that describes the simultaneous effects of actual climatic gradients and distance from previous glacial refugia on the current overall richness of riverine fish species (Griffiths 2006; Reyjol et al. 2007). In contrast to the total fish species richness, the proportion of non-native species across 109 entire catchments is less related to the variables provided in the individual

PART | I Rivers of Europe

chapters. Mean annual air temperature explains most of the variation in the proportion of non-native fish species, although catchments with high temperature can have a high or low proportion of non-native species (Figure 19.3e). Similarly, catchments with high per capita wealth have high or low proportions of non-native species (Figure 19.3f). In combination, these two variables explain 34.5% of the variability in the proportion of the non-native fish species across the catchments (Table 19.2). Thus, the relative importance of fish invasions increases with a combination of high temperature (indicating frequent invasions of south-western European catchments; Leprieur et al. 2008b) and per capita wealth (perhaps indicating the invasion risk associated with trade and traffic), the latter accounting for most of the global variation in non-native fish species richness in the world’s river systems (Leprieur et al. 2008a).

19.3. THE STATE OF THE CONTINENT 19.3.1. Bad News and Good News European rivers, without exception, have been profoundly altered by human population and economic growth. This ranges from the long-distance transport of airborne pollutants to the most remote areas, to the more or less complete morphological, hydrological and ecological transformation of the most affected urban rivers. In many cases, these changes are effectively irreversible, perhaps because of the replacement of the native biota by invasive species, through hydrological modification and the permanent occupation of floodplains by humans, or because some ecological regime shift has occurred. We have even managed to cause salinization of the soils of the ‘fertile crescent’, in modern-day Turkey, where humans first started farming crops 10 000 years ago at the dawn of the agricultural revolution! Nevertheless, the ecosystem goods and service provided by European rivers are still substantial, active and absolutely vital. Most crudely, this is in the form of the absorption, dilution and disposal of waste materials, of which huge amounts are evidently being dealt with. For instance, while we learn that in Greece today 90% of the human population is connected to some kind of wastewater treatment plant, >2/ 3 of this is only primary treatment, while in the remaining countries of the Balkans ‘municipal waste water is rarely treated’ (Chapter 11). In Turkey, sewage treatment is negligible outside the big cities and evidently river water quality is in decline. There is still bad news from several of the major tributaries of the Danube, most spectacularly from the third longest, the Siret, that drains parts of the Ukraine and Romania. At its mouth, mean BOD and COD are still 7 and 45 mg O2/L, respectively, and cyanide concentration (from the mining industry) has been recorded as high as 4 mg/L (the EU safe limit is 0.005 mg/L) (Chapter 3). Intensive livestock rearing also contributes to severe eutrophication and we note, for instance, that farm animals produce 230 000 tons of N and 144 000 tons of P in the Po basin of Italy each year

Chapter | 19 European Rivers: A Personal Perspective

(Chapter 12)! These are just a few of the more startling examples of statistics on pollution that are encountered everywhere in the pages of this book. There is also a great deal of good news on pollution, however. At the continental scale, water quality has improved radically over the past 20–30 years or more in the richer countries of northwestern Europe. Famous examples of recovery from (largely organic) pollution come from the Mersey, Trent and Thames in England, and from the Rhine and Elbe (both predominantly in Germany), and this story has been repeated very widely in such countries. In the Meuse, there has been a steady decrease in heavy metal pollution and a major decline in orthophosphate concentration since the 1980s. We were also struck by the observation that ‘in the Upper Danube . . . mostly clean water flows through heavily modified channels’ while in the Middle and Lower Danube ‘polluted water flows in more intact channels’ (Bloesch 1999; Chapter 3). Clearly recovery, at least from gross organic pollution, has been achieved over large parts of the continent and is achievable elsewhere with time and sufficient resources. Less tractable are a range of toxic substances, encompassing pesticides, pharmaceuticals including (but not exclusively) endocrine disruptors, and metals. Moreover, almost all lowland rivers in Europe remain firmly hypernutrified, with many times more fixed nitrogen and phosphorus than the natural background. For instance, it is calculated that the nitrogen and phosphorus loads in the huge Danube system are about 10 times increased over the pristine system. This must have enormous consequences for the functioning of river ecosystems, which are not yet completely understood.

19.3.2. Flow Regulation, Impoundments, Abstraction and Connections Large lowland rivers in industrialized Europe are largely regulated for navigation and flood control, with little or no contact with floodplains and riparian wetlands, though there are some encouraging examples of reconnections and restoration of at least some fragments of the original river morphology and dynamics. Statistics about the number of dams and impoundments on European rivers are at the same time disturbing and impressive. Clearly, humans have sought for a very long time to control dangerous floods, store water for use during droughts, and to generate power. We learned that there are >6000 large dams (>15 m high) in Europe, with 20% in Spain alone, and that only one (the Northern Dvina in Russia) of the 20 largest European rivers is free flowing. The litany of figures on the total numbers of dams and impoundments in individual rivers, however, is staggering. The river network of the Garonne has 920 artificial barriers, comprising 90 retention dams and 803 artificial waterfalls that constrain fish migration along the river, yet it is still described as ‘one of the least regulated of the French rivers’! Europe’s greatest river, the Volga, has 12 very large reservoirs with a total storage of 168 km3 and total area

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>23 000 km2, nine of them on the main river itself. Much of the river’s course is described as a ‘cascade of large shallow reservoirs’ and its flow regime is now largely determined by reservoir managers. Similar descriptions apply to the Dnieper (Europe’s third largest river) and many others. Only 15% of the length of the Danube upstream of Bratislava (1000 river km) remains free flowing. Spain alone has over 1000 reservoirs along its largest rivers, in a region where tensions over water supply are rising sharply. Flow in Iberian (and other) rivers is greatly threatened by water abstraction (Chapter 4). To mention just one example, in the Guadiana (shared by Spain and Portugal) progressively greater water abstraction in 1960s and 1970s was unsustainable and several aquifers became overexploited, while regulations on abstraction are difficult to enforce because of resistance by farmers wanting to irrigate their crops. Groundwater depletion has sharply decreased surface flows over the past 30 years, and drying of several km of the upper Guadiana over 15 years caused severe damage to riparian forests. Here the water table was lowered by 30–40 m below the river channel, the river flowing only in a wet period in 1995/1996. The ecological consequences of all this regulation of flow, loss of river dynamics and longitudinal fragmentation of river systems are too profound and complex to deal with in a few lines, but we would mention some impacts that really stand out from the pages of this book. The first is the loss of large migratory fishes – and in particular of the iconic sturgeons. Time and again we read of collapse or extinction as a consequence of restriction to migration caused by dams and other insults. Thus, sturgeon went ‘extinct in the Elbe in the middle of the 20th century’, ‘disappeared from the Vistula almost a century ago’, ‘after construction of (the) Dubossary dam, sturgeons and many species of semi-migratory fish were lost from the Dniester’, and one of the six species of sturgeons in the Danube is extinct, a second on the verge of extinction and the others threatened. In France, the sturgeon ‘is the only native fish to have become extinct within the Loire basin’, and (in the Garonne) ‘Sturgeon catches dropped from several thousand in the 1960s to about 10 in the 1980s when the species became completely protected’. Sturgeons are perhaps the most sensitive of all fishes to river fragmentation and the prevention of their longitudinal breeding migrations, but other migratory fishes have also declined almost everywhere, including eels, shads and salmonids. Prevention of longitudinal exchange and dispersal of individuals must have affected many other species of animals and plants, about which we know much less. It is a major irony that the longitudinal fragmentation of rivers by dams and pollution, and the disconnection of rivers laterally from their floodplains, has at the same time been accompanied by the large scale connection of major river systems by navigation canals, water diversions and via marine shipping. Whereas many species can no longer migrate within their native catchments, routes for dispersal across formerly impassable watersheds have now been opened up. Such dispersal has evidently increased enormously, usually

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aided by trade and traffic in combination with particular biological traits that favour dispersal and/or the foundation of new populations (P€ ockl 2007; Statzner et al. 2008). Invasive species, in Europe particularly passing along the ‘southern invasive corridor’ from the Ponto-Caspian via the Danube and the Danube-Main-Rhine canal to the Rhine and the Atlantic and beyond, are a spectacular example of the ecological effects of the removal of barriers to dispersal and its potential to homogenize the biota. The cleaning up of the Rhine after major industrial pollution and the Sandoz disaster of 1986 (Chapter 6), a major success story in terms of water quality, has opened up the river to a benthic community dominated by alien species, and the native community of insects has been replaced by non-native crustaceans and molluscs, now making up >90% of the total biomass and density. Perhaps the most invasive freshwater organism of all, the zebra mussel, has been widely dispersed by ships. Its expansion and effects have most widely been documented in North America but it is widespread and extremely abundant in Europe too. This is true of the Bodensee (Lake Konstanz) on the Upper Rhine, and in Lake Peipsi (on the Narva River in the Eastern Baltic), where its biomass now exceeds that of all other benthic and planktonic invertebrates and fish – combined (Chapter 16). Thus, while there is as yet no statistical evidence of a decline in the species richness of native fishes caused by non-natives (Figure 19.3b), this probably would not be the case with invertebrates. Even with the fish, there are many accounts in this book of the replacement of rheophilic migratory and non-migratory species by generalist non-migratory species when rivers are regulated. Another major impact of longitudinal fragmentation is that, in many instances, sediment supply (so crucial to river morphology and dynamics), has been truncated by solid material being retained in impoundments and dams, leading to the incising of channels downstream. This is also rather ironic, since sediment yields from catchments under agricultural and urban land-use has certainly increased as erosion has accelerated. For instance, about 30% of the Dubossary reservoir on the Dnieper is already filled by deposited sediments because it intercepts 95% of the particles transported by the river. Downstream of the dam, the riverbed has been incised on average by 0.8 m. Further examples come from the Danube, Spree, Rhine and Elbe (where downstream of impoundments in the Czech section of the river the channel has incised by 1.6 m).

19.3.3. The Future The future is a complicated and unpredictable place! Recent attempts to forecast the state of rivers and streams over the next few decades have been fraught with uncertainty about the likely extent and impact of future climate change and its importance relative to more familiar threats to rivers from human population and economic growth (Allan & Benke 2005; Malmquist et al. 2008). The WFD makes no mention of climate change, and it is undeniable that humans have

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been devastatingly successful at downgrading the ecological health of Europe’s river systems using conventional means. Moreover, we can see clear signs of future changes in the state of the environment consequent upon unprecedentedly rapid socioeconomic trends. Yet some of these socioeconomic trends, including human population movements, may already be reflecting changes in the global climate, and there are some signs of recent climate change in the rivers of Europe, particularly around the Mediterranean (to add to that detected via anomalies in the runoff ration in far northern rivers – see above). In Turkey, there has been a significant decrease in river discharge in the Mediterranean, Aegaen, Marmara and Central Anatolia regions (Chapter 17), partly reflecting a drying climate. In the Arno basin of Italy, there has been a modification in rainfall events over 30 years, with a marked increase during autumn (September–November) and a reduction in winter (Chapter 12). There are also indications of rising temperature in UK streams (Durance & Ormerod 2007, 2008). Already, there are many catchments that approach the limit of water supply needed for domestic and industrial use or cropland irrigation (as was again apparent in our analysis of runoff-ratios), and the relative importance of biotic invasions increases with temperature (Figure 19.3e). If we do reach a situation of runaway climate change, the consequences for water supply, floods and droughts, let alone river health, will be serious indeed. We can be clear about conflicts between economic growth and the health of Europe’s rivers, which are evident from historical trends and clear from the chapters in this book. Industrial and population growth in western Europe put severe pressures on river systems in the 19th and 20th centuries, which were largely dealt with on the grounds of human health and welfare using engineering solutions to sewage and water treatment. Post-industrialisation has seen a remarkable transformation in river health, at least as measured by ameliorating water quality. In eastern Europe, improvements in water quality have been much less and were delayed until the collapse of communism – but have since been encouraging. The conflicts between rapid development, human population growth, water supply for human use, and the economic resources needed for river restoration and river health are now much starker in the south and east of the continent – and some worrying trends are evident. Sabater et al. (Chapter 4) write that, ‘People in arid and semi-arid regions have the least respect towards rivers since the rivers are often dry or have catastrophic floods, and are therefore viewed more as a danger than as a natural resource to be preserved. Moreover, there is a well-rooted perception that any water that reaches the sea is wasted.’ There is thus an important job to be done on public attitudes, and the ecosystem services provided by functioning land–ocean interactions need to be demonstrated more clearly. A further example of recent conflicts between the environment and economics come from the western Steppes, where economic considerations dominate decision making more than elsewhere. The Ukrainian government went ahead with construction of the

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Tashalyks hydro-nuclear power station and a large reservoir on the Southern Bug that will cause dramatic ecosystem changes downstream and seriously impact the terrestrial ecosystem of the Basalt Steppe Pobuzhe (Chapter 13). By far the most complicated river basin in terms of the conflict between economics and environment is the Danube, which is seen as key to improvements in transport links between eastern and western Europe. Here the European Union plans to develop the Trans-European Networks for Transport (TEN-T) Corridor VII. This aims to remove navigation ‘bottlenecks’ (i.e. natural river morphology) along much of the Romanian-Bulgarian section of the Danube, a long stretch in Hungary, and hitherto free-flowing sections downstream of Vienna in Austria, and elsewhere. In addition, the proposed Danube–Oder–Elbe Canal would affect 46 000 ha of 38 protected areas, including two national parks, six Ramsar sites and two biosphere reserves (Chapter 3). The pressure for rapid economic development is particularly great in Turkey, where there is an accelerating demand for water for irrigation and for hydropower (Chapter 17). These will inevitably cause further environmental damage. The Turkish government plans 22 new dams and 19 hydroelectric power plants on the Euphrates and Tigris Rivers and their tributaries. This will help develop southeastern Turkey (a known biodiversity hotspot) with its large human population and high levels of unemployment and political instability, but risks conflict through the resettlement of people, destruction of historic sites, and environmental and social impacts (let alone problems over water with the states downstream). Also in Turkey, the Coruh ¸ basin borders Georgia and the largely unregulated river flows into the Black Sea. However, about 27 dams and hydropower plants are planned for the Coruh ¸ River and its tributaries to meet increasing energy demands, expecting to reach 10 500 billion kWh. As long as these socioeconomic trends continue, and particularly if the climate becomes drier, the demand for water and power seems set to increase and we will face stark choices over the fate of rivers everywhere (the examples we have mentioned here are just some of the more obvious ones). Even many Arctic rivers in remote and thinly populated areas, will be further affected by exploitation of oil, gas, minerals and hydropower. All these create real challenges to river managers and scientists. Yet we must not forget the natural resilience of rivers, and the near miracles of recovery from pollution that have already been achieved. We need to provide a means by which the immediate needs of people and those of the environment (which are also the needs of people in the long-term) can as far as possible be reconciled.

19.4. POLICY – WHAT WE SHOULD DO None of us has all the answers in the area of policy for the sustainable management of rivers. The issues and conflicts are extremely challenging. Perhaps the main achievement of this book is to line up, one after another, accounts of many of

Europe’s river systems, when the common repeated themes of conflicting pressures and problems become obvious.

19.4.1. Are Rivers Particularly Problematic? It seems so to us. Of course, conservation is always challenging in reconciling the needs of natural systems with the pressures for development. However, one cannot ever actually or conceptually ‘fence off’ a river and hope to protect its biodiversity or ecosystem processes. Water is far too dynamic in the landscape, and it is an undoubted achievement of modern ecology that we now appreciate just how much water integrates the dispersal and transformations of chemicals, particles and organisms in river catchments. The socioeconomics of fresh water also intervene too profoundly. People need rivers, but fear them, and this is part of our nature as a species. We think rivers are beautiful and exhilarating, but also regard them as dangerous and untrustworthy. It is perhaps not surprising then that managing rivers everywhere seems to involve complex combinations of disciplines (hydrology, engineering, ecology, sedimentology, chemistry), but also consortia of interests and ‘stakeholders’ (landowners, local or national governments, pressure groups, river authorities, power companies and many others). This is particularly obvious from the examples in this book. Such management arrangements are often organized at the catchment scale (thus reflecting a natural unit of the landscape) and, because catchments of continental rivers can be so large, cross-national cooperation is often required. The prime example in Europe is the International Commission for the Protection of the Danube River (ICPDR), for the Danube is the most international river in the world. There are many other examples of river basin authorities scattered throughout this book and integrated catchment planning is the flavour of the day (and enshrined in the WFD) – even though it is extremely difficult to put into practice when apparently irreconcilable objectives have somehow to be reconciled. Nevertheless, we see no alternative and this work must go on.

19.4.2. Conserve or Restore? Should we give most attention to conserving what is left, or to restoring what has been lost? A fairly resounding consensus is apparent about this question: the very highest priority should go to conservation (Chapter 3; Boon 2005). Of course, we should both conserve and restore, but conservation is likely to be more cost-effective, not least because it is not clear how far restoration is possible or effective. The designation of freshwater sites for protection is a difficult business (Mainstone 2008), but some systems present themselves to us from this compendium of European rivers. These candidates for protection are all ‘big’ systems, covering large (sometimes huge) areas and subject to conflicting demands by the people who live in or near them. Thus the challenge is to show why the price of a lost economic opportunity should

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be paid, by restricting development in protected sites, when such developments have been allowed elsewhere. It seems to us that the kinds of ecological and morphological damage to river systems that are themes throughout this book are not truly global, in the sense that climate change or the long distance transport of airborne pollutants to remote areas may be thought of as global. They are global only in the sense that they are being repeated everywhere (Malmquist et al. 2008) producing global change through ‘death by a thousand cuts’. In any local conflict of interest between potentially damaging developments and conservation, the economic interests of people usually take precedence (see, for instance, Chapters 17, 3, 13, 4 and others). A wider context thus seems necessary, in which the value of the ‘last wild river’ is enhanced by its rarity in a crowded continent, thus leading to a decision to conserve its natural dynamics and biodiversity. International oversight and agreements are crucial in this and, perhaps, compensation to local communities for lost economic opportunities, although there is also an alternative economic value in natural ecosystems and their goods and service. We do not underestimate the difficulties of such a proposal. The systems mentioned here are merely examples of those that need protection – there are certainly others with good claims. In this book we see arguments, for instance, for the conservation of the few lowland floodplains of the Danube and its tributaries the Savam, Drava and Tisza (all of them highly impacted rivers), and continued strict protection of the UNESCO Biosphere reserve in the Danube Delta (Chapter 3). The Isar is described as one of the last natural Alpine rivers in Europe, a title also claimed for the Italian Tagliamento, which is apparently a reference system for a braided river – strict controls must surely be imposed on its proposed development (Chapter 12). The Drawa River in northwest Poland, lying within the Oder drainage, is also an obvious candidate for further strict protection and rehabilitation, since it is one of the few lowland rivers of its size left in the region with anything approaching natural dynamics (Chapter 14). This would also apply to the River Frome in southwest England, which is unimpounded, has an active floodplain and a natural run of salmon (Chapter 10). Of really large rivers, a priority for protection is the Ural, the third longest river in Europe and the last where sturgeons still reproduce naturally in large, even if reduced, numbers. The conservation and sustainable management of the unique ecosystems along the Ural corridor and along the coastal shore areas are of global importance. Its largest right bank tributary, the Sakmara, is the largest free-flowing river remaining in the entire Ural basin, and is in close to reference conditions for a steppic river (Chapter 18). This system is of the very highest priority for conservation.

19.4.3. ‘Technical Fixes’ While conservation of such key sites and systems is the highest priority, the vast majority of our continent is in far

PART | I Rivers of Europe

worse condition and this cannot be ignored. The EU’s WFD aspires to restore all European freshwater bodies to ‘good ecological status’ by 2015, which seems to us (particularly after having read this book) to be a wildly optimistic target and an even more wildly optimistic timeframe. Thus, of the large, industrialized, regulated and eutrophic River Meuse, it is said, ‘Implementing the Water Framework Directive on such a river, and in particular achieving the objective of “good status” or “good potential” is not a simple task and necessarily involves coordination at an international level’ (Chapter 5). This seems to be true of most of the larger European lowland rivers. Nevertheless, targets are there to be aimed at and river ecosystems can recover. We cannot deal here with all the techniques that can be used to restore water quality in rivers. Clearly we require the expansion of water treatment facilities (to tertiary standards in some cases), reductions in the application of increasingly expensive fertilizers to agricultural land, increasing efficiency in our use of water, and restrictions on the urbanization and disconnection of flood plains. We also need to find ways of reducing the load of metals, pharmaceuticals and pesticides to our rivers. Beyond the restoration of water quality, we need to increase the connectivity within catchments, both along the river continuum and between the main river channel and its floodplain. For example, the design and efficiency of fish passes should be improved, particularly for large migratory species. Other measures focusing on river morphology and discharge (quantity and variability) should restore physical habitat conditions. The idea of river restoration has a mixed history, but will certainly have a role in river management. Small-scale modifications of habitat, such as the placing of a few riffles and flow diversions, isolated in otherwise degraded catchments, seem to have had little benefit, despite substantial cost (e.g. Pretty et al. 2003; Harrison et al. 2004). The restoration of the Danish River Skjern (Chapter 14) is an encouraging example, however. In an earlier drainage project, the lower 20 km of the main channel had been straightened, flooding prevented by large dykes and the groundwater table lowered by pumping. This yielded 4000 ha of arable farmland from what was previously meadows and wetlands, the area of the latter being reduced to only 430 ha. The modern-day cost of this is estimated at e27 million (Chapter 14). Barely had it been finished than it was decided to reverse it, with the objectives of increasing nutrient retention capacity, providing a wetland for migratory birds, improving fisheries and promoting ecotourism. The key was its large scale and that most of the area (19.5 km2) was purchased from the farmers. The river was re-meandered and natural water levels and water level fluctuations restored, at a cost approximating that of the original drainage scheme. The restoration of the Skjern was broadly successful, with benefits to biodiversity and ecosystem function, with a reduction in inputs of fixed nitrogen also playing a role. There are other examples of large-scale restoration projects on European rivers, including the rehabilitation of substantial areas of floodplain on the

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Austrian Danube downstream of Vienna, on the French Rhone and on the Rhine; size clearly matters on big rivers. Finally, the idea of ‘giving rivers space’ is prominent throughout this book – though we would like to see more critical assessment of its efficacy. In the absence of more precise knowledge, protection of riparian corridors (not mere thin strips of trees) within which river dynamics can occur is likely to be beneficial. The costs of this can be offset by use of EU subsidies to farmers and land-owners for environmental purposes, and perhaps because restoring river ecosystem processes could substitute for the ultimate and expensive stages of water treatment. Hydrologically active source areas of catchments might also be a focus of protection. Whether restoration of riparian and other wetlands could actually reduce the frequency and severity of damaging floods (a muchdiscussed ecosystem service) must depend on their extent relative to the size of the catchment, but could certainly help.

19.5. SCIENCE – WHAT WE NEED TO KNOW There is a debate to be had about whether we already know enough to be able to manage river ecosystems effectively or need more research. Already, we do have tools to help river managers because we can usually give informed general advice and, in some cases, have created river specific management tools. However, there remains much to do, as we think is evident from these accounts of European rivers. While not able to offer an exhaustive research programme for European river research, some areas seem particularly pressing. We can group these into three main categories: (a) research surveys providing basic information and descriptions, (b) research directly supporting management and (c) conceptual issues in river ecology. It is evident (a) that even basic descriptions of the environment, biota and ecosystem processes in many of Europe’s larger river systems and wetlands (particularly in the south and east of the continent) are missing. For instance, details of the biota of rivers in Turkey, on the Volga and Ural Rivers, and in the Balkans are at best inadequate, and this makes decisions on environmental protection and resource management, as well as assessments of ecological status, problematic. Even our ability to identify many river organisms is limited in such areas. Unfashionable though it may seem, a thorough programme of ecological survey backed up by taxonomic effort is required. This should not be just conventional taxonomy, moreover. Our knowledge is least in biodiversity hotspots (Turkey, the Balkans), and additional genetic research to reveal cryptic diversity and threatened genotypes is well justified in such areas. A particularly pressing need for management (b) is for better, ecosystem-based, indicators of ecological status. The chapters in this book (an exception is the account of the Elbe) are almost silent on characterising or measuring ecosystem processes. Yet promising techniques are now available and widely used in fundamental research, including whole

stream metabolism, stable isotope techniques, automatic monitors of greenhouse gas fluxes from rivers, and molecular probes. We should be researching how such measures can give us a better handle on the state of river ecosystems, to supplement rather than replace established tools based on community structure. Technical applied research is also required, for instance, on analysing and assessing the importance of new pollutants, including novel and powerful pharmaceuticals, nanoparticles and others. More conceptually (c), large rivers and river-floodplain systems offer fascinating challenges to ecological theory, that if resolved will provide a basis for future management and conservation. Many large European rivers now consist essentially of hypernutrified water constrained within defended banks. This must contrast with the ‘pristine’ state of vanishingly low concentrations of plant nutrients but with large amounts of recalcitrant woody detritus on active floodplains and deposition zones. This must completely change ecosystem processes and the balance of allochthonous and autochthonous carbon in the ecosystem. Studies on river metabolism on these highly modified systems, in comparison with less impacted ones, will be instructive. Beyond ecology, we think that the relationships between ecosystem and human health (including its physical and psychological component) is worthy of exploration, as is economic research on the costs and benefits of river modifications taking into account the losses of ecosystem services and of the impact of invasive species. Overall, an excellent step would be to establish a number of key catchments across Europe that could provide foci for both strategic and fundamental research. Ideally, these would include sites with long runs of background data and where ‘reference conditions’ (in the terminology of the WFD) could be objectively defined, and would provide secure access to researchers and include facilities for manipulative or statistical experiments at large scales. Against such reference sites, gradients of human pressures would enable us to define reductions in ‘ecological status’ and to learn about ecological responses to ‘cocktails’ of stressors on natural ecosystems. Whatever we find out about Europe’s rivers, the most important lesson will be to learn to work with, rather than against, them. This means assuring their ecological health into the future so that limiting freshwater resources are not lost, that the cultural, aesthetic and economic value of rivers is conserved, and that we give them sufficient room so that they do not endanger human well being. Perhaps, therefore, the biggest challenge of all will be to change public attitudes to these fluctuating and dynamic ecosystems, which will be near the forefront of landscape responses to a changing climate.

Acknowledgements We thank the editors for their invitation to write this personal perspective and to the authors of individual chapters for all their hard work.

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REFERENCES Allan, D.J., and Benke, A.C. 2005. Overview and prospects. In: Benke, A.C., Cushing, C.E. (eds). Rivers of North America, Elsevier Academic Press. Benke, A.C., and Cushing, C.E. 2005. Rivers of North America. Elsevier Academic Press. Anon. 1998. Special report No. 3/98 concerning the implementation by the commission of EU policy and action as regards water pollution accompanied by the replies of the commission. Official Journal of the European Communities C191: 2–44. Bloesch, J. 1999. The International Association for Danube Research (IAD): its future role in Danube research. Archiv f€ ur Hydrobiologie Supplementband 11(3), 115(3): 239–259 [Large Rivers]. Boon, P.J. 2005. The catchment approach as the scientific basis of river basin management. Archiv f€ ur Hydrobiologie Supplementband 16(1–2), 158 (1–2): 29–58 [Large Rivers]. Burt, T.P. 1992. The hydrology of headwater catchments.Calow, P. and Petts, G.E. editors. The Rivers Handbook Vol. 1: Blackwell, Oxford, , 3–28. Cushing, C.E. Cummins, K.W. and Minshall, G.W. (eds). 2006. River and Stream Ecosystems of the World, Elsevier Academic Press. Durance, I., and Ormerod, S.J. 2007. Climate change effects on upland stream macroinvertebrates over a 25-year period. Global Change Biology 13: 942–957. Durance, I., and Ormerod, S.J. 2008. Trends in water quality and discharge confound long-term warming effects on river macroinvertebrates. Freshwater Biology, DOI: 10.1111/j.1365-2427.2008.02112.x. Griffiths, D. 2006. Pattern and process in the ecological biogeography of European freshwater fish. Journal of Animal Ecology 75: 734–751. Gustard, A. 1992. Analysis of river regimes.Calow, P. and Petts, G.E. editors. The Rivers Handbook Vol. 1: Blackwell, Oxford, , 29–47. Harrison, S.S.C., Pretty, J.L., Shepherd, D., Hildrew, A.G., Smith, C., and Hey, R.D. 2004. Rehabilitation of lowland rivers: the effects of instream structures on macroinvertebrates. Journal of Applied Ecology 41: 1140–1154. Kaika, M., and Page, B. 2003. The EU water framework directive: part 1. European policy-making and the changing topography of lobbying. European Environment 13: 314–327. Leprieur, F., Beauchard, O., Blanchet, S., Oberdorff, T., and Brosse, S. 2008a. Fish invasions in the world’s river systems: when natural processes are blurred by human activities. PLOS Biology 6: 404–410.

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Leprieur, F., Beauchard, O., Hugueny, B., Grenouillet, G., and Brosse, S. 2008b. Null model of biotic homogenization: a test with the European freshwater fish fauna. Diversity and Distributions 14: 291–300. Mainstone, C.P. 2008. The role of specially designated wildlife sites in freshwater conservation – an English perspective. Freshwater Reviews 1: 89–189. Malmquist, B., Rundle, S.D., Covich, A.P., Hildrew, A.G., Robinson, C.T., and Townsend, C.R. 2008. Prospects for streams and rivers. In: Polunin, N.V.C. (ed). ‘Aquatic Ecosystems; Trends and Global Prospects’, Cambridge University Press, Cambridge, UK, pp. 19–29. Oberdorff, T., Hugueny, B., and Guegan, J.-F. 1997. Is there an influence of historical events on contemporary fish species richness in rivers? Comparisons between Western Europe and North America Journal of Biogeography 24: 461–467. Page, B., and Kaika, M. 2003. The EU water framework directive: part 2. Policy innovation and the shifting choreography of governance. European Environment 13: 328–343. P€ockl, M. 2007. Strategies of a successful new invader in European fresh waters: fecundity and reproductive potential of the Ponto-Caspian amphipod Dikerogammarus villosus in the Austrian Danube, compared with the indigenous Gammarus fossarum and G. roeseli. Freshwater Biology 52: 50–63. Pretty, J.L., Harrison, S.S.C., Shepherd, D.J., Smith, C., Hildrew, A.G., and Hey, R.D. 2003. River rehabilitation and fish populations: assessing the benefit of instream structures. Journal of Applied Ecology 40: 251–265. Reyjol, Y., Hugueny, B., Pont, D., Bianco, P.G., Beier, U., Caiola, N., Casals, F., Cowx, I., Economou, A., Ferreira, T., Haidvogl, G., Noble, R., De Sostoa, A., Vigneron, T., and Virbickas, T. 2007. Patterns in species richness and endemism of European freshwater fish. Global Ecology and Biogeography 16: 65–75. Simonovic, S.P. 2002. World water dynamics: global modeling of water resources. Journal of Environmental Management 66: 249–267. Statzner, B., Bonada, N., and Doledec, S. 2008. Biological attributes discriminating invasive from native European stream invertebrates. Biological Invasions 10: 517–530. Statzner, B., and Sperling, F. 1993. Potential contribution of system-specific knowledge (SSK) to stream management decisions: ecological and economic aspects. Freshwater Biology 29: 313–342. Whitton, B.A. (ed). 1984. The Ecology of European Rivers, Blackwell Scientific Publications, Oxford, UK.

Chapter 1

Index A Aare, 199 Acheloos, 422, 423, 426, 428, 430-432, 434, 435, 438, 439, 442-444, 448-451, 453-458, 464 Aggitis, 422, 428, 434, 439, 442, 444, 462 Ain, 247 Alfeios, 422, 424, 425, 430, 432, 433, 438, 439, 443-445, 448-451, 454, 457, 458, 462, 464, 465 Aliakmon, 422, 425, 430, 431, 433, 435, 437, 439, 441-445, 448-450, 454, 455, 457, 458, 462 Almopeos, 422, 433 Alta See Altaelva Altaelva, 337 Aoos, 422, 424, 426, 428, 432, 434, 436, 439, 442-445, 448-450, 453, 454, 456-459, 461 Arachthos, 422-424, 427, 431, 432, 434, 435, 438, 439, 443-445, 440-451, 454-457, 463, 465 Arda, 422, 434, 436, 442, 448 Asi, 643 Atna, 582-584 Axios, 422, 429-432, 434, 435, 437, 439, 441445, 448-450, 453-459 B Bayelva, 338 Belá, 60 Bijala Mesta, 434 Bjøra, 601, 602 Black Drin, 422, 441 Bøvri, 583 Breelvi, 596-598 Bregalnica, 433, 442 Bug, 462, 607 Buna, 422, 441, 456, 457, 459 C Cherna Mesta, 434 Creuse, 685 Crna, 422, 433, 442 D Dal River, 297 Danube, 60, 421, 428, 453, 455 Lower Danube, 428 Djupa, 585 Dospatis, 422, 442

Index.indd 699

Dospatska See Dospatis Drawa, 525 Drim See Drin Drin, 422, 433, 434, 439, 441, 442, 445, 448, 453, 455, 456, 458-460, 464 Drino, 422, 432, 448 Duero, 114 Durance, 248 Dvina See Northern Dvina E Ebro, 114 Elbe, 525 Em, 525 Enipeas, 423 Era, 421, 435-437 Erdalselva, 598, 599 Ergene, 422, 431, 434, 442 Evinos, 463 Evros, 422, 424, 430, 431, 433-436, 439, 442445, 448-455, 457-459 Evrotas, 422, 424, 425, 427, 430, 432, 439, 443-445, 448-451, 453-455 G Gallikos, 433 Gallo, 460 Geithellnaá, 338 Glitra, 583 Glomma, 577, 581-585, 605 Grana, 600 Guadalquivir, 114, 455 Guadiana, 114 H Heinelva, 585, 587 Hjelledøla, 598, 599 I Ilek, 448, 456, 673 Inn, 60 Inna, 600 Iskar, 435 J Jostedøla, 577, 595-598 K Kalaritikos, 431, 432 Kama, 24

Kamchia, 422, 429, 439, 441-445, 448, 449, 451, 452, 458, 465 Kara, 643 Komagelva, 337 Koutajoki, 297 Krundøla, 596, 598 L Ladon, 425, 438, 443, 449 Lærdalselva, 577 Laxá, 338 Logna, 588, 590 Loudias, 433, 457 Louros, 431, 432, 454-456, 465 Lyon, 247 M Main, 24, 199, 247, 422, 431-437, 442, 443, 449, 451, 452, 456, 457, 463, 578, 581, 582, 588, 590, 594, 595, 597-604 Malakasiotikos, 433 Mandalselva, 577, 588-590 March, 439, 442, 444, 462, 463, 581, 584, 586, 589, 592, 594, 597, 600, 673 Maritsa See Evros Megdovas, 423 Meriç See also Evros Mesta See Nestos Meuse, 151 Mezen, 338 Mjølkelva, 598, 603 Moldova, 497 Mondego, 114 Monn, 588 Moraca, 436, 441 Morava, 60, 453 Mørkedøla, 594 Moselle, 199 N Namsen, 577, 601, 602 Narew, 607 Narva, 608 Neckar, 199 Nemunas, 607 Neretva, 422, 428, 430, 432, 434-436, 439, 441, 444, 445, 448, 453, 456-461, 463 Nestos, 422, 430, 431, 433, 435, 436, 439, 443445, 448-452, 454-459, 462-464 Neva, 297

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700

Northern Dvina, 338 Numedalslågen, 582 O Oder, 525 Oka, 24 Olt, 60 Onega, 337 Onochonos, 423 Or, 24, 60, 151, 199, 247, 337, 381, 421-423, 429, 432, 435-437, 439, 443-445, 449-459, 463, 466, 467, 497, 525, 578-581, 584-586, 592, 594, 596, 600, 603, 604, 643, 673, 685 Orava, 60 Orkla, 577, 599-601, 605 P Pechora, 338 Pilica, 607 Pinios, 422, 423, 431, 433, 435, 438, 439, 443445, 448-450, 452, 456, 458 Pinios (Pelopones), 422, 423, 431, 433, 435, 438, 439, 443-445, 448-450, 452, 456, 458 Pinios (Thessaly), 422, 423, 431, 433, 435, 438, 439, 443-445, 448-450, 452, 456, 458 Po, 337, 439, 467 Prut, 60 R Raubekken, 600 Rauma, 583 Rena, 582 Rhine, 199 S Sakmara, 673 Sanddøla, 601, 602

Index.indd 700

Index

Sava, 60 Save, 421 Segura, 114 Sheksna, 24 Siret, 60 Skarmodalselva, 602 Skjerka, 588 Skjern, 526 Smedøla, 594 Sperchios, 422, 423, 430, 433, 439, 443–445, 449, 451, 453, 457, 458, 461, 465 Spree, 526 Store Fiplingdalselva, 602 Striama, 430 Struma See Strymon Strumeshnitsa, 422 Strymon, 422, 428, 430, 431, 433–435, 437, 439, 441–445, 448–450, 452, 454, 457, 459, 464 Stryneelva, 577, 598, 599 Such, 427, 428, 436, 437, 439, 443–445, 451– 457, 459, 581, 590, 592, 597, 599, 601, 604 Suldalslågen, 582 Susna, 598, 602 Svenningdalselva, 602, 604 Svorka, 601 T Tagus, 114 Tana, 337 Tarn, 581 Tavropos See Megdovas Ter, 114 Tern, 60, 247, 455, 607 Thyamis, 453 Tisza, 60 Torne River, 297

Trebisnjica, 422, 441 Treklyanska, 422, 433 Treska, 433, 442 Tundja, 422, 430, 434, 436, 442, 445, 448, 459 Tunnsjøelva, 601 Túr, 60 U Ume River, 297 Unkra, 602 Ural, 3, 673 Uvdalselva, 585 V Vardar See Axios Varzuga, 337 Vefsna, 578, 598, 602-605 Velika Morava, 60 Venetikos, 422, 433 Vistula, 607 Little Vistula, 607 Upper Vistula, 607 Middle Vistula, 607 Lower Vistula, 607 Vjose See Aoos Volga, 24 Upper Volga, 24 Middle Volga, 24 Lower Volga, 24 W Weser, 525 Western Dvina (W Dvina), 608 White Drin, 422, 433 Z Zagori, 432

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