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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

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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

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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).

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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).

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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).

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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

248

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