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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
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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
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Foreword
I am grateful for the opportunity to write the foreword for Rivers of Europe as it represents the European counterpart to Rivers of North America, edited by Bert Cushing and myself (Benke and Cushing 2005), and is also published by Academic Press/Elsevier. Editors Klement Tockner, Urs Uehlinger, and Christopher T. Robinson believe as we did that comprehensive description of a continent’s rivers is essential if human societies are to have any hope of understanding and wisely managing our fresh water resource and the rivers within which it flows – now and into the future. This book is important for one simple reason: fresh water is the single most important natural resource on earth. Consider that in looking for past or current life on other planets, finding evidence of water is a primary goal. Without fresh water, inland environments would be lifeless. Rivers of Europe represents by far the most comprehensive effort to describe Europe’s rivers to date. This outstanding reference contains an enormous amount of information in characterizing and synthesizing natural features of rivers and their drainage basins (catchments), including such things as climate, land use, hydrology, and biodiversity. It also highlights environmental issues of great importance to citizens and governments, including fragmentation by dams, pollution, introduction of nonnative species, and reductions in biodiversity. Although the book deals with serious issues, it will be a pleasure to read for both professional and layperson with its many beautiful maps and photographs, as well as extensive data tables that allow comparisons of physical and biological features between rivers and across regions. The editors have assembled a team more than 130 river experts from throughout Europe to describe most rivers of the continent. Included are 165 rivers from the Atlantic Ocean to the Ural Mountains and Caspian Sea. In some ways, creating Rivers of Europe surely was an even greater challenge than Rivers of North America since editors had to work with authors from many more countries and native languages. Nonetheless, this unique compendium is the result of meeting that challenge and producing what should become a standard reference for many years to come. There are interesting contrasts between North American and European rivers. The land area of Europe is roughly half that of North America, yet European rivers are found in 48 countries rather than three. Because most rivers are transboundary, the authors emphasize the particular need for using the river catchment as the key ecological/management unit, rather than political boundaries. Like North America, the diversity of European rivers is impressive, with environments ranging from the Scandinavian-Russian Arctic to mesic regions of middle Europe to arid regions of the Iberian Peninsula and Mediterranean coast. On the other hand, with a lower biodiversity of aquatic fauna in Europe, the authors’ descriptions of river-specific biodiversity, and threatened, nonnative, and extinct species serve to highlight the pressing need for conservation. Human influence on European river systems appears to have occurred earlier than in North America, with the possible exception of southern Mexico. The first alterations to European rivers were probably deforestation of floodplains, wetland drainage, and early agriculture, at least 6000 years ago. More dramatic alterations of channels, small dams, and levee-building probably did not occur in any significant way until 1000 years ago, and as the centuries passed, such activities became more widespread. Like North America, however, most significant engineering projects, particularly large dams, did not appear until the 20th century. As a result, few European rivers today are free-flowing with significant natural floodplains (only 30 of 165 described in this book), and many suffer from a wide variety of additional impacts. Given this long history and intensity of river degradation, Tockner and his collaborators emphasize the need for conservation of the few natural rivers and restoration of many others. Restoration of rivers degraded for more than a century creates a special challenge because reference conditions are non-existent in many regions. Furthermore, all conservation, restoration and management activities come with a price tag, and establishment of priorities is a major and potentially controversial task.
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The good news for European rivers is that the European Union recently began an important program called the Water Framework Directive (WFD) that requires a management plan for all major European rivers to achieve ‘‘good ecological status’’ by 2015. Rivers of Europe seems uniquely timed to be an invaluable resource to the WFD by providing a foundation for future management decisions. In general, however, the book will greatly appeal to any individual who is fascinated by rivers and will become a single major information source for river scientists, river managers, government agencies, recreationists, and conservationists within Europe and elsewhere. Arthur C. Benke The University of Alabama Tuscaloosa, Alabama, U.S.A.
Preface and Acknowledgements
Rivers traverse our landscapes and often are the major source of water for domestic, agricultural and industrial usage, power generation, navigation, fisheries, and recreation. Rivers also are a source of fascination and discovery for ecologists, hydrologists, geologists, geographers, and environmentalists. They house a tremendous source of aquatic biodiversity, much of which is highly threatened. Because of the vital role rivers play in the landscape and for society, they have been described as the circulatory system of the landscape. In spite of their undeniable and fundamental importance, there is no comprehensive treatment of the natural characteristics and diversity of European rivers nor of the extent to which human society has exploited them. With this book, Rivers of Europe, we tried to narrow this important information gap. In 2005, editors Art Benke and Bert Cushing published the benchmark book Rivers of North America. This book inspired us to compile a similar book on European Rivers. Enthusiastically, we agreed to the task - though being unaware of the major challenges awaiting us. It took almost three years from developing the first concept until completion of the book. Geographically, Europe extends from the Ural Mountains in the east to the Caucasian Alps in the southeast. There are over 150 transboundary rivers in Europe that form or cross borders of two or more countries. Europe has a total population of 780 million people with more than 100 spoken languages. The Rivers of Europe is the first reference book that covers all of Europe. In total, 136 authors from 20 countries contributed to the book, mirroring Europe’s cultural, geographic, and ecological diversity. Our first challenge was to collect comparable information on 165 European rivers, including catchments ranging from Iceland to the Peloponnese, and from the Atlantic coast in Portugal to the shores of the Caspian Sea. On the one hand, we were pleased with the wealth of available information, even for rivers that most people are unfamiliar such as those in Anatolia or northwest Siberia. On the other hand, we were somewhat surprised that even basic information on river basins such as catchment area, discharge, or water temperature was quite difficult to obtain in adequate quality. For example, published data on catchment area varies extremely, even for well-studied rivers such as the Rhine and Danube. Our second challenge was to focus at the catchment rather than country scale. While information on biodiversity or water use is mainly available at the country scale, management of river ecosystems must be done at the catchment scale. In addition, information quality differed between countries, which created a major challenge, especially for transboundary rivers. Therefore, there might be inconsistences between data presented in the individual chapters and those in the introductory chapter, where we analysed data from the same sources for all of Europe. In this respect, this book should stimulate the collection of comparative data for all of Europe and not just for the member states of the European Union. This kind of information is a pivotal requirement for setting priorities for conservation and restoration at the continental scale. We hope that the present book stimulates further research activities on European rivers, and that it supports the implementation of the EU-Water Framework Directive (WFD). The Directive is an extremely ambiguous legislative framework to protect and improve the quality of all water resources, including rivers, lakes, groundwater, and even transitional and coastal waters. The Directive states that “good ecological status” of all European rivers must be achieved by 2015. By reading about so many rivers during the past few years, we must acknowledge that most rivers already have been irreversibly transformed. Many rivers have been managed for centuries, thereby forming important elements in our cultural landscapes. In this respect, most rivers have been trained during the past decades leading to potentially irreversible damages. This book would not have been possible without the support of many people. First and foremost, we heartily thank the contributors of the chapters. It was an amazing pleasure to collaborate with so many enthusiastic and
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dedicated authors from all over Europe. We are especially grateful to Diego Tonolla, Eawag, who has devoted an immense amount of effort to the book. Diego Tonolla developed the European Catchment Data Base, digitized all the catchments, designed the maps, and was essential during the final preparation of the book. Rosi Siber, Eawag, has overseen the entire GIS effort, at the beginning of the project in particular. Special thanks goes to Fabian Peter, who developed the fish data base on European Rivers. Further, he summarized the available information on dragonflies, wetland birds, crayfish, and amphibians. We also thank Verena Keller, Schweizerische Vogelwarte, Sempach, for her support in collecting data on wetland birds, and Vincent Kalkman, European Invertebrate Survey - Nederland Nationaal Natuurhistorisch Museum - and Chair of the IUCN Odonata Specialist Group, for the compilation of the Odonata data. Additional support came from Sónia Ferreira, Cosmin-Ovidiu Manci, Elena Dyatlova, Milen Marinov, Otakar Holusa, Milos Jovic and Vladimir Skvortsov. Jörg Freyhof provided helpful information on the European freshwater fish fauna. Special thanks go to illustrator Lydia Zweifel for drawing all graphs for the book. Jan Landert, Christoph Gasser, and Barbara Köfler-Tockner assisted in the preparation of the book at various stages. We thank the many people that contributed photos that greatly enhanced the asthetics of the book. They are acknowledged in the individual chapters. The editors thank the many colleagues and authors that encouraged us and provided feedback over the past three years. We are very grateful to Andy Richford, Stephen Pegg, Emily McCloskey, and Mara Vos-Sarmiento of Elsevier/Academic Press for guiding us through the planning and execution of the project. Finally, we thank our home institutions Eawag, the Swiss Federal Institute of Aquatic Sciences and Technology, and IGB, the LeibnizInstitute of Freshwater Ecology and Inland Fisheries, for logistic and financial support. Without this support, it would have been impossible to establish the European Catchment Data Base, to design the GIS maps, and to redraw all graphs. We thank DIVERSITAS for endorsing the work presented. This book contributes to the implementation of the Science Plan of the DIVERSITAS freshwater BIODIVERSITY Cross-cutting Network. Berlin and Dübendorf, October 2008. Klement Tockner, Christopher T. Robinson, Urs Uehlinger
Chapter 1
Introduction to European Rivers Klement Tockner
Urs Uehlinger
Christopher T. Robinson
Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), M€ uggelseedamm 310, Berlin, Germany Institute of Biology, Freie Universit€ at, Berlin, Germany
Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland
Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland
Diego Tonolla
Rosi Siber
Fabian D. Peter
Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland
Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland
Swiss Federal Institute of Aquatic Science and Technology (Eawag), Box 611, 8600 Duebendorf, Switzerland
1.1. 1.2. 1.3. 1.4. 1.5. 1.6. 1.7. 1.8. 1.9. 1.10. 1.11. 1.12.
1.13. 1.14.
Introduction Biogeographic Setting Cultural and Socio-economic Setting Hydrologic and Human Legacies Early and Recent Human Impact Temperature and Precipitation Water Availability and Runoff Riverine Floodplains River Deltas Water Quality Freshwater Biodiversity Environmental Pressures on Biodiversity 1.12.1. Fragmentation 1.12.2. Water Stress 1.12.3. Land Use Change 1.12.4. Non-native Fish Species The European Water Framework Directive Knowledge Gaps Acknowledgements References
1.1. INTRODUCTION Rivers recognize no political boundaries. This is particularly true for Europe, which has over 150 transboundary rivers (Whitton 1984). For example, the Danube is the 29th longest river globally, and it drains parts of 19 countries and 10 ecoregions. Further, 8 of the 10 largest catchments in Europe (Figures 1.1 and 1.2, Table 1.1) are in the eastern plains of Russia and the Ukraine and information on their present status Rivers of Europe Copyright Ó 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.
is highly limited. Europe also has a long history in river training with most rivers being severely fragmented, channelized, and polluted (Petts et al. 1989; Kristensen & Hansen 1994; Tockner & Stanford 2002; UNEP 2004; Nilsson et al. 2005). Recently, the European Union launched an ambitious program called the Water Framework Directive (WFD) that requires a catchment management plan for all major European rivers for achieving ‘good ecological status’ by 2015. In this introductory chapter, we provide a comprehensive overview of all major European catchments included in the book (Figure 1.2), starting with the biogeographic setting, with an emphasis on physiography, hydrology, ecology/biodiversity, and human impacts.
1.2. BIOGEOGRAPHIC SETTING Europe forms the northwestern physiographic constituent of the larger landmass known as Eurasia. Europe covers an area of 11.2 million km2 that includes the European part of Russia, parts of Kazakhstan (Ural River Basin), the Caucasus, Armenia, Cyprus, and Turkey (Figures 1.1 and 1.2). Armenia and Cyprus are considered as transcontinental countries; and Turkey is included because of political and cultural reasons. The average altitude of Europe is 300 m asl compared to 600 m asl for North America and 1000 m asl for Asia. Only 7% of Europe is above 1000 m asl. Europe has an extensive and deeply penetrating network of water bodies. Its 117 000 km convoluted coastline facilitated easy access to the interior, and it is this feature that contributed to the rapid development of its southern shores along the Mediterranean Sea (Stanners & Bourdeau 1995; Butlin & Dodgson 1998; Hughes 2001). 1
2
PART | I Rivers of Europe
FIGURE 1.1 Topographic map of Europe and location of geographic regions covered in the book. Data sources: see Appendix.
Europe is highly diverse, both biogeographically and ecologically. The European Environmental Agency has identified 11 biogeographical regions that are considered as useful geographical reference units for describing habitat types and species that live under similar conditions (Figure 1.3A) (http://reports.eea.europa.eu/ report_2002_0524_154909/en). The biogeographic regions dataset contains the official delineations used in the Habitats Directive and for the EMERALD Network set up under the Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention). In addition, Europe has been divided into 71 ecological distinct areas, based on climatic, topographic, and geobotanical data, together with the judgement of a large team of experts from several European nature-related institutions (Figure 1.3B). Ecological regions are areas with relatively homogeneous ecological conditions, within which comparisons and assessments of different expressions of biodiversity are meaningful (e.g. rivers and lakes, see also Illies 1978).
1.3. CULTURAL AND SOCIO-ECONOMIC SETTING There are distinct cultural, demographic, socio-economic, and political gradients across Europe (Bacci 1998; Hughes 2001). Today’s human population is 780 million with an average population density of 69 people/km2. At the catchment scale, the population density ranges from <2 people/km2 (e.g. Pechora Basin in Russia) to 1257 people/km2 (Mersey basin in Great Britain). The annual Gross Domestic Product (GDP; US$/person) ranges over two-orders-of-magnitude, from 600$ (Dniester Basin in Moldova) to 65 000$ (Aare Basin in Switzerland, a subbasin of the Rhine). Human life expectancy ranges from 61 (Ural Basin) to 80 years (river basins in Iceland, Italy, Spain, Sweden, and Switzerland). More than 100 languages are spoken across Europe, with the greatest number (27 languages) spoken in the Caucasus region.
Chapter | 1 Introduction to European Rivers
FIGURE 1.2 Spatial distribution of European catchments in 17 different geographic regions (different colors), including subcatchments of the Volga, Danube, Rhine, and Rhone Basins. Data sources: see Appendix.
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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
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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
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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 )
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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).
29
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).
30
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).
31
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
46
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
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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).
53
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.
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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
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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
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60
FIGURE 3.1 Digital elevation model (upper panel) and drainage network (lower panel) of the Danube River Basin.
PART | I Rivers of Europe
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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
78
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
79
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).
82
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.
93
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
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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
