Rivers of the Balkans

Klement Tockner, Urs Uehlinger, and Christopher T. Robinson

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Rivers of EuropeFirst Edition

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Cover ImageThe High Rhine River at the outlet of Lake Constance, near the small town of Stein am Rhein. Lake dwellers and, subsequently, the Romans settled along the southern shore of the river at Eschenz. Today, the island ‘Werd’ is home to a group of Franciscan friars. At this location, the waters of the Rhine have already travelled for 230 km and will fl ow for another 1000 km before entering the North Sea. (Photo: Dieter Füllemann, Eschenz, Switzerland, with kind permission).

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List of Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

For w rd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv Arthur C. Benke

Preface and Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii Klement Tockner, Urs Uehlinger, and Christopher T. Robinson

Chapter 1 Introduction to European Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Klement Tockner, Urs Uehlinger, Christopher T. Robinson, Diego Tonolla, Rosi Siber, and

Fabian D. Peter

Chapter 2 Volga River Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Alexander S. Litvinov, Natalya M. Mineeva, Vladimir G. Papchenkov, Ludmila G. Korneva,

Valentina I. Lazareva, Grigory Kh. Shcherbina, Yuri V. Gerasimov, Svetlana A. Dvinskikh, Victor M. Noskov, Alexander B. Kitaev, Margarita S. Alexevnina, Elena V. Presnova, Elena B. Seletkova, Euvgeny A. Zinovíev, Mikhail A. Baklanov, Alexander G. Okhapkin, and Galina V. Shurganova

Chapter 3 The Danube River Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Nike Sommerwerk, Thomas Hein, Martin Schneider-Jakoby, Christian Baumgartner, Ana Ostojic,

Momir Paunovic, Jürg Bloesch, Rosi Siber, and Klement Tockner

Chapter 4 The Iberian Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Sergi Sabater, Maria Joao Feio, Manuel A.S. Graça, Isabel Muñoz, and Anna M. Romaní

Chapter 5 Continental Atlantic Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 Jean-Pierre Descy

Chapter 6 The Rhine River Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 Urs Uehlinger, Karl M. Wantzen, Rob S.E.W. Leuven, and Hartmut Arndt

Chapter 7 The Rhône River Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 Jean-Michel Olivier, Georges Carrel, Nicolas Lamouroux, Marie-José Dole-Olivier, Florian

Malard, Jean-Paul Bravard, and Claude Amoros

Chapter 8 The Fennoscandian Shield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 B. Malmqvist, T. Muotka, C. Nilsson, and H. Timm

Contents

e o

Chapter 9 Arctic Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 John E. Brittain, Gísli M. Gíslason, Vasily I. Ponomarev, Jim Bogen, Sturla Brørs, Arne J. Jensen,

Ludmila G. Khokhlova, Sergej K. Kochanov, Alexander V. Kokovkin, Kjetil Melvold, Jón S. Ólafsson, Lars-Evan Pettersson, and Angelina S. Stenina

Chapter 10 British and Irish Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 Chris Soulsby, Doerthe Tetzlaff, Chris N. Gibbins, and Iain A. Malcolm

Chapter 11 Rivers of the Balkans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 Nikolaos Th. Skoulikidis, Alcibiades N. Economou, Konstantinos C. Gritzalis and Stamatis

Zogaris

Chapter 12 The Italian Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 B. Gumiero, B. Maiolini, N. Surian, M. Rinaldi, B. Boz, and F. Moroni

Chapter 13 Western Steppic Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497 A.N. Sukhodolov, N.S. Loboda, V.M. Katolikov, N.A. Arnaut, V.V. Bekh, M.A. Usatii, L.A. Kudersky,

and B.G. Skakalsky

Chapter 14 Rivers of the Central European Highlands and Plains . . . . . . . . . . . . . . . . . . . . . 525 Martin Pusch, Hans E. Andersen, Jürgen Bäthe, Horst Behrendt, Helmut Fischer, Nikolai

Friberg, Aleksandra Gancarczyk, Carl. C. Hoffmann, Justyna Hachot, Brian Kronvang, Franciszek Nowacki, Morten L. Pedersen, Leonard Sandin, Franz Schöll, Matthias Scholten, Sonja Stendera, Lars M. Svendsen, Ewa Wnuk-Gławdel, and Christian Wolter

Chapter 15 Rivers of the Boreal Uplands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 Jan Henning L’Abée-Lund, Jon Arne Eie, Per Einar Faugli, Svein Haugland, Nils Arne Hvidsten,

Arne J. Jensen, Kjetil Melvold, Vegard Pettersen, Lars-Evan Petterson, and Svein Jakob Saltveit

Chapter 16 Baltic and Eastern Continental Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 607 Henn Timm, Małgorzata Łapinska, Maciej Zalewski, Vaida Olšauskyte, Ricardas Skorupskas,

Agrita Briede, Ivars Druvietis, Gertrúde Gavrilova, Elga Parele, Gunta Springe, Ritma Gaumiga, Marina M. Mel’nik, and Jurij V.Aleksandrov

Chapter 17 Rivers of Turkey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643 Nuray (Emir) Akbulut, Serdar Bayarı, Aydın Akbulut, and Yalçın Sahin

Chapter 18 Ural River Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 673 Tatjana V. Eremkina, Margarita I. Yarushina, and Klement Tockner

Chapter 19 European Rivers: A Personal Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 685 Alan G. Hildrew, and Bernhard Statzner

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 699

Chapter 11

Rivers of the Balkans

Nikolaos Th. SkoulikidisHellenic Centre for Marine Research,

Institute of Inland Waters 46.7km Athens-

Sounion Avenue, 190 13 Anavissos, Greece

Alcibiades N. EconomouHellenic Centre for Marine Research,



Konstantinos C. GritzalisHellenic Centre for Marine Research,



Stamatis ZogarisHellenic Centre for Marine Research,



11.1. Introduction

11.2. Historical Perspective

11.3. Major Rivers and Tributaries

11.4. Biogeographic Setting

11.4.1. General Aspects

11.4.2. Palaeogeography

11.5. Physiography, Climate and Land Use

11.5.1. Geomorphology, Landform, Geology

11.5.2. Climate

11.5.3. Land Use Patterns and Human

Pressures

11.6. Hydrology and Biogeochemistry

11.6.1. Hydrology and Temperature

11.6.2. Biogeochemistry

11.6.3. General Characterization

11.6.4. Sediment Loads (Long-Term Trends)

11.6.5. Nutrients and Pollution

11.7. Riparian and Aquatic Biodiversity

11.7.1. Riparian Vegetation

11.7.2. Lowland Riparian Woods

11.7.3. Deltaic Communities

11.7.4. Ichthyofauna

11.7.5. Macroinvertebrates

11.7.6. Reptiles and Amphibians

11.7.7. Birds

11.7.8. Mammals

11.8. Management and Conservation

11.8.1. Economic Importance

11.8.2. Conservation and Restoration

11.8.3. Restoration Activities and Potential

11.8.4. Reference Conditions

11.8.5. EU Water Framework Directive

11.9. Conclusion and Perspective

Acknowledgements

Reference

11.1. INTRODUCTION

The Balkan Peninsula, or Balkans, is the historic and geo-graphic name of southeastern Europe. The name is derivedfrom the Balkan mountain range, the ancient Haemos, whichdivides Bulgaria and runs through eastern Serbia (in Turkish,Balkan means ‘a chain of wooded Mts’). The Balkans laysouth of the rivers Save, Drava andDanube and is surroundedby the Adriatic and Ionian Seas in the west, the Mediterra-nean Sea in the south and the Aegean, Marmara and BlackSeas in the east. The identity of the Balkans owes as much toits complex and oftenviolent common history as well as to itsspectacular mountainous topography.

11.2. HISTORICAL PERSPECTIVE

Rivers and river gods played an important role in Greekmythology. Potamoi (Rivers) were thought to be offspringsof the Titan Okeanos (Ocean), son of Gaea (Earth) andOuranos (Sky), and Tethys. The Balkan mountain rangesprovide no barriers against human invasions from the northor east. Hence, the region has faced a long history of wars,rebellions, invasions and clashes between tribes, nationsand empires – from prehistoric times to the recent Yugoslavwar. The Balkan region has been inhabited permanentlysince the Middle Palaeolithic (Darlas 1995). It was the firstarea in Europe where farming cultures and livestock raisingwere established during the Neolithic era (Bailey 2000). Inpre-classical and classical antiquity, the region was home toGreeks, Illyrians, Paeonians, Thracians and other ancienttribes. Later, the Roman Empire conquered most of theregion but significant parts remained under classical Greekinfluence. At the end of the Roman Empire, migrating Slavsentered the Balkans. During the middle Ages, the Balkansbecame a battlefield between the Byzantine, Bulgarianand Serbian Empires. By the end of the 16th century, the

Ottoman Empire emerged as the dominating force in theregion. Because of frequent wars, the Balkans has remainedthe least developed area in Europe for the past 550 years.The Balkan nations started to regain independence in the19th century. After World War II, until 1989, the Balkans(except Greece) was under communist regimes. In the1990s, the region was hit by a civil war, with a death tollof�100 000 people, finally leading to independence of theformer Yugoslavian states.

11.3. MAJOR RIVERS AND TRIBUTARIES

This chapter covers 15 rivers that encompass the bio-geographical diversity of the Balkan Peninsula (Figure11.1). TheKamchia River flows into the Black Sea, all othersinto the Mediterranean; eight rivers enter the Aegean Sea(Evros, Nestos, Strymon, Axios, Aliakmon, Pinios, Sperch-ios and Evrotas), three the Adriatic Sea (Neretva, Drin andAoos) and three the Ionian Sea (Arachthos, Acheloos andAlfeios). Six river basins are transboundary. The Drin (Drim)drains parts of Albania, Serbia, Montenegro, former Yugo-slav Republic of Macedonia (FYR Macedonia) and Greece.For its relatively small size, it is among the most internation-al rivers worldwide. The Neretva flows through Bosnia andHerzegovina and Croatia; the Evros (Maritsa, Meric) basin isshared among Bulgaria, Greece and Turkey; the Strymon(Struma) and the Nestos (Mesta) are shared by Bulgariaand Greece, the Axios (Vardar) enters Greece from FYRMacedonia, while the Aoos (Vjose) flows from Greece to-wards Albania. The Kamchia is entirely located in Bulgaria,while the Aliakmon, Pinios, Sperchios, Arachthos, Ache-loos, Alfeios and Evrotas are entirely in Greece. The catch-ment area of all 15 rivers totals 182 637 km2. Six river basins(Evros, Axios, Drin, Neretva, Strymon and Pinios) areconsidered as very large (>10 000 km2) and 9 as large(1000–10 000 km2). The Nestos, Drin, Neretva, Aoos andArachthos drain mountainous catchments with meanaltitudes>800 m asl, the remaining rivers drain mid-altitude(mean altitude: 300–800 m asl) catchments, with theKamchia, Evros and Pinios having downstream lowlandriver sections. Most Balkan rivers form deltaic plains; someof them are wetlands of international importance. Table 11.1summarizes the main physiographic characteristics of allcatchments (Photos 11.1–11.10).

TheNeretva rises in Bosnia and Herzegovina (97.5% ofits basin) and enters southern Croatia forming a large delta.The Basin contains the largest karstic river in the DinaricMts and is hydrologically connected with the TrebisnjicaRiver.

The Drin, the largest Albanian river, runs through amountainous area towards the coast. It provides the thirdgreatest river discharge in the European Mediterranean.The river has two main branches: the White Drin drainsSerbia and Montenegro and the Black Drin originatesfrom Lake Pespa (transboundary lake between FYR

Macedonia, Albania and Greece) and Lake Ohrid (trans-boundary lake between FYR Macedonia and Albania).Before it enters the Adriatic Sea, the Buna River joinsthe Drin. The Buna drains Lake Shkodra (Shkadar),the largest Balkan lake (shared between Albania andMontenegro).

The Aoos flows through an almost pristine mountainouslandscape in NWGreece before it enters Albania (64% of thetotal basin). It forms a large delta. Its largest tributary is thetransboundary Drino with a catchment area of 1320 km2

(80% located in Albania).The Kamchia runs through a wide basin in eastern

Bulgaria and empties into the Black Sea. The river has twomain branches, the Golyama–Kamchia in the north and theLuda–Kamchia in the south.

The Evros is the largest river basin in the Balkans. It isshared between Bulgaria (66.4%), Turkey (27.2%) andGreece (6.4%). It flows through Bulgaria, then forms theborderline with Greece and Turkey and finally creates a largedelta in the Aegean Sea. The main tributaries are the Tundja(7980 km2, 350 km) in Bulgaria, the Arda (5200 km2,240 km) in Bulgaria with a small part in to Greece, and theErgene (10 200 km2, 280 km) in Thracian Turkey.

The Nestos is a highland river (mean altitude:1006 m asl). It flows through Bulgaria (60% of the basinarea) and Greece and enters the Aegean Sea forming anextensive delta. The main tributary is Dospatis (Dospatska)(236 km2) that emerges in Bulgaria and joins the Nestos inGreece.

The Strymon basin is mainly located in Bulgaria (50%)and in Greece (37%), with tributaries draining small partsof FYR Macedonia (9%) and Serbia (4%). After enteringGreece, it passes through the semi-natural Kerkini Lakeand discharges into the Aegean Sea (Strymonikos Gulf).Major tributaries along the Bulgarian section are the Stru-meshnitsa (1892 km2) and the Treklyanska (515 km2),while the Aggitis (2234 km2) is the main tributary inGreece.

The Axios, located in the central Balkan Peninsula,drains the second largest catchment in the Balkans. The riverdrains 83% of FYR Macedonia and small parts of Bulgaria,Serbia and Greece before it enters the Aegean Sea (Thermai-kos Gulf). Major tributaries are the Crna (5890 km2) and theBrejalinica (4307 km2). The river is hydrologically con-nected to Lake Doirani (Dojran), shared between Greeceand FYR Macedonia.

The Aliakmon, the longest river in Greece, receivesoverflow waters from Lake Kastoria. Its main upstreamtributary is the Venetikos (821 km2). Downstream, thetributaries Almopeos and Edesseos, connected through along irrigation canal (named T66) (2100 km2), join the riverthat finally discharges into the Thermaikos Gulf forming ajoint delta with Axios.

The Pinios in central Greece drains the seemingly vastThessaly plain and flows into the Thermaikos Gulf. Severalpermanent tributaries contribute to its runoff of which

Titarissios (1750 km2), Onochonos (1575 km2) and Enipeas(1075 km2) are the largest.

The Sperchios basin, south of the Pinios catchment, is thesmallest of the examined rivers. It flows to the Maliakos Gulf(Aegean Sea) where it creates a rapidly expanding delta.

TheArachthos drains a small mountainous basin locatedin western Greece. It outflows to the Amvrakikos Gulf(Ionian Sea) creating a large delta with extensive lagoons.

The Acheloos, also situated in western Greece, has thehighest runoff among all Greek rivers. The upstream andmiddle parts of the river receive numerous permanenttributaries with Megdovas (Tavropos) being the largest(830 km2). Close to its delta, four natural lakes (Tricho-nis, the largest and deepest Greek lake, Lysimachia,Ozeros and Amvrakia) are formed that maintain a presentor past connection with Acheloos. The river empties into

FIGURE 11.1 Digital elevation model (upper panel) and drainage network (lower panel) of Rivers of the Balkans.

TABLE 11.1 General characterization of the Rivers of the Balkans

Kamchia Neretva Drin Evros Nestos Strymon Axios AliakmonPinios Sperchios Aoos Arachthos Acheloos Alfeios Evrotas

Mean catchment elevation (m) 311 848 868 400 1006 715 747 771 431 685 849 807 744 690 654Catchment area (km2) 5338 13 311 20 585 53 078 6265 17 087 24 604 8880 10 743 1493 6813 1907 6478 3637 2418River length 245 255 285 550 246 410 380 310 257 82 260 105 255 112 90Discharge (km3/year) 0.607 11.9 11.4 (21.4a) �7.0 2.076 4.31 3.62 2.7 2.55 0.703 5.55 2.08 4.38 2.1 0.76Specific discharge (L/s km2) 5.2 28.3 17.5 (26.3a) !4.2 10.5 8.0 6.7b 9.6 7.5 14.9 25.8 34.6 21.4 18.3 10.0Mean annual precipitation (cm) 57.7 117.7 105.3 62.9 64.8 60.8 62.9 67.1 62.4 64.4 100.2 91.2 80.8 76.2 73.3Mean air temperature (�C) 11.1 9.2 8.9 11.2 9.6 10.1 9.9 10.6 13.3 13.2 11.8 12.9 13.5 13.9 14.0Number of ecological regions 2 2 4 4 3 3 4 3 2 2 2 3Dominant (�25%)ecological regions

9 27; 39 9; 53 9; 58 9; 58 1; 9 9 53 1 1; 53 39; 53 39; 53 1; 53 1 1

Land use (% of catchment)Urban 4.5 0.7 0.7 2.7 1.2 2.4 1.4 1.1 2.1 1.3 1.0 0.6 0.7 0.8 0.7Arable 40.6 16.3 21.7 53.4 18.2 34.5 34.0 39.3 51.1 31.4 16.0 19.3 22.2 38.6 34.6Pasture 3.4 8.3 4.3 5.1 0.8 2.0 8.1 0.4 1.6 0.2 0.5 0.0 0.0 0.9 0.0Forest 44.7 29.2 36.6 26.7 56.4 35.8 32.1 30.4 16.9 32.4 35.7 24.7 26.3 17.2 15.8Natural grassland 5.8 40.2 26.2 10.1 20.4 22.8 23.4 25.4 32.8 33.7 39.3 30.4 43.0 39.9 48.0Sparse vegetation 0.0 3.0 5.2 0.2 1.5 1.4 0.3 1.6 1.2 0.8 6.9 3.5 3.3 2.1 0.8Wetland 0.0 0.4 0.8 0.7 0.5 0.3 0.2 0.4 0.1 0.1 0.1 0.2 0.3 0.0 0.0Freshwater bodies 1.0 0.7 4.5 1.1 1.0 0.8 0.5 1.4 0.2 0.1 0.5 1.3 4.2 0.5 0.1

Protected area (% of catchment) 0.2 0.9 5.0 1.1c 5.7 7.3 1.8 13.5 13.0 19.5 15.6 21.7 17.2 7.4 18.9

Water stress (1–3)1995 2.7 1.1 1.1 2.8 2.3 2.8 2.9 2.7 2.9 2.1 1.7 1.8 2.2 1.8 1.02070 2.8 1.2 1.2 2.9 2.3 2.9 2.9 2.7 2.9 2.1 1.7 1.9 2.2 1.8 1.0

Fragmentation (1–3) 3 3 3 2 3 3 2 3 2 1 2 3Number of large dams (>15 m) 3 5 5 21 4c 4c 17 3 1 0 1 2Native fish species 38 31 56 32 21 36 36 24 29 11 17 13 22 10 5Nonnative fish species 3 12 16 7 8 7 5 9 1 4 1 3 15 8 1Large cities (>100 000) 0 1 3 3 0 0 1 0 1 0 0 0Human populationdensity (people/km2)

48 38 98 69 33 57 83 36 54 28 44 28 27 26 30

Annual gross domesticproduct ($ per person)

1800 2014 2562 2922 6710 6636 3229 13 227 12 350 15 096 4407 9265 11 978 10 836 11 390

Land use data are approximate values.a With Buna.b �Natural.c At least.

For data sources and detailed explanation see Chapter 1.

the Ionian Sea forming a delta associated with extensivelagoons.

The Alfeios, with its main tributary Ladon (750 km2),drains much of the western Peloponnese.

The Evrotas is the southernmost basin of the Balkanmainland and empties into the Laconikos Gulf.

11.4. BIOGEOGRAPHIC SETTING

11.4.1. General Aspects

The Balkan Peninsula is situated at the biogeographicalcrossroad between continental Europe, western Asia andthe Mediterranean and Black Seas. It is characterized by a

PHOTO 11.1 The Aliakmon’s IlarionGorge, near Kozani, Northern Greece;one of the largest deep canyons in Greecedestined to be flooded by new hydropow-er dam developments (S. Zogaris).

PHOTO 11.2 Evrotas upstream dry-ing out (N. Skoulikidis).

rich aquatic fauna and flora with a high proportion of en-demic species. High biodiversity is a consequence of theregion’s geologic and palaeoclimatic history as well as thegeophysical variety of inland water bodies (Griffiths et al.2004). During the Pleistocene, glaciers were restricted tomountain summits. The lowland areas provided refugia forthe continental freshwater fauna and flora. Despite their

rather small size, the Balkan rivers and streams host highlydiverse freshwater communities. The high degree of ende-mism, compared to the rest of Europe, is perhaps the mostremarkable feature of the Balkans. For example Greece con-tains the largest number of freshwater fish species and thehighest proportion of endemic fish in Europe (Crivelli et al.1995).

PHOTO 11.3 One of westernGreece’s most extensive braided riverreaches on the mid section of the Ache-loos river (S. Zogaris).

PHOTO 11.4 The Aoos river near theGreek-Albanian border naturally con-strained in conglomerate bedrock (S.Zogairs).

The relative isolation of river basins through geologicalhistory has forged distinctive biogeographic boundaries anda complex historical sequence of biotic isolation and frag-mentation (e.g. interruption of dispersal routes). During theformation of the mid-Aegean trench (�9 Ma BP), the pen-insula became separated from Asia Minor by the contiguousAegean Sea (Dermitzakis & Papanikolaou 1981). One of the

most distinctive long-standing biogeographical barriers isthe Dinarides–Hellenides mountain chain that separates thewestern and eastern biotic assemblages. Phylogenetic stud-ies confirm a west–east split of the Balkan’s aquatic andterrestrial biota. Even widespread species, such as the PondTurtle (Emys orbicularis) and common reptiles, are split intowestern and eastern phylogroups (Schmitt 2007).

PHOTO 11.5 The Arachthos river atTzari Bridge upstream of the PournariReservoir (S. Zogaris).

PHOTO 11.6 The Evrotas river,flanked by native white poplars, rem-nants of extensive riparian forests (S.Zogaris).

The isolation of the western Balkan river basins sinceMiocene times has favoured a rich endemic aquatic fauna(Bianco 1986; Gasc 1997). Further, there are marked latitu-dinal gradients in species composition and richness. Speciesrichness increases from south to north while the proportionof endemic species increases from north to south. The catch-ments south of the Aoos River are depauperate compared tothe more northern basins. However, almost all primary fresh-water fishes as well as several amphibians (e.g. Epirus frogRana epiroticus) and reptiles are endemic to this area(Arnold & Ovenden 2002).

The eastern part of the Balkan Peninsula is richer inaquatic biota, although the proportion of endemic speciesis lower. This area is influenced by adjacent biogeographicregions, especially the Lower Danube-Black Sea region. Inaddition, climatic factors contribute to the generation ofbiogeographic differences. The eastern Balkans exhibit acontinental and dry climate with harsh and cold winters.Some parts are biologically ‘isolated’ through local xericclimate conditions caused by rain shadow effects. SoutheastGreece, a rather small part of the peninsula with low

precipitation and dry summers, contains small and oftenintermittent rivers. They harbour fish and benthic inverte-brate communities rich in endemic species (Economidis &Banarescu 1991).

An important geological feature of the Balkans, withstrong biogeographic implications, is the high proportion ofkarstic subterranean rivers, especially in the western part.They contain remarkable subterranean communities. Thisarea is a ‘hot spot’ of hypogean biodiversity with unique lifeforms such as the Olm Proteus anguinusin in the Neretva.The Aggitis River tributary at the Strymon emerges from avast system of underground caverns that provides habitatfor the Thracian barbel Barbus cyclolepis and the Stonecrayfish Austropotamobium torrentium (Koutrakis et al.2003, 2007).

A definitive biogeographic characterization of the Bal-kans remains difficult because underlying biogeographicpatterns are interrupted by several idiosyncrasies and inher-ent river basin attributes (numerous lakes, peninsulareffects). There exist major discrepancies among researcherson how to define and delineate biogeographic regions for

PHOTO 11.7 The Mesochora Dam (not yet filled) in theUpper Acheloos river; one of the largest and most contro-versial river diversion projects in Mediterranean Europe (S.Zogairs).

terrestrial, aquatic, or semi-aquatic biota in this region (Illies1978; Banarescu 2004). Since aquatic biodiversity has notbeen well inventoried in many parts of the Balkans, satisfac-tory base-line knowledge of species distributions and thevalidity of the systematic taxonomy are far from complete.

11.4.2. Palaeogeography

The Balkan Peninsula has developed over the course ofseveral orogenic cycles from the Late Palaeozoic to thepresent following the collision between the Eurasian andAfrican tectonic plates. The current orographic regime ofthe Balkans is the result of the Alpine orogenesis duringthe past 250 million years (from late Triassic to the Quater-nary). The Alpine orogenesis began with the rifting of Pan-gea, the development of tectonic rift valleys, and the advanceof the Tethys Sea between Eurasia and Africa–Arabia.Wide-spread carbonate marine sedimentation (limestones, dolo-mites and marls) continued through the Triassic andCretaceous. During the late Jurassic and early Cretaceous

significant orogenic activities caused the break up of thecontinental crust within the Tethys Sea, where ophiolites,situated today along two parallel belts, have been emplaced.A Cretaceous to Eocene compressive deformation that mi-grated from the east to the west of the Balkans was followedby the generation of deep rift valleys, which were filled up byflysch andmolasse (Eocene–Miocene, younging from east towest).

During the late Palaeocene – late Eocene (50–35 MaBP),large parts of the northern and eastern Balkans had alreadyemerged and in the mid-late Eocene the Kamchia foredeepdeveloped (Georgiev 2001). By the end of the Eocene thewestern part of the Tethys Sea was reduced to the Mediter-ranean Sea. During the Eocene–Oligocene transition(�32 Ma BP) the Paratethys was formed to the north. Thegradual uplift of the Balkan and the Dinarides–HellenidesMts separated the Balkan basins from the central Europeanand the eastern and western Balkan basins. In the lowerMiocene (�23 Ma BP) the Pindic and Pelagonian Cordil-leras, together with the Rhodopes, created large landmassesinterrupted by seas. Deep sea carbonate and flysch

PHOTO 11.8 The Yeropotamos tributary of the Axios-Vardar, on Mount Voras, Northern Greece (S. Zogaris).

sedimentation continued westward and shallow marinemolassic deposits laid down between the mountain ranges.About 18 Ma BP, significant tectonic movements upliftedthe whole Balkan region and huge napes were emplaced inmost Alpine chains. By that time, the Balkans, the AegeanSea and Asia Minor formed a large continuous landmass(Dermitzakis & Papanikolaou 1981).

During the late Tortoninan (c. 8 Ma BP), widespreadextensional tectonics caused intense fracturing of the centralcontinental part, the invasion of the sea and the connection ofthe Mediterranean with the Black and Caspian Seas, bothremnants of the Parathethys. In the mid-late Miocene, theinitial rift structures of most Balkan rivers, for example theStrymon, Nestos, Axios, Neretva, Aliakmon and Acheloos,were formed along large faults, together with the rifts oflakes Ohrid, Prespa and Doirani (Tzankov et al. 1996; Kar-istineos & Ioakim 1989; Med�zida et al. 2006; Hinsbergen2004; Lykoudi & Angelaki 2004). In the late Miocene, thelower part of the Strymon basin alternated between freshwa-ter, lacustrine and marine conditions and was linked withNestos through the Serres and Drama basins (Zagorchev

et al. 2002). At the end of the Miocene (Messinian,�5.5 Ma BP), the Mediterranean Sea closed and almostdried, large volumes of evaporites precipitated in a seriesof vast basins (‘Messinian Salinity Crisis’) and then it wasrefilled with freshwaters from the Paratethys. This event mayhave facilitated the dispersal of freshwater organisms arounda Mediterranean circum (Bianco 1990).

During the Pliocene (�5–2 Ma BP), the majority of theBalkan rivers started a rejuvenating phase forming wide anddeep mother valleys, and large amounts of fluvial sedimentswere deposited (Psilovikos & Ioannou 1993). At this time,the palaeo-Striama river (Evros tributary) joined the palaeo-Tundja river (Tzankov et al. 1996). At the end of the Plio-cene, rapid climate changes caused the disappearance ofsavannas and associated mammals and the development ofsteppic floras (Koufos et al. 2005). In the late Pliocene–Pleistocene, extensional dynamics formed the AmvrakikosGulf, which was connected with Sperchios graben and theGulf of Evia (Hinsbergen 2004), as well as the Alfeios andEvrotas basins (Hinsbergen et al. 2005), and the presentday contours of the Balkan area were shaped. At the

PHOTO 11.9 One of the largest lowland Oriental Planeriparian woodlands in southern Greece clothes parts of themid Evrotas river, in this summer-intermittent reach south ofSparta (S. Zogaris).

Plio-Quaternary boundary, a major marine transgressionconnected the Mediterranean with the Black Sea, the Cas-pian Sea and Lake Aral (Paluska & Degens 1978).

The Quaternary period was marked by alternating large-scale glaciations interfered by short warm intervals. In thePleistocene, the Axios found its way to the sea, and thusother related palaeo-lakes were drained. Today, only LakesOhrid, Prespa and Doirani remain as remnants of this exten-sive system of lakes (Dumurdzanov et al. 2004). At 1.5 MaBP, the palaeo-Evros, which emptied in the Marmara Seathrough the Ergene River, was diverted to the AegeanSea due to the uplift of the northern margin of MarmaraSea (Okay & Okay 2002). The Acheloos opened a valleythrough the Agrinio Basin, formerly filled by a large lake,remnants of which are four contemporary lakes, and emptiedinto the sea (Psilovikos et al. 1995). The same situation facedPinios, formerly a Pleistocene lake, finding its way to the seain the Holocene when the Tempi Gorge was opened (Leiva-ditis 1991). During the moist and cool conditions in theUpper Pleistocene–Holocene (130 000–18 000 years BP),glaciers covered the highest mountains, and rivers faced asecond stage of rejuvenation opening steep and incised val-leys (Psilovikos & Ioannou 1993). The rivers shortened,alternating between meandering and braided styles, andpropagated deltas, depending on glacial/interglacial cycles.

At the last glacial maximum (�21 500 years BP), whenthe sea level was �120 m lower than today, extensive shelfareas were exposed at the northern Aegean, the Adriatic andparts of the Ionian Sea. As a result, river confluences enableddispersion and faunal exchanges. The Marmara Sea and partof the Amvrakikos Gulf were freshwater lakes. TheArachthos River and its tributary Louros (which today is a

separate river) drained across the Amvrakikos Gulf, exhib-ited a braided style, and formed a delta in the Ionian Sea(Piper et al. 1988). The Thermaikos Gulf was a large alluvialplain drained by the extensions of Aliakmon and Pinios, thentributaries of the Axios palaeo-river (Lykousis et al. 2005).The Nestos and Strymon Rivers formed a joined delta in theGulf of Kavala (Perissoratis & Conispoliatis 2003). With theretreat of the ice-sheets 18 000 BP, the Black Sea lacustrinesystem drained into the Mediterranean (Economidis &Banarescu 1991). Ancient flood myths may be based onthe rising Mediterranean that suddenly broke through theBosporus inundating the farmlands of the Black Sea about5500 years BP. At that time, the sea level stabilized, whileclimate and tectonic movements, along with sediment depo-sition and deltaic formation, controlled the present shape ofcoastal areas.

11.5. PHYSIOGRAPHY, CLIMATE AND LANDUSE

11.5.1. Geomorphology, Landform, Geology

The Balkan Peninsula is a rough Alpidic orogen of the Med-iterranean type, with large thrust sheets, ophiolites, repeatedevents of metamorphism and related granitic intrusions, andsedimentation of thick carbonate, flysch and molasse depos-its. With the exception of the Thracian plateau, the Balkansare a mountainous region geotectonically divided in Internaland External Balkanides. The External Balkanides extendalong the Adriatic and Ionian coasts and are bound to the eastby the NNW–SSE running Dinarides–Hellenides mountain

PHOTO 11.10 Kalaritikos, themain Arachthos River tributary(N. Skoulikidis).

range, the backbone of the western Balkans. They weredominated by the Alpine orogenesis and reveal a rathersimple geotectonic structure made up of sedimentarysequences. The Internal Balkanides east of this mountainrange were affected by even older orogenic movementsand reveal a complex geotectonic structure dominated bymetamorphic massifs of the Pre-alpine age (Carrigan et al.2003), plutonic and volcanic intrusions and ophiolite suturezones. There are two ophiolite zones; the predominant oneextends �1000 km along the Dinarides–Hellenides moun-tain range (Dinaric Mts toMount Orthrys in Greece), and thesecond one extends eastwards along the Axios basin. Twoshorter ranges climb in the ophiolite zones, running acrossFYR Macedonia and Greece, where Mt Olympos peaks at2917 m asl; the second highest point in the Peninsula. Theimpressive chain of the Rhodopes (with Mount Rila,2925 m asl) traverses the centre of the Peninsula, throwingout spurs towards the Black Sea and the Aegean. To thenorth, the 600 km long Balkan Mts, an elongation of theCarpathians, run from west to east across Bulgaria. Due toits relatively young geology, the Balkan Peninsula is char-acterized by highly fragmented hydrographic networks andis drained by many small and medium-sized mountainousrivers. Rivers run through steep, narrow mountain valleys,have flashy flow and sediment regimes, and descend abrupt-ly to the coast. However, there are a few larger low-gradientrivers crossing the Balkans along prevailing thrust belts andrelated rift valleys that form extensive flood and deltaicplains.

The Dinarides–Hellenides mountain range forms a seriesof nearly parallel ridges, plateaus and depressions, dissectedby steep-sided valleys. A number of rivers (Neretva, Aoos,Arachthos, Acheloos, Alfeios, Evrotas) that emerge alongthe western slope of this mountain range lie exclusively oralmost exclusively in the External Balkanides. Their basinsconsist of Mesozoic-Palaeogene carbonates covered byPalaeogene flysch. Magmatic and metamorphic rocks areabsent in the basins of Neretva, Acheloos and Alfeios,whereas the headwaters of Arachthos and Aoos drain smallophiolite outcrops and the mountainous surroundings ofEvrotas basin include small portions of schists.

The Neretva is the largest river in the Dinaric Mts flow-ing for almost 250 km through a karstic area. It emerges atabout 1100 m asl at the base of the Zelengora Mts(2032 m asl). The headwaters are dominated by Triassicand Jurassic limestone and dolomite. The river flows througha sequence of bedrock canyons and plains. In the last 30 kmthe river widens and branches, spreading into a 200 km2

deltaic plain. The Neretva Delta, one of the largest wetlandsalong the Dalmatian coast, includes small shallow karsticcrypto-depression lakes, marshes and lagoons, fringed bylimestone outcrops.

The Aoos River (Photo 11.4) originates at the base of thePindos Mts (Mavrovouni peak 2159 m asl) and flowsthrough deep gorges and steep ravines. The Voidomatis trib-utary (384 km2), a partially intermittent river with a steep

gradient (1.6%), flows through the renowned Vikos Canyonand joins the Aoos in the Konitsa plateau just upstream of itsconfluence with the Sarandaporos tributary (870 km2). TheGamila summit, an imposing alpine ridge with enormousvertical slopes, is one of the few glacial landscapes inGreece. Here, the unique alpine lake Drakolimni (Dragon-lake) is located at an altitude of 2050 m asl. Flowing in a SE–NW direction, the Aoos is joined by the tributaries Drino,Zagori and B€enc€e. The lower meandering river channel is onaverage 25 m wide. The delta, with a well-defined cuspateshape, hosts the Natra Lagoon (33 km2). Carbonates (mainlylimestones) overlain by flysch, cover most of the catchment.Recent deposits include Messinian evaporites and Pliocenemolasses that outcrop between alluvial sediments.

The narrow Arachthos basin (Photo 11.5) drains the Pin-dos Mountain range, with main springs in the Tzoumerka(2429 m asl) and Lakmos (2295 m asl) Mts. A spectaculargorge (�30 km long) spans between the Tzoumerka and Xer-ovouni Mts. Among the numerous headwater tributaries, theKalaritikos (Photo 11.10) forms twomagnificent gorges southof Mt Lakmos. The Arachthos empties into the AmvrakikosGulf, 30 km east of the Louros river mouth. The uniquedouble-delta formation extends over 109 km2 (350 km2 withLouros delta), creating Greece’s largest coastal reed-swampand saltmarsh system fringed by coastal lagoons known as theAmvrakikos wetlands. The basin primarily consists of flysch(68% of the basin), while limestones and dolomites cover thewestern and northeastern parts (23%). Small ophiolite out-crops impinge on the northern part of the basin, while alluvialsediments cover the river valley and delta.

TheAcheloos (Photos 11.3 and 11.7) starts at 1700 m asland drains the rugged southern Pindos mountain range. Theriver enters the Agrinio plain where the average width of thechannel is 25 m with a maximum of 90 m in the deltaic area.Water depth is up to 7 m in the narrow gorges and 1–2 m inthe delta section. The large lobate-type delta covers 270 km2

and includes two large lagoons, Mesolonghi and Aetoliko.The bedrock consists of flysch (48% of the basin) and lime-stone (32%), while the valleys and the delta are covered bylacustrine Pliocene and alluvial sediments(20%). Small out-crops of Triassic evaporites appear in the lower basin.

TheAlfeios River starts at 1800 m asl at the Taygetos Mtand outflows into the Kyparissiakos Gulf. The surroundingMts reach up to 2338 m asl (Mt Menalo). The upper Alfeiosdrains the Megalopolis plateau where lignite ores areenclosed. The riverbed is composed of gravel and sand,having a mean valley slope of 0.37%. Sediments from theAlfeios River contribute to the longest coastal sand dunesystem in Greece. The arcuate-oblique delta type covers113 km2. The basin is formed by karstic limestones whilethe lowlands are covered by Pliocene (marine), Pleistocene(lacustrine and terrestrial) and alluvial sediments, underlainby Triassic evaporites.

The Evrotas (Photos 11.6 and 11.9) traverses a low-gradient narrow plain bound by the steep mountain rangesof Taygetos (west, 2407 m asl) and Parnon (east, 1935 m asl).

The river originates from the Taygetos Mt, near the springs ofAlfeios River and flows southwards through the Laconia ba-sin. It then crosses the Vrodamas limestone gorge and dis-charges into the Laconikos Gulf, where it creates a small(53 km2) arcuate-lobate delta. The mountainous area of thebasin is formed by limestones (42% of the basin) and flysch(29%). The lower parts are covered by marine Pliocene andalluvial sediments (28%).

The Drin, Aliakmon, Pinios and Sperchios Rivers flowfrom the eastern flanks of the Dinarides–Hellenides moun-tain range and are (except the lower Drin) within the InternalBalkanides. They drain ophiolites, acid metamorphic rocks(gneisses, micaschists, amphibolites and phyllites), granitoidintrusives and Mesozoic carbonates. The Aliakmon, Piniosand Sperchios Rivers emerge from the eastern slope of thePindos range and flow eastwards. Extended Tertiary (Eo-cene–Miocene) molassic sediments of the Meso-HellenicTrough (Aliakmon, Pinios) and Palaeogene flysch (Pinios,Sperchios) dominate their basins.

The Black Drin starts from the unique Prespa and OhridLakes and flows NNW–SSE along a rift valley fringed by thesteep forested Sar Mts (up to 2500 m asl). Its drainage areaincludes mafic/ultramafic rocks (Midrita ophiolite belt withimportant Cr, Fe and Ni ores), granites, volcanic and volca-no-sedimentary series. The White Drin mainly drains Neo-gene lacustrine and marine deposits of the Kosovo plateauand meets the main branch of the Drin in Albania. The lowerbasin is formed by Triassic-Cretaceous limestones, flysch/molasse and recent deposits. The river forms a delta withcoastal lagoons.

The Aliakmon (Photo 11.1) emerges in the Pindos Mts(Mt Gramos, 2520 m asl, is the highest peak). The river firstdrains a plain, where it receives water from Lake Kastoria andVenetikos-tributary. Then a section with reservoirs followsand downstream, the Almopeos and Edesseos tributaries en-ter in the Imathia plain though the T66-channel. Finally, theriver forms a 120 km2 Delta. The northern and southern basinconsists of metamorphic and acid igneous rocks (14.5% ofthe basin) and ophiolites (9.2%), overlain by Triassic lime-stones (15.7%). The western basin is covered by molassicdeposits (29.6%). Neogene-Quaternary terrestrial, lacustrineand marine sediments (31%) cover the lowlands.

The Pinios surrounded by high mountains (Pindos, Kam-vounia, Pieria, Olympos, Ossa and Orthrys), drains the vastThessaly plain, a former Pleistocene lake. Downstream of theconfluence with the Malakasiotikos, it becomes a lowlandmeandering river. Lowmountains (693 m asl) divide the plaininto a western and eastern part (Trikala and Larisa basins).Within the Trikala basin, the river widens up to 1.5 km form-ing a braided channel. Between Mts Olympos and Ossa, itpasses through the Tempe Gorge and discharges into theThermaikosGulf forming a 69 km2 radial-shaped delta.Meta-morphic and acid igneous rocks outcrop along the northernand eastern mountainous boundary (17.5% of the basin). Me-sozoic sediments of Triassic and Cretaceous age (limestones,dolomites and cherts) are mainly found on the Pindos range

(14.7%). Ophiolites (6.2%), underling these sediments, out-crop in erosional zones. Flysch andmolasse (15.8%) cover thewestern basin, where conglomerate molassic outcrops formimpressive landscape features. The Thessaly plain is filledwith Neogene and Quaternary fluvio-lacustrine deposits,which cover almost the half of the basin (47.9%).

The Sperchios becomes a river at 700 m asl at the foot ofTymfristos Mt (2327 m asl). The basin belongs to a narrowW–E orientated rift valley. The lower section of the river ismeandering and finally ends in the shallow muddy MaliakosGulf forming a 196 km2 lobate delta. The western basin iscovered by flysch (48% of the basin), which supplies theriverbed with gravel. Mesozoic dolomites and limestones(16%) extend in the SE and NE basin. In the N and NEportion (Mt Othrys), ophiolite complexes with Cr-ores cover12% of the basin. The valleys are filled by thick alluvialdeposits (24%).

The Axios basin starts at 750 m asl at the western slopesof Crna Gora Mountain (2062 m asl) and is bound to thenorth and west by the Sar Planina Mountain range(2748 m asl) and to the east by the ‘Surrounding’ MountainRanges (2252 m asl). In the headwaters, it receives theTreska-tributary (2068 km2) before entering the Skopje-Veles plains. The tributaries P�cinja (2840 km2), Bregalnicaand Crna join the river before it enters Greece through thenarrow Klisura Valley. Finally, it forms a wide bird-foot typedelta in the Thermaikos Gulf. The delta is also fed by theAliakmon, Loudias and Gallikos Rivers forming the mostextensive wetland area in Greece (area: 600 km2). Themountainous areas consist of metamorphic rocks, granitoidsand volcanic formations (43.5% of the basin), Mesozoiclimestones (11.4%) and ophiolites (7.7%). Igneous and vol-canic rocks are associated with mixed sulphides and areimportant sources of Pb–Zn ores. Flysch and molasse cover5.6% of the basin. Lacustrine and terrestrial Neogene andalluvial sediments (31.9%) fill the river valleys and the delta.

The Kamchia River emerges from the eastern flanks ofthe Balkan Mts and flows into the Black Sea. To the south,the Evros basin drains the large Thracian plain, bound to thesouth by the Rila-Rhodope Mts. The southern flanks of thismassif are drained by the Nestos and Strymon rivers bor-dered by Pirin Mt.

The Kamchia is a low-lying river emptying into theBlack Sea �40 km south of the city of Varna. The basin isfilled with Mesozoic-Palaeocene flysch and some Eocenemolasse overlaying the metamorphic and intrusive rocks,and is marked by Late Cretaceous andesitic volcanism.The lower basin is covered by Pliocene and Quaternarysediments.

The Strymon basin, confined to the north byMt Vitosha,starts at the base of Mancho peak (2378 m asl). Mt Rila(2925 m asl) and Pirin (2914 m asl) form the eastern andsoutheastern catchment boundaries. Initially, the river flowsthrough a mountainous terrain receiving a number of N–Sflowing tributaries (Konska, Svetia and Treklyanska) andthen turns to the south through a broad valley. It enters

Greece through the Rupel narrows, crosses the vast Serresplain forming the semi-natural Lake Kerkini and thenreceives the inflows of Aggitis karstic river. The river emp-ties in the Strymonikos Gulf forming a small delta (9 km2). Alarge portion of the basin (41.6%) is formed by acid meta-morphic and plutonic rocks, that is schists, amphibolites,gneiss and ultrabasics, intruded by granitoid and Paleogenevolcanic bodies (rhyolites, rhyodacites). Triassic carbonaterocks (marbles, limestones, dolomites) are restricted to thenorthern basin, while Palaeozoic marbles are found in the SE(mainly Aggitis basin). Carbonates cover 17.1% of the basin.Flysch deposits (5.2%) are restricted to the headwaters. Theriver valleys and the Serres–Drama plains are filled withterrestrial, lacustrine and marine Neogene and Quaternarysediments (33.7%).

The Nestos starts at the eastern slope of Rila Mt andforms a narrow mountainous basin, confined by the Strymoncatchment to the west, the Rhodope Mts to the east and theGulf of Kavala to the south. After the confluence of BijalaMesta and Cherna Mesta, the river flows through a rift plainbetween Mts Pirin and Rhodope, with their 109 small alpineglacial lakes and tarns. The headwater regions contain im-pressive geomorphologic structures, canyons and steep for-ested rocky gorges. Acid silicate rocks cover 68% of thebasin. Metamorphic formations (gneisses, amphibolites, mi-ca schists and marbles), Quaternary volcanics, with a varietyof base and precious metals mineralization and geothermalfields, and granite plutons shape the upper and middle parts.Just before its delta, between Stavroupolis and Toxotes, theriver cuts through the extensive karstic marble formation ofLekani Mt. Downstream of this impressive gorge, the riverspreads over a large flat deltaic area covered by lacustrineand terrestrial Neogene-Quaternary deposits (18% of thebasin area). Carbonate formations (13%), together with lim-ited Eocene–Oligocene molassic sediments, mainly occur inthe southern part. The 434 km2 arcuate delta consists of amosaic of sand dunes, freshwater lakes and ponds, coastallagoons and saltmarshes, and the relicts of the famous allu-vial forest Kotza Orman.

The Evros is a large lowland river draining the Thracianplain. It also emerges at the Rila Mt near the summit ofMusala and runs first through a steep glacier valley and theneast and southeast fringed by the Balkan and Rhodope Mtsbefore crossing the Thracian plain. It forms the Bulgarian-Greek border over a short distance before it flows along theGreek-Turkish border to the Aegean Sea. At �140 Rkm(Parvomai) it reaches 200 m width and 5 m depth and hasan unstable riverbed. In Greece, the river width reaches150 m. The 188 km2 lobate-shaped delta contains two majorlakes associated with swamps and extensive coastal lagoons.The Tundja tributary starts in Stara Planina Mts and flowsthrough a low elevation plain (average basin altitude:386 m asl) before entering the Evros at Edirne. The Ardariver, flowing through a medium elevation plain (648 m asl),joins the main stem in Greece. The Ergene tributary, flowingthrough the East Thrace (Turkey) plain, joins the main chan-

nel upstream of the delta. Acid silicate rocks make up 37.8%of the basin. The mountainous parts consist mainly of meta-morphic formations, granites and carbonates. Volcanic intru-sives (andesites, tuffs, monzonites, diorites) occur locallyand along the Maritsa fault. Important hydrothermal metal-logenic zones rich in Au, Ag, Cu, Pb and Zn ores extendalong the Balkan Mts and in the eastern basin. The Thracianplain is covered by Pliocene (including lignite ores) andQuaternary sediments. Lacustrine and terrestrial Neogeneand Quaternary sediments are the dominant basin formation(41.9%). Carbonate rocks comprise 10% of the basin.Palaeogene molassic deposits (9.4%) mainly cover theThracian plain.

11.5.2. Climate

Altitudinal gradients, a diverse mountainous relief, and theinfluence of theMediterranean and Black Seas create diverseclimatic conditions in the Balkan Peninsula. In general, theclimate is characterized by a distinct bimodal seasonalityand a strong N–S gradient, with increasing temperatureand decreasing precipitation towards the S–SE (Table11.1). The S–SE Balkans suffers from prolonged droughts.In the past decades, average precipitation decreased and thefrequency and severity of droughts increased (World Bank2003). In 2007, during prolonged summer heat waves, heavywildfires destroyed thousands of km2 of Balkan forests.

The Adriatic and Ionian basins receive a much higherprecipitation compared to the eastern Balkans. The DinaricAlps exhibit a moderate continental climate with cold wintersbut warm and humid summers, while the higher Mts have asubalpine climate with extended periods of snow cover.Therefore, many rivers show steep climatic gradients alongtheir course. The mean annual air temperature in the Neretvabasin is 9.2 �C but reaches >16 �C downstream of Mostar.The Drin basin has the lowest average air temperature(8.9 �C) of all examined basins, although its downstreamsection exhibits a Sub-Mediterranean climate with mild,wet winters and hot summers (mean annual air temperature:16–18 �C). Similarly, the upper section of the Aoos basinexperiences a moderate Sub-Mediterranean and the lowersection a Mediterranean climate. The highest precipitationoccurs along the central Adriatic Mts. In the Dinaric Mts,precipitation exceeds 300 cm, with up to 550 cm in SWMontenegro. In Albania, mean precipitation ranges from300 cm (Albanian Alps) to 130 cm (southern part). In NWGreece precipitation is maximal at 240 cm (upper Acheloosand Arachthos basins). The annual precipitation east of theDinarides–Hellenides range is 25–50 cm less than in thewestern peninsula. The upper Axios basin exhibits a climatesimilar to continental European with long cold winters. Thearea south of Skopje is considered as one of the driest regionsin FYR Macedonia. In winter, the dry ‘Vardar’ N-wind cre-ates harsh cold conditions. Large areas of Bulgaria are char-acterized by a drought-prone climate (Alexandrov 1995).

There, annual precipitation is <65 cm and potential evapora-tion exceeds 100 cm in most lowland sections. In the Pirin,Rila and Rhodope Mts, 30% of the annual precipitation fallsas snow. The lower Evros, Strymon and Nestos basins changefrom continental Mediterranean climatic conditions, to anInterior Sub-Mediterranean climate, and finally to a typicalMediterranean climate in the deltaic plains.

The Mediterranean climate, typical for Albania and mostof Greece, is influenced by local orographic effects. A south-ward and a less significant eastward increase in air temper-ature and evapotranspiration occurs (Dalezios et al. 2002).Many river stretches in S and SE Greece have intermittentflow regimes. Enclosed lowland parts of the mainland expe-rience a continental Mediterranean climatewith cold wintersand hot summers (e.g. mid-Aliakmon and Pinios basins),while upland reaches experience temperate continental con-ditions (e.g. upper Aliakmon). In the Pinios basin heavyrainfall may occur in winter and persistent droughts in sum-mer with temperatures >40 �C.

11.5.3. Land Use Patterns and HumanPressures

In most catchments, evidence of human appearance datesback to the late Pleistocene (Middle Palaeolithic). Duringthat period, the Balkan landscape experienced distinct cyclesfrom deciduous forests to dry steppe, indicating week glaci-ation. During the Neolithic era, humans started cultivatingcereals and legumes, and breeding domestic livestock (Bai-ley 2000). First settlements were established along rivers andaround lakes taking advantage of good grazing conditionsand naturally irrigated land. Prehistoric deforestation andsoil erosion have been attributed not only to climate change(Hempel 1982) but also to human activities (Butzer 2005).According to the ancient traveller Pausanias, the reason thatthe Echinades Islands, 10 km offshore of the Acheloos estu-ary, were not joined to the mainland was that Aetoliaremained untilled because the ancient Aetolians abandonedthe area reducing sediment fluxes. Since the Minoan period,rivers and streams have traditionally been used as naturalsewage systems. In addition, humans managed rivers bybuilding dams or diverting channels to protect their settle-ments against floods (Morhange et al. 2000). The geographerStrabo noted that flood Morhange structures had alreadybeen built 2500 BP along the Pinios River.

Large-scale deforestation occurred during the Roman,Byzantine and Ottoman Empires. Since the 15th century,rice fields have been irrigated through 560 km of canals inthe Thracian plain (Knight & Staneva 1996). However, upto the 19th century, when major shifts of settlements andland use ensued, many areas in the Balkans were considereda wilderness and were scarcely populated. During the 20thcentury, farming technologies improved, although animal-drawn plows and cart wheels are still common in Albania,Bulgaria and former Yugoslavia. In the 1920–1940s,

massive land reclamation took place in Greece to createnew land for people displaced from Asia Minor. Thisresulted in the drainage of lakes, marshes and lagoons(e.g. Lakes Yiannitsa, Amatovou and Ardjan in Axios areaand the marshes of Philippi in Strymon area), and channelsof large rivers were rearranged (Papayiannis 1992). Landreclamation continued with the construction of extensiveirrigation networks. As a result, northern Greece lost1150 km2, or 73%, of its original wetlands (Psilovikos1992). In Albania, extensive land reclamation and irriga-tion projects occurred during the past 50 years resulting in asignificant loss of its native forests and marshes (Cullajet al. 2005; Ciavola et al. 1999).

The first dams were already constructed between the 1stand 5th century BC in ancient Alyzia, one of the most im-portant cities of Acarnania (near the Acheloos basin). In the1950s, the first large dams were constructed in the Balkans.In Bulgaria, huge drainage and irrigation networks wereestablished together with interbasin water transfer projects(e.g. transfer from the Strymon and Nestos headwaters to theIskar and Evros basins) (Knight & Staneva 1996). In theNeretva basin, �50 km2 of wetlands were drained, severallarge dams constructed, and water transferred betweenbasins (EIA 2006). During the last decades, a lesser degreeof agricultural intensification relative to northern Europe hasbeen observed. However, increasing overall trends in theintensification process are apparent in the plains, especiallyin Greece, with increasing trends in agrochemical consump-tion and extensification in mountainous areas (Caraveli2000).

Landscape features and agriculture are intimately linked.The northeastern areas where almost treeless open land-scapes prevail are intensively used for arable crops. TheDinaric, Albanian and Balkan Mts are characterized by ex-tensively cultivated landscapes. In Albania and Greece,sharp contrasts between open cultivated andwilderness areasoccur. Cereals are grown at a large scale and olives coverhillsides where possible, while Mts are used for extensivegrazing. Yields are low due to moderate to high erosioncreating stony soils (cambisols, luvisols), the dry hot climateand intersection of arable land by shrublands. The Evros,Pinios, Strymon plains as well as the lower Axios and Ache-loos, including their main deltas, are fertile landscapes, in-tensively cultivated and densely populated (Meeus 1995). Asa consequence, the plains of Serres (Strymon basin), Thes-saloniki (lower parts of Axios and Aliakmon basins), Thes-saly (Pinios basin) and Arta (lower Arachthos basin) havebeen designated as NitrogenVulnerable Zones (Directive 91/676/EEC).

Since Greece joined the European Union in 1981 majorefforts have been devoted to control municipal wastes. To-day, >90% of the human population is connected to WasteWater Treatment Plants (WWTPs) (with 2/3 primary and 1/3secondary treatments) (NCE 2003). However, small villagesstill have simple sewage systems (permeable seep-tanks) thatmay drain through local aquifers into affluent rivers and

there is evidence of poorly functioning WWTPs in the smal-ler towns. In the other Balkan countries, municipal waste-water is rarely treated and even large towns are insufficientlyconnected to WWTPs. Moreover, the transition to a free-market economy caused new problems such as land erosion,increased use of fertilizer, soil salinization, loss of soil fer-tility and locally a reduction in biodiversity (Sumelious et al.2005). All Balkan countries face substantial solid wastemanagement problems and have a great number of illegal,uncontrolled landfills. In Greece, mining and industrial ac-tivities are limited. Heavy industry is concentrated mainly tolarge urban centres and seasonally operating food productionindustries comprise the main industrial pressure. The otherBalkan countries have developed significant mining and in-dustrial activities during the communist era. Since the be-ginning of the 1990s, these countries suffered from a majoreconomic crisis, with a reduction in mining, industrial andagricultural activities that led to an improvement in environ-mental conditions (UN/EC 1999, 2000, 2002a, b, c, d, 2007a,EIA 2006). It is characteristic that industries previouslyequipped with WWTPs have often not maintained their fa-cilities. Due to recent economic stability, potential pollutingindustries have been reactivated (e.g. Rastall et al. 2004).

Before the war, Bosnia and Herzegovina was the indus-trial heartland of former Yugoslavia. Most of its rivers wereseverely polluted. Today, theNeretva is affected by disposalof untreated municipal and industrial wastewaters, that is byheavy metals from metallurgy effluents (Konjic and Mostar)and from food, lumber, construction material and light in-dustries. Intense agricultural production (mainly citrus orch-ards) is limited to the delta area (EIA 2006). The firstsignificant morphological alteration occurred in the 1880s,when the Austrian–Hungarian government channelled22 km between Metkovic and Usce. This part of the riveris regularly dredged to ensure navigation and to preventflooding. Before dam construction and land reclamation,the lowlands were frequently inundated during winter form-ing a large deltaic lake. Dam construction resulted in saltwater intrusion in the lower Neretva and the destruction ofthe delta; of the initial 12 distributaries only three remain.

The Drin flows through mountainous terrains and wide,densely populated valleys. The lowland section has beendiked. In the Albanian part, half of the arable land is irrigat-ed, whereas mountainous areas remain virtually undisturbed.In the upper basin, iron and chromium mining along withindustrial activity affect Lake Ohrid, while copper, chromi-um, iron and nickel mining and processing (at a reduced ratein recent years) contaminate the middle and lower riversections as well as Lake Shkodra. Shkodra Lake is alsothreatened by the Moraca River that carries wastewater froman aluminium smelter in Montenegro (UN/EC 2002b). Un-sustainable agricultural practices have led to an increase innon-point pollution and erosion (Faloutsos et al. 2006).Gravel extraction from the riverbed favours bed incision.Moreover, the river and lakes are affected by untreated orinsufficiently treated municipal wastewater. Besides large

reservoir construction, other major hydrological interven-tions include stream diversions to Lakes Prespa and Ohrid.Finally, illegal logging impacts many tributaries.

The Kamchia receives annually �1.85 Mm3 industrialand 15.3 Mm3municipal wastewater (including water from astorage battery plant in Shoumen) (Mihailov et al. 2005).Flow regulation has caused a degradation of riparian vege-tation and localized habitat loss.

In the Aoos basin, traditional agro-silvo-pastoral activ-ities have been applied since the end of the 2nd millenniumBC (Lafe 2003). Today, most of the catchment remains in awild, almost untouched state with restricted agriculture,forestry, cattle breeding and some aquaculture. The riverreceives untreated effluents from five urban settlements(Konitsa, Permet, Argirokastro, Tepelen, Mamalje, Sele-nica), small-scale industrial areas and by-products of pe-troleum extraction in the lower section. There are no majordams disrupting the main river course. The lower part wasdiked in the 1960s and about one-third of the Narta lagoonhas been converted into a commercially operated salina.Local gravel and sand extraction and deforestation lead tobank erosion and sediment deposition (Troendle 2003).However, overall, the Aoos is considered as one of theleast modified rivers in Europe (Chatzinikolaou et al.2007).

The Evros and Tundja valleys have been colonized byhumans since the Neolithic era to exploit their fertile fluvialsoils (Bailey 2000). Today, the Evros basin hosts 3.6 millionpeople, mainly around Plovdiv, Stara Zagora, Haskovo,Pazardjik and Edirne and the river is possibly the most im-pacted of the Balkans. In the Bulgarian part and the Ardabasins, mining activities are intense and mostly untreatedindustrial effluents from heavy metal processing and platingunits, chemical, textile, paper and food industries, woodprocessing, tanneries and dye factories are released intothe river. In Turkey, industrial activities are concentratedaround Edirne (textile, pharmacy, dairy, tanneries). In thewhole basin, municipal WWTPs are inadequate to coverthe needs of the population. Agriculture is intense and theuse of agrochemicals is widespread, especially in the inten-sively cultivated plains of Plovdiv and Edirne and in down-stream sections. Other pressures comprise reservoirconstruction, extraction of inert material from the riverbedand large-scale deforestation. Land reclamation, includingextensive wetland drainage and canalisation, has led tocoastline erosion and the destruction of deltaic sand-barrierislets while groundwater exploitation has led to an increasein salinity.

Due to its rough relief, the Nestos basin has a low pop-ulation density and contains relatively natural upland areas.In Bulgaria, industrial point pollution is limited to timberindustries and uranium mining at Eleshnitza. Conditionsmay improve because industries at Razlog have beenshut down and mining activities are scheduled to cease(NATURNET 2006). Intensive deforestation, especiallyin the NW basin, has led to excessive erosion and

sedimentation. In Greece, only few agro-industrial units arepotential pollution sources. Municipal WWTPs are restrict-ed to Razlog and Chrisoupolis. Extensive agriculture is prac-ticed mostly along the stream valley, especially in theirrigated southern Bulgarian stretch and in the delta. Landreclamation has transformed 80% of the virgin deltaic KotzaOrman forest (140 km2 before World War II) to farmland,creating an extensive irrigation and drainage network(Ministry of Environment Baden-W€urttemberg 1990).Reservoirs, flood protection schemes, canalisation andembankments initiated the erosion of the delta (Stournaras1998) and caused a reduction of coastal marshlands. In ad-dition, groundwater exploitation from >2000 shallow wellsincreased salinization of the coastal aquifers.

In the Drama plain of the Strymon basin, humansestablished settlements already in the Neolithic. Croppingand grazing, especially during historical times, affectedsoil erosion and aggradation. During the Ottoman period(15th to early 20th century), the basin was intensivelyfarmed and grazed and native forests completely disap-peared from the plains and surrounding hills (Lespez2003). In ancient times, the Greek section was a wide,poorly drained valley with extensive marshes and shallowlakes. Two large shallow lakes survived until recently. In1927 the former Lake Kerkini covered an area of �5 km2

surrounded by 26 km2 of marshes and wetlands and theformer Lake Achinos covered 80 km2 with an additional88 km2 of wetlands (Petrou 1995). In the 1930s, LakeAchinos was drained and a dam was constructed for floodcontrol, transforming the Kerkini wetlands into a largesemi-natural lake. By the 1980s, almost the entire StrymonRiver in Greece was straightened and embanked. In theGreek part, �33 Mm3/year industrial (slaughterhouses,tanneries, food industries) and 7.3 Mm3/year municipalwastewaters are discharged into the river (HMD 2003).Four WWTPs in Bulgaria and three in Greece are in oper-ation. About 1400 km2 are irrigated land (900 km2 in theGreek section) (HMD 2003).

In the Axios basin, near Lake Doirani, early humanimpacts date back 2800 years BP, when deforestation andstock-breeding led to a replacement of native woody vege-tation by xerothermic plants (Athanasiadis et al. 2000). In the4th century BP, the river mouths of the Axios and Aliakmonwere 30 km further inland (Kapsimalis et al. 2005) and theancient cities of Pella and Skydra were located along thecoast. Massive sedimentation led to the formation of LakeYiannitsa, one of the largest deltaic swamps along the Ae-gean coast. In the early 1930s, drainage led to the loss of 70%of the former delta wetlands (Psilovikos 1992). During thelast 40 years, groundwater exploitation from numerous irri-gation wells considerably lowered the water table, and thedelta area subsided at a rate of up to 10 cm/year. Consequent-ly, the sea has expanded up to 2 km inland forcing authoritiesto construct coastal embankments (Stiros 2001). The basin isdensely populated and the Axios is one of the most impactedrivers of the Balkans. In FYR Macedonia, the main point

pollution sources are untreated industrial and municipalwastewater especially from metal and chemical industriessuch as agrochemical manufacturing from the cities of Velesand Skopje. Wastewater treatment plants exist only for fewcities. The most important nutrient point source is the fertil-izer plant of Veles (UNEP 2000). In FYR Macedonia, about50% of the catchment has been converted into agriculturalland, including �800 km2 irrigated land (NEAP 1996). Un-treated municipal wastewater release 4700 tons/year N and857 tons/year P into the river (NEAP 1996). In the Greekcatchment, water demand for irrigation and agricultural pol-lution constitute the most important human pressures. There,almost 80% of the catchment is intensively cultivated, in-cluding �1400 km2 irrigated land. Industry, mainly foodprocessing plants, plays a limited role because the bulk ofthe effluent is treated. The total annual input of nitrogen andphosphorous from industrial sources is 15 tons and 12 tons,respectively (Karageorgis et al. 2003).

7000 years BP, prehistoric man settled the southern shoreof lake Kastoria and cultivated the fertile land of the area.The upper part of Aliakmon basin is mainly covered byforests and open pastures, while agriculture (140 km2 irri-gated land) and agro-industrial production are localized.This part contributes 1073 tons N/year and 130 tons P/yearto the Polyfyto Reservoir in the upper section of the river(Skoulikidis et al. 1998a). In the middle section, mining forasbestos and chromium threatens the river, while three reser-voirs cover the valleys. Lignite combustion units in the cityof Ptolemais (lying just outside the basin) use the water fromthe Aliakmon for cooling. They are also a major source of airpollution (SO2, heavy metals) for the entire area. The lowerAliakmon is densely populated and used for intensive agri-culture (about 950 km2 irrigated land). The former extensivewetlands are drained by the canal T66. Land reclamationsincluded artificial diversion, alignment of the main riverchannel, and embankment of the right river bank. Reservoirshave substantially diminished sediment loads, with a conse-quent reduction of deltaic development, salinization of thedeltaic areas and deterioration of wetlands. The large citiesof the basin (Kastoria, Grevena, Kozani, Veria, Naousa) areserved byWWTP, while untreated urbanwastewater of smal-ler towns and villages and partly treated wastewater fromsmall industrial units (dairy farms, cheese-dairies, food pro-cessing plants, hatcheries, slaughterhouses, tanneries, textileindustries, dye-houses) are discharged directly into the river,its tributaries or affect groundwaters.

In the Pinios basin, the Thessaly plain was a vast lakeat the beginning of the Holocene that drained at the endof the Mesolithic era through the narrow Tempe passage(Leivaditis 1991). The latter was obstructed several timesin the historical epoch and the landscape changed from riverto lake and vice versa, forcing the ancient Greeks to deepenthe Tempe Gorge and embank the river against flooding(Papadimos 1975). In the 1930–1950s, levees were con-structed along the river and excess water from former LakeKarla, a relict of the ancient Thessaly Lake, was diverted

through ditches to the Pinios. Before it was completelydrained and converted into agricultural land in the late1960s, Lake Karla was one of the largest inland wetlandsin Greece. Today, the Thessaly plain is the most productiveregion in Greece and the Pinios basin the most cultivatedbasin in the Balkans (84% cropland). About 2750 km2 areirrigated. Groundwater exploitation resulted in lowering ofthe groundwater table by tens of meters (Marinos et al.1997). In the Thessaly plain, >230 000 tons of fertilizersand 2000 tons of pesticides are used per annum (Bellos etal. 2004). In addition, the river receives partly treated mu-nicipal wastewater. The largest city Larisa discharges about9.1 Mm3/year of treated sewage into the Pinios River, anoth-er 4.3 Mm3/year are from sugar factories, paper mills,slaughterhouses, olive-presses, dairy farms and dairies(Fytianos et al. 2002).

In the headwater and mountainous parts of the Ara-chthos basin, human activities are restricted to small ham-lets. About 180 km2 of the lowlands are intensivelycultivated and irrigated from�4000wells. The river receivestreated wastewater from the city of Arta, untreated sewagefrom small towns and villages and partly treated wastes fromsmall agro-industries (oil mills, fruit juice factories, dairyfarms and slaughterhouses) and stock breading units. Sand isextracted from the riverbed. Impacts of two reservoirs,placed at the lower portion of the river, include erosion ofthe riverbed, significant upstream propagation of the sea,salinization of aquifers and coastal lagoon waters and deltaicand sand-barrier erosion (Mertzanis 1997).

The Sperchios is a small basin dominated by semi-nat-ural features, particularly in its upper and mid portions. Thisdynamic delta lies just north of the famous Thermopylaebattlefield where the Greeks fought against the Persians in480 BC. The narrow Thermopylae pass was of strategic im-portance controlling the transition between the sea and thecoastal Mts. During the past 2500 years the delta expandedby 100 km2 (average: 4.1 ha/year). This average rate in-creased during the past century to 13 ha/year, mainly as aconsequence of deforestation (Zamani & Maroukian 1980),reaching 23.6 ha/year between 1943 and 1971 (Kotoulas1988). The former extensive marshes and riparian forestswere mostly converted into agricultural land by the middleof the 20th century through the construction of a spillwayconnecting the upper delta with the sea and of levees bor-dering the river. Today, �154 km2 are irrigated and22 700 tons of fertilizers and 306 tons of pesticides are ap-plied each year (Dassenakis et al. 2005). Urban wastewaterfrom the city of Lamia are treated, however, sewage of anumber of small towns and villages remain untreated. Be-sides olive oil refineries and small manufacturing units(slaughterhouses, dairies, a dye-house, a cannery), industrialpollution is limited.

The Acheloos drains one of the least populated Balkanbasins with mostly semi-naturally vegetated areas, especiallyin the upper and mid portions. Interest in draining and con-trolling floodwaters of the rivers’ delta is evident since an-

cient times as depicted in the myth of the battle of Herculeswith Acheloos the river god (Papadimos 1975). The shiftinglower course created conflicts between the classical Greektribes of Aetolia and Akarnania because the river was theborder. At the beginning of the 20th century, large swampsstill covered the western part of the delta. In the 1960–1970s,wetlands were drained and extensive reclamation works werecompleted to irrigate�500 km2 while from the 1960s onwardlarge hydropower reservoirs were being constructed. As aresult of siltation, the ancient shipyard of Oiniadaes(500 BC) is now about 9 km inland. Due to hydromorpholo-gical pressures (construction of dams and embankmentsalong the lower portion of the river, creation of an extensiveirrigation and drainage network and dredging of the riverchannel and the coastal lagoons), the Acheloos delta has beenconverted into a semi-natural regulated system (Psilovikos etal. 1995), with a dramatic reduction in sediment deposition,groundwater salinization and upstream sea water propaga-tion. Industry plays a minor role in the catchment. The majortowns (Agrinio, Messolonghi, Karpenisi, Stratos, Aetolikoand Thermo) are connected to WWTPs.

The Alfeios basin has been occupied by humans since thePalaeolithic and Neolithic periods. The ancient sanctuary ofOlympia is betweenAlfeios and its small Kladeos tributary. Inthe first centuries AD major alluviation events (as a result ofthe drainage of Pheneos karstic lake, connected undergroundwith Ladon tributary) buried the ancient city (Kraft et al.2005). To control floods, the lower river was diked. About230 km2 are irrigated. The former extensive coastal lagoonswere drained in the early 1970s (Agoulinitsa and Mourialagoons). Small agro-industrial units, partly served byWWTPs and livestock breeding farms are scattered through-out the basin. Municipal WWTP facilities are restricted to thetowns of Pyrgos, Megalopolis, Krestena and Olympia. In theupper section of the river, the Megalopolis lignite power plantproduces high SO2 emissions (134 000 tons/year) due to thebad quality of lignite and the absence of pollution abatementequipment (NTUA 1997). Illegal extraction of inert materialfrom the riverbed in the lower section resulted in bed incisionof up to 5 m (Yannopoulos & Manariotis 2005). In summer2007, wildfires burned large forested areas.

The great city of Sparta was located along the banks ofthe Evrotas. It flourished after 1000 BC when the DoriansoccupiedLaconia. In ancient times, the deltaic areawas a largeswamp that was drained in the 1930s. Today, the lower riverhas been diked to prevent flooding and to expand agriculturalland.The riverbed is regularly dredged. Landuse in thebasin ischaracteristic of the dryMediterranean and dominatedbyolivegroves. Over 90% of total nitrogen and phosphorous inputsoriginate from agriculture (Nikolaidis et al. 2006). Pointpollution sources comprise untreated and treated (city ofSparta)municipal wastewater and effluents from agro-industrialunits including>90 olive oil presses, orange juice factories,slaughterhouses, food industries and a plastic manufactur-ing plant – all concentrated around the city of Sparta.Wildfires in summer 2007 burned 216 km2 of Mt Parnon.

11.6. HYDROLOGY ANDBIOGEOCHEMISTRY

11.6.1. Hydrology and Temperature

Hydrological data are mainly derived fromUNESCO (www.rivdis.sr.unh.edu) and from the Hellenic Public Power Cor-poration (Tables 11.1 and 11.2). The total river discharge inthe European Mediterranean region is �330 km3/year(UNEP/MAP 2003). All Balkan rivers contribute 85 km3/year. The rivers included in this chapter contribute 83%(70 km3/year) to the Balkan discharge, or �21% to the Eu-ropean Mediterranean runoff. Because the eastern Balkanbasins exhibit a semi-arid climate, specific discharge islow, ranging between 4 and 14.9 L/s/km2. The western Bal-kan basins are characterized by high precipitation and spe-cific discharge ranges from 18.3 to 34.6 L/s/km2. The Drinand Neretva rank 3rd and 4th in total annual discharge of allrivers in the Mediterranean region (after the Rhone and thePo Rivers). A large proportion of Balkan rivers is affected byhydropower generation. Most rivers are strongly fragmentedby dams and flow regulation (Table 11.1). The Evros, Axios,Pinios, Alfeios and Aoos are ‘moderately fragmented’, whileonly the Sperchios and Evrotas are free-flowing.

The hydrological and thermal regime depends on theseasonal distribution and type of precipitation (rain or snow),as well as on hydrogeological features (e.g. karstic or alluvialaquifers, degree of surface/subsurface flow interactions).Balkan rivers reveal a strong seasonal hydrology, mostlyflashy in nature and with low summer flow. Three flowregime types are identified: (I) a pluvial type with dischargemaxima in winter, (II) a pluvio-nival type with maximumdischarge in winter and a second peak in spring (snowmelt)and (III) a nivo-pluvial type with maximum discharge inspring and a second peak in winter. Type I rivers includethe Neretva, Evros, Arachthos, Pinios, Sperchios, Acheloosand Alfeios Rivers, with 63–78% of their annual runoffbetween November and March. Drin, Aoos and Nestos be-long to type II, while Strymon, Axios, Aliakmon and Evrotasare type III rivers. In type II and III rivers, 20–30% of therunoff is derived from snowmelt. Dam operations smoothseasonal variations and result in a modification of the hydro-logical regime downstream of reservoirs. Thus, Acheloos,Nestos and Aliakmon now present high to maximum dis-charge in July due to peak hydropower production. Based onthe ratio between the long-term maximum and minimummonthly discharge (Table 11.2), four groups of rivers canbe distinguished. For regulated rivers such as the Neretva,Nestos, Acheloos and Aliakmon, the karstic Aggitis and inthe middle section of the Drin, the seasonal variation rangesbetween 1.5 and 3. The Axios, Alfeios (with karstic inflows)and Kamchia, as well as the upper Evros, Strymon andNestos exhibit moderate seasonal variations with ratios be-tween 3.2 and 7. The Aoos, lower Drin (Vau Deze), Strymon(Rupel), Evros (Edirne) and Arachthos show high hydrolog-ical variation with ratios between 7.6 and 15. Finally, the

Pinios, Aliakmon and Evrotas exhibit very high seasonalvariations (Table 11.2). Rock permeability drives baseflowcontribution in river flow and regulates seasonal runoff var-iation and floods. The correlation between the ratio and thepercentage contribution of baseflow in river runoff showsthat high baseflow contribution smoothens seasonal hydro-logical variation (Figure 11.2).

Over the past 40–45 years, the Balkan rivers have under-gone dramatic discharge reduction (Figure 11.3), a commonphenomenon for the entire Mediterranean region (UNEP/MAP 2003). In addition, a severe drought at the end of1980s – beginning 1990s created major water shortages (e.g. Mimikou 1993; Knight & Staneva 1996). Besides climatevariability and change, evaporation from reservoirs and ex-tensive water abstraction for irrigation diminish river runoff.The Evrotas has experienced a 79% discharge reduction(1974–2004), followed by Axios (57%, 1961–2000),Sperchios (48%, 1950–1990; Tsakalias & Koutsogiannis1995), Kamchia (38%, 1936–1986), Drin (31%, 1965–1984) and Arachthos (30%, 1982–2006). The annual dis-charge of the Aoos decreased by 24% (Greece) and 19%(Albania) (1964–1987), the discharge of the Acheloos de-creased by 11.6% (1980–2006) and of the Aliakmon by12.2% (1963–2006). In the Nestos, discharge remained sta-ble (0.8%, 1966–2006), whereas it increased in the Evros by7.5% (1963–1985).

On average, the Neretva reveals the lowest and Strymonthe highest mean annual water temperature (Table 11.3).Neretva, with a low snowmelt contribution to river runoffand substantial karstic flow shows weak seasonal variation.Reservoir outflow smooths seasonal variation and altersthe thermal regime in receiving water bodies. For example,thermal variation downstream the Acheloos reservoirs is lowwith minimum temperature in February and maximum inSeptember (in free-flowing rivers minimum water tempera-ture occurs in January and maximum between June andAugust). Based on long-term records (1948–2005), the meanannual temperature of the Neretva increased by 0.27 �C(average: 0.017 �C/year), the maximum annual temperatureincreased by 0.42 �C and the minimum temperature by1.7 �C. This is a general trend that also holds for all Greekrivers except the Strymon (Table 11.3).

The Neretva, despite a high annual precipitation, has alow stream density because water is lost to the underground.Karstic springs contribute substantially to surface flow(Stambuk-Giljanovic 1999). Trebisnjica, one of the longest‘subterranean’ rivers in the world, supplies water to theNeretva delta through karstic springs. In addition, excesswater from Trebisnjica is artificially transferred to the Ner-etva. Maximum runoff occurs in December and minimum inJuly–August. The upper basin is characterized by a nivo-pluvial flow regime, a high specific discharge (over 45 L/s/km2), and high water level fluctuations (up to 14 m nearMostar). Five hydropower plants in Bosnia and Herzegovina(Jablanica, Rama, Grabovica, Salakovac and Mostar) im-pound a total area of 36 km2 and store �1070 Mm3. In the

http://www.rivdis.sr.unh.edu/


TABLE 11.2 Discharge characteristics of the Balkan Rivers (in m3/s)

River Station Period A (km2) NQ MNQ MQ MHQ HQ MHQ/MNQ MAX/MIN Source

Neretvaa Opuzen 1946–2005 13300 23 48.3 69.5 114 193 2.4Metcovic 1946–2005 12311 43 60.7 93.2 163 297 2.7

Drin Ura e Dodes 1976–1984 5400 27 47.8 98.2 164 302 3.4Van Deze 1960–1968 12368 13 66.8 339 613 772 9.2

Kamchia Gzozdevo 1936–1986 4857 0.09 3.74 21.8 69.5 191 18.6Aoos Konitsa 1963–1971 665 4* 27 58*

Dorze 1965–1984 5420 21 36.1 146 260 595 7.2Evros Plovdiv 1936–1985 7931 2 14.2 51.6 123 258 8.7

Harmanli 1965–1979 19693 1.6 20.4 113 272 516 13.3Svilengrad 1936–1985 35165 0.7 27.1 110 299 911 11.0

Nestos Thysavrosb 1998–2005 3698 2.2 31 52.6 76 96.6 2.5Platanovrisib 2000–2006 4090 3.8 15.2 36.3 73.4 112 4.8Temenos 1966–1989 4393 2.7 9.7 44.5 111 199 11.4Stavroupoli 1989–2000 5509 0 4.4 26.4 84.4 406 19.2

Strymon Radzavitza 1965–1979 2171 1.5 3.5 11.7 30.5 41 8.7Krupnik 1965–1979 6777 5 13.5 47 111 157 8.2Rupel 1929–1932/1951–1956 10800 27* 110 228*

Axios Skopje 1978–1990 4650 6.6 24.3 57.3 102 164 4.2Axioupoli 1961–2000 20200 3.4 29.7 115 275 949 9.2

Aliakmon Ilarion 1962–1988 5505 2.1 4.57 48.3 138 369 30.1Polyfyto 1975–2006 5800 0 10.9 43.8 88.8 184 8.1Sfikia 1986–2006 6030 15 59.5 80.8 125 196 2.1Asomata 1986–2006 6180 0 8.6 58 89.6 191 10.4

Arachthos Tsimovo 1965–2003 640 0.250 3.51 18.2 51.1 97 14.6Pournari 1950–1980 1778 11.5* 62 130.9*Pournari I 1982–2006 1778 0 4.9 45.5 129 235 26.4Pournari II 1999–2006 1845 0 8.1 49 113 145 13.9

Acheloos Kremasta 1980–2006 3570 1.9 48.3 96.7 182 320 3.8Kastraki 1980–2006 4118 13 60.7 116 244 1118 4.0

Pinios Giannouli 1903–1911/1932–1942/1951–56

8563 11* 81 171*

Sperchios Kobotades 1932–1941/1949–1959 1165 12* 62 110*Alfeios Alfeiousa 1949–1956 3534 21* 67 145*Evrotas Vrodamas 1974–2004 2000 0 0 2.9 10.4 21.9 –

A: catchment area upstream of gauging station, NQ: lowest measured mean monthly discharge, MNQ: arithmetic mean of the lowest measured mean monthly discharge, MQ: arithmetic mean annual discharge, MHQ:

arithmetic mean annual of highest mean monthly discharge, HQ: highest measured mean monthly discharge, * arithmetic mean of month with minimum/maximum discharge, MAX/MIN: ratio between the month with

maximum discharge and the month with minimum discharge, PPC: Public Power Corporation, HMRDF: Hellenic Ministry of Rural Development and Food.a water level.b water used for hydropower production.

downstream section, flood control measures and karsticinputs (�26% of river runoff) reduce seasonal water levelfluctuations (Glamuzina et al. 2002).

The Drin originates from the Lake Ohrid-Prespa karsticsystem. The Prespa Lake (surface area: 274 km2, basin:1300 km2, mean depth: 16 m, maximum depth 47 m) con-tributes to Lake Ohrid about half of its karstic groundwaterinflows (Amataj et al. 2007). During the past 20 years adecline of the water level in Lake Prespa has been observed.Lake Ohrid discharges 0.69 km3/year through an artificially-controlled outlet into the Black Drin. It is a deep lake (meandepth: 155 m, maximum depth: 288 m) that covers 358 km2

and drains 1310 km2. Lake Shkodra (basin area: 5180 km2),receives its waters mainly by the Moraca River (99 km long)and drains into the 44 km long Buna River that joins the Drin1.5 km before the mouth. The hydrological regime ofBuna and the water level of Shkodra depend on the flow ofthe Drin. During winter floods, the Drin floods back intothe Buna, and consequently the lake experiences floodingfrom Drin water (Faloutsos et al. 2006). As a result, the lakesurface varies from 372 to 542 km2 and the maximumdepth exceeds more than five times the mean (8 m). Inthe mountainous basin, three groups of glacial lakes (Lura,Ballgjaj and Dhoski) are found. Snowmelt in the upper partof the river causes discharge maxima in May, while in the

lower section maxima occur in December. Seasonal dis-charge variation increases downstream (Table 11.2). Twohydropower plants are in FYRMacedonia (Globochica andSpilje) and three in the lower Drin in Albania (Komani,Vau Deza and Fierza). Fierza, covering 97 km2, is thelargest in Albania.

Of the two Kamchia branches, Golyama is consideredthe main stem. Two reservoirs are along Luda Kamchia(Kamchia and Tzoveno) and a third one (Tiche) is formedthrough the confluence of three Golyama tributaries.The Kamchia reservoir provides most of the drinkingwater for the cities of Burgas and Varna (storage capacity:229 Mm3). After reservoir construction, the total flow de-creased from 0.87 to 0.61 km3/year (Jaoshvili 2002). Theriver exhibits a strong seasonal regime with maximumflow in February/March and minimum flow in October(Table 11.2).

FIGURE 11.2 Correlation between baseflow contribution to river flowand the ratio of maximum to minimum monthly discharge.

TABLE 11.3 Inter-annual and intra-annual variations of river water temperature (period: 1977–2003)

River Station Inter-annual Intra-annual

Mean Range S.D. Trend (�C/year) Range S.D.

Neretva Metcovic 12.15 3.3 0.64 0.052 11.1 4.04Evros Dikea 15.61 9.49 1.9 0.014 18.1 6.86Nestos Papades 15.89 9.27 2.19 0.16 18.4 6.14Strymon Rupel 18.09 7.08 1.94 �0.024 15.1 5.51Axios Axioupoli 15.25 4.27 1.13 0.029 18.5 6.81Aliakmon Ilarion 15.02 4.73 0.97 0.014 17.9 6.86Pinios Larisa 17.31 12.88 2.25 0.009 17 6.58Acheloos Kastraki 14.96 4.61 1.22 0.065 10.36 4.01

SD: standard deviation.

FIGURE 11.3 Long-term discharge variation (mean annual discharge) inselected Balkan rivers.

The Aoos catchment has a high stream density (0.92 km/km2) and a high runoff coefficient (0.95 at Konitsa) due tothe dominance of flysch. Maximum flow occurs in Decem-ber and minimum in August–September. Between 21% and25% of the flow originates from snowmelt and �66% fromrain. Seasonal hydrological variation decreases from theheadwaters downstream. A small artificial lake (surface area11.5 km2, total storage capacity 260 Mm3) was created at thesubalpine plateau (1400 m asl) that diverts �10% of Aooswater towards the Arachthos basin.

The Evros has about 100 tributaries. Discharge data arelimited for the Evros, therefore only estimates on total an-nual runoff are presented (Table 11.2). Mean annual dis-charge of the Arda tributary is 2.2 km3, of Tundja 1.08 km3

and of Ergene 0.87 km3. Maximum flow occurs betweenMarch and May, minimum between July and September.Rainfall contributes 52–55% to discharge in the upper (Plov-div) and middle (Harmanli) basin, respectively, andincreases to 71% at Edirne. Seasonal discharge variationincreases, respectively (Table 11.2). There are 21 large reser-voirs, mainly along Bulgarian tributaries (four in Ardas andthree in Tundja) with a total storage capacity of 3440 Mm3.Despite numerous reservoirs, runoff remains highly variablewith frequent severe floods. Among themost disastrous werethe floods in 2005 and 2006 (UN/EC 2007b).

The Nestos is snow fed in the Mts and rain fed in thelower reaches. In the middle section (at Temenos) rain andsnow contribute �54% and �28%, respectively, to total dis-charge. Maximum flow occurs in spring (in May in the upperpart and in April in the lower part of the basin), and minimumin August–September. In Bulgaria, six reservoirs are ontributaries, the largest is on the Dospatis (total storage capac-ity 430 Mm3). In Greece, three large hydropower reservoirs,Thysavros, Platanovrisi and Temenos (under construction)and a small irrigation dam (Toxotes), occur along the mainstem. The former two cover 56 km2 and can store 798 Mm3.

In the Bulgarian part of the Strymon, the runoff coef-ficient varies substantially (0.01–0.95) (Knight et al. 2001).In Bulgaria, 56 multipurpose reservoirs with a total storagecapacity of 141 Mm3 have been constructed. Pchelina(area: 5.4 km2, capacity: 55 Mm3), Studena (capacity:25 Mm3) and Djakovo are the largest. However, the riskof flooding is high. Moving downstream, the ratio betweenmonthly maximum (May) and minimum (August) dis-charge increases: 4.2 at Radzavitza, 5.0 in Krupnic and8.4 in Rupel. The water balance in the Greek sub-basin ispositive (Tzimopoulos et al. 2007). The Aggitis tributaryhas a mean annual discharge of 0.55 km3 (8.3 L/s/km2). TheKerkini reservoir has a surface area of 109 km2 and a totalstorage capacity of 365 Mm3. It has amaximumdepth of 10 m(average: 1 to 3 m). Upstream of the lake, the river ceasessurface flow in summer due towater abstraction for irrigation.

TheAxios still exhibits a near-natural flow regime. High-est flow occurs in April and minimum in August. Rain andsnow contribute 53% and 30%, respectively, to total flow.The mean annual runoff of Crna is 1.18 km3, of Treska

0.76 km3, of Bregalnica 0.44 km3 and of P�cinja 0.40 km3.Until recently, floods caused major damages. For examplethe city of Skopje was destroyed in 1963. To control floods,17 large dams have been constructed at river tributaries inFYRMacedonia with a total storage capacity>500 Mm3. Asmall irrigation dam at the delta remains closed betweenMay and September, allowing only �1 m3/s to pass duringthe dry period (Konstantinidis 1989). Doirani Lake has anarea of �40 km2 (basin area: 272 km2), a total volume of50.7 Mm3, and a maximum depth of 10 m. Overflow waterenters the Axios through an artificial canal. Since the end ofthe 1990s, the water level of Lake Doirani has been recedingas a result of drought and overexploitation for irrigation inGreece.

In the free-flowing upper Aliakmon, the ratio be-tween monthly maximum (March) and minimum (August–September) discharge is one of the highest in the Balkans(Table 11.2). About 70% of the river is hydrologically heavilymodified due to damming. Reservoirs (Polyfyto Sfikia andAsomata) cover 81 km2 and can store�2.9 km3. Downstreamof reservoirs, maximum discharge occurs in summer and min-imum in spring. The shallow karstic Kastoria Lake (28 km2,mean depth: 4.4 m) overflows in theAliakmon through a ditch.

Pinios has only one major dam along the Smokovo trib-utary, although many small temporary earthen dams areconstructed by farmers to serve irrigation. However, irriga-tion has deteriorated the water balance, which is stronglynegative (reaching up to�1.2 km3/year; Loukas et al. 2006).As a result, the river partly dries out during dry years.Simultaneously the river has a flashy regime (Table 11.2)and despite flood protectionmeasures severe floods continueto threat the region.

The mostly unregulated Sperchios River receives 63mainly torrential tributaries. About 69% and 19% of riverflow originates from rain and snow, respectively. Flushfloods and high sediment loads cause frequent damages todownstream villages, agriculture and infrastructure.

The runoff of theAcheloos is caused by rain (�71%) andsnowmelt (19%). The runoff coefficient decreases from 0.65(headwater at Mesohora) to 0.51 (mouth). In the headwaterand middle sections, four large reservoirs (Kremasta, Kas-traki, Stratos and Plastiras) exist and two (Mesohora andSykia) are under construction. These reservoirs will cover>150 km2 with a total storage capacity of �6.6 km3, �1.5times the total annual discharge. From the Plastiras reservoir,�0.15 km3/year are transferred to the Pinios basin. Prior todam construction, maximum discharge occurred in Decem-ber and minimum in August. Today, discharge peaks in Julyand 30% of the annual flow occurs during summer (com-pared to 11% prior to dam construction). In the lower sec-tion, the natural Trichonis karstic lake (97 km2, maximumdepth: 59 m, volume: 2.8 km3) is connected to the 13 km2

shallow alluvial Lake Lysimachia through an artificial canal.Excess water from these lakes is transferred to Acheloos.The river is also connected to the shallow alluvial LakeOzeros during floods.

TheArachthos basin has a high stream density (0.91 km/km2; Karibalis et al. 2001), high specific discharge and aflashy flow regime (Table 11.2). Maximum discharge occursin December–January and minimum in August. The reser-voirs Pournari I and II cover 21 km2 and can store�800 Mm3. These reservoirs decrease seasonal flow varia-tions but only slightly alter the relative seasonal flow varia-tion. Water losses through irrigation (130 Mm3/year) andevaporation from reservoirs (12.5 Mm3/year) are counterbalanced by water transferred from the Aoos River(138 Mm3, Mertzanis 1997).

The Alfeios is partly supplied by karstic runoff. TheLadon and Lousios tributaries contribute 0.64 and0.21 km3/year, respectively. Maximum discharge occurs inJanuary and minimum in August, while the Ladon shows itsmaximum flow 1 month later due to karstic influence. In thedownstream section, baseflow contributes �14% to totalrunoff, compared to�73% by rain. In the upper basin, base-flow contribution is higher (23%) due to karstic inflows. Asmall hydroelectric dam along the Ladon tributary (4 km2,total storage capacity: 58 Mm3) is used for flood control andirrigation and a small dam located 10 km upstream of themouth, serves irrigation.

Due to intensive water abstraction, drought and hightransmission losses, parts of Evrotas show an intermittentflow regime. From its tributaries, only the Oinous ensures apermanent flow for most of the year. Apart from significantdirect water abstractions for irrigation, the river remainsunregulated, only localized earthen water abstraction weirsexist in summer. It has a flashy flow regime causing severefloods. Snowmelt (almost 40% of river runoff) and karsticoutflow lead to discharge maxima in March.

11.6.2. Biogeochemistry

In Greece, medium and large rivers have been monitoredsince the 1970s at monthly intervals for chemical quality(Ministry of Rural Development and Food, HMRDF andMinistry for the Environment Physical Planning and PublicWorks, HME), whereas studies have focused on their hydro-chemical regime and pollution status (Skoulikidis 1993;Skoulikidis et al. 1998b, 2006; Nikolaou et al. 2002; Lekkaset al. 2004; Konstantinou et al. 2006). For the other Balkancountries, such data are often not available or inaccessible.Moreover, most technical reports and scientific publicationsare written in the native language. The Greek data presentedare from HME and HMRDF as well as from scientific pub-lications and technical reports. For the other Balkan coun-tries, we used the EIONET database as well as informationderived from scientific publications.

11.6.3. General Characterization

The geology and climate are the main controllers of thehydrochemical regime. Geochemical and hydrogeological

variability as well as precipitation patterns control watertemperature and solute concentrations. Further, wastewaterdischarge, reservoir outflow and water abstraction locallyaffect chemical composition. The southern Balkan riversbelong to three hydrochemical zones with distinct hydroche-mical composition. Zone 1 rivers (Evros, Nestos, Strymonand Axios) are of an acid silicate type with low air temper-ature. Zone 2 rivers (Aliakmon, Pinios and Sperchios) be-long to a mafic silicate type, together with low precipitation.Zone 3 rivers (Aoos, Acheloos, Arachthos, Alfeios and Evro-tas) are of a carbonate type, and generally with high precip-itation (Skoulikidis et al. 2006). Zones 1 and 2 correspond toIlle’s ecoregions 6 and 7, while zones 2 and 3 correspond tothe geologic (and hence geochemically) and climatic diverseInternal and External Hellenides. It is speculated that thishydrochemical zonation is broadly applicable to the entireBalkan Peninsula. For example the Kamchia basin lies in theextension of zone 1 to the north, while the extension of zone3, west of the Dinarides-Albanides range, covers the Drinand Neretva basins.

The majority of the Balkan rivers belong to the calcium-carbonate hydrochemical type (Ca > Mg > Na > K–HCO3 > SO4 > Cl) (in meq/L), similar to the average ofrivers worldwide (Meybeck 1981). The Aoos headwatersare of a magnesium carbonate type (Mg > Ca). In Evros,Acheloos and Kamchia and in Nestos and Aliakmon head-waters, sodium is the second dominant cation while chlorideis in Acheloos and Arachthos. In general, total dissolvedsolid concentration increases downstream and is proportion-al to the percentage of recent (Neogene and Quaternary)sediments in the river basins. The reasons include high sur-face/groundwater interaction in areas with vast alluvial aqui-fers, high weathering and dissolution capacity ofunconsolidated sediments, and a downstream increase inpollution and evapotranspiration (Skoulikidis 1993). Forexample Nestos reveals pronounced upstream/downstreamhydrochemical differences, as it flows from the RhodopeMts, where weathering resistant rocks dominate and theclimate is Transitional Mediterranean, to karstic formationsand deltaic sediments, where the Mediterranean climate pre-vails (Skoulikidis 1991).

Rivers in the northern part of zone 3 (Acheloos, Ara-chthos, Aoos) are only slightly mineralized due to high pre-cipitation, causing dilution, and the dominance of poorlyleached soils in their catchments. In the Peloponnese(Alfeios, Evrotas), mineralization increases southwards asclimate becomes semi-arid. Evrotas, at the southern part ofzone 3, exhibits the maximum mineralization of all exam-ined Balkan rivers. Rivers in zone 2 (Aliakmon, Pinios,Sperchios and Aoos headwaters) present hard waters andare enriched with magnesium carbonate due to ophioliteweathering. In zone 1, the prevalence of magmatic and meta-morphic rocks with sulphide ore dykes cause low (Nestos,Kamchia) to medium (Strymon, Axios) mineralization asso-ciated with high alkali and sulphate ion percentages (Evros,Kamchia, Nestos, Strymon, Axios) and generally medium

hardness. Despite its position within zone 1, Evros presentsexceptionally high mineralization (caused by elevated sul-phate concentration), as a result of human impact (mining,industrial and municipal wastewaters) (Skoulikidis 1993).The Alfeios has the second highest sulphate concentrationbehind Evros due to gypsum dissolution and lignite miningand combustion (Skoulikidis et al. 2006). Increased chlorideconcentrations are caused bymunicipal wastes (Evros, Evro-tas and Axios), marine deposits (Sperchios), evapotranspira-tion (Lake Doirani) and/or marine aerosol (Acheloos,Arachthos).

Heracleitus (�500 BC) said that ‘No man ever steps inthe same river twice’. This means that a river is not the sameat two different times, an aphorism that fully reflects thestrong temporal hydrological and chemical variability ofBalkan rivers.Most Balkan rivers reveal larger temporal thanspatial hydrochemical variation governed by the factorsdrought, dilution and flush flows (Skoulikidis & Kondylakis1997). In general, specific conductance peaks during baseflow conditions and is lowest during spring (snowmelt) andwinter (rainfall). Thus, an inverse relationship between dis-charge and conductivity is commonly apparent (e.g. Figure11.4). Such rivers are termed as ‘dilution type’ (Skoulikidis1993). Floods are associated with soil–salt flushing and oc-casionally can enhance solute concentrations. The Aliakmonis a characteristic ‘flush type’ river showing maximum min-eralization in winter (December). For the Evros, Strymonand Pinios, weak flushing processes occur in winter (Decem-ber, January) and for Axios in autumn (October). The Piniosexhibits maximum mineralization in autumn (October), lowlevels in July–August and March and a minimum in Decem-ber. This peculiar monthly chemograph is driven by in-creased dilution in December and March due to peakrainfall and snowmelt, respectively, and possibly by photo-synthetically induced carbonate precipitation in pool domi-nated reaches during the dry period. Karst dominated riverswith weak seasonal runoff fluctuations, such as the Neretva,Aggitis and Evrotas, show low seasonal solute variations.

Regulated rivers reveal an artificial temporal chemograph.For example in Acheloos, solute concentrations are low insummer as a result of carbonate precipitation in upstreamreservoirs and high in winter due to inputs of hypolimnionwaters (Skoulikidis 2002). The increase in solutes during aperiod of severe drought (end of the 1980s – beginning of the1990s) demonstrates the impact of climate variability onriver hydrochemistry. At that time, the conductivity in Axiosrose by �40% compared with previous years (Skoulikidiset al. 1998b).

11.6.4. Sediment Loads (Long-Term Trends)

The sediment transport data are from Poulos et al. (1996),Gergov (1996), Poulos and Chronis (1997), UNEP/MAP(2003), Eurosion (2004), Becvar (2005) and Zarris et al.(2006). Balkan rivers tend to have naturally high sedimentfluxes due to high relief ratios, high seasonal climatic vari-ation, easily erodible rock formations and sparse vegetation.Fluxes have further increased by massive deforestation, fire,grazing and other human activities such as mining(e.g. Ardas River). The estimated total natural sediment fluxof all rivers examined is 115 Mt/year (UNEP/MAP 2003;Eurosion 2004). In the western Balkans (Arachthos, Aoos,Acheloos, Drin and Neretva basins), high precipitation incombination with flysch bedrock cause specific sedimentyields of 1000–16 000 tons/km2/year. In autumn, heavyinitial rains on desiccated soils often cause landslides, espe-cially where unconsolidated sediments prevail. During thefirst flush events, occurs often 50% to 95% of the annualsediment transport (Poulos et al. 1996). In the eastern basins,where magmatic and metamorphic rocks prevail (Kamchia,Evros, Tundja, Nestos, Strymon and Axios) and sedimenttransport mainly peaks during snowmelt, sediment yields arelow and range between 9 and 200 tons/km2/year. Basinsformed by a mixture of bedrock types (Sperchios, Aliakmonand Pinios) exhibit intermediate sediment yields (460–1000 tons/km2/year). The organic fraction of suspended

FIGURE 11.4 Correlations between discharge and spe-cific conductance and discharge and nitrate concentrationin the Axios and Axioupolis Rivers (data: Hellenic Minis-try of Agricultural Development and Food, period: 1971–2000).

sediments transferred by major Balkan rivers is low (onaverage 2.83% POC, 1.69% PN). More than 50% of theinorganic fraction consists of muscovite-illite (�27%) andsilica (�25%) (Skoulikidis 1989).

In general, total sediment flux increases with catchmentarea. Hence, the total load of the Evros, Axios, Drin andNeretva Rivers is between 14 and 26 Mt/year. However, highsediment transport also occurs in small narrow mountainousbasins such as the Aoos and Arachthos with 8.4 and 7.3 Mt/year, respectively. The Aliakmon, Pinios and Strymon havesimilar fluxes (between 4.8 and 4.1 Mt/year), followed byAcheloos and Sperchios (�2 Mt/year), while the flat Kam-chia basin transports only 0.46 Mt/year (Cagatay 1997).Since the Mediterranean Sea is characterized by low waveenergy and negligible tidal activity, the aerial extent of del-taic areas is correlated to sediment fluxes. However, this isnot true for the large Pinios and Strymon basins. The PiniosRiver has a relatively small delta due to its low-gradient andcyclic basin shape that retains most sediment. Similarly,Strymon has a surprisingly small deltaic area as a conse-quence of sediment trapping in the former Achinos Lake.

The long-term decline in river runoff, in combinationwith enhanced sediment retention in reservoirs, has resultedin a dramatic reduction in sediment fluxes during the past 50years. For example the sediment transport of the StrymonRiver has decreased from 6.5 Mt/year (1932–1962) to2.2 Mt/year (1962–1977) and to 1.3 Mt/year (1984–1990)(Crivelli et al. 1995; Psilovikos et al. 1994). The Drin expe-rienced a 13-fold sediment reduction compared to pre-indus-trial rates (REAP 2006). Today, the proportion of the annualsediment flux trapped behind reservoirs is �99% for theAcheloos, 95% for Nestos, 85% for Aliakmon, 80%for Arachthos and 60% for Kamchia (Piper & Panagos1981; Mertzanis 1997; Paraskevopoulos-Georgiadis 2001;Jaoshvili 2002; Kapsimalis et al. 2005). Consequently, del-taic areas of dammed rivers are not expanding (Poulos et al.1996) or have even started to decrease in size (Stournaras1998). It is predicted that the sandy beaches and islandbarriers of the Acheloos delta will gradually erode and coast-al lagoons will be intruded by sea water (Bouzos et al. 1994).Global sea level rise will further accelerate the destruction ofmany deltaic areas of the Balkans.

11.6.5. Nutrients and Pollution

Table 11.4 lists the basic information about dissolved oxygenand nutrient concentrations in Balkan Rivers. To ensurecomparability among rivers, we only report data from thelowermost monitoring station. On average, the Balkan riversare well oxygenated with oxygen concentrations rangingfrom 10.5 mg (Sperchios) to 7.2 (Kamchia) mg/L. Minimummonthly values range from 9.5 mg (Aliakmon) to 5.8 (Evros)mg/L. Oxygen concentrations<5 mg/L are only sporadical-ly recorded (e.g. Evros: 4.2% of all measurements). Mini-mum oxygen concentrations occur in summer. In Axios,

Aliakmon (upstream of the dams) and Strymon, the correla-tion coefficient (r2) between monthly water temperature anddissolved oxygen range from 0.78 to 0.91 indicating thatoxygen concentration is mainly physically driven. In Pinios,Nestos and Acheloos, the coefficient varies between 0.63and 0.45 suggesting a higher biological influence, while inEvros no correlation exists between water temperature andoxygen. In fact, Evros, Nestos and Acheloos have high ox-ygen concentrations in summer as a consequence of in-creased photosynthesis in-stream (Evros, Nestos) or inupstream reservoirs (Acheloos).

Figure 11.5 shows multi-year average nutrient levels inthe Balkan rivers. The upper Aoos presents minimum con-centrations of DIN (dissolved inorganic nitrogen), followedby the Acheloos. Of all examined rivers, the Drin shows amaximum DIN, followed by Evros, Evrotas, Kamchia andAxios. The Drin also exhibits the highest nitrate concentra-tion, followed by Evros, Pinios and Axios. These rivers score‘bad’ in nitrate quality according to a classification systemdeveloped by Skoulikidis et al. (2006). The lower Aoos (inAlbania), Evrotas and Strymon exhibit ‘poor’ nitrate qualitystatus. Nestos, Kamchia, Alfeios, Aliakmon and Neretvapresent a ‘moderate’ and Acheloos and Aoos (in Greece) a‘good’ status. Concerning nitrite, Evros, with a maximumconcentration, has a ‘bad’ status, followed by lower Aoos (inAlbania), Axios, Kamchia and Evrotas which have ‘poor’status. The Drin, Strymon, Nestos, Pinios, upper Aoos (inGreece) and Aliakmon are classified as ‘moderate’, whileAcheloos, Evrotas, Alfeios and Neretva have ‘good’ status.Maximum ammonia levels place Kamchia in ‘poor’ statusand Aliakmon, Evros, Axios, Nestos, Strymon, Pinios andEvrotas in ‘moderate’ status, while the rest of the rivers(Alfeios, Evrotas, Aoos/Vjose, Acheloos, Drin and Neretva)have ‘good’ status. The ammonia share of DIN in the exam-ined rivers shows dramatic variation. In the Drin, the ammo-nia proportion is minimum (0.7–1.1%). In Neretva, a 10-folddownstream ammonia concentration increase is evident(0.5% in Bosnia and Herzegovina and 5.6% in Croatia). Inthe majority of Greek rivers (Evros, Nestos, Strymon, Axios,Pinios, Alfeios) the ammonia share of DIN ranges between2% and 6%. The Acheloos, Aoos and Aliakmon show higherammonia portions (12–17%). In Bulgarian river stretches,ammonia comprises even higher proportions (21–23% inNestos, Strymon and Kamchia, 25–28% in Evros, Tundjaand Arda), indicating municipal wastewater impact. TheAxios in FYR Macedonia shows the maximum ammoniaportion (44%), reaching 75% and 89% downstream ofSkopje and Veles, respectively. The organic fraction of totaldissolved nitrogen is 40% in the lower Acheloos, 50% in theupper Aliakmon and 65% in the upper Drin, while in riversheavily affected by inorganic fertilizers the organic fractiondecreases; 33% in T66 (Aliakmon-ditch), 35% in lowerAxios and 11.5% in lower Strymon (Voutsa et al. 2001;Skoulikidis et al. 2001; Ovezikoglou et al. 2003; Borgvanget al. 2006). Rivers of zone 3 (Alfeios, Evrotas, Aoos, Ache-loos) have the lowest total phosphorus (TP) concentrations.

TABLE 11.4 Water quality characteristics of the Balkan Rivers

River Station DO (mg/l) N–NO3 (mg/l) N–NO2 (mg/l) N–NH4 (mg/l) TP (mg/l) DIN (mg/l) Source, period (comments)

Aliakmon Ilarion Average 10.9 0.68 8 140 20 0.82Median 11.0 0.49 5 23 10 0.52Range 6.0–14.5 0.005–3.64 0.09–137 2.3–13246 1–118 0.007–17Count 192 240 180Period 1980–95 1980–00 1980–94

Evros Dikea(near border)

Average 8.9 3.47 165 105 668 3.74Median 9.4 3.18 18 31 555 3.23Range 1.2–12.5 0.02–22.4 0.30–3729 0.67–1675 65–2668 0.02–27.8Count 78 91 91Period 1980–95 1980–01 1980–94

Axios Brige Axioupoli(near border)


Nestos Papades(near border)


Pinios Larisa Average 10.5 1.92 13 63 77 1.99Median 10.7 1.60 8 36 65 1.64Range 1–14 0.08–12.1 0.30–213 6.2–709 2–340 0.08–13Count 201 241 181Period 1979–95 1979–00 1979–94

Strymon Rupel(near border)


Acheloos DownstreamKastraki reservoir

Average 10.9 0.32 7 43 21 0.37Median 11.0 0.18 4 26 10 0.21Range 6.0–13.7 0.004–4.85 0.30–79 4.7–424 0.51–663 0.01–5.36Count 192 252 180Period 1980–95 1980–01 1980–94

Aoos Konitsa brige Average 10 <0.22 10 <36 19.6 <0.27Median 10.1 <0.1 64 <19 <0.18Range 6–15.2 <0.1–2.20 <0.3–47 <19–222 <0.12–2.47

Sperchios Basin average 0.75 5.2 83.2 15.2* 0.89

Alfeios Floka dam(near mouth)

Average 10.1 0.69 <5.5 <54 <16 <0.74Median 10.1 0.70 <3.6 <19 <10 <0.73Range 8–12.2 <0.1–1.30 0.00–44 <19–222 <10–65 <0.12–1.57

Evrotas 6 stations Average 8.9 1.21 21 65 <21 1.30Median 9.0 1.17 16 50 <18 1.24Range 6.6–11.8 0.43–2.26 5–75 30–172 <10–71 0.46–2.51

Drin A1RV2(near L Shkodra)

Average 8.6 4.60 16.3 37.75 36 4.65Median 8.6 1.465 16.3 35.25 31 1.52Range 2–12 0.035–12 1–65 10–80 9–90 0.046–12.2

Vjose A1RV20(near mouth)

Average 8.9 1.71 63.8 44.3 29.1 1.82Median 8.9 1.67 14.3 51.5 28.9 1.73Range 6.1–10.4 0.01–6.8 1–1200 12–210 12–75 0.02–8.21

Kamchia 28 066(near mouth)

Average 7.15 1.23 49.5 737.7 337.5 2.02Median 7.56 1.03 44.1 484.5 1.55Range 4.6–8.5 0.65–2.81 21.3–107 124–1480 0.80–4.40

Neretva 40 159(near mouth)

Average 9.78 0.62 5.7 37 28.4667 0.66Median 9.9 0.59 39 28 26.6667 0.66Range 5.1–12.1 0.27–1.01 2.5–20 5–160 0.005–0.08 0.28–1.19

HMRDF: Hellenic Ministry of Rural Development and Food, HME: Hellenic Ministry for the Environment, Physical Planning and Public Works.

* P–PO4.

These rivers, along with Aliakmon, Neretva, Vjose, Drin andPinios, belong to a ‘high’ quality class concerning TP. Stry-mon and Nestos have ‘good’ TP status, Kamchia ‘poor’ andEvros with Axios a ‘bad’ status. The organic fraction of TPcomprises 62% in Acheloos, 50% in the upper Aliakmon,54% in the upper Drin and 51% in the Axios (Greece)(Voutsa et al. 2001; Ovezikoglou et al. 2003; Borgvanget al. 2006). In the lower parts of the Acheloos, Aliakmon,Neretva andDrin, the organic P fraction ranges between 57%and 75%, indicating organic inputs of upstream reservoirs,while the high portion in Evros (70%) is attributed to organicpollution.

In general, nutrients exhibit a downstream increase intheir concentrations caused by a respective increase in hu-man pressures with some exceptions due to the contributionof local point pollution sources. A notable exception is theNeretva River, where the TP concentration shows an up-stream increase. Due to municipal wastewater impacts, theDrin tributaries in the area of Lakes Prespa and Ohrid showrelatively high nutrient concentrations tending towards a‘moderate’ quality. In addition, Lake Ohrid is being enrichedwith nutrients through underground inputs from Lake Prespa(ILEK 2005). Further downstream near the mouth, ammoniaand nitrite levels decline while nitrate and phosphate in-crease (Borgvang et al. 2006) indicating impact of inorganicfertilizers. The headwaters of Aoos show very low DINand P–PO4 levels of 0.03 mg/L and 5 mg/L, respectively(Chatzinikolaou et al. 2007). Upstream and midway sec-tions, along with the Drino and Shushica tributaries, anddespite a 10-fold DIN and a 3-fold TP increase relative toheadwaters, maintain a ‘high’ quality. Kamchia has a rela-tive degradation in quality downstream of Preslav with fur-ther increases downstream of Shumen, while the inflow ofLuda Kamchia upgrades its quality.

In rivers entering Greece from Bulgaria and FYR Mace-donia, there is a steep increase in nitrate concentration, alongwith a respective decrease in ammonia concentration (e.g.Evros, Nestos and Strymon). Nitrate-pollution sources be-tween the border stations are insignificant, and because it isunlikely that ammonia nitrification alone can account for the

observed differences it seems probable that different techni-ques and methodologies are employed in the different states.In the Evros, below Kostenec, nutrient quality turnsgradually to ‘bad’. DIN levels at the Bulgarian part rangebetween 0.28 (near the source, i.e. upstream of Kostenec)and 6.1 mg/L (below Dimitrovgrad), while P–PO4 levelsrange between 10 (near the source) and 410 mg/L (belowHarmanli). Ammonia reaches high levels, with maximumconcentrations below Dimitrovgrad (1.56 mg/L N–NH4)and Harmanli (1.32 mg/L N–NH4), indicating municipalwastewater discharge. At the delta, autumn flushing causeshigh nutrient concentrations (N–NO3 exceeds 4 mg/L andP–PO4 almost reaches 700 mg/L) (Angelidis & Athanasiadis1995), indicating agricultural impacts. In Tundja, ‘poor’ to‘bad’ nutrient quality prevails. At its downstream section,below the industrial city Jambol, aquatic quality deteriorates.It improves slightly downstream Elhovo and even more be-fore entering the Evros, although retaining ‘bad’ quality. Inthe Arda, nutrient quality ranges between ‘good’ and‘moderate’. In the Bulgarian part of Nestos, ‘moderate’quality prevails. Nitrate and phosphate levels decrease alongthe Greek stretch and, as a result of agricultural impacts, theyincrease again in the delta area. The quality of Strymon,below the Pchelina reservoir, in general presents ‘poor’ nu-trient status (EIONET, Voutsa et al. 2001), while in theBulgarian portion ‘bad’ TP quality dominates. The Axiosshows also an exceptional spatial pattern, with nutrientmaxima at its mid-reach, due to point source pollution fromthe towns of Skopje (organic chemical plant, municipalwastes) and especially Veles (fertilizer industry, municipalwastes), where average N–NH4 reaches 10.9 mg/L and TP16 mg/L. Downstream and along the Greek stretch, waterquality improves due to a reduction of point sources, exceptnitrate which increases as a result of intense agriculturalactivities.

The Aliakmon headwaters and mountainous tributariesshow ‘high’ nutrient status. Along the main stem, nutrientquality ranges between ‘good’ and ‘moderate’ status, whilethe Lake Kastoria canal has a ‘bad’ status (Skoulikidis et al.2002a). Within T66 and downstream of its confluence to theriver, the nutrient quality turns to ‘bad’ (DIN 4.9 mg/L, TP630 mg/L; Voutsa et al. 2001). Along the Pinios main stem,‘bad’ nitrate and ‘poor’ phosphate quality predominate,while tributaries show ‘bad’ nitrate quality and ‘good’ to‘moderate’ phosphate quality (data: Stamatis 1999, Fytianoset al. 2002). In its upper and midway portions, the Acheloosshows ‘high’ nutrient status (data: Ovezikoglou et al. 2003),while the lower part shows ‘good’ quality for N-compoundsand ‘high’ quality for phosphate (Skoulikidis et al. 2002b).Along the Sperchios, nutrient levels range between ‘good’and ‘moderate’ status (data: Dassenakis et al. 2005). Nutrientlevels along theAlfeios indicate ‘good’ to ‘high’ quality. Thetributaries (Elisson, Lousios and Ladon) are of ‘high’ status.Aquatic quality slightly deteriorates below Megalopolis toimprove again downstream (data: Skoulikidis et al. 2000).In the Evrotas, there is a downstream deterioration of N-

FIGURE 11.5 Average nutrient concentrations of Balkan Rivers.

compounds from ‘good’ to ‘moderate’ status, whereas aquality improvement at the mouth is attributed to dilutiondue to karstic inflows. Concerning P constituents, the rivershows ‘high quality’ (Nikolaidis et al. 2006).

In general, Balkan rivers are enriched with nitrate inwinter (December–February) as a result of arable land flush-ing (in the Aliakmon mainly in autumn), while dilutionduring spring and insignificant nitrate point discharges insummer keep nitrate concentrations low (Skoulikidis &Kondylakis 1997). Some rivers (e.g. Evros, Strymon andAliakmon) show an increase in nitrate concentration withdischarge, indicating the prevalence of flushing processes,while others (e.g. Axios, Nestos, Acheloos) show a decreas-ing trend with discharge, indicating the prevalence of dilu-tion processes (see Figure 11.4). TP exhibits maximumlevels at the rising limb of the hydrograph (mainly October,for Pinios in November) due to initial flushing. Ammoniapeaks that occur in winter or spring may be attributed toorganic matter mineralization. Increased TP and ammonialevels during low flow originate from municipal and indus-trial (e.g. seasonal food processing industries) effluents, al-though prevalence of denitrification processes (e.g. in thePinios by standing waters) cannot be excluded.

Regarding long-term nutrient variation (Figure 11.6),during the initial period of measurements, the Evros, Nestos,Strymon and Axios show a gradual increase in nitrate con-centration reflecting agricultural intensification. In the dryperiod (end of the 1980s – beginning of the 1990s), all fourrivers show a concentration increase. In the Evros, a decreas-ing trend is evident after 1991. In the Nestos, Strymon andAxios, after a decrease in the mid-1990s, nitrate increasedagain to reach the multi-year maximum in 1997–1998 and

since then gradually diminished. The Kamchia shows peaknitrate values in 1997 and 2001. The Evros, Nestos, Strymonand Axios show maximum TP concentration in 1982. In theEvros and Axios, a second peak appears in 1990 that coin-cides with minimum discharge. After 1982, TP shows a cleardecrease in the Nestos, a slight decrease in the Strymon, anincrease in the Axios and no clear trend in the Evros. In theKamchia, TP concentration increased in 1995–1997 andthereafter gradually decreased, with a peak in 2001, beingalso evident in the Neretva.

According to the Directive 75/440/EC regarding thequality of drinking waters, the Aoos, Arachthos, Acheloos,Alfeios, Evrotas, Strymon, Nestos and Lakes Prespa andDoirani satisfy the conditions for their classification at A1class. The Pinios, despite occasionally high nitrate and phos-phorous concentrations, satisfies the conditions for its clas-sification as A2 category, while the Aliakmon marginallymeets drinking water criteria. The Axios generally satisfiesthe Directive’s conditions, despite occasional high nitrate,ammonia and phosphorous concentrations, while the Evrosis marginally classified as A3 category (HME 2006). Theother Balkan countries apply national criteria concern-ing water quality for different uses (drinking, swimming,recreation).

The pollution of Greek rivers from compounds of List IIreferred to in Directive 76/464/EC, and other toxic com-pounds, shows low concentrations of VOCs and insecticides,whereas the concentrations of herbicides and metals gener-ally range around moderate levels. Elevated concentrationsoccur in a number of cases due to a variety of factors includ-ing intense agricultural applications, meteorological events,industrial effluents, mining activity and the geochemicalbackground (Lekkas et al. 2004). Regarding pesticides, themost polluted rivers are the Axios andAliakmon. S-triazines,amide herbicides and organophosphorous insecticides arethe most frequently detected, while organochlorine pesti-cides (banned in Greece in 1972) occur at very low concen-trations (Konstantinou et al. 2006). The highest levels oforganochlorines, occasionally exceeding the EC qualitativestandards (Directive 76/464/EC), were detected in trans-boundary water bodies, especially near the borders (Evros,Nestos, Strymon, Axios, Small Prespa, Doirani) denotingtransboundary pollution (Golfinopoulos et al. 2003; Lekkaset al. 2004; Konstantinou et al. 2006). In Axios, lindane(phased out in Greece since 2002, according to Directive2000/801/EC) was detected in 100% of the samples at theentrance of the river to Greece, demonstrating the impact oflindane manufacturing in Skopje (Konstantinou et al. 2006).Concerning insecticides, methyl parathion, parathion (with-drawn since 2003 and not found in recent investigations) anddiazinonwere compounds previously detected inmost Greekrivers, followed by fenthion, carbofuran and malathion. Thehighest insecticide levels were recorded for the Axios (upto 2000 ng/L for malathion, parathion and pyrazophos,362 ng/L for parathion methyl and 7300 ng/L for carbo-furan), while fenthion’s maximum was observed in Evrotas

FIGURE 11.6 Long-term variation of nutrient concentrations in selectedBalkan Rivers.

(Konstantinou et al. 2006). Several organophosphorousinsecticides were detected, mainly in the Evros, Nestos,Strymon, Aliakmon, Acheloos, Pinios, Alfeios and LakePrespa. Regarding herbicides, atrazine, simazine (withdrawnin Greece since 2004), metolachlor, alachlor and prometrynewere most frequently detected (Lekkas et al. 2004; Konstan-tinou et al. 2006). The highest concentrations of simazine(117 ng/L) and cyanazine (63 ng/L) were found in Strymon(Lekkas et al. 2004), of prometryne in Aliakmon (6100 ng/L)and of propanil in Axios (20 600 ng/L) (Konstantinou et al.2006). Captafol, captan, chlorothalonil, metalaxyl, flutriafoland vinclozolin were the fungicides found in the Axios,Aliakmon, Nestos and Evrotas (Konstantinou et al. 2006).VOCs exhibit low concentrations, with higher levels andgreater variety detected in the Axios and Stymon.Hexachlorobutadiene exceeded the quality target level(0.1 mg/L) in the Axios, Strymon, Nestos and Pinios. Inthe transboundary rivers, a number of VOCs presented ele-vated concentrations near the border (e.g. 4-chlorotolueneand napthalene in Strymon, 1,1,2-trichloroethane in Nestos)denoting transboundary pollution, while others(e.g. 1,3-dichlorobenzene in Strymon) were attributed toGreek sources (Nikolaou et al. 2002). Despite the high geo-chemical background, riverine heavy metal levels (for worldaverages seeSalbu&Steinnes1995) aregenerally low(Lekkasetal. 2004).According toLekkas etal. (2004), thehighest toxicmetal concentrations are present in the Strymon (6.39 mg/LAs), Evros (9.17 mg/L Pb; world average 1 mg/L), Axios(43.6 mg/L Zn; world average 30 mg/L, 1.15 mg/L Al), Pinios(40.3 mg/L Cr, 51.1 mg/L Ni; world average 2.2 mg/L,5.35 mg/L Co, 23.7 mg/L Cu; world average 10 mg/L) andL. Doirani, which generally shows elevated geogenic heavymetal concentrations, especially for As (51.5 mg/L). TheAlfeios has high Fe and Mn levels (5.7 and 0.26 mg/L,respectively). Finally, Cd concentration distribution in coresediments of the Axios and Aliakmon reveal high anthro-pogenic flux in recent decades (Samanidou et al. 1991).

11.7. RIPARIAN AND AQUATICBIODIVERSITY

11.7.1. Riparian Vegetation

Mountainous areas still contain surprisingly undisturbed andoften isolated river valleys, in particular close to politicalborders. Western tributaries of the Evros are covered byclosed mixed and deciduous forests (e.g. eastern slopes ofthe Rhodope Mts along the border of Greece and Bulgaria).They are often a ‘secondary wilderness’ as a result of recentdepopulation and cultural abandonment and provide species-rich riparian habitats including residual alluvial alder forests(Alnion glutinoso-incane) and the rare willow Salix xanthi-cola listed by Greece’s Red Data Book (Phitos et al. 1995).

The rivers in the western and southern peninsula oftenhave similar but structurally varied montane riparian vege-

tation. For example the Aoos headwaters drain a uniqueplateau (�1400 m asl) in the northern Pindos Mts that hasbeen used for centuries as the summer grazing area by theVlach shepherds. There, the riparian vegetation is disturbedby grazing forming scattered scrublands with willows andforbs as well as humid montane grasslands. All other head-water tributaries are steep and often colonized by Black Pineforests down to the edge of streams. Further downstreamalong the river valleys, Mediterranean mountain vegetationdevelops. Platanus orientalis is the most ubiquitous treespecies along Balkan rivers, especially in the western andsouthern peninsula. In the Acheloos, the tree begins formingstands at about 1100 m elevation and continues along thelength of the river until its delta in the Ionian Sea. In opendepositional reaches, thickets of Salix eleagnus are charac-teristic throughout the western Balkans (Figure 11.7).

The Upper tributaries of the Arachthos drain flysch bad-lands where landslides are frequent. These badlands createunique riparian zones with narrow wooded strips of OrientalPlane, alders and willows. The 30 km long Arachthos Gorgeprovides another spectacular area with high forest diversityincluding remarkable sclerophyll woods of holm oak; and,locally Laurel Laurus nobilis forms thickets beneath ancientOriental Plane stands. In the southeastern Peloponnese, forexample along the Evrotas River, many headwater streamsare ephemeral or intermittent and fringed by open and linearriparian vegetation. The ubiquitous Oriental Plane is a long-rooted phryatophyte that reaches the groundwater table evenduring the long dry summer.

11.7.2. Lowland Riparian Woods

Today, natural lowland riparian forests are rare in the Bal-kans and they are among the most threatened natural wood-land types. Traditionally, wood cutting for rural and household use was intense along rivers, and is still commonlypracticed in Albania. Only few lowland sections have es-caped widespread degradation. Extensive riparian forests arerare and localized, one such remnant exists along the lowerKamchia. Along the Evros, intact riparian forests, includingpoplar-willow stands and small riverine wetlands that serveas refuges for the riparian flora and wildlife, remain alongthe Greek-Turkish border. One of the most famous lowlandriparian hardwood forests in the Balkans is in the Nestosdelta, the so-called Kotza Orman (Gerakis et al. 2007). Inthe western Balkans important lowland forests are presentalong Lake Shkodra and at Fraxos in the Acheloos Delta.However, in most areas hardwood hygrophilous woods withash or oak are extremely rare and often only small plots ofsurviving trees remain.

Overall, the proportion of alien riparian plant communi-ties is lower in the Balkans than in Western Europe andWestern Mediterranean (Zogaris et al. 2006). Some formerlowland riparian forests in the southern Balkans (e.g. lowerAlfeios and some Evrotas tributaries) have been replaced by

Eucalypt plantations. In the northern and central Balkans,hybrid poplar plantations and species such as Robinia pseu-dacacia, Amorpha fruticosa are now widespread. The Tree-of-Heaven Ailianthus altissima is also a widespread alienspecies in the proximity to settlements in lowland areas. Inlowland areas, the invasive Giant Reed Cane Arundo donaxcovers disturbed and deforested streams and canals. Thesedense bamboo-like thickets impede the regeneration of wil-low and other riparian plants.

11.7.3. Deltaic Communities

The extensiveBalkan river deltas are famous for their diverseplant communities (Szijj 1981). Plant richness can be up to300 to 400 species per delta (Sarika et al. 2005). The deltas ofthe Eastern Balkan are the richest because they containelements from Asia or Eastern Europe (e.g. Iris orientalisin the Evros delta). Most rare species have a circum-Medi-terranean distribution but are often constrained to certainfreshwater wetland types. Sedge habitats, freshwater poolsand wet grasslands are of outstanding local conservationimportance. Species listed as vulnerable, such as Trapanatans, are found in lentic waters of the Lakes Prespa andKerkini. Even formerly widespread species are today eitherpatchy or local in their distribution and frequently listed asthreatened (e.g. Isoetes histrix in Lake Prespa,Cladium mar-iscus in the Arachthos Delta and Ludwigia palustris in theNeretva and Acheloos Deltas).

The large western Balkan deltas share similar landscapefeatures (Koumpli-Sovantzi 1983; Sarika et al. 2005). Thedeltas are bounded by limestone hills, islets and large lagoonswith barrier spits along the shore. Rich hydrophyte commu-nities including Potamogeton spp., Myriophyllum spp.,Polygonum sp. and helophytes (extensive reeds of Pragmitesaustralis, Scirpus spp., Carex spp. and Typha spp.) cover themain river channel. Complex riparian galleries (Salix spp.,

Populus spp., Ulmus minor, P. orientalis, Fraxinus sp.) fringethe deltas. Deciduous scrubs, such as Tamarix spp., coverbrackish coastal lagoons while Chaste Trees (Vitex agnus-castus) prevail along inland freshwater wetlands. Halophilousdwarf scrubs (Salicornia spp., Arthrocnemum spp., Halocne-mum spp.) often form extensive steppes in river mouths andcoastal saltmarshes. Along sandy shores, ammophilous asso-ciations form shifting dunes colonized by Ammophia are-naria, Agropyrum mediterraneum, Cakile maritime and arefringed by pine forests and juniper thickets. In shallow coastalareas, marine angiosperms such as Zostera and Cymodoceaand the Neptune Grass Posidonia oceanica (in clear waters)form extensive sea meadows. The eastern Balkan deltas aregeomorphologically more diverse. A unique formation is theestuarine mudflats in the Sperchios delta, the largest in theentire Aegean.

11.7.4. Ichthyofauna

The Balkan Peninsula hosts a rich freshwater ichthyofaunawith a high proportion of endemic species. It is considered asone of the world’s biodiversity hotspots (Peter 2006). Thenumber of freshwater fishes is the highest in Europe,although estimates of richness vary. The Croatian riversflowing to the Adriatic Sea host 88 species (Radovic et al.2006). More than 135 species have been reported fromGreece (Bobori & Economidis 2006). This number will fur-ther increase, because the taxonomy of many groups is underrevision and new endemic species are still being discovered(Kottelat 1997). Out of 198 known Balkan fish species, 81are listed as threatened or endangered by IUCN. Many of themore restricted species are declining in number.

An even larger and yet poorly explored diversity exists atthe subspecies level with unique phenotypes and genetic pro-files (for salmonids: see Apostolidis et al. 1997; Bernatchez2001; Snoj et al. 2002). The high level of endemism is a result

FIGURE 11.7 Natural longitudinal distribution of key riparian tree species along the Acheloos and Alfeios Rivers,Western Greece. The lower-middle andlower courses contain diverse hydrophilous tree communities because of extensive floodplain development and the presence of karstic springs that createperennial wetlands. Note, the extensive longitudinal dominance of the Oriental Plane (Platanus orientalis).

of the complex geological history of the area in combinationwith distinct environmental gradients as well as past climaticchanges. Awell-accepted hypothesis of the origin and diver-sity of the Balkan ichthyofauna postulates that the Euro-Siber-ian and Palaearctic species colonized the area during theOligocene and Miocene through river captures. The Alpineorogeny and the uplift of the Balkan Mts gradually isolatedthis area from the rest of Europe and additionally cut connec-tions between the eastern and western Balkan drainages(Economidis & Banarescu 1991). Another hypothesisexplains the colonization of freshwater species around thecircum-Mediterranean during a short period in the late Mio-cene, when theMediterranean dried and thenwas refilled withfreshwater entering from the Paratethys (Bianco 1990). In anycase, the area retains elements of the ancestral Europeanichthyofauna that were lost inmost other parts of the continentduring the Pleistocene glaciations.

From an ichthyogeographical perspective, two majordivisions are recognized in the Balkans: the Ponto-Caspianand the Western Balkan. These divisions are biogeographi-cally distinct because mountain boundaries form old barriersto fish dispersal. The Western Balkan rivers are dominatedby relatively depauperate but endemic-rich assemblages thathave experienced long periods of isolation. The rivers of thePonto-Caspian division are more species-rich because manyfish of Black Sea and Danubian origin intruded into this areaduring the Pliocene and Pleistocene when the Black Sea stillwas a freshwater lake. Opinions differ over the existenceand delineation of additional freshwater biogeographic divi-sions and subdivisions (e.g. Bianco 1990; Economidis &Banarescu 1991; Stephanidis 1939; Maurakis et al. 2001).Economidis & Banarescu (1991) distinguished four mainichtyogeographic divisions: the Ponto-Aegean (with the sub-divisions of Eastern Bulgaria, Thracian-East Macedonia andMacedonia–Thessaly), the Attiko–Beotia, the Dalmatianand the South Adriatic–Ionian divisions (Table 11.5). Thesedivisions account for the long-term isolation of the Ionianfrom the Adriatic drainages as reflected by the presence ofunique species endemic to both areas.

The Ponto-Aegean division includes rivers flowing intothe Black and Aegean Seas down to the Pinios River. TheEast Bulgarian subdivision, with its distinct influence from

the Danubian and central European fauna, contains no en-demic freshwater species, although there are brackish andanadromous species endemic to the Black Sea (Neogobius,Alosa spp). The ichthyofauna of the Kamchia includes spe-cies typical of the Danubian ichthyofauna (e.g. Aspiusaspius, Squalius cephalus, Petroleuciscus borysthenicus,Barbus barbus, Chalcalburnus chalcoides, Gobiogobio, Alburnus alburnus and Alburnoides bipunctatus; seeKarapetkova et al. 1993; Vassilev 1999).

The Thracian-East Macedonian subdivision includes the32 native fish species in the Evros and 36 in the Strymon(Table 11.1). It is postulated that their fish fauna entered fromthe Black Sea during its freshwater phase in the Pleistocene(Economidis & Banarescu 1991). Few taxa with Anatolian-Asian affinities are represented by endemic species or sub-species: Cobitis strumicae, Barbatula bureschi and B. cyclo-lepis (with the endemic subspecies B. c. cyclolepis in theEvros and B.c. strumicae in the Nestos and Strymon). Thereare few local endemic species such as Cobitis punctilineata(Strymon) and Squalius orpheus (Evros River).

The fishes of the Western Macedonia–Thessaly subdivi-sion belong to the Danubian faunistic complex and are mostlikely have colonized the area through a postulated Plio-cene–Pleistocene river capture involving the Axios andMor-ava (Danube River tributary) (Economidis & Banarescu1991). Fishes shared with the Danube basin include A.bipunctatus, A. alburnus, Rutilus rutilus, G. gobio, Gaster-osteus aculeatus and Silurus glanis. A number of other fishesstemming from Danubian lineages have evolved endemicforms (Barbus macedonicus, Cobitis vardarensis, Gobiobanarescui, Romanogobio elimeius, Pachychilon macedoni-cum, Chondrostoma vardarense, Vimba melanops, Squaliusvardarensis and Zingel balcanicus).

The rivers of mainland portion of the Attiko-Beotia di-vision contain a depauperate freshwater fish fauna with dis-tinctive endemics (e.g. Barbus graecus, Pseudophoxinusmarathonicus) (Economidis 1995). The Sperchios Rivercontains the locally endemic species P. hellenicus, confinedto spring-fed wetlands of alluvial floodplains.

The Western Balkan division drainages have remainedisolated perhaps since the Miocene and are inhabited mostlyby endemics. The Dalmatia subdivision encompasses a

TABLE 11.5Main ichthyogeographic divisions and subdivisions in the Balkans (in bold: rivers described in this book)

Main divisions Subdivisions River catchments

Ponto-Aegean East Bulgaria Kamchia, Ropotamo, Rezubtska, Veleka, MandraThracian – East Macedonia Evros, Nestos, Strymon, Filiouris, Loutros, Marmaras, Vospos, Kosinthos, KompsatosWest Macedonia – Thessaly Axios, Aliakmon, Pinios (Thess.), Gallikos, Loudias, Sourporema

Attico–Beotia Sperchios, Kifissos, Assopos (mainland only)

West Balkans Dalmatian Neretva, Mirna, Lika, Zrmanja, Krka, Cetina, SocaAdriatic Drin, Aoos (Vjose), Seman, Skumbi, Erzen, Ishmi, Matia, BunaIonian Acheloos, Arachthos, Alfeios, Evrotas, Thyamis, Acheron, Louros,

Krathis, Foinix, Piros, Mornos, Evinos, Pinios (Pelop.), Pamissos, Neda, Peristras, Velikas

number of small and medium-sized rivers that drain Slove-nia, Croatia, Bosnia and Herzegovina and parts of Montene-gro. The shallow northern Adriatic Sea most likely driedduring the last glacial maximum and several rivers hadjoined confluence allowing a faunal exchange among riversof the Northern Adriatic and the Italian coast. In the Neretva,this group of fishes include the cyprinids Chondrostomaknerii, Squalius microlepis, Squalius svallize, Phoxinellusadspersus and Rutilus basak, the salmonids Salmo marmor-atus and Salmo (Salmothymus) obtusirostris, the gobiid Kni-powitschia croatica and the lamprey Lethenteron zanandreai(see Mrakov�ci�c et al. 1995, 2002; Brigic et al. 2004). Tworecently described species (Phoxinellus pseudalepidotus(Bogutskaya & Zupancic 2003) and Knipowitschia radovici(Kovacic 2005)) are endemics to the Neretva. Characteristicsfor the Dalmatian ichthyofauna are the high degree of diver-sification within the genus Phoxinellus (Bogutskaya &Zupancic 2003) and the existence of high morphologicaland genetic diversification among salmonid taxa (Glamuzina& Bartulovic 2006).

The Adriatic and Ionian subdivisions were considered byEconomidis & Banarescu (1991) to comprise a singleichthyogeographic region (the Southern Adriatic–Ionian Di-vision). However, Bianco (1986) argued convincingly thatthe Adriatic and Ionian drainages host different fish faunasand proposed their separation. The Adriatic subdivision,delineated to the north by the Drin and to the south by theAoos, is rich in endemic fishes (for faunistic descriptions seeSpirkovski 2003; Crivelli et al. 1997; Rakaj & Floko 1995).The Drin river system alone (including the associated LakesOhrid, Prespa and Skadar) contains more than 30 endemicfreshwater fish species. Lakes Ohrid and Prespa are geolog-ically old (Plio-Pleistocene) and as such they accommodateseveral local endemic species and subspecies (Ohrid: Salmo(Salmothymus) (Acantholingua) ohridanus, S. letnica,Pseudophoxinus minutes and Rutilus ohridanus; Prespa:Chalcalburnus belvica, Chondrostoma prespense, Barbusprespensis, Cobitis meridionalis, Phoxinellus prespensisand Rutilus prespensis). Two additional species endemic tothe Drin have been recently described: Scardinius knezevici(Bianco & Kottelat 2005) and Eudontomyzon stankokara-mani (Holcik & Soric 2004). Two Dalmatian salmonids arealso found in the Drin: S. marmoratus and S. obtusirostris.

The Ionian subdivision encompasses the drainages be-tween the Thyamis and Evrotas and represents a long-termisolated area with a high proportion of endemic species(Economou et al. 1999). Two genera containing two specieseach are endemic to the Ionian drainages (Tropidophoxinel-lus and Economidichthys). Danubian and European generatypically present in other Balkan regions are absent (e.g.Chalcalburnus, Chondrostoma, Barbatula, Gobio, Albur-nus, Alburnoides, Phoxinus, Cottus and Rhodeus). TheAcheloos contains 22 native fishes including many lacus-trine and fluvio-lacustrine forms that have probably des-cended from morphotypes inhabiting the ancient lakeAetoloacarnania. Six species of the Acheloos are locally

endemic (Scardinius acarnanicus, Rutilus panosi, Silurusaristotelis, Salaria economidisi, Cobitis trichonica andEconomidichthys trichonis) and eight species are endemicto the Ionian subdivision (Barbus albanicus, Tropidophox-inellus hellenicus, Pseudophoxinus stymphalicus, Barbuspeloponnesius, Squalius peloponnensis, Economidichthyspygmaeus, Telestes pleurobipunctatus and Valencia letour-neuxi). The Evrotas in the south has a depauperate native fishfauna (four species) with three species endemic locally or tosouthern Peloponnese (Squalius keadicus, Pseudophoxinuslaconicus and Tropidophoxinellus spartiaticus).

11.7.5. Macroinvertebrates

For most Balkan rivers, the taxonomy and distribution ofbenthic macroinvertebrates have been poorly documented.In Bulgaria, Serbia and Montenegro their identificationis often possible to the species level although availableinformation is restricted to specific catchments (e.g.Vidinova 2003; Bauernfeind 2003; Maurakis et al. 2004;Vidinova et al. 2006; Petrovic et al. 2006). In Greece,identification at the species level remains difficult dueto lack of appropriate taxonomic keys. As a result, suit-able data to evaluate the state of rare, endangered, orprotected species are often absent. Two riparian butterflyspecies (Lycaena dispar and Apatura metis), listed in theAnnexes of the EU Habitat Directive, are still locallycommon along the Evros, Aoos and other central Balkanrivers. Other freshwater species protected by the Directiveinclude the mussels Margaritifera margaritifera and Uniocrassus.

The benthic fauna is widely used to assess the quality offreshwaters (Ghetti 1997). Thus, many inventories have beencarried out for the southern Balkan rivers (Vourdoumpa1999; Lazaridou-Dimitriadou 2002; Kampa et al. 2002;Iliopoulou-Georgoudaki et al. 2003; Skoulikidis et al.2004; Gritzalis et al., 2006). Ephemeroptera, Plecopteraand Trichoptera (EPT-taxa) are used as sensitive indicatorsfor (organic) pollution. The pristine or slightly pollutedmountainous sections of the Alfeios, Aliakmon, Aoos, aswell as the tributaries Nestos and Strymon are dominatedby the taxa Rhithrogena lisettae, Ecdyonurus spp., Hepta-genia spp., Epeorus spp., Taeniopteryx sp., spp., Habrophle-bia spp., Choroterpes spp., Dinocras spp., Perla spp.,Dictyogenus spp., among many others. In the more degradedlower sections, the diversity and abundance of EPT-taxa isusually much lower. The lower Axios (Kampa et al. 2002),Alfeios (Vourdoumpa 1999), Louros, Arachthos and Evrotasrivers (Gritzalis and Skoulikidis unpublished data) are dom-inated by Baetidae, Caenidae, Nemouridae, Hydropsychi-dae, denoting degradation.

Avifauna and human activities have led to a fast expan-sion of molluscs in Greece. Some gastropods (e.g. Ancylusfluviatilis, Acrolocus lacustris) attain high abundance infast-flowing and macrophyte-free headwaters. Other gas-tropods (e.g. Lymnaea spp., Physa spp.) mostly occur in

middle and lower river sections that are rich in fine sedi-ments and macrophytes. Theodoxus spp., one of the mostabundant genera in the southern Balkans, has been collect-ed along all lowland river types. Bivalvia, such as Pisidiumsp. U. crassus and M. margaritifera, are locally common inlowland sections. For instance, M. margaritifera has beenrecorded in the Acheloos and Aliakmon andUnio spp. occursin large numbers in the Alfeios and Aliakmon (Gritzalis andSkoulikidis unpublished report).

Odonates of the families Aeschnidae (Aeschna spp.,Anax sp., Boyeria sp.), Corduliidae (Somatochlora sp., Cor-dulia sp.) and Libellulidae (Orthretrum sp., Sympetrum sp.,Libellula sp.) are typically found in near-pristine sites. Coe-nagrionidae (Pyrrhosoma sp., Ischnura sp., Enallagma sp.,Coenagrion sp.), Calopterygidae (Calopteryx splendens),Gomphidae (Onychogomphus sp., Gomphus sp., Ophiogom-phus sp.), Lestidae (Lestes sp.) and Platycmenidae (Platyc-nemis spp.) include more tolerant species and therefore arecommon in the middle and lower river sections. Cordulega-ster spp. is a rare species in Greece. Epallage fatime occursonly in the Alfeios and Pinios.

Dipterans of the families Chironomidae and Simulidaeusually inhabit low quality waters. Other Dipteran specieslike Atherix spp. live in areas with good water quality, whilespecies of other families (Dixidae, Limoniidae, Psychodi-dae, Ceratopogonidae, Blephariceridae, Tipulidae, Empidi-dae) appear in low numbers and rarely co-occur in the samesampling site. The most abundant coleopterans belong to thefamilies of Elmidae, Hydrophlidae, Gyrinidae and Dytisci-dae. The Heteroptera (Corixidae, Gerridae, Veliidae andNotonectidae) prefer pool conditions and display toleranceto various pollutants (Karaouzas & Gritzalis 2006). In pol-luted sites, Hirudinea are encountered in large numbers, withrepresentative species belonging to the families of Glossi-phoniidae, Hirudidae and Erpobdellidae. The speciesHirudomedicinalis is rare in the southern Balkans (except in theupper Aliakmon). As detritus feeders, the majority ofOligochaeta are usually found at the lower, and often pollut-ed, river sections.

Among the Crustacea, the Astacidae are a rare groupfound mainly in pristine areas, for example in a tributaryof the Strymon in Greece and in the headwaters of theAoos, where huge numbers of Astacus sp. occur. TheAtyidae and Palaemonidae include typical representativesof the meta- and hypopotamon of Balkan rivers. Theyprefer vegetated habitats and exhibit a higher toleranceto increased salinity. Gammarus spp. (Amphipoda) prefersfast-flowing oxygenated streams, although they are occa-sionally observed in pools. Corophium orientale has beenreported from the Evros Delta (Kevrekidis 2005). Fromobservations in large Greek rivers (Aliakmon and Axios),Asselus spp. and especially Asselus aquaticus (Isopoda)are associated with low flow velocity, low oxygen andorganic pollution. Finally, freshwater crabs of the genusPotamon spp. are common in the Balkans (Maurakis et al.2004; Bechev 2004).

11.7.6. Reptiles and Amphibians

The Balkan river valleys host diverse reptile and amphibianassemblages; species richness benefits from remarkable het-erogeneity of habitat and climatic zones. The Evros River ischaracterized by a transitional fauna between Sub-Mediter-ranean and Mediterranean bioclimates, and its herpetofaunaincludes species from different climatic and biogeographicrealms. Amphibians include the southernmost distribution ofthe fire-bellied frogs Bombina bombina. The lower Evrosvalley hosts one of the westernmost populations of the Ot-toman viper Vipera xanthina. Both Greek and Hermann’stortoises are abundant. During the long warm summer, manyreptiles seek shelter in the humid riparian zones.

The herpetofauna shows a remarkable distinction be-tween the eastern and western parts of the Balkan peninsula(Sotiropoulos 2004). The herpetofauna of the eastern Adria-tic and Ionian coast, including the Peloponnese, includes atleast 10 species endemic to this area (e.g. Albanianfrog Rana shqiperica, Epirus frog R. epiroticus) (Arnold &Ovenden 2002). Many reptiles are listed as protected,although they are locally common (e.g. the two nativesemi-aquatic terrapins are widespread in lowland rivers).The herpetofauna of the Acheloos includes at least 20 spe-cies listed as protected at the national, European, or interna-tional level. Along river corridors, a typical faunal ‘zonation’from upland coldwater species (e.g. Alpine Newts, Fire Sal-amander, Yellow-Bellied Toads and Stream Frog) to lowlandwarm-water species (e.g. Spadefood Toads Pelobates syria-cus) occurs (Bousbouras & Ioannidis 1997).

11.7.7. Birds

Many birds are associated with lowland rivers, riparian habi-tats and wetlands. The headwaters of Balkan rivers host fewobligate aquatic birds, mainly Dippers and Grey wagtails,although mature riparian woodlands are often rich in terres-trial forest birds. The middle river sections, especially areaswith extensive braided channels, contain small populationsof river-breeding species, in particular common sandpiper,little-ringed plover and white and greywagtails. The lowlandreaches are often exceptional rich in waterbirds includingmany obligate wetland birds. Natural river floodplain habi-tats are rare; although areas such as the Louros–Arachthos delta hold remarkable riverine wetlands that hostlarge colonies of breeding cicconiformes and other water-birds. The deltaic systems of the Axios, Drin and Evros stillcontain wide floodplains with islands, bars and river flatsthat provide nesting sites for shorebird and tern colonies.Threatened wetland-associated raptors, such as White-tailedEagle and Lesser-Spotted Eagle, nest in riparian forestsalong larger rivers such as the Evros, Drin, Nestos and thelower Aliakmon.

The deltas of the Kamchia, Evros, Nestos, Acheloos, thedouble-delta area of the Arachthos and Louros, as well as theLakes Kerkini, Shkodra and Prespa contain rich bird faunas

often with more than 300 bird species per site. These sites areof exceptional ornithological importance especially for mi-grating species. For instance, Lake Shkodra is the western-most breeding site of the Dalmatian Pelicans and hosts thesecond largest colony of the Pygmy Cormorants worldwide(UN/EC 2007b). The Evros delta is renowned as an interna-tionally important bird area; its value has often been com-pared to the much larger river deltas of the Danube, Rhoneand Guadalquivir (Makatsch 1959; Handrinos et al. 2005).This international significance is mainly due to its strategicgeographical position along the important migration flywaybetween Europe and Asia. The delta is only 70 km from theDardanelles that forms together with the Bosporus a keymigratory ‘bottleneck’ for millions of birds. The delta is alsoan overwintering area for many species from Russia andScandinavia (Handrinos & Akriotis 1997). Although thenumber of breeding birds has recently declined due to habitatloss and anthropogenic degradation, many rare Europeanspecies still breed including Ruddy Shelduck (Tadorna fer-ruginea) and Spur-winged Plover (Hoplopterus spinosus). Inaddition, the middle sections of the Evros in southern Bul-garia are also extremely important for rare and threatenedbirds. There, Mediterranean species and certain raptors findtheir northernmost distribution or have important local pop-ulation strongholds (Stoychev & Petrova 2003). The Dadia–Lefkimi–Soufli National Park in Greece (lower Evros) isrenowned for a remarkable variety of rare breeding raptors(21 breeding species), including internationally importantpopulations of Eurasian black vulture, griffon vulture, Egyp-tian vulture, white-tailed eagle and lesser-spotted eagle(Petrou 1993).

Monitoring of wintering birds has shown a decline insome large raptors and waterbirds in the Balkans (Tucker& Heath 1994). This includes Lesser-Spotted Eagle, GreatBittern and Waterfowl such as Ferruginous Duck and severalgeese species (Handrinos & Akriotis 1997). Supported bydirect and effective conservation efforts, some birds havemaintained and increased their breeding populations suchas Dalmatian Pelican at Lake Prespa and the Louros–Aracthos delta (Zogaris et al. 2003). Other species such asGreater Flamingo, Great White Egret, Little Egret, GreyHeron and Great Cormorant are recovering or even expand-ing their habitat range. Control of indiscriminate shootingand poaching and the creation of artificial reservoirsmay have assisted their populations (Tucker & Heath 1994;Handrinos & Akriotis 1997). Interestingly, local populationswith expanding populations in parts of Western Europe haveshown a regional decline in some wetland areas of the west-ern Balkans (e.g. White Stork, Bittern, Pygmy Cormorant);therefore, small localized subpopulations may be vulnerableto extirpation in geographically isolated Balkan river valleys.

11.7.8. Mammals

Several large mammals have declined in range and num-bers primarily due to poorly regulated hunting and poach-

ing. However, in upland wilderness pockets, stillwidespread in the Balkans, refugia for large mammalsexist. River-associated mammals are poorly studied andinformation on rare or threatened species is mostly fromprotected areas. In the central Balkans National Park (up-per Evros basin), a remarkable number of bat species,including species that use riparian habitats, has beenrecorded (Ivanova 1998). The area is an important strong-hold for the wolf, a species that locally expanded its rangedue to a decrease in human populations in Mts and remoteregions. The golden jackal Canis aureus occurs along low-land valleys where it finds shelter and prey along rivers andin deltas; it is frequently observed in the Nestos and EvrosDeltas. However, the population of the Arachthos–Lourosdelta was extirpated in the early 1990s (Giannatos et al.2005). The otter is widespread in all major river basins anduses a variety of habitats, even steep montane troutstreams. However, a recent decline has been documentedin lowland Balkan areas. The otter is rare in the highlydegraded middle and lower sections of the Evrotas. TheBalkans host Europe’s largest bear populations outsideRussia, a species that frequently uses riparian areas formigration and feeding. An important brown bear popula-tion survives throughout the Dinaric mountain chain,from Slovenia down to the Pindos Mts in central Greece(Swenson et al. 2000). In some parts, brown bear popula-tions are expanding their range due to the depopulation ofvillages. There is a noticeable recolonization of formerareas in the northern Balkans and along country borders(Mertzanis 1998). Recently, the recolonization of the upperand middle section of the Aliakmon, Acheloos and Ara-chthos by bears has been reported. These long mountainriver valleys may serve as stepping stones for the south-ward expansion of brown bears.

11.8. MANAGEMENT AND CONSERVATION

11.8.1. Economic Importance

Most Balkan rivers are too shallow and steep to be navigablewith large motorized vessels. For example, only the lowersections of the Neretva and Buna are used for trade andcommunication. Agriculture is by far the most importantwater consumer in Greece (89%), FYR Macedonia (80%)and Albania (72%). Agricultural water use accounts for 18%in Croatia, 10% in Bulgaria, but only 0.65% in Bosnia andHerzegovina. Half of the water resources in Croatia andBulgaria (53% and 45%, respectively) supply water for in-dustrial use. Large portions of agricultural land are irrigatedin Albania and Greece (49% and 40%, respectively), com-pared to Bulgaria and FYR Macedonia (18% and 11%, re-spectively) and all other Balkan countries (between 0.2%and 2%) (World Bank 2003). The Evros, Pinios and Kamchiadrain the most intensively cultivated basins (53.4 - 40.6% ofthe basin, Table 11.1). About 60% of the total rice production

and 2/3 of the total mussel production (>30 000 tons/year)of Greece occurs in theAxios Delta and estuary (Karageorgiset al. 2003; Zanou et al. 2005).

In Albania, Croatia, Bosnia, Herzegovina, Serbia andMontenegro, hydroelectricity represents a substantial sourceof power (97%, 62%, 59% and 40%, respectively, of totalenergy production). In FYR Macedonia, the share of hydro-power is about 20%, inGreece andBulgaria 10%.Dams alongthe Drin supply major energy for Albania (about 90%,1350 MW, of total power production;WorldBank2003). Sim-ilarly, Neretva (installed capacity: 1120 MW) is amain energysource for Bosnia andHerzegovina (EIA 2006). InGreece, thetotal annual hydropower production is �3000 MW (PPC2008). Most reservoirs have multipurpose functions (e.g. irri-gation, urban water supply, cooling of thermoelectric plants,aquaculture, recreation). In Greece, around 30% of the usablevolume of reservoirs is allocated for irrigation. Inmost Balkancountries there are major demands for further hydropowerdevelopment, reflecting the expected strong economic growthin this region. There is also the obligation for EU and EU-perspective countries to increase the share of energy fromrenewable resources to the total energy production.

Other economic activities comprise forestry in moun-tainous areas, a declining industry, fisheries in lakes,lagoons and estuaries, ecotourism and cultural tourism,extraction of salt from lagoons and of inert material fromriverbeds. The most important lakes for fisheries areLakes Shkodra (annual production: 950 tons/year), Tri-chonis (500 tons/year), Ohrid (230 tons/year, decliningin recent years), Kerkini (150 tons/year) and Prespa(100 tons/year). It is worth noting that the former KarlaLake (Pinios basin) had an average annual production of1000 tons. In lagoons, many aquatic organisms flourishforming highly productive systems. Migratory euryhalinefishes and shrimps are the most abundant and commer-cially important species. Important lagoons for fisheriesare the Mesolonghi lagoons in the Acheloos Delta (about1400 tons/year) and the Narta lagoon in the Aoos Delta(200–340 tons/year). Salt extraction from the Mesolonghilagoon reaches 120 000 tons/year, �65% of Greece’ssalt production. From Narta lagoon, an additional120 000 tons/year are harvested. Protected areas, wherethe local economy was formerly based on agricultureand forestry, play an increasingly important role for eco-tourism and recreation. For example Lake Ohrid has beendeclared as a mixed cultural/natural heritage site byUNESCO, which stimulated the local tourist market(ILEK 2005). Other protected areas of major tourist in-terest include the Vikos–Aoos and Valia Kalda (Aoos) andthe Pirin (Nestos) forest national parks, the Amvrakikoswetlands (Arachthos–Louros delta) and Lake Kerkini.

11.8.2. Conservation and Restoration

Wars and political instability over the past centuries havecreated difficulties for both conservation and research.

This has inhibited a thorough inventory of species, habitatstypes, conservation areas and conservation resources at theregional level. Hence, freshwater biodiversity patterns re-main poorly documented and the underlying processes arefar from being well understood. The protection of thenatural aquatic heritage is often unsatisfactory and poorlyplanned because the focus has been mainly on forestedlands or sites of outstanding scenic beauty. Greece andBulgaria were the first countries in this region that imple-mented protected forested areas. In Greece, this wasthrough the provision and regulation of the Forest Codeand the law on National Parks. The implementationprocess has been very slow. A major problem remainsthe administrative complexity on issues of nature conser-vation, management and enforcement of legislation.Additional problems arise from institutional ineffective-ness, financial restraints, legal problems, deficiency ofpublic involvement and limited political commitment toconservation (Kassioumis 1990; Handrinos & Akriotis1997).

During the past two decades, interest in inland waterprotection has increased, although the focus was primarilyon lentic systems and selected wetland habitats. Biodiversityconservation, ranging from genetic diversity to landscapes,rarely targets rivers or streams in the Balkans. An exceptionis deltaic wetland areas. In fact, all the larger deltas containprotected areas such as Ramsar Sites, with statutory zonationdesignations. Human and natural factors are often deeplyinterdependent in these complex systems. The coastal lagoonsystems, a priority habitat type for conservation in Europe,are usually exploited as traditional fish farms. Moreover,within the wider area of deltas, there are some unique habi-tats such as karstic ponds (deep cryptic depressions) either inmarshes or in coastal lakes and lagoons, such as those en-countered in the Neretva, Louros–Arachthos and Sperchiosdeltas. In the Sperchios upper delta, for example deep spring-fed ponds host the local endemic Pungitius hellenicus, per-haps the most range-restricted fish in the Balkans. Nonethe-less, there are some upland riverine areas that have beenassigned conservation status. These include some spectacu-lar limestone gorges along the Nestos, Aoos, Arachthos andAlfeios, significant portions of the Axios, the virgin forestsof Pirin (Nestos–Strymon basins) and Sredna Gora Mt(Evros basin) and several other headwater streams in themajor river basins. Quite often, the main river channels arenot included in conservation frameworks, and thus remainvulnerable to alteration.

International treaties and designations have greatlyassisted conservation efforts (UNESCO conservation des-ignations). One of the most important steps in promotingthe conservation of aquatic habitats was the signing of theRamsar Convention for the protection of wetlands. InGreece, there are eight sites in the examined basins (EvrosDelta, Nestos Delta and associated lagoons, Kerkini Lake,Axios–Loudias–Aliakmon Deltas, Lake Small Prespa, theAmvrakikos Gulf including the Arachthos Delta and

Mesolonghi lagoons at Acheloos Delta). In FYR Macedo-nia, there is one site at Lake Large Prespa. Lake Shkodraand River Buna are Ramsar sites in Albania and Montene-gro. The Neretva Delta is also protected by the RamsarConvention with two sites in Croatia and Bosnia and Her-zegovina, respectively. European Union Directives havealso promoted the designation and conservation of pro-tected areas in the Balkan states.

In Greece, widespread identification and inventory of po-tential conservation areas officially begun in the early 1980sand was supported particularly by the Birds Directive (79/409) which uses bird populations and species’ vulnerabilityas criteria for the identification of sites of conservation im-portance. The Habitats Directive (92/43/EEC) for the protec-tion of species and habitats of community interest contributedto the designation of protected areas within the Natura 2000conservation scheme. This is the umbrella EU legislation fornature conservation and drives changes in national legisla-tions, which are currently under reform. Greece has proposed359 sites to be included in the NATURA 2000 protectionnetwork. These include a number of riverine gorges, almostall the major river deltas including associated lagoons, and anumber of lakes that maintain a present or past connectionwith large rivers, such as Lakes Trichonis, Lysimachia,Ozeros, Amvrakia, Kerkini, Prespa and Kastoria. Nationallegislation concerning national parks is in a transitional phaseas the Natura 2000 network expands and new protected areaswith their management bodies are being planned. In Bulgaria,monitoring schemes are better developed than in other Balkancountries, and assistance from the EU has helped importantsite inventory processes. Since the country joined the Euro-pean Union (January 2007), it undertook the obligation tosubmit to the European Commission a list of sites to beincluded in the NATURA 2000 network.

The management of natural areas in the Former YugoslavRepublics is still in a transitional stage. In FYRMacedonia, aforestry corps is responsible for the management of desig-nated protected areas (covering about 7.3% of the land area),but its tasks mainly involve inspections. This country plansto extend the protected area surface area to 12% of its na-tional territory, establishing 250 Protected Areas. In Bosniaand Herzegovina, even though international assistance hashelped to develop the framework of an environmental law,legislation remains incomplete and the management of pro-tected areas is far from being satisfactory. In Montenegro, acomprehensive set of acts devoted to the management ofProtected Areas has not been completed. However, the exist-ing national legislation (the National Parks Law) coversseveral issues of management of the four officially designat-ed National Parks, including Shkodra Lake. Serbia’s pro-tected areas are classified according to the criteriarecommended by the World Conservation Union (WCU),and their management is coordinated by the Ministry ofEnvironment according to national laws. In Albania, theactual management of protected areas and national parks isthe responsibility of the Ministry of Agriculture and Food.

This Ministry intends to reorganize protected areas, group-ing several national parks together and increasing the totalsurface of Protected Areas and National Parks from 165 000hectares to over 449 000 hectares (15.6% of the country’sarea). However, enforcement and monitoring withinAlbania’s protected areas is inadequate, and managementplans do not yet exist for most areas.

11.8.3. Restoration Activities and Potential

Ecological restoration efforts have traditionally concentratedon conservation actions for endangered species and pro-tected area habitat enhancement. Most projects are carriedout at a local scale such as riparian tree planting. EuropeanUnion funding has been instrumental for promoting this typeof active restoration. Between 1992 and 2005, Greecebenefited from 46 LIFE-NATURE projects that in manycases provided small restoration programs, often targetedon wetland restoration. The EU-INTERREG programmeand the EU-Structural Funds have also assisted restorationefforts primarily at the local level and often of demonstrativenature. NGOs, Government Research Institutes, and Univer-sity Departments have been active too, often in coopera-tion with the local and federal Government (Aperghis &Gaethlich 2006). Active river restoration has not been exten-sively implemented and there is a major lack of post evalu-ation or project monitoring (Theocharis et al. 2004). Acurrent large wetland restoration project concerns the partialre-establishment of LakeKarla (Kettunen& ten Brink 2006).Another ongoing project concerns the restoration of 2.8 km2

riparian forests in the Nestos delta. Additional restorationactivities have been undertaken for the Evros riparian forestin Bulgaria and in the Kamchia delta.

11.8.4. Reference Conditions

Establishing reference conditions is important for developingecological quality classification systems according to theWater Framework Directive 2000/60/EC (WFD). Identifyingnatural watercourses is not an easy task in the cultural land-scape of the Balkans because centuries of varied land use andsettlement combined with pollution and widespread hydro-morphological modifications obscure the natural physicaland biogeochemical structure and processes. Balkan land-scapes, as other Mediterranean landscapes, usually show amix of degraded and regenerating biophysical features. Also,temporal rainfall patterns differentially affect aquatic bioticcommunities (Bonada et al. 2007). However, the majority ofthe mountainous parts of Balkan river basins, especiallyalong the country borders, can be considered as minimallydisturbed. These regions are only affected by livestock graz-ing, although the density of roads has increased recently,particularly in Greece. Sporadic ecological quality assess-ment studies carried out in Greece confirm that a number of

headwaters and tributaries in the Nestos, Axios, Aliakmon,Aoos, Acheloos and Alfeios basins satisfy the EU criteriaregarding hydrogeomorphological, chemical and biological(mainly based on macroinvertebrates) reference conditions(Lazaridou-Dimitriadou et al. 2000; Skoulikidis et al. 2002a,2004; Iliopoulou-Georgoudaki et al. 2003; Chatzinikolaouet al. 2007; Economou et al. unpublished data).

11.8.5. EU Water Framework Directive

The water resources in the Balkan Peninsula are temporallyand spatially unevenly distributed among and within coun-tries. Some countries face localized water shortages, whilemost major rivers and lakes are transboundary, creating con-flicts of interest. Almost all Balkan countries face dauntingwater resource challenges because of urgently requiredinvestments in water supply, sanitation, irrigation and hy-droelectricity. At the same time, water quality deteriorates(e.g. Evros, Axios, Kamchia, Drin), water exploitation forirrigation increases (e.g. the Thessaly and Laconian plains),fragmentation by large dams is a major pressure (e.g. Drin,Neretva, Acheloos, Nestos, Aliakmon), flooding remains amajor threat (e.g. Evros, Drin, Aoos, Sperchios, Neretva) anddroughts increasingly exhaust water resources (e.g. Pinios,Evrotas).

With the exception of Greece and Bulgaria, which are EUMember States, all other Balkan countries are in the processof integration. This obliges compliance with EU policies,rules and regulations concerning water, here in particular,with the WFD, which is the basic water management legalinstrument. However, economic, political and structural con-straints impose considerable impediments on the applicationof the EU environmental legislation. Water managementtraditions and approaches differ among countries, reflectingdifferences in political systems, administrative structuresand relevant institutional frameworks.

Greece has adopted the EU water policies and rules in-cluding the WFD. Nevertheless, the application of environ-mental legislation was proved in a number of casesinadequate. Even in protected areas, and despite nationaland international legislation, environmental protection hasbeen often neglected in favour of large-scale developmentprojects. Environmental Impact Assessments have so farbeen applied often in inappropriate and ineffective ways(Handrinos & Akriotis 1997). An outstanding example ofthis is the well-publicized Acheloos Water Transfer, a mega-project which planned to divert a large portion of the watersof the Acheloos (today in a reduced scale of 0.6 km3/year)towards the Pinios basin. This transfer is anticipated to serveirrigation of 2400 km2, drinking water supply, hydropowerproduction and to improve surface and groundwater qualityand quantity of the Thessaly plain. The project has been on-going and has stirred debate and controversy for over 30years; but, study after study, has not convinced courts orthe public that the environmental costs do not significantlyout-way the benefits of this water transfer.

For the other Balkan countries, constraints arise fromlong-standing sectoral planning traditions, heavy invest-ment requirements (e.g. in sanitation and waste treatmentinfrastructure), poor administrative capacities and little ex-perience of dealing with multidisciplinary issues. Addition-al difficulties arise from the deteriorating governmentservices and public infrastructure following severe civilconflicts that recently affected the economies of somecountries. Hence, policies and strategies for water use andmanagement evolved on different principles, reflecting thelong duration of the previous period of central planningculture and practice. In accordance with the prevailing po-litical and administrative structures, management followeda top-down approach based primarily on sectoral planning,in which different sectors and services were separated andhandled by different ministries and agencies. Bulgaria hasjoined the EU very recently (January 2007), and Croatia, asa candidate country, made progress in establishing appro-priate legislative and institutional framework for a decen-tralized integrated management on a river basin districtscale compliant with the demands of the WFD. In the con-stituent republics of the state union Serbia and Montenegrothe water legislation has several shortcomings hamperingthe effective management of water resources including lackof a clear institutional framework (World Bank 2003). InBosnia and Herzegovina, water management is under theauthorities of two entities; the Federation of Bosnia andHerzegovina and Republika Srpska, which have two inde-pendent water laws and organizational structures based ontheWFD. Geopolitical and administrative boundaries in theNeretva basin make the optimal management of the riverbasin, delta and coastal zone complex and difficult. In FYRMacedonia and Albania, despite the adaptation of WFDprinciples in respective water laws, there is a clear lack inimplementing a modern water resource management intoreality (Speck 2006).

The speed of legal and institutional reforms required forthe implementation of the WFD is generally slow in allcountries, including Greece. In Greece and Bulgaria, de-spite the recent elaboration of preliminary River BasinManagement Plans, there is limited progress in implement-ing the Directive, particularly for the assessment and clas-sification of the ecological status of waterbodies(Skoulikidis & Gritzalis 2005; BMEW 2005). Concerningthe management of shared basins, one-sided exploitation ofwater resources and pollution impact by upstream partiescause critical deficiencies of water quantity and quality todownstream countries, including surface and groundwatersand wetlands. The Neretva, Evros, Tundja, Nestos, Stry-mon and Prespa and Doirani Lakes are examples of sharedwaterbodies where such situations are encountered (GWP2005). To face the transboundary nature of water supply andsanitation issues, the Balkan countries adopted the WaterConvention of the United Nations Economic Commissionfor Europe, which entered into force in 1996. The provi-sions of the WFD and the Water Convention include the

design and implementation of joint plans, joint river au-thorities, transboundary river basin units and coordinatednational measures at a basin scale, and provide the platformfor the management of shared water basins between mem-ber states and non EU countries.

However, joint international management is either insuf-ficient or completely missing for the majority of sharedrivers and lakes despite, agreements, protocols and treatiessigned for the rivers Neretva (not fully in power), Drin (be-tween Albania and FYR Macedonia), Aoos, Axios, Evros(between Greece/Bulgaria and Greece/Turkey) and Nestosand for Lakes Shkodra, Ohrid, Prespa and Doirani (GWP2005). In the majority of cases, political obstacles, lack ofresources or inefficient collaboration in a technocratic level(Kallioras et al. 2006) have not allowed proper implementa-tion (GWP 2005). An example of poor transboundary coop-eration is the case of the Evros basin, where major problemsare connected with floods and water quality. Moreover, theAxios basin has been at the heart of numerous conflictsbetween Greece and FYR Macedonia for decades (GWP2005), despite agreements on water management that datesince 1959. In contrast, the case of Prespa Lake is an excel-lent example of how transboundary environmental issues canencourage international cooperation among neighbouringnations (Greece, FYR Macedonia and Albania). Lake Ohridprovides another example of effective measures being takenfor cooperative management of transboundary lakes. More-over, after years of disputes, a bilateral treaty regulating theamount of Nestos water entering Greece has been signed,while cooperation exists between the two countries in theframework of several bilateral research projects (GWP 2005;UNESCO 2006). Overall, the Balkans represent one of themost important areas for potential transboundary coopera-tion in protected area management worldwide. Indeed, atleast 50% of the sites of international importance in theregion are transboundary, including all the large lakesShkodra, Ohrid, Prespa and Doirani, many large rivers andimportant deltas (e.g. Evros River, Buna Delta). Moreover, inthe IUCN Strategic Plan for South Eastern Europe, 37 pri-ority sites have been identified for a transboundary cooper-ation in protected areas development.

11.9. CONCLUSION AND PERSPECTIVE

Driven by active tectonic movements, the Balkan Peninsulais a geomorphologically dynamic region with intensiveerosion and deposition. Dynamic river systems create adistinct longitudinal sequence of steep gradient headwaters,braided and meandering channel types and deltaic areas.Recent hydromorphological alterations (embanking,straightening, reservoir building) have inhibited or reversedthe evolution of deltas and have reduced the recharge ofgroundwater aquifers. On the other hand, unregulated riversections are prone to floods, and widespread deforestationand wildfires enhance erosion. Overexploitation of water

resources for agriculture, in combination with semi-aridconditions and a progressive decline of precipitation dueto climate change, has modified most natural flow regimes.Former perennial rivers are now temporary. In addition,large-scale wetland drainage has caused major hydrologicalmodifications, has degraded water quality, and has led tothe loss of habitats and species. Pollution from municipal,industrial and agrochemical sources remains a major threatto Balkan freshwater ecosystems. Environmental pressuresdiffer among regions; mining effluents affect mainly Bul-garian and Albanian rivers, industrial pollution is importantin Bulgaria, FYR Macedonia and Bosnia and Herzegovina,agricultural pollution is widespread in Greece, Bulgariaand Albania, while urban pollution prevails in all countriesexcept Greece. Today, the aquatic and riparian fauna andflora in many river basins is at risk. Lowland sections are atgreatest risk due to changes in agricultural practices, indus-trialization, tourism and large-scale modifications in head-waters. Environmental decision-making processes areintrinsically complex and require concerns for biodiversityconservation and integrated river basin management. Asound scientific basis is often missing. The WFD demandsa reduction of human impacts to establish a ‘good’ waterstatus, however, at present the Directive is only beingimplemented in Greece and Bulgaria. Overall, there is amajor lack of hydrological and physicochemical data, andin particular of ecological data, that hinders the establish-ment of river basin management plans. The development ofoperational monitoring networks is of pivotal priority. Thesituation becomes even more complex in transboundaryriver basins where the establishment of appropriate admin-istrative and a scientific institutional framework are essen-tial. Efforts should be devoted to standardizing andcalibrating techniques for measuring chemical and ecologi-cal quality among countries sharing river basins. Today,Balkan countries should take advantage of EC and UNassistance in order to efficiently manage, protect and re-store their watercourses.

Acknowledgements

The authors would like to thank their colleagues at the In-stitute of Inland Waters (Hellenic Centre for Marine Re-search), namely Ioannis Karaouzas, Elias Mousoulis,Yorgos Amaxidis, Leonidas Vardakas, Theodora Kouvarda,Argyro Andriopoulou, Maria Koutsodimou and DimitrisKommatas, who supported the entire attempt for the devel-opment of this manuscript. They also whish to thank theCroatian Meteorological & Hydrological Institute, whokindly provided a comprehensive water temperature andlevel time series, as well as Danillo Mrdak from the Univer-sity of Montenegro for assisting in compiling the Drin fishdata. This book chapter was also made possible by projectgrants from the E.U. and the Greek General Secretariat ofResearch & Technology, Ministry of Development.

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Global Runoff Data Centre (GRDC) http://grdc.bafg.de/servlet/is/

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http://www.hydromet.gov.bz/Data_Request.htm Serbia, Republic Hydro-

meteorological Service: http://www.hidmet.sr.gov.yu/eng/osmotreni/

stanje_voda.php.

Bulgaria, National Institute of Meteorology and Hydrology: http://hydro.

meteo.bg/indexen.html Albania, Academy of Science, Institute

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Sediment fluxes

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http://grdc.bafg.de/servlet/is/Entry.987

http://grdc.bafg.de/servlet/is/Entry.987

http://www.grdc.sr.unh.edu/html/Runoff/index.html



http://medhycos.mpl.ird.fr/en/t1.ovei%26gn=ove.inc%26menu=projectimp1st.inc.html




http://www.dei.gr/default.aspx%3Fid=1001%26nt=18%26lang=2




http://www.hydromet.gov.bz/Data_Request.htm

http://www.hidmet.sr.gov.yu/eng/osmotreni/stanje_voda.php

http://www.hidmet.sr.gov.yu/eng/osmotreni/stanje_voda.php

http://hydro.meteo.bg/indexen.html

http://hydro.meteo.bg/indexen.html

http://www.academyofsciences.net/institutes/hydrometereology/

http://www.academyofsciences.net/institutes/hydrometereology/

http://www.fao.org/ag/agl/aglw/sediment/default.asp

http://www.fao.org/ag/agl/aglw/sediment/default.asp

Water quality

European Environment Information and Observation Network (EIONET),

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minagric.gr/en/1.1.html.

Hellenic Ministry for the Environment Physical Planning and Public Works

(HME). http://www.minenv.gr/welcome_en.html.

Hellenic Centre for Marine Research, Institute of Inland Waters (rivers):

http://www.rivernet.gr (in Greek, in English under construction).

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Serbia, Republic Hydrometeorological Service: http://www.hidmet.sr.gov.

yu/eng/osmotreni/kvalitet_voda.php.

Biology

www.fishbase.org

www.ripidurable.eu.

http://www.eionet.europa.eu/

http://www.minagric.gr/en/1.1.html

http://www.minagric.gr/en/1.1.html

http://www.minenv.gr/welcome_en.html

http://www.rivernet.gr/

http://www.lakenet.gr/index_en.php

http://www.hidmet.sr.gov.yu/eng/osmotreni/kvalitet_voda.php

http://www.hidmet.sr.gov.yu/eng/osmotreni/kvalitet_voda.php

http://www.fishbase.org/

http://www.ripidurable.eu/

Documents

Rivers of the Balkans