Water Pollution Control - A Guide to the Use of Water Quality Management Principles Edited by Richard Helmer and Ivanildo Hespanhol Published on behalf of the United Nations Environment Programme, the Water Supply & Sanitation Collaborative Council and the World Health Organization by E. & F. Spon © 1997 WHO/UNEP ISBN 0 419 22910 8 Case Study IX* - The Danube Basin * This case study was prepared by Ilya Natchkov IX.1 Introduction The Danube river basin is the heartland of central and eastern Europe (Figure IX.1). The main river is among the longest (ranked 21) in the world and the second longest in Europe. It has a total length of 2,857 km from its source at a height of 1,078 m in the Black Forest, Germany, to its delta on the Black Sea, Romania. The watershed of the Danube covers 817,000 km2 and drains all or significant parts of Germany, Austria, the Czech Republic, the Slovak Republic, Hungary, Croatia, Slovenia, Bulgaria, Romania, Moldova, Ukraine and parts of the Federal Republics of Yugoslavia, Bosnia and Herzegovina. The watershed represents 8 per cent of the area of Europe (Figure IX.2). Between the source and the delta, the main Danube river falls a total height of 678 m and its character varies, therefore, from a mountain stream to a lowland river. Upstream of the Danube delta the mean flow of the river is about 6,550 m3 s-1 with maximum and minimum discharges of 15,540 m3 s-1 and 1610 m3 s-1 respectively. About 120 rivers flow into the Danube, such as the Tisza and Sava which have their own significant flow. The contribution from the main tributaries is given in Figure IX.3. The mean altitude of the river basin is only 475 m, but the maximum difference in height between the lowland and alpine peaks is over 3,000 m. However the basin can be conveniently divided into an upper, middle and lower region (according to its geological structure and geography), and the Danube delta. The range of mean monthly temperature increases in an easterly direction from 21 °C in Vienna to 23 °C in Budapest and to 26 °C in Bucharest. The average annual precipitation in the Danube river basin varies from 3,000 mm in the high mountains to 400 mm in the delta region. The mean annual evaporation varies between 450 mm and 650 mm in lower regions. Approximately 80 million people are living in the basin (Table IX. 1). The economic conditions vary from the highly developed countries of Germany and Austria, to countries with modest economical and technological possibilities. Most of the countries in the region are in transition after recent political changes and are suffering severe economic and financial constraints. Figure IX.1 Location map showing the countries drained by the Danube river basin IX.2 Economic activities in the basin Throughout the basin, the tributary rivers and the main Danube river provide a vital resource for water supply, sustaining biodiversity, agriculture, industry, fishing, recreation, tourism, power generation and navigation. In addition, the river is an aquatic ecosystem with high economic, social and environmental value. A very large number of dams and reservoirs, dikes, navigation locks and other hydraulic structures have been constructed in the basin to facilitate important water uses; these include over 40 major structures on the main stream of the Danube river. These hydraulic structures have resulted in significant economic benefits but they have also caused, in some cases, significant negative impacts downstream. These impacts include, for example, increased erosion and reduced assimilative capacity where river diversions have resulted in reductions in flow below the minimum required for desired water uses, such as fisheries and maintenance of aquatic ecosystems. Figure IX.2 Detailed map of the catchment area of the Danube river basin Figure IX.3 The contribution made to the total flow of the Danube river by the various tributaries along its length Table IX.1 Area and population data for the countries included in Environmental Programme for Danube river basin1 Country Total Area Danube Population Population Danube Urban area within basin (% (106) in (106) basin (% population (103 (103 of the of the (%) km2) km2) total) total) Germany 356.9 59.60 16.7 80.0 9.00 11.25 Austria 83.9 80.70 96.2 7.42 7.42 100.00 Czech Republic 78.9 22.49 28.5 10.36 2.74 26.45 78 Slovak Republic 49.0 48.68 99.3 5.31 5.10 96.00 78 Hungary 93.0 93.0 100.0 10.60 10.60 100.00 61 Croatia 56.5 33.75 59.7 4.76 3.25 68.30 51 Slovenia 20.25 15.20 75.0 2.00 1.76 87.75 56 Bulgaria 111.0 48.20 43.4 8.80 4.07 46.25 68 Romania 238.0 233.20 98.0 22.76 22.00 96.70 54 Moldova 33.7 8.79 26.1 4.34 0.77 17.60 47 Ukraine 604.0 36.31 6.0 51.70 3.00 5.80 67 Total in the area 679.92 69.7 of EPDRB FR Yugoslavia, 134.25 10.5 Bosnia and Herzegovina Others 2.83 80.2 Total 817.00 1 Some data are estimates because statistics were not available specifically for the Danube river basin The main water uses in the basin are domestic drinking water supply, industry and irrigation. Many water works along the Danube and its tributaries use bank-filtered water. The Nussdorf water works provides about 15 per cent (150,000 m3 d-1) of Vienna's water demand from bank wells. The water supply of Bratislava relies on bank-filtered water (160,000 m3 d-1). In Hungary, most drinking water (90 per cent) actually comes from sub- surface water resources. The total pumped amount is approximately 6,000 × 106 m3 d-1 of which 70 per cent provides public water supplies and 30 per cent is used for irrigation and industrial purposes. In Bulgaria, the total water abstraction from the Danube is 1,142 × 106 m3 a-1 (surface and bank-filtered) of which 70 per cent goes to irrigation, 20 per cent serves industry and 10 per cent provides public water supplies. In the downstream countries the main user is agriculture, which accounts for 85 per cent of total use in Moldova. In upstream countries, such as Slovakia, the main water user is industry (accounting for up to 71 per cent of total surface water withdrawals). Economic activities and land use in this large river basin are very diverse, including numerous large urban centres and a wide range of industrial, agriculture, forestry and mining activities. There are also numerous important natural areas, such as wetlands and flood plain forests. The water resources and the environmental quality of the basin are under great pressure from these activities. Microbiological contamination is evident throughout the river system and is generally due to the discharge of urban wastewater and storm water. Urban and industrial discharges from inadequate waste treatment and disposal facilities also contribute significant quantities of oxygen depleting substances (measured in terms of their biochemical oxygen demand (BOD)). Nutrients from domestic and industrial sources, chemical fertilisers used in agriculture, and manure from intensive and large-scale livestock operations, have leached into the groundwater and into the surface waters and their sediments. The resultant increases in nutrient levels have stimulated eutrophication and degraded the aquatic ecosystem. Water quality for the eight countries of the Danube basin is summarised in Table IX.2. The countries of the middle and lower Danube basin are undergoing a major restructuring and transformation of their political, social, administrative and economic systems. From an environmental perspective, some of the most important changes will be in the industrial sector, where the nearly exclusive emphasis on production in the past resulted in significant pollution and waste of resources. Some institutional changes, such as the decentralisation of management and financial responsibility for water supply and wastewater management to local authorities, are creating opportunities for substantial improvements in water services and in environmental benefits. Table IX.2 Proportion of river network conforming to different water quality classes in eight countries of the Danube basin (according to national classification systems) Water Quality Class Country I II IIIIV V Austria1 23 71 6 0 Bulgaria2 37 22 24 16 1 Czech Republic3 Oxygen regime 0 22 19 36 23 Basic physical and chemical indicators 0 0 0 1 99 Biological and microbiological parameters 4 26 66 4 0 Germany4 Baden Württemberg 17 75 7 Bavaria 8 87 4 Hungary5 31 54 15 Romania6 42 24 24 12 22 Slovakia Oxygen regime 0 22 33 16 29 Basic physical and chemical indicators 0 0 17 27 56 Chemical components 16 26 11 26 21 Biological and microbiological parameters 0 0 13 18 69 Slovenia7 0 5032 12 6 Unless otherwise noted the water quality classification is based on five classes. 1 I & I-II, II & II-III, III & III-IV, IV system for 1992; Source: IUCN, 1994 2 Source: IUCN, 1994 3 Source: Haskoning, 1994 4 I & I-II, II & II-III, III & III-IV, IV system; Source: IUCN, 1994 5 I, II. III system, 1991 figures; Source: IUCN, 1994 6 Source: IUCN, 1994 7 I & I-II, II-III, III-IV, IV system for Drava basin only; Source: Haskoning, 1994 IX.3 The Environmental Programme for the Danube river basin Recognising the growing regional and transboundary character of water resources management and the related environmental problems, the Danube countries (together with the interested members of the international community) met in Sofia in September 1991 to consider a new regional initiative to support and to enhance national activities for the management of the Danube basin.