Dams and the Danube: Lessons from the Environmental Impact

Presentation by Alexander Zinke
at the WCD Forum in Prague (26 March 1999)

1 General Situation of the Danube Basin

The Danube is, after the Volga river in Russia, with 2,780 km the 2nd largest and, truly, the European river. Its flow along or through 10 countries (Germany, Austria, Slovakia, Hungary, Croatia, Federal Republic of Yugoslavia, Bulgaria, Romania, Moldova and Ukraine) makes it the most international river in the world. In a distinct west-east flow orientation, it connects the Black Forest in south-western Germany (as confluence of the two source rivers of Brigach and Breg at Donaueschingen: at only 678 m a.s.l.) with the Black Sea in the remote south-eastern Europe. The entire catchment area of 817,000 km² includes large parts or entire territory of 13 states (in addition Czechia, Slovenia and Bosnia-Herzegovina) and touches in small surfaces another 4 states (CH, I, PL, ALB, FYROM). The Danube has about 300 tributaries of which 30 are navigable. At its delta, the discharge varies from 1,610 m³/s to 15,540 m³/s (average: 6,550 m³/s). The river slope also varies a lot: in the upper reach it is between 1 ‰ and 0,2 ‰, in the middle reach is goes down to 0.06 ‰, through the Carpathians is up again to 0.32 ‰ and then up to the delta it is less than 0.01 ‰.

The basin includes abundant morphological (alpine, mountains, basins / plains and delta), climatic (from atlantic and even sub-mediterranean to continental-steppe) and biological forms (e.g. pannonian, balkan and pontic elements). It is geographically divided into four parts: upper region (source to "Porta Hungarica" at Bratislava), middle region (down to the Iron Gate cross-cutting the Carpathian mountains), the lower region and the delta (divided into three river arms; size: some 5.800 km²).
The biggest tributaries are the Inn (at the Austro-Bavarian border; average discharge 745 m³/s), the Drava (Croatian-Hungarian border, av. 578 m³/s), the Tisza (largest sub-basin with 149,000 km² = 18.5 % of the entire basin; av. 814 m³/s) and the Sava (mouth at Belgrade; av. 1,613 m³/s) - all being of transboundary character.

Most rivers in the basin are already "developed" by ten thousands of dams. Today, only remnants of intact river stretches are left (e.g. the Austrian Lech; the Lower Mura and Drava, the Drina). River engineering works during the last decades have significantly altered the natural flow and sediment regime, especially in mountain stretches of tributaries and at the Iron Gate dams. Furcation and meander zones of the Danube and the tributaries were canalised, resulting in

• interrupted sediment transport and downstream bed deepening,
• changed hydrology
• aggravation of flood hazards,
• reduced self-purification capacities
• blocking of longitudinal and lateral migration patterns and in
• losses in biodiversity

in various parts of the basin.

Unique ecosystems in the basin are the puszta plain, the karst landscape and its underground systems (especially in western Slovenia) as well as large wetlands like the Danube delta and the floodplains on the central Danube (near Vienna, Bratislava and at the mouth with the Drava river; the central Sava river). Biodiversity includes e.g. some 180 bird and 100 fish species, as well as some 2,000 higher plants. However, while large areas are under protection, this gene pool is degrading and many species are threatened with extinction (e.g. German tamarisk, water chestnut; sturgeon family; white-tailed eagle, little ringed plover, pelican; beaver).

The Danube basin is also very diverse in its political, economic and social state. Today's situation is the heritage of the past development politics, with the most decisive periods under the Slavic tribes, the Habsburg monarchy, the centralised communist system and the EU market economy.

As the riverine landscapes are attractive for human settlements and economic activities, they are the most affected and degraded basin parts. Some 83 million people live in the basin (13 countries) with an average 103 people/km²: highest in entire Germany with 162/km², lowest in Bosnia & Herzegovina with 79/km²). The GDP (Gross Domestic Product) varies from US$ 512/capita/year in Moldova to US$ 25,600 /capita/year in Germany.

Clean freshwater is a limited resource in the basin. The average water demand varies between 165 l/capita/day in Hungary to 435 l/cap/day in Bulgaria. 29% (Moldova) to 98% (Bulgaria and Germany) of the population are connected to central water supply systems, losses range from less than 15% (D) to 43% (BG). Individual waste water collection varies from 11% (D) to 86% (MD), in rural areas this share can go beyond 95%, whereas central sewerage systems vary from 14% (MD) to 89% (D). Surface water is abstracted (more than half in Romania) for industry and mining, for agriculture (including irrigation), public water supply and, as the highest use, for energy production (cooling water).

Substantial parts of the population live near water bodies with a quality unsuitable for bathing. Main pollution sources for health hazards are non-existing or inadequate collection and treatment of communal and industrial waste waters (often directly discharged into the rivers). Disposal of solid wastes (often a mixing of municipal with industrial and even hazardous waste) constitutes a particular hazard for aquatic systems and drinking water resources. Agriculture further contributes mainly through diffuse pollution with nitrogen and phosphorus to heavy nutrient loads of river and groundwaters. The political changes after 1989 resulted in reduced pollution loads in the post-communist countries. However, there are still hundreds of hot spots (cities, industry complexes, pig farms) causing locally and further downstream serious environmental problems for man and nature.

2 The Taming of the Rivers

First river works aimed at flood protection (ice flows) and at improving and securing navigation (changing main bed, shallows and rapids). By the end of 19th century, the Danube was severely changed through various river regulation works. In Bavaria, for instance, the 400 km long floodplain section (German section is in total 580 km) was shortened by 21%. Today, less than 25% of the Bavarian Danube are still free flowing.

In Austria, tow paths were built already in the 18th century. Strongest change of the Austrian Danube occured near Vienna in form of a 25 km long new straight channel, built after 1850. Protection works against floods started in Hungary already in the 16th century. Similar activities were undertaken in the Yugoslavian Vojvodina and on the Drava and Sava rivers in the 19th century.

Most dramatic changes have be reported from Hungary where in the 19th and 20th century large-scale drainage of some 3,700,000 ha of permanently or seasonally inundated areas was undertaken. Some 4,000 km of dykes were built, at a total river length of only 2,800 km. Cross-cutting of meanders and other straightening works reduced the length of rivers: at the Danube from 494 km to 417 km, at the Tisza from 1,419 km to 966 km. Subsequently, low water levels went down and high water levels up, increasing flood hazards (e.g. the latest flood on 320,000 ha in northern Hungary in February 1999). River bed erosion is affecting falling water tables and with this the overall soil fertility. It is expected that some 2 million hectares of arable land have soon to be abandoned. Navigation, water supply (mostly through bank-filtered resources) and fisheries also suffer from these impacts.

Intensive networks of dyke lines, drainage and irrigation systems were installed in various lowlands throughout the basin. Most prominent areas are the lower Tisa (Vojvodina) and the lower Danube and the delta. In Bulgaria, some 72,600 ha of floodplain were dyked between 1930 and 1950, and in Romania in the 1960s and '70s, 80% (435,000 km²) of floodplain landscape were disconnected from the lower Danube to intensify agricultural production (agricultural and fish polders). In the delta, the Sulina arm was made navigable for large sea ships between 1857 and 1902, thus shortening its formerly meandering route from 85 km to 62 km).

Navigation is a traditional activity on the Danube and very much supported its economic development. The first tow path was built by roman emperor Trajan at 100 A.D. at the Iron Gate. Intensive works started in 1834 but the dangerous passage through the cataracts ceased with their impoundment over 270 km. In 1972, the Iron Gate I dam (drop of 32 m) was completed, in 1984 the Iron Gate II dam was added.

The first hydrodam was built in 1927 at Vilshofen (lower Bavaria). Hydro-power utilisation varies substantially from country to country (e.g. Hungary 28 MW = 0.6% of power generation, Romania 5,200 MW = 30% of power generation; Austria 14,200 MW: 70%). The totally installed hydropower capacity in the entire basin is in the order of 29,000 MW.

River works altogether are responsible for a loss of some 15-20,000 km² of Danube floodplains. This has led i.a. to a clear worsening of flood peaks which are today arriving faster and higher than before.

3 Environmental Impacts of Danube Basin Dams

Environmental impacts of river dams are well known and studied all over the world. They do not differ a lot from the main problems known for the Danube basin. As the floodplain ecosystem is adopted to survive few months or even years of unfavourable conditions, it seems that the main scientific challenge is to early recognise slow but decisive environmental changes (biodiversity changes, physiological stress) which gradually develop over years until they reach a "point of no return". Main impacts in the Danube basin are:

Excellent example is the upper Danube between the source and Bratislava (the first 1,000 km) with its chain of 58 dams, i.e. in average one dam every 17 km and with only three important free-flowing section left: Straubing-Vilshofen in Bavaria, the Wachau and Vienna-Bratislava. In the early 1980s, these important losses of upper Danube floodplains over the past decades - both in form of the visible changes, personal experience and of information from scientific impact monitoring - have led many concerned people to oppose the continuation of conventional river development. International attention was drawn to the dam conflicts of Hainburg (1984), Gabcikovo-Nagymaros (1988), Bavarian Danube (Straubing-Vilshofen) and the Croatian Danube (Novo Virje). Even more, smaller conflicts occured in Austria in the 1990s (Vienna-Freudenau, Mur, Traun, Lech) because already some 80% of Austria's large rivers are seriously damaged and more than 50% are impacted by hydropower dams, as recent WWF studies show.

Austria (size of 83,800 km²) has a river network of about 100,000 km:
        Total number of dams: many thousand (no figure yet available: alone the province of Salzburg has more than 2,000 dams)
        Total area lost to river regulation over the last 50 years: 400,000 ha and 30,000 km
        Out of 5,265 km of rivers having a catchment over 500 km² (including the Danube):
                        3.7 % pristine
                        17.4 % semi-natural
                        78.9% seriously damaged (canalised and/or dammed by hydropower)
       Impact of hydropower: 50.9% (2.678 km)
                                1.056 km impounded
                                934 km residual flow
                                688 km peak operation
       Affected biodiversity: more than 900 species (223 plants and 668 animals) on red lists.

Hainburg (A)
This dam was planned to complete the Austrian chain of Danube dams up to the Slovak border. Mounting protests peaked in December 1984 in a site occupation by thousands of ordinary citizens which prevented the permitted logging of the dam site. In spite of repeated revival efforts to build this or a similar dam, the continued public opposition eventually forced the establishment of a "Danube floodplain national park" in October 1996. The area of some 10,000 ha is the only large floodplain forest left in the upper Danube. The mosaic of different floodplain biotops and a diversity of some 5,000 animal species led to its nick-name as "Austrian rainforest".
WWF with the help of 120,000 donors has bought in 1989 a core zone of 420 ha where since 1990 model wetland restoration is being implemented together with the Waterways Authority (see table in chapter 4). Embankments, limiting over decades the inflow of river water, were lowered at four sites to stop siltation, to support erosion and to create more open waterbodies and gravel banks. The discharge increase from 5 m³/s to 200 m³/s created one of the most dynamic floodplain areas in central Europe.

Gabcikovo-Nagymaros (SK-H)
This dam project became the best known and most disputed river works in Europe and is subject until today of a bilateral conflict between Slovakia and Hungary at the International Court of Justice in The Hague (NL). Originally planned as a combined dam system allowing peak operation in the Pannonian plain - i.e. a technical experiment in its kind and, as it was shown, with repeated technical failures - it was altered after the stopping of the Nagymaros sub-project by Hungary in 1989. Slovakia then built a unilateral variant which was put into operation in October 1992 - in spite of Hungarian governmental protests. Mediation by the European Union resulted in a long-years legal case whose end is uncertain. The ICJ decision from September 1997 prescribed both parties to start new negotiations under certain framework conditions.
Even without Nagymaros, the revised Gabcikovo system has major environmental impacts. The floodplain area of more than 20,000 ha was - next to the Gemenc-Beda-Kopacki Rit and the Hainburg floodplains - the last large floodplain forests in central and south-eastern Europe. Although still having been subject to regular inundations, it already suffered from dropped water tables due to river bed erosion (upstream dams) and local large-scale gravel excavations. Construction works destroyed more than 5,000 ha of floodplain forests but still left another 8,000 of diverse forests and side-arm system aside.
Since the start of operation, 80-90% of the Danube water is diverted on a stretch of 50 km from its original river bed into a sealed canal. As the residual flow can neither compensate for the 2-4 m drop of the water tables nor for the missing water supply of the side-arm system, artificial water input structures were built, which provide a permanent and little varying supply for the floodplain. A chain of small weirs stabilises the water levels. The continued absence of needed inundations and water fluctuations ("Danube heart beat") and the complete disconnection of the side-arms from the river is leading - for largest parts of the area - to a list of negative ecological short- and long-term changes, including

Surprisingly, the impact of Gabcikovo was presented by the dam promotors in such a biased way that many visitors gained the impression that this project "saved the Danube floodplain". In addition, critical persons - scientists, NGO representatives and others - were publicly attacked and discredited over the years. This atmosphere has prevented over many years an objective evaluation of the project, also because the ongoing intensive scientific monitoring was used to support the propaganda and the two parties' argumentation in The Hague. Today, a new solution for Gabcikovo is being re-negotiated between the two new governments. A solution allowing more water for the Danube and the wetlands is still possible. WWF has - as an independent party - published in 1997 a new report assessing five years of Gabcikovo's environmental impact and proposing "How to Save the Danube" (at least 2/3 of the water, a lifting and constricting of the river bed allowing a reconnection with the side-arms).

Drava dam at Novo Virje (HR-H)
The lower Drava river, together with its main tributary, the lower Mura, rank among the still most intact river stretches in the entire Danube basin. The upper alpine reaches of both rivers in Austria are largely destroyed by chains of hydrodams (on the Drava continued through Slovenia and in Croatia down to the mouth with the Mura). Starting from the Mura at the Austrian border downstream to the mouth of the Drava into the Danube (Kopacki Rit) there is a non-dissected, largely pristine river continuum of altogether 370 km - unique in Central Europe. There is the acute threat that this could be cut into half by a new Croatian hydrodam at Novo Virje (near Koprivnica). The project stretches over 22 km including a reservoir of 1,600 ha and a power plant with a 121 MW installed capacity. While the old Drava river bed usually forms the - formerly strictly protected - border with Hungary, there is here a new river bed running over Croatian territory which would be used for the new reservoir and dam site. However, the dam project would have direct transboundary impact on the core zones of the Hungarian Duna-Drava national park as well as on the Croatian Repas oak forests.

New scientific studies have shown the extremely high ecological value of this river section which hosts the whole diversity from pioneer sand bars and cliff banks to reed beds, sand dunes, wet meadows, oxbow-lakes, soft- and hardwood floodplain forests. The fauna and flora can be described as complete for such biotops and has European importance (black and white stork, river otter, sea eagle etc.).

Different to this, a recently published study of the dam promoting company was presented as an environment impact assessment which proved to be particularly weak in the ecology and hydrology impact assessment. Dam opponents presented an alternative proposal to develop this area into a core zone of a new large transboundary biosphere reserve which would support eco-tourism (e.g. bird watching, spa resorts).

Romania
River regulation has a long tradition in Romania. Between 1940 and 1988, the size of embanked floodplain areas along the Danube increased from 50,000 ha to 435,000 ha (over 1,000 km long). Today, Romania has more than 400 large dams. All are located at Danube tributaries like the Siret (88 hydropower plants!) or the Olt (43 plants). Their total production in 1995 was 16,630 GWh (= 29% of the Romanian electricity production).
The biggest hydropower dam in Romania is located at the Djerdap (Iron Gate) gorge (117 km long) and constitutes a joint object together with the Federal Republic of Yugoslavia. It is also the largest single hydropower dam and reservoir system along the entire Danube (the next upstream and the second largest is Gabcikovo). Here, the river acquires an exceptionally high hydropower potential due to its rich flows (average 5,500 m³/sec) and an overall drop of 34 m (river width in the dam section: 1,100 m). There are two dams Iron Gate I (at rkm 942) and Iron Gate II (at rkm 863) where the second reservoir serves for balance peak operation waves. Installed capacity is at 1,266 MW, the annual production is at 6,490 GWh.
The dam creates a reservoir which flooded land, the towns of Orsova and Doni-Milanovac, the Ada-Kaleh isle, roads, railways, bridges, telecommunications, industrial enterprises, historical monuments, etc. The new places were built near the old ones.
The Iron Gate system has transboundary effect. The sediment load carried further down by Danube decreased after 1970 after the started operation of the hydraulic structures and hydropower plants: the reservoirs have a volume of 3.2 billion m³ where some 20 million t per year of sediments (inert particles with absorbed organic matters) are trapped. Thus, especially the upper reservoir (Iron Gate I) serves both as an important nutrient sink and as a deposit of hazardous and toxic matter for many pollution sources from the upstream Danube catchment area. However, ongoing erosion problems on the downstream Danube riverbanks are attributed to the dams operation: the suspended load is reduced by the dams by some 50% ; this is partly balanced by river bed erosion.

4 Times of Transition

Over the last two decades, the public image of river engineering and dam construction became quite negative. Reasons include one-sided interests of the dam lobby, abuse of authorities' power, no or small mitigation of negative effects, rejection of critical questions and alternative proposals and bad cost-benefit ratios. In addition, conventional river engineering did mostly miss or ignore new scientific experience which recommended the down-grading of dam/canal sizes or even the cancelling of a project due to other reasons than the pure continued building of one dam after the other.

After the massive protects against large dams/canalisation projects in the 1980s in Austria and later in Hungary, Slovakia and Germany, not only environmentalists, the general public and the media but also politicians and financing institutions were building up a very critical position against new dam projects. The Gabcikovo, Vienna-Freudenau or the Lambach dams could only be built and finished under big public, political and legal constraints, even more the cases of Gabcikovo and Vienna-Freudenau proved to become the predicted stranded investments with no chance to ever become profitable. For the disputed Danube section in Bavaria (Straubing-Vilshofen), the opposition was successful in pressing for a moratorium until the year 2000 and a testing of alternative engineering measures which would allow improved navigation without damming the river.

It therefore can be stated that in the 1990s the Era of Dam Construction with its spirit of engineers "taming the rivers" is coming to an end on the Danube. More objective and more multi-disciplinary pre-project studies on the need of a dam and the possible project variants, including environmental impact assessments and an evaluation of the cost-benefit ratio are becoming project hurdles which are difficult to be passed. Much more attention has to given to indirect effects, like flood hazards, downstream river bed erosion, groundwater recharge, changed biodiversity and economic productivity. It became much more difficult to get access to international funds which are no longer available for disputed dam projects. Expert and public opposition are accepted negative criteria for "new" dam projects. Recent examples are

Start of the "Era of River Restoration"

When looking at the present situation of dam building and river engineering in the Danube basin it becomes evident that there are not only just very few dam projects going on, but that there won't be many more possibilities for conventional dam building in the future either. On the other hand there is quite an impressive list of very modern river engineering expanding in this region. The new spirit and objective of governmental institutions and certain river authorities is to take account of past experiences in river management (e.g. in terms of profitability of hydro dams, flood control, water table and water quality alterations, recreation and biodiversity needs). As a result, authorities with the help of scientists and NGOs have started in the 1990s to reverse certain mistakes of the past river management by preparing and implementing investment programmes to

restore river dynamics
and
to increase and secure multiple sustainable uses
(i.e. recreation, drinking water supply, water quality purification, productivity for forestry and agriculture, flood protection etc.).

It is already quite difficult to have a simple overview, as there are very many small and local river restoration activities going on which do not receive international attention. At present, some 17 million US$ are being spent through the following major river and wetland restoration programmes in the Danube basin (remark: the list is certainly incomplete!):
 Wetland Restoration Programmes in the Danube River Basin

A separate comment has to be given to the recent "Living Rivers Campaign" in Austria which in a innovative co-operation of the Ministry for Agriculture & Forestry, the Ministry for Environment and WWF Austria has drawn throughout the year of 1998 nation-wide media and public interest in river management and restoration. The three goals for two years (1998 - 2000) are

It is evident that these programmes do not only include baseline data collection of ecologists but also technical planning of engineers and implementation with the help of bulldozers and other construction equipment. Therefore, more and more river engineers and river management institutes support ecology-oriented river development as they recognise this as an important field and task of future river engineering. Still, it has to be emphasised that wetland restoration is undertaken in the Danube basin at least at a level of one magnitude smaller than conventional dam building and river development. However, when taking into account the limited possibilities to build more dams, reservoirs and canals in this region, then the future of river engineering has two routes:

A new study presented by WWF Austria (Heeb 1999) states that the former loss of 400,000 ha of inundation area (5% of Austria!) resulted in a drastic decrease of flood security, of groundwater levels, of self-purification capacity and of biodiversity. For compensation, WWF demands that 84,000 ha of new river space should be set aside by the year 2030 (i.e. 2,800 ha/year) and 8,000 km of river stretches revitalised (i.e. 260 km/year).