UN UNIVERSITY LECTURES: 10
Environmental Management of an International River
Faculty of Natural Sciences
A Presentation Made at the United Nations University
on 2 September 1994
It is my great pleasure to talk to such a distinguished audience today about the environmental issues related with the second largest river of Europe-the River Danube-in connection with the large dam project which has attracted wide attention in Europe, and from a purely technical point became also a political issue among the countries located near the river.
Water is part of the biosphere and the key natural resource, but like all the Earth's natural resources, water is exhaustible. Access to clean water is a fundamental requirement for health and sustainable development. Therefore the UN Conference on "Water and the Environment" in Dublin, January 1992 and "Environment and Development"-the Earth Summit in Rio de Janeiro in June 1992 set challenging tasks also for the water resources development sectors. Also the UNESCO/WMO/ICSU International Conference on Hydrology-Towards the 21st Century: Research and Operational Needs, held in Paris, March 1993, declared that research emphasis should be given to large-scale problems, issues related to ecohydrology, connections between hydrology and climate, and the vulnerability of the water resources.
From the Dublin Statements on Water and Sustainable Development
Scarcity and misuse of fresh water pose a serious and growing threat to sustainable development and protection of the environment. Also human health and welfare, food security, industrial development and the ecosystems on which they depend, all are at risk, unless water and land resources are managed more effectively than they have been in the past.
The Conference also stated that concrete action is needed to reverse the present trends of over-consumption, pollution and also increasing threats from drought and floods. Recommendations for action at local, national and international levels were set out.
The Conference developed a series of recommendations which also form a framework for the planning of the International Hydrological Programme of UNESCO. This programme is the only science and educational programme of the United Nations system in the field of hydrology and water resources, which would serve the needs of both developing and developed countries. This month (in September 1994) an International Conference within the UNESCO IHP on Developments in Hydrology of Mountainous Areas will be held in Slovakia to discuss the Alpine and Mediterranean Regional Hydrology.
Water Management in Europe
Water management within European countries has traditionally been well organized. The present structures in strategic planning, operation and management can be largely understood from these historic conditions. One can say that water quantity problems in Europe have been solved or can be easily solved. On the other hand, new problems arise, due to poor water quality and to increasing competition for the available high-quality water in areas where also ecological demands for water use exist.
Thousands of projects have been built during the last century on the European rivers to stimulate and promote the development of flood control, transport, ecologically clean energy and environmental management. In all, technical, economic, social and environmental aspects, as well as the needed research leading to the use of modern techniques have already been well established.
Water is largely unrestricted by national boundaries. In Europe the rivers are usually shared by several countries. To ensure equal access to water resources, it is important that water be considered in its geographical, rather than in its political context. This means that the river basin, as a natural unit of water supply, must be the basis of any discussion around water use.
One such international river is the Danube (Donau in German, Duna in Hungarian), of outstanding importance in the European geopolitical region, which crosses the territories of many nations influencing lives of millions of people.
About the River Danube and Danube Region
The river basin of the Danube covers an area of 817,000 km2, where about 80 million inhabitants live, the length of the river is 2,857 km and the average discharge in the delta is 6,500 m3s-1. It starts only 100 m from the Rhine-Danube watershed between the Black and North Seas. The Danube is the largest transboundary river basin in Europe. Realizing the parameters of the river, we can feel its continental significance. On its long course from the Black Forest in Germany to the Black Sea in Romania, the Danube flows further on through Austria, Slovakia, Hungary, former Yugoslavia and Bulgaria.
The Danube region was never a closed and homogeneous political formation in the course of history. Given the extraordinarily rich tribal or national group structures in Europe at various stages of development, it would have almost been a miracle. However, the fact is that the frequent contacts made possible by the river, the exchange of information, cultural and other cooperation, the similar mental characteristics and styles of living of these peoples (at least at modern times), and the resulting-often unconscious but intense-feeling of brotherhood in the population played an important role in the development of European civilization. Although the river joined these people, not only separated them, it never united them in one political and constitutional formation-because of geographic dimensions and the diversity of people living in the Danube basin. Apart from this, several political changes occurred in the course of history, which altered the geopolitical map of the Danube region.
If we go back to the beginning of the 20th century, we see that there have been eight states in the Danube region since the end of World War I. This is the basic fact when looking for a solution for our present as well as future problems. The frontiers of these states do not coincide with the natural borders of the Danube region, but all these countries participate in exploiting the Danube to a greater or lesser extent. Moreover, even other European states, not directly situated on the Danube, wish to contribute to the present process of European integration by participating in the development of the Danube region. Such an example is Germany, which represents a bridge between the Danube basin and the Rhine land in the form of the Rhine-Main-Danube Canal.
Importance and Benefits of the Danube
The Danube countries have always been genuinely interested in a large-scale Rhine-Danube navigation route running across Europe and linking Sulina at the Black Sea with Rotterdam on the North Sea, a 3,500 kilometre long journey. The Danube itself served for many years for navigation as a part of the west European waterways. Since completion of the Rhine-Main-Danube Canal, officially opened in Nuremberg in September 1992, the Danube became an organic part of this important transcontinental waterway.
Furthermore, the Danube is a natural resource of water for industry, agriculture, domestic water supply, people, and the groundwater supplies. For the proper management of the Danube, between 1950 and 1980 a total of 69 dams with a volume above 1 million m3 were constructed on the Danube and more are being prepared. Also, in the so-called "Iron Gates" part of the Danube, former Yugoslavia and Romania constructed a second stage, and joint Bulgarian-Romanian works are being prepared. In most of them, hydroelectric power plants have been implemented for using the Danube as a source of the most environmentally friendly energy.
The Danube flows through the Swabian and Franconian Jura Mountains in Germany, touches the Alps in Austria, then drains the southwest slopes of the Czech Forest, runs into flatlands near Bratislava in Slovakia and continues through Hungarian lowlands, then through Vojvodina in Yugoslavia, along the Romanian-Bulgarian border and finally ends in the Danube delta, merging with the Black Sea. Therefore the nature of the landscape is very changeable along its course. The Danube is also an important bioclimatological factor within the whole basin, and a reservoir of extensive biodiversity in the region. It is an important part of the water cycle in the European microclimate.
Problems of Further Joint Utilization of the Danube
Such conditions make great demands on the Danubian nations and have also generated an exceptional relationship between each nation and the Danube. The water from this river is essential for them for many purposes. The Danube on the Slovak-Hungarian section has extraordinarily complex natural conditions. Also floods and difficulties for navigation were characteristic of it. As I mentioned before, such problems on the Danube have been already solved in Germany and Austria, also in Yugoslavia, Bulgaria, Romania (except for some modernization works).
The most disastrous floods of 1954 and 1965 hit the territories of Slovakia and Hungary but also the other Danube countries were influenced by flood disasters-Austria and Yugoslavia.
In 1954 the Danube broke through its banks, in four places on the Hungarian side. The whole area of Maly Zitny Ostrov (Hungary's Szigetkoz region), an area of 33,000 hectares, was flooded.
The territory of Slovakia was hit by the disastrous floods of 1965, when the left flood-protection dike burst in two places-at Cicov and Patince. The floods inundated 71,000 hectares of land, and internal waters destroyed a further 114,000 hectares of fertile soil. There was almost a total crop failure, a large number of farm animals died, almost 3,500 houses were destroyed and a further 5,000 damaged, all roads and railway lines were flooded. Almost 54,000 inhabitants had to be evacuated from the affected region. In addition, the old woodlands were destroyed, many fish and wild animals died, and sources of drinking water became polluted. This is just the short record of the last two biggest flood disasters.
Deepening the River Bottom
Another problem affecting this region is increasing deepening of the River Danube bottom around the Bratislava profile. Since the construction of many waterworks upstream on the Danube in Austria and Germany the transportation of bed-load sediments and of gravel rapidly was reduced. Due to the speed and energy of flowing water, the river bottom decreased 1 cm per year on average in the past. In the 1970s it was 3 cm per year, in the 1980s already 16 cm per year. The level of the river in Bratislava has decreased by 2 meters in the past 30 years. These lowered levels in the Danube's main bed resulted in a situation where not only collateral branches of the river remained half empty during most of the year, but also lowered embankments and cracked the walls of buildings in many cities and villages due to land depression.
Another alarming fact was found during tunnelling works under the Danube for planning underground constructions; the fine ancient Pannonian sediments in the river bed are covered by only a very thin layer of the gravel. If this thin layer will be further eroded by the running water (that will happen within a few years), a quick deepening and loosening will endanger the stability of embankments and buildings in Bratislava City, with the further risk of flooding the territory below the town.
Endangering the Famous Inland Delta
Recently another risk was recognized. The decrease of water level in the territory of the famous inland delta with its unique ecosystem of fauna and flora and the wetland woods in an area of about 4,000 hectares began to dry out. Intensive agricultural production on the most fertile area in Slovakia (on ca. 165,000 hectares) was also affected by lack of water for supplementary irrigation and groundwater was not sufficient for most crops.
Ecological Problems of the Danube and Its Tributaries
The river has lived its own life for ages and solved its problems in its own way. That is until the arrival of people, who took possession and made use of the whole river. Not only its water, but fauna and flora, sand, gravel, gold, transport capacity and hydroelectric potential as well. Finally, people strictly limited the space of the river in the countryside, which used to belong to it completely in the past. The effects of natural forces, which form the river, were multiplied by human activities. Man should know the natural laws of the river and the countryside, through which it flows, and be willing to respect these laws. If not-catastrophes may arise.
Let me look on the energy problems. Energy issues in the territory of Slovakia were solved using water, coal and nuclear energy resources.
The hydroelectric potential of the River Danube in Germany and Austria is almost fully exploited. Only the Austrian section downstream of Vienna, the Austrian-Slovak border section, remained untouched and before the waterworks of Gabcikovo-Nagymaros also the common Slovak-Hungarian section of the Danube was not utilized for energy.
Conditions for Navigation and International Shipping
As I mentioned before, the Danube itself, and also as a part of the Rhine-Main-Danube Canal, became an important transcontinental waterway. Due to natural sediment transport, several kilometres downstream of Bratislava and due to change of the longitudinal inclination of the main river bed in this profile, fords appeared in several sections between Rajka and Gonyu, affecting safe navigation. Costly dredging of the sediments was not the most economical solution.
Multinational Utilization of the Danube
There are many international treaties on the Danube based on the international river laws. Going back in history-the Paris Conference in 1920 constituted the International and European Danube Commissions.
Later, the significant Belgrade Convention was signed in 1948 and ratified by seven Danube countries. It created the so-called new Danube Commission, consisting of representatives of the Danube states. It has its own headquarters, stamp and flag. The Commission is obliged to see to the observance of the Convention, to prepare the schedules of large-scale measures on the navigation route in cooperation with the Danube countries, to carry out work which is beyond the capacity of one country and to give advisory services to all Danube countries, including technical and economic plans for all major projects. The Commission is obliged to work on the unification of all navigational conditions on the Danube with regard to the specific conditions in some river sections, including pilot services, utilization of hydrometeorological and hydrological data, collection of statistical data about shipping, and issuance of navigational aid.
Individual articles of the Convention describe in detail the navigational regime, the river management on the lower Danube, the river management of the section below Bratislava and other necessary topics.
Talking about the above-mentioned problems on the common Slovak-Hungarian part for utilization of the Danube, they are being solved. The idea of exploiting the hydroelectric potential of this river between Budapest and Bratislava is not a new one. Several plans were made in 1880, 1915, 1921. After World War II, Czechoslovakia began to prepare studies for the utilization of the river in 1952, and after this preparatory works were continued with Hungary. In 1964, 1967 and 1973, joint investments began for building a power plant on the diversion canal after a comprehensive evaluation. It was called the "Gabcikovo-Nagymaros System of Hydroelectric Schemes". A great amount of surveying and research work were carried out by specialized institutes of the Slovak Academy of Sciences, the Hungarian Academy of Sciences, various universities, research institutes and consultations abroad. We focus on some details for two reasons:
-The section of the Danube studied is situated in the so-called "Inland Delta" area of the Danube, which is formed by up to 300 m thick layers of river gravel, sand and other alluvial sediments deposited over thousands of years. Constructing the foundations of hydraulic structures safely and economically in this area in which there is some seismic activity is an extremely challenging engineering task;
-With regard to the given natural conditions, big attention was paid to geological surveying and seismic prospecting, as well as to modelling research of all hydraulic structures. Natural conditions were summarized, and possible environmental effects of technical measures were evaluated in the so-called "bioprojects" in 1975 and later in 1984.
The joint water policy, water management and scientific studies resulted in the international joint Gabcikovo-Nagymaros twin dam project on the Danube. This common effort of former Czechoslovakia and Hungary led to the signing of the International Treaty in 1977, also registered by the United Nations. The upper and lower dams (connected hydraulically by interconnected water levels) were quite asymmetrical, with different volumes of construction work, construction costs, and methods of power generation, as well as different schedules of construction.
Construction works on the hydroelectric schemes at Gabcikovo and Nagymaros began in spring 1978. The Hungarian and Czechoslovak organizations involved worked according to a plan and deliveries based on equal division of work expressed in terms of the financial costs between the contracting parties (50 : 50), regardless of the country in which they were built. In the Treaty, both sides further decided on the division of the planned annual output of 3,900 GWh of electricity in the same 50 : 50 proportions. The parties to the Treaty committed themselves to secure the continuity of international navigation and not to worsen the quality of water in the Danube by their operation.
The plan according to the Treaty of 1977 dealt with the following problems:
- Regulation of the internal water regimes
- Regime and protection of underground water supplies
- Water purity
- Utilization of the old river bed of the Danube and its river branches
- Bed-load transport regime
- Regime of ice floods
- Agriculture, fishery and game management
- Protection against floods
- Protection of historical monuments
- Utilization of the region for recreation and sports
- Complex system of monitoring
The original hydroelectric twin dam project Gabcikovo-Nagymaros consisted of the following main structures:
Gabcikovo part (upper part of the system):
The Main Reservoir (Hrusov-Dunakiliti)
Total volume: 240 million cubic metres
Useful volume: 60 million cubic metres
The Diversion Canal (continuation of the reservoir to the power plant)
Length: 17 km, width: variable 267-737 m
The Hydroelectric Power Station
Total installed capacity: 720 MW (8 vertical Kaplan turbines, max. 90 MW)
Two twin locks; length: 275 m, width: 34 m
Outlet Canal (discharged water from the power plant into the water reservoir at Nagymaros)
Length: 8.2 km, width: 185 m
Nagymaros project (lower part of the system):
Width: 7 x 8 m
The Hydroelectric Power Station
Total installed capacity: 158 MW (6 bulb-turbines)
River regulation and protective measures, reconstruction of existing flood control dikes, sealing aprons, seepage canals, drains and pumping stations.
Two twin locks; length: 275 m, width: 34 m
Until now only the Gabcikovo part of the Project has been put into operation. The Hungarian side decided, due to alleged ecological risks of the project, to stop partially construction work on the dam over the Danube in 1989, and stopped all construction work in 1990, when already 80-95% of the works were completed. The Cabinet of the Slovak Government evaluated the situation and decided to make measures to put the power plant at Gabcikovo into operation by building an alternative and temporary solution on Slovakia's territory. Before that, all governmental and professional negotiations were ruined due to the fact that Hungarian representatives had the mandate only for negotiation about stopping of all works, demolishing the waterworks, and for annulling the Treaty from 1977. But as I mentiond, the Treaty was internationally drafted as being unilaterally indissoluble.
Both sides requested an impartial expert assessment from the highly recognized foreign companies, Bechtel Environment, Inc. of San Francisco, USA and Hydro-Quebec International of Canada. Both companies agreed on the view, that it is possible to deal with the expected ecological consequences without postponing operation of the waterworks.
We in Slovakia call it a "temporary solution", because we firmly believe that common sense will prevail in the end. The temporary solution fully respects the concept of the original plan elaborated according to the Treaty of 1977. Among the seven variants of the temporary solution which have been elaborated, the alternative of damming the Danube in Slovak territory without building the dam at Nagymaros was selected as the only acceptable solution. The new dam started operation in October 1992. The borderline continues to follow the centre of the present river bed, so the course of the frontier did not change.
Of course, the original flow parameters have been changed and has resulted in a big loss of the energy output. Only two or three turbines out of eight are working daily due to the smaller volume of the reservoir upstream. The turbines can presently give 140-160 GWh per month only; nevertheless, 2,200 GWh were produced between October 1992 and December 1993. This is approximately half of the production with fully installed capacity of the project. This is a big loss, for such nations like Slovakia and Hungary. Nevertheless, even with this temporary solution it is easy any time to recontinue construction according to the original project.
Environmental Effects after Two Years of Dam Operation
The full environmental impacts of such a large project can be observed, of course, only after a longer period after operation. Nevertheless, due to quick water movement in the rivers and in the porous soil the first positive aspects of the Danubian dam on the surrounding biota have been recognized, quickly, just two years after operation. This is also due to the detailed monitoring system of various environmental data around the reservoir, with 494 built-in measuring points and 53 automatic signalling stations installed. The monitoring system is continuously observing and evaluating the fluctuation of the water-table and the water quality, as well as other parameters.
The project showed its utility in late 1992, when floodwaters occurred, that the region is now safe against the danger of disastrous flooding.
The erosion process of the river floor was stopped as well as the diminishing of the water-table, with all its adverse effects on nature and the community. The groundwater level in the region increased due to the damming of the Danube (up to 3 metres downstream of Bratislava). Groundwater lowering was registered on ca. 6% of the influenced territory, but was easily compensated by additional filling-up of the system of river arms.
The project also enables improved conditions for shipments using the Rhine-Main-Danube transcontinental waterway, connecting Rotterdam (North Sea) and Sulina (Black Sea) without any reloading, conserving fuel and producing less exhaust fumes. During the last year ca. 11,000 ships went through the navigation locks in Gabcikovo.
The river branches of the Danube in the Slovak side are now filled by water, bringing water to wetland woods, which before got water only about one month in a year. This now attracts waterfowl and fish, creating ideal conditions for wildlife and at the same time guarantees survival of floodplain forests and the famous Danube's inland delta. The permanent feeding of water into the river arms-the Little and the Mosoni Danubes-has revitalized 200 km of these rivers, which were also ten months per year without any inflow from the Danube.
The capacity of wells, supplying freshwater from deeper aquifers, was increased by 30 to 40 per cent, without influencing the quality. The quality of groundwater around the influenced area by the Danube was also improved, increasing its oxygen content. The more intensive seepage has increased also the dynamics of the groundwater flow, the polluted upper layer of groundwater is being diluted and gradually replaced. A part of the seepage waters, collected in the seepage canals, became a source of high quality water for irrigation and industrial use.
Production of the most environmentally friendly energy by hydroelectric power plants is the main advantage of the project and would enable substitution of several classical coal power plants or one old nuclear power generator, if fully implemented. Furthermore, it was calculated that after utilization of the renewable hydraulic energy of the Danube according to the proposed project, the general savings in fuels represents 3.9 million tons of brown coal or 1.0 million tons of oil. The burning of this quantity of coal would take from the atmosphere as much oxygen as is created by 400,000 hectares of forest, and produce 23,000 tons of sulphurous fumes each year.
The project itself creates ideal conditions along a 50 kilometre stretch for the establishment of a new national park of an international stature for nature conservation, unique in its kind in Europe. According to a rapid initial survey for the future preserves in Central Europe, floodplain areas of the Danube are among 24 major areas selected as new opportunities for nature conservation in the new Europe.
For full utilization of environmentally friendly energy potential of the Danube, the lower dam in Nagymaros still needs to be constructed. The Hungarian side could easily elevate the groundwater level on their side by building elevation transverse barrages in the old Danube according to the original 1977 project.
Some catastrophic forecasts by some environmentalists have not been fulfilled, and no negative influences of the project on the environment have been recorded yet, almost two years of the Gabcikovo part of the twin dam Danubian project being in operation. The most frequently heard arguments against the environmental effects of the Danubian dam project have already been disproved in practice. Due to positive impacts on environment and economy of both countries, the professionals-hydraulic engineers, economists and ecologists-believe that completion of the whole project would further contribute to the ecological and economical development of both Slovakia and Hungary.
Therefore, there is still a chance to withdraw the documents submitted by Slovakian and Hungarian sides on 2 May 1994 to the International Court of Justice in the Hague. Since this summer, a non-official consultation started between Slovak and Hungarian specialists. Also, the representatives of the World Wide Fund for Nature recently accepted the mostly positive influences of the waterworks on saving the floodplain forest in that region. The Director-General of the WWF, Claude Martin, has now stopped any campaigning against the dam, after receiving detailed scientific refutation of the claim that the dam is causing an ecological catastrophe. Recently New Scientist reported that the European director of the WWF, Magnus Sylven, recently (in June 1994) apologized to Slovakian scientists, saying "how embarrassed I personally feel about WWF's past involvement" in the campaign against the dam.
In June this year the Hungarian (Arpad Goncz) and Slovak (Michal Kovac) presidents met jointly with US President Bill Clinton, who praised the people of both nations for their steadfastness, "even in the face of great difficulty", and congratulated the two presidents for their "genuine leadership ability". Both presidents then received a joint award from the Institute for East-West Studies for their efforts to overcome historical differences between Slovakia and Hungary. The Slovak president stated that the Gabcikovo Dam controversy needs to be depoliticized and it would be better to consider solving the case in bilateral talks rather than in an international court, if a historical reconciliation is achieved between the two countries.
Binder, J., 1993. The present state of implementation of the Gabcikovo-Nagymaros System (G-NS). In: International Conference on "G-NS: Intentions and reality", Bratislava, pp. 41-50.
Cizik, F., 1993. Hydropower station Gabcikovo in operation. Urbanita 74:19-26.
Danisovic, P., 1993. Problems solved by the Gabcikovo-Nagymaros Project. In: International Conference on "G-NS: Intentions and reality", Bratislava, pp. 27-31.
Danubius Magnus (Gabcikovo), 1993, T.R.T. Medium, Bratislava.
Hrasko, J., 1993. Effects of Gabcikovo-Nagymaros Project on soils and agricultural production. Urbanita 74:65-70.
Hrasko, V., 1993. The Gabcikovo Project-Saving the Danube's Inland Delta. Q111, Bratislava, 31 pp.
Jambor, A., 1993. The Gabcikovo-Nagymaros System, intentions and reality from the point of view of central investor's authority. In: International Conference on "G-NS: Intentions and reality", Bratislava, pp. 19-26.
Jansk´y, L., 1994. The influence of the Danubian Gabcikovo Project on floodplain forest after two years operation. In: International Symposium on Forest Hydrology, Tokyo (in press).
Kalis, J., Bacik, M., Klucovska, J. and J. Topolska, 1993. The sedimentation of the bed and suspended load in the Hrusov reservoir and the possibilities of influencing it. In: International Conference on "G-NS: Intentions and reality", Bratislava, pp. 285-289.
Liptak, J., 1993. The river Danube of Europe. NVK International, Ltd., Bratislava, 114 pp.
Liska, M., 1993a. A complex view on the hydro-electric system Gabcikovo-Nagymaros. Vodohospodarska vystavba, Bratislava, 10 pp.
Liska, M., 1993b. Gabcikovo Project-catastrophic forecasts falling into pieces. Europa Vincet, Slovak European Review, XV (3):14-19.
Liska, M., 1993c. Analysis of the dispute about the Gabcikovo-Nagymaros Project. In: International Conference on "G-NS: Intentions and reality", Bratislava, pp. 369-396.
Mucha, I. and E. Paulikova, 1993. Impact of Gabcikovo water-works on groundwater regimes. Urbanita 74:77-84.
Mucha, I., Paulikova, E. and Z.Hlavaty, 1993. Impact of Gabcikovo water-works on groundwater level. In: International Conference on "GNS: Intentions and reality", Bratislava, pp. 313-318.
Regional Focus: Central Europe. In: World Resources 1992-93; A guide to the global environment, Oxford University Press, p. 59.
Secretariat of the United Nations Commission for Europe, 1994. Protection and use of transboundary watercourses and international lakes in Europe. Natural Resources Forum, 18(3)171-180.
Soltesz, A. and J. Benetin, 1993. Analysis, prognosis and regulations of soil water regime in floodplain ecosystem. In: International Conference on "G-NS: Intentions and reality", Bratislava, pp. 255-260.
Soltesz, A. and J. Szolgay, 1993. Hydrological and energetical criteria of water regime regulation in floodplain area of the Danube. In: International Conference on "G-NS: Intentions and reality", Bratislava, pp. 99-104.
Soltesz, A., Gramblicka, M., Lindtner, J. and P.Michalik, 1993. On application of artificial flooding in floodplain area of the Danube. In: International Conference on "G-NS: Intentions and reality", Bratislava, pp. 345-349.
Sutor, J., 1993. Monitoring of water retention in zone of aeration of the Zitny ostrov influenced by the water structure Gabcikovo. In: International Conference on "G-NS: Intentions and reality", Bratislava, pp. 455-459.
United Nations Educational, Scientific and Cultural Organization, International Hydrological Programme (Fifth Phase-Revised Outline), 1994. Hydrology and Water Resources Development in a Vulnerable Environment, Paris, 49 pp.
Valtyni, J., 1993. The influence of Gabcikovo water-works on floodplain forests. Urbanita 74:74-76.
Return to previous page
Return to the UNU Homepage