Recommendations with Respect to the EC Reports · Alternative Recommendations for the Future Water Regimes · Short-term Solution · Long-term Solution · References

A. Recommendations with Respect to the EC Reports

As stated above, WWF suggests producing as soon as possible:

A water quality study including:

• control sampling and analysis on the changes in surface and groundwater quality,
• changes of the underground currents, and
• potential impacts on the drinking water reservoir.

A river engineering study investigating:

• the present state of the Cunovo scheme,
• the technical possibilities and costs for the improvement of the discharge into the Old Danube, and
• the new variant to reduce the undesired sedimentation processes in the storage lake up- and downstream from the Cunovo weir through the construction of a small navigation route (see WWF recommendation C).

Each study should be worked out by an independent expert team also involving local, competent experts, providing that they can work independently from the government and the Gabčíkovo operator.

B. Alternative Recommendations for the Future Water Regimes

WWF is aware of the fact that due to the present technical state of the Cunovo weirs, the very short time up to the next vegetation period (March 1994), and the difficult political situation, it is hard to achieve significant improvements.

However, it is clearly a question of the European political interest how quickly the needed political negotiations will produce results and how much time will be allowed to pass by for the realisation of the urgently needed and hopefully agreed steps.

WWF tried to keep this “time problem” in mind when discussing and formulating the following recommendations. The scientists involved are convinced that this “gentle solution” can be achieved faster, cheaper, and politically easier than the “technical solution” the EC Mission’s Working Group was able to agree on.

Priority objectives

Every new solution has to respect the following priority objectives:

1. The reestablishment of the hydrological dynamics both in the old river bed, in the side-arm system, and in the floodplains.

   This means that the water level fluctuations in their amplitude (minima, maxima), number, and duration, in the channels and in the floodplain, have to run in such a way as they were at least under pre-dam conditions, and at best before the serious gravel excavations started (i.e. the 1960s). This automatically entails the needed natural input of nutrients into the floodplain. The water supply for the Old Danube is closely dependent on the upstream Danube discharge fluctuations, as measured at the Devín gauge.

2. The restoration of the groundwater table dynamics.

   This is possible only under a non-restricted connection between the surface water and the aquifer.

3. The reestablishment of a direct and non-inhibited connection between the river and the floodplain, including the side-arms.

   This will allow the migration of organisms and diaspores.

4. The enhancement of the morphodynamics.

   Erosion and sedimentation are prerequisites for the habitat and biological dynamics of floodplains. They should be promoted to the largest extent possible.

5. The restoration of self-purification processes.

   They have to be supported to the maximum extent in the entire floodplain and river area.

C. Short-term Solution

Based on the technically possible discharge minimum of 600 m³/sec and discharge maximum of at least 940 m³/sec (more, up to 1,500 m³/sec, depending on the technical possibilities of the Cunovo weirs and with respect to the Slovak legal order stated in the “19 Conditions” from June 1991), WWF suggests as an urgent measure for the next two years — which are needed for the preparation of the long-term solution — instead of underwater weirs, the accumulation of sediment bodies in the old river bed in the form of gravel banks and islands.

The goal of this measure is to reduce the discharge area, which provokes a lifting of the water level and thus will even permit an inflow of Danube water into some of the side arms (whose closures have to be reopened again).

Even though this interim solution cannot balance the drawbacks of underwater weirs concerning the groundwater levels, it offers real benefits:

• it largely prevents upstream colmation and eutrophication;
• it preserves the river continuum and allows free migration of fish and other organisms in the river bed;
• it is no alien construction (like an artificial underwater weir) in the river bed, and uses autochthonous material from the river bed itself and from the banks — this measure does not disturb or change the typical environment for the river biocenoses;
• these sediment bodies allow an easy transition towards the needed long-term solution suggested in D;
• they can easily be built up within a short term of a few weeks, using the existing local gravel and sand deposits in the old river bed; and
• even moderate changes of these sediment bodies by erosion will not reduce their expected purpose and positive effects.

The design and planning preparation of the suggested measure can be accomplished within a few months.

Subsequent to this measure in the river bed, the lateral dikes — especially in the Slovak floodplain — and the bilateral closures between the side-arms and the Old Danube, should be reopened (lowered) to the maximum extent which is ecologically supportive.

D. Long-term Solution

Starting from the above-mentioned facts that:

• the previous, natural water level dynamics, with all their positive effects for the floodplains and the groundwater, have to be restored;
• the discharge in the Old Danube realistically will remain below the former discharge;
• at least the Slovak legal standards (as stated in the “19 Conditions” from June 1991, following § 14 of the Slovak Water Law) will be fulfilled, but in their meaning of a dynamic discharge (cf. description in B) of 65 to 75% of water;
• an acceptable compromise will be found, orienting on the EC proposal from February 1993 (average discharge of 66%), which was already accepted by Hungary; and
• the compensation of the discharge deficit (25–35%) can only be achieved by lifting and constricting the present river bed,

which is entailed by a reduction of the existing discharge area. The lifting and constricting of the river bed can be achieved by the deposition of gravel and small-sized boulders in the old river bed. Similar to the short-term solution, this measure includes the forming of islands and gravel banks. It is expected that a stretch of ca. 20–30 km downstream of Cunovo has to be filled up with a volume of one to two meters. For this purpose, an amount of ca. 5–10 million m³ of gravel and boulders will be needed.

The origin of such material, and its environmentally sound exploitation and transport, still has to be investigated. In comparison to the amount excavated from the Danube alone on the Slovak side (e.g. 50 million m³ within 14 years), it becomes evident that the volume needed is realistic and technically feasible. The cover layer of this “new river bed” should be provided by gravel of locally typical size that can be acquired from the vicinity.

As a second WWF recommendation, it is suggested that the storage lake up- and downstream of Cunovo be reduced by new dikes to a navigation route. The objective is to reduce the sedimentation and undesired biogeochemical processes in the surface and groundwater of this artificial lake (which has no efficient sealing to the underground, unlike the power canal) to the minimum extent. This will reduce the potential water pollution threatening the nearby and downstream drinking water wells. The area in-between the new dikes parallel to the navigation route and the present lake dikes should be turned into restoration areas. If done in the appropriate way, these man-made biotopes can develop over the years into secondary wetland biotopes.

It is evident that the entire planning and realisation of this solution has to be examined thoroughly and in detail by an independent, international water engineering institute together with an ecological institute experienced in river management.

However, the preparation of this solution has to be started as soon as possible, because it will require several years for its completion.

In contrast to other proposals, this “gentle” solution offers a comprehensive approach to the river area. It will help to limit and partly even reverse the detrimental changes induced by the Gabčíkovo scheme. It will not only bring a long-term preservation of this floodplain ecosystem of European importance, but it guarantees an improvement of the presently critical groundwater situation. It is a solution for the Danube and the base for an ecologically-oriented economic development of the border region, which is to serve the livelihood of people living on both sides of the river.

References

1. WWF (1989): Stellungnahme des WWF zum Staustufenprojekt Gabčíkovo-Nagymaros. I. A. Ungar. Inst. f. Intl. Angelegenheiten. Rastatt.
2. WWF (1992): Energy for Slovakia — Options for an environment-oriented policy. Ed.: Austrian Ecology Institute, Vienna.
3. WWF (1992): Construction and operation of Variant C of the Gabčíkovo-Nagymaros project under international law. Legal study by Dr. G. Berrisch, Brussels.
4. EC Mission Data Report (2 November 1993) on Assessment of Impacts of the Gabčíkovo Project and Recommendations for the Strengthening of the Monitoring System. Budapest.
5. EC Mission Report (1 December 1993) on Temporary Water Management Regime. Bratislava.
6. Surface and Groundwater Quality (October 1993): Parts 1/2 and 2/2, by RH Union, Bratislava.
7. Extended Monitoring of Water Quality during the Filling of the Gabčíkovo Dam (period 26 October – 31 December 1992): Slovak Hydrometeorological Institute SHMÚ, Bratislava.
8. EC Mission Report (November 1992): Working Group of independent experts on Variant C of the Gabčíkovo-Nagymaros project.
9. EC Mission Report (May 1993): Field inspection at the Gabčíkovo construction site.
10. Lehotský Ján, Martin Bačík, Jiří Kalis, Ján Lindtner, and Ján Szolgay (June 1991): Vplyv prevádzky vodného diela Gabčíkovo na prírodné prostredie, VÚVH Bratislava (Impacts of the Gabčíkovo power plant on the natural environment, Water Research Institute Bratislava).
11. Schönbach Wilfried, Michael Kosz, Brigitta Brezina, and Thomas Madreiter (June 1993): Kosten-Nutzen-Analyse ausgewählter Varianten eines Nationalparks Donau-Auen. Vorläufiger Endbericht (Cost-Benefit Analysis of Selected Variants of a National Park Danube Floodplains, Preliminary Final Report). Wien.
12. Rovný Borislav (June 1993): Ichtyocenózy územia dotknutého výstavbou a prevádzkou vodného diela Gabčíkovo — pred, počas a po výstavbe VD-GN. Štúdia (Ichthyocenoses of the Area Being Affected by the Construction and Operation of the Gabčíkovo Power Plant — Before, During, and After the Construction). Bratislava.
13. Hügin G. (1981): Die Auenwälder des südlichen Oberrheins — ihre Veränderung und Gefährdung durch den Rheinausbau. In: Landschaft und Stadt, 13 (2), 78–91.
14. Henrichfreise (December 1993): written reply on rehabilitation experiences from the Upper Rhine floodplains (referring to Hägin 1980, BFANL 1988, BFANL 1990, Schelkle und Henrichfreise 1991). Bonn.
15. Roux A.L. et al. (March 1994): Rapport sur l’état des peuplements de poissons dans le secteur des plaines alluviales slovaques affecté par l’aménagement hydroélectrique de Gabčíkovo (preliminary title). Lyon. In press.