EC Recommendations for Strengthening of Monitoring System, 1993

EXECUTIVE SUMMARY

BACKGROUND

As a follow-up of the 'Special Agreement for Submission to the International Court of Justice of the differences between the Republic of Hungary and the Slovak Republic concerning the Gabcikovo-Nagymaros Project' a Group of Monitoring and Water Management Experts for the Gabcikovo System of Locks (Working Group) was established by the Republic of Hungary, the Slovak Republic and the Commission of the European Communities (CEC).

The tasks of the Working Group fall in two parts:

	*	On the basis of available data to assess the impacts of the Gabcikovo Project and to prepare recommendations for strengthening the monitoring system in the area.

	*	Preparation of recommendations for a Temporary Water Management Regime as well as for necessary discharges, water levels and remedial measures.

The present Data Report deals with the first of the above two tasks, while the Final Report of the Working Group scheduled for the beginning of December 1993 shall deal with the second aspect.

The Working Group has obtained most of the relevant data and information requested from the two Governments. The report is based on this information.

IMPACTS OF THE GABCIKOVO PROJECT

Major general impacts as compared to pre-dam conditions have been identified from the available data with regard to the following aspects:

Discharge

In the Old Danube the discharge has in 1993 been reduced to in average about 400 m3/s corresponding to about 20 % as compared to the pre-dam condition.

Surface water level

At Bratislava the water levels during low flow periods have increased by 1-2 m as compared to pre-dam conditions, i.e. to a level corresponding to the situation 40 years ago. In the upstream part of the Old Danube the 1993 water levels have been reduced by 2-4 m as compared to pre-dam conditions, and have thus reached a level 2 m below the lowest ever recorded values. In addition, the characteristic natural dynamics of the water level fluctuations have been changed (reduced) significantly.

Sediment transport and sedimentation/erosion

Significant erosion occurred the first 500 m downstream the Cunovo structures under the November 1992 flood event. This material has been deposited downstream in the Old Danube. sedimentation of fine material/silt can be seen in the Old Danube. Most likely, sedimentation of the total bed load and a substantial part of the suspended load have occurred in the reservoir. However, there are presently not sufficient data to quantitatively assess such impacts.

Ground water leve1

In June/July 1993 the situation in Slovakia shows that over the entire area the ground water levels have increased or have not been affected. The increases have mainly occurred in the upstream area close to the reservoir, i.e. in the area which has been most negatively affected by the long term trend of decreasing ground water levels. On the Hungarian side, where comprehensive assessments have not been made, it appears that ground water levels have increased close to the reservoir (Rajka - Dunakiliti region). Furthermore, it appears that in the middle part of Szigetköz between Dunakiliti and Asvanyraro ground water levels have decreased in areas close to the main Danube. On both sides the ground water level fluctuations have been reduced significantly.

Electricity production

The Gabcikovo hydropower plant has produced 150 - 200 GWh/month in 1993. This corresponds to about 10% of Slovakia's electricity consumption.

In addition, minor impacts have been observed or no significant impacts can be detected from the available data for the following aspects:

Surface water quality

With exception of November - December 1992, when sudden changes of regime and a high flood event occurred, no significant changes in surface water quality parameters as compared to pre-dam conditions can be detected after damming the Danube.

Ground water quality

In general, no significant ground water quality changes can be identified after the damming of the Danube. One exception is the Rusovce area where some parameters (e.g. Total Dissolved Solids and nitrate) have changed due to changes in the flow pattern. No changes in concentrations of heavy metals nor organic micropollutants have been detected.

Flora and fauna

Due to insufficient data availability and due to the long response time of natural systems with regard to flora and fauna, no major general impacts can be documented as yet. However, changes in the abundance of certain species have been observed.

Agriculture

Due to increases of ground water tables on the Slovak territory a slight increase in the capillary water supply for Slovakian agricultural areas has taken place. In Hungary, where comprehensive assessments have not been made, the impacts on agriculture are uncertain.

Forestry

As a result of the changes in ground water levels the forestry has been positively influenced in Slovakia and negatively in Hungary.

RECOMMENDATIONS FOR STRENGTHENING OF MONITORING SYSTEM

The Working Group recommends that the present monitoring system, including the extended programs specifically aiming at monitoring possible impacts of the Gabcikovo Project, be continued.

In addition, the Working Group recommends that the monitoring system be strengthened in two aspects:

	*	aspects requiring more measurements, either in terms of measurements of new parameters or more measurements (in time and space) of already measured parameters; and

	*	aspects where discrepancies between Slovakian and Hungarian data have been detected, and where coordination efforts therefore are required.

For the different parameters the recommended strengthening is as follows:

Discharge

For obtaining firm conclusions on the discharge uncertainties the following checks are required to be carried out by joint Hungarian-Slovakian teams:

	*	Check on discharge calibration curve at the bypass weir at Cunovo.

	*	Check on discharge calibration curve at the turbines at Gabcikovo.

	*	Check of discharge rating curves at Rajka and Dunaremete.

Surface water levels

There is a need for a new monitoring program on measurements of surface water levels in the side channels on the flood plains both in Hungary and in Slovakia.

Surface water quality

There is a need for a new monitoring program on measurements of surface water quality in the side channels on the flood plains both in Hungary and in Slovakia.

Sediment transport and sedimentation/erosion

There is a need for establishment of a permanent sediment transport measurement program comprising both bed load and suspended load measurements at the following locations:

	*	Upstream the reservoir.

	*	In the reservoir.

	*	In the old Danube.

	*	In the side channels of the Hungarian and Slovakian flood plains.

	*	Downstream the confluence at Sap/Palkovicovo.

Furthermore, there is a need for establishment of permanent programs for monitoring river bed and reservoir topography.

Ground water quality

The intensive monitoring must be continued for the coming years, especially with regard to areas close to the Danube where the infiltration conditions have been changed. Depending on the development of the measured ground water quality parameters it may be required to add more observations in the future.

Flora and fauna

A biomonitoring program comprising the following elements should be carried out:

	*	Geobotanical monitoring.

	*	Mapping of the bird species.

	*	Investigations on fish populations, Carabide-beetles, grasshoppers and living and dead mussels and water snails.

	*	Monitoring of plankton in major water bodies.

Forestry

The following monitoring should be carried out:

	*	Mapping the forest types in the scale 1:10.000.

	*	Annual measurements of height, perimeter and leaf area at selected "monitoring trees".