PART 8

 

8.1. Conclusion statements

Taking into consideration the evaluation of the environmental monitoring results in hydrological year 2003 the Nominated Monitoring Agents concludes:

1.    The gauging station Bratislava-Devín plays the key role in determination of water amount discharged into the Danube old riverbed downstream of the Čunovo dam. The average annual flow rate in this station in the hydrological year 2003 was 2000.75 m3s-1, which was close to the annual average flow rate considered in the intergovernmental Agreement (2025 m3s-1). In contrast to the normal average annual flow rate extremely low flow rates were recorded during the vegetation period, what influenced the soil moisture, the forest and biota development. 
Taking into consideration obligations envisaged in the intergovernmental Agreement the Slovak Party was obliged to release an average annual discharge of 395.21 m3.s-1 into the Danube riverbed downstream of Čunovo dam. According to the observations carried out at the Doborgaz and Helena gauging stations it can be stated that the yearly average discharge released to the Danube old riverbed downstream of Čunovo in the hydrological year 2003 was 398.97 m3.s-1. When subtracting the amount over 600 m3.s-1, released during floods (1 value), the annual average flow rate of 397.94 m3.s-1 is obtained. This means that according to the water management agreed in the intergovernmental Agreement, signed in 1995, the obligation of the Slovak party to release the yearly average discharge, which is function of the yearly average flow rate recorded at the Bratislava-Devín gauging station, was fulfilled. The discharge into the Mosoni branch of the Danube, taking into consideration the technical and hydrological circumstances envisaged in the intergovernmental Agreement, was 44.87 m3.s-1. This means that the amount of water released to the Mosoni branch of the Danube envisaged in the Agreement was fulfilled as well.

2.    The surface water quality in the Danube in the observed period slightly improves in long-term, which is reflected in decrease of nutrient contents, CODMn, TOC, saprobic index and bacteria. Changes in water quality on observation points in the Danube throughout the year refer to the water quality fluctuation at Bratislava, which is characterising the water quality entering the influenced area. The hydrological year 2003 in water quality was similar to the previous hydrological year, no extreme values of any parameters were observed. The reservoir, situated downstream of Bratislava, depending on the actual flow rate and flow velocity, play certain role in settling and in removing of suspended solids. The water quality in the main right side river branches due to the water supply follows the water quality observed in the Danube. The water quality in tributaries and the pollution from the settlements on the Hungarian side primarily affect the water quality in the Mosoni Danube, observed at the Vének profile.

3.    Considering the course of water levels in the Danube river during the hydrological year 2003 it can be stated that it was an atypical year. In general highest ground water levels were induced in the winter period as a consequence of extremely water rich months, while in the vegetation period continuous decrease of natural water level was observed. However, where water supply was applied – in the Slovak and Hungarian river branch system and along the Mosoni Danube – the ground water levels were artificially raised in comparison to the natural water level. In spite of unfavourable hydrological and meteorological conditions in 2003 (low flow rates in the Danube during the whole vegetation period, and insufficient precipitation amount) no significant changes were observed in the area affected by the water supply in comparison to the previous years. In general it can be stated that the water supply into the right side river branch system plays an important role in influencing ground water levels over the Szigetköz region. As a result of the measures realised according to the intergovernmental Agreement significant increase of ground water levels occurred for low and average flow rate conditions in the Danube. However, no significant changes in the upper and middle part of the Szigetköz region and decrease of ground water levels along the Danube riverbed are characteristic for the high flow rate conditions. The monitoring results highlights the necessity of solving the ground water level decrease in the lower part of inundation area on both sides. 
Increase of ground water levels in the strip along the Danube old riverbed on both sides could be satisfactorily ensured only by increasing water level in the Danube by measures realised in the riverbed. Such measures will improve the ground water regime in the inundation area and could also help in artificial flooding. However, these measures have to conform to the flood protection activities in this area.

4.    According to the long-term data evaluation on the selected 16 observation wells on the Hungarian side it can be stated that the water base of Szigetköz is typically characterised by higher iron and manganese content. The manganese content was permanently over the groundwater quality limit at 12 wells, while the iron concentration exceeded the limit value at 9 wells. In 2003 further changes in ground water quality could be observed at certain wells, since the content of components – presumably indicating contamination of agricultural origin and waste water – like nitrogen forms and organic material changed from well to well. However, their content was generally lower or it did not changed in comparison to the previous year. These changes in the water quality might reflect the integrated effect of the changes in the area, in which the changed ground water flow directions, affected by the water supply, might also play role.   
On the Slovak side it can be stated that the basic physical and chemical parameters, cations, anions and oxygen regime parameters satisfies the agreed ground water quality limits at all monitoring objects. The manganese content frequently exceeded the given limits on 4 of 18 evaluated wells, while the iron concentrations frequently exceeded the agreed limits on 2 wells and occasionally on another two wells. In case of the wells used for drinking water supply, it can be concluded that the water quality parameters are excellent and the water composition is characterised by high stability on both sides.

5.    The soil moisture content in 2003 was strongly influenced by unfavourable hydrological and meteorological conditions. Although the winter period was characteristic by high flow rates in the Danube, in consequence of lack of precipitation in February and March the soil moisture content reached 70-80% of the content in previous year on most of the monitoring sites on both sides. Higher amount of rainfall occurred in May, June and July only, however it was not sufficient and there were major differences in the spatial distribution. Due to this, due to average and below average flow rates in the Danube in vegetation period the soil moisture content decreased since the beginning of the vegetation period. On monitoring sites, which are not influenced by the water supply the soil moisture content reached the lowest values recorded in the whole observed period. Unfavourable hydrological and meteorological conditions were partly reduced in areas where water supply is realised. In such a situation an artificial flooding of the inundation area would be the best solution in the future.

6.    The monitored forest stands on the Slovak side consist of willow and cultivated poplars. The cultivated poplar stands are widely spread in the inundation area. The height increments on most of them still meet the curves for the I. growth class. On the other side the climatic conditions in 2003 evoked premature defoliation in several regions – particularly the region at Dobrohošť and the strip along the Danube old riverbed where the drainage effect strongly occurs. Actually the older stands don’t show signs of damage due to the water insufficiency, however, this phenomenon will probably cause problems at reforestation of these stands. The yearly increment of the willow stands in the year 2003 remained on the stable level. The health state of the willow stands in the evaluated year remained good. The long lasting period of low flow rates in the Danube in 2003 influenced lower part of inundation area negatively (in neighbourhood of the tailrace channel). This is demonstrated by unsuccessful reforestation of the white willow, what emphasizes the need of solving the water supply of this region.       
The composition of forest stands on the Hungarian side is comparable to that on the Slovak side. The increments of willow and poplar stands on shallow soils lag behind the expected growth rate. The general health condition of willows was moderate, and in the area upstream Dunasziget and Kisbodak villages the health conditions show remarkable deterioration. High calcium content has been found in the soil, which can be blamed for the destruction of willow under the water-poor site conditions. Soils with such high carbonate content – over 20 % – can be used for cultivation of willows only in case of advantageous water supply. In the case of missing floods the stands covered by willow became not suitable for them and conditions for willow cultivation became noticeably worse. The health conditions of poplars show continuous improving during the last years. The unfavourable moisture conditions, especially when low amount of precipitation occur during the vegetation period, could be improved by artificial flooding of the inundation area.

7.    Unfavourable hydrological and meteorological conditions in 2003 negatively influenced the soil moisture conditions in the area. Particularly in regions where the water supply is not solved – lower part of inundation area on both sides. Although the initial conditions for optimal start of vegetation growth were almost reached at the beginning of vegetation period, intensive deterioration of moisture conditions in following months was registered. On monitoring areas with sufficient water supply and favourable moisture regime changes of the phytocoenoses were not observed, however in areas where the water supply missing or is not sufficient changes towards more xerophilous communities were registered. The macrophyte communities are highly dependent on site-specific hydrological conditions. After introducing the water supply the river branch system became through flowing. Macrophytes settle riverbank and part with slow current of water. In the flood-protected areas the development of macrophytes remained unchanged thanks to the permanent water supply and unchanged hydrological conditions, however some quantitative changes were noticeable in the river branch system after floods in previous years. Considering the terrestrial molluscs it can be stated that the unfavourable climatic conditions were reflected in significant decrease of abundance, mainly during the summer sampling. On the other hand the occurrence and regular presence of several rare species were confirmed in 2003. Changes in aquatic fauna reflect the changes in the river arm system. Generally it can be stated that along the water supply path the number of species rose (the number of rheophilous species increased). The species composition became stabile. Reappearance of some rheophilous species in the ichtyofauna reflects the partial reconnection of the right-side river branch system with the main riverbed. The characteristics of fish community became stable on monitoring areas supplied by water. In consequence of the unfavourable hydrologic conditions in 2003 the species diversity and abundance, which increased after floods in 2002, returned to the level recorded before floods in 2002. In the flood-protected area the species richness became stable and during the last years was balanced.

8.2. Proposals

Proposals given in this point will be obligatory for both Parties and do not require further approval when the actual Joint Annual Report is approved and signed by Nominated Monitoring Agents.

1.    The negotiations between the Parties on the term “flood event” have not been finalized yet. Therefore, continuation of negotiations will be performed between the experts on surface water hydrology in next few months. The detailed method of the released water amount into the Danube old riverbed in case of high discharges will be elaborated as well.

2.    Negotiation will be started in order to achieve unified evaluation of sediment quality. Both Parties are using Canadian standards, however they differ in limit values and classification. When the procedure of evaluation will be elaborated specific conditions of the region where the method of evaluation will be used must be taken into account (e.g. background concentration of parameters, etc.)

3.    New standards on drinking water supply were accepted in both countries in 2003. Considering this a new table should be elaborated in the ground water quality section, with regard on the possible changes in EU standards as well.

4.    Considering the approximation of EU legislation in surface water quality, revision of biological data included in the data exchange in the frame of joint monitoring should be done. The emphasis in evaluation of the ecological state is put on biological parameters.

5.    The Slovak Party in monitoring of Odonata, Ephemeroptera and Trichoptera will consider the possibility of observation of flying imagines, simultaneously with the larvae monitoring.