PART 8
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. 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. 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. 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. 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. 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. |