PART 8

 

8.1. Conclusion statements

After considering the evaluation of environmental monitoring results in hydrological year 2006 the Nominated Monitoring Agents conclude:

  1. The gauging station Bratislava-Devín plays the key role in determining of water amounts discharged into the Danube old riverbed downstream of the Čunovo dam. The average annual flow rate in this station in the hydrological year 2006 was 2152 m3.s-1, which was the sixth highest annual average flow rate observed since 1992. Considering the course of water levels and flow rates during the hydrological year 2006 it can be stated that no unusual values occurred.       
    Taking into consideration obligations envisaged in the intergovernmental Agreement, the Slovak Party was obliged to release an average annual discharge of 425.1 m3.s-1 into the Danube riverbed downstream of Čunovo dam. According to the observations carried out at the Doborgaz and Helena gauging stations, the yearly average discharge released to the Danube old riverbed downstream of Čunovo in the hydrological year 2006 was 495.6 m3.s-1. Taking into account the modified method of average discharge calculation, accepted in the Joint Annual Report on the environment monitoring in 2004, discharges exceeding 600 m3s-1, while the flow rate in the Danube was higher than 5400 m3s-1, were reduced to 600 m3s-1. When subtracting the amount of water over 600 m3s-1 released during the flood events (15 values), the average annual flow rate of 424.5 m3s-1 is obtained, which represents 99.9 % of the amount requested by the Agreement.. This means that the obligation was fulfilled. The discharge into the Mosoni branch of the Danube was 42.57 m3.s-1, which represents 99 % of the agreed amount. Taking into consideration the technical and hydrological circumstances envisaged in the intergovernmental Agreement and the accuracy of measurements it can be stated, that the amount of water released to the Mosoni branch of the Danube was fulfilled as well.

  2. The surface water quality in the Danube in the observed period had not changed compared to the previous year. Changes in water quality at observation points in the Danube throughout the year correspond to the water quality fluctuation at Bratislava, which is characterising the water quality entering the influenced area. Increased values of some parameters in the Danube during the hydrological year 2006 were related to higher flow rates in the Danube during flood waves. The reservoir, situated downstream of Bratislava, depending on the actual flow velocity, plays a certain role in settling and removing of suspended solids. The fluctuation of water quality parameters in the right side river branch system follows their fluctuation in the Danube since introducing the water supply in 1995.
    The tributaries and local pollution of settlements, besides the water supply influence, form the water quality in Mosoni Danube. Before its confluence with the Danube the water quality is variable in time, which is proved by unfavourable values of some parameters (electric conductivity, dissolved solids, Coliform bacteria, CODMn, BOD5, nutrients and saprobic index). Compared to the previous years the water quality improved, thanks to investments realized in the water treatment plant. The amount of chlorophyll-a in the Mosoni Danube at Vének was significantly lower than in the previous year. The cleanest water was found in the seepage canals, which results from its groundwater origin.   
    Considering the surface water quality evaluation in 2006 the water quality in the Danube at Medveďov is very similar to the water quality at Bratislava.  
    Considering the sediment quality evaluation in 2006 it can be stated that the amount of analysed micropollutants in the influenced area is low and the vast majority of measured values were below or fluctuated closely to the Threshold Effect Level (TEL), when the unfavourable effect on biological life occurs rarely, in less than 25 %, and it corresponds to an uncontaminated natural environment. From the point of view of inorganic micropollutants the most polluted sampling site appeared to be the Ásványi river branch.

  3. Based on the evaluation of the ground water regime 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, a significant increase in the ground water levels occurred for low and average flow rate conditions in the Danube. No changes in the upper and middle part of the Szigetköz region, and a decrease in the ground water levels along the Danube riverbed can be registered for the high flow rate conditions.. 
    The monitoring results highlights the necessity of increasing the ground water level in the lower part of the inundation area on both sides. The ground water level increase in the lower part of the Ásványi river branch system and in the Bagoméri river branch systems and on the Istragov Island on the Slovak side could be solved by measures applied in the Danube old riverbed upstream of the confluence with the tail race channel. Such measures can improve the general situation in this region.
    An increase of ground water levels in the strip along the Danube old riverbed on both sides could be 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. Any measures applied in the riverbed or in the inundation area have to conform with flood protection activities in this area.
    An overall evaluation of impacts in the influenced area based on the comparison of periods before constructing the dam and the present time would be required. For these purposes extension of the period for mutual data exchange is necessary.

  4. Summarizing the results of the long-term ground water quality observations on Hungarian side it can be stated that the water base of Szigetköz is typically characterised by higher iron and manganese content. The iron and manganese content permanently exceed the groundwater quality limits on most of the observed wells. In 2006 the contents of nitrogen form parameters and parameters indicating the presence of organic matter in general slightly decreased or it did not changed in comparison to the previous year, organic pollution is local only. The low concentration of oxygen is typical as well. Changes in the ground water quality at some places reflect an integrated effect of the transformations that occurred in the region, in which the ground water flow directions, affected and changed by the Szigetköz water supply, also play a role.  
    Based on the results of the long-term groundwater quality observation on the Slovak territory it can be stated that the observed groundwater quality parameters mostly satisfies the agreed ground water quality limits. Sporadic exceeding of limit values occurred during the observation period as well. 
    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. However, the ammonium ion and organic matter content are higher in wells in the Győr region. In these wells also the iron and manganese content occasionally exceeds the drinking water quality limit values or oscillate around them.

  5. The soil moisture content in 2006 was significantly influenced by the flood in March/April, high discharges in May and June and precipitation amount at the beginning of the vegetation period, particularly at April. The hydrological and climatic conditions in July were not favourable, but the amount of precipitation and the flood in August increased the soil moisture content again. The end of the vegetation period was characterised by precipitation amount below the long term average and by temperatures exceeding the average values. The average ground water level during the vegetation period 2006 was higher compared to the average ground water level in last two years. At the beginning of the vegetation period the soil moisture content reached 90-95 % of the saturation level. It was characteristic that in the soil layers up to 1 m depth the minimum, average and maximum values of the soil moisture content were higher at all monitoring sites. In the soil layers below 1 m depth the minimal, average and maximal values were similar as in the previous year. Since August decrease of soil moisture content was registered and the minimal values mostly occurred at the end of the vegetation period.   
    At the lower part of the inundation area on the Slovak side decrease of soil moisture content is registered during low, or even average flow rates in the Danube. Due to riverbed erosion downstream of the confluence of the tail race canal and the Danube old riverbed the ground water level does not supply the soil profiles sufficiently. Also during the year 2006 the soil moisture observation at monitoring sites situated in the agricultural area on the Slovak side proved that the soil moisture content remained unchanged.

  6. The monitoring of forest stands on the Slovak side was focused onto various cultivated poplars clones. Based on the monitoring results it can be concluded that in general the growth of poplar clones in the different part of inundation is similar. The increment of the older stands after the growth culmination decreases slowly, their growth, especial in height is henceforth good. From the point of view of the young trees, it can be stated that at the monitoring restoration slow growth was observed, which gradually got better in the following years. In the case of newly planted trees the root system is not developed, so the access to the water is difficult. Problems with reforestation of cleared area emphasize the necessity of hydro-technical measures. The water regime in inundation area can be improved by ground water level increase, by artificial flooding of the area and by measures in the Danube old riverbed, which will increase the water level. The health state of forest in the inundation area in 2006, evaluated on the basis of terrestrial survey, was good, similarly as in the previous year. 
    The composition of forest stands on the Hungarian side consist mainly of willows and cultivated poplars. Besides this several hardwood and lowland forest stands are monitored. According to dendrometric measurements in 2006, the changed moisture conditions in the Szigetköz region after diversion of the Danube affected the forest stands, however the impact is strongly dependent on the forest type and its location. The older and middle-aged poplar stands “I-214” and “Pannonia” with outstanding growing capabilities, which are situated in a good habitat, were not affected or the impact was very slight. However, there are seriously affected stands, which consist of willows or young poplars, which are situated on locations unsuitable for these kinds of trees. The rate of girth growth of the observed poplar stands was similar to that in previous years. The positive impact of floods and higher amount of precipitation was not reflected in higher increments. The health state of forest stands was favourable. Concerning the species composition changes were detected through the past decades. There are more tree species in the Szigetköz today than they were 20 years ago. The proportion of cultivated poplars decreased significantly whilst other cultivated, improved domestic species were being involved.

  7. The beginning of the vegetation period, April-May 2006, was rich in precipitation. The temperature was lower, so the intensive growing of vegetation started later (end of April). The temperatures in June and July were extremely high and in July the were accompanied by lack of precipitation. The situation got better in August, when the precipitation amount was higher. The autumn was dry, atypically warm and long lasting. Hydrological conditions in 2006 were favourable as well. A large part of the inundation area was flooded several times (March/April, June, August), high discharges occurred till end of June. Extremely low discharges in the Danube were characteristic in July. Flow rates reached values near minimums ever observed. These conditions strongly influenced the development of plant and animal communities. The favourable climatic and hydrological conditions were reflected in increase of biomass of the herb layer, although its height was slightly lower in comparison to the previous year when maximal values of the whole monitoring period were recorded. The species number was insignificantly higher. At some of monitoring areas retreat of Urtica dioica and invasive species was registered in a consequence of floods. The structure of phytocoenoses along the Mosoni Danube remained unchanged. Stabilized development of phytocoenoses can by observed in a greater part of the left side inundation area. However, unfavourable moisture conditions for the lowland forest were found in the area upstream of the water supply canal and in the region of Istragov Island. Higher amount of precipitation and favourable hydrological conditions in 2006 postponed the defoliation and no mosaic loosening of coverage in the herb layer occurred. 
    The terrestrial mollusc’s community on a large part of Slovak inundation area are stabilized. In the most moisturised regions typical marshy wetland forest communities occur. However, worsening of the hydrological regime in the region of Istragov Island invoked a medium degradation of the malakocoenoses, euryek species are already abundant. The tendency of gradual decrease of species diversity and abundance of individual species registered in previous years has changed. In 2006 increase of species number and significant increase of abundance was recorded, at some of hygrophilous species several hundreds of individuals were registered. The mollusc communities at some sampling sites might be influenced by clearing the surrounding forest stands.   
    The macrophyte communities are highly dependent on site-specific hydrological conditions. After the washout by the strong flood in 2002 regeneration and intensive development of aquatic macrophytes was registered in last years. The discharges supplied into the active floodplain on both sides were similar to discharges in previous years. Large part of the floodplain river branches is characteristic by higher water depth, which corresponds to stabilized species composition of aquatic plant communities. In the last two years the macrophyte communities were very similar. 
    Concerning the aquatic fauna in the Danube there are considerable differences between the Slovak and Hungarian results. According to the Slovak observations the aquatic Mollusc's communities had a weak occurrence and the Planktonic Crustaceans, Caddisflies and Mayflies communities were very poor in the Danube. The Hungarian results proved a significant increase of species number and abundance in Mollusc's community, the Planktonic Crustaceans, Caddisflies and mayflies were rich in species and abundant. In the inundation area stable, rich in species and abundant Mollusc's communities were registered on both sides. In case of Dragonflies poor communities were registered in the Slovak inundation area. On the Hungarian side changes towards rheophilous species are observed, while on the flood protected area stabilised Dragonflies communities are registered. The Planktonic Crustaceans in the inundation area are rather rich in species, on the Slovak side the euplanktonic species dominate. The composition Planktonic Crustaceans on the Hungarian flood protected side indicate the diversity and stability of habitats. In case of Caddisflies and Mayflies poor communities were registered in the Slovak inundation area, while on the Hungarian side rich in species and very abundant communities were observed.  
    Concerning the fish community in the Danube it can be stated that the ichtyocoenoses in the Danube river is stabilized in last years. Slight decrease in species diversity can be registered, but the results of particular samplings are highly dependent on the actual flow rate in the Danube and other circumstances of sampling. Simultaneously with the dominance of eurytopic species an increase of foreign expansionary rheophilous species of Neogobius family can be registered. In the right side river branch system mostly the eurytopic species occur. The reappearance of some rheophilous species in the ichtyofauna reflects the partial reconnection with the main riverbed. The species richness of the fish community is significant and stable. In the Hungarian flood-protected area regeneration of ichtyofauna is observed since introducing the water supply. The species richness became stable and during the last years was balanced. Rich in species and abundant fish community was registered in the Slovak inundation area as well. Eurytopic, rheophilous and limnophilous species were registered, euryekous species dominate. In 2006 significant increase in abundance of the expansive species Ameiurus melas was recorded at monitoring site No. 2603.

8.2. Proposals 

Proposals given in this chapter 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. Monitoring in 2008 will be carried out according to the Statute on the activities of the Monitoring Agents modified in May 2007. According to the modified Statute greater accent is put on the Water Framework Directive in the frame of surface and ground water quality monitoring. The monitoring, including its evaluation, in the year 2007 should be considered as transitional.

  2. In connection with changes in methodology in water quality monitoring an overall evaluation of the preceding period is recommended.

  3. The Slovak Party repeatedly propose an extension concerning the agreed period for data exchange by at least 10 years backwards (at least since 1982). The actual period of mutual data exchange is represented by period starting in October 1992. The extension should relate to all existing data for monitoring sites, plots, areas and parameters actually included in the frame of Joint monitoring according to the 1995's intergovernmental Agreement.

  4. When an extension in data exchange period is agreed an overall evaluation of ground water levels in the influenced area based on the comparison of pre-dam and post-dam periods is recommended.

  5. The Parties propose to make an overview of evaluation methods accepted in both countries in connection with the Water Framework Directive.