PART 8

 

8.1. Conclusion statements

Based on the results of environmental monitoring in the year 2011 the Nominated Monitoring Agents conclude:

  1. The gauging station Bratislava-Devín plays a key role in determining the current amount of water to be discharged into the old Danube riverbed downstream of the Čunovo weir. The average annual flow rate in this station in hydrologic year 2011 reached 1782 m3.s-1. This flow rate belongs to below average flow rates on the Danube and represents the third lowest flow rate since operating the Gabčíkovo hydraulic structure. Considering the course of water levels and flow rates during the hydrologic year 2011 it can be stated that no extraordinary values occurred, however, one high flood wave occurred in mid January. The course throughout the year was not typical – rather big flood occurred in the winter period, flow rates mostly below average were registered from mid February to mid July, without more significant discharge waves.

Taking into consideration obligations envisaged in the intergovernmental Agreement, the Slovak Party was obliged to release an average annual discharge of 352.0 m3.s-1 into the Danube riverbed downstream of Čunovo weir. According to 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 hydrologic year 2011 was 424.4 m3.s-1. Based on the modified method of average annual discharge calculation, accepted in the Joint Annual Report on the environment monitoring in 2004, reduction of discharge released to the Danube old riverbed was done for 4 days (reduction to 600 m3.s-1). According to this the average annual flow rate in the Danube old riverbed corresponded to 409.2 m3.s-1, which represents 116.3 % of the amount required by the Agreement. If we reduce the discharge according to the suggested modification also in September, since the higher flow rate was released due to maintenance works on the power plant (reduction for 4 days), the average annual flow rate in the Danube old river bed will be 404.0 m3.s-1, which represents 114.8 % of the amount required by the Agreement. This means that the obligation of the Slovak Party was fulfilled. The total annual average discharge into the Mosoni branch of the Danube was 41.40 m3.s-1, which represents 96.3  % of the agreed amount. Taking into account the maintenance works it can be stated that the obligation envisaged in the Agreement was also fulfilled.

  1. The surface water quality in the evaluated year 2011 was similar as in previous years. Regarding the specific hydrologic and climatic conditions of the year 2011 the time series data of observed parameters were more balanced, with lower frequency of higher values. Increased values of some parameters in the Danube water were related to higher flow rates. The quantitative ratio of ionic composition of the surface water shows high stability in last years. In case of nutrients mostly lower or similar contents were registered than in the year 2010. Oxygen conditions in the year 2011 were very good; the organic pollution represented by CODMn was lower in comparison with the year 2010, in case of BOD5 lower values at some sampling sites and higher values at other sampling sites were recorded. When analysing changes in suspended solids content at sampling sites in the Danube, generally it can be stated that the suspended solids content downstream of the reservoir (at Medveďov sampling site) during flood waves is lower than in the Danube at Bratislava, which demonstrates the settling effect of reservoir. Unlike the previous years, in 2011 the content of suspended solids measured downstream of reservoir (at sampling site at Medveďov) was higher than in the Danube at Bratislava. From among the heavy metals the highest concentrations were recorded in case of copper, the lowest in case of cadmium and lead. Major part of analysed concentrations was below the detection limits of applied analytical methods.

The fluctuation of surface water quality parameters in the right side river branch system since introducing the water supply in 1995 follows their fluctuation in the Danube. The water quality in the Mosoni Danube differs in the upper and lower section of the river. The water quality on the sampling site at Čunovo/Rajka follows the water quality in the Danube, while the water quality in the lower section of Mosoni Danube at Vének (upstream of the confluence with the Danube) is formed by its affluents and local pollution from settlements. From the long-term development point of view the pollution decreased at this sampling site, although the content of nutrients and the CODMn values still reach the highest values in comparison with the other sampling sites. The cleanest water is characteristic for seepage canals, what results from its groundwater origin.

Monitoring of biological quality elements of surface water in the evaluated year at sampling sites observed by the Hungarian Party was realised according to the national methodologies for particular biological quality elements in accordance with the Water Framework Directive. According to phytoplankton the sampling sites were classified from I. to II. class, thus from high to good status, and according to phytobenthos with II. class, thus good status. Based on the monitoring results of biological quality elements and considering the evaluation of physico-chemical elements and evaluation of other specific pollutants the ecological status of surface water at individual sampling sites was determined as good, so the II. quality class.

The evaluation of sampling sites observed only by the Slovak Party was carried out according to methodology used in previous years. Saprobic indexes varied in ranges corresponding to beta-mezosaprobity, thus environment that offers suitable living conditions for a wide scale of organisms. Similarly to the year 2010, an exception was the sampling site No. 311 in the reservoir, where in case of the saprobic index of macrozoobenthos alpha-mezosaprobity occurred. In connection with the unusual hydrologic and climatic conditions, especially in the vegetation period, the abundance of phytoplankton several times exceeded the limit for mass development in the evaluated year. In comparison with the year 2010 the average annual values of phytoplankton abundance achieved higher values on all observed sampling sites.

Considering the sediment quality evaluation in 2011 it can be stated that the amount of analysed micropollutants in the influenced area is low and the majority of measured values were below or fluctuated closely to the Threshold Effect Level (TEL). However, the number of exceedings of the threshold concentrations of monitored parameters was slightly higher than in the year 2010. These concentrations varied in the range >TEL - <PEL, what represents a status when the unfavourable effect on biological life occurs occasionally. Unlike the previous year higher concentrations of zinc (on two sampling sites) and lindane (on three sampling sites) occurred in the evaluated year, which exceeded the Probable Effect Level (PEL) limit values. When exceeding the PEL limit value, the unfavourable effect on biological life can occur frequently. The highest concentrations of inorganic and organic pollution occurred at sampling sites No. 311 in the reservoir and at sampling site No. 1126 in the Ásványi river arm.

Based on comparison of water quality entering the influenced area (sampling site at Bratislava) and water quality that leaves the influenced area (sampling site at Medveďov) it is evident, that the water quality that leaves the system is very similar to the quality of the incoming water.

  1. Based on the evaluation of groundwater regime it can be stated that the water supply into the right side river branch system plays an important role in influencing groundwater levels over the Szigetköz region. As a result of measures realised according to the intergovernmental Agreement, a significant increase in the groundwater levels occurred for low and particularly for average flow rate conditions in the Danube. The increase is reduced in the upper part of the Szigetköz region and around the reservoir due to the decrease of permeability of the reservoir bottom. Certain influence have also had the adverse changes in sediment transport regime in the Danube, that are probably related to measures realized on the Austrian stretch of the Danube just upstream of Bratislava in last years. A decrease in the groundwater levels along the Danube riverbed can be registered for high flow rate conditions, however in certain distance from the Danube old riverbed no change was observed in inundation area and increase of groundwater levels in the inland area of Szigetköz.

The monitoring results still proves the necessity to solve the water supply in the lower part of the inundation area on both sides. The groundwater level increase in the lower part of Ásványi river branch system and in the Bagoméri river branch system and on the Istragov island on Slovak side could be solved by measures applied in the Danube old riverbed upstream of confluence with the tail race channel. Such measures can improve the overall situation in this region.

An increase of groundwater levels in the strip along Danube old riverbed on both sides could be ensured only by increase of water level in the Danube by some measures realised in the riverbed.

  1. Based on results of long-term groundwater quality monitoring on the Hungarian territory it can be stated that the groundwater in the upper part of the gravel sediments in Szigetköz is characterised by higher iron and manganese content. The iron and manganese contents constantly exceed the groundwater quality limits on most of observation objects. On these objects also the concentrations of parameters reflecting the local pollution are higher. The local pollution is of agricultural origin, or it originates from sewage ponds. In comparison with the previous year the contents of nutrients and organic matter slightly decreased or did not change.

The groundwater quality in deeper horizons in the Szigetköz is monitored by wells used for drinking water supply. The iron and manganese concentrations are lower in wells, which drawn the water from greater depth. In the region at Győr the iron and manganese contents exceed the drinking water quality limit values or oscillates around them. In these wells also the concentrations of ammonium ion and organic matter contents are higher. The water extracted in the northern part of Szigetköz is of satisfactory quality and the groundwater quality is characteristic by high stability. In general the groundwater quality in wells producing potable water (occasionally after pre-treatment) is suitable for drinking water supply.

Based on results of long-term groundwater quality observation on the Slovak territory it can be stated that the observed groundwater quality parameters in waterworks mostly satisfy the agreed groundwater quality limits. The exceptions are the waterworks at Bodíky and Kalinkovo. In waterworks at Bodíky the manganese exceeds the quality limit in each sampling and occasionally occurs a higher concentration of iron as well. In waterworks at Kalinkovo occasionally occurs manganese content, which does not meet the relevant limit. In case of observation objects exceeding of limit values is more frequent and it occur at more objects. Based on long-term measurements it can be stated that the organic pollution decreased during the observed period. Nutrients occur in low concentrations on monitored objects in long-term. At present they are mostly below the detection limits of applied analytical methods. In the evaluated year 2011 no considerable changes of the groundwater quality were registered. The groundwater quality in observation objects mostly reflects local influences.

Inorganic and organic micro-pollution of groundwater in 2011, monitored at selected observation objects, was found in concentrations below the limit values for groundwater quality evaluation. The groundwater chemical composition in observation objects is similar to the chemical composition in waterworks in their neighbourhood.

  1. In the year 2011 14-cycles of soil moisture measurements were performed on the Hungarian side. Measurements were performed at forest monitoring sites in the floodplain area and at agricultural monitoring sites in the flood-protected area. The soil moisture content at the end of March was slightly lower in comparison with the year 2010. The initial soil moisture content continuously decreased due to insufficient precipitation during the year. The highest soil moisture values were mostly recorded at the beginning of measurements in March. Minimal values of soil moisture were registered at the end of the vegetation period. Generally it can be stated that the average soil moisture content in 2011 in both depth intervals was lower than in the previous year.

Concerning the soil moisture development at monitoring sites situated on the Slovak side it can be stated that the soil moisture content at monitoring sites on agricultural area is stable during the whole observation period. In the year 2011 the fluctuation of soil moisture content in both depth intervals depended on climatic conditions. The soil moisture in the inundation area, along with the groundwater level and precipitation, is highly dependent on natural or artificial floods. The soil moisture content at the beginning of the year was rather high, thanks to the flood wave in January, but generally it was lower than in the previous year. The maximal average values mostly occurred in the period from January to March. However, at monitoring sites influenced by the water level fluctuation in the Danube, the maximal average soil moisture values occurred during discharge waves in July and August, especially in the layer below 1 m depth. The lowest average values in both, the layers down to 1 m depth and below the 1 m depth, were mostly recorded at the end of the year from October to December. Concerning the minimal and the maximal average values it can be generally stated that they were lower than in the previous year on most of monitoring sites.

  1. The development of forest stands in the evaluated year, according to the results of Slovak Party in 2011, despite the unfavourable hydro-meteorological conditions, mostly did not go beyond the existing tendency. The height increment quality classification of most of the observed forest stands remained unchanged or it slightly improved. Majority of stands is characterized by intensive growth increment reaching or exceeding the quality level 40 for poplar I-214. However, on some monitoring areas considerably lower increments were recorded in spite of rather favourable soil moisture conditions on these areas. The weekly girth growth measurements have been started on four of original monitoring areas in young poplar stands in 2011. Measurements still continue on two substitutive monitoring sites. The cumulative girth growth increment values of the young poplar stands were significantly higher in comparison with values recorded on the substitutive sites in previous year. The comparability of results, however, is very limited due to the age and different kind of poplar clones. Contrary to this, the actual values of girth growth increment recorded on the substitutive monitoring areas were lower in comparison with the previous year. The occurrence of zero weekly girth growth increments in the young poplar stands was rare. The growing period in the evaluated year was rather long, similarly to that in the previous year. The initiation of growth was registered in first two weeks of April and significant increments were still recorded at the end of September, when the measurements have ended. The monitored cultivated poplar stands (Pannonia and Giant clones) were healthy and vital. The occurrence of diseases and pests was sporadic during the whole growing period.

Based on results of the evaluation of aerial images it can be stated , that the portion of healthy stands in the area of interest exceeds 60 % in long-term (at present 72 %), what proves the appropriateness and vitality of trees. Groups of damaged trees are situated in upper part of the inundation area, downstream of Dobrohoą» village. The position of groundwater level in this area is unsuitable for healthy development of forest stands and for the expected wood production due to the strong drainage effect of the Danube old riverbed. Modification of regulatory structures would be required in order to ensure the increase of groundwater level. The hypothesis of large unfavourable effect of the Gabčíkovo Hydropower structure on the health status of forest stands is not proved. In comparison with evaluation results of aerial images taken in 2008 it can be stated, that the health status of 38 % of stands have not changed, insignificant worsening of health status was registered in case of 25 %, and improving in case of 23 % of stands. Significant worsening of health status was identified at 8 % and improving at 6 % of forest stands. The health status of forest stands on the area of interest is henceforth very good and stable.

Dendrometric characteristics and the health status of the forest stands monitored on the Hungarian side in the year 2011 were observed in the frame of the Joint monitoring on 14 monitoring plots, which are situated in the inundation area. The aerial survey of the health state of forest on the Hungarian side was not realized in the year 2011. Based on the detailed analysis of actual growth characteristics of forest stands it can be stated that no change have been registered in the existing growth tendency. The growth of trees in the evaluated year again developed favourably. On the monitored areas poplar stands dominate, what correspond to the actual tree composition in the Szigetköz area. Cultivated poplar “Pannonia” forms the largest portion of forest stands. Their growth can be considered satisfactory at current flow rates. In the evaluated year no slowdown was recorded even in case of slow-growing native species. The weekly girth growth increments were low in all four observed stands, despite of high precipitation amounts. In case of some stands this could be explained by high age of trees, but in case of other areas more detailed analysis would be required.

  1. In the year 2011 the biological monitoring continued without changes. The hydrologic and climatic conditions of the evaluated year were not favourable, especially due to low flow rates in the Danube during the vegetation period. The groundwater level was decreasing and the related soil moisture decreased as well. Unfavourable soil moisture conditions were slightly improved by higher precipitation amount in June and July. Flooding of the inundation area did not occurred during the vegetation period. Phytocoenoses on the Slovak side can be regarded stabilised. Changes in younger stands were mostly positive in the evaluated year, ruderal and synantropic species gradually disappears and the position of characteristic nitrophilous and hygrophilous species strengthens, the presence of invasive plant species remains negligible or they absent. However, at some monitoring areas the invasive species dominate. The phytocoenoses in the Hungarian inundation show no changes in terms of tree layer and no significant changes were observed in terms of the herb layer coverage, however, the species number was lower. On the monitoring site with cleared poplar stand the surviving herbal undergrowth had four times higher number of species compared to the previous year, with the dominance of weed and ruderal species.

The terrestrial mollusc communities on the large part of Slovak inundation area are stabilised on levels typical for different variants of lowland forest. The malakocoenoses on areas degraded by clearing of the forest stand in previous years are in different stages of regeneration at present. On the Hungarian side the terrestrial mollusc communities in the inundation shows certain fluctuation, however, no worsening tendency can be observed. Fauna remains quite diverse. Malacofauna in this region is rather endangered by silviculture than by changes of hydrologic regime. Malacofauna of the flood-protected area is rather variable, depending on local conditions, but vulnerable.

The hydrologic situation in the observed river branches on the Slovak side was substantially less favourable than in the previous years. In river arms with open water area the high number of macrophyte species remained preserved also in the evaluated year, but an unfavourable fact is the spreading of invasive species Elodea nuttallii. The bottom of shallow river arms was uncovered during the evaluated year and these sections were richly populated with marshy species and annual plants. Discharges supplied into the active floodplain on the Hungarian side were similar to discharges in previous years. Large part of the floodplain river branches is characteristic by greater water depth, to which adapted the stabilised species composition of macrophytes. The open water area was covered with submersed species together with green algae. Growing conditions in the flood-protected area were similar to that in previous years, what is associated with controllable water regime. The average species number of macrophytes have not changed. The species number in the river branches is high; the presence of several rare or protected species was proved every year. Spreading of invasive Elodea species was insignificant.

According to the monitoring data the entire stretch of the Danube is characterized by poor malacofauna in last years. This decline was probably caused by interaction of several factors – hydrologic, trophic, physical and chemical. At present only the non-native invasive species Theodoxus fluviatilis and the ubiquistic species Dreissena polymorpha has regular occurrence in the Danube. In the river branch system on the Slovak side destruction of malacocoenosis, decline of populations of large species and significant decrease in abundance of smaller species can be registered in recent years, despite the heterogeneous nature of the river arms, sufficient size of biotopes and good conditions for its development. At present the malacocoenosis is stabilized at 9-11 species, that achieve abundance of several dozens of individuals. Aquatic malacofauna in the Szigetköz region has great species diversity, with ability for regeneration. Relatively rich communities of aquatic malacofauna in inundation area did not show significant differences in comparison to previous years; they are stable. The variety of malacofauna of wetlands in the flood-protected area does not reach the diversity registered in the inundation area.

Results of the Slovak party constantly show the presence of less rich dragonfly communities. The section in river arms with flowing water are convenient for rheophilic and semirheophilic species, while the overgrown meanders are populated by stagnicolous species. Monitoring of the dragonfly community on the Hungarian side shows rather rich community. The odonatocoenoses of different types of water bodies developed differently due various interventions. Increased discharges into the Mosoni Danube did not have significant influence on the composition of present odonatocoenosis, typical for flowing water. However, the increased amounts of water supplied to the river arms in the flood-protected area have changed the communities of densely overgrown branches with stagnant water.

The cladocerans and copepods communities in the Danube are unstable and have become poorer in last years. Gradual retreat of pelagic and increase of littoral species, and increase of invasive cladocerans and copepods is registered. In most of the Slovak river branches decrease in species number and abundance was registered in both communities due to unfavourable hydrologic conditions in the evaluated year. However, on some monitoring areas rather rich communities occur with the dominance of euplanktonic or phytophilous species. The number of recorded species of planktonic crustaceans on Hungarian side in the evaluated year was the lowest in the observation period (in comparison with the previous year only a half). The stable ecological conditions in the Lipóti marsh are manifested by balanced species number of crustaceans in long-term, however, their actual species number and abundance were very low. Similar situation occurred also in the flood-protected area. Long-term observation results show high species diversity and stability, with occurrence of several rare species, however low species number and low abundance were registered in the evaluated year.

The evaluation of mayflies and caddisflies communities the Slovak Party carried out according to the methodology set out in the intergovernmental Agreement from 1995, while the Hungarian Party evaluated these communities in the frame of macrozoobenthos evaluation according to the Water Framework Directive. According to Slovak results the occurrence of mayflies and caddisflies remains permanently low, both in the Danube and in the whole inundation area. Species recorded in the Danube are mostly rheophilic, however, their occurrence is irregular in individual samples and in particular years. Mayfly communities in the river branch system consisted of 1-2 stagnicolous or semirheophilic species, achieving low abundance and mostly irregular presence during the year. According to the Hungarian results the ecological status of observed river arm in the evaluated period is moderate, and ecological status of the Mosoni Danube in the evaluated period is good.

Generally it can be stated that the ichtyocoenosis of the diverted stretch of the Danube is stabilised in recent years, with relatively low species diversity and abundance, and with the dominance of eurytopic and non-native invasive representatives. Their expansion is hindered by indigenous rheophilic species, which probably find their refuge in the not sampled medial part of the river. However, the results of both Parties indicate that the registered ichtyocoenosis is probably underestimated due to the low extent of observed area. The ichtyofauna in the river branches on the Slovak side is rather stable, rich in species with high abundance, especially in river arms connected with the Danube. The fish community is composed of eurytopic and indifferent species, with occurrence of several rheophilic species. The ichtyocoenoses in isolated river branches is poorer. The ichtyofauna on the Hungarian side, both in the inundation and in the flood-protected area is stabilized in recent years; substantial changes in species diversity or abundance were not recorded. The most frequent were eurytopic and limnophilic species, but in river branches used for water supply rheophilic fish species were present as well. The abundance of invasive black bullhead (Ameiurus melas) was negligible in the evaluated year.

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. Slovak and Hungarian experts recommend to perform long-term evaluation of the monitoring results, with the aim to optimize the monitored parameters and frequency of monitoring. Optimization should relate in particular to the quantity and quality of surface and groundwater, as well the assessment method. Long-term evaluation and optimization of the monitoring is to be undertaken outside the scope of the existing evaluation.

  2. Slovak and Hungarian experts agreed on continuing the discussion on the Slovak proposal for reconsidering the evaluation method of surface water quality, which was agreed by both Parties on the meeting of Monitoring Agents on April 25, 2007.