PART 8
8.1. Conclusion statements
Based on the results of environmental monitoring in the year 2011 the
Nominated Monitoring Agents conclude:
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.