PART 8
8.1. Conclusion statements
Based on environmental monitoring results in year 2009 the
Nominated Monitoring Agents conclude:
1.
The gauging station Bratislava-Devín plays a key role in determining the 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 the hydrological year 2009
was 2163 m3s-1, which belongs to flow rates on the Danube
above the average. Considering the course of water levels and flow rates during
the hydrological year 2009 it can be stated that no extraordinary values
occurred, one high flood however occurred at the end of June. The course
throughout the year was typical – low flow rates in the winter period; higher
flow rates in the spring and a flood in the summer.
Taking into consideration obligations
envisaged in the intergovernmental Agreement, the Slovak Party was obliged to
release an average annual discharge of 427.3 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 2009 was 484.8 m3.s-1. According to the
modified method of yearly average discharge calculation, accepted in the Joint
Annual Report on the environment monitoring in 2004, reduction of the discharge
released to the Danube old riverbed was done for 8 days (reduction to 600 m3.s-1).
According to this the average annual flow rate in the Danube old riverbed
corresponded to 435.5 m3.s-1, which represents 101.9 %
of the amount requested by the Agreement. This means that the obligation of the
Slovak Party was fulfilled. The discharge into the Mosoni branch of the Danube
was 41.31 m3.s-1, which represents 96.1 %
of the agreed amount. The water amount discharged to the Mosoni branch of the
Danube was reduced during the flood wave in June. Taking into account the
technical and hydrological conditions it can be stated that the obligation
envisaged in the Agreement was fulfilled.
2.
The surface water quality in the evaluated year 2009 was similar as in previous
years. Considering the specific hydrological and climatic conditions in the
actual period the observed surface water quality parameters did not reach
extreme values. Changes in water quality at observation points in the Danube and
in the river branch systems throughout the year correspond to the water quality
fluctuation at Bratislava, which is characterising the water quality entering
the influenced area. Basic physical and chemical parameters in the Danube and in
the river branch system connected to the Danube main riverbed show seasonal
variations and some of them predominantly depend on the flow rate. Increased
values of some parameters were related to higher flow rates in the Danube. In
case of nutrients slightly higher concentrations were registered in comparison
with the previous year, however in long-term they did not violate the tendency
of pollution decrease. The dissolved oxygen content remained preserved at the
level of previous years. The organic pollution represented by CODMn
was higher in comparison with the previous year 2008, in case of BOD5
decrease of pollution was registered. When analysing the changes in suspended
solids content at sampling sites in the Danube, it can be stated that the
suspended solids content downstream of reservoir during flood waves is lower
than in the Danube at Bratislava, which refer to settling effect of the
reservoir. From among the heavy metals the highest concentrations were recorded
in case of zinc, copper and mercury (on the Slovak side). The lowest contents
were registered in case of chromium and lead. A large part of analysed
concentrations was below the detection limits of the applied analytical methods.
The water quality in the Mosoni
Danube differs in the upper and lower section of the river. The water quality at
the sampling site at Čunovo/Rajka follow the water quality in the Danube, while
the water quality on the lower section of Mosoni Danube (upstream of the
confluence with the Danube) is formed by its affluents and local pollution from
settlements. Compared to previous years the water quality significantly improved
thanks to investments realized in the wastewater treatment plant. In general it
can be stated that the content of all nutrients decreased at this sampling site,
although their concentrations in comparison with other sampling sites still
reach the highest values. The cleanest water was found in the seepage canals,
which results from its groundwater origin.
The monitoring of biological elements
of the surface water quality in the evaluated year at jointly monitored sampling
sites and at sampling sites observed by the Hungarian Party was realised
according to the national methodologies for particular biological quality
elements in harmony with the Water Framework Directive. Both Parties carried out
the evaluation of biological quality elements separately. Based on the Slovak
evaluation results of the biological quality elements the sampling sites in the
Danube and Mosoni Danube at Čunovo/Rajka were classified into III. quality
class, which correspond to moderate ecological status. Water in the seepage
canal corresponded to the II. quality class. Based on the Hungarian results the
sampling site in the Danube old riverbed at Rajka was classified into the I.
quality class (high status), while all other sampling sites into the II. quality
class, which corresponds to good status. It have to be noted however, that in
the Hungarian evaluation only results from phytoplankton and phytobenthos
monitoring, and only the phytoplankton at sampling site at Rajka, were taken
into account.
According to the National
methodologies also the overall ecological and chemical status at observed
sampling sites was determined. Based on the Slovak results the overall
ecological status at sampling sites in the Danube and Mosoni Danube at Čunovo
was moderate (III. class) and in the seepage canal at Čunovo it was good
(II. class). Based on Hungarian results all sampling sites were classified
into good ecological status (II. class). Good chemical status was not
achieved at three sampling sites (Rajka, Medveďov and Mosoni Danube at Čunovo).
Incongruence was caused by the content of DEHP organic substance.
Considering the sediment quality
evaluation in 2009 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), when the unfavourable
effect on biological life occurs rarely. In case of inorganic and organic
contamination of sediments on the Slovak side concentrations close to TEL limit
value within the range >TEL and <PEL, or even concentrations lower than
TEL limit value were recorded. In sediments analysed by the Hungarian Party,
similarly as in the year 2008, several exceeding of PEL (Probable Effect Level)
were recorded, when the unfavourable effect on biological life occurs
frequently. In 2009 exceeding occurred in case of zinc and mercury in June. In
samples taken in September the high concentrations were not proved and the
measured contents belonged to the lowest ones from among the heavy metals.
Concentrations of organic pollution mostly varied below the TEL limit value,
when the unfavourable effect on biological life occurs rarely.
Comparing the water quality entering
the influenced area (sampling site at Bratislava) and the water quality leaving
this area (sampling site at Medveďov) it is evident, that the water quality
leaving the system is very similar.
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. A decrease in the ground water levels
along the Danube riverbed can be registered for high flow rate conditions,
however in some distance from the Danube old riverbed no change was observed in
inundation area and increase of ground water levels in the inland area of
Szigetköz. In general the overall situation is similar as in the previous year
and no significant changes can be observed.
The monitoring results highlights the
necessity to solve the water supply 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 also 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 increase of water level in the Danube by
certain measures realised in the riverbed.
4.
According to results of the long-term water quality observations at 16
groundwater quality observation wells on the Hungarian side, it can be stated
that the water base of Szigetköz is typically characterised by a higher iron
and manganese content. The iron and manganese content exceed the drinking water
quality limit values on most of the observed wells. In general it can be stated
that contents of nitrogen form parameters and parameters indicating the presence
of organic matter (CODMn) slightly decreased or it did not changed in
comparison to the previous year. The organic pollution is local, particularly of
agricultural origin, or in some cases it originates from wastewater settlement
tanks.
When analysing the groundwater
quality data from wells used for drinking water supply it is evident that the
ammonium ion and organic matter contents exceed the drinking water quality limit
values or oscillates around them The iron and manganese concentrations are lower
in waterworks, which are pumped from a bigger depth. The water extracted in
waterworks Dunakiliti I., Feketeerdő T-II and Darnózseli I is of satisfactory
quality and the groundwater quality is characteristic by high stability. In
general the groundwater quality in drinking water producing wells (occasionally
after pre-treatment) is suitable for drinking water supply.
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. In case of waterworks exceeding of manganese limit value
was recorded at Bodíky waterworks in every sample and occasionally it occurs at
Kalinkovo waterworks, in the year 2009 it did not occur. In case of observation
objects exceeding of limit values is more frequent and it occur at more objects.
The groundwater quality at waterworks is stable in long term. The groundwater
quality in observation objects mostly reflects local influences.
5.
The soil moisture content at the beginning of the vegetation period was higher
in comparison with the previous year. Due to the lack of precipitation in April
the soil moisture content decreased and the decrease continued till the
beginning of June. In June the soil moisture decrease was interrupted thanks to
significant amount of precipitation, which resulted in a flood wave at the end
of the month. During the flood significant part of the inundation area was
flooded; the soil moisture was replenished. The groundwater level was higher by
0.5 m comparing to the previous year. Just after passage of the flood wave, in
the first half of July, the maximal soil moisture values were recorded. Since
then continuous decrease of soil moisture content followed till the end of
vegetation period. Minimal values of soil moisture were registered either at the
end of the winter period or at the end of the year (mostly in October). In
general it can be stated that the average soil moisture content in 2009 was
slightly higher in comparison with the previous year, especially maximal values
were significantly higher thanks to flooding. The soil moisture contents at
agricultural monitoring sites on the Hungarian territory were mostly dependent
on precipitation and weather conditions.
Concerning the soil moisture
development at monitoring sites situated in the agricultural area on the Slovak
side it can be stated that the soil moisture content and the position and
fluctuation of ground water levels during the whole observed period remained
unchanged. In the hydrological year 2009 both, artificial and natural flooding
of inundation occurred. The highest flow rate reached 8288 m3s-1,
which means that two thirds of inundation area was entirely flooded. The soil
moisture content at the beginning of the year was rather low. But thanks to
increased precipitation amount in January, February and mainly in March the soil
moisture content on most of the observed sites reached maximal average values.
Higher values were recorded only just after flooding the inundation area. The
lowest values in the layer down to 1 m depth were mostly recorded in September
and October. The lowest values in the depth interval from 1 to 2 m were
registered almost exclusively at the end of the year, in October and November or
December. The maximal values, depending on the position of the monitoring site,
occurred after flooding in June and beginning of July. Due to low water level in
the Danube during last months of the year the soil moisture content at the end
of the year was similar or even lower in comparison with the starting content at
the beginning of the year. Concerning the minimal and the maximal values it can
be generally stated that minimal values were similar to the values in the
previous year, however the maximal values were significantly higher thanks to
the flooding.
6.
The development of forest stands according to the results of Slovak Party in
2009 did not deviate from the existing tendency. The increments remained on the
increased level, which was achieved in previous years. The quality
classifications of height increments of most observed areas remain unchanged (at
high level); on several young areas significantly improved. In young forest
stands, which were considered as problematic after their planting, continuous
improving of their state and stabilisation of growth increment is registered.
These young forest stands are healthy as well. According to the actual weekly
girth growth increments it can be stated that the growing got intensive after
improvement of hydro-meteorological conditions in June-July. Zero weekly girth
growth increments were registered only sporadically. In comparison with the
previous year only minimal differences were registered in the occurrence of
illnesses and pests. It have to be emphasized the need of more efficient
utilisation of existing weirs in the river branch system for elimination of
groundwater level decrease and for application of artificial floods. Forestry
observations also prove that the increase of discharge in the spring have to be
commenced before the beginning of growing season, in case of warm winter not
later than at the beginning of March. The necessity of permanent water supply to
the Istragov area is constantly actual.
7.
The hydrologic conditions of the evaluated year were favourable, large part of
the Danube inundation area was flooded. Phytocoenoses on the Slovak side are
stabilised, changes in certain young stands can be assigned to gradual closure
of treetops. The phytocoenoses observed in the Hungarian inundation are
characteristic with stable species diversity too. Flooding caused the decrease
in species diversity registered in the actual year. The average leaf area values
of willows remain in the fluctuation range of previous years.
The terrestrial mollusc communities
on the large part of Slovak inundation area are stabilised on the levels typical
for different variants of lowland forest. Changes registered on certain areas
with young vegetation (decrease of hygrophilous species, increase of species
diversity, penetration of alien species) are assigned to the impact of
silviculture. In case of terrestrial malakocoenoses on the Hungarian side it can
be stated that both, in the inundation area and in the flood-protected area
certain fluctuation can be observed, without any tendency. The fauna varies.
High water levels during the spring
and in the summer hampered the development of macrophyte communities. Wealthier
communities were registered at the end of summer and in autumn. Generally, the
hydrological situation was favourable for the development of true aquatic
vegetation (including several rare species), which suppressed the swamp and
ruderal species. Hydrological conditions in the Hungarian inundation and in arms
on flood-protected area are settled thanks to continuous water supply. The
species number in river arms is relatively high, basically the species
composition of monitored sites is settled as well. Spreading of invasive Elodea
species was insignificant in most branches.
Aquatic malakocoenoses in river
branches on both sides start to show signs of instability and vulnerability.
These communities depend on actual hydrological conditions, and the frequent
decrease of water level linked with oxygen shortage has destructive impact on
them. Decrease of species diversity and abundance can be observed, mainly on the
Slovak side.
Monitoring of the dragonfly community
on the Hungarian side shows rather rich community, which did not show
significant, tendentious changes. Results of the Slovak party constantly show
the presence of less rich communities, which are composed mainly by stagnicolous
and eurytopic species.
In most of the Slovak river branches
rich and stabilised Cladocera and Copepod communities occur, with the dominance
of phytophilous species. Low colonisation of river branches was registered in
summer due to high water stages. Weak representation of these communities in
Hungarian river branches probably reflects the only single sampling in the
summer.
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 mainly caddisflies remains permanently
low in the whole inundation area, however total absence of these communities at
individual sampling sites in the evaluated year was not registered. Regarding
the monitoring results on the Hungarian side abundant occurrence of two-winged
insects (Diptera), aquatic molluscs, mayflies (Ephemeroptera),
bugs (Heteroptera) and caddisflies (Trichoptera) can be stated.
The river branches monitored on the
Slovak side mostly show rather stable, rich in species and abundant
ichtyocoenoses, especially in river arms connected with the Danube. The
ichtyocoenoses in isolated river branches is poorer, because in those situations
with oxygen shortage occur or even they dry out. Rich in species ichtyofauna was
registered on the Hungarian side as well. The species richness is stable and
during last several years it was balanced, significant changes in species
composition were not registered. The most frequent were eurytopic and
limnophilous species, but in river branches used for water supply rheophile fish
species were present as well.
The aquatic fauna of the Danube old
riverbed, which is prevailingly evaluated according to Slovak results, is
characteristic by changed features after diverting the river. The changes in
first years were reflected in decreased participation of rheophilous species (molluscs,
mayflies, caddisflies and fishes) and their replacement by eurytopic and
ubiquistic species. However, further general impoverishment of communities is
registered in last years without any clear reasons. Interaction of several
factors – hydrological, trophical, physical and chemical – is supposed. An
actual change is the spreading of invasive species on the whole Danube stretch
(mainly in the molluscs and fish communities), which is successfully hampered by
original rheophilous species. It have to be noted that the degree of these
changes is probably significantly lower than the results show, since the results
do not represent the status of the medial part of the riverbed, where the
ordinary sampling methods cannot be used.
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.
Experts of both Parties propose to adjust the groundwater limits used for
evaluation in the frame of joint monitoring, due to changes in national
standards concerning the ground water quality.