PART 8
8.1. Conclusion statements
After considering the evaluation of
environmental monitoring results in hydrological year 2006 the Nominated
Monitoring Agents conclude:
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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In connection with changes in methodology in water quality
monitoring an overall evaluation of the preceding period is recommended.
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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.
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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.
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The Parties propose to make an
overview of evaluation methods accepted in both countries in connection with
the Water Framework Directive.
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