PART 8
8.1. Conclusion statements
Based on the results of
environmental monitoring in the year 2010 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 2010 was 2098 m3s-1, which belongs to
average flow rates on the Danube. Considering the course of water levels and
flow rates during the hydrological year 2010 it can be stated that no
extraordinary values occurred, one high flood however occurred at the beginning
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 414.4 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 2010 was 472.9 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 5 days (reduction to
600 m3.s-1). According to this the average annual flow
rate in the Danube old riverbed corresponded to 449.0 m3.s-1,
which represents 108.3 % of the amount required by the Agreement. This
means that the obligation of the Slovak Party was fulfilled. The discharge into
the Mosoni branch of the Danube was 37.91 m3.s-1,
which represents 88.2 % of the agreed amount. Lower annual average
flow rate discharged into the Mosoni branch of the Danube in 2010 was caused by
long-term technological breaks due to maintenance and repair works on turbines
and the intake object itself. 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 2010 was similar as
in previous years. 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. The quantitative ratio of ionic composition of
the surface water shows high stability in last years. 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 similar or
slightly higher concentrations of nitrates and total phosphorus were registered
in comparison with the previous year, however they did not violate the
long-term tendency of pollution decrease. Oxygen conditions in the year 2010
were very good; the organic pollution represented by CODMn was lower
in comparison with the previous year 2009, in case of BOD5 it was
similar or slightly higher. 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
copper, the lowest in case of mercury, cadmium and lead. A large 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 at the sampling site at
Čunovo/Rajka follows the water quality in the Danube, while the water quality
on 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.
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 is characteristic for seepage
canals, which results from its groundwater origin.
The
monitoring of biological elements of the surface water quality 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
state, and according to phytobenthos from II. to III. class, thus from good to
moderate state. Based on the monitoring results of biological quality elements
and considering the evaluation of physico-chemical elements and evaluation of
other specific pollutants (see the Hungarian National Report in 2010) the
ecological status of water bodies 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. Macrozoobenthos and
phytoplankton were evaluated. Saprobe indexes varied in ranges corresponding to
beta-mezosaprobity, thus environment that offers suitable living conditions for
a wide scale of organisms. An exception in the year 2010 was the sampling site
No. 311 in the reservoir, where in case of the saprobe index of macrozoobenthos
beta-alpha-mezosaprobity occurred.
Considering
the sediment quality evaluation in 2010 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 organic contamination on the Hungarian side all values were lower than the
Threshold Effect Level (TEL). On the Slovak side there were concentrations also
within the range >TEL and <PEL, but all fluctuated close to the TEL
limit. In case of inorganic contamination several concentrations falling into
the range >TEL and <PEL, when the unfavourable effect on biological life
occurs occasionally, were found on the Slovak and Hungarian territories. The
highest concentrations occurred in case of zinc, when at sampling sites at
Vének and in the Ásványi river branch values closer to PEL limit were recorded.
Other concentrations of heavy metals varied closer to the Threshold Effect
Level (TEL). The highest concentrations of heavy metals occurred at sampling
site No. 311 in the reservoir and in the Mosoni Danube at Vének (No.
1141).
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 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 measures realised according to the intergovernmental
Agreement, a significant increase in the ground water levels occurred for low and
particularly for average flow rate conditions in the Danube. The increase was
reduced in the upper part of the Szigetköz region and around the reservoir in
last two years due to adverse changes in sediment transport regime in the
Danube, that are probably related to measures realized on the Austrian stretch
of the Danube upstream of Bratislava. A decrease in the ground water
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 ground water levels in the
inland area of Szigetköz. In general the overall situation in last two years is
slightly worse compared to the previous period Generally, the
overall situation in last two years has deteriorated slightly
in comparison with the previous period,
and probably it will be needed to take
some action in the reservoir.
The monitoring results also 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 Ásványi river branch system and in
the Bagoméri river branch systems 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 ground water 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.
4. According to results of long-term water quality monitoring at 16
groundwater quality observation wells on the 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 constantly exceed the
groundwater quality limits on most of observed wells. In general it can be
stated that the content of nitrogen form parameters and parameters indicating
the presence of organic matter (COD) 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 are
higher in wells at Győr region. In these wells the iron and manganese contents
exceed the drinking water quality limit values or oscillates around them. The
iron and manganese concentrations are lower in waterworks, which are drawn from
greater 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 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 mostly
satisfies the agreed groundwater quality limits. The exceptions are the
waterworks at Bodíky and at Kalinkovo. At Bodíky waterworks the manganese
exceeds the quality limit in each sampling and occasionally occurs a higher
concentration of iron as well (one value in the year 2010) At Kalinkovo
waterworks sometimes 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. The groundwater quality at waterworks is
stable in long-term. In the evaluated year 2010 no considerable changes of the
groundwater quality were registered. The groundwater quality in observation
objects mostly reflects local influences.
The
groundwater chemical composition in observation objects is similar to the
groundwater chemical composition of the waterworks in their neighbourhood.
5.
The soil moisture content at the beginning of the vegetation period
was slightly lower in comparison with the previous year. It increased
significantly in the layers down to 1 m depth thanks to the precipitations
amounts high above average, especially in the first half of April and in May.
Huge precipitations occurred also from July to September, thus the soil
moisture values were higher till end of the year in comparison with the
previous year. During the flood significant part of the inundation area was
flooded. After passing the flood the soil moisture values also reached higher
values in comparison with the previous year. The highest soil moisture values
were recorded after passing the flood wave, in the second half of June or at
the beginning of July. The groundwater level reached similar levels as in the year
2009. Minimal values of soil moisture were registered either at the end of the
winter period or at the end of the year. Generally, the soil moisture in the
year 2010 had developed favourably.
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 is
stable during the whole observation period. Since the year 2004 slight increase
in the soil moisture content can be observed, while the ground water level
position and fluctuation remained unchanged. In the hydrological year 2010
natural flooding of inundation occurred in June. The highest flow rate reached
8071 m3s-1, which means that large part of inundation
area was entirely flooded. The soil moisture content at the beginning of the
year was rather low, especially in the layer below 1 m depth. Thanks to
precipitation amount in January and in April and May, which were highly above
average, the soil moisture content significantly increased. The lowest values
in the layer down to 1 m depth were mostly recorded during summer months. The
lowest values in the depth interval from 1 to 2 m were mostly registered at the
end of the year. The maximal values on most of monitoring sites occurred after
flooding in June, but on some in September, when the flow rate in the Danube
old riverbed was increased again. The soil moisture content at the end of the
year mostly reached higher values compared to 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 higher than in the previous year. The
maximal values were higher on a part of monitoring areas, while they were lower
on others, in comparison to the previous year.
6. The development of forest stands according to the results of Slovak
Party in 2010 did not go beyond the existing tendency. The growth
characteristics in young or middle-aged forest stands are basically stable. The
best height increment according to results of quality classification show
stands exceeding the age of 10 years and approaching the culmination age.
Stands with the “Pannonia” poplar clones in the age 5-10 years are
characterised by stable growth increment at moderate level. The growth
increment of young stands that are below the age of 5 years is relatively slow
in first years of monitoring, however, continuous improving of their state and
stabilisation of growth increment is registered. According to the results of
girth growth increments in the year 2010 a significant decrease of width
increment intensity was recorded in all evaluated areas, and the zero weekly
increment occurred several times. The monitored cultivated poplar stands were
healthy. Due to high relative humidity after frequent rainfall slight increase
of fungal diseases on almost all areas was registered in early summer, but in
spite of this their spreading was sporadic. Further spreading of fungal
diseases in the coming months was not registered. The occurrence of foliar
pests in the observed stands was only sporadic during the whole growing period.
Although the hydro-meteorological conditions of recent years have been quite
favourable it is necessary to take into account the effective use of existing
weirs in the river branch system for ensuring artificial flooding in case of
absence of natural floods. In region of Istragov it is necessary to resolve the
recharge of the river branch system by water. The impact of riverbed erosion
downstream of the confluence of the Danube old riverbed and the tailrace canal
has to be monitored.
Based
on the detailed analysis of actual growth characteristics of forest stands on
the Hungarian side it can be stated that no change have been registered in the
existing growth tendency. The growth of trees in the evaluated year developed
favourably. No slowdown in the evaluated year 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, which is in
harmony with results on the Slovak side. Detection of possible causes would
require a detailed analysis.
7. The hydrologic conditions of the evaluated year were favourable,
there was enough precipitation and a large part of the Danube inundation area
was flooded. Phytocoenoses on the Slovak side can be regarded stabilised,
changes in certain young stands can be assigned to gradual closure of treetops.
The phytocoenoses observed in the Hungarian inundation were influenced by
flood; the coverage of herb layer was significantly decreased temporarily.
The
terrestrial mollusc communities on the large part of Slovak inundation area are
stabilised on 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 remains variable.
The
observed river branches were characteristic by increased water level in the
evaluated year. Generally, the hydrological situation was favourable for the
development of true aquatic vegetation (including several rare species), which
suppressed the swamp and ruderal species. The unfavourable fact is the
spreading of invasive species Elodea nuttallii at some sites. The
growing conditions in the Hungarian inundation and in the flood-protected area
thanks to the continuous water supply, remained unchanged in recent years,
therefore the species composition and the abundance of species is stable. 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 malakofauna in last years. The reason for decline of native species from the Danube is not yet
clear. This is probably an interaction of several factors – hydrological, trophical,
physical and chemical. In the river branch system on the
Slovak side destruction of aquatic malakocoenoses is registered despite the
heterogeneous nature of the river arms, sufficient size of biotopes and good
conditions for its development. In river branches on both sides start to show
signs of instability and vulnerability. The relatively rich communities of
aquatic malakofauna on the Hungarian side did not showed significant
differences in comparison to previous years; they are stable and depend on
actual site-specific conditions.
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, but significant – trend changes were not registered.
Results of the Slovak party constantly show the presence of less rich
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.
In
most of the Slovak river branches rich and stabilised Cladocera and Copepod
communities occur, with the dominance of phytophilous species. However, the
actual results indicate negative changes. Decrease in species number and
abundance was registered in both communities. Sampling of planktonic
crustaceans on the Hungarian side was carried out only once a year; the number
of recorded species is therefore rather low. Several rare species were
registered in the evaluated year as well. The highest species diversity was
repeatedly registered in the Lipóti marsh, and this site was also
characteristic by the highest abundance in the evaluated year. Results obtained
from monitoring sites in the flood-protected area from the long-term point of
view present a high diversity and stability of biotopes.
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. Surviving of more abundant
communities, however, can be supposed in hard-to-get medial sections of the
flow. Mayfly communities consisted of 2-3 species with low abundance, caddisfly
communities were even poorer, at most of sites no representative was recorded.
The
ichtyofauna in the river branches on the Slovak side is rather stable, rich in
species and abundant, 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. 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 recorded. The
most frequent were eurytopic and limnophilic species, but in river branches
used for water supply rheophilic fish species were present as well. On several
sites permanent occurrence of the invasive Ameiurus melas was
confirmed.
Based
on the results of Slovak and Hungarian observations the ichtyocoenoses 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 representatives. Their expansion is hindered by indigenous rheophilic
species, which find their refuge in the medial part of the river.
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.
Hungarian experts suggest discussing a slight change of the method
for average annual flow rate calculation, which would consider the
circumstances that occurred in the hydrological year 2010.
2.
Considering the differences in the evaluation of surface water quality
according to national methodologies, experts of the Slovak Party propose to
discuss and reconsider the evaluation method of surface water quality, which was
agreed by both Parties on the meeting of Monitoring Agents on April 25, 2007..