VI.    Proposals for Joint monitoring improvement

VI. 1.   Monitoring of natural environment – present structure and  proposals

Zoltán Hlavatý, Iľja Krno, Mikuláš J. Lisický

In accordance with the intergovernmental Agreement from 1995, the present structure of the monitoring represents a complex and mutually interconnected observation of the abiotic and biotic components of natural environment. The present structure of monitoring is designed on the monitoring of the Gabčíkovo hydraulic structures impacts. It is focused mainly on processes, which depend on the surface and ground water regime changes. 

Surface and ground water 

The essential parts of monitoring are observations of changes in discharges and levels of surface water and ground water levels. Changes in discharge and flow velocity of surface waters, as well as their distribution, can change the surface water quality, which is primarily determined by the Danube water quality inflowing into the Gabčíkovo project area. Surface water quality can further influence the ground waters quality. The oxidation-reduction processes play a significant role during the surface water infiltration into an aquifer. 

The present extent of monitoring of discharges and water levels in the framework of the Joint monitoring makes possible to evaluate the course of discharges within the hydrological years and their distribution in the Slovak and Hungarian territory as well as their changes when leaving the project area. In the same situation is the surface water quality monitoring. Evaluation is based mainly on comparison of inflowing and outflowing water quality (comparison of water quality data upstream and downstream from the Gabčíkovo hydraulic structures). In addition, surface water quality is observed inside of the hydraulic structures in the Čunovo reservoir, seepage canals and in the Danube river arm systems. 

Network of ground water level monitoring wells, in addition to the observation of impact of the water released into the Old Danube and river branch system according to Agreement 1995, enable to measure and to evaluate changes and development of ground water levels in the entire territory of the Žitný ostrov and the Szigetköz area, downstream from Bratislava to Komárno and from the Little Danube to the Mosoni Danube. Development of ground waters quality is observed, in the framework of the Joint monitoring at all significant ground water sources as well as in the zone along the Old Danube. 

Based on data interpretation and experience we can conclude that extent of the analysed parameters, monitoring frequency and density of monitoring network fully satisfy the goals of the Joint monitoring and, in general, it is not necessary to modify the monitoring. In order to evaluate processes having been running in this area before the Joint monitoring started it would be necessary mutually exchange data from the period before 1992. 

Soil moisture 

Changes in soil moisture have a deciding role at transfer of impact of water regime towards terrestrial biota. Deciding factors influencing soil moisture are ground water level and relation between precipitation and evapotranspiration. Since the changes of surface water regime influence foremost the level and fluctuation of ground water level, evaluation of soil moisture changes are focused on relation between soil moisture and ground water level. If there is an rise in the ground water level, than there is also an increase of soil moisture or occasionally the moisture may remain unchanged at some depths, but there is in no case a decrease in the soil moisture because of rising of ground water level, and vice versa. Therefore, neither an increase of the moisture in the soil due to a lowering of ground water level, nor a decrease of the moisture in soil due to a rise of ground water level can happen. 

The soil moisture depends to a considerable degree on the concrete conditions in the monitoring plot (thickness of soil layer, granulometric structure, presence of gravel layers etc.). Therefore it is not possible to extrapolate results from the monitoring plot. On other hand, it is not possible to carry out soil moisture measurements on the entire territory. However, it is necessary to ensure compatibility of the soil moisture observation results with the results of other components of the environmental monitoring. Therefore, on the Slovak area, the soil moisture is monitored on the common permanent monitoring plots of forest stands and biota. From this reason changes in monitoring network of soil moisture are not expected at present. 

Forest stands 

The floodplains on both sides of the Danube are intensively used for cultivation of monocultures of poplar and willows cultivars. The forest stands have been therefore included into the monitoring. The monitoring of forests stands on both sides is focused mainly on the production parameters (increments) and healthy state of the forest. There are some differences in the methods of monitoring in the Slovak and Hungarian side, which result from different monitoring goals. As the results of forest stands monitoring are influenced, similarly as at the soil moisture, by the concrete conditions of the stand, the monitoring in the Slovak side is completed, in addition to the standard monitoring by overall evaluation of the healthy state based on the aerial photography, which started in 1995. In spite of a relatively great effort, it has not succeeded to realize a similar evaluation on the Hungarian side. In the framework of the forest stands monitoring there is necessary to unify the monitoring methods and evaluation modes. Differences should be gradually eliminated in mutual specialists collaboration. 

Biota 

Experiences from the existing Joint Slovak-Hungarian biota monitoring allow to formulate some recommendations referring as the area having been monitored up to present as the functionally connected stretch downstream from Sap. Principles of organization of the biota monitoring, based on experience from the area influenced by the Gabčíkovo hydraulic structures, can be found in [7, 8, 9]. The original concept [5, 6], that all responses of ecosystem could have been monitored in some representative plots, has appeared as unrealistic in the case of strongly migrating animals like fish and birds. In addition, in the case of birds, visiting of the monitoring plots by many specialists taking samples can have a disturbing effect (Černý and  Bohuš in this issue). 

In connection with stabilizing of abiotic conditions, a reduction of frequency of sampling in the existing monitoring plots can be recommended in that sense that the seasonal frequency would be maintained, but the samples would not be taken every year, but in two- or three-year intervals. We again recommend to reconsider the principle of the species inventory in the entire territory once in five years, which was proposed in the past, but has not been realized (Uherčíková in this issue), inclusively of its enlarging from flora also on fauna. This is also valid for the monitoring plots laying outside of the within-dike zone, in which the inventory investigation was carried out in the first year of the monitoring, but which do not belong to the network of the permanently monitored plots. Their annotated list can be found in the paper by Čejka [3]. Changes in the monitoring methods should be consulted with the coordination group for the monitoring of biota on the base of the monitoring reports and proposals on individual specialists. In this way enlarging of gamut of the monitored parameters (for example of the taxocoenoses) could also be proposed if it is evident that some unpredictable change could be better detected. It would be desirable to consult such changes in methods among specialists from both sides. 

In the case of monitoring of aquatic biota, a shift to more modern methods (see contributions by Krno - Bulánková, Kubalová, Šporka in this issue) has been realized. In addition, due to adhering of both states to European Union they are obliged to use methods according to Water Framework Directive. Under condition of maintaining principle of mirror symmetry, as to the extent of the monitored groups, the partial methods of sampling and evaluation should be unified in individual systematic groups so that interpretation of methods is absolutely comparable. This principle was not fully maintained in all monitored groups (for example at aquatic insects). 

The largest reduction of the monitored groups occurred in the course of the monitoring of natural environment in the area influenced by the Gabčíkovo hydraulic structures at the terrestrial zoocoenoses in spite of the fact that more of the monitored animal taxocoenoses have been shown to be effective bioindicators of the monitored problems in the period 1990-1996. Therefore we recommend reconsidering to include again some selected groups into the monitored animal groups. The only group of the terrestrial animals that was monitored without interruption during a longer time horizon was the mollusks. Monitoring of this only terrestrial animal group could be completed by Carabids and Staphylinids, which react very quickly on the environmental changes, but due to their mobility indicate changes in larger areas. A detailed argumentation can be found in the works by Čejka and Šustek in this issue. It is also possible to accept the generally valid proposal by Šustek (l.c.) to monitor the terrestrial animals on two levels: the quantitative level on the existing monitoring plots and the additional qualitative level, focused on reliable bioindicators, which would better cover the mosaic patterns and spatial diversity of the monitored area. 

Aquatic flora 

As the habitats of aquatic vegetation in the monitoring plots on the Slovak side of the Danube are monitored three times a year and as the habitats are not always flooded and overgrown by hydrophytes, it would be desirable to simultaneously apply, out of the Kohler’s method of mapping the macrophytes [4], the traditional phytocoenological sampling in the sense of the Zürich-Montpellier school [2], as well. We recommend to use at this assessment also evaluation of river hydromorphology by means of the method of River Habitat Survey [10], which gives data for proposals of restoration measures and is applied at assessment of environment in more EU countries in connection with implementation of unified methods of water quality evaluation. 

Aquatic fauna 

The existing mode of sampling, processing and evaluation of aquatic biota, especially of the aquatic fauna, does not more satisfy demands of the modern monitoring. The Water Framework Directive (WFD) requires a complex monitoring of the whole benthic fauna – aquatic invertebrates. At assessment of the ecological state of water bodies the autecological characteristics are usesd, on the base of which the indices – the metrics are obtained, which make possible classification of the water bodies. The Framework Directive for assessment of ecological state of water bodies is based on four main groups of aquatic biota (Phytobenthos, phytoplankton, macrophytes, macroinvertebrates and fish). The zooplankton is not included into the WFD, but it’s monitoring, especially in the arms, should unambiguously continue. Until 1997, the macroinvertebrates were monitored in complexity, but later sampling and evaluation of all groups was abandoned. At present only some selected groups are monitored as pars pro toto. In regard to WFD, it will be necessary to modify the methods of taking and processing of samples so that they are made in the same way and only subsequently individual specialists identify them. In this way, it will be achieved that macroinvertebrates from the samples taken in one term and in the same habitats will be evaluated. This has not been provided up to present. The most suitable solution is to make two complex samplings a year (spring, autumn) by a group of hydrobiologists and to complete these samples by samples made by specialists (2-3 times a year). 

In the EU countries, the metrics used for evaluation of results of the aquatic biota monitoring are integrated into one multimetric index and compared with its value, which, however, has not been established for the big lowland rivers like the Danube is, but we expect its establishment in close future. Evaluation of ecological quality of water streams by means of metrics must be based on a complex list of the macrozoobenthos, because absence of some groups (Oligochaeta, Crustacea, Chironomidae, Simuliidae) can bias the final results of evaluation of the ecological quality of the water. The unified methods are to be used for the whole macrozoobenthos, inclusively of evaluation of abiotic environment. As mentioned above, monitoring of macroinvertebrates must be based on taking of one common sample given, after its sorting, to respective specialists for identification. Taking of samples should be modified according to methods required by the WFD and, according to possibilities, harmonized with the Hungarian side. As sampling in the medial zone of the main channel and arms requires expensive equipment, we propose to take samples for the needs of monitoring only in the ripal and littoral zone by means of the methods suggested by the consortium AQEM and STAR. At this method, the kick net is used and altogether 20 samples from the total surface of 1.25 m² of different sediments are taken. Estimation of sediments is made on a stretch of 100 m so that a representative samples is obtained. This mode has been published in the methodical procedures proposed by the AQEM Consortium (2002). In Slovakia the same mode of sampling is already used at sampling in the reference and monitoring plots for the needs of WFD in Slovakia. 

At monitoring of fish it would be more desirable to catch in the whole area of the respective species, hence all habitats inhabited by the respective species in the monitored territory, not only in the determined monitoring plots. Probably just from the reason that the Old Danube is monitored on the plots set for the whole biota, some fish species are not regularly recorded at catching by the electrical aggregate in spite of the fact that they do occur in the Old Danube channel. They prefer other habitats than those represented by the monitoring plots at Dobrohošť and Istragov. They migrate in the old channel and river arms according to water temperatures, discharge and other environmental factors. Therefore, even three catches in a site a year must not be representative neither for the commonly occurring fish species. 

At evaluation of changes in the biota in individual monitoring plots, it is also necessary to use the existing chemical and physical parameters of the abiotic environment, inclusively of the height of level of the surface and ground water, water temperature, pH and content of nutrients. It is necessary to provide a continual and long termed monitoring of the abiotic parameters so that a sufficient amount of data for evaluation of realized measures and for proposals of other measures is available. 

Significance of monitoring of aquatic biota still will increase as in the case of realization of mutual interconnecting of the arms systems in each side of the Danube as in the case of interconnecting of the arms systems with the old channel. 

Bird fauna 

Although monitoring of birds is not the objective of the Joint monitoring, we suggest to include the data obtained at the regular bird census or at occasional observation of some bird species into evaluation in certain time intervals. 

In the case that bird fauna monitoring would be taken in consideration in the future, we recommend to make monitoring thematically in two areas (Bohuš in this issue):

1.   Monitoring of dynamics of the mosaic of habitat patches and succession stages by means methods of coenological methods (spot mapping or point method/IPA).

This monitoring should be focused on the monitoring plots representing the main types of aquatic and terrestrial habitats in the territory and their succession stages, preferably in the breeding season. The monitoring plots should include the whole gamut of aquatic habitats, from the active arms to the terrestrialized oxbows, gravel banks restored by the dynamical hydrological regimen, succession stages of floodplain forests from the naturally regenerating stands to the stands in phase of disintegration. The monitoring should be carried out in the possibly restored area of the existing remnants of the Danube arm system, as well as in the stretch downstream from the mouthing of the tail-race canal and the downstream tributaries (Vážsky Dunaj, Hron, Ipeľ). The „difference“ species with a close habitat valence like Ardea purpurea, Ixobrychus minutus, Rallus aquaticus, Porzana porzana, Podiceps cristatu, Tachybaptus ruficolli, Alcedo atthis, Charadrius dubius, Hippolais pallida, Sylvia communis, Sylvia nisoria, Hippolais icterina, Musicapa striata, Phoenicurus phoenicurus, Ficedula albicollis, Certhia sp. and some cavity nesting species like Strix aluco, Ciconia nigra etc. can be used for evaluation.

2.     Complexe evaluation of function of the ecosystem.

In this case, the data collecting should be focused on the species with affinity to a wider gamut of feeding and breeding habitats (waterfowl, especially of the order Anseriformes; Phalacrocorax carbo, Haliaëtus albicilla) and on use of results of the regular bird census in the respective stretch of the Danube and water bodies of the Gabčíkovo hydraulic structures. In this case, the line and point methods could be used, which are applied at the running census programs, which can be immediately continued (winter census of waterfowl, census of the wintering population of the Sea eagle). 

Proposal of the common monitoring of the natural environment in the stretch between Sap and Štúrovo 

As there is a good experience from the common Slovak-Hungarian monitoring, it would be desirable to introduce a similar monitoring also in the stretch Sap – Budapest. Extent and content of the monitoring should be at least identical with the extent of the monitoring carried out according to the intergovernmental Agreement from 1995. It would be desirable to analyse the existing proposals or a new proposal by a group of selected specialists. 

In regard to the fact that the monitoring of benthic invertebrates has become one of the crucial indices of the new legislative for monitoring of surface waters in Slovakia and in EU, we propose, in interest of evaluation of the Danube, to enlarge as soon as possible the network of the profiles having been monitored up to present by the profiles downstream from Číčov (Zlatná na Ostrove), downstream of mouthing of the Váh river (Iža) and downstream of Štúrovo (upstream from Chľaba), as well as possibly downstream of the mouthing of the Morava river (Devín). At present it is necessary to focus on a detailed investigation of macrozoobenthos in the localities influenced by the Gabčíkovo hydraulic structures. We propose to replace the control localities Istragov and Sporná Sihoť by other localities situated more downstream, in the places where influence of the hydraulic structures is not expected (see above). At present, these two localities do not satisfy even with reserve the criteria of the reference localities (strong fluctuations of water level in the Danube and adjacent arms. Values of these two localities as reference localities would change if their artificial supplying by water is solved.

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