7. Monitoring

A typical example of monitoring is the publication ?GABČÍKOVO PART OF THE HYDROELECTRIC POWER PROJECT - ENVIRONMENTAL IMPACT REVIEW (Evaluation Based on two Year Monitoring) [3], published by the Faculty of Natural sciences, Comenius University in Bratislava, in 1995" or reports [7] and [11, 12, 13] "Joint Annual Report of the environment monitoring in 1995, 1996, 1997, 1998" elaborated regularly according to the "Agreement between the Government of the Slovak Republic and the Government of Hungary About Certain Temporary Measures and Discharges to the Danube and Mosoni Danube", Signed April 19, 1995.

The monitoring of the environment should provide information about the impact of various activities and realised measures on the natural conditions, and to compare prognosis with the reality. The impact of the hydropower structures and realised measures is expressed via changes in the hydrological regime of surface and ground water, further through the changes in the zone of aeration (zone between surface and the ground water level), which include the soil horizon with plant roots, and further on through the changes in flora and fauna. The goal of the monitoring is not only to estimate the changes after putting the hydropower structures and measures into operation, but mainly to observe, evaluate, and to manage the water regime in such a way that the processes lead to improving the impact of the hydropower constructions on the various parts of environment. Hydropower structures usually have many technical means for managing the surface and ground water regime and thus also have large possibilities to positively influence environment.

The final aim of monitoring is not to define a "status quo", nor so called conservation or restriction measures, but to provide measures for ensuring development from any point of view, and also with the aim of improving conditions for natural biodiversity and ensuring sustainable development in the broadest meaning of term. Continuous development, which is called "sustainable development", can continue only through improvements in knowledge, development of science, study of natural processes and continuous development of the educational level of inhabitants, including technical disciplines. Monitoring of the impacts of the hydropower structures and man's other activities is a key basis for such processes.

Monitoring is based on sampling and measuring data. There are two general types of sampling, probability sampling and non-probability sampling. Probability sampling means that each item in the population has a chance of being chosen. In non-probability sampling methods not all items have a chance of being included in the evaluation process. This means that the monitoring results may not be representative of the population. The Method of stationary plots might not represent the monitoring area, if monitoring plots are not correctly chosen statistically. Monitoring of such an area as is the area influenced by the hydropower project, should include correctly distributed monitoring plots that characterise all the principal types of impact, and, in addition, also movable monitoring plots which follow the spatial shifting of biotope conditions. The recommendations is to measure in profiles and to map the area of individual components of monitoring. Sampling should, therefore, be of purpose, based on typical structures of communities - taxocoenoses. In the case of flora, it is better to monitor growing parameters of typical representatives of flora. Estimates of biodiversity should refer to the whole area of inundation, or at least to its characteristic units.

The interpretation of monitoring should be transformed into an examination of the whole area, using causal relations between the surface and ground water level and the changes of bio-indicative characteristics. The interpretation of changes in surface and ground water levels should, therefore, be included in the interpretation of the hydropower project impact on biota. A typical example of such monitoring is monitoring of forest.

The impact of the Gabčíkovo structures on biota occurs through changes in the ground water level in the zone of aeration. These changes are manifested through changes in the soil moisture conditions of the zone of aeration, as compared to the soil moisture conditions without the impact of the structures under similar other conditions. If there is an rise in the ground water level due to the construction of hydropower structures, than there is also an increase of moisture in the zone of aeration, or occasionally the moisture may remain unchanged at some depths, but there is in no case a decrease in the moisture caused by the engineering works. Reciprocally, if there is a decrease in the ground water level due to the construction of the engineering structures, then there is also a decrease in the soil moisture, or occasionally the moisture may remain unchanged at some depths, but there is in no case an increase in the moisture caused by the engineering works. Therefore, neither an increase of the moisture in the zone of aeration due to a lowering of ground water level, nor a decrease of the moisture in the zone of aeration due to a rise of ground water level, can happen.

The interpretation of ground water level changes, is therefore, the basis for interpreting biota monitoring data.

In an interpretation of the impact on the environment, a lowering of the ground water level means changes into more hygrophobe(dry) biocoenoses,a rise of the ground water level means changes into the more hygrophilous ( wet) biocoenoses. If the criterion is accepted that hygrophilous biocoenoses are more valuable, more original or native in the flood-plain area, that they have higher biodiversity and higher genetic diversity, then it is very easy to define areas with negative and positive changes, and this according to the changes in ground water levels.