CLIMATE CHANGE AND ITS IMPACT ON QUALITY OF AQUATIC HABITAT.

At the present, the issue of climate change is a very frequent term especially in the relationship with global warming. These changes are reflected in the full range of ecosystem. The paper evaluated the prognosis of climate change and its impact on the quality of aquatic habitat at a particular section of the Váh River. Based on the calibration of parameters by hydrological model Hron changes in air temperature, precipitation and flow at the final profile of Váh River in the future periods (2021-2050 and 2071-2100) were evaluated. The results indicate the change of flow in the future, which is mainly due to changing rainfall. More important than the flow rate is the distribution of flow over the year. Therefore, the results were evaluated as the long-term average values in each month and three different climate change scenarios were compared. For better review of the future changes, the changes in individual hydrologic parameters during the period of 2071-2100 compared to the period 1961-1990 (which is considered as a reference period) were assessed. The results show that not all regional models, although based on the same emission scenario SRES A1B (IPCC, 2000), show the same outcomes. The article compare three models and their results are analyzed in terms of flood control and maintenance of the quality of aquatic habitat in the period of minimum flows. For larger rivers, it is assumed that climate change would not have significant impact on the biota of the river. Threatened will be smaller mountain tributaries where the flow decreasing and temperature increasing can significantly affect the aquatic ecosystem. Specifically, these changes were examined at Hybica River that is a tributary of the Váh River (the largest left tributary of the Danube in Slovakia). From the measured data it was found that the minimum flow rates and the most demanding conditions for the biota of the river occur in August. Based on the measured data of air temperature and precipitation at individual stations from 01/11/1994 to 10/31/2002 the forecast of changes in the minimum flow in the month of August was modeled. The mean monthly values as well as minimum daily flows were evaluated. For modeling the flow impact on the quality of aquatic habitat the data from the Department of Land and Water Resources Management were used. There were evaluated 43 rivers and 52 representative sections of mountain rivers in Slovakia. Measurements are adapted to the requirements of modeling the aquatic habitat quality by the methodology IFIM in the program RHABSIM (detailed topographic, hydraulic and ichthyologic measurements on selected reference sections of rivers), so the forecast of impacts of climate change on the quality of aquatic habitat will use the above methodology and model. The modeling results of the impact assessment of climate change on the quality of aquatic habitat of the Hybica River shows that minimum flows will decrease in summer, which is critical for the biota of the Mountain Rivers. By reducing the flow volume the suitable habitat is reduced and simultaneously the reduced flow allows quickly overheat of the water, which negatively affects the aquatic biota. It could be concluded that climate change can significantly influence the quality of the ecosystem of the Hybica River. A similar trend can be expected for all mountain rivers within the Váh River basin. [ABSTRACT FROM AUTHOR]