engleski

THE INFLUENCE OF THREE CROATIAN HYDROELECTRIC POWER PLANTS OPERATION ON THE RIVER DRAVA HYDROLOGICAL AND SEDIMENT REGIME

Since 1975, numerous hydrotechnical works have been carried out on the 60 km long section of the River Drava from Slovenian-Croatian border to the River Mura mouth. Three hydrotechnical power plants with three reservoirs and three long inlet and outlet canals have been built. Massive construction on the Drava River basin and on the river itself during the last centuries, as well as recent climate change and/or variability has caused many different and possibly dangerous changes to its hydrological and ecological regime. Changes in water level, discharge and suspended sediment yield along the River Drava measured in Croatia, downstream of the three reservoirs, during the last thirty to hundred thirty years are presented. The investigation focuses on changes that have occurred during last thirty-odd years, caused by the anthropogenic influences on the River Drava watercourse and its catchment in Croatia and Hungary, and probably by climate change or variability. Methods of rescaled adjusted partial sums, statistical tests, as well as regression and correlation analyses are used in order to explain changes in water level, discharge and suspended sediment yield. There is evidence in the time series of decreases in the minimum, mean and maximum annual water levels and minimum and mean discharges on the lower part of the River Drava. One of the main objectives of this paper is to examine the effect of dams and reservoirs operation on the changes of the downstream suspended sediment regime. The amount of suspended sediment has been greatly reduced, which can cause serious consequences.

water level; discharge; suspended sediment; River Drava (Croatia).

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