engleski

Discharge response to precipitation and temperature change in the lowest part of the Drava river basin, Croatia

The Drava river is one of the largest rivers in central Europe, which flows through five countries. The purpose of this researche is to assess the influence of precipitation variability on hydrological parameter in the study catchment. The analysis aims at investigating trends in observed precipitation amount, frequency (number of precipitation days, Rd ≥ 0.1 mm), intensity (daily intensity) and mean discharge, using long-term records 1926-2004. Meteorological gauging station Osijek (H=328 m asl,  =45°32',  =18°44') and hydrological station Donji Miholjac ("0"=88, 57 m asl,  =45°48',  =18°21') are located in the lowest part of the Drava river basin in the very southern part of the Pannonian lowland. Linear trends were estimated for annual, warm half-year (April-September) and cold half-year (October-March) data series, and tested for significance by means of the nonparametric Mann-Kendall rank statistics t (Mitchell et al., 1966, Sneyers, 1990). For the series, which showed the significant trend, a progressive analysis of the time series by means of the statistic u(t) was performed in order to determine the beginning of this phenomenon by means of a sequential analysis (Sneyers, 1990). In order to eliminate short-term fluctuations, the noise was taken out of the data series by means of the weighted 11-year binomial moving average filter. The anomalies show the large variability of the meteorological parameters as well as the discharge. In the cold half-year trends in precipitation and discharge indicate decrease and at the same time increase in temperature. All of them are not statistically significant at the 95% level, except frequency of precipitation days. This series show significant decrease since 1981. Interannual variability in all parameters is yet more pronounced than in the warm half-year. In the warm half-year, during the second half of the 1930s' and in the 1940s' large positive temperature anomalies are present. At the same time precipitation anomalies are negative. These reflect in negative discharge anomalies. At the end of the observed period increase in temperature with the simultaneous high precipitation interannual variability is associated with negative discharge anomalies, as a strong impact of the groundwater resources.

climate change; discharge; warm and cold half-year; the Drava river; Croatia

nije evidentirano