engleski

Trends and variability in precipitation and discharge in the Drava River basin, Croatia

Previous study on climate conditions in the Croatian Drava River basin, including average annual cycle of climate parameters and water balance components, pointed at the strong influence of air temperature, relative humidity and precipitation on water balance components, as well as on the dominant influence of precipitation on mean discharge. This paper deals with time series analysis of precipitation parameters and mean discharge, using long-term records over the 1926-2004 period at hydrological station Donji Miholjac and meteorological station Osijek. Linear trends show decrease in annual, warm and cold half-year precipitation amounts and number of precipitation days and mean discharge, and practically no change in daily precipitation rate. Due to non-parametric Mann-Kendall test with a 5% significance level, statistically significant decreasing trend has been detected only in the number of precipitation days for the cold half-year. It appears since 1981 according to the Sneyers progressive trend test. A statistically significant decrease in the variability of mean annual discharge and precipitation days, and increase in the variability of cold half-year discharge is present in the long-term period. The trend analyses of successive 30-years sub-periods, whose beginnings are shifted by ten years, indicate exchanges of positive and negative annual precipitation and discharge trends.

climate change; discharge change; half-year period; trend; variability; the Drava River; Europe

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