Detection of changes in flow variability of the upper Danube between 1876-2006

Abstract

It is widely acknowledged that global warming will result in an increased extremality of hydrological phenomena. As for streamflow it is anticipated that duration of low-flow conditions and flood frequency will both increase. Approving this hypothesis by statistically evaluating daily runoff characteristics depends on the availability of long and homogeneous data series. The aim of this paper is to analyze the change of the average daily flows of the Danube at Bratislava for different subsets of the period 1876-2006. The statistical tests did not reveal any increase in the extremality of daily runoff over the period 1876-2006. On the contrary, variability of daily flows of the Danube River decreases. Over the last 30 years streamflows increased in the winter-spring season and decreased in the summertime, compared to the past periods. This can be explained by the higher air temperature in the headwaters. A warmer climate causes an earlier onset of snowmelt in the winter-spring season, thus less runoff is observed in the summer with higher rates of precipitation.