Impacts Of Regional Climate Change On Hydrological Drought Characteristics In Headwaters Of The Ore Mountains

Changes in the frequency, magnitude, and seasonality of hydrological extremes are one of the expected consequences of climate change. Recent years suggested an increasing risk of drought occurrence and restricted water supply even in usually humid mountain regions. Our research is focused on the evaluation of regional climate change and its effect on hydrological drought characteristics in headwater areas in the Ore Mountains along the Czech/German border. The main aim was to evaluate and compare streamflow regime changes and trends in long-term hydrological and climatic time series within selected sub-catchments of the Svatava (Zwota) River, the Rolava River, and the Nacetinsky Brook (Natzschung). A comparative statistical analysis for the 1967-2018 period was performed using various homogeneity and trend tests. Longer runoff time series with earlier beginnings were examined for two catchments as well. The results pointed to significant, continuous warming in the region which is accompanied by decreasing trends in snow cover depths in the colder half of the year. Drought indices based on runoff data were derived in the Indicators of Hydrologic Alterations (IHA 7.1) software environment. The seasonality of hydrological drought occurrence changed markedly after 1992, when most severe drought events started to concentrate between August and October in the study area. Increasing trends in deficit volumes were found in two catchments characterized by lower elevation. Furthermore, there was a significant decrease in average and minimum flows in spring and summer months in all catchments observed between 1967 and 2018 despite relatively stable amounts of precipitation and land cover.