Hydrological drought within the upper streams of the Šumava, Ore and Giant Mountains: Lessons from the last half century
Abstract
In the context of the continuing warming of the climate of Central Europe, changes in the flow regime of the local rivers are expected, especially changes in the frequency of hydrological extremes, their seasonality and, in the case of droughts, changes in their duration. Increasing average air temperature and evaporation, stagnating precipitation and decreasing water reserves in the snow cover in mountainous areas are likely to further exacerbate the deficits of summer droughts.
This study examines the variability and seasonality of low flows and hydrological drought in fifteen catchments in the Šumava, Ore Mountains and Giant Mountains. The tools of the "lfstat" package in the R environment were used to quantify changes in the selected catchments between 1968 and 2019.
The results showed a substantial increase in the proportion of summer droughts during the study period accompanied by an apparent shift in the average date of drought occurrence towards the beginning of the calendar year. The most pronounced seasonal shifts were found predominantly in catchments with an average elevation of 800-1 000 m a.s.l. across all regions.
In contrast, catchments above 1,000 m a.s.l. showed almost no changes in the low-flow regime over the period 1968-2019. The findings of this study can help identify the potentially most vulnerable natural catchments in terms of summer water scarcity and also in planning mitigation measures in the affected areas.