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Popular Science: Drought comes earlier

Hydrological fluctuations have been occurring in recent decades and they currently manifest primarily in significant and prolonged droughts. Changes in the hydrological cycle have a major impact on both water supply and the entire ecosystem. Vojtěch Vlach and Milada Matoušková from the Department of Physical Geography and Geoecology, Faculty of Science, Charles University together with Ondřej Ledvinka from the Czech Hydrometeorological Institute know well about the severity of the hydrological situation. Therefore, they explored in detail what has happened in terms of hydrological change in the areas of Czech mountains in recent decades.

Difficult tasks caused by climate change are often hard to handle. Adaptation to the changing climatic conditions and prevention of more severe impact on the landscape, society and the entire ecosystem are very important today. Knowledge of past and current climate conditions is necessary for predicting the future evolution and implementing effective measures to counter negative effects.

Drought is now one of the largest hydrological risks, which is very difficult to cope with. In a recent study, scientists therefore focused on the analysis of long-term variability and seasonality of low flows in fifteen river catchments of the three different regions of our border mountains - namely the Bohemian Forest and the Bavarian Forest, the Ore Mountains, the Giant Mountains and the Broumov Highlands. The reviewed period (1968–2019) was long enough to discern the trends and significant changes.

Low flows have a negative impact not only on society and the surrounding landscape, but also for the river fauna and flora. The Upper Blanice river, which is exceptional by the occurrence of the endangered freshwater pearl mussel (Margaritifera margaritifera), was one of the study river basins.

Hydrologists have used many tools and techniques to evaluate the changes in the flow rate in terms of long-term variability and seasonality. At the same time, they focused on the lowest flows that occur mainly in winter and summer months and can cause major problems with water supply, especially if they last long.

The study results show serious problems, especially a substantial increase in the proportion of summer low flows during the analysed period, a shift in the average date of low flow occurrence towards the beginning of the year and an increase in the duration of drought episodes. At the same time, the altitude and the overall river catchment orientation have fundamental effects. The most significant changes were noted in catchments oriented mainly to the southwest with an altitude of about 800–1,000 m. On the contrary, the catchments with terrain above 1,000 m.a.s.l. remained mostly stable in the last fifty years.

Although the hydrological situation in our country has improved slightly in the past year, groundwater reserves are not fully refilled and the situation is still critical in certain areas, especially in Western Bohemia. Moreover, it is possible to expect more severe drought events in the future. In addition, the current study shows that the hydrological situation in our territory is spatially different. It is necessary to not to rest on one’s laurels and take decisive measures for proper water management in the landscape depending on the state of the specific catchment condition.

Vlach, V., Ledvinka, O., Matouskova, M. (2020): Changing Low Flow and Streamflow Drought Seasonality in Central European Headwaters. Water, 12, 3575; doi: 10.3390/w12123575.

Kateřina Fraindová

Published: Mar 29, 2021 06:55 PM

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