Martin Rulík: The impact of drought on surface and groundwater will be enormous this year

Field in Grygov
Photo: Martin Rulík
Monday 11 May 2020, 12:00 – Text: Šárka Chovancová

Another significant decline in groundwater levels and flow in rivers and streams in the Czech Republic this year will be caused by a drought that struck in the spring – much earlier than in previous years, due to poor snow cover and a lack of rainfall. Drought reduction cannot be expected in the coming months, when, on the contrary, the precipitation deficit should widen further. This has been brought to our attention by Martin Rulík from the Department of Ecology and Environmental Sciences of the UP Faculty of Science.

“Meteorological forecasts for the coming months do not anticipate more rain, so the impact of drought on surface and groundwater will be enormous this year. There will be significantly below-average flow in watercourses,” warned Rulík.

In terms of the lack of moisture in the soil and flow in rivers and streams, this spring is worse than the previous two years. “The drought in mid-April this year was comparable to the situation we observed last year at the end of April or the beginning of May. It follows that the drought has shifted more to spring, bringing with it all the negative effects,” said Rulík.

Compared to 2018 and 2019, the water supply in the snow in the mountains was up to three times lower. In addition, the snow began to melt in February, relatively soon. “This was followed by a period without significant precipitation. Although there was increased flow in watercourses at the time of melting, groundwater was not significantly affected by this. At present, the levels are significantly below normal,” added the hydrobiologist.


The summer months should be above average in temperature

According to Rulík, meteorologists’ forecasts for the next part of this year are not optimistic. “Precipitation is expected to be less frequent, very dry weather is expected with extreme heat in the summer, when temperatures are expected to reach 40°C,” he warned. However, due to the mild winter, groundwater reserves have not been replenished and their levels are below average. “Therefore, it can be expected that the flow in watercourses will be much below average, or even none at all,” he warned.

Very low flows are already visible on larger watercourses, such as the Morava River and the Elbe. “Heavier precipitation, for example during storms, can occasionally raise flows for a shorter period of time, but otherwise very low flows will prevail,” he said. The Czech Republic has been struggling with drought for a long time. For example, in South Moravia, there is already such a precipitation deficit as if it had not rained there at all for a year, according to Rulík.


Groundwater status will be saved only by heavier rains and winters richer in snow

Rulík assumes that the average total rainfall in the Czech Republic will continue to be approximately the same as in previous years. “However, their distribution will change significantly during the year. Extremes will be more frequent, i.e. torrential rains, when in a short time it rains as much as it once did in one month,” he said.

Due to the rising temperature, the evaporation of water from the landscape and the output of water through plant surfaces will also increase. According to Rulík, the hydrological situation could be improved only by heavier rains and winters richer in snow, which is not realistic. “It now rains an average of 680 mm annually. In order to improve the state of groundwater for next year in particular, it would have to rain at least twice as much, and in the winter it would have to snow and last at least until March 2021 and then gradually thaw. But that is, of course, just a theoretical calculation and wishful thinking,” he said.

It is therefore necessary to introduce measures to increase the amount of water retained in the landscape. “The only source of water for the Czech Republic is precipitation. So the more water we capture in the landscape, the more we will have. So that the water that rains stays at the point of impact and soaks into the soil and then into the groundwater depends on the condition of the landscape,” he said.


Restart the landscape

However, the Czech landscape has been considerably devastated over the last 60 years and lacks sufficient retention structures to slow water runoff. “It is necessary to ‘restart’ the ‘small’ water cycle in the landscape. Primarily, a change in management in our landscape is necessary, i.e. above all a change in management on agricultural land and in forests,” mentioned Rulík.

Retention structures that would slow down the outflow of water and the removal of soil from the fields include, for example, small woods, seepage meadow belts or alleyways of trees between the fields. “Forest management should also be improved and the revitalization of our regulated streams is needed in order to slow the outflow of water away from the landscape. It would also help to increase water areas in the landscape, which would strengthen the small water cycle. During evaporation and plant transpiration, water vapor removes heat from the environment, thus cooling it. Therefore, in a landscape with plenty of water, the climate and temperature are more amiable than in a landscape without water,” he explained.