Potsdam. According to calculations by the German Weather Service (DWD), March 2023 was the wettest March since 2001. With more than 90 liters of precipitation per square meter, there was almost 60 percent more precipitation than the average for the reference period from 1961 to 1990. According to this, the average rainfall in March is 56 .5 liters per square meter. From a statistical point of view, meteorologists are already registering April as having a lot of precipitation.
Does this mean that the issue of water shortages, which many regions in Germany suffered from in recent summers, is no longer an issue? “You shouldn’t let the current rainfall fool you,” says Fred Hattermann, head of research on hydroclimatic risks at the Potsdam Institute for Climate Impact Research (PIK). “Unfortunately, the all-clear can’t be given for a long time.”
Only upper soil layers moist
The hydrologist explains that it is too short-sighted to draw conclusions about the groundwater level from large amounts of precipitation. “The soil is well moistened in the upper layers. But the groundwater level, which is many meters below the surface of the earth, is not even at the level of last year in many regions.” East Germany is particularly affected, but also regions in southern and western Germany. “We have a rainfall deficit of one year. So it would have to rain for a year.”
Fred Hattermann is deputy head of the Climate Resilience department, he heads the “Hydroclimatic Risks” working group at the Potsdam Institute for Climate Impact Research (PIK).
© Source: PIK / Klemens Karkow
longer growing season
The lack of rain is only one problem when it comes to the drought. “You always look at the precipitation, but you often forget that global warming also plays a major role,” explains Hattermann. “The average temperature in Germany has risen by two degrees since pre-industrial times. This means that the winters are shorter and the growing season is longer.” The plants would therefore draw water from the soil for their growth earlier and earlier in the spring and longer in the autumn.
“Due to the increasing heat, evaporation has also increased,” says the hydrologist. This continuously drains the water reserves. “On average, it would have to rain more and more to compensate for the increasing evaporation with warming.”
Air conditioning check
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What helps against drought?
If rain alone isn’t enough, then what helps to make Germany better equipped to deal with drought? There are a variety of measures to act, says Hattermann, who names three main ones: “On the one hand, we need greener cities: Areas would have to be unsealed so that rainwater can seep away and the groundwater can be replenished.” In addition, rich greenery would lower the temperature in the cities. “Even the planning must be consistently climate-friendly – if necessary, through appropriate conditions.”
“Second, she should Agriculture be adapted: with hedges as wind breakers, if possible shade against strong evaporation,” explains the scientist. You also have to grow new, adapted varieties that, for example, require less water to grow.
Last but not least, you have to “in the forestry carry out a forest conversion”, says Hattermann. “We have far too many spruce forests. But the classic coniferous forest uses significantly more water in winter than a deciduous forest.”
Water from the Elbe for the Spree?
How does the expert view the future? “One does not know exactly how it will develop.” That also depends, for example, on how the wind systems over the Atlantic, which is our “weather kitchen”, change under climate change.
“But if the regional drought continues to increase, you have to think about diverting water from other regions.” There are already considerations of using water from the Elbe in winter to support the Spree inflow to Berlin. After all, you need around eight cubic meters of water per second into the city so that the water can continue to flow there. This is already difficult today in the dry season.