When the Drought is Balanced
The year 2022 was very sunny, hot and dry: it rained a lot in the new year, especially in the west and south. On the contrary, is the water table level rising? The first half of January was wet: it rained a lot in Germany, especially in northern Germany, and precipitation in the previous January exceeded the long-term climate average for the years 1991 to 2020, in some cases significantly with 60 to more than 100 liters per square meter. This corresponds to up to 140% of the average climate.
In the south and east, it dropped from 30 to 80 percent of usual precipitation, which equates to 10 to 40 liters per square meter. In western Germany, for example on the Moselle and Rhine, which are currently experiencing minor flooding, the January monthly target of 60 to 75 liters per square meter has been achieved.
However, it is not enough to draw conclusions about groundwater levels directly from large amounts of precipitation and severe flooding. Soil moisture on top of the soil takes a long time to affect groundwater. Depending on soil conditions, the water table here in Germany is several meters below the surface.
Drought stress in Northern Germany
In fact, during the winter, when the plants are dormant, the soil is usually well moistened. And in most regions of Germany there is already enough water in the topsoil.
The situation is different in northern Germany, particularly in Saxony-Anhalt, in southern Brandenburg, in northern Thuringia – and sometimes in Lower Saxony and North Rhine-Westphalia: soil moisture is still low below a depth from 40 to 50 cm, as the data from Germany meteorological service show. There is still water stress in some areas.
Since the hot year of 2018, we have had a persistent drought in Germany – only stopping at the wet year of 2021.
Plants need water longer and more often
At this time, it cannot rain “too much” in terms of soil water requirements. In addition, there is another problem caused by constantly high temperatures in the context of global warming: as the growing season lengthens and winter dormancy becomes shorter and sometimes almost complete, plants also grow longer in autumn and more early in spring. the ground for its growth.
In light of droughts and floods – here in Germany too – it becomes increasingly clear how important water management is. When it rains, that rain must drain, if possible it must not drain. So cities need more open green spaces – facades and roofs need to be greened so that water can be held in place.
These green environments provide less hostile conditions for people and animals in hot, dry summers. Sponge cities help us meet the challenges of extreme weather.
Due to climate change, extreme weather events such as heavy rains and flooding are becoming more important, and solutions are being sought to protect habitats. One of them: Sponge Cities. In Sponge City, areas capable of absorbing large amounts of water and releasing it again with a delay are created. There are individual pilot projects in German cities such as Hamburg or Berlin.
Copenhagen is a pioneer city abroad: the entire city center was redesigned according to the sponge city principle and the runoff model was calculated. This shows where and how much water flows when it rains. Based on this, streets, squares and many buildings were reassessed.
The angle of inclination of some roads is changed so that the water can drain in a directed way (rainwater roads). Other methods have been reduced to serving as retention methods. There are “green roads” – green streets where water can seep into plant beds, tree ditches and street cavities. Squares, and parks in particular, are being altered or redesigned to function as reservoirs and retain as much water as possible, which can infiltrate and evaporate. New construction projects in the city are based on this principle. The goal: better protection against extreme weather events.