The summer in Germany is extremely hot, and climate change is also increasing the trend towards longer and longer dry periods. One of the consequences: the sinking groundwater – with serious consequences for nature and agriculture. A glimmer of hope: the concept of “sponge cities”.
It’s hot in Germany. In addition to temperature records, the current summer has also seen record droughts. It is the driest summer to date since weather records began in 1981. The effects of the extreme weather are not only noticeable in this country, but can be seen throughout Europe.
Particularly dramatic: the situation in northern Italy, which is considered the worst in 70 years. The Dora, Baltea and Po rivers only carry around twelve percent of the usual amounts of water, and the Italian government has already declared a state of emergency for five regions. In France, too, the government is talking about the “worst drought” ever recorded in the country.
What still seems far away could soon be here in Germany due to climate change. “Central and Western Europe is one of the regions of the world that will be increasingly affected by soil water and groundwater drought with increasing global warming,” confirms Sonia Seneviratne, Professor at the Center for Climate System Modeling at the Institute for Atmosphere and Climate (IAC) at the University of Zurich (ETHZ).
Jörg Dietrich, head of the working group at the Institute for Hydrology and Water Management at the Gottfried Wilhelm Leibniz University in Hanover, points to existing satellite data showing that Germany will also be increasingly affected by the drought in the future.
Measures for dealing with water shortages in the future are currently being discussed with regard to the dangers that the drought and the associated sinking groundwater bring with them. One of them is the so-called “sponge city”.
The term refers to a concept of urban planning to collect and store rainwater locally in cities instead of just channeling and draining it. The idea behind it is very simple. As Germany’s cities are increasingly built up and “sealed” with asphalt and concrete, two problems arise:
If a city is able to absorb rainwater like a sponge, it can release the temporarily stored water through evaporation during hot periods. The city stays cooler this way. In conventional cities, a possible cooling by evaporating water is prevented, however, the immediate discharge of the falling precipitation into the sewage system.
At the same time, the concept of the sponge cities prevents flooding in the event of heavy rain, as it creates natural storage spaces for the large amounts of precipitation.
The sponge city is designed to collect and store rainwater where it falls. Above all, green areas, forests and meadows absorb the water best – and also release it into the environment in the event of heat.
Cities such as Hamburg, Berlin, Wuppertal, Freiburg or Leipzig have been dealing with the concept of sponge cities for some time in order to adapt their urban development to the conditions of climate change. In general, it is easier to implement the ideas of innovative urban development in new development areas than to redesign existing inner cities.
With regard to the groundwater problem, however, they are only suitable to a limited extent, since they can primarily be used in urbanized areas and not in rural areas. For all others, alternative measures must be taken with regard to the current developments in the German groundwater level.
But it is not only the groundwater itself that is sinking. At the same time, due to drought and heat, the demand for water increases in the summer months. Experts cite the following areas as examples:
The fact is that the sinking groundwater will continue to cause great concern for people and nature in the future. But we can all do something to conserve our water resources.
According to experts, there are several ways to do this. These include:
With all innovative ideas for saving water, however, it must be taken into account that in future it will also be possible that in extreme situations you will no longer be able to adapt well. “The latest IPCC report states that there are limits to climate adaptation,” said Seneviratne.
It is therefore important to work on your own awareness of how to deal with water. “Water is a scarce resource that needs to be handled with care. We have lost this insight – due to our supposed abundance of water,” emphasizes Claudia Pahl-Wostl, Professor for Resource Management at the Institute for Geography and Environmental Systems Research at the University of Osnabrück.
The population must be informed that rationing is conceivable in very difficult situations. This means that you have to make sure that you use as little water as possible in everyday life, for example in the garden and when washing.
Each individual can also actively save water in everyday life. FOCUS online has collected tips on how consumers can use simple means to reduce their water requirements.
Dietrich appealed that in the future it would also be conceivable to systemize the distribution of water in Germany in order to be able to protect particularly dry areas during periods of drought.
The research project WatDemand is currently being carried out for the systematic distribution of the water. This models the sectoral water requirements throughout Germany up to 2100 at the level of districts and river catchment areas and blends these with forecasts for the water supply in order to be able to identify future bottleneck regions in Germany at an early stage.
Last but not least, Germany can learn from other countries that have been exposed to regular periods of extreme heat for a long time. “In Cyprus, for example, an entire river is allowed to seep away in winter – and thus groundwater formation – so that the enriched groundwater can be used in the dry summer,” explains Thomas Riedel, research associate and business unit manager of water production at the IWW Water Center.
Further measures for dealing with water shortages in the future are also summarized in a report by the Federal Environment Agency from 2019.
