According to the Berlin hydrogeologist Irina Engelhardt, the enrichment of artificial groundwater during heavy rain could provide a remedy during drought periods in the future.
“In some regions we see a decent drop in the groundwater level,” said the head of the Chair of Hydrogeology at the Technical University of Berlin of the German Press Agency. It is indispensable for people, animals and nature – for example as drinking water from the tap, for irrigating fields or watering animals. According to Engelhardt, urgent measures are therefore already needed to ensure that sufficient water is still available even if the drought lasts for a long time.
Artificial groundwater against drought
The idea of artificial groundwater recharge is to collect rainwater that does not seep away during heavy rains in spring, autumn and winter. Especially in densely populated cities like Berlin, the water finds it difficult to get into the ground. This is not only harmful to nature, but also to the groundwater. Because if the rainwater flows into the sewage system, it is lost for groundwater recharge.
To avoid that, it could be temporarily stored in large tanks, Engelhardt explained. According to the scientist, this ideally happens in sinks, lakes or reservoirs. “The pool for temporary storage would have to be at least as big as a lake.” However, apart from classic dams, there are no storage reservoirs of this size in Germany. Later, the water can then be artificially seeped into the ground to increase the amount of groundwater if necessary.
Another option for artificial treatment is to take river water and let it seep away. In Berlin, for example, this is already being done. According to the Berliner Wasserbetriebe, depending on the season, ten percent of the drinking water is obtained from artificially enriched groundwater that was previously taken from the Havel.
Germany needs artificial groundwater recharge
However, Engelhardt is less worried about Berlin than about other regions of Germany: “In my view, the water problem in Berlin is still limited.” Since there was already a lack of groundwater in the capital 100 years ago, a large part of Berlin’s drinking water is obtained by so-called bank filtration – i.e. from wells that use seeped surface water from nearby rivers or lakes. According to the water company, the drinking water supply is stable.
Nevertheless, the scientist assumes that Germany will no longer be able to do without artificial groundwater recharge in the future. In countries like Spain or Israel, the practice has long been part of everyday life. “We should definitely start introducing new technical measures on an ongoing basis, which may also require adjustments to water law.” For example, when using cleaned wastewater, the use of which – for example for the irrigation of green areas – has not been legally possible in Germany so far.
Of course, the reuse of waste water and rainwater must be strictly monitored and sewage treatment plants technically upgraded to further purification stages, said Engelhardt. A variety of contaminants could be present. For this reason, Berliner Wasserbetriebe invested around 100 million euros in the cleaning quality of their own sewage treatment plants last year. Because: “Purified wastewater is an important resource for the landscape water balance in the future,” said a spokeswoman.
