It has never been this hot: The drought summer is showing its worst side. In addition, some regions are already struggling with water shortages. How is this going to continue in the future? The geoscientist Andreas Wunsch explains in an interview with FOCUS online what is to come.
According to the Karlsruhe Institute of Technology (KIT), 70 percent of our drinking water comes from groundwater and spring water. The drought summers of recent years and the particularly extreme summer of 2022 show that a commodity that is so taken for granted as water may soon no longer be available to everyone: drinking water has already had to be rationed in parts of Italy. At KIT, researchers have investigated how different scenarios of climate change can affect our drinking water supply. One of them is Andreas Wunsch. In an interview, the geoscientist explains how our groundwater is doing and how artificial intelligence can help with forecasts.
FOCUS online: Mr. Wunsch, simply asked: How is our groundwater?
Andreas Wunsch: Unfortunately not as it should be. The dry summers of recent years have left their mark, while winter precipitation has not been able to compensate for the losses. We are therefore currently seeing below-average and therefore too low groundwater levels in large parts of Germany.
The geoscientist Andreas Wunsch is a doctoral student at the Karlsruhe Institute of Technology (KIT). Photo: Andreas Wunsch
Many people have felt global warming first hand, especially this year with several consecutive heat waves. How does climate change affect our groundwater supplies?
Wunsch: First of all, we have to distinguish between direct and indirect influences. The direct influences are the immediate changes caused by a changing climate, for example higher temperatures. As a result, more water evaporates or is released by plants, which in turn means that less groundwater forms. We only have limited influence on such factors, since these are global problems and we can only counteract them as a community of states with more climate protection.
And what about indirect influences?
Desire: Indirect influences are, for example, changing or adapted vegetation or land use, but also increased groundwater extraction due to higher water requirements for drinking water, industry or agriculture. In contrast to direct influences from climate change, indirect factors presumably have a much stronger influence on groundwater. The good news, however, is that we can usually influence these factors locally and regionally.
How can we influence these factors locally?
Wish: We can determine, for example, how much water we take or how we treat plants. This affects, for example, which plants are grown on fields and how they are irrigated or how much water we take for our drinking water supply.
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If the forecasts are to be believed, dry regions such as the Mediterranean will become even drier. Humid regions such as northern Europe are becoming even wetter. How does that fit in with the heat waves and hot summers we’ve had in recent years?
Wunsch: That’s right, that’s what the overall trend looks like. However, there will of course continue to be individual years or a series of years that are particularly wet or dry. The last few years have been extreme events, but their frequency will increase in the future. This gives us a good idea of what we will have to deal with in the future.
How accurate are your forecasts for the regions in Germany? Where is it particularly scarce?
Wunsch: We have looked at different climate scenarios and actually see declining tendencies in all scenarios, to varying degrees. In the worst possible scenario, i.e. global warming of four and a half to five degrees, it was evident that eastern Germany would be affected by greater decreases than the rest. The most optimistic scenario corresponds to a warming of one and a half to two degrees and thus also the goals of the Paris climate agreement. In this scenario, this strong downward trend was not discernible in eastern Germany, but was weaker for all of northern Germany. However, we only simulated the climatic part, i.e. the direct effects of the climate mentioned above, such as changing precipitation or rising temperatures.
Do people in eastern or northern Germany have to worry about water?
Desire: The actual development depends to a large extent on indirect consequences such as groundwater extraction. Such factors then also have a considerable influence on whether people really have to worry about water. However, it is difficult to predict exactly how these will develop. Accordingly, we have not yet been able to take this into account in our models. In any case, the development is alarming.
In Brandenburg and Saxony, massive forest fires have been fought in recent weeks. What will people in these regions face if they are also confronted with falling groundwater levels?
Desire: Falling groundwater levels mean that the vegetation comes under even greater drought stress: If there is then too little precipitation, its resilience also decreases. Likewise, rivers are often largely dependent on inflowing groundwater. When the groundwater level falls, we must therefore also reckon with falling levels up to the point of smaller rivers falling dry. In extreme cases, the ratio can even be reversed, so that the water is discharged from the river into the groundwater and not vice versa. The corresponding effects on the ecology of the rivers, such as which plants and animals can then still live there, are of course on top of that.
So if rivers dry up and we have less groundwater, will that also affect our water supply?
Desire: The extent to which the water supply is restricted by falling groundwater levels varies locally and regionally. However, we will have to reckon with some bottlenecks, such as have already occurred in the Black Forest in recent years. Here, a clever distribution of the existing water resources via long-distance pipelines should be implemented even better.
For your research project, you used AI models to create a forecast for our groundwater. Why artificial intelligence? How can this be used to predict the level of our groundwater?
Desire: AI models are particularly suitable for considering a large number of locations. In contrast to conventional models, we hardly need any previous knowledge about the nature of the subsoil and can therefore calculate groundwater levels from climate data with comparatively little effort. The AI models automatically learn the connection between groundwater and precipitation or temperature. For this, physical processes do not have to be explicitly modeled.
How do your models work and what data are they fed with?
Request: Our models automatically learn the relationship between groundwater and climatic parameters such as precipitation and temperature using data from the past. In order to study the development of groundwater levels in the future, we use predictions of these climatic quantities, as simulated by climate models in various possible scenarios, as input data for our own models.
Can comprehensive measures such as the national water strategy be based on such AI models in the future in order to ensure optimal groundwater supply?
Desire: The forecasts of our AI models certainly provide important information here, but they are only one component. In principle, however, packages of measures such as the water strategy should of course be based on the available scientific knowledge, which then also includes the forecasts of the AI models.
What do citizens have to prepare for with regard to groundwater availability?
Desire: Since groundwater covers a large part of our water requirements, restrictions in the future are quite conceivable. We have to get used to the fact that unlimited water is no longer available everywhere and at all times. We also have to sensitize the population to handle water carefully. However, in order to at least secure the drinking water supply in endangered regions, a well thought-out distribution of the available water through long-distance networks can help.
What measures do we have to take to continue to guarantee our water supply?
Wish: Of course we have to reduce consumption overall and distribute the available water cleverly. At the same time, it is important that we simply record better how much is withdrawn in order to be able to better plan future measures. Withdrawal quantities are well documented in the case of the drinking water supply, whereas for industry and agriculture there are often only approved quantities. However, one often does not know how much and when is actually used. Of course, this makes it difficult for researchers to make reliable forecasts.
Can we, stupidly asked, “save” groundwater again?
Wunsch: Yes, we can also “save” groundwater, as you say. On the one hand, if we manage the available resources in a generally sustainable manner. Concrete measures such as buffering heavy precipitation with temporary buffer storage are also possible. On a small scale, for example, a cistern in a private household. On a large scale, sponge city concepts could then come into play.
What are sponge cities?
Desire: This is an idea from urban planning in which cities collect and store rainwater or release it again with a delay instead of draining it off directly. The water can be used for cooling in summer as well as for irrigation. A direct groundwater enrichment through targeted seepage of large amounts of water underground is also conceivable. Such measures are used in arid regions of the world, such as in Jordan, but also as part of groundwater management in Germany, such as in the Hessian Ried.
