Tobias Krüger is a Professor of Hydrology and Society at the Institute of Geography at Humboldt-Universität zu Berlin. There, he heads the Integrative Research Institute for Human-Environment Systems (IRI THESys). In the Einstein Research Unit “Climate and Water under Change” (CliWaC), his team brings together research results in models and prepares these for various target groups. Einstein Research Units (ERUs) are understood as interdisciplinary and transdisciplinary collaborative efforts on strategically important research questions within the Berlin University Alliance. They are funded for at least three years with up to EUR 2 million per year.

What are you researching in CliWaC?

We are investigating the effects of climate change on the prevailing water situation in Berlin and Brandenburg. We are conducting three case studies to this end. In the first study, we are looking at the following bodies of water: “Groß Glienicker See” and the “Sacrower See”. Both are part of a coupled hydro-geological system of glacial lakes that were formed after the melting of the Weichselian-Baltic Sea ice sheet. In the second case study, we are examining the river Spree and its catchment area. For decades, the underlying water situation there was shaped by the large, open-cast lignite mining areas in Lusatia, from which groundwater was pumped out and discharged into the Spree. This will continue to change with the phasing-out of coal and, with it, the water balance of the Spree as far as Berlin and beyond. And in the third case study, we are investigating the effects of extreme rainfall in urban areas. We are also developing prospective solutions for dealing with such heavy rainfall events.

What have been your most important findings to date?

In Berlin and Brandenburg, both heavy rainfall events and droughts will increase – including in the form of so-called “flash droughts”. They appear in a flash when it has barely rained for a prolonged period of time and is very hot. In order to overcome such challenges, we looked at ideas stemming from the “sponge city” concepts within the framework of CliWac that have been under discussion for some time, and which have already been implemented in some cases. Just as a sponge absorbs water, Berlin and Brandenburg could better store heavy rainfall for periods of drought. This can be achieved, for example, by greening roofs and building facades, or by granting rivers more space. They then flow more slowly and can spread out when flooding occurs. Some of the water seeps away, and new groundwater is created. The construction of rainwater retention basins can also contribute to this end. However, potential flood risks from near-surface groundwater must also be taken into account. This requires close-knit cooperation between those stakeholders involved in the planning process, such as water suppliers, water consumers (such as industry), and the authorities. Berlin and Brandenburg must also work more closely together. This is because Berlin depends on the water resources that are formed in Brandenburg, or even Saxony.

What difficulties do you envisage there?                                                                             

Our ethnographic and political science research has shown that collaboration in water management is affected by fundamental social conflicts – such as the urban/rural divide. When citizens of Brandenburg look at Berlin, some ask themselves: those Berlin dwellers are better off than us anyway, why should we give them our water too?

Can such questions be answered scientifically?

The natural and social sciences can provide helpful information here. But it takes more than facts to develop measures and gain acceptance in society. It requires empathy. We scientists have to listen to what people in society are worried about, and subsequently address their concerns in our questions and proposed solutions. And we need to explain scientific findings better. This includes providing coordinated answers across the boundaries between disciplines. This is what we do at CliWac as part of the project AnthropoScenes. Researchers present their findings in the Humboldt Lab, for example, on stages in Berlin or elsewhere in Brandenburg and discuss these with citizens. I myself went on river walks along the Panke and Spree with Pauline Münch from “AnthropoScenes” and citizens, as well as with the journalist, literary critic and honorary professor of modern German literature at Humboldt University, Lothar Müller.,and another time with the ensemble of the “RambaZamba Theater” in preparation for their play “the world flames like a discokugel” by Jacob Höhne.

How did the Berlin University Alliance support CliWaC?

AnthropoScenes has been funded by the BUA since June 2021. That was a stroke of luck for CliWaC. Thanks to the integration of AnthropoScenes, scientific communication has enjoyed a high priority within CliWaC from the very start. And this has also furthered the establishment of an unusually strong role for the social sciences in large-scale research projects.

Can you explain this in more detail?

During large, interdisciplinary research projects, the social sciences are often left with the task of finding out whether scientific solutions are accepted by the population. In CliWaC, on the other hand, colleagues from the social sciences conduct ethnographic, sociological, or political science studies to identify the fears and concerns of the population from the very outset, which are then incorporated into scientific research and solutions.

Could you provide an example?

Ethnographic field research in Berlin and Brandenburg has shown that the population is very interested in the consequences of climate change and approaches to overcoming them. Simultaneously, many respondents did not feel well informed by the scientific community. That is why we launched the CliWaC Explorer. This is a website where we will pool our social and natural science research findings and present them in a comprehensible way. In doing so, we are creating a reliable information alternative to the pseudo-scientific information often found on offer on social media, which I would characterize as “fake science”. This is the only way that solutions can be discussed in society in an informed manner.

Projects such as the CliWaC Explorer require close collaboration between different scientific disciplines, as well as between scientists and partners from civic society. How did you manage that?

We have created customized exchange formats depending on the topic and information needs of project participants. For example, there were workshops to which all CliWaC participants were invited, and where they were able to feed questions into the research process. But we also held workshops for specific groups. Research colleagues discussed risk perceptions pertaining to climate change and water with local residents, nature conservation organizations, farmers, water companies and administrations, and evaluated proposed solutions that were already on the table, and which could be implemented quickly. Such formats create a shared awareness of the underlying issue, which opens up opportunities for better, more comprehensive solutions.

And what’s next for CliWaC?

With CliWaC, we have created a research network on the topic of water. This has enabled us to network scientists and experts who now want to initiate further research projects together. This includes our involvement in the planned Einstein Center for Climate Change. The CliWac Explorer will serve as an important connection to keep this network together. And that is why we are already looking for suitable funding to continue (and further develop) the Explorer.