Berlin is a city built on water, from the Spree and Havel Rivers to the lakes and canals that snake through its urban landscape. However, the city is uniquely vulnerable. Unlike other major European metropolises that draw from multiple sources, Berlin relies entirely on groundwater: no lakes, no reservoirs, just what flows beneath the surface.
With around 3.8 million people depending on this underground supply, and with climate change intensifying, Berlin’s water system is feeling the pressure.
Bank Filtration: Nature’s Water Filter
Berlin’s drinking water system heavily relies on a natural process called bank filtration. Water from the Havel and Spree Rivers, as well as nearby lakes, is pulled through layers of sand and gravel before being treated and distributed. This natural system has worked well for decades, keeping Berlin’s water clean and safe. After use, the water is treated and returned to the rivers, starting the cycle anew.
But the past few years have shown the cracks in the system. “Currently, we have the water quality that we need. But the last five years were really dry years and this kind of showed us already limits of the system,” explained Josefine Filter of Berliner Wasserbetriebe.
New Climate, New Challenges
With annual rainfall averaging around 580 litres per square metre, Berlin was never a particularly wet city. But now, climate change is disrupting rainfall patterns. The region is experiencing more frequent and intense downpours, along with longer dry periods.
Weather isn’t the only concern. In 2038, Germany is scheduled to close the Lusatia coal mine, which currently discharges groundwater into the Spree River. Without this artificial supply, and with increasingly dry summers, Berlin’s drinking water faces growing risks.
In response, the Berlin Senate introduced a Masterplan Water, a set of 32 strategic measures aimed at protecting the city’s long-term water supply.
Supporting Informed Decisions
To help cities like Berlin prepare for the uncertain future, researchers in the European project IMPETUS are developing advanced modelling tools. These simulations assess how droughts, changes in river systems, or the end of coal mine discharges might impact water availability, and how different management strategies could respond under stress.
Exploring New Solutions
One promising innovation being explored is ozonation, an advanced treatment process that uses reactive oxygen to break down pollutants such as pharmaceutical residues. Already recommended by the European Commission, ozonation is being implemented in Berlin and could make it easier to reuse treated wastewater. This could add flexibility to the city’s water supply system in times of drought.
Planning for the Long Term
Berlin is not alone. Cities across Europe are grappling with the effects of climate change on their water systems. As Regina Gnirss of Berliner Wasserbetriebe puts it: “We cannot go on business as usual. And that’s the reason we try to have a picture ready, which is not looking on the yearly water demand we have, but on the water demand we have in ten years, in 20 years… How will you react?”
By preparing today for the challenges of tomorrow, Berlin is working to keep its water supply secure for generations to come.
