Berlin Lichtenberg district, Germany, December 1, 2025. Although the city of Berlin is already implementing large-scale measures to manage rainwater sustainably, thousands of liters of valuable water flow into the sewage system when it rains. It could be put to good use, for example to water school gardens in the hot summer months or to let it seep away wherever it falls. To leverage the huge potential of decentralized rainwater management at 24 Berlin schools in Lichtenberg, a district with some high-density areas, the local roads and parks department commissioned Drees & Sommer SE to draw up a report. The company specializes in consulting on construction, real estate and infrastructure. 80 percent of the project was financed by the European Regional Development Fund (ERDF), and 20 percent funded by the federal state of Berlin within the framework of the Berlin Program for Sustainable Development (BENE 2). The recently completed analyses indicate the extent to which each of the schools is already using rainwater efficiently and where there is an urgent need for action.
The idea of using rainwater usefully at educational facilities and sites is not new in Berlin. Five schools in the Friedrichshain-Kreuzberg district are already using rainwater butts to collect it from the school roof. Berling’s Lichtenberg district is now following suit. Jörg Schreckenberg, who heads the green spaces management at the Lichtenberg district office says: “Like many major cities, Berlin has a combined sewer system. In heavy rainfall it quickly overflows and causes flooding where the water is least needed.“ To avoid this, rainwater at a total of 24 schools is to be collected directly on the properties in future, seeped away on site, or reused. The first steps in the planned measures include disconnecting each of the schools from the sewer network operated by Berlin's water utility, Berliner Wasserbetriebe. This would correspond to a total disconnected area of 135,000 square meters of sealed soil.
Basic Evaluation Shows Need for Action – from Sealed Surfaces to Rainwater Infiltration
Based on various selection criteria, including soil permeability and depth to groundwater table, twenty four of ninety properties were selected for deeper analysis, in collaboration with Berlin’s rainwater agency, Berliner Regenwasseragentur[i]. These were considered most suitable for disconnection from the sewer system. Ramona Jones, project manager and expert for sustainable city development and urban water management at Drees & Sommer, started with a comprehensive survey and basic evaluation in order to analyze the condition of the selected properties and assess which measures have already been implemented for efficient rainwater management. The project manager comments: “We recorded aspects such as the infiltration capacity of the soil, the protection of historic buildings, the condition of the roofs and whether it is a water protection area. Information for the project has been gained by on-site visits and retrieved from publicly available sources. We can now say that some of the schools are very well positioned with large permeable surfaces, just a few sealed areas and some water butts that collect rainwater on schoolyards, for example. However, there is much room for improvement at other schools.”
There are a number of solutions to deal with this. Ramona Jones points out: “A good way of retaining rainwater, for example, is to create large-scale green spaces and infiltration areas.“ They absorb the rainwater like a sponge, store it and let it seep away. “This is why we speak about the ‘sponge city’ principle. Troughs are particularly suitable in the middle of these green spaces. This is because additional trees can be planted in them and they can be designed with biodiversity in mind,“ the expert points out. Alternatively, infiltration ditches can be used. She adds: “They are like cola crates, lined up and covered with geomembrane, and installed in the ground. When it rains, the water collects in the ditch and seeps away.” In addition, asphalted surfaces, like schoolyards or parking spaces, can be unsealed, at least to a certain extent.
Failing to Act Now Will Create Greater Costs in the Future
Drees & Sommer’s team of experts has made a rough assessment of the various methods of rainwater storage, infiltration and reuse, determined their location and evaluated them in terms of expected costs. “Especially in view of climate change, which is accompanied by more frequent heavy rainfall events and changing patterns of precipitation, we should stress that the cost of these measures is negligible compared to that which would be incurred if no action were taken,” emphasizes Ramona Jones.
Within the framework of the report, the project team has prepared a site plan for each of the twenty-four school properties and an assessment document with the results of the analysis. The expert says: “This information will be the basis for decision-making and the invitations to tender. We have recently submitted the documentation to the department responsible for green spaces management. They will decide which measures to pursue and which of the twenty-four schools will be given priority.” The results gained will serve as a reference for future school projects relating to decentralized rainwater management in Berlin.
Berlin’s Ideas for Sustainable Water Management
Germany’s capital is already at the forefront when it comes to conserving water resources. In September 2024, for example, the district of Friedrichshain-Kreuzberg built Germany's first rainwater bench. This is a piece of furniture that not only invites you to sit down, but also collects and stores rainwater from the roof of the Menschenskinder family center in its 500-liter tank. This provides enough water to irrigate its garden even during long periods of drought.
Jörg Schreckenberg comments: “Our expert opinion on twenty-four schools actively contributes to make Lichtenberg fit for the future. A nice side effect is that the schools also become interactive learning spaces that promote awareness of the city’s water situation among pupils and make the experience tangible.“ In addition to the positive effects of infiltration and sustainable rainwater management, it is possible that savings could be made in the rainwater fees charged by the water utility, Berliner Wasserbetriebe. According to the head of the department responsible for green spaces management, the structural improvements can be written off over a period of five to fifteen years.