The Berlin government is implementing various construction measures to transform the German capital into a sponge city that effectively manages rainwater.
Within two years, a massive pit in central Berlin will become the largest water reservoir in the German capital, capturing the increasingly valuable resource of water, according to AFP.
Water reservoir under construction in central Berlin. (Photo: AFP).
Once a swamp centuries ago, Berlin has transformed from a city trying to prevent abundant groundwater from overflowing to efforts to preserve lush green forests. “In the past, the goal was to drain rainwater so that people could walk through the city without wearing rubber boots,” said Stephan Natz, spokesperson for the Berlin water management authority. However, in 2018, the city adopted a new model and is now seeking to store rainwater to combat drought while preventing flooding.
Essentially, the city is applying the concept of a sponge city, which emerged in the 1970s and has gained traction in urban centers across the United States, China, and Europe, especially amid climate change that has made weather systems increasingly erratic and severe. “Rainwater distribution has become more chaotic today. Drought follows heavy rainfall, and warming increases evaporation,” Natz stated. “Berlin’s 150-year-old drainage system was not designed to handle the large floods we see today. In cases of heavy rain, stormwater mixes with sewage and floods the Spree River, causing fish die-offs and visible pollution.”
At the same time, Berlin has faced severe water shortages in recent years due to drought conditions that have left the ground too dry to absorb sudden heavy rains. As a result, the city’s groundwater levels have yet to return to normal after five years of drought, according to the Leibniz Institute of Freshwater Ecology and Inland Fisheries. “Now, people are increasingly aware of the value of water in Berlin. This is one of the driest places in Germany,” said Darla Nickel, director of the city’s rainwater management authority.
Symbolizing the ongoing transformation, the massive water reservoir under construction is located right in the heart of the capital, less than 2 km from the Brandenburg Gate. The reservoir, with a diameter of 40 meters and a depth of 20 meters, will collect nearly 17,000 square meters of water, five times the capacity of an Olympic swimming pool. It will store rainwater before directing it to a treatment facility.
In addition to the expansive reservoir, Berlin is requiring new housing projects to include rainwater collection systems. The Quartier 52 housing complex, built five years ago in the southwest of the city, provides a model for this. Three large ponds dug around the complex offer residents a walking path on sunny days while also storing water during rainy weather. Rainwater is collected from rooftops and funneled into the ponds. The water then evaporates, creating a more pleasant atmosphere, according to Nickel. Sidewalks are also constructed with a slight slope to allow water to flow into the ground. The challenge lies in replicating such measures throughout the city.
Overall, approximately 30 similar projects are underway as part of the sponge city initiative, including in the Gendarmenmarkt area in central Berlin. The city is also encouraging residents to install rainwater collection devices or to create green roofs, considering waiving management or treatment fees for rainwater. Authorities hope that Berlin will become a true sponge city within a few generations.
