(Berlin) A 20-meter-deep hole destroys the heart of Berlin. Within two years, this titanic project would create the largest reservoir in the German capital, capable of collecting water that has become precious.
“Before, the goal was to drain rainwater, so you could cross the city without rubber boots,” said Stefan Knotts, a spokesman for Berlin’s water authority, screwing a hard hat on his head at the river’s edge.
But the city has changed course and is now working to store rainwater where it falls to control floods and fight drought.
It’s the concept of a “sponge city” that was theorized in the 1970s and adopted by Berlin in 2018. In the United States, China, and Europe, many urban centers have switched to this approach, which proposes to absorb, collect, filter, and reuse wastewater.
Photo by John McDougall, Agence France-Presse
Mr. Knotts explains.
Five Olympic swimming pools
A symbol of ongoing change: the giant water reservoir under construction in the heart of the capital, less than two kilometers from the iconic Brandenburg Gate.
A basin with a diameter of 40 meters collects nearly 17,000 m3 The water – five times the capacity of an Olympic swimming pool – is stored and then sent to a treatment plant.
Photo by John McDougall, Agence France-Presse
Because, with a 150-year-old sewer system and more extreme weather conditions than in the past, the city cannot manage both wastewater and stormwater. causing fish mortality and visual pollution,” explains Stephen Knotts.
At the same time, Berlin, despite being built on former swamps, has been facing severe water shortages for years. After five years of drought, water levels have yet to return to normal, according to data from the Leibniz Institute for Freshwater Ecology and Fisheries.
“There is a slow awareness of the value of water in Berlin. It is one of the driest places in Germany,” underlines Darla Nickel, director of the German capital’s rainwater management system, created to support the city’s transformation into a sponge.
Every new real estate project should now adopt this strategy by developing rainwater harvesting techniques.
The 52 Degrees North District, southwest of the city, which emerged about 5 years ago, is carefully applying the new rules. Young parents, children and old people with prams merrily mingle around the three large ponds in a windy row of reeds.
“That simple! »
Rainwater is “collected on green roofs and in these basins. The water evaporates, creating pleasant air,” says Darla Nickell. Green walkways are also sloped so that water seeps into the soil more easily.
“You see it’s so simple! » exclaims Mme Nickel.
But even if Berlin is half as dense as Paris, the challenge is to multiply these kinds of activities in the heart of the city.
Photo by John McDougall, Agence France-Presse
“We progressed much more slowly with the existing building than with the new construction,” admits Darla Nickell.
For example, in a historic district of Berlin, a square is being renovated to collect rainwater and channel it into the groundwater.
The Stormwater Management Institute supports more than thirty projects linked to “Sponge City”. The municipality encourages individuals to install water collectors or green roofs by exempting them from fees for rainwater management and treatment.
However, local officials know that it will take generations for Berlin to truly become a “sponge”. “It remains to be seen whether climate change will give us time,” observes Stephen Knotts.
