Berlin: Two years from now, a giant hole in the basement of Berlin will become the largest reservoir in the German capital, taking with it an even more valuable resource – water.
A few centuries ago, Berlin, a swamp, went from one city to another to keep its forests green to prevent the groundwater from rising.
20 meters (66 feet) “The original purpose was to evacuate rainwater so that you can walk through the city without wearing rubber shoes,” Stefan Natz, a spokesman for Berlin’s water authority, told AFP.
But in 2018, the city adopted a “paradigm shift” and is now looking for ways to capture rainwater to combat drought and prevent flooding.
In fact, it uses the concept of the sponge city, which appeared as a theory in the 1970s and was favored by growing urban centers in the United States, China and Europe, because climate change makes weather systems more magnificent and more intense.
“Precipitation distribution is now more skewed, meaning that droughts are followed by heavy rains and hotter days, which in turn increase evaporation,” Natz said.
Berlin’s 150-year-old sewage system was not built to withstand today’s severe flooding.
At the same time, Berlin has experienced severe water shortages in recent years, as the capital’s drought conditions are unable to absorb sudden and heavy rainfall.
According to the Leibniz Institute for Freshwater Ecology and Inland Fisheries, groundwater levels in the capital have not returned to normal after five years of drought.
“Berlin is now realizing the value of water. This is one of the driest places in Germany,” said Darla Nickel, director of the capital’s rainwater management agency.
As a symbol of the ongoing transformation, a giant water reserve is located in the center of the capital – two kilometers from the Brandenburg Gate.
With a diameter of 40 meters, the reservoir holds approximately 17,000 cubic meters of water – or 5 times the size of an Olympic swimming pool.
It will store rainwater before sending it to the treatment plant.
In addition to mega reservoirs, Berlin needs a rainwater harvesting strategy in new housing projects.
Quarter 52, built five years ago in the southwest of the city, offers a model.
Three large ponds are dug around the estate, offering residents a nice way on sunny days for fishing when it rains.
Rainwater “is collected on the green roof and then in this pond,” Nickel said.
“Water evaporates and in turn creates a more comfortable atmosphere.”
Pavements also have a smooth slope, so water flows out of the ground.
“You see it can be very simple,” Nickel said.
The challenge is to expand such activities throughout the city.
“We have moved more slowly with existing buildings than with new construction,” Nickel said.
In total, about 30 projects in the sponge city plan are underway, including in the Gendarmenmarkt area in central Berlin, usually a tourist magnet.
The city is also asking residents to install water collectors or install green roofs, requesting waivers on storm water management or maintenance fees.
Officials know it will take generations for Berlin to become a true sponge.
“We’ll see if climate change gives us enough time,” Natz said.
