Published: 12:12 AM, 16 July 2026
How to store more groundwater for dry seasons
Many soils in Germany are far too dry. Rainfall was already lacking in spring, especially in March.
Even the partly above-average precipitation in some regions during April and May was unable to replenish the missing moisture in deeper soil layers. This is shown by the current drought monitorof the Helmholtz Center for Environmental Research (UFZ).
The city of Munich in southern Germany has banned filling private swimming pools and watering lawns.
Following an extreme heat wave at the end of June, the next one is already torching Europe, putting even more strain on dwindling groundwater resources.
Anyone with a garden and a water tank knows the advantage of collecting rainwater and using it when rain is scarce. But groundwater also functions like a gigantic water reservoir.
Containing nearly half of the world's drinking water, groundwater forms when water seeps into the ground and accumulates above impermeable layers of rock or clay in the subsurface. It's often the only source of water in arid regions.
Groundwater levels are falling worldwide
Precious groundwater is currently being extracted at three times the rate it was 50 years ago.
The problem of more intensive water use is being exacerbated by more frequent drought linked to climate change. Even during heavy rains, the dried-out soil cannot absorb enough water.
More and more land is also being paved over, causing rainwater to run off the surface instead of seeping into the ground - meaning it can't be collected for use during dry periods.
Even in countries with relatively high rainfall, such as Germany, groundwater levels are falling significantly, with wells drilled deeper and deeper in some regions to reach water.
Groundwater reserves can only replenish if enough rain seeps into the soil. But groundwater overexploitation means that more water is extracted than can be restored.
Now more than 2 billion people and 40% of global agricultural production depend on overexploited groundwater reserves.
Targeted groundwater storage to combat drought and flooding
A research team led by hydrogeologist Thomas Baumann from the Technical University of Munich has developed a "Smart Storm Water Storage" device to tackle groundwater depletion.
"Our idea was to combine flood protection with drought prevention," said Lea Augustin, another hydrogeologist working with Baumann.
The facility is located in a hilly hop-growing region about 60 kilometers (about 40 miles) north of Munich, where heavy rainfall frequently causes flooding, and where groundwater is significantly depleted for drinking water and irrigation.
The water storage project works by first collecting water in a retention basin during heavy rain. It is then purified, and pollutants are removed. The clean water then flows through pipes to so-called infiltration wells that channel it about 30 meters (100 feet) deep into the ground. As the groundwater level rises, the water can be pumped back up via wells.
Groundwater does not evaporate
The Namibian capital, Windhoek, is also working to replenish groundwater. The city is located in the country's arid highlands where rainfall is scarce. By the late 1960s, the groundwater was already considered overexploited. At the time, Windhoek responded by becoming one of the world's first cities to convert wastewater into drinking water.
And since 2002, infiltration wells have been used to channel this treated water into the ground. Water sourced from sometimes distant reservoirs is also used to replenish groundwater.
The advantage is that far less water evaporates underground compared to open reservoirs, allowing better retention of scarce water resources.
California relies on groundwater storage
More and more groundwater remediation techniques, sometimes known as managed aquifer recharge, are being developed worldwide.
These include the redirection of excess rainwater or floodwater into ditches or large basins before it slowly seeps into the ground. The method is less expensive than technical systems but requires a lot of space. It also takes longer for the water to reach the aquifer.
Such infiltration basins exist in numerous worldwide locations, including along the San Gabriel River in the Los Angeles metropolitan area.
The drought-stricken US state of California views aquifer recharge as a key strategy for coping with climate-related weather extremes, according to the state water agency. In 2023 alone, more than 4.1 million acre-feet of water - equivalent to more than 5 billion cubic meters - was injected into aquifers, the agency told DW.
>> DW
