The city of Munich in southern Germany\u00a0has banned filling private swimming pools and watering lawns.<\/p>\n
Following an extreme heat wave<\/a> at the end of June, the next one is\u00a0already torching\u00a0Europe, putting even more strain on dwindling\u00a0groundwater resources.<\/p>\n Anyone with a garden and a\u00a0water tank\u00a0knows the advantage of\u00a0collecting\u00a0rainwater and using\u00a0it when rain is scarce.\u00a0But\u00a0groundwater<\/a> also functions\u00a0like a gigantic\u00a0water reservoir.<\/p>\n Containing\u00a0nearly half\u00a0of the world’s drinking water, groundwater\u00a0forms\u00a0when water seeps into the ground and accumulates above impermeable layers of rock or clay in the subsurface.\u00a0It’s often the only source of\u00a0water in arid regions<\/a>.<\/p>\n Groundwater levels are falling worldwide\u00a0<\/p>\n Precious\u00a0groundwater\u00a0is currently being extracted at three times the rate it was\u00a050 years ago.<\/p>\n The problem of more\u00a0intensive\u00a0water\u00a0use<\/a>\u00a0is being\u00a0exacerbated\u00a0by\u00a0more frequent drought<\/a> linked to\u00a0climate change<\/a>. Even during\u00a0heavy rains<\/a>, the\u00a0dried-out\u00a0soil cannot absorb enough water.<\/p>\n More and more land is\u00a0also\u00a0being paved over, causing\u00a0rainwater\u00a0to\u00a0run off the surface instead of seeping into the ground\u00a0\u2014 meaning it\u00a0can’t\u00a0be\u00a0collected for use during dry periods.<\/p>\n Even in countries with\u00a0relatively high\u00a0rainfall, such as Germany<\/a>, groundwater levels are falling significantly, with\u00a0wells drilled\u00a0deeper and deeper\u00a0in some regions\u00a0to reach water.<\/p>\n Groundwater\u00a0reserves<\/a> can only replenish if enough\u00a0rain\u00a0seeps into the soil.\u00a0But\u00a0groundwater overexploitation\u00a0means\u00a0that\u00a0more water is extracted than can be restored.<\/p>\n Now more than 2 billion people and 40%\u00a0of global agricultural production depend on overexploited groundwater reserves<\/a>.\u00a0<\/p>\n Targeted\u00a0groundwater\u00a0storage\u00a0to\u00a0combat\u00a0drought\u00a0and flooding\u00a0<\/p>\n A research team led by hydrogeologist Thomas Baumann from the Technical University of Munich\u00a0has developed a\u00a0“Smart Storm Water Storage” device\u00a0to tackle groundwater depletion.<\/p>\n “Our idea was to combine flood protection with drought prevention,”\u00a0said\u00a0Lea Augustin, another hydrogeologist working with Baumann.<\/p>\n The facility is located\u00a0in a hilly hop-growing region about 60 kilometers (about 40 miles) north of Munich, where heavy\u00a0rainfall\u00a0frequently\u00a0causes flooding, and\u00a0where\u00a0groundwater is\u00a0significantly depleted\u00a0for drinking water and irrigation.<\/p>\n \u00a0<\/p>\n The water storage project works by first\u00a0collecting\u00a0water\u00a0in a retention basin\u00a0during heavy rain. It is then purified, and pollutants are removed.\u00a0The clean water\u00a0then\u00a0flows through pipes to so-called infiltration wells\u00a0that\u00a0channel\u00a0it\u00a0about 30 meters (100 feet) deep into\u00a0the ground.\u00a0As the groundwater level rises, the water can be pumped back up via wells.\u00a0<\/p>\n Groundwater does not evaporate\u00a0<\/p>\n The Namibian<\/a> capital, Windhoek,\u00a0is\u00a0also working to replenish\u00a0groundwater. The city\u00a0is located in the country’s arid highlands where rainfall is scarce. By the late 1960s, the groundwater was already considered overexploited.\u00a0<\/p>\n At the time,\u00a0Windhoek\u00a0responded by becoming\u00a0one of the\u00a0world’s\u00a0first cities\u00a0to convert wastewater into\u00a0drinking water.<\/p>\n And since\u00a02002, infiltration wells have been used\u00a0to\u00a0channel\u00a0this\u00a0treated water into the ground. Water\u00a0sourced\u00a0from\u00a0sometimes distant\u00a0reservoirs\u00a0is also used to replenish groundwater.<\/p>\n The advantage\u00a0is that far less water\u00a0evaporates\u00a0underground\u00a0compared\u00a0to\u00a0open reservoirs, allowing better retention of scarce\u00a0water\u00a0resources<\/a>.<\/p>\n California relies on groundwater storage<\/p>\n More and more\u00a0groundwater\u00a0remediation techniques, sometimes known as managed aquifer recharge,\u00a0are being developed worldwide.<\/p>\n These include the redirection of\u00a0excess rainwater or floodwater into ditches or large basins\u00a0before\u00a0it slowly seeps into the ground. The\u00a0method is less expensive than technical systems but requires a lot of space. It also takes longer for the water to reach the\u00a0aquifer.<\/p>\n Such infiltration basins exist in\u00a0numerous\u00a0worldwide\u00a0locations, including along the San Gabriel River in the Los Angeles metropolitan area.<\/p>\n The drought-stricken<\/a> US state of California views\u00a0aquifer\u00a0recharge<\/a> as a key strategy for coping with climate-related weather extremes, according\u00a0to\u00a0the state water agency.\u00a0In 2023 alone, more than 4.1 million acre-feet\u00a0of water\u00a0\u2014\u00a0equivalent to more than 5 billion cubic meters\u00a0\u2014\u00a0was\u00a0injected into aquifers, the agency told DW.<\/p>\n Flooding fields to increase groundwater<\/p>\n Another\u00a0option\u00a0is the targeted flooding of agricultural land when\u00a0extreme rain threatens, allowing floodwaters to be captured and directed into the groundwater. The advantage: The land can continue to be used for agriculture after the water has seeped away.\u00a0<\/p>\n Since farmland and pastures account for about 40%\u00a0of the world’s land area, this method has\u00a0great potential. However, it only works under certain conditions.<\/p>\n The plants must not be damaged. Furthermore, no pollutants or pathogens from the floodwaters must enter the groundwater, making\u00a0implementation difficult.\u00a0<\/p>\n River restoration replenishes groundwater levels\u00a0<\/p>\n Nature itself\u00a0can also help. When rivers are\u00a0restored,\u00a0they\u00a0expand. They can\u00a0then\u00a0spread out\u00a0during floods,\u00a0creating\u00a0shallow side channels and pools.<\/p>\n These capture floodwater,\u00a0some of\u00a0which\u00a0also\u00a0seeps into the ground. Floodplain microorganisms also\u00a0filter the water, meaning\u00a0the process\u00a0both\u00a0replenishes and purifies the groundwater.<\/p>\n At the same time, the risk of flood damage decreases.<\/p>\n Harvesting groundwater directly from rivers or lakes<\/p>\n In Germany, drinking water is often obtained indirectly from rivers\u00a0through a process known as bank filtration.<\/p>\n Here, groundwater is pumped out\u00a0of wells\u00a0located\u00a0near rivers or lakes, creating\u00a0a vacuum.\u00a0Water from the river\u00a0then\u00a0flows in to replace it. As it passes through the ground, it is naturally filtered.\u00a0Bank filtration provides more than half of Berlin’s drinking water.<\/p>\n Infiltration weirs also channel river water into the groundwater. These are structures in the riverbed that reduce the\u00a0flow\u00a0velocity,\u00a0or\u00a0temporarily dam up the river. When the water flows more slowly, more of it can seep into the ground.\u00a0<\/p>\nDrought had depleted water levels in Turkey’s Naip Dam Image: Mesut Karaduman\/Anadolu\/picture alliance<\/p>\n
Dams and groundwater recharge basins were constructed along the San Gabriel RiverImage: Stocktrek Images\/IMAGO<\/p>\n
India is among the countries using percolation tanks for water storageImage: Dad Fotos\/imageBROKER\/IMAGO<\/p>\n
Restoring rivers can help since they can spread out during floods, creating shallow side channels and poolsImage: Joachim Stingl\/imageBROKER\/IMAGO<\/p>\n