A map of groundwater depletion in 40 global hotspots runs far deeper than earlier estimates, and farm irrigation drives the steepest water losses.<\/p>\n
Farms pull water out of the ground to carry crops through a dry stretch. Cities do the same when their reservoirs run low. <\/p>\n
Since 2002, satellites have been weighing water losses from above, though rarely at a scale smaller than a mid-sized state.<\/p>\n
Researchers at NASA uncovered previously hidden changes in water storage across 40 regions shaped by human activity, including losses far greater than earlier estimates.<\/p>\n
The sharper the picture got, the worse the drain looked, and it looked worst where people pump the hardest.<\/p>\n
The new method reveals long-term trends in water storage, but it cannot track how those changes unfold from year to year.<\/p>\n
Mary Michael O\u2019Neill, Matthew Rodell and Bryant D. Loomis conducted the research at NASA\u2019s Goddard Space Flight Center<\/a> in Maryland. <\/p>\n O\u2019Neill also works at the University of Maryland\u2019s Earth System Science Interdisciplinary Center<\/a>.<\/p>\n Weighing the world\u2019s water losses from orbit<\/p>\n NASA launched the first pair of these satellites in 2002 and a replacement pair, GRACE-FO<\/a>, in 2018. They fly one behind the other and measure the distance between them without stopping.<\/p>\n Ground with more mass beneath it tugs a little harder on the lead satellite than on the one behind. The gap between the two shifts by a tiny amount.<\/p>\n From those shifts, researchers work out where mass on Earth has moved. <\/p>\n Water is most of what moves. Add up what\u2019s held in soil, snow, lakes, rivers and the rock underneath, and you get one figure for the fresh water a patch of land is holding.<\/p>\n The trouble has always been the size of the patch. The standard method blends everything inside roughly 58,000 square miles (150,200 square kilometers) into one value, an area about the size of Illinois. <\/p>\n A single, overpumped farm valley disappears into that average.<\/p>\n So the team went back to the raw distance measurements and fit one trend to the whole record, instead of stacking up monthly snapshots. <\/p>\n Their map picks out changes that are five to ten times finer.<\/p>\n Water losses were larger than estimated<\/p>\n Ninety-four places came through with water trends too strong to be noise. <\/p>\n In 40 of them, the pattern lined up with something people were doing: pumping for irrigation, clearing forest, farming on rainfall alone, or filling a reservoir.<\/p>\n Add up what those 40 lost between 2002 and 2025 and it comes to roughly 750 cubic miles of water (3,122 cubic kilometers), more than Lake Victoria holds. <\/p>\n Gains across the same regions come to about four-fifths as much.<\/p>\n Asked by Earth.com which of the 40 hotspots are most worrying, O\u2019Neill said, \u201cThe regions of greatest concern are those already recognized as water-stressed, where we now observe losses even greater than previously estimated.\u201d <\/p>\n She added that these included areas of the North-Western Sahara Aquifer System (over Algeria and Tunisia), the Saq aquifer system in Saudi Arabia, southern Iran, and especially the Indo-Gangetic Plain in northern India.<\/p>\n Old method shows lower water losses <\/p>\n Run the old method over the same places and its trends come out 33 percent smaller on average. <\/p>\n For the seven smallest regions, it missed 52 percent. The gap against a 2018 map<\/a> is wider still.<\/p>\n The smaller the region, the more likely earlier measurements were to underestimate its water losses.<\/p>\n Pumping takes the worst of it. Earlier studies<\/a> of groundwater depletion had estimated the declines to be, on average, 45 percent lower.<\/p>\n Irrigation drives the steepest declines<\/p>\n Northern India is the deepest hole on the groundwater map, losing close to 7.8 cubic miles (32.5 cubic kilometers) of water a year. Two other recent studies estimated roughly half that. <\/p>\n Melting Himalayan glaciers account for only about 15 percent of the losses, suggesting that groundwater pumping plays a much larger role.<\/p>\n In central Saudi Arabia, the water leaving the ground each year runs to more than six times what rainfall and rivers put back. Most of it comes out of one desert aquifer, the Saq.<\/p>\n T\u00fcrkiye\u2019s losses came out at more than double an earlier figure, and the shortfalls that followed reached downstream into Syria and Iraq.<\/p>\n Across North Africa and the Middle East, ancient aquifers are under pressure from desert farming and a warming climate<\/a>.<\/p>\n Iran shows the resolution problem plainly. Two regions covering about a quarter of the country are suffering water losses that are equal to what one earlier study attributed to the whole of Iran.<\/p>\n Two of the 40 are in the United States. One is centered on California\u2019s Central Valley, where drought since 2003 and heavier pumping drove the decline. California\u2019s farms<\/a> sit on top of it. <\/p>\n The other is the southern High Plains Aquifer, where more than 80 percent of irrigated land runs on groundwater.<\/p>\n Dams added water<\/p>\n Not all of the 40 are emptying. The biggest additions are reservoirs; about 450 large ones went in during the satellite era.<\/p>\n Russia\u2019s Boguchany Reservoir, on the Angara River, was the largest built anywhere this century until the Grand Ethiopian Renaissance Dam opened in 2025. <\/p>\n Although it has received relatively little attention in scientific research, the reservoir produces the strongest individual water-storage signal in northern Asia outside the polar regions.<\/p>\n Malaysia\u2019s Bakun Reservoir covers roughly 270 square miles (700 square kilometers), one of the smallest things these satellites have picked out alone.<\/p>\n Rain-fed crops raise water tables<\/p>\n Stranger still is farming without irrigation. Across sub-Saharan Africa, land cleared of native savanna and planted with millet and other rainfed crops is gaining water. <\/p>\n \u201cWhat surprised us most was how widely rain-fed agriculture and land clearing were associated with increases in water storage across sub-Saharan Africa and South America,\u201d O\u2019Neill told Earth.com.<\/p>\n Crops such as legumes and cereals \u2013 which have shallower roots and transpire less \u2013 can enhance soil recharge and raise water tables, explained O\u2019Neill.<\/p>\n \u201cBut we did not expect that relationship to emerge significantly at continental scale.\u201d <\/p>\n Sharper maps come at a cost<\/p>\n The team fit one trend across all 23 years, which is what sharpened the map of water losses. What it erases is timing. Wet cycles and drought recoveries drop out.<\/p>\n It can also only connect a cause to an effect in the same place. Upstream dams, river diversions and aquifers linked across borders had to be handled separately.<\/p>\n Take the Aral Sea<\/a>, down 74 percent from the area it covered in the mid-20th century. Its water was taken somewhere upstream.<\/p>\n Human land and water use explained a measurable share of the trends on every nonpolar continent except Australia, which didn\u2019t fit.<\/p>\n Checking the map against the ground worldwide is still out of reach, because monitored wells are too sparse for a formal comparison. <\/p>\n Where well records do exist, they follow the new trends more closely than the old ones.<\/p>\n GRACE Continuity, the next spacecraft in line, is expected to launch in 2028. <\/p>\n Every year added to the record cuts the map finer, which matters most for the growing cities<\/a> and farm districts the old map couldn\u2019t see.<\/p>\n The full study was published in the journal Proceedings of the National Academy of Sciences<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"A map of groundwater depletion in 40 global hotspots runs far deeper than earlier estimates, and farm irrigation…\n","protected":false},"author":2,"featured_media":926256,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22],"tags":[64,63,75,128],"class_list":["post-926255","post","type-post","status-publish","format-standard","has-post-thumbnail","category-environment","tag-au","tag-australia","tag-environment","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/926255","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=926255"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/926255\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/926256"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=926255"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=926255"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=926255"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}