Nevertheless, they fear that depleting the underground water supply could increase the risk of conflict around the world. Researchers at the University of California, Irvine, which led the study, say that, while the data provide reliable estimates of use, they can't say for sure how much water is left in the aquifers. Great Plains, where crops are grown using mainly rainwater, fared better. Until recently, San Antonio was one of the largest cities in the world that. Eight of the worlds 37 largest aquifers were classified as 'overstressed,' with almost no natural replenishment, while five others were found to be 'extremely' or 'highly' stressed. Basins shown in shades of brown have had more water extracted in the study years than could be naturally replenished basins in blue saw increases in underground water storage, perhaps due to changes in precipitation. The Ogallala aquifer extends through 48 counties of the Texas Panhandle and. It is found throughout Florida and extends into the southern portions of Alabama. Other places, such as the sparsely populated and very wet Amazon Basin and the U.S. The map above shows the annual change in groundwater storage from 2003 to 2013 in the 37 largest aquifer systems in the world. The Floridan aquifer is one of the highest producing aquifers in the world. The aquifer under California's drought-stricken Central Valley is also being overused. Groundwater is being rapidly depleted in the Middle East, North Africa and Central Asia. GRACE measures water under the ground by measuring its gravitational tug, and it watched 37 aquifers around the world over the course of 10 years to see what was happening to the water they held. Groundwater is also used for farming, especially during times of drought.
![biggest aquifers in the world biggest aquifers in the world](http://videos.usatoday.net/Brightcove2/29906170001/2015/06/29906170001_4302434628001_video-still-for-video-4302366792001.jpg)
![biggest aquifers in the world biggest aquifers in the world](https://www.sciencenewsforstudents.org/wp-content/uploads/2019/11/ts_groundwater_map_free.jpg)
Globally, scientists estimate that roughly 2 billion people rely on water supplied from underground aquifers as their main source of freshwater. The Gravity Recovery and Climate Experiment, or GRACE, used a pair of satellites to measure water use in the world's aquifers.