Stanford researchers say that California’s drought-stricken Central Valley harbors three times the supply of groundwater previously thought. The study, published in the journal Proceedings of the National Academy of Sciences, points up the need to develop a better understanding of deep aquifers, and has implications for regions beyond California where drought is a problem.
“It’s not often that you find a ‘water windfall,’ but we just did,” study co-author Robert Jackson told Stanford News Service. “There’s far more fresh water and usable water than we expected.”
What this actually means is murky, because the water is up to 3,000 feet below the Valley’s surface, making it costly to access. Researchers say it also may be salty or contaminated from oil and gas drilling. And pumping the deep water could exacerbate subsidence problems already plaguing the Valley.
“Previous estimates of groundwater in California are based on data that are decades old and only extend to a maximum depth of 1,000 feet, and often less,” Stanford News Service says. “Until now, little was known about the amount and quality of water in deeper aquifers.”
The new study, though, used data from from “938 oil and gas pools and more than 35,000 oil and gas wells to characterize both shallow and deep groundwater sources in eight California counties.”
Mary Kang, a co-author of the study, said more research is needed to determine how clean, or dirty, the deeper water is. “What we are saying is that no one is monitoring deep aquifers. No one’s following them through time to see how and if the water quality is changing,” Kang said. “We might need to use this water in a decade, so it’s definitely worth protecting.”
California is in its fifth year of drought. Water reserves in all of California’s reservoirs are well below their normal ranges, and in 2014 Gov. Jerry Brown declared a statewide drought emergency. Yet the Metropolitan Water District of Southern California, a wholesaler for 19 million people in 26 cities, recently announced “it has sufficient water supplies to meet the demand of its member agencies over the next three years.”