Groundwater depletion accelerating in Central Valley
December 27, 2022
Study finds an underground Gold Rush in California.
Dr. Jay Famiglietti, Executive Director Emeritus of the University of Saskatchewan’s Global Institute for Water Security and former Senior Water Scientist at NASA Jet Propulsion Laboratory, and other scientists report that groundwater in California and across the southwestern U.S. is disappearing “much faster than most people realize.”
Published in the journal Nature Communications, the study finds that the rate of groundwater depletion has been 31% greater during the (current) megadrought since 2019 than the last two droughts (2006-2011 and 2011-2017).
“The water stress level in California is getting higher,” said Pang-Wei Liu, a NASA scientist and the study’s lead author. The current pace of groundwater losses is now nearly five times faster than the long-term average since the 1960s.
“We are seeing what appears to be a rush to pump as much groundwater as possible before new restrictions take hold,” Famiglietti said.
No water may be left to manage under SGMA’s year 2040 deadline to achieve groundwater sustainability goals.
Accelerated depletion in California’s Central Valley during the drought is attributed to heavy agricultural pumping. Recent low water level measurements reveal threatened underground water reserves, which have endured low groundwater levels for decades.
Since 2003, the agricultural region has sustained total groundwater losses of approx. 36 million acre-feet, about 1.3 times the full water storige capacity of Lake Mead, the country’s largest reservoir.
Data analysis included of nearly two decades of data from two NASA satellite missions, including GRACE Follow-On which measured earth’s surface mass and water changes; soil moisture; surface water and snowpack to estimate groundwater losses; and estimates from a USGS computer model.
The step-like drops in average water levels were “only temporarily slowed” by brief wet periods. The losses of groundwater far exceed reductions in surface water, snow and soil moisture.
Groundwater is “disappearing at rates nearly 5 times faster than historical rates, said Famiglietti. California’s groundwater savings bank account is desperately need to get through droughts, but it may be depleted soon.
Satellite data reveals that California isn’t alone as areas throughout the Southwest face the combination of groundwater loss and drought – threating agriculture for people everywhere and drinking water supplies for communities who depend on wells.