Los Angeles Times

Aquifers are being depleted

8 of the world’s largest basins have almost no replenishm­ent, studies find

- By Rosanna Xia rosanna.xia@latimes.com

More than a third of the largest groundwate­r basins in the world are being depleted faster than they are getting replenishe­d, and there are little to no accurate data showing just how much water is left in them, according to two new studies published Tuesday.

Researcher­s used data from NASA satellites to examine the 37 largest aquifers in the world. They found that eight were being depleted with almost no natural replenishm­ent and five, including the Central Valley, were “extremely” or “highly stressed,” with not enough water f lowing back to offset how much is sucked up. Saudi Arabia, India, Pakistan and northern Africa have the most stressed aquifers, according to the research.

The studies spotlight increasing sustainabi­lity concerns as regions like California rely more and more on groundwate­r during times of severe drought.

“We know we’re taking more than we’re putting back in — how long do we have before we can’t do that anymore?” said Alexandra Richey, who conducted the studies as a graduate student at UC Irvine. “We don’t know, but we keep pumping. Which to me is terrifying.”

Many previous studies of groundwate­r storage relied on statistica­l calculatio­ns and looked mostly at how much water was being pumped from the ground. These limited estimates were too uncertain to improve groundwate­r management, researcher­s said. For example, past storage estimates for the Northwest Sahara Aquifer System ranged from 10 to 21,000 years.

“This work clearly demonstrat­es that it is no longer adequate to continue citing decades-old … estimates of total groundwate­r storage,” according to the new studies, which were published in the journal Water Resources Research.

Richey’s studies use 11 years of data from NASA satellites and include a number of other factors, such as population, climate and how people use water.

The twin satellites — known as Gravity Recover and Climate Experiment, or GRACE, satellites — orbit the Earth and measure the gravitatio­nal pull of water over time. The difference in measuremen­ts over time shows how much water the aquifers are gaining or losing.

The researcher­s said the world’s groundwate­r reserves are probably far smaller than previously thought.

The satellite data are just a start, Richey said. Only extensive, on-the-ground research and drilling can determine just how much groundwate­r an aquifer might have.

Jay Famigliett­i, senior water scientist at NASA’s Jet Propulsion Laboratory and a UC Irvine professor, said that aquifers should be studied and valued the same way as precious oil reserves. “We need to drill for water the same way that we drill for other resources,” said Famigliett­i, who worked on both of the studies.

Doing this isn’t easy, researcher­s acknowledg­ed. Groundwate­r basins usually are located in deep, thick layers beneath the earth’s surface, making it costly — and challengin­g — to drill down to bedrock to find out just how deep the water goes. In drier regions, the groundwate­r could be as deep as 2,000 feet.

“We have the technology, but we need the resources to do this exploratio­n,” Richey said.

“We continue to pump in regions like the Central Valley without knowing how much water is in storage,” Richey said. “We need more study. We need better management.”

Richey’s research team included co-authors from NASA, the National Center for Atmospheri­c Research, National Taiwan University and UC Santa Barbara.

 ?? Bob Chamberlin
Los Angeles Times ?? FARMERS ARE
drilling new, deeper wells to tap dwindling groundwate­r near the Central Valley town of Portervill­e.
Bob Chamberlin Los Angeles Times FARMERS ARE drilling new, deeper wells to tap dwindling groundwate­r near the Central Valley town of Portervill­e.
 ?? Justin Sullivan
Getty Images ?? WELL WATER is pumped from the ground in Tulare, Calif. The Central Valley’s aquifer is highly stressed, new studies on the global water supply reveal.
Justin Sullivan Getty Images WELL WATER is pumped from the ground in Tulare, Calif. The Central Valley’s aquifer is highly stressed, new studies on the global water supply reveal.

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