Enough water for 11 million households went into California aquifers this year. Why it’s only a start

State water authorities estimated that 3.8 million acre-feet of water went into depleted underground reservoirs this year after a record winter of rain and snow. That’s about how much water more than 11 million California households will use annually.

The figure released Wednesday was praised by officials as a boon to depleted groundwater basins after decades of overpumping during drought. But it’s going to take years of rain and effort from local water agencies to reach sustainability, said experts and advocates.

“We took a pretty creative approach on how to deal with atmospheric rivers,” said Paul Gosselin, deputy director of the Department of Water Resources’ sustainable groundwater management office. “This one year is going to improve conditions but it’s also not the end of the story, and it may only scratch the surface.”

California’s Central Valley has a groundwater deficit that ranges between 2.3 and 7.0 million acre-feet, according to a study of NASA satellite data. A single acre-foot is equal to roughly 325,000 gallons and can serve about three households in a year.

DWR’s estimate, which is based on project reports and permit records, far exceeds a goal set by Gov. Gavin Newsom to refill depleted reservoirs by an average of 500,000 acre-feet per year.

Yet the smallest contribution came from Newsom’s executive order waiving permits amid the winter’s atmospheric river storms, which the agency said put 92,410 acre-feet of flood water underground.

The vast majority came from pre-existing projects — water banks and surface water diversions — amounting to over 2.1 million acre-feet. State Water Board and Bureau of Reclamation programs to streamline permits account for approximately 1.2 million acre-feet, with another 117,000 acre-feet in permits from state grants.

The agency will issue a complete calculation by April, after the deadline for local groundwater agencies to submit annual reports to the state.

“Nature brought a lot to the table and then through human efforts and coordination, we enhanced that,” said Gosselin. “I think it’s safe to say that up and down, the Central Valley had great benefit from recharge and flood diversions.”

Underground water stores make up 40% of California’s supply for farms, cities and households. State agencies estimate their total capacity at somewhere between 850 million and 1.3 billion acre-feet.

In the Central Valley alone, researchers say, groundwater basins can hold three times as much water as California’s surface reservoirs. But the critical water source has been in steep decline since the 1960s, mainly because agricultural pumping during drought outpaced natural replenishment in wet years.

California’s 2014 Sustainable Groundwater Management Act (SGMA) aims to address this problem by 2040. A key piece of the sweeping law will include local agencies intentionally flooding plots of land with porous soil to let water seep underground, called groundwater recharge.

Graham Fogg, a professor emeritus of hydrogeology at the University of California, Davis who studied California’s water systems for 40 years, gives the state’s efforts on recharge this year a B+.

“These apparent recharge numbers are a positive sign, but are really just a start, and reflect only part of what needs to happen for California to stabilize its water resources,” he said. “This will not happen in just one year, and likely not in just one decade.”

More recharge projects need to come online for the next wet year, he said, and there should be reductions in pumping during the next drought. Tracking the changes in net groundwater storage should be the goal, not ad hoc recharge estimates.

Groundwater is tricky to measure and there’s currently no database for aquifers in the way anyone can look at today’s level for any surface reservoir. But recently, the state has conducted aerial surveys and used electromagnetic imaging to map recharge zones.

Historical reluctance by the state’s private landowners is also beginning to change. The North San Joaquin Water District purchased a 10-acre plot of land this year for recharge, and flooded an abandoned 80-acre vineyard for the same purpose.

“I think anything we can do is helpful,” said board president Joe Valente, who grows wine grapes and almonds in Lodi. “When SGMA came along, people were upset about it. But on the positive side it got people working together and thinking outside the box.”

Farmers are not alone in their dependence on groundwater. A recent report from the Nature Conservancy and Union of Concerned Scientists found that the majority of groundwater sustainability plans under SGMA fail to protect less organized and powerful stakeholders.

Those include households that rely on shallow wells for drinking water. Agricultural overpumping during California’s recent extreme drought left a handful of communities, home to mostly low-income Latino residents, without running water.

Nataly Escobedo Garcia, water policy coordinator at the Leadership Counsel for Justice and Accountability, wants to see recharge that prioritizes the needs of domestic well users and small water systems. That includes groundwater quality and managing demand during the next drought.

Even now, some 43 wells reportedly went dry in the state this month, mostly in the San Joaquin Valley. To date this year, 316 wells were reported dry.

“For the folks whose wells have been dry since 2020, this unfortunately doesn’t mean much for them,” Escobedo Garcia said. “Some of our worries with celebrating a wet year a little too much is false confidence about where our aquifers are actually at.”