The efforts are paying off. In some wells, water levels are measuring 15 to 20 feet higher than before this wet season. Fukuda believes that by pairing wet-year recharge with management of pumping, the district can minimize the need to leave farmland fallow.
California state officials preliminarily estimate a total of at least 3.8 million acre feet have been recharged across the state this year, including both on-farm and other efforts, though more data will be confirmed next year.
Amid this winter’s deluge, Sustainable Conservation — which has been supporting on-farm recharge — heard from many other districts interested in implementing the approach in their areas.
“This has really been the catalytic year,” Mountjoy says.
In addition to helping to stabilize groundwater stores, the practice has promise to help mitigate subsidence, according to Mountjoy. Though aquifer recharge won’t raise ground that has already sunk, Mountjoy says, it may be able to stop it from sinking further. It can also help with flood mitigation, diverting some high waters away from rivers and reducing the impact of inundation to communities downstream.
The method essentially leverages farmland to address an existential problem in California: When you receive too much water, how do you not only manage the flooding, but also store that water for future years when you don’t get enough?
“You need recharge basins and on-farm recharge to capture the big gulps in years like this,” Mountjoy says.
While on-farm aquifer recharge is gaining popularity, on its own the practice will not be enough to completely address the region’s groundwater overdraft. Researchers estimate that up to 25 percent of the San Joaquin Valley’s groundwater depletion can be addressed by returning water to the ground.
Recharging aquifers and then continuing to use water at the same rate is “a risky bet,” notes Hannah Waterhouse of University of California Santa Cruz, a soil biochemist who has studied on-farm recharge.
“There needs to be decreases in pumping,” Waterhouse says. “That has to be a part of the story.”
Using farmland to replenish aquifers also raises questions about implications for groundwater quality, according to Waterhouse. As water trickles down into the aquifer, it carries with it nitrate from excess fertilizer, a contaminant linked to negative health consequences. Putting large amounts of water on fields could potentially flush older built-up nitrate into the groundwater supply.
But Waterhouse says research models have found that, if fertilizer use is reduced, adding water to the depleted aquifers could improve groundwater quality by diluting the nitrates already in there. This could help restore drinking water to communities where wells have run dry.
Meanwhile, after irrigating 40 acres of almond orchards this winter, the groundwater level on Gemperle Orchards rose by about a foot.
Christine Gemperle says that the farm took a total of 44 acre feet in stormwater –– nearly double the 26 acre feet of well water that the farm used during the drought in 2022.
The trees don’t seem to have been harmed by the process, Gemperle says, and the young ones have put on about four feet of growth. Water was restored to her neighbor’s well, too, which ran dry last year.
Gemperle budgets groundwater carefully, and plans water use to try to keep it healthy. Recharging the aquifer helps the small family farm prepare for uncertain weather ahead.
“It’s nice to have that backup,” Gemperle says. “With climate change, in order to be resilient, we have to be super flexible.”
