Underground water sources are critically important in the United States. Groundwater supplies around 35 percent of America’s drinking water, and farmers rely on aquifers for crop irrigation, livestock production, and other agricultural needs. However, aquifers do not have an infinite amount of water. Across the country, they are drained faster than replenished, leaving communities without the water they once depended on and even causing the ground to sink and open up in some locations. 

Natural recharging, where water trickles through soil into the aquifer on its own, is not fast enough to combat depletion. Is there a way to reverse course? New data shows there might be. Ironically, the same farmers who once helped drain aquifers could now play a role in recharging them. 

California has one of the worst cases of rapidly depleted groundwater in the nation. The study ranking the world’s 100 worst cases of aquifer depletion included six locations within California alone. Recharging aquifers is an urgent necessity in the state. 

Rosemary Knight, professor of geophysics at the Stanford Doerr School of Sustainability, had studied groundwater depletion across California and became interested in ways to reverse the problem through managed aquifer recharging. Managed recharging most commonly involves flooding a piece of land with excessive water, allowing the water to seep through the soil and be stored within the aquifer below. Recharging has been deployed worldwide and is being increasingly used here in the United States—the National Ground Water Association is even holding a conference on the topic later this year. 

Knight and her team set out to test if manual recharging could be more efficient. They pulled a significant amount of electromagnetic data that the California Department of Water Resources had obtained by doing a grid search over the Central Valley with specially equipped helicopters. The equipment sent an electromagnetic signal into the ground to track how the electrical current traveled through the soil. Areas where water easily flows do not conduct electricity well, and that information showed up in the data. 

With this information at their fingertips, Knight’s team created a three-dimensional model showing the points in the Central Valley where water would flow through the soil fastest. These findings, recently published in Earth and Space Science, found that between two and seven million acres of land in the Central Valley, between 19 and 56 percent of the valley’s total area, are suitable for manual recharging. Most of this land is currently dedicated to growing crops. 

Knight and her team have made their model available online. The data may inform regional agencies across California as they develop water management plans. Knight also hopes that having publicly available data will empower farmers and landowners to explore sustainable water and soil management practices, arguing that agricultural producers want to be a part of the solution: 

“I care about actionable data presented in a way that is helpful to end users, such as growers, managers of water districts … the user can make their own decisions about how best to use the results.”

If individual stakeholders use this modeling data to target specific areas for manual recharge on their land, it could set a precedent for water management practices across the country. Agriculture may drain a lot of water from aquifers, but it’s also part of the solution. 

The views and opinions expressed are those of the author’s and do not necessarily reflect the official policy or position of C3.