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Analysis says to end Valley’s groundwater overdraft, farmland must be retired

A federal Central Valley Project pumping plant near Tracy delivers water to the San Joaquin Valley from the Sacramento-San Joaquin Delta. The Trump administration wants to increase deliveries.
A federal Central Valley Project pumping plant near Tracy delivers water to the San Joaquin Valley from the Sacramento-San Joaquin Delta. The Trump administration wants to increase deliveries. Sacramento Bee

The San Joaquin Valley is on the brink of a major transition as it seeks to balance its groundwater accounts. California’s largest farming region has the state’s biggest groundwater deficit — almost 2 million acre-feet per year by our estimates. To put it in context, that’s about one Don Pedro Reservoir’s worth of water a year.

Groundwater overdraft — pumping more than is replenished over the long term — makes wells go dry, increases energy required to pump water and causes land to sink, which in turn damages major regional infrastructure. These harmful impacts have become increasingly costly to address.

The state responded to this challenge by mandating that areas with shrinking groundwater supplies bring their basins into balance by the 2040s. To attain balance, groundwater sustainability agencies in the Valley will have to increase supplies, reduce demands, or both.

Our new research includes a detailed analysis of a wide range of options to address this deficit. Although ending overdraft will bring long-term benefits, it entails near-term costs. We find that only about a quarter of the Valley’s groundwater deficit can be filled with new supplies at prices farmers can afford. The rest must come from managing demand. We estimate that ending the overdraft will require taking at least 500,000 acres of irrigated cropland out of production.

In addition to water scarcity, the Valley also must deal with a host of other related issues. These include poor groundwater quality, a lack of safe drinking water in rural communities, and a degraded natural environment. Top priorities for addressing these linked issues are:

▪ Capture more local runoff. The best option for increasing supply is capturing and storing additional water from big storms. In particular, recharging groundwater could deliver significant new supplies at a cost farmers can afford. Coordinating management of surface and groundwater storage — both locally and across the entire Central Valley — can also help boost overall water storage capacity. In contrast, big investments to increase water imports — for example, California WaterFix or expanding Shasta Reservoir — are relatively expensive for Valley farmers.

▪ Expand water trading. Trading water can significantly reduce the costs of ending groundwater overdraft, because it allows farmers to maintain the crops that generate the most revenue and jobs. Overall, we estimate that if farmers can freely trade water within their basin, it will reduce the costs of this transition by nearly half. And trading more broadly across the region will cut costs by nearly two-thirds.

▪ Address groundwater quality challenges. Providing safe drinking water to rural communities is an urgent priority. Stakeholders in the Valley will also need to work on managing water quantity and quality together, since recharge could affect groundwater quality. For instance, some recharge practices could flush pollutants from soils into groundwater.

▪ Foster beneficial water and land-use transitions. There are opportunities to put lands coming out of production to good use and gain “more pop per drop” from limited water resources. Multiple-benefit approaches to water and land management can enhance groundwater recharge and provide new recreational opportunities, additional flood protection, improved habitat, and new revenue for landowners.

Gov. Newsom has acknowledged the need to address the Valley’s water supply, water quality, poverty, and economic development challenges. State leadership can help on a number of fronts ― including providing clarity on how much water is available for groundwater recharge, establishing a reliable funding source for safe drinking water solutions, and supporting regional planning processes to address these issues.

Although state and federal partners can help, the Valley’s future is in the hands of its residents. A Valley-wide conversation on the changes that lie ahead can help determine the next steps for creating a better future. The stakes are high — but the costs of inaction are higher.

Ellen Hanak is director of the Public Policy Institute of California’s Water Policy Center and can be contacted at hanak@ppic.org. Alvar Escriva-Bou is a research fellow at the PPIC Water Policy Center and can be contacted at escriva@ppic.org. Sarge Green is a water management specialist with the California Water Institute at California State University, Fresno, and can be contacted at sgreen@mail.fresnostate.edu.