California’s biggest agricultural region also has the state’s biggest groundwater deficit, which has long-term consequences for the region’s economy and farming.
The San Joaquin Valley — where decades of unchecked pumping has depleted reserves, resulting in a long-term deficit of nearly 2 million acre-feet per year — has about a generation to bring its groundwater use into balance to comply with the state’s Sustainable Groundwater Management Act. Storing more water underground through “groundwater recharge” can help, reducing the deficit by as much as a quarter.
But this would require putting much more water into groundwater basins in wet years than is currently possible because it is mainly available over a short period of time when rivers are flowing at very high levels.
Although recharge is not a panacea, it is a vitally important tool for getting to groundwater sustainability.
We reviewed local efforts after the very wet winter of 2017 and found widespread recharge efforts but also significant hurdles.
Our new research released this week shows that improving the capacity to recharge requires concerted actions by local, state, and federal partners.
The State Water Board should develop a streamlined process for water users to capture surface water when it is available. Beyond establishing legal rights for diversion and storage, it is essential to develop a simple, rapid way to determine when river flows exceed water required for the environment and downstream users.
A key challenge is that most available flows are in the northern part of the valley, while most of the overdraft and best recharge potential is in the south. So a top priority is to make better use of existing infrastructure (canals, reservoirs and recharge basins) and to determine where additional investments are warranted.
Recharging farmland is one of the most cost-effective ways to capture water in wetter years, but it is underused. Ramping it up will require addressing technical issues and establishing incentives.
State and federal agencies need to improve the process for approving construction of new recharge projects, moving recharge water through their conveyance facilities and allowing more flexibility in where water is stored. Farmers also need guidelines for recharge that complies with water quality rules.
Better accounting of water going into and out of groundwater basins is key to sustainable management. It’s also needed to develop incentives for growers, encourage partnerships and make informed decisions on new investments.
Finding the right mix of policies, regulations and incentives to encourage more groundwater recharge is still a work in progress. One thing is clear: cooperative efforts hold great promise. As water districts and water users develop sustainability plans, partnerships between cities and farming areas and surface water “haves” with “have nots” can increase the chances of success.