The Central Valley
SGMA
As the agricultural hub of California, the Central Valley faces intense groundwater extraction which has substantial consequences including land subsidence and well depletion. California’s Sustainable Groundwater Management Act (SGMA) mandates that groundwater be sustainably used by 2040. The amount of water extracted from the ground must equal the amount of water being replenished into the aquifers. Because of this, there is increased interest in how managed aquifer recharge (MAR) can help California address groundwater depletion, particularly in the agriculturally intensive San Joaquin Valley. MAR captures available surface water—often during wetter periods—and stores it underground for later use.
We are particularly interested in examining whether proposed MAR projects are both economically realistic and practically achievable. We have analyzed Groundwater Sustainability Plans throughout the San Joaquin Valley and found substantial variation in how project costs are estimated and reported. The results highlight the need for more consistent accounting of expenses such as land, construction, water conveyance, operations and maintenance, and water purchases. Water, itself, may be a major constraint: proposed projects collectively seek more recharge water than current estimates suggest is reliably available, making coordination among local groundwater agencies and water users increasingly important.
We also have examined where and how recharge will actually improve groundwater conditions. Much of the San Joaquin Valley contains the Corcoran Clay, an impermeable layer that can separate shallow aquifers from deeper groundwater systems where substantial pumping and land subsidence occur. Because surface-spreading projects generally recharge shallower aquifers, careful site selection and complementary approaches such as injection wells should be considered.
Overall, we combine economics, hydrology, infrastructure planning, and groundwater management to identify where MAR can be most effective—and how agencies can use it as part of a broader strategy for a more resilient and sustainable water future.