Background: To ensure the state’s water resiliency, the California Department of Water Resources passed the Sustainable Groundwater Management Act (SGMA) in 2014 to regulate and monitor groundwater supplies. SGMA mandates that each California groundwater basin form a Groundwater Sustainability Agency (GSA) and develop a water budget. GSAs need accurate estimates of groundwater extraction, both to develop water budgets and to monitor groundwater extractions over time. While flow meters are the ideal way to track groundwater withdrawals, they are not widely adopted in many areas of the state. The current recommended alternative to flow meters is a groundwater model developed by DWR called C2VSIM, which estimates groundwater extraction as a secondary output of the model. The extraction estimate in C2VSIM is based on a crop water demand model that relies on limited data sources, and is insensitive to changes in the water use behavior of growers.
Project: Through a small scale pilot study completed in 2018, CWEE demonstrated that the Efficiency Lift Method (ELM) can produce reliable estimates of groundwater extraction at the individual farm level and at larger spatial scales. The ELM makes use of electricity data and estimated or measured pump operating conditions to calculate groundwater extraction. Since the estimates are generated from electricity usage at the pump level, groundwater extraction estimates from the ELM do not rely on any assumptions about farmer behavior, and can measure true water usage more precisely than any crop water demand model. In phase two of the analysis, CWEE researchers are replicating, verifying the findings, and improving the methodology in a larger study area with increased availability of measured groundwater extract data. The resulting research will report on the feasibility of creating a statewide system for using electricity data to estimate groundwater extraction, including estimating costs to set up and maintain the analysis.
Geographic locations of study: Salinas Valley, Pajaro Valley, San Joaquin Valley, and Coachella Valley.
Peer reviewed publication: “Estimating Agricultural Groundwater Withdrawals with Energy Data” (Phase 1) https://ascelibrary.org/doi/10.1061/(ASCE)WR.1943-5452.0001348
