San Joaquin Valley 2017 Recharge Demonstration Sites

Project Summary

The Sustainable Groundwater Management Act, signed into law in 2014, requires a balance of pumping and recharge to be established in medium to high priority basins by a date dictated by the region’s overdraft severity. Many medium to high priority basins reside on agricultural land due to the regions dependence on groundwater pumping for crop use. Therefore, farmers are participants in mitigating groundwater loss. On – Farm Recharge (OFR) necessitates use of surplus surface water during the wet season or recycled water to apply to agricultural fields. OFR is a best management practice (BMP) with dual benefits: (1) it incentivizes farmers to use a water source outside of groundwater for crop uptake (in – lieu recharge) and (2) if soil field capacity is achieved, the water percolates to the water table (direct recharge). Both types of recharge aid in reducing groundwater decline.

OFR was performed and studied on almond, grape, walnut and pistachio fields at seven locations in the San Joaquin Valley. Each location contained a test and control site with the same crop and soil characteristics. The test site was designed to receive OFR, while the control site was designed to receive water from either a flood irrigation system of a drip irrigation system, depending on farm equipment available. Surface water, taken either directly from surplus river flow or from irrigation districts, was delivered to fields via flood irrigation systems. Instruments were installed at all sites to continuously measure field surface water depth and soil moisture (volumetric water content, VWC) with depth through the soil profile. Oxygen (O2) levels were measured at four sites: pistachio, almond, and walnut sites, and a control almond site.

The seven locations provided recharge quantities, infiltration rates, and soil conditions during OFR. In the 2017 recharge demonstration, six test sites and three control sites received direct recharge, while at one location, both test and control site only received in – lieu recharge. Unfortunately, not all 2017 OFR events were recorded because OFR began before instrument installation at some locations.

1. S.M. Bachand, R. Hossner, P.A.M. Bachand. 2017 OFR Demonstration Site Monitoring and Analyses: Effects on soil hydrology and salinity, and potential implications on soil oxygen. Developed For Sustainable Conservation, San Francisco, CA. Available Through Sustainable Conservation, “Sustainable Conservation”, Published: January 28, 2019.

2. Bachand, S., P.A.M. Bachand, D. Mountjoy, l. Asgill, J. Choperena “Groundwater Recharge on Farmland: Challenges and State of the Practice”. 2019 Conference Proceedings California Plant and Soil Conference. American Society of Agronomy California Chapter Co-Sponsored by the Western Plant Health Association. February 5-6, 2019. Fresno, CA.