Almond Orchard OFFCR

On-Farm Flood Capture and Recharge (OFFCR) at an Organic Almond Orchard, Recharge Rates and Soil Profile Responses in Chowchilla, CA

Project Summary

The Central Valley is critically overdraft in most of its regions. The severity of groundwater loss lead to the development of the 2014 Sustainable Groundwater Management Act (SGMA). Groundwater Sustainability Agencies (GSAs) are preparing Groundwater Sustainability Plans (GSPs) to mitigate further groundwater loss and strive towards hydrologic health. Farmers and other stakeholders will need to comply with regulations set by GSAs to achieve SGMA goals. On-Farm Floodwater Capture and Recharge (OFFCR) is a potential management strategy for farmers seeking to reduce their groundwater dependence. 

In this project, OFFCR was studied at an organic almond orchard. Flood irrigation was applied at three recharge treatments each including: (1) a control site, 6 in of water applied to meet ET as typical for irrigation, (2) a low flooding site, 12 in per irrigation application (mid treatment), and high flooding, and (3) 24 in per irrigation application (high treatment). Soil sensors were installed to monitor moisture and salinity. We monitored agronomic practices, recharge loading, and crop yields. We also took post-irrigation deep cores to assess changes in soil and porewater nutrient and salt concentrations.

Within the vadose zone, 0-48 inches, the soil profile did not reach saturation at any of the test sites, indicating that recharge did not cause anoxic conditions for the crop. The duration of water content above field capacity at 48”, and hence the duration of recharge, was extended in the mid and high treatments. At the control site, there was no drainage past the root zone. DON peaks were found in the shallower zone in control treatments and at deeper depths at recharge sites, indicative of piston flow.  The more water is applied, the greater number of constituents are flushed out of the root zone. Overall, the project resulted in significant recharge during the summer season, 6 ft, and water quality loading and concentration decreases. Crop yields did not appear to be affected.