A Look at Groundwater Recharge

Flooding the orchard during the dormant season at $40 to $100 per acre-foot recharged is the least costly option for groundwater recharge (photo courtesy Don Cameron, Terranova Farms.)

One of the most cost-effective methods for bringing California’s groundwater basins into compliance with the Sustainable Groundwater Management Act is managed groundwater recharge.

Almond Board of California’s Training Tuesday session on Feb. 2 offered some advice for growers who may want to ‘get their feet wet’ with groundwater recharge in their orchards.

Jesse Roseman, ABC policy analyst for environmental and regulatory affairs, noted three options for growers who want to attempt groundwater recharge: flooding orchards during the dormant season, building and maintaining their own recharge basins or installing a subsurface recharge system prior to planting an orchard.

Flooding the orchard is the least costly option at $40 to $100 per acre-foot recharged. Recharge basins can take advantage of a particularly sandy area, but take land out of production. The third option involves installation of reverse tile drains and is the most expensive option. UC and ABC research has shown there are no negative impacts to almond orchards from flooding during dormancy. Growers considering flood recharge need to be aware of soil conditions that will limit this option.

Daniel Mountjoy, director of resource stewardship with Sustainable Conservation, said that incentives for landowners to recharge groundwater are being used by some irrigation districts. Some make direct payments while other districts offer discounted water or pumping credits. There are also lease options. Natural Resource Conservation Service is working on a cost-sharing plan, Mountjoy said.

Fresno County diversified grower Mark McKean shared his experience with flooding orchards to recharge groundwater. In orchards where soils support this practice, McKean said he found that, rather than long periods where large amounts of water are applied, shorter bursts of water work just as well and orchard access is not an issue. He uses berms to control the water and drip system to meet ET requirements of the trees. Planning ahead and making changes in nutrient management are important, McKean said. He has decreased his postharvest nitrogen application to 5%, noting that if recharge is to work in the long run, growers will have to recognize and implement practices to prevent nitrogen leaching.

Greg Wegis, Kern County grower and land manager, recounted his experience installing a subsurface recharge system in the Semitropic Irrigation District. The reverse tile drain system was installed in a 40-acre block prior to planting trees. This system, Wegis said, will increase his ability to bank water for longer periods of time in peak flow years. It also eliminates risk of nitrogen leaching.