Issue link: https://www.e-digitaleditions.com/i/1369084
WATER USE New ABC Resource Dives into Groundwater Recharge With California's ebbs and flows of dry years and irrigation demand outpacing supply, as well as increased regulation of groundwater pumping, finding enough water to produce an almond crop each year is enough to keep growers up at night. At least part of the solution may be for growers to figure out how to save, not for a rainy day, but to save the rainy day itself. Groundwater recharge, or intentionally refilling underground aquifers using flood flows and released water from reservoirs, could help individual growers and the almond industry as a whole successfully address what may be an increasingly water-scarce future. As discussed at The Almond Conference 2020 panel, "Overcoming Challenges to Maximizing Groundwater Recharge," agricultural recharge can also be part of multi-benefit projects, such as improving aquifer drinking water quality for disadvantaged communities and flooding fields for migratory birds. "When the Almond Board of California (ABC) set out to do research in recharge, we started early," said Jesse Roseman, ABC's principal analyst for Environmental and Regulatory Affairs. "We have a lot of acreage in the Central Valley and the majority of almonds are in overdrafted groundwater basins. We see a great opportunity to explore increased adoption of recharge to help balance our water supply for multiple purposes." What should growers consider when deciding whether to pursue groundwater recharge in their orchards? This question is answered in a new ABC resource: "Groundwater Recharge Guide for Almond Growers." This new resource aims to walk growers through initial considerations for whether groundwater recharge is a good fit for their operation and, if so, what type will work best. Factors to consider include: availability of surface water – secure supplies are fundamental to being able to do recharge, appropriate soil type – recharge works better in sandy loam and similar well-draining soils, subsurface conditions – underground sand and clay layers may help or inhibit recharge, and necessary management changes – different methods have variable requirements for integrating recharge into an orchard operation. ABC-funded research conducted by University of California Cooperative Extension researchers, in partnership with Sustainable Conservation, 1 has shown that "on-farm recharge" – intentionally flooding orchards to encourage groundwater recharge – is safe in well-drained soils during December and January when trees are dormant and flooding will not harm trees or future yields. Other important considerations involve avoiding unintended consequences, such as pushing crop nutrients past the root zone into groundwater. This can be avoided by making sure proper nutrient management is carried out in orchards where recharge takes place. Growers should also avoid nutrient applications immediately before a recharge event, as recently applied nutrients may be lost with recharge, reducing tree benefits and harming water quality. From an Integrated Pest Management perspective, growers should remain vigilant in monitoring for diseases and responding when treatment is needed. Recharge increases moisture in orchards, which can lead to an increased risk of certain fungal and mold diseases in almonds, such as Phytophthora, Alternaria and hull rot. For this reason and others, in-orchard recharge via surface application of excess water during the growing season is currently not recommended. To implement recharge efficiently, growers will need to have the ability to move water into the orchard and hold it there long enough to percolate, using either existing or temporarily installed flood irrigation systems and berms. Other recharge opportunities While applying surplus water to orchard floors is one of the most cost-effective ways to perform on-farm recharge, this groundwater resource also provides options that don't require flooding the orchard. On-farm dedicated groundwater recharge basins in select areas may require removal of trees but otherwise avoid ongoing impacts to orchard operations. They can be expensive to Research shows that intentionally flooding orchards to encourage groundwater recharge is safe for the orchard when the trees are dormant. 1 Sustainable Conservation, a nonprofit organization that promotes collaborative solutions to address the state's land, air and water challenges, has been a longtime collaborator with ABC. Learn more at www.suscon.org. See also https://prn.to/31GJsmQ 5