“Growers are experimenting with a lot of alternative approaches to recharge and being creative in how they determine what works best for their orchards,” Roseman said.
(April 10, 2020) – While groundwater recharge is not a new concept for the California almond industry, interest is continuing to grow. As pressure on the state’s aquifers continues to rise, innovative industry members are considering all options for how to grow almonds while also supporting groundwater sustainability. Recharge, executed correctly, allows growers to do their part in replenishing underground aquifers, supporting agriculture long-term while protecting the health of their trees.
“On-farm recharge is a relatively new practice, but growers are experimental,” said Jesse Roseman, principal analyst for Environmental and Regulatory Affairs at the Almond Board of California (ABC). “If you’re facing a future with reduced water supply, you’re even more willing to try new things.”
If the overflow attendance at a breakout session devoted to recharge at The Almond Conference (TAC) 2019 is any indication, Roseman is right – interest in recharge is gaining momentum.
“Growers are experimenting with a lot of alternative approaches to recharge and being creative in how they determine what works best for their orchards,” Roseman said. “It’s exciting to see the industry share ideas and contribute to conversations on how working lands can help balance groundwater supplies.”
The fundamentals of recharge
Groundwater recharge involves purposely flooding an orchard, pond or fallow field when water is available in order that a certain amount of water may percolate into the aquifer, replenishing supplies that are needed for future irrigation, drinking water and the environment.
In terms of timing, recharge can take place during any season. Winter and spring can bring flood flows that provide more rain and snow than normal. In the fall, dams release large amounts of water that can create space for winter runoff. And during the summer, there may be opportunities for irrigation districts to provide water for banking.
Even though this past winter delivered below-average rain and snow – limiting recharge possibilities when almond trees were dormant – it’s never too early to begin preparing for the next opportunity.
Optimizing how groundwater is recharged will help almond growers and other crops adapt to a future where groundwater pumping in California is dependent on sustainable management.
According to the Public Policy Institute of California’s Water Policy Center, intentional groundwater recharge efforts could fill about 25% of the gap between current supply and demand for groundwater in the San Joaquin Valley, putting up to 500,000 acre-feet of water back into aquifers each year.
“For almond growers, recharge may mean applying flood water in the dormant season, but it also may mean working with other land owners,” said Roseman. “And the solution is not always going to be in almond orchards – it will depend on local conditions in your area.”
No “one size fits all” solution
There are several options for growers considering how to perform groundwater recharge. The simplest way involves using existing flood irrigation systems in the winter dormant season when there is excess water.
If a flood irrigation system isn’t available, the soil doesn’t drain well or other obstacles occur, alternatives, as discussed at the TAC 2019 session, include:
- installing a groundwater recharge pond outside the orchard,
- fallowing an area that’s best suited for recharge to develop a pond (sandy areas are best), and
- working with a local Groundwater Sustainability Agency (GSA) to develop recharge projects elsewhere in their local basin.
Roseman said initial research conducted by University of California (UC) Davis Associate Professor Helen Dahlke and her team suggests that saturating orchards during the dormant season is safe for trees and their roots, but that issues could occur if too much water is applied during the growing season.
“Once trees come out of dormancy, they need to ‘breathe.’ You also don’t want to increase the potential for disease in your orchard,” Roseman said.
He also said growers also should consider nitrogen management when designing recharge projects in order to limit nitrates moving past the root zone into the groundwater.
Soil conditions, location make a difference
Not all orchards are a good fit for recharge: several ABC-funded research projects are exploring how soil conditions and subsurface composition may optimize recharge .
In one project, Dahlke and her research team are seeking to understand how water infiltrates into the soil, identifying underground pathways that can make percolation uneven.
A second study being conducted by Dr. Rosemary Knight of Stanford is exploring if remote sensing can help pinpoint the best areas for recharge, whether in orchards, fields, basins or other areas.
The Almond Board also has invested in developing maps that show areas with the greatest groundwater recharge potential for all almond orchards in California. Data from the maps, developed in partnership with Land IQ of Sacramento, indicate that in 2016 nearly 675,000 acres of almond orchards were located on soil that is moderately good or better for groundwater recharge. Growers can visit Almonds.com/Maps to see where those orchards are located.
In addition to ABC’s partnership with Land IQ, in May 2019 ABC renewed its agreement with the nonprofit Sustainable Conservation to further coordinate efforts to promote recharge and improved groundwater management. This organization has partnered with California farmers for decades to help address some of the state’s most pressing environmental challenges in ways that support agriculture and communities.
“Sustainable Conservation is playing an important role statewide as they’re co-leading with DWR the development of the Flood Managed Aquifer Recharge (FloodMAR) strategy, which seeks to maximize the use of working lands for recharge,” Roseman said. “They are also working with farmers who are creatively developing on-farm recharge solutions that we will need to address the challenges of SGMA.”
Want to recharge? Start planning now
Growers who may want to try on-farm recharge should plan ahead and put steps in place ahead of the next dormant season. Before conducting recharge, growers will likely need to coordinate with their local irrigation district or Groundwater Sustainability Agency (GSA. Beyond that, having water available for recharge is only the first step as growers will need to decide how to recharge and ensure proper nutrient management, among other considerations.
The Almond Board offers multiple resources for growers interested in learning more about groundwater recharge, including the articles “Where Might Almonds Fit into Groundwater Recharge?” and “Is Groundwater Recharge Right for You?,” which walks growers through the factors they should consider before trying recharge. Growers are also encouraged to check out this YouTube video where Dahlke discusses her team’s work in this area.
