and flood irrigation valves and flow meters are necessary. The guide includes common and alternative ways to apply OFR surface water. • Reverse tile drains – This method is considered subsurface groundwater recharge using reverse tile drains. Conventional tile drain systems typically move water out of the soil in fields with high water tables to avoid anoxic conditions that are harmful to crops. The OFR adaptation of reverse tile drains applies excess water below the root zone. The guide says one of the key benefits of a reverse tile drain system is that it does not require saturation of the root zone, thereby allowing water application without impact to growing season considerations. This method can be expensive as pre- planting orchard modifications need to be performed. Ideal soil conditions are sandy loam in the first few feet and a sandy layer below the root zone that extends down to the water table. • Recharge basins – The final OFR method discussed in the guide is recharge basins, which can be built by growers on land adjacent to an orchard or developed on a larger scale by water districts or even Groundwater Sustainability Agencies (GSAs). In the case of growers, OFR basins typically are smaller and serve many functions as flood releases may only be available every few years. Growers may also identify natural depressions or part of their property that has the best recharge characteristics and is less ideal for crop production as mini-basin potential. The time to act is now Recharging aquifers will continue to take on greater importance as the Sustainable Groundwater Management Act (SGMA) is implemented over the next 20 years. SGMA divides California into 515 groundwater basins, 94 of which must be locally managed to preserve and replenish aquifers and tackle the problem of land subsidence. At The Almond Conference 2021 conference session on water, water use expert Scott Hamilton estimated that the San Joaquin Valley is short 3-million-acre feet of water
each year to use for agriculture, domestic and commercial purposes, and environmental uses. Without a comprehensive strategy to recharge groundwater basins, Hamilton estimated that as many as 1 million acres could be taken out of ag production in the Central Valley, amounting to a $7 billion annual hit to the economy. Paul Gosselin, who oversees SGMA as the deputy director of the California Department of Water Resources, said 40% of the state’s water comes from underground sources in an average year. In dry years, however, that figure soars to 60%, underscoring the need to protect aquifers even in the face of more frequent droughts. “Local agencies, growers and farmers must find strategies to reduce groundwater use,” said Gosselin, adding the state “must consider the impact of all groundwater users, including farmers.” He and other panelists encouraged almond growers and others in the ag industry to become involved with their local Groundwater Sustainability Agencies.
“The time is now to build that sustainable future,” he said.
A flooded orchard at Terranova Ranch during groundwater recharge trials. Credit ABC
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