On-farm groundwater recharge could greatly help decrease aquifer overdraft, but recent efforts show that some significant obstacles will need to be overcome.
|WRITTEN BYMichelaina Johnson||PUBLISHED ON|
GROUNDWATER OVERDRAFT IN the San Joaquin Valley – producer of half the state’s agricultural output – has averaged roughly 1.8 million acre-feet annually since the mid-1980s. Even before the start of the most recent drought in 2011, a few San Joaquin farmers recognized the dire need for sustainable water management and started individually pioneering a groundwater recharge practice that has since gained statewide traction.
On-farm groundwater recharge involves intentionally diverting surface or stormwater to agricultural fields for percolation into the aquifer during times of excess. The practice holds tremendous potential for increasing water storage and offsetting groundwater overdraft, but to scale efforts, some serious obstacles will need to be overcome.
Lodi wine-grape grower Al Costa, in partnership with North San Joaquin Water Conservation District and the nonprofit Sustainable Conservation, this year launched a groundwater demonstration project on a 13.7-acre parcel of old-Zinfandel grapes to study the benefits of flooding agricultural fields with surface water to refill the aquifer below. Thus far, 145 acre-feet of Mokelumne River water has inundated the field and percolated into the subsurface, rejuvenating a small fraction of the estimated 100,000 acre-feet of water overdrafted from the aquifer each year. And all this happened with no damage to the grape vines, Costa said.
His project is just one of many projects implemented throughout the San Joaquin Valley that helped capture a share of the past winter’s near record rainfall. A recent survey found that about three-quarters of the 81 San Joaquin water districts surveyed were actively recharging this year. The majority of districts were engaging in some type of on-farm recharge, including extra irrigation on active cropland, inundation of fallowed land or substituting surface water instead of groundwater for irrigation (a method known as in-lieu recharge), said Ellen Hanak, director of the Public Policy Institute of California’s Water Policy Center, which conducted the survey.
Despite an increasing number of districts and growers adopting this practice, its full potential has yet to be realized, as policymakers create frameworks for this emerging method and researchers quantify its value.
“There is not a lot of on-farm recharge being done today, but it’s growing and will continue to grow,” said Joe Choperena, Sustainable Conservation’s senior project manager.