Requirements to balance supplies in California groundwater basins have refocused attention on how best to achieve recharge, and on what's known as the conjunctive use of surface and groundwater supplies.
Some irrigation districts have been recharging groundwater in that manner for years or even decades.
In Fresno County, recharging the groundwater aquifer has long been a priority for the Selma-based Consolidated Irrigation District, which serves 5,000 farmers across 120,000 acres. Consolidated General Manager Phil Desatoff said the district has actively recharged groundwater since the 1920s by diverting floodwater to recharge ponds, which are now spread across 1,400 acres.
"The old-timers started putting water in the underground when it was available. A lot of times it was unintentional, because the river was flooding, but they saw how it worked so they started putting water on the low spots," Desatoff said, adding that the district uses Kings River water for irrigation and groundwater recharge.
"Our farmers have been paying for recharge for 100 years," he said. "But now, with SGMA (the Sustainable Groundwater Management Act), you've got other folks looking to capture floodwaters doing the exact same thing we're doing."
Adopted in 2014, SGMA sets milestones that must be met to achieve groundwater sustainability. The law requires formation of local groundwater sustainability agencies—or GSAs—to guide groundwater management in basins and sub-basins classified by the state as medium or high priority. The local agencies must work together and with groundwater users to develop sustainability plans that will guide decisions affecting groundwater use and fees.
In the Consolidated district, irrigators rely mostly on surface water and are able to meet their needs with supplemental groundwater through the conjunctive-use program. The success of the district's ability to add to the groundwater aquifer, Desatoff said, is due to its coarse, sandy soils that offer an average percolation rate of 1.1 acre-feet per day, more in some areas.
Due to its long history with groundwater recharge, Desatoff said, Consolidated will be ready for SGMA and has the ability to sell water to nearby districts.
"We are going to be in balance—in fact, we're almost in balance now," he said. "We're probably going to do deals with some of the folks around us, to help us do recharge and put in more recharge basins to help the entire basin."
Districts lacking water want to buy it, Desatoff said, "so they will have to go to someone who has access to surface water, so districts like mine that either have a lot of surface water or groundwater or a combination are prime sources to meet demand."
To the north, the Merced Irrigation District also operates as a conjunctive-use district, providing surface and groundwater supplies for about 100,000 acres.
Merced Irrigation District Deputy General Manager Bryan Kelly said the district has been focused on groundwater recharge for many years, operating two basins that receive stormwater captured in MID canals and waterways and 220 active groundwater wells.
"We deliver surface water and in times of drought, we sometimes supplement with groundwater, and we've operated that way for decades," Kelly said. "On average, we replenish 140,000 acre-feet of recharge from all of our groundwater recharge activities."
Through its conjunctive-use management activities "and just being a good steward," he said, the district recharges the groundwater aquifer when it can through two basins: the Cressey-Winton Recharge Basin, which first received flows in 2011, and the El Nido Recharge Basin, constructed about 10 years ago. The Cressey-Winton basin spans 20 acres and can replenish about 50 acre-feet per day with surface water flows from Lake McClure. The El Nido basin, on about 18 acres, can replenish 18 acre-feet of groundwater per day, Kelly said, with flows from Mariposa Creek.
"The Cressey recharge basin is one way we help to replenish the groundwater and to conjunctively manage the surface water and groundwater resources," Kelly said. "It is just one of many tools in the toolbox. Whenever there is available surface water supplies, we are recharging water to the basin. We use it as much as we possibly can."
Farmer Gino Pedretti III, whose farm is near the El Nido recharge basin, said "groundwater recharge is going to be vital to keep production agriculture going in our area," adding that this is especially true given requirements under SGMA plus State Water Resources Control Board approval of a plan to require districts along the Merced, Stanislaus and Tuolumne rivers to leave 30 to 50% of "unimpaired flows" in the rivers to help fish.
Given that combination, Pedretti said, "I could easily see in dry years, 50% of our ground being fallowed in the Merced sub-basin."
Pedretti, who serves as president of the Merced County Farm Bureau, said even though his irrigation district has its own recharge area, "recharge is also vital for the 'white areas' outside district boundaries. In years that the district has excess water, selling that water to neighboring farmers is what is going to keep agriculture in our area going."
David Guy, president of the Northern California Water Association, likened balancing groundwater under SGMA to managing a bank account.
"Everybody's going to provide their GSPs (groundwater sustainability plans) next year or in three years and then, like any bank account, when we see that we're overdrafting, we try and earn more money or we cut our expenses," Guy said. "We're going to recharge groundwater every opportunity we have. I do think that SGMA's going to bring groundwater recharge very much into focus over the next several years."
(Christine Souza is an assistant editor of Ag Alert. She may be contacted at email@example.com.)
Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.