By Dennis Pollock, Ag Alert
There is more than one way to recharge groundwater by using almond orchards, and two growers talked about that in an online forum presented by the Almond Board of California.
One of them, Mark McKean, a principal in McKean Farms in Fresno County, described his trees and the high berms around them that keep water from their trunks.
Greg Wegis, president of Semitropic Farmers for Sustainable Ground Water in Bakersfield, talked of subsurface recharge, and whether the rewards of this more costly recharge method will be worth the risks. He said he believes they are.
“We have to be open to different ways,” McKean said, after remarking during the forum, “We have to take risks.”
Groundwater recharge is seen as one way to make it easier to comply with the Sustainable Groundwater Management Act, a state law that addresses overdraft and improving water quality. Panelists said pursuing recharge has regional benefits that accrue to the individuals who do it as well as their neighbors.
McKean operates a diversified farm, growing winegrapes, almonds, processing tomatoes, cotton, grains, alfalfa and other crops. He said he became involved in recharge in 2010 as he saw pumping levels drop, and experimented with floodwater.
He said soils on his land were variable—some conducive to recharge efforts, others not. Rather than flooding the orchard, he found “short, quick bursts across the field were working just as well.” Many of the times when floodwaters were available were times McKean said he also had to have access to the fields and he did not wish to have water sitting in them for too long. Achieving recharge, he said, brought the added cost of having two irrigation systems, flood and drip.
In 2017, McKean said, he was able to bank about 2.4 acre-feet in one orchard, as well as growing a crop.
He also described his concern about Phytophthora, which can result if trees become waterlogged. He said he hopes there will be more research on Phytophthora and disease-resistant rootstocks, as well as more data on nitrogen leaching. McKean said he has cut the amount of nitrogen he applies in the fall on the orchards where he does recharge.
Wegis, who manages 20,000 acres of almonds, pistachios, row crops and dairies, and farms in nine different water districts, described the subsurface system he had put in.
Tile drain systems for subsurface recharge must be in place before planting. On a 40-acre plot, he began a project putting lines that were 8 feet deep over Corcoran clay.
Surface water from Semitropic Canal was run through a filter. In 2019, 5 acre-feet a day was recharged, Wegis said.
“It never interfered with our cultural practices,” he said. “We don’t have to worry about nitrogen leaching,” adding that the system includes two monitoring wells that showed depth to surface.
Wegis encourages incentivizing of landowners who make efforts to recharge groundwater.
With systems such as his, costs can range from $1,000 to $4,000 per acre, “depending how far apart your laterals are.” With his system, an 8-inch to 12-inch, non-perforated mainline carries surface water from the district to 4-inch to 6-inch perforated laterals 96 feet apart.
Wegis said it’s hard to determine the return on investment, because “you don’t know when the water is going to come and how many acre-feet you are going to be able to bank in those events.”
He has also put in surface basins, which can cost $5,000 to $8,000 an acre, noting that a crop can’t be grown on those basins as can be on a subsurface recharge system.
“We’ve seen surface ponds, basins seal up with silt,” Wegis said.
With the subsurface system, sand filters remove the silt “for the most part,” he said. “Some silt will get by.”
He said much remains unknown about the longevity of the subsurface system.
“I’m not concerned. I think we will get many, many years,” Wegis said.
Daniel Mountjoy, director of resource stewardship with Sustainable Conservation, discussed incentives and rewards for farmers who engage in on-farm recharge.
Mountjoy said examples of recharge incentives for private landowners include financial incentives in the form of district payments and discounted water from districts. There may also be pumping credits and a lease option, and he said the U.S. Department of Agriculture Natural Resources Conservation Service is expected to enter into cost-share agreements soon.
He said local groundwater sustainability plans call for significant recharge, and there are more water right applications for increased high flow diversions: “Catch it when you can.”
“If your land is not suitable for recharge, support incentives for others to recharge, to benefit your shared groundwater basin,” Mountjoy said.
He added that markets for groundwater trading are being developed, and farmers will be allowed to buy and sell groundwater sustainability plan allocations. He said an accounting platform is operational, but trading has not yet been approved.
“There is the potential for farmers to recharge to increase their allocation,” Mountjoy said.
Jesse Roseman, principal analyst for environmental and regulatory affairs with the Almond Board, said groundwater recharge mitigates overdraft and improves water quality, decreases pumping costs, mitigates subsidence, replenishes aquifers and helps secure water supplies during times of drought.
It could help reduce the fallowing of land at a time when nearly a million acres are expected to be idled during the next 20 years as a result of SGMA.