Groundwater recharge projects to benefit farms and fish
By Kate Campbell
More than 11,000 acre-feet of excess flows from Cache Creek were diverted during late winter storms into the Yolo County Flood Control and Water Conservation District’s earthen canal system to allow it to seep into groundwater.
Yolo County farmer Blake Harlan called the effort crucial for continued farming in the area.
Chris Scheuring, CFBF environmental attorney, center, and Mary-Ann Warmerdam of Rural County Representatives of California, right, discuss Yolo County Flood Control and Water Conservation District’s groundwater recharge project with Max Stevenson, the district’s assistant manager.
Increased reliance on groundwater for crops and homes, along with new state regulations to manage the resource, are prompting creative approaches to ensure groundwater supply reliability and improve environmental conditions in the future.
The Yolo County Flood Control and Water Conservation District explained to state officials, local agencies and farmers last week how their new strategy for recharging aquifers will help stabilize local surface water and groundwater supplies. Their efforts are part of a statewide emphasis on maintaining adequate groundwater levels as required by the 2014 Groundwater Management Act.
This spring the district released about 11,000 acre-feet of excess storm flows from Cache Creek into its 160-mile-long canal system. The unlined irrigation canals—typically empty during the winter and early spring—allowed the retained water to seep into the aquifer for later use.
It's an approach to maintaining groundwater levels and storing above-normal flows that otherwise would be wasted, said district manager Tim O'Halloran, who added the additional stored water "increases the size of the groundwater pie."
"This has been an amazing project," said Yolo County farmer Bruce Rominger, who is chairman of the district's board of directors. "This is a great model that can be used throughout the state and we need to look at how this approach can be adapted elsewhere."
Rominger said he relies on the district's canals for irrigation water and is aware that without stable groundwater supplies farmers are at risk because of uncertainties related to surface water deliveries due to drought, environmental restrictions and growing demand.
In many areas increased water efficiency and water quality requirements are having unintended consequences on groundwater.
"I'm being told not to allow water to go down beyond the root zone of my tomato crop because of the possibility of leaching of nitrates," he said. "We're using micro emitters and drip irrigation to prevent leaching, but in past decades flood irrigation put water back into the aquifers. We're in a different world now."
State officials said that after a couple of months of study last winter, the district's proposal for storing excess storm flows was accepted and received temporary permits from the State Water Resources Control Board in just three days and in time to capture water from an approaching storm.
With permits in hand, the district captured a fraction of the excess creek flows, but they say it's an important amount of recharge and proves the benefit of the approach.
"Our water supplies are delicately balanced because our surface water isn't perfectly reliable," said Blake Harlan, who farms in Yolo County. "We've got a 10 percent chance in any given year that we'll have no surface water whatsoever. When that happens we have to go to groundwater. It's how we stay in business."
Maintaining balanced, reliable water supplies is important to the future of farming, he said, underscoring the value of collaboration with farmers, the district, government agencies and stakeholders, including Farm Bureau experts at the county and state levels who pushed for the demonstration project.
David Guy of the Northern California Water Association said the approach used in Yolo County demonstrates what it takes to creatively move toward groundwater sustainability, which is mandated by state law.
Farther north in Siskiyou County, farmers intentionally flooded fields during storm events in January and February with excess flows in the Scott River. They did it to replenish groundwater and improve river flows in the summer to help fish and wildlife by maintaining surface-ground water connectivity.
Through a fast-tracked temporary groundwater-storage permit from the state water board, the Scott Valley Irrigation District was allowed to divert up to 5,400 acre-feet of water during high river flows through the end of March.
CFBF Associate Counsel Jack Rice said Gov. Brown's executive order last November that encouraged accelerated groundwater recharge smoothed the way for speedier permitting of recharge projects.
"We thought the Scott Valley project looked promising, and so Farm Bureau worked closely with the irrigation district and the other partners to help make it happen," Rice said. "Both the irrigation district and the staff of the water board put in a remarkable effort to have the temporary permit approved quickly."
The strategy involves capturing water when stream flows are high and then apply it on dormant or fallow agricultural fields away from the river, so that the water will infiltrate and slowly percolate through the aquifer back to the river, said Helen Dahlke, a hydrology expert and professor with the University of California, Davis, Department of Land, Air and Water Resources.
"In months when we don't have stream flow from rainfall anymore, we hope to get groundwater flow coming into the river, and that hopefully is enough to keep the river connected so that fishes can migrate," she said.
The Scott Valley Irrigation District used its canal system to deliver irrigation water to farms to spread water onto as many as 3,500 acres of farmland within its service area for infiltration.
Though this type of practice is new for the Scott Valley, Dahlke noted previous research done several years ago in Fresno County with farmer Don Cameron on his Terranova Ranch involved diverting water from the Kings River onto alfalfa, fallow fields, row crops, orchards and vineyards to reduce downstream flood risks and replenish groundwater.
Though results of that study looked promising, Dahlke said, interest for on-farm flooding to recharge groundwater had not yet caught on.
"Now with the drought being so severe, we have more and more farmers interested in the idea," she said.
Dahlke and her research team have expanded their focus to almond and pistachio orchards in the San Joaquin Valley. There's greater risk working with permanent crops such as almonds, she said, noting that trees are harder to understand because they are slower to respond to environmental factors, and effects of stress may not show up until two or three years later. It will take multiple years of intensive study for researchers to get the full story, she added.
Identifying suitable locations and cropping systems and then figuring out how to connect those locations using existing irrigation ditches and canals to reservoirs that are releasing water in the winter are key to improving surface-water management in the long term, Dahlke said.
"It is important to understand that it is not surface versus subsurface reservoir storage, but integrated management of both," she said, emphasizing surface and subsurface reservoirs should be used together to manage water supply variability.
In some ways, groundwater recharge strategies are "akin to managing checking and savings accounts: Surface reservoirs act as a checking account for deposits and withdrawals; groundwater storage is the savings account built over time and tapped when surface supplies run low," said Danny Merkley, CFBF water resources director.
"Farm Bureau has long maintained that California must continue to pursue an all-of-the-above approach for making our state's water supplies more secure, including storage both aboveground and underground, with continued investments in water recycling, coastal desalination and enhanced water efficiency," Merkley said. "Maintaining groundwater levels and increasing surface storage are essential to supply reliability."
(Kate Campbell is an assistant editor of Ag Alert. She may be contacted at firstname.lastname@example.org.)
Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.