First-of-its-kind groundwater project begins
By Ching Lee
Some Siskiyou County farmers will be deliberately flooding their fields in the next two months with high winter flows from the Scott River, in an effort to replenish groundwater and improve river flows in the summer to help fish and wildlife.
Through a temporary groundwater-storage permit from the State Water Resources Control Board, the Scott Valley Irrigation District will be allowed to divert up to 5,400 acre-feet of water during high flows until the end of March.
The water board said the temporary permit is the first issued for this type of water diversion and use. Working with the University of California, Davis; California Farm Bureau Federation; Scott River Water Trust and others, the district secured the permit just as heavy storms drenched the state.
CFBF Associate Counsel Jack Rice said Gov. Brown issued an executive order last November that encouraged groundwater recharge and smoothed the way for permits for 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 goal is to capture water when stream flows are high and apply it on dormant or fallow agricultural fields far 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 UC 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 added.
With heavy rainfall associated with El Niño predicted this year, state water board Chair Felicia Marcus said the project provides "an opportunity for accelerating groundwater recharge that we so critically need."
The Scott Valley Irrigation District will use its canal system that typically delivers irrigation water to farms to spread water onto as many as 3,475 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, which 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.
One was Siskiyou County rancher and hay grower Jim Morris, who volunteered a 15-acre alfalfa field last spring on which Dahlke and her team did their initial research. Alfalfa is a good candidate, she said, because of the amount of acreage dedicated to the crop in the state and because it requires little to no nitrogen fertilizer, which reduces the risk of nitrogen leaching into the subsurface.
"We found that the water-holding capacity was tremendous," Morris said. "The amount of water that we could put in was beyond anybody's expectations."
Having data from the study also helped to push the permitting process through in an expedited manner, Morris noted. He is participating in the current recharge project, again using land with alfalfa for some of the infiltration sites.
But unlike other, similar projects that divert excess surface water to fields and infiltration basins for the purpose of groundwater banking, Morris said the intent of the Scott Valley project is not to recharge groundwater for irrigation. Rather, it's to enhance instream flows for fish and wildlife, which he said is a benefit to agriculture in the long term. By improving summer flows using winter high water and thereby helping the fish, Morris added, that "hopefully helps to decrease the size of the target on our backs."
"We will not pump any less or any more because of this project," he said.
With the infrastructure already in place to divert the water, Morris said "there's really not a good reason not to do" the project, although he noted there will be a management cost to the district. And there are still many unknowns about how alfalfa and other crops will react to being underwater for extended periods, though applying water during winter dormancy appears to have had little impact on his alfalfa stands last year, he noted.
Dahlke noted that while the crop showed some yellowing after six weeks, the plants bounced back after water was turned off, with no appreciable reductions in yield.
Dahlke and her team have expanded their research into 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.
With the state's groundwater management law, passed by the Legislature in 2014, Dahlke said local agencies will be looking for ways to achieve long-term groundwater sustainability. Relying just on natural recharge from rainfall and snowmelt is likely not the only answer, with variable climate expected in the decades to come, she said. Agriculture's reliance on surface-water supplies during the summer also will be more uncertain, with less water being stored as snowpack and more of it flowing downhill that reservoirs will not be able to store, she added.
"This water is really something that we want to capture with groundwater recharge," she said. "But it needs a little bit of planning because recharge is really not a fast process."
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.
While the use of on-farm flooding as a recharge strategy is still new with a lot of unknowns, Morris said he thinks it will be "a tool that will be used regularly to benefit groundwater."
"There are opportunities through this kind of a project to build relationships with other users of resources in the area and with agencies," he said. "I think these are the kind of win-win opportunities that we have out there and we need to take advantage of them every chance we get."
(Ching Lee 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.