Groundwater: Farmers employ methods meant to boost supply
By Kate Campbell
With the California drought placing more reliance and focus on the state's groundwater resources, California farmers and ranchers continue to test innovative techniques to managing the resource through aquifer recharge, groundwater banking and conjunctive use.
At Terra Nova Ranches in southwestern Fresno County, farm manager Don Cameron has been pioneering new approaches to capturing floodwater and diverting it to permanent crops and open land, for percolation into underground aquifers. Cameron said the ranch received a U.S. Department of Agriculture grant in 2011 to assess the impact of standing water on permanent crops.
"We actually had floodwater that year and we were able to implement the testing we needed to do," Cameron said. "We recharged more than 7,000 acre-feet that year on our farm."
In partnership with the Kings River Conservation District, excess flood flows were delivered to the ranch and applied to vineyards, a pistachio orchard and open ground that was later planted to tomatoes.
"We had water a foot and a half deep on our grapes for about five and a half months," Cameron said.
People wondered how the vines would do after being inundated for so long. The answer: Just fine, Cameron said, noting that the vines put on a good canopy and fruit yield was up slightly.
With the success of the initial test, Cameron said the project has been expanded to include four other neighboring farmers and about 16,000 acres. The state Department of Water Resources, University of California, Davis, and private consultants have been working with the farmers to evaluate the impacts and techniques for applying winter floodwater to cropland.
Everybody has their fingers crossed for sufficient flows this winter to continue research and to put more water in underground storage.
UC soil scientists recently identified at least 3.6 million acres of California cropland suitable for recharging groundwater. They say walnut orchards may be viable recharge sites, but note more needs to be learned about the potential practice to avoid risk to crops.
"On-farm flooding looks very promising," said UC Davis researcher Helen Dahlke, a hydrology expert. "We're pleasantly surprised by how quickly water tables have responded to on-farm flooding without damage to crops."
This spring, Dahlke's team flooded alfalfa at Bryan-Morris Ranch in Siskiyou County, applying more than twice the irrigation water the field normally gets in a year. The field produced more weeds than usual, she said, but otherwise the alfalfa produced normally.
Answers to basic questions, such as how much floodwater application is too much and too often, still need to be settled scientifically.
This new approach to groundwater recharge can complement ongoing techniques, said farmer Kole Upton of Chowchilla. Delivering extra surface water through unlined canals, he said, provides for water to seep into the ground in what's known as "in-lieu" recharge.
"The drought has exacerbated the groundwater issues," he said. "But if we do get some rain, we need to capture the excess flows and turn it back in a controlled manner to the land, including underground."
Upton said looking at the state's soil and water resources in an interactive manner is essential to maintain food production.
"I have some water-banking facilities," said Upton, who is president of the Chowchilla Water District. "But in our district, we try to deliver as much surface water as we can through the canals to fill up the soil profile with moisture, so more water is available to move underground.
"Most importantly, we have to have access to surface water in a timely manner," he said. "During the drought, that hasn't been happening."
While groundwater banking isn't new, UC Davis researcher Josue Medellin-Azuara said it's a more effective way to replenish underground aquifers than previously realized. There are private and public groundwater banks throughout the state, and the importance of banking is gaining wider recognition.
Another tool for conserving both groundwater and surface water is conjunctive use, which uses the two sources strategically to conserve resources.
"When we think about the large water storage projects, they were conceived in part to take pressure off groundwater," said David Orth, a water agency consultant. "Conjunctive use meant if there was an abundance of surface water, that was used. If there was excess, it went to recharge groundwater."
Orth said water management will continue to incorporate that model, along with new ideas such as the winter flooding being tested on Cameron's farm.
"I think we'll see the emergence of active water markets where people are compensated for not pumping groundwater as a conjunctive-use strategy," Orth said, "maybe balancing exchanges that allow for trading."
This approach could lead to fallowing, Orth said, but it would depend on how exchanges are handled. It also could lead to crop shifting for non-permanent crops.
"It may well mean looking at ways to manage farming differently," he said.
Specialists with Sustainable Conservation, a natural resources consulting and advocacy organization, said using flood flows to recharge aquifers may be able to offset groundwater overdrafting by as much as 20 percent in some circumstances, and could expand the state's water storage capacity.
There are many issues that will need to be sorted out before various groundwater-management strategies can be scaled up—technical, scientific, regulatory and political—but water experts agree there is a lot of new research and rethinking how California's water supplies are managed.
"There are several initiatives underway in California that may lead to a more integrated approach to water management," said Chris Scheuring, lead environmental attorney for the California Farm Bureau Federation.
Barriers to thinking more strategically about water resources and how they can work together over time, he said, include a lack of financial incentives and a regulatory structure that lacks certainty.
"Basically, we need to think of our resources like banking—and in California, we need more than one savings account," Scheuring said.
(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.