FutureStructure

Harnessing El Niño: California Farmers Flood Fields

Although the comparatively small flood projects popping up around the San Joaquin Valley won’t cure California’s drought, farmers are hoping to recoup some of their losses.

by Dale Kasler, The Sacramento Bee / January 21, 2016
Farmers in California are forced to come up with new ways of growing crops in the drought-plagued state. Flickr/U.S Department of Agriculture

(TNS) -- The water bubbled and gurgled for a few seconds, and then poured out in a rush. Within minutes, a five-acre plot on Nick Blom’s almond orchard was under a half foot of water Tuesday. Scientists from UC Davis stood by in the rain, checking underground gauges installed to make sure the standing water wouldn’t ruin his trees.

“It’s a risk, but it’s a calculated risk,” Blom said as floodwaters from a nearby canal gushed out of the irrigation pipe. “We’re helping the groundwater.”

Blom is among a group of California farmers volunteering in an experimental attempt to harvest the fruits of El Niño. Instead of letting winter stormwater run off their fields and flow to the ocean, as is typical, they’ve agreed to deliberately flood their orchards and vineyards for days at a time. The idea is to let the water slowly percolate into the ground to help recharge California’s overtaxed aquifers.

By themselves, the comparatively small flood projects popping up around the San Joaquin Valley won’t cure California’s drought, now in its fifth year. Much of the rain falling on rural California will wind up in the ocean. While that will improve the health of the Sacramento-San Joaquin Delta, the troubled estuary that serves as the hub of the state’s water system, it won’t provide the kind of drought relief Californians are craving.

“There will still be a lot of water that goes to the sea,” said Jeffrey Mount, a water expert at the Public Policy Institute of California.

Nevertheless, the flood experiments could point the way toward at least a partial remedy for one of California’s most difficult and persistent water problems: the long-term depletion of the state’s aquifers.

Farmers and others were extracting as much as 2 million acre-feet a year from beneath the San Joaquin Valley even before the drought began, according to Department of Water Resources data. That pumping shifted into overdrive when the drought dried up deliveries of water from the state’s reservoirs and canals, draining the aquifers by an estimated 5 million acre-feet a year. Relentless pumping has caused parts of the valley floor to sink, a phenomenon known as subsidence.

California’s Sustainable Groundwater Management Act, signed into law in 2014, adds urgency to the quest to replenish the state’s groundwater. The law, which takes effect in 2020, requires local agencies to manage their aquifers more responsibly in the decades to come.

In the meantime, some farmers and water districts have moved ahead with projects designed to store winter rains beneath the soil.

With financial help from the state, the Fresno Irrigation District has invested millions in the past decade on a group of stormwater-capture basins to recharge the region’s aquifers. The basins essentially consist of 8-foot-high earthern berms that hold in the water, diverted from district canals, until the water trickles into the soil. Gary Serrato, the general manager, said the district can deposit at least 40,000 acre-feet of El Niño water into the ground this winter.

“If we can put water in, build up our groundwater aquifer, it’s like a bank,” Serrato said. “It’s in these wet years when we’ve got to (make) the efforts that we’re doing right now.” An acre-foot is 326,000 gallons.

The recharge movement has spread to other pockets of the valley. The Tulare Irrigation District, thanks to a grant from the U.S. Bureau of Reclamation, is building a groundwater storage project on 80 acres near the city of Tulare. In the Fresno County community of Helm, a farmer named Don Cameron is working with neighbors on a plan to flood 6,000 acres in a project funded with $5 million in state grants. Cameron’s project, like the Tulare program, won’t be ready this winter.

“We felt responsible for trying to rebuild our underground aquifer here,” said Cameron, who flooded 600 acres of vineyards and pistachio orchards in an experiment during the last wet winter, in 2011. “We realized that it’s a problem.”

Flooding farm fields is a promising but largely overlooked method of replenish the valley’s aquifers. Mount said the projects under way are worthwhile but won’t go nearly far enough in correcting the aquifer depletion that’s been occurring for years.

“These projects aren’t going to come close to restoring that,” Mount said. “The water balance problem is immense. This is not going to solve the problem, but it’s going to help.”

Organizers said the recharge movement could expand. Helen Dahlke, a UC Davis hydrologist working on the flooding of Blom’s orchard, said university soil surveys revealed that as many as 5.6 acres of California farmland could be flooded to replenish aquifers.

“We are hoping to figure out how we can use the vast acreage of agriculture fields in California to do designated artificial groundwater recharge,” she said.

The technology is relatively simple. Blom’s almond orchard, a few miles west of Modesto, is served by a canal maintained by the Modesto Irrigation District. In a typical winter, rainwater would pour through the canal en route to the Tuolumne River and ultimately the Pacific Ocean. On Tuesday, for the third time this winter, Blom opened up one of his irrigation pipes, and water from the canal started filling one five-acre stand of almond trees.

Gravity did the rest. By mid-day Wednesday, much of the water had seeped into the soil, beginning the process of replenishing the aquifer below.

Blom, who farms a total of 1,300 acres, is one of three valley farmers participating in a series of small tests coordinated by UC Davis, San Francisco nonprofit Sustainable Conservation and the Almond Board of California. The almond board is providing $210,000 to fund the three projects.

“We’re going to start conservatively,” Dahlke said.

The reason for the caution is that flooding orchards can cause problems for trees.

The water that gushed onto Blom’s orchard last week created a temporary lake that didn’t seep into the ground for two days. The possibility of disease and other problems loomed large.

Ken Shackel, a UC Davis plant scientist working on the project, said researchers believe almond trees can take flooding in December and January –but no later than that.

“December and January are the window,” he said. “We know you can kill almond trees if you flood them in spring and summer.”

Shackel said cameras have been planted underground on Blom’s farm to monitor the roots and make sure the trees stay healthy. When the harvest comes in, yields will be compared with previous years to make sure the trees’ productivity hasn’t been compromised.

Blom’s experiment won’t contribute much to the state’s overall water supply; a total of 10 acre-feet of water will be planted in the ground if all goes according to plan. Nonetheless, Blom said every bit helps.

Last summer, the Modesto Irrigation District, which is served by the Don Pedro reservoir, sent Blom less than half the water he needed to produce his almond crop. The rest of his water came from groundwater pumping. While the aquifer around Modesto isn’t nearly as depleted as some in the valley, Blom believes the underground reservoir needs to be kept as full as possible.

“If we can recharge that and make it better, it’s just a plus for everybody,” Blom said. “If, through their research, we find out we’re not hurting my trees, so much the better.”

©2016 The Sacramento Bee (Sacramento, Calif.) Distributed by Tribune Content Agency, LLC.