Farmland and Floodwater: A Solution to the Drought?

By: Ari LeVaux

The human food supply chain is essentially an ecological food chain that’s been modified, modernized and streamlined to our needs. Despite attempts to insulate this supply chain from the whims of the ecosystems that sustain it, acts of nature can still disrupt the best laid plans. The El Niño currently brewing over the Pacific Ocean could be a major supply chain disruptor, with the potential to wash out roads (distribution) and topsoil (production). But the rains might also provide an opportunity to alleviate a deficit in California’s groundwater, which is a much longer-term threat to the supply chain. Here’s a look at how a mix of farmers, scientists, extension agents and business and nonprofit groups are scheming to capture as much of El Niño’s rainfall as they can, and bank that water in the ground for a sunny day.

Photo Source: Ken Lund

Photo Source: Ken Lund

South of Fresno, at the base of the Sierra Nevada, channels of the Kings River disappear into the ground en route to the long-dry bed of Tulare Lake, which was once the largest freshwater lake west of the Mississippi River. The last time real water moved through the channels was in January 2012.

A local farmer named Don Cameron diverted some of that flood-stage river water onto 150 acres of grapes. Thanks to the snowpack that year, he was able to keep the grapes flooded for the better part of five months. His grapes and his harvest both turned out fine. The aquifer below his ranch, meanwhile, got a much-needed shot in the arm; Cameron believes about 75 percent of the water he diverted to his fields made it into the groundwater.

His results, and the buzz they stirred, helped germinate a movement to explore the possibilities of flooding agricultural land to absorb surface water during times of high flow.

For years, several California water districts have made use of infiltration basins, to which available surface water has been diverted for recharge purposes, with good results. Ag-land, being flat and divided, and with infrastructure sometimes already in place for bringing  floodwater to the fields, is an attractive option.

Ag-land, it turns out, has become all the more overdrawn on its groundwater bank account because of the industry-wide shift from old-style flood irrigation to drip irrigation, which is more efficient. But that efficiency means less wasted water to percolate down into the aquifer. Suddenly, here is an opportunity for agriculture to become part of the solution, rather than just the problem.

"Kings Canyon National Park - Kings River - confluence of middle and south forks" by Daniel Mayer. 

"Kings Canyon National Park - Kings River - confluence of middle and south forks" by Daniel Mayer. 

From a hydrologic perspective, flooding fallow or dormant cropland for aquifer recharge, “is straightforward engineering,” professor Charles Harvey, a groundwater hydrology expert at MIT, tells Food + City. There wouldn’t be a lot of hidden surprises, he speculates, and the fields are already leveled, irrigated and basically ready to go — as opposed to, say, the conversion of forest land.

While the 2012 El Niño was enough to get the Kings River channels flowing, the surge in water resources failed to meet agricultural needs in the long term.  But now, California now finds itself facing a potential Godzilla among El Niños, with the possibility of flooding galore, and there are many parties interested in using this precipitation to research the finer points of groundwater banking.

A team at the University of California, Davis recently identified 3.6 million acres of California farmland as potentially suitable to groundwater banking, from a geological perspective.

There would be many other legal, environmental, economic and agricultural factors to consider, such as the kinds of crops currently on the land and their ability to adapt to being submerged under water for weeks at a time. While grapes might be the current poster child for groundwater banking, other crops are being explored, like pears, wine grapes, some annual crops, and some varieties of almonds, peaches, and plums. Fallow land, or land under a cover crop works too.

“We’re pleasantly surprised by how quickly water tables have responded to on-farm flooding without damage to crops,” says Professor Helen Dahlke, who leads the UC Davis team.

Diverting winter rainfall from rivers to crop acres not only recharges the aquifer, but can mitigate downstream flooding as well, explains Phillip Bachand of the environmental engineering firm Bachand & Associates. In the San Joaquin drainage, Bachand tells Food + City, the ability to move water from dangerously bloated rivers could prevent billions in downstream damage. The biggest hurdle to flooding cropland is that many farms and water districts are currently lacking infrastructure to bring the water to the fields — or “conveyance,” in irrigation jargon. He also says there needs to be a better link between surface and groundwater storage engineering, which would, “make groundwater storage a major player in managing the water crisis.”

California’s Sustainable Groundwater Management Act, passed in 2014, specifically mandates the facilitation of groundwater banking. Increases groundwater storage and removes impediments to recharge, is among the eight core descriptors of the act.

Invoking that mandate, district water managers are writing grants galore to build and improve their conveyance capacity. In Yolo County, water conservation district general manager Tim O’Halloran recently spent $2 million of grant money to automate the gates on 16 miles of his district’s canals, and just received another $2 million for another ten miles’ worth. This will allow the district to act more nimbly when the rain is falling, he says, which is also when you least want to send a technician into the mud to yank on a manual gate.

While grant money is flowing for bureaucrats, it’s conspicuously absent for farmers, who sometimes can incur quite a financial burden in their attempts to bank groundwater. Well-funded visionaries like Don Cameron, who has spent millions of his own on groundwater banking research and efforts, are few and far between. Toby O’Geen of UC Davis tells Food + City, “farmers will need some sort of compensation to alleviate some of the risk and effort associated with this practice.”

Photo Source: Harsha K R

Photo Source: Harsha K R

Daniel Mountjoy is director of research stewardship with Sustainable Conservation, a nonprofit that is working with landowners to research and implement groundwater banking schemes on private land. Mountjoy believes that 20 percent or more of the state’s overdraft from its aquifers could be offset by the use of groundwater banking practices on suitable lands. “This is probably one of the more exciting projects we’ve had in our 20 year history,” Mountjoy says.

Mountjoy looks at the coming El Niño as a huge opportunity and plans to flood tomato, walnut, grape, almond and pistachio fields. He spoke of an almond grower who is doing his own personal flood irrigation research, with promising results, and has partnered with the Almond Board of California to investigate the feasibility of using almond acreage for aquifer recharge.

The Almond Board, meanwhile, has also financed feasibility research at UC Davis. After being so often vilified as the water table’s worst enemy, it wants to be at the forefront of groundwater banking.