At the Terranova Ranch near Fresno, California, general manager Don Cameron examines grapes in a vineyard that workers flooded last spring.

Winter rains had ended a severe drought and he was engaged in “groundwater recharge,” returning unused water from the North Fork of the Kings River to an underground aquifer, the source of irrigation for this region. Some were skeptical because he was flooding a working vineyard and not a special basin designed for the purpose.

“We’ve been through a five-year drought,” Cameron explained. “Our groundwater has been depleted during that period, and long term, we want to rebuild what we’ve lost.”

Recharging groundwater on fields that are in production was a test, and the vines were closely monitored. They held up well to the thousands of cubic meters of water that flooded the fields and percolated down to nature’s underground storage system.

A research team led by hydrologist Helen Dahlke at the University of California, Davis, wants to test this concept throughout the Central Valley.

California produce

The 50,000-square-kilometer swath of California farmland produces one-quarter of the food for Americans, and 40 percent of their fruits, nuts and vegetables.

The Terranova Farm grows 25 crops, from tomatoes to onions, and Cameron wants to see how other crops respond to the winter flooding. He is expanding the farm’s recharge project with help from a $5 million grant from the California state government, and envisions recharge efforts at farms around the state.

Aquifers are like a banking system, says Graham Fogg, a UC Davis geologist and water expert who says depleted aquifers have three times the available storage capacity of surface reservoirs. “If you’re looking for places to store water, it’s a no-brainer,” he said.

The idea of groundwater banking took root in the 1990s, when water authorities such as the Semitropic Water Storage District near Bakersfield, California, created exchange systems to credit farmers for surplus water returned to canals and reservoirs when it is not needed.

Farmers later use that water instead of pumping water from the ground. The district also floods recharge basins to let the water seep down to replenish the aquifer.

Surface and groundwater are parts of the same system, says district general manager Jason Gianquinto, “so we can take advantage of the wet years and put a lot of water in storage and then fall back on the groundwater in the dry years.”

Groundwater measures

In 2014, California legislators imposed restrictions on pumping groundwater and gave local authorities until 2020 to implement measurements and controls.

The law aims to stop aquifer depletion within two decades and create a record of groundwater use, something already seen in many other Western states.  

Hydrologist Fogg says intervention was needed because Central Valley aquifers have been dramatically lowered in places, which has led to subsidence or sinking of the ground that could potentially lead to the collapse of some aquifers. He notes that aquifer depletion is also a problem in many developing nations, including China and India.

Issues surrounding water in California are politically charged and pit residents of the north against those of the south, cities against farmers, and environmentalists against agricultural interests.

Regulations to regulate the pumping of groundwater are being drawn up by local agencies, and it needs to be done right, says farm manager Cameron, or “you’re going to have fewer jobs. It’s a ripple effect through the economy.”

He says that farmers could face a stark choice of pumping less groundwater or growing fewer crops.

Whatever happens, Cameron says, “it’s going to be a real game-changer for this area when we get to 2020,” when the groundwater management system is in place.
…