Water is scarce in California. But farmers have found ways to store it underground


Aaron Fukuda admits the 15-acre sunken field behind his desk doesn’t look like much.

It’s basically a big, wide hole in the ground behind the headquarters of the Tulare Irrigation District in the southern part of fertile California. Central valley. But “for a water resources nerd like me, this is sexy and sexy infrastructure,” says Fukuda, the district general manager.

This earthen basin could be the key to the survival of a farming community that delivers huge amounts of vegetables, fruits and nuts to the rest of the country – but is short some water. The basin only needs the Californian rivers to rise and flood it.

When the rains come in winter and swell the rivers, Fukuda and his colleagues open floodgates and send water through the irrigation canals to fill this basin and many others they have established. This captured water will seep into the ground and eventually make its way to a natural aquifer system hundreds of feet below.

Groundwater has become a rare and the regulated assets of the State. Farmers have pumped so much water from aquifers in this part of California that they have depleted, threatening water supplies for agriculture and communities that depend on wells for their household water. A 7-year-old law, which has just come into force, strictly limits the amount that farmers can pump from these aquifers, and those limits could bankrupt some farmers.

Water catchments like this one, however, offer farmers a way to survive. It is because the new law treats the underground aquifer like a bank account. If farmers add water to this account when water is plentiful, they can extract more when needed, during drought years. “It’s really the difference between our community surviving and not,” says Fukuda.

Floods go from nuisance to lifeline

In the past, many Californians viewed winter flooding as a nuisance, Fukuda says. Now that has now completely changed. “It’s liquid gold,” he said. “Cold, crisp floodwaters are gold these days.”

Farmers and water managers in the southern part of the Central Valley, where the water problem is more severe, seize the idea of ​​the water reserve as a lifeline. Jon Reiter, breeder and water consultant, works with some of them.

He shows me a field of grapes, destined to become raisins. The ground is sandy and seems to be able to soak up all the water that has landed here. There is already an embankment around three sides of the land. “You can imagine how much water you could store in the ground in a place like this,” says Reiter.

The owner of this field, he says, “decided he would be ready to take out the raisins” and use the land instead to catch the water. The water he “sinks” may be more valuable to him than his harvest of raisins, as it may earn him the right to pump more water from the aquifer during a future drought to irrigate other fields. .

Don Cameron, the owner of Ranch Terranova near Helm, Calif., has even bigger ambitions. Cameron’s farm relies almost entirely on groundwater. He has watched the falling groundwater level for years and worries about the future.

Ten years ago, during a winter with a lot of rain, he decided to flood some vineyards and orchards, to see if he could replenish the aquifer without even clearing land for a dedicated “recharge basin” . “A lot of people were skeptical, our neighbors in particular,” Cameron says. “I mean, they thought we were crazy. That we were going to kill our vineyard.”

In fact, the vines and trees survived very well and the experience increased the groundwater levels under his field. Other experiments, some carried out in collaboration with researchers at the University of California at Davis, have confirmed the feasibility of this “on-farm recharge”. Now Cameron is persuading his neighbors to do the same. Together, they could potentially flood tens of thousands of acres.

This is only possible, however, because Cameron is in a privileged location, right next to an arm of the Kings River, which in turn is connected to a grand canal which is a major artery of the vast system of California water supply. This canal is dry at the moment, but in years of heavy rain it can fill with water. Many other farmers who depend on groundwater, and who will be hardest hit by the new law restricting its use, cannot make “deposits” to their underground bank account because they do not have access to floodwater. They are not connected to the network of ditches and canals that would be necessary to carry flood water to their fields.

All Cameron needs is Mother Nature to deliver a flood. “I know we’ll have another one,” he said. “There is no doubt in my mind that we are going to flood again. We may even see more severe flooding in the future.”

Climate experts agree this is likely. In the past, California relied on precipitation arriving as snow in the Sierra Nevada Mountains. The high altitude snowpack acted like a giant reservoir, slowly releasing water into rivers as it melted. In the future, more of this water will arrive as rain, quickly flooding rivers. The largest reservoir available to store it could be underground, in the aquifer that Californian farmers have drained for most of the last century.

Will this solution fail?

This won’t solve all of the Central Valley’s water problems, however. On the one hand, there will still not be enough water available to fully recharge the aquifers. According to Reiter, the aggressive capture and storage of flood water could at best offset 40 to 50 percent of the current groundwater deficit.

In addition, aquifer recharge could have mixed effects on the other big problem of groundwater in the central valley: contamination of wells with agricultural chemicals. These include nitrates from fertilizers and livestock wastes. The problem is most serious for low-income communities who depend on shallow wells for household water use.

Flooding more land will likely result in the release of these agricultural pollutants into aquifers, according to Helene dahlke, hydrologist at the University of California, Davis. “We often see a nitrate spike, for example, in the water table below a recharge site,” she says.

In the long run, however, she believes it will be good for the water quality. “Most of the water we use to recharge is very clean, because it comes from precipitation or snowmelt in the Sierra Nevada mountains,” she says. “Ultimately, there will also be a pulse of clean water entering the aquifer as well, which can dilute many pollutants that have moved into groundwater over the past two decades.”

She recalls the experience of a small community in Tulare County called Okieville. There are parts of the community where the wells show high levels of contamination. But along its southern edge, there is a groundwater recharge basin that the Tulare Irrigation District regularly fills with floodwater. People who live near this basin have benefited from a reliable supply of clean water from their wells.

The Irrigation District is now considering building a new recharge basin on the other side of Okieville. “The idea is that we can start pouring water under their community. Quality, clean water, ”explains Aaron Fukuda, general manager of the irrigation district. “The quality of the water, we hope, is improving.”

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