California’s Farmers Need Water. Is Desalination the Answer?

President Obama will get to see California’s disastrous drought first hand today on a visit to the farming city of Fresno. It won’t be a pretty sight. While the conditions are arid across the state, with 91.6% of California in severe to exceptional drought, agricultural areas are suffering the worst.

The state’s Central Valley has long been the fruit and vegetable basket of the country, growing nearly half of U.S. produce. But farms in the valley exist only thanks to irrigation—the Central Valley alone takes up one-sixth of the irrigated land in the nation. And thanks to the drought, there’s been little rain, and irrigation has been virtually cut off. California officials have already said that they won’t be able to offer any water to farmers through the state’s canals, and the expectation is that federal reservoirs won’t be of any help either, leaving farmers to their own dwindling supplies of groundwater. The California Farm Water Coalition estimates that the drought could translate to a loss of $11 billion in annual state revenue from agriculture.

Obama will try to offer some help in his visit to Fresno, announcing that the federal government will make available up to $100 million in aid for California farmers who’ve lost livestock to the drought, as well as $15 million in aid to help farmers and ranchers implement water conservation policies. But while efficiency and conservation can go a long way to stretching dwindling supplies of water, the reality is that California is an arid state that consumes water—80% of which goes to agriculture—as if it were a wetland. If it wants to continue as the nation’s number one farming state—producing a record $44.7 billion in agriculture receipts last year—it’s going to need more water. And if scientists are right that the current drought is the worst California has faced in 500 years, and that the state could be on the brink of a prolonged dry period accentuated by climate change, that water is going to have to come from new sources.

(MORE: Hundred Years of Dry: How California’s Drought Could Get Much, Much Worse)

As it happens, California sits next to the biggest source of water in the world: the Pacific Ocean. The problem, of course, is that seawater is far too salty to drink or use for irrigation. Desalination plants can get around that, using large amounts of electricity to force seawater through a membrane filter, which removes the salt and other impurities, producing fresh water. There are already half a dozen desalination plants in California, and around 300 in the U.S., but the technology has been held back by cost and by environmental concerns. A $1 billion desalination plant capable of producing 50 million gallons of water a day is being built in the California town of Carlsbad, but San Diego will be buying water from the facility for about $2,000 per acre-foot, twice as much as the city generally pays for imported water, while producing enough water for 112,000 households. Desalination can have a major carbon footprint—the Carlsbad plant will use about 5,000 kilowatt hours of electricity to produce an acre-foot of water. And because desalination plants in general needs about 2 gallons of seawater to produce a gallon of fresh water, there’s a lot of highly salty brine left over, which has to be disposed of in the ocean, where it can pose a threat to marine life.

Still, while efficiency and conservation will always be lower cost and lower impacts solutions to any water crisis, it’s hard not to see desalination playing a bigger and bigger role in California’s efforts to deal with lingering drought. The process of desalination is improving—the Carlsbad plant uses reverse osmosis technology, which is more energy efficient and environmentally friendly than older methods —and it has the advantage of being completely drought-proof. In a world where water is more valuable and more valued, desalination can begin to make more sense.

“Desalination needs to be judged fairly against the other alternatives,” says Avshalom Felber, the CEO of IDE Technologies, an Israeli company that is helping to construct the Carlsbad plant.

(MORE: Can GM Crops Bust the Drought?)

If desalination could be powered by renewable energy, some of those environmental concerns would melt away. And that’s what a startup called WaterFX is trying to do in the parched Central Valley. While farmers in the valley generally depend on irrigated water brought in from hundreds of miles away, the land itself isn’t short of groundwater. But most of that water is far too salty for use in farming. WaterFX’s technology uses a solar thermal trough—curved mirrors that concentrate the power of the sun—to evaporate salty water. The condensate that’s later collected and cooled becomes freshwater, leaving salt and other impurities behind. “Solar stills are an old technology, but this has a new twist that makes it very efficient and very cost effective,” says Aaron Mandell, the CEO of WaterFX.

Because it uses solar power, WaterFX’s desalination has virtually no carbon footprint, and the company says that it has a 93% recovery rate, much higher than conventional desalination. But its biggest advantage might be its modularity—Water FX’s solar stills can be set up locally, allowing farms to recycle their own runoff, rather than having freshwater pumped in from afar. That saves energy and money. “You can create a closed loop where the water is reused over and over again,” says Mandell.

Right now the company is working on a pilot with the Panoche Water District in the Central Valley, producing almost 500 gallons of clean water a day. WaterFX has plans to expand to a commercial plant with a 2 million gallon capacity. Of course, the technology would have to be scaled up massively to even make a dent in California’s irrigation needs, given that the state sends billions and billions of gallons of water to farms each year. But if California really is on the edge of a great dry, every drop will help.

(MORE: Why the Drought Won’t Be Getting Better Anytime Soon — and Why This One Won’t Be the Last)