In drought-wracked California, some towns are looking to the sea for a solution to their water woes.

But turning salty seawater into something drinkable is a costly process that's not likely to help break the long dry spell by itself.

"There's a saying — and it might be true — that ocean water desalinization is a promising solution, and possibly always will be," Jay Lund, the director of the Center for Watershed Sciences at the University of California-Davis said.

"You can go back to the 1950s and 1960s, and politicians and some technologists were saying that in the next decade, breakthroughs in seawater desalination are going to make water so cheap we won't bother metering it," Lund said. "The cost of desalination has gone down quite a lot. But at least in California, they would have to come down another 50 percent or so before they're really competitive."

Workers are rushing to complete a $1 billion desalination plant outside San Diego, a project that's expected to produce up to 50 million gallons of drinkable water a day after it goes online in October. The San Diego County Water Authority has a 30-year contract to buy water from the plant, which is expected to provide about 7 percent of the area's demand.

At least two other seawater desalination plants are being planned along the coast. And in Santa Barbara, the city is reactivating a $34 million facility that it built during a drought in the early 1990s — only to put it into mothballs when the drought eased.

Desalination works by pumping water at high pressure though a series of filters — a process known as reverse osmosis. The process yields a gallon of fresh water for every two gallons of seawater used, according to Poseidon Water, which is building the plant.

The company did not respond to questions from VICE News.

The state has provided about $40 million over the past decade to local governments that want to build a desalination plant, with the money supporting planning, research, and construction efforts, Doug Carlson, an information officer for the California Department of Water Resources, said. But that the economics of desalination are more complicated for bigger communities.

"Smaller communities may find it advantageous to fill in some blanks that they may have in their own water resources," Carlson said. But right now, "It's not economic to build massive plants that would take care of millions and millions of people's needs," he said.

Desalination has been used successfully and fairly economically in taking the salt out of brackish groundwater. But seawater has 10 times the salt content of brackish water, and desalination consumes a significant amount of power — about 5 kilowatt-hours to desalinate a cubic meter (264 gallons) of water, Lund said. As a result, it ends up costing about twice as much as ordinary water.

"You've got to be pretty desperate to pay those costs," Lund said. The most successful projects have been in Israel and in the Persian Gulf states: "They have much less agriculture and they don't have any lawns," he said. The oil-rich Arab monarchies in particular "have lots of cheap energy, and no other supplies of water."

But California is home to a $43 billion agriculture industry that provides about half of America's fruits and vegetables. As much as 80 percent of the state's water consumption goes to farms far inland, and desalination plants won't have much effect on that, said Heather Cooley, the water program director at the Pacific Institute, an Oakland-based environmental think tank.

"I think agriculture does think that by providing another source to urban areas, it would reduce pressure on them to reduce their water use," Cooley told said. "But no one's talking about using it directly for agriculture."

Desalination also leaves behind a concentrated brine that has to be pumped offshore or injected underground. Environmentalists warn that sucking in huge quantities of seawater and expelling much-saltier water will kill marine life, and that the power used releases more planet-warming carbon emissions. Poseidon says it will restore nearby trees and wetlands as part of the project and has a plan to eliminate its carbon footprint through energy efficiency, capturing carbon dioxide, and planting new trees.

But for most communities, simpler solutions like conservation and recapturing stormwater runoff are cheaper and pose fewer environmental problems, Cooley said.

"It's effective in some regions where there's a need," she said. "But we need to fully recognize what the opportunities are, what the relative costs and environmental impacts are, and do the most cost-effective things first."

Watch the VICE News documentary Flooded Fields in California's Drought here: