Extreme drought conditions in California have state officials looking for alternative sources of water, including desalinated ocean water. Richard Vogel/AP

National Public Radio in the USA has this story, both podcast and text version, about efforts to provide drinking water to a dry, thirsty region:

California is getting some much needed rain this week, but more than two-thirds of the state is still in extreme drought conditions, and that has the state thinking about alternative ways of getting water.

On the coast in Carlsbad, Calif., construction workers are building what will be the largest seawater desalination plant in the Western Hemisphere. When finished in early 2016, it is expected to provide up to 50 million gallons of fresh drinkable water every day.

“That’s enough water for 112,000 households here in the region,” says Peter MacLaggan with Poseidon Resources, the developer of this $1 billion plant.

The process, MacLaggan explains, involves taking water from the Pacific Ocean, removing the silt, sand and “organics,” then pressurizing the water through very fine membranes. The technical name is reverse osmosis. And the result? “Every 2 gallons of seawater that goes in, 1 gallon of high-quality drinking water comes out,” he says.

And MacLaggan says the best part is it’s droughtproof.

“It’s droughtproof because it’s not dependent on snowpack in the Sierras, it’s not dependent on rainfall here in San Diego,” he says. “You’re getting water from the Pacific Ocean.”

The word “droughtproof” carries a lot of weight in California. That snowpack in the Sierra Nevada he’s talking about is still less than half of what it should be for this time of year. Farmers, environmentalists and cities like nearby San Diego have been fighting over what little water there is.

“San Diego currently imports about 70 percent of its water,” says Bob Yamada, the water resources manager at the San Diego County Water Authority.

Yamada says that’s why the authority has agreed to buy water from the Carlsbad plant when it’s finished — even though it costs twice as much as the water imported from Northern California and the Colorado River.

It’s expensive “but it does provide you with the highest reliability,” Yamada says. And he says people are willing to pay more for reliability. He also thinks that the difference in price between imported water and desalinated will shrink as more and more people vie for less and less water from rainfall and snowpack.

Desalination costs more because it takes a lot of energy to suck 100 million gallons of ocean water into a plant and pressurize it through little tubes. And that’s where the opposition comes in.

“Well, on a macro level, we just think that there are less expensive, less environmentally damaging ways to increase our water supply,” says Rick Wilson with Surfrider Foundation. The nonprofit environmental group opposes the Carlsbad project.

One reason, Wilson says, is that all of that energy use will contribute to global warming. More directly, he says, the intake pipe for the plant will suck in sea life, killing marine animals.

“And there’s also the concern in some cases about the discharge from these plants,” he says. Discharge is the extra salty leftover water that’s pumped back into the ocean.

Those concerns have stalled plans for another desalination site farther up the coast, in Huntington Beach. Carlsbad though, has met all of the state’s requirements. Still, Wilson says, money would be better spent on conservation and water recycling efforts…

Read the whole story here.