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The snow pack in the Mountain West is down, way down from previous years. 2013 was the driest year ever recorded in many parts of California. And there is little relief in sight.

From member station KQED, Lauren Sommer reports that water managers are trying to squeeze every last raindrop out of Mother Nature with an old technology: cloud seeding.

LAUREN SOMMER, BYLINE: Droughts tend to produce a lot of wishful thinking and Jeff Tilley says, as a cloud-seeder, it definitely comes his direction.

JEFF TILLEY DESERT RESEARCH INSTITUTE PROFESSOR: There's only so much we can do. If we could make the clouds appear out of thin air we would, but we can't do that yet.

SOMMER: Tilley runs the cloud seeding program at the Desert Research Institute in Reno, Nevada. And he says weather modification, as it's called, is about making rain, not making clouds.


SOMMER: It happens at the summit of the Alpine Meadows Ski Area, north of Lake Tahoe, right where the chairlift drops off.


SOMMER: Most skiers don't notice the large metal bunker with a chimney on top.


SOMMER: So it's going?

PROFESSOR: It's going.

SOMMER: This isn't a snow-making machine, like the ones ski areas are relying on this winter. The chimney is releasing tiny particles of silver iodide. These are the seeds in cloud seeding, rising thousands of feet up into the air. How do they work? Well, clouds are made of millions of tiny water droplets, but those drops don't automatically fall as rain or snow.

PROFESSOR: Water needs some sort of substance to condense upon.

SOMMER: It needs something to stick to, tiny particles like dust. If a cloud doesn't have enough dust, Tilley says...

PROFESSOR: You have these very static, dead clouds that don't precipitate, don't produce any water and just keep moving right through.

SOMMER: That's where the silver iodide comes in. Tilley says it's the right shape and size to help snowflakes form. Cloud seeding only works in certain conditions - you have to have clouds, of course - and it has to be colder than 20 degrees. But over a season, Tilley says it can make a difference.

PROFESSOR: What we find is a range of anywhere between eight and 15 percent increase in water.

SOMMER: The silver iodide ends up in the local environment where some worry it's a contaminant, though Tilley says tests show only trace amounts. Cloud seeding in California started more than 50 years ago. Though back then, it was a closer to magical thinking, an idea Tilley says has stuck around.

PROFESSOR: We get voodoo. We get, you know, Dr. Frankenstein. We get all sorts of things. But we've been able to refine the technology.

PETER GLEICK: For a long time there's been hope that we could somehow figure out a way to squeeze more water out of nature.

SOMMER: Peter Gleick is president of The Pacific Institute, a water policy think tank. He says it's hard to verify exactly how much water cloud-seeding produces, and if it's worth the money. A review by the National Academy of Sciences, in 2003, found that more research needs to be done to prove its effectiveness.

GLEICK: But even more importantly, it's limited no matter what. We get a certain number of clouds with moisture in them. If we can wring a little more out of those clouds, that's sort of the idea behind cloud seeding. But we're not going to wring a lot more out of those clouds. And so it's not a silver bullet. There is no silver bullet for California's water problems.

SOMMER: Across the state, water agencies spend three to $5 million a year on seeding, which is estimated to boost runoff by about four percent. That might not sound like much, but as water resources get tighter, cloud seeder Jeff Tilley says his field is getting a second wind. Nine other Western states also use seeding, including Colorado, Texas and Utah, where it's commonly done with airplanes.

PROFESSOR: I think for the entire inner Mountain West, it's becoming more important. It's not going to be the whole answer but it can be one tool in the toolkit. And it's a cost-effective one.

SOMMER: Tilley says cloud seeders are looking to cut costs further by using drones instead of planes. The demand is on the rise, he says, as the West relies more than ever on every last raindrop.

For NPR News, I'm Lauren Sommer in San Francisco.



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