The Science of Sustainability

In Dry Year, California Looks to Cloud Seeding

  • share this article
  • Facebook
  • Email
Cloud seeding tower at the summit of Alpine Meadows ski area near Lake Tahoe, California. (Lauren Sommer/KQED)

Cloud seeding tower at the summit of Alpine Meadows ski area near Lake Tahoe, California. (Lauren Sommer/KQED)

California’s snowpack is just 20 percent of normal for this time of year, according to snow survey results released on Friday. That’s not surprising after 2013 ended as the driest year ever recorded in many parts of the state, but it’s fueling concerns about California’s water supply.

With rationing looking likely, water managers are hoping to squeeze every last drop out of Mother Nature with cloud seeding. The decades-old technology is designed to wring extra moisture out of storm systems, though the storms have to appear in the first place.

“There’s only so much we can do,” says Jeff Tilley, who runs the cloud seeding program at the Desert Research Institute in Reno, Nevada. “If we could make the clouds appear out of the thin air, we would, but we can’t do that yet.”

This time of year, Tilley and his team are scouring weather imagery, waiting for the right conditions to turn on five ground-based cloud seeding towers. One sits at the summit of the Alpine Meadows Ski Resort, north of Lake Tahoe, right where the chairlift drops off.

The large metal bunker with a chimney on top goes mostly unnoticed by skiers zipping by. It’s not a snow-making machine, like those the ski areas are relying on this winter. The chimney releases tiny particles of silver iodide – the seeds that rise thousands of feet into the clouds.

“Water needs some sort of substance to condense upon,” says Tilley. Clouds are made of millions of tiny water droplets, but the droplets don’t automatically fall as rain or snow. They stick to tiny particles like dust.

I think for the entire Intermountain West, it’s becoming more important

If a cloud doesn’t have enough dust, “you have these very static, dead clouds that don’t precipitate, don’t produce any water and just keep moving right through,” he says.

That’s where the silver iodide comes in. Tilley says it’s the right size and shape to help snowflakes form. Cloud seeding only works in certain conditions: cold temperatures with the right wind direction and cloud types. But over a season, Tilley says it can make a difference.

“What we find is a range of anywhere between eight and 15 percent increase in water,” he says.

The silver iodide eventually ends up in the local environment, where some worry it’s a contaminant, though Tilley says tests show it’s only a trace amount.

Cloud seeding has been used for six decades in California. In the early days, it was closer to “magical thinking,” an idea Tilley says has stuck around. “We get voodoo,” he says. “We get Dr. Frankenstein. We get all sorts of things. But we’ve been able to refine the technology.”

No Silver Bullet

“For a long time there’s been hope that we could somehow figure out of a way to squeeze more water out of nature,” says Peter Gleick, president of The Pacific Institute, a water policy think tank.

Gleick says the problem with cloud seeding is that it’s tough to measure or verify how much water it produces and if it’s worth the investment. A review by the National Academy of Sciences in 2003 found that more research needs to be done to prove its effectiveness.

Click to enlarge - cloud seeding areas in California. (Source: California Department of Water Resources)

Click to enlarge – cloud seeding areas in California. (Source: California Department of Water Resources)

“But even more importantly, it’s limited no matter what,” says Gleick. “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.

"So it’s not a silver bullet," he says. "There is no silver bullet for California’s water problems.”

Nine other western states also use cloud seeding, where it’s commonly done with airplanes. The Desert Research Institute is also looking into using drones, potentially cutting the cost of flights.

Across California, water agencies and utilities spend $3-to-5 million a year on seeding, which is estimated to boost runoff by around four percent. That might not sound like much, but these days when every drop counts, Jeff Tilley says cloud seeding getting a second wind.

“I think for the entire Intermountain West, it’s becoming more important,” he says. “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.”

Snowstorms from Dust Storms

Improving cloud seeding may depend on scientists unraveling something that’s still mysterious: what exactly makes it rain?

“It’s incredibly complicated,” says Kim Prather, who studies atmospheric chemistry at the University of California-San Diego.

Prather wanted to know why some clouds produce snow in the Sierra Nevada and others don’t. So, she and her team flew an airplane through the clouds, testing them to see what kinds of tiny particles were forming snowflakes.

What she found was a big surprise. On snowy days, the clouds contained dust from a faraway source.

“Dust had made its way across the Pacific, clear from Asia and even Africa, the Middle East where there are these big dust storms,” she says. “Takes about 7-to-10 days to get here, but it makes it. It’s not a lot of dust. It’s just the right amount of dust that seeds the very top of the clouds.”

Prather says that type of dust can boost snowfall, but other kinds of particles seem to have the opposite effect. Air pollution, from California sources and all the way from Asia, could be adding too many tiny cloud seeds.

“There’s only so much water available and in order to get rain, you have to have big enough droplets for them to fall. The more seeds you have, you have many more tiny droplets. If you have too many seeds, you’re not going to get precipitation out of that cloud.”

“Potentially it’s us affecting our own water supply,” she says. “Potentially it’s stuff coming from much farther away and to be able to sort that out, we’re just at the tip of the iceberg.”

Prather says understanding that process could improve cloud-seeding techniques or show when it may not be effective, something that could be key as California relies more than ever on every last raindrop.

Related

Explore: , , , , , , , , , , , ,

Category: Climate, Engineering, Environment, Radio, Water

  • share this article
  • Facebook
  • Email

About the Author ()

Lauren is a radio reporter covering environment, water, and energy for KQED Science. As part of her day job, she has scaled Sierra Nevada peaks, run from charging elephant seals, and desperately tried to get her sea legs - all in pursuit of good radio. Her work has appeared on Marketplace, Living on Earth, and NPR's Morning Edition and All Things Considered. You can find her on Twitter at @lesommer.
  • CAOCaliforniaResident

    How does this affect rain fall that would naturally be occurring in Colorado or dust bowl Midwest states? Sounds a little greedy of California…

    • MrSharknado

      Sierra Nevada's = natural rain shadow. Rocky Mountains = natural rain shadow. Dust bowl states get there moisture either from the Gulf of Mexico or from air that drops east of the Rockies. Watch the jet stream, when it dips, they get hammered with snow.

    • Invicta81

      Greedy, eh? That's a good term. I think the greedy ones are whomever is benefiting from the pollution these planes are spewing over the United States' skies. California is not the only state with "contrails", or "cloud seeding planes". We are being poisoned. Cloud seeding hasn't worked that I know of and I've spent 27 of my 33 years there. I now live in Oregon and we get the same planes. No more extra rain than usual. In fact, we have far less rain in my opinion than we did when I moved here in 2007. The drought has been all over the news in California, and if they truly have a plan for cloud seeding to work, wouldn't they attempt to assure the people that their needs were trying to be met? This type of theory, "cloud seeding" is unknown to most California citizens .I've asked around

  • lizacrunch

    cloudseeding aka chemtrails is not good for the planet in any way and this man made rain is def not something you'd want to drink. how can people wake ip and see this wrong. mother nature is not one to mess with and this is detrimental to all lif eon this planet. heavy metal toxification is bad on your brain and causes alzheimers nto to mention all the other horrible things it does…

  • xeifrank

    Pollution from China reducing our west coast rainfall amounts?

  • midwestFornian

    Is there any way weather systems sending all this precipitation to the plains/upper Midwest being diverted towards areas that need it more? Seems it'd benefit everyone since the authorities here spend lots of money shoveling/salting the roads and it's resulted in traffic incidents/school closures, and other years it causes damages due to flooding.
    I imagine it's an oft asked question, but one would figure the technology would be providing at least a clue.

  • Bob

    it is called robbing Peter to pay Paul
    we need to stop trying to play God

    • bryce

      i know

      • swag lord

        cool

  • Pingback: Why Shouldn't We Learn to Control Mother Nature? | Consider, Reconsider

  • sally

    There is a bacteria that lives in conifer forests over about 50 years old. This bacteria is a binder like the silver iodide but natural. Humans will never win a war against nature, hard for me to understand how people do not see this. As long as the approach is to extract and "squeeze out a little more" we are inevitably in trouble. What i haven't heard talked about is how the major extraction of forests relates to drought but this is obvious, they are our natural reservoirs, water filters and create rain

    • swag lord

      nawwwwwwwwwwwwwwwwwwwwwwwwwwww dooood

  • Pingback: impossible things podcast | 2.4 California Drought

  • Pingback: impossible things podcast | 2.5 Makin’ It Rain!

  • Pingback: Mr. Iverson's 8th Grade Science | Cloud Seeding Articles