As flood waters recede, ski areas step up cloud-seeding efforts

FRISCO, Colo. — Knowing that water is the key to the circle of life, humans for millennia have implored their gods to deliver rain and snow — not catastrophic week-long downpours, but life-giving, field-soaking, stream-replenishing precipitation.

The Maya retreated deep into sacred caves when the weather turned dry, even sacrificing their own brethren in desperate times. The ancient Hawaiian deity Lono was associated with rainfall and food plants, and similarly, the Norse pantheon included Freyr, governing thunder, lightning, winds, rains, as well as fair weather and crops.

In Colorado, ski-area operators and water managers have been known to do a few rain dances and — privately at least — pray to their own God when drought strikes. But in the age of technology and hubris, when nearly every challenge is met with engineering, they aren’t just waiting for Mother Nature to put her cards on the table. Instead, there’s a growing interest in seeding clouds with silver iodide to coax every possible bit of moisture from passing storms.

Weather modification has historic roots in the Cold War era, when both the U.S. and Soviets looked at ways to weaponize weather, and more recently, U.S. intelligence agencies decided to help fund a far-reaching study aimed at determining if there’s a way to mitigate global warming with technology and engineering.

Proponents have claimed for years that seeding can increase snowfall in targeted areas by as much as 15 percent. As a result, water providers like Denver Water, and big ski resorts, including Vail, Breckenridge and Winter Park, are all helping fund a $1 million cloud-seeding program in Colorado’s north-central mountains, hoping to improve ski conditions, as well as boost stream flows and reservoir storage.

Recent news about record-low flows from Lake Powell, the key Colorado River reservoir, has spurred even more interest in enhancing natural precipitation, said one of the state officials who manages what’s formally called a weather modification program. A roster of companies involved in cloud seeding and related activities shows that weather modification is a growth industry.

The state program is run by the Colorado Water Conservation Board, which issues permits and sets basic rules — for example cloud-seeding stops when the snowpack reaches a certain level to address concerns about avalanches and flooding.

But those rules haven’t quelled concerns, as there are still a few people left who probably think that tinkering with the weather on a large scale is probably one of the worst ideas ever. Those sentiments were reflected during a hearing for cloud seeding permits in the early 2000s. Residents of Evergreen turned up en masse to claim that, ever since Vail started seeding clouds (way back in the 1980s), snowfall in their town has declined.


The CWCB program was jump-started with state seed money in the early 1970s, but since then has become 80 percent – 90 percent self-funded through grants and participation by resorts and water providers, with everyone seeing cloud-seeding as a low-cost alternative to building new reservoirs and pipelines. And with an uncertain outlook for Colorado River flows, even downstream states like Arizona and California are ponying up to help pay for cloud seeding in the headwaters.

The question about downwind impacts seems reasonable. After all, there’s only so much moisture in every cloud. But weather experts like Colorado state climatologist Nolan Doesken say there’s not a shred of evidence to show that cloud-seeding affects snow and rainfall downwind of the specific target areas. The weather pattern most suitable for mountain cloud seeding (a steady, moisture-laden jet stream out of the northwest) generally leave the plains high and dry.

On the other hand, Doesken said there’s no clear evidence to show that seeding enhances snowfall anywhere near the amount claimed.

“If it really increased snowfall by 15 percent, you’d be able to see that in streamflow records from, say, the Gunnison Basin (where seeding has been ongoing for many years), but that’s not the case,” Doesken said. Overall, he believes that seeding does boost precipitation, but by a lesser amount than claimed.

The problem is, there has never been a conclusive way to measure whether human tinkering forces nature’s hand. In fact, when Denver Water studied areas targeted by cloud-seeding in 2003, researchers couldn’t find a trace of the silver iodide anywhere in the snowpack.

But that may change in the next few years. Under CWCB rules, cloud-seeding programs must do more stringent target and control evaluations, comparing seeded areas with comparable geographic areas that aren’t targeted by seeding.

The results from the first year of those studies are trickling in and sources say the numbers show snowfall enhancement more in the range of 1 to 7 percent, but one year of data isn’t enough to get the full picture.

“The people who are paying for the cloud seeding want to know,” Doesken said. “So all eyes are on Wyoming,” he said, referring to a state-funded research program that includes randomized seeding and sampling — a key to ensuring a valid measure of cloud seeding’s effectiveness.

In Colorado, the cloud-seeding program looks a little like a backyard chemistry project. Big metal burners are permanently installed at strategic locations upwind of the target areas. When the combination of winds and moisture are just right, the program manager makes the call and on-the-ground operators, for example ranchers in the Blue River Valley north of Silverthorne load the powdered silver iodide into the burners and vaporize it at a high temperature, sending wisps of smoke into the sky.

The tiny particles provide additional nuclei — along with dust particles — for the formation of snow crystals, helping to wring a bit of additional moisture from the atmosphere. Silver iodide is conducive to ice crystal formation at cold temperatures, and propane-based seeding is getting another look as an option for warmer conditions. Placing automated cloud-seeding equipment at remote high-elevation locations, where the material can be fed into the clouds more directly, could also help make the program stronger, experts said.

So when your score your first face shots this coming winter, go ahead and enjoy the celebratory bonfire in honor of Ullr, the Norse god of skiing. But just to be on the safe side, don’t forget to raise your glass in a toast the men and women who promise better living — including more snow — through chemistry and engineering.

[Top image: An operator watches as a cloud-seeding station in Colorado burns silver iodide to help increase snowfall. Photo courtesy Larry Hjermstad, Western Weather Consultants. Bottom: Real flakes or man-made? By Bob Berwyn. ]


  1. I am sick over the seeding that ski areas are doing. I have NO DOUBT that my back yard is a dust bowl due to this big business venture being done without proper research on the effects.

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