Print Back to top

Dry winter — can cloud seeding help?

The science behind sending ‘snow seeds’ into the sky, and why successful seeding needs help from Mother Nature.

Morning, noon and night, all winter long, a team of scientists track every aspect of Colorado’s weather. They’re looking for ideal conditions to send millions of “snow seeds” into the sky.

The scientists are experts in cloud seeding — a weather modification technique used across western Colorado to enhance snowfall and boost mountain snowpack.

“Cloud seeding doesn’t make clouds, it’s about getting more snow out of a storm,” said Joe Busto, cloud seeding program manager with the Colorado Water Conservation Board. “We need good, juicy storms for the process to work effectively.”

Eric Hjermstad, field operations director for Western Weather Consultants, lights a cloud seeding generator north of Silverthorne, Colorado.

Cloud seeding works by using a propane-fired generator to send particles of silver iodide into the sky. Winds lift the silver iodide particles into the clouds where they attract water vapor, grow, and fall as snowflakes.

“There are storm clouds that blow through Colorado that may have plenty of liquid, but not enough particles to form snowflakes,” Busto said. “What we’re doing is adding more particles into the clouds and using natural processes to harvest that water vapor and squeeze more snow out of a storm. Silver iodide is essentially a dust particle for cloud vapor to bond to.”

Busto said it’s important to understand that cloud seeding is most effective in average-to-wet winters.

“The dry winters are when everyone hopes cloud seeding can help with the snow, but unfortunately that’s not how it works,” he said. “We gauge success by looking at snow totals over the years, not single seasons.”

There are seven cloud-seeding programs in Colorado permitted by the state through the Department of Natural Resources. Forty organizations spend an average of about $1 million annually on the seven programs.

Denver Water, through the Front Range Water Council, helps fund the Central Colorado Mountains River Basin Cloud Seeding Program. Other partners include the Colorado Water Conservation Board; the Colorado River District; Breckenridge, Keystone and Winter Park ski areas; and water districts in Arizona, southern California and Nevada.

Together, the CCMRB partners provide an average of $250,000 in total to fund the program each year.

The CCMRB program began in 2012, and the partners plan to continue funding it into the future. Under the program, Desert Research Institute operates two high-elevation remotely operated cloud seeding generators in Grand County, Colorado. Western Weather Consultants operates more than 20 manually operated machines in Eagle, Pitkin and Summit counties.

This cloud-seeding generator in Grand County, Colorado, is remotely operated by Desert Research Institute. The machine is used to seed clouds north of Winter Park Ski Resort.

The generators are placed in locations to boost snowpack in the Upper Colorado River Basin, which provides water for eastern and western Colorado, as well as communities in downstream states.

Weather conditions must meet a set of state criteria before seeding operations can begin including temperature, height of the clouds and wind direction. Seeders also look for storms that carry high amounts of moisture.

Critics may question the effectiveness of cloud seeding, but Busto points to a number of studies that show cloud seeding can boost snowfall by 5 to 15 percent. That would equate to getting about an extra inch of snow out of a 10-inch snowstorm, according to Busto.

“You can’t seed every storm,” he said. “Only about 10-14 storms that pass through the state each winter meet the criteria.”

Desert Research Institute and Western Weather Consultants rely on automated SNOTEL readings, ski resort data and weather models to estimate the impact of seeding operations.

Western Weather estimates that during seasons with a high number of good conditions, cloud seeding has added an average of 60,000 acre-feet of additional water to the Upper Colorado River Basin in the CCMRB coverage area.

“A couple inches here and there add up,” said Eric Hjermstad, field operations director at Western Weather Consultants. “If you consider 1 inch of extra snow spread across 300 square miles, that’s a big boost to the water supply.”

A manually operated cloud seeding generator north of Silverthorne, Colorado. The machine boosts snowpack in the Upper Colorado River Basin, but also enhances snowfall at Keystone Ski Resort, seen in the distance.

Denver Water participated in cloud-seeding programs in the early 1950s and 1980s. Recent projects started up again after the 2002-03 drought.

“Mountain snowpack provides 80 percent of our water supply,” said Dave Bennett, director of water resource strategy at Denver Water. “So while it’s tough to pinpoint the exact impact of cloud seeding, Denver Water, the ski areas and our partners in the Front Range Water Council feel there is enough benefit to support the program.”

Since cloud seeding’s early days back in the mid-1900s, advancements in technology have dramatically improved cloud-seeding efforts, according to Busto.

“We’re going to add a state-of-the-art cloud seeding generator later this year,” he said. “Our goal is to continue to add more remote-operated generators and get them higher up the mountain where research says they’re most effective.”

Advancements in weather forecasting and monitoring have also improved the field. New developments include high-resolution weather modeling, simulated weather balloon launches, ceilometers that measure cloud base, and radiometers that characterize super-cooled liquid water to help determine when to seed during a storm system.

“We’re getting more up-to-date data,” Hjermstad said. “The more information we have about atmospheric conditions, the more efficient we can be about when to seed.”

Breckenridge, Keystone and Winter Park ski areas help fund the CCMRB program to boost snow for skiers and snowboarders.

Snow that falls on the resorts eventually melts and drains into rivers and streams that feed the Upper Colorado River Basin, which is used by Denver Water and other Front Range water suppliers.

Cloud seeding generators for the CCMRB program are located in Eagle, Grand, Pitkin and Summit counties.

“We’ve been cloud seeding on and off over the past 30 years,” said Doug Laraby, planning director at Winter Park Ski Resort. “If we can add a few more inches, that’s great for skiers and when the snow melts, it’s great for water supply.”

As advancements improve in the field, silver iodide continues to be the industry standard for cloud seeding. “After 50 years of operations and research in the U.S., silver iodide has not been proven to be harmful to the environment,” Busto said.

As for the future of cloud seeding in the state, Busto is working to increase funding for programs in Colorado and is building partnerships with other Western states.

“We’re constantly evaluating the program and looking at ways to increase our efficiency and effectiveness,” Busto said. “Cloud seeding isn’t a cure-all for water supply, but we hope with all the partners and states working together we can make our programs stronger in the future.”