To form snowflakes, water vapor in clouds must first attach to something, like a dust particle. Idaho Power seeds clouds by introducing very small amounts of silver iodide into winter storms that meet very specific criteria, such as wind speed and direction, temperature, and water content.

Adding the silver iodide particles can kick-start snowflake formation, causing increased precipitation from passing winter storm systems.

Idaho Power uses two methods to seed clouds: remote ground generators located at high elevation and airplanes that burn special flares within storm clouds. Both methods release silver iodide into passing storms. Minute water particles within the clouds freeze on contact with the silver iodide particles and eventually grow and fall to the ground as snow.

Liquid propane can also be used in storms where clouds are near ground level and temperatures are only slightly below freezing.

Idaho Power began its cloud seeding program to provide additional water for our hydroelectric power plants, which comprise our largest energy source and provide safe, reliable, affordable, clean power for our customers. The initial program began in 2003 in the Payette River watershed.

Understanding that additional snowpack from cloud seeding also benefits agriculture and aquifer recharge, we expanded the program starting in 2008 into the Upper Snake River basin above Milner Dam. This was in collaboration with the Idaho Water Resources Board as part of the state’s Eastern Snake Plain Aquifer Comprehensive Aquifer Management Plan.

In 2015, at the request of irrigators, Idaho Power expanded the program again to cover the Wood River and Boise River basins.

The additional water also supports fish, wildlife habitat, and water quality as well as snow- and water-based recreation.

The Idaho Water Resource Board (IWRB), with support from Idaho Power, reported initial benefits to water supplies in each basins where we conduct seeding. For example, in the upper Snake River basin, preliminary IWRB studies show up to 32% of the benefits accrue to within-basin natural flow use and 10% to increased reservoir carryover in a 4,000,000 acre-foot reservoir system.

The state-managed recharge program benefits by 12% of the water generated and hydropower downstream of Milner Dam improves by up to 13%.

We operate remote ground-based generators and aircraft to target high elevations In the Central Mountains (the Payette, Boise and Wood River basins), and the upper Snake River basin.

The original program was established to increase snow accumulation in the Payette River watershed beginning in 2003. In partnership with the Idaho Water Resources Board (IWRB) and as a part of the Eastern Snake Plain Aquifer Comprehensive Aquifer Management Plan, Idaho Power expanded the program into the upper Snake River basin above Milner Dam beginning in 2008. In 2015, at the request of irrigators, Idaho Power again expanded the cloud seeding program to cover the Wood River and Boise River basins.

No. Aerial seeding in Idaho only takes place in or above existing winter storms over mountainous areas. Cloud seeding does not create clouds. It only makes existing storms more efficient at producing precipitation under the right conditions.

The principle of cloud seeding was discovered in 1946 by American chemist and meteorologist Vincent Schaefer. The use of silver iodide to enhance the formation of ice crystals in clouds was discovered only a few days later by noted atmospheric scientist Dr. Bernard Vonnegut.

The technology has been used since the late 1940s to enhance precipitation and also to dissipate fog and reduce the size of hailstones.

Data from the World Meteorological Organization, compiled in 2000, listed 74 projects ongoing in 23 countries worldwide. In 2001 the National Oceanic and Atmospheric Administration (NOAA) documented 66 projects conducted in the western U.S.

A wide range of entities sponsor cloud seeding programs in the U.S. They include municipal, county and state governments; irrigation, water resource and water conservation districts; airports; ski resorts; and private industry. (source: North American Weather Modification Council)

Active programs exist in several states, including Idaho, North Dakota, California, Texas, Colorado, Wyoming, Utah and Nevada.

Idaho Power has developed target-control analyses to evaluate the annual average benefits associated with the collaborative cloud seeding program. Based upon these analyses, the company estimates the cloud seeding programs provide approximately 600,000 acre-feet of additional water in the Payette, Boise and Wood River basins as well as over 400,000 acre-feet of additional water each year in the upper Snake River basin. One million acre-feet of water can generate approximately 844,500 megawatt-hours if used for hydroelectric production — enough to power roughly 74,000 homes.

The IWRB, with support from Idaho Power, studied and reported initial benefits to water supplies in each of the above-mentioned basins. For example, in the upper Snake River basin, preliminary IWRB studies indicate that based upon average water year modeling, up to 32% of the benefits accrue to within-basin natural flow use and 10% to increased reservoir carryover in a 4,000,000 acre-foot reservoir system. The IWRB-managed recharge program benefits by 12% of the water generated and hydropower downstream of Milner Dam improves by up to 13%.

Studies conducted by the Desert Research Institute from 2003 to 2005 and a 2017 study funded by the National Science Foundation support the effectiveness of Idaho Power’s program.

Idaho Power seeds clouds by introducing additional ice nuclei (silver iodide) into winter storms. The additional ice nuclei increase precipitation from passing winter storm systems. If a storm has abundant water (vapor or small liquid droplets) and appropriate temperatures, the conditions may be optimal for cloud seeding to increase precipitation.

Idaho Power uses two methods to seed clouds: remote ground generators located at high elevation and airplanes that burn special flares within storm clouds. Either method successfully releases silver iodide into passing storms. Minute water particles within the clouds freeze on contact with the silver iodide particles and eventually grow and fall to the ground as snow.

The seeding agent we use is silver iodide, which has been used in numerous western states and globally for decades without any known harmful effects. Silver iodide is insoluble in water which is a characteristic that keeps it from having harmful effects on water quality or biota.

Idaho Power works closely with state and federal authorities to ensure our cloud seeding operations comply with all relevant environmental and land-use guidelines.

The active ingredient is silver iodide, which is a stable molecule that does not readily dissolve in water. The solution used in our generators is 97% acetone, which is used to create a steady flame that disperses the silver iodide into the storm clouds. Acetone breaks down into carbon dioxide and water with trace amounts of small hydrocarbons similar to car exhaust.

Silver iodide makes up about 2% of the solution, and the remaining 1% is commonly used combustible salts that increase the efficiency of the acetone flame.

Some ground-based generators use liquid propane to induce snow formation.

Flares used for aerial seeding are a similar combination of silver iodide and combustible salts without the acetone because the material is being deposited directly into the cloud. They also include materials that hold the flare together and control how evenly it burns. These materials are consumed during combustion.

The combustible materials in flares are the same materials commonly used in road flares and fireworks. By comparison, common road and marine flares as well as fireworks contain tens or hundreds of times more fuel and oxidizer than cloud-seeding flares. The flares used for seeding are designed to burn slowly and steadily rather than producing light, sparks, or explosions.

Yes. Idaho Power uses target-control analysis to evaluate the annual average benefits of the cloud seeding program. This means comparing data associated with snowpack characteristics from an area targeted by seeding with data from a nearby “control” area that is not seeded. Using historical data and modern measurement tools with computer modeling, we estimate that our cloud seeding project generates an annual average increase in snowpack of 10-15%.

Studies conducted by the Desert Research Institute from 2003 to 2005 and a 2017 study funded by the National Science Foundation support the effectiveness of Idaho Power’s program.

Research has shown no evidence that cloud seeding in one location causes a reduction in precipitation in neighboring areas. During a storm, a relatively small portion of the overall atmospheric water falls to the ground as precipitation. Cloud seeding increases that amount slightly (5%–15%), leaving most of the water in the atmosphere as part of the storm system. The additional precipitation that falls is not lost from the water cycle.

Typically, a well-run cloud seeding program would affect less than 1% of the total available water in a storm system.

No. That project is being conducted by a company unaffiliated with Idaho Power in an area outside the drainages that we target to increase snowpack that ultimately feeds the Snake River.

Idaho Power works closely with federal, state and local authorities to ensure our cloud seeding operations comply with all relevant environmental and land-use guidelines.

• North American Weather Modification Council: nawmc.org
• Weather Modification Association: weathermod.org
• For questions specific to Idaho Power’s program, email questions@idahopower.com