Idaho Power’s cloud seeding program benefits agriculture, fish and other wildlife habitat, aquifer recharge and water quality as well as recreational users such as skiers and snowmobilers while providing increased generation at the company’s hydroelectric facilities

In the Central Mountains, which includes the Payette, Boise and Wood River basins, our program operates 32 remote ground-based generators and two airplanes. The program in the upper Snake River basin includes 25 remote ground-based generators operated by Idaho Power, 25 manual ground-based generators operated by the High Country Resource Conservation and Development program and one airplane for cloud seeding operations. Idaho Power provides meteorological data and weather forecasting to guide seasonal cloud seeding operations throughout all basins associated with the program.

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.

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.

Silver iodide has been used as a seeding agent in numerous western states for decades without any known harmful effects. Silver iodide is insoluble in water which is a characteristic that keeps it from having harmful effects.

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.

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. For more information, contact:

• North American Weather Modification Council nawmc.org
• Weather Modification Association weathermodification.org
• Shaun Parkinson, PE, PhD, Water Resources Leader, Idaho Power sparkinson@idahopower.com
• Derek Blestrud, Senior Atmospheric Scientist, Idaho Power dblestrud@idahopower.com