Idaho Power briefs committee on cloud seeding: company cites expanded program, environmental studies and suspension criteria

Cresta Davis, senior manager for water resources at Idaho Power, told the committee the utility operates a collaborative cloud seeding program aimed at augmenting winter snowpack and improving water supply for irrigation, hydropower and other uses.

Davis said Idaho Power’s program now includes 63 remote ground generators and three aircraft, and she described the program as a partnership among Idaho Power, the Idaho Water Resource Board and local water users. “On average, the annual benefits break down by basin,” Davis said, citing company estimates: about 240,000 acre-feet for the Boise Basin, roughly 100,000 acre-feet for the Wood River Basin, just over 600,000 acre-feet for the Upper Snake Basin and close to 200,000 acre-feet for the Payette Basin — a total the company described as just over 1 million acre-feet across the Snake River Basin.

Davis and committee members discussed program history and methods. Idaho Power began pilot studies in the 1990s, established an operational program in the Payette Basin in 2003 and expanded the system through the 2010s. In 2024 the company added liquid-propane generators in the Payette Basin, Davis said. Idaho Power explained the program uses “target-control” analyses: comparing snow-water-equivalent accumulation inside targeted cloud-seeding areas with outside control areas and attributing consistent divergences to cloud-seeding activity.

The company estimated a cost near $4 per acre-foot for the program when benefits are aggregated and compared to rental-water prices in contested basins. Davis said the $4-per-acre-foot figure is a system average used to compare program cost to prevailing water-rental rates.

Committee members questioned environmental and chemical concerns. Davis said cloud seeding introduces artificial ice nuclei, most commonly silver iodide, and summarized peer-reviewed and agency studies concluding no measurable adverse effects to human health or environmental receptors. “Over 20 studies have been published. All of those studies have found similar outcomes — no evidence of adverse effects to human health or the environment,” she said. Davis added that Idaho Power conducted sampling in target areas and was not able to detect measurable increases in silver attributable to the program above background levels.

Senators asked technical questions about how liquid propane generators operate; Davis replied that the propane is used to cool air around existing dust particles so supercooled water can adhere and form snow, and that the propane is not adding aluminum or other elements to the atmosphere. The company also described suspension criteria developed with state and federal agencies: if monitored snowpack accumulation or reservoir content exceeds predefined thresholds, seeding operations are suspended until conditions return below those thresholds.

Davis linked the cloud-seeding program to Idaho Power’s interest in preserving hydropower reliability as the state’s energy needs grow. She said hydropower made up almost 40% of Idaho Power’s generation in 2024 and that the program supports reservoir carryover, water quality and recreation, among other benefits. Committee members did not take formal action on the presentation.