Idaho Power tells Senate committee cloud-seeding program aims to add low-cost water for hydropower, agriculture

Idaho Power staff briefed an Idaho Senate committee on the company’s collaborative cloud-seeding program and said the effort is intended to augment winter snowpack, boosting water supply for irrigation, aquifer recharge, recreation, fish and hydropower generation.

Cresta Davis, senior manager for water resources at Idaho Power, described the utility’s service area and energy portfolio and framed cloud seeding as a water-management tool. "When we talk about cloud seeding in Idaho, we are talking specifically about snowpack enhancement," Davis said.

Davis summarized the program’s history and current scale. The company operated pilot programs beginning in the 1990s, began an operational program in the Payette River Basin in 2003, and expanded partnerships with the High Country RC&D and others through the 2010s. As of 2024 the program included 63 remote ground generators and three aircraft; Idaho Power also added liquid-propane generators to the Payette Basin in 2024. Davis said the company’s 2024 energy mix was about 40% hydroelectric and about 20% natural gas, and that hydropower remains foundational to the company’s system.

Idaho Power presented basin-level benefit estimates derived from a target-control analysis and hydrologic modeling: 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 roughly 200,000 acre-feet for the Payette Basin — a total the company described as "just over a million acre-feet," which Davis said is slightly more than the storage of Brownlee Reservoir. Davis said the program’s cost per acre-foot when spread across beneficiaries is about $4 per acre-foot.

Davis explained the program’s scientific approach: operators introduce ice-nucleating material (commonly silver iodide) or use cooling techniques to encourage supercooled liquid water in winter storms to form ice and fall as snow. On questions about the 2024 propane generators, Davis said propane acts to cool the air passing the generator and is not itself a particle introduced into the atmosphere: "The liquid propane is actually acting to cool that air as it moves past the generator," she said.

Committee members asked about environmental and downstream impacts. Davis cited published studies and program reviews, including Solak et al. (2003) and work by North American Weather Consultants, and said multiple studies have found no environmentally harmful effects from cloud seeding and that some analyses show increased precipitation up to 100–240 kilometers downrange rather than a decrease. She summarized published literature by the Weather Modification Association and Australia’s Natural Resource Commission and said more than 20 studies have reported no adverse effects to human health or ecosystems from typical cloud-seeding agents.

Davis described monitoring and suspension criteria meant to limit flood risk: Idaho Power and partners monitor snowpack and reservoir content and suspend operations if thresholds are exceeded. She said suspension criteria were developed with state and federal agencies and are reviewed annually.

Senators asked technical and public-concern questions. Senator Taylor asked whether propane or propane-fired devices release silver iodide; Davis clarified that propane cools the air and that silver iodide (when used) is the ice nucleant. Senator Blaylock raised constituent concerns about aluminum in water samples; Davis responded that the elements being reported by concerned residents did not match the substances used in the cloud-seeding program and that samples taken near towns are outside the program’s high-elevation target areas. Senator Leahy asked whether cloud-seeding activity is visibly detectable; Davis said it is not: "There is no visible effect," she said, noting that airplane contrails are unrelated to cloud-seeding operations.

Davis described how program benefits are estimated: the program uses a target-control methodology that compares snow water equivalent inside treatment areas to reference (untreated) areas and to pre-program relationships. She said the program assesses accumulation each season (typically measured around April 1 or May 1) and applies the measured percentage increase in snow to hydrologic and operational models to estimate water supply benefits.

No formal committee action was recorded on the presentation. The committee thanked Idaho Power and adjourned.

Why it matters: Committee members heard that cloud seeding is intended to increase reliable water supplies for agriculture, aquifer recharge and hydropower at relatively low per-acre-foot cost, while Idaho Power cited monitoring and published studies to address environmental concerns.