Idaho Power outlines cloud-seeding program, estimates ~1 million acre-feet annual benefit across basins

Idaho Power officials briefed the Senate Agricultural Affairs Committee on the utility’s collaborative cloud-seeding program, describing program history, operations, estimated benefits, environmental studies, and operational safeguards.

Cresta Davis, senior manager, water resources, Idaho Power, described cloud seeding in Idaho as "specifically about snowpack enhancement." Davis told the committee the company now operates 63 remote ground generators and three aircraft across target areas from western Wyoming through the Payette Basin and that the program expanded in 2024 to include liquid-propane ground generators in the Payette Basin.

Idaho Power provided basin-by-basin benefit estimates derived from a target-control methodology that compares snow accumulation inside seeded target areas against outside control areas. The company estimated average annual additional water supply of roughly 240,000 acre-feet in the Boise Basin, just over 100,000 acre-feet in the Wood River Basin, about 600,000 acre-feet in the Upper Snake Basin, and roughly 200,000 acre-feet in the Payette Basin—totaling just over 1 million acre-feet. Davis said that, when expressed as cost per acre-foot, cloud seeding is roughly "$4 per acre-foot," which the company compared to rental-water market rates in some basins.

Davis addressed common concerns. On downstream impacts, she cited studies (including Solak et al., 2003, and analyses by North American Weather Consultants) showing target-area increases and little or no measurable downrange reduction; she summarized the atmospheric reasoning presented by Idaho Power team members that only a small percentage of available atmospheric water is converted to precipitation during a winter storm, so seeding increases fall locally without significantly depleting downrange vapor. On environmental and health effects, Davis noted that silver iodide is used as the ice-nucleating agent and that multiple published studies and reviews (Weather Modification Association, Australia's Natural Resource Commission and more than 20 additional studies) have found no adverse environmental or human-health impacts. "It is inert and it can't be taken up by, you know, the things out in the biota," Davis said when explaining silver iodide's chemical behavior as presented to the committee.

Idaho Power also described program safeguards. The company told the committee it applies suspension criteria—developed with state and federal agencies and reviewed annually—that halt seeding operations if monitored snowpack and reservoir conditions exceed thresholds that could increase flood risk.

Committee members asked technical and operational questions, including how liquid-propane generators function (Davis said propane cools the air around existing condensation nuclei to encourage ice formation rather than adding particles), how program benefits are measured (annual target-control and regression analysis on snow-water-equivalent measurements, typically evaluated after winter), and whether cloud-seeding effects are visible to the public (Davis said there are no visible trails from cloud seeding operations). Several senators asked about aluminum concerns in local water samples; Davis said the program does not use aluminum and studies attempting to detect silver from seeding in target-area samples were unable to measure a program signal above background.

Idaho Power emphasized collaboration and funding: the program has included financial contributions and operations/maintenance support from the Idaho Water Resource Board and local water users; partners share capital and O&M costs and receive attributed benefits per the collaborative agreements. Davis framed cloud seeding as one water-management tool that supports irrigation, aquifer recharge (including the Eastern Snake Plain aquifer), recreation, fish habitat, and the utility’s hydropower-based generation capacity.

The committee took no formal action on the presentation. Members thanked Idaho Power for the briefing and adjourned.