Cloud seeding last winter added more snow-water content than usual to southern Idaho’s river basins.

Additional water supply from cloud seeding can benefit uses such as irrigation, hydropower production, fisheries and recreation. It added to already strong snowpack in the region.

“This was a great year for cloud seeding,” Kresta Davis, Idaho Power Co. senior manager of water resources and policy, said in a release from the state Water Resource Board. The board and the Boise-based utility work together.

Snow-making activities added 400,000 acre-feet of snow water content in the Upper Snake River Basin, 190,000 acre-feet in Henry’s Fork of the Snake, 107,000 acre-feet in the Big Wood, 270,000 acre-feet in the Boise basin and 250,000 acre-feet in the Payette basin, according the board’s release.

Cloud seeding in the past 20 years has increased snow-water equivalent by an average of 5% a year in the Henry’s Fork basin, Idaho Power officials told Capital Press. Last winter’s gain due to cloud seeding was 10%.

Other increases last winter were 12% in the Upper Snake basin compared to the long-term average of 9%, 13% in the Wood River system compared to 10%, 18% in the Boise basin compared to 13%, and 17% in the Payette basin compared to 11%.

Natural variations between target and control gauges can account for some of the year-to-year difference, said Derek Blestrud, senior atmospheric scientist with the company. He is more confident in the long-term average than in a result for a single year.

Last winter brought substantially more opportunities to generate snow than Idaho Power saw in the previous two years, spokesman Brad Bowlin said.

The company used the same amount of equipment, but seeding from ground-based generators was significantly above the long-term average while aircraft flight time was flat to slightly below average, he said. Winter conditions favored ground-based seeding that targeted lower-elevation storms.

“Conditions were great for ground-based seeding last winter,” said Shaun Parkinson, Idaho Power meteorology and cloud seeding leader. Temperatures were cooler close to the ground, “and there was abundant liquid water in the storms at low elevations.”

Storms “had an abundance of super-cooled liquid water, which is what we target with our seeding operations,” he said. Numerous atmospheric river situations brought substantial rain and snow to much of California and Oregon before moving into Idaho Power’s area, and “the number of storms enabled us to look for the very best opportunities to seed.”