DILLON — One woman expressed fears that winter cloud seeding in the Beaverhead Mountains could rob moisture from the Pioneers, the mountain range whose snowpack serves her family’s summer irrigation.

Preliminary studies of cloud seeding’s potential to augment snowpack in the watershed of the Big Hole River have suggested the Beaverhead Mountains could provide conditions favorable to seeding.

Sarah Tessendorf, Ph.D., responded that research of ongoing cloud seeding operations in several other Western states suggests this “robbing Peter to pay Paul” scenario is unlikely but worthy of more research. She noted too that the Pioneers could host cloud seeding endeavors in the years to come if continuing inquiry indicates it is feasible and cost-effective.

Tessendorf, a scientist with the National Science Foundation’s National Center for Atmospheric Research, spoke Tuesday night at the University of Montana Western. A crowd of more than 40 people attended, with another 20 or so online, as she and Michael Downey of the Montana Department of Natural Resources and Conservation talked about the feasibility of cloud seeding in the Big Hole Watershed.

Listeners included Jim Hagenbarth, a prominent regional rancher and board member of the Big Hole Watershed Committee. He has expressed interest in the potential of cloud seeding to augment mountain snowpack, which is a key water resource for ranchers.

In 2023, the state legislature appropriated funds requiring DNRC to complete an analysis of winter-time cloud seeding to enhance mountain snowpack in southwest Montana. That work continues.

Analysis of river basins in the region determined that conditions in the Big Hole’s watershed were the most promising for a cloud seeding feasibility study, Downey said.

“Cloud seeding is not easy or cheap, so the first thing you need to do is make sure it will work in the area identified,” Downey said.

“Preliminary results show most opportunities for cloud seeding are in the western portion of the Big Hole Basin,” she said, including the Beaverhead Mountains and the Anaconda-Pintler Range, with potential also in the Pioneers. 

Downey cautioned that cloud seeding would not be a cure-all.

“This is not a panacea,” he said. “It’s not going to cure the drought. It’s another tool in the toolbox.”

Big Hole Basin snowpack from the winter of 2023-24 was meager and the flow in the freestone river ran low and warm as the summer proceeded. Climate change suggests this most recent winter is no anomaly.

How might cloud seeding work?

Cloud seeding aims to boost snowfall by dispersing silver iodide particles into clouds containing supercooled liquid water to form ice. 

The dispersal can be accomplished by ground-based generators — triggered remotely or manually — or the particles can be seeded by aircraft.

Western states that already host collaborative cloud-seeding programs include Idaho, Wyoming, Colorado, Utah, Nevada and California.

Research north of Boise conducted with funding from Idaho Power and the National Science Foundation yielded “very clear evidence of ice and snow that reaches the ground” after cloud seeding, Tessendorf said Tuesday.

Idaho Power meteorologists monitor winter storms, looking for opportunities to increase snowfall in drainages that feed the Snake River. The goal is providing more water for the utility’s hydropower projects.

Idaho Power said it operates remote-controlled, ground-based generators and aircraft to disperse the silver iodide particles.

The Idaho Department of Water Resources said that a remote-based ground-generator releases seeding material into the atmosphere and the material is carried by winds moving up and over a mountain, where it then reaches the cloud base to begin ice formation.

“Remote operations allow for placement at higher elevation where snowpack is significantly higher,” the department said. 

Tessendorf and Downey said they anticipate releasing preliminary results of the feasibility study in October, with a final report in early 2025. More work remains to conduct a cost-benefit analysis of cloud seeding's potential in the Big Hole River Watershed.

Computer modeling and simulation will be employed, Tessendorf said.

She said some mountain ranges and some storms are more amenable to aerial cloud seeding and others are more impacted by ground-based seeding.

Tessendorf and Downey planned to meet Thursday night with the Big Hole Watershed Committee in Divide.

Pedro Marques is the watershed committee’s executive director. He has talked before about cloud seeding’s potential.

“Yes, not a panacea,” Marques said. “In fact, that’s the tough part for people to accept. There is no single solution. It’s going to take lots of different projects and approaches across the watershed.

“That said, where we do cloud seed, we’ll want to enhance that basin’s capacity to retain and absorb the extra moisture so, whichever basin that is, we would want to prep projects and make sure they are compatible with fisheries objectives,” he said.   

Marques and other members of the Big Hole Watershed Committee have discussed various water storage strategies for the Big Hole Basin. 

Tessendorf and Downey said states in the West which have adopted cloud seeding programs have used various collaborative efforts to pay for them.  

In Montana, “we’ll probably need some state seed money to get it going and then it’s going to be about these partnerships,” Downey said.

Computer modeling and simulation and cost-benefit analyses will provide more information, he said, to determine whether a three-to-five year pilot study should follow.

Tessendorf said research to date does not suggest the use of silver dioxide particles causes a detectable increase in silver in the environment.

And she said cloud seeding would be suspended if there were indications of significant avalanche danger, or a looming storm was forecast to deliver a wallop of snow.

Meanwhile, this past winter’s scant snowpack in the Big Hole Watershed had far-reaching impacts on people who depend on the river for irrigation, outfitting or recreation and likely affected aquatic life too.

If additional research suggests cloud seeding might be a viable intervention, its constituency could be diverse. Attendees at Tuesday night’s meeting included Clayton Elliott of Montana Trout Unlimited.

That said, many Big Hole River watchdogs believe the state should invest more in acquiring instream flow rights to mitigate against dewatering tied to seasonal irrigation.

DNRC provided a handout about winter cloud seeding during Tuesday’s meeting.

Its text advised, “Ultimately, cloud seeding should be viewed as one tool in a water resource manager’s toolbox of mitigation strategies for long-term water management solutions under a changing climate and growing water scarcity. Specifically, cloud seeding can offer an effective strategy for increasing water supply.”

Katja Friedrich, Ph.D., a professor at the University of Colorado Boulder, is considered an expert on cloud seeding. She spoke earlier this year to the school's alumni association. 

"Cloud seeding is not the holy grail if you think about how to generate water or mitigate droughts," Friedrich said. "But this is an important part because you can maybe produce additional water." 

The summer of 2024 could have used it.