Weather Modification

The Roaring Fork Conservancy will host a discussion on cloud seeding on Thursday. The practice involves launching silver iodide into the skies to hasten precipitation.

On the surface, the title of the Roaring Fork Conservancy’s upcoming talk seems like a no-brainer – Plant a Seed, Grow a Snowpack: A Discussion of Cloud Seeding in the Upper Colorado River Basin. Any sensible person, one might think, would be in favor of growing the snowpack and adding to the flow of a river that reportedly gets used up before it ever reaches the ocean.

But not everyone is in favor of cloud seeding, and few people understand how it works and to what extent it’s already being done. The discussion, which takes place at RFC’s River Center in Basalt Thursday at 5:30 p.m., aims to educate the public by exploring the science, lessons learned to date and implications of cloud seeding as a water management tool.

“I’m hoping the audience will walk away better informed about the science and research of cloud seeding and understand that, environmentally, it does not represent an impact to aquatic or terrestrial environmental concerns,” said Dave Kanzer, deputy chief engineer of the Colorado River Water Conservation District, who will give the presentation. “I’ll be talking about the research that is becoming more incontrovertible with every study that it is an effective way, especially here in the inter-mountain West, to increase water supply with minimal environmental or energy impacts, and it is a potential hedge or mitigation approach to climate change.”

One of the concerns those opposed to cloud seeding have voiced is the possibility of removing water vapor from the air and impacting weather in other parts of the country – causing a drought in the Great Plains, for example. This is a hypothetical phenomenon known as “extra-area effects,” but according to Kanzer, research has shown that this is not a consequence of cloud seeding.

“I categorize my role as a myth-buster,” said Kanzer. “There are studies that indicate there are no measurable extra-area effects. The hydrosphere has the ability to regenerate itself, so to speak, so the amount of change we’re able to produce is significant on a local scale but insignificant on a regional scale. It has no impact on those outside the target area.”

The process works by introducing silver iodide, an inert, inorganic compound that has been found to pose less danger from exposure than tooth fillings, into clouds to form the nuclei around which drops of water condense. Silver iodide comes as a yellow or gray powder that is vaporized by what Kanzer called “ground-based generators” and released into the air to rise based on wind patterns and, hopefully, create ice crystals.

“We’re decreasing the time it takes to form a snowflake,” said Kanzer. “In nature it takes a long time, and because that process is so inefficient we can miss out on opportunities, and that moisture can move past some of our target areas and even re-evaporate, meaning it doesn’t precipitate at all.”      

To many, cloud seeding may still seem like a novelty, but just the opposite is true. The science was conceived more than a century ago, and cloud seeding has been tried in various forms since the 1940s. It also may seem like something that isn’t really happening in many places, but that’s not the case, either.

“Attendees at the discussion might be surprised at the level of the investment in infrastructure and operation, maintenance and research that has been going on for the last 40 to 50 years,” said Kanzer. “Vail Resorts, in particular, their program celebrated its 40th year, and they’re going strong. Cloud seeding is a mature science and industry that has the potential to aid in our management of water resources, and its full potential has not been reached.”

It’s a compelling argument for a practice that is becoming more and more a part of the conversation when the question of how to meet the West’s growing water demands arises. Still, Kanzer knows lots of people have lots of questions, including, as it turned out, the folks at RFC, which is why they invited Kanzer to be the second speaker in their Brooksher Watershed Institute 2019 Winter Speaker Series.    

“We have been hearing a lot about cloud seeding,” said Christina Medved, RFC’s director of community outreach, “and people started asking us what we thought of cloud seeding and how effective it is, and it was like, ‘Honestly? We don’t know.’ But we need to know because this is getting closer to home, so we thought we’d have Dave come here and talk to everybody about it.”

The discussion will take place in the classroom of the River Center, which opened adjacent to Basalt’s Old Pond Park last August. Since that time, the center played host to hundreds of school groups and other visitors through the fall, but RFC needed something to fill in the quieter winter months, leading to the creation of the speaker series, which concludes March 11 with a discussion on Restoring Critical Riparian Habitat in the Age of Invasives.

The conservancy, which protects the watershed of the Roaring Fork River, hopes to elevate the conversation about our water and how it’s valued while helping attendees and others understand how we fit into the bigger water picture and what’s being done regionally to address those issues. As such, the conversation on cloud-seeding was a natural fit, and Medved thinks the 50-room classroom might fill to capacity. She recommended contacting the conservancy at or (970) 927-1290 to reserve a seat.

If you can’t make it to Thursday’s talk but you’d like to know more about cloud seeding, Kanzer will also be leading a workshop on March 14 at the Pitkin County Courthouse, starting at noon.

Todd Hartley is the special sections editor for Aspen Daily News. He can be reached at