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Cloud seeding and Utah's efforts to combat drought

Given recent drought conditions, finding solutions to water shortages has become increasingly critical. One focus point for researchers and the state government is cloud seeding storms to increase snowpack and snowmelt runoff that feeds reservoirs and rivers.

Research on cloud seeding started in the 1940’s, but more recently started garnering public interest as a means of ‘combating’ drought particularly in the western states.

Cloud seeding works by injecting the atmosphere with silver iodide, a nontoxic substance that acts as a catalyst for snowflake formation. Cloud seeding works best when clouds contain supercooled liquid water, meaning it is below 32 degrees F, but has not frozen yet. If storm clouds meet these conditions, releasing silver iodide into the atmosphere before the storm passes can increase the amount of snow the storm generates.

Jonathan Meyer, a faculty member at Utah State University studying cloud seeding, explains how silver iodide works.

“This wonderful molecule silver iodide has such a shape and characteristic that it perfectly mimics these nuclei in the atmosphere that starts the growth of snowflakes,” Meyer explained.

By increasing snowfall from winter storms, cloud seeding could be a potential tool to alleviate drought conditions here in Utah. Joel Ferry, director of Utah Division of Natural Resources, shares the importance of snowpack to water consumption in Utah.

“Over 90% of the water that we consume is coming from snowpack. It's not coming from summertime storms. So summertime storms are great. They help us with a lot of things, but they don't fill reservoirs, snowpack fills reservoirs,” said Ferry.

While we know the process of cloud seeding works and can be stimulated in a laboratory, it’s difficult to measure the success of cloud seeding in a natural system. There is not really a way to determine natural snowfall versus snowfall induced by cloud seeding.

Mathematical modeling has proved particularly helpful in determining how much cloud seeding contributes to snowfall. However it is still difficult to measure how effective cloud seeding is in naturally occurring systems, considering so many factors contribute to weather systems.

Jim Steenburgh is a professor of atmospheric sciences at the University of Utah, who has voiced his concerns on Utah spending money into cloud seeding as a solution.

“The idea that we can see clouds increase Snow is straightforward. The real question is, how much does it increase precipitation. And then if it does increase precipitation, how much of that precipitation is converted into runoff. And that's where it gets really hard, it gets really hard because the atmosphere is a complicated place. There's all these things happening in winter storms,” explained Steenburgh.

While the general effectiveness of cloud seeding is debated, this strategy has been implemented in Utah since the 1950’s, and many feel it is a worthwhile use of resources. Joel Ferry of the DNR discusses plans to increase government spending on cloud seeding efforts.

“Basically we're going from $350,000 to an additional $2.2 million,” Ferry said.

So what does the process of cloud seeding actually look like? The weather forecasting community monitors storm systems and weather patterns, looking for when conditions necessary to seed clouds might present. Monitoring begins about two weeks before a storm’s arrival, but meteorologists typically won’t know whether a storm is right for cloud seeding until one to two days before the storm hits. This gives about 12-18 hours to initiate cloud seeding operations.

Once a storm has been identified for cloud seeding, silver iodide is released into the clouds from ground stations or airplanes. Utah mostly uses ground operations but hopes to implement aerial strategies in the future.

While this approach to water issues has the potential to increase Utah’s current snowpack, it is important to keep in mind the limitations and that it is not the solution to water shortage.

“Now I want people to know, we need to know, we need to recognize that this is not going to save us. There's no silver bullet to get through this drought. But this is one of the components that is really going to help us, it's gonna help us statewide,” Ferry said.

Meyers confirmed this sentiment, speaking of cloud seeding as an important and effective solution for the time being, but it is only a temporary solution to water issues here in Utah.

“At some point, climate change will change the conditions of our wintertime clouds. So cloud seeding becomes less effective later in the century. So anything that we could do now, to buy us some time to figure out more long term water resource strategies and solutions is going to be incredibly invaluable,” confirmed Meyer.

Read Jim Steenburgh’s commentary on cloud seeding here and for more on Utah’s cloud seeding efforts visit water.utah.gov/cloudseeding.

Erin Lewis is a science reporter at Utah Public Radio and a PhD Candidate in the biology department at Utah State University. She is passionate about fostering curiosity and communicating science to the public. At USU she studies how anthropogenic disturbances are impacting wildlife, particularly the effects of tourism-induced dietary shifts in endangered Bahamian Rock Iguana populations. In her free time she enjoys reading, painting and getting outside with her dog, Hazel.