Making it rain: How cloud seeding affects southern Utah’s water resources

Technology to increase precipitation from clouds might sound like something out of science fiction, but the Utah Department of Natural Resources has been using such technology since the mid-20th century. Cloud seeding increases the amount of snow that falls throughout Utah during the winter months.

This process involves ejecting small particles into the atmosphere by burning special flares either on the ground or from a plane to encourage water molecules to accumulate in clouds and fall down to the surface. Raindrops and snowflakes typically rely on dust or salt in the atmosphere in order to form, but cloud seeding helps to increase the amount of precipitation created by a storm by providing fragments for water vapor and ice crystals to condense around. 

“In Utah, [cloud seeders] use silver iodine. Any water vapor that’s in the air will stick to the little particle and will create a raindrop or a snowflake depending on the temperature conditions,” said Aspen Manning, an assistant professor of geosciences at Southern Utah University. “[Cloud seeders] usually do cloud seeding in the winter here in Utah because snowpack is so important for our water supply.”

The Utah Division of Water Resources, one of several divisions housed within the DNR, estimates that approximately 95% of Utah’s water supply comes from snowpack. That means that in years of light snowfall, reservoirs will not be replenished for the following year. Changing weather patterns over the past decades have made precipitation cycle estimates unreliable.

“Right now, there’s a lot of ambiguity in the models about how our area and deserts are going to be impacted by climate change and how that’s going to change rainfall patterns,” explained Manning. “Cloud seeding can be a good opportunity to increase rainfall, but if there’s not enough moisture in the atmosphere, then it’s not going to make rain appear.”

Although the roughly 10% increase in precipitation yielded by cloud seeding might not seem like a whole lot, every drop goes a long way to replenish reservoirs affected by the ongoing drought. Per the DWR, it will take years of above-average precipitation to mitigate the drain on reservoirs.

Water is a precious resource necessary for society to function, and uncertainty about its long-term availability is concerning. Reducing water usage through methods such as cultivating drought-resistant crops, replacing grass lawns with native plants or using a water-efficient dishwasher are beneficial, but increasing the availability of water through techniques like cloud seeding is essential to the sustained availability of water.


Author: Jacob Horne
Photos courtesy of SUU and the Utah Division of Water Resources
Editor: Lily Brunson