Enhancing our water supply 

Utah has been cloud seeding since the early 1950s to help augment the state’s water supply. The Cloud Seeding Act of 1973 gave authority to the Utah Division of Water Resources to oversee state cloud seeding projects. The Utah Legislature continues to support operational cloud seeding activities and pushes for innovation in the field. 

Cloud seeding takes place in Utah from the months of November and into April. It only occurs during snowfall events where atmospheric conditions (such as temperature and moisture) favor the enhancement of snow – never under clear conditions. 

How cloud seeding works

Utah uses both ground-based seeders and drones. In both seeding methods, silver iodide is dispensed into winter clouds to help form ice crystals. Ground-based seeders are placed along foothills and higher elevations, and the release of the silver iodide  is timed so that air currents carry them high into the cloud. Drones operate inside the cloud for more precise targeting.

This process is effective because clouds are formed by water vapor and airborne particles (cloud condensation nuclei). Under certain natural conditions, water droplets will freeze together around the particles and, when heavy enough, fall from the sky as snow. Often, the amount of water that can fall as snow is limited by the number of particles around which ice crystals can form. That is why adding particles, or seeds, facilitates and accelerates the process. This may lead to more snow falling than would have under natural conditions.

Why Utah cloud seeds

Since snowpack is Utah’s largest reservoir, increasing the amount of snow that falls is a win for the water supply. It doesn’t work just anywhere. The conditions have to be right. Fortunately, Utah’s topography, climate and reservoirs make winter snowpack enhancement cost-effective. Statistical analysis shows an average increase in precipitation of 5-15% in seeded areas. The field program is funded jointly by the state and local water interests. 

Cloud seeding can only occur when there is sufficient water in the atmosphere along with other meteorological parameters (i.e. during precipitation). It is a long-term water management strategy that enhances snowfall. See our FAQ sheet to learn more.

Environmental considerations

Cloud seeding is a scientifically validated method for enhancing snowpack, has been thoroughly researched and is conducted with transparency and strict adherence to environmental regulations. 

Cloud seeding uses small amounts of silver iodide – a compound that exists naturally in the environment at low concentrations and is not known to be harmful to the environment, humans or wildlife – to aid in the formation of ice crystals. Silver and iodide have a strong covalent bond that keeps them insoluble in water and in a solid form. This keeps silver iodide safe, with only a maximum concentration of silver in water of 0.984 micrograms per liter – far below the natural background levels of silver in Utah and neighboring states and below the limits to impact aquatic life, drinking water and terrestrial plants.