Snowpack Enhancement

Snowpack enhancement (also known as cloud seeding or weather modification) is a key, creative solution to provide our communities with more water.

This method has been used across the western United States, including Colorado’s Western Slope, to increase the amount of snow that falls during winter storms. In 2022, the St. Vrain and Left Hand Water Conservancy District implemented the Front Range’s first snowpack enhancement program in collaboration with the Colorado Water Conservation Board (CWCB) and the Left Hand Ditch Company.

Our program is focused on the St. Vrain Creek and Left Hand valleys and offers a safe, cost-effective way to build reliable water supplies and increase the amount of water available for local communities, lakes, creeks and the environment.

Snowpack enhancement is a part of a comprehensive approach that includes water conservation, water sharing, improved water management and multipurpose off-channel storage. All of these are necessary to meet our future water needs.

Snowpack Improvement
Snowpack 3

How does it work?

Snowpack enhancement increases the amount of snow that falls during winter storms by adding small amounts silver iodide to clouds using ground-based, remotely operated cloud seeding generators. The silver iodide is chemically similar to water molecules and interacts with the super cooled liquid in the clouds to form more ice crystals and subsequently more snow. Once the snow melts, the trace amounts of silver iodide break down into silver and iodine, both naturally occurring and shown to be safe for the environment and people.

Weather Modification

How much snow is produced?

Snowpack enhancement efforts typically increase the amount of snow from any given storm by around 5-10%. If one inch of snow falls, the snowpack enhancement could add 0.05 to 0.10 inches of additional snow. While that is a small amount for a single storm, over the course of a winter season and on the scale of an entire watershed, that can amount to a lot of water. Snowpack enhancement is estimated to increase snowpack by 5-10% over a season, increasing stream flows for our area of up to 10,000 acre-feet (one acre-foot equals 325,851 gallons).

Is the program “stealing” snow from down-wind locations?

Snowpack enhancement does not significantly impact snowfall down-wind of the target area. In any given winter storm, only 10% of the total moisture in a cloud falls as snow. Snowpack enhancement only decreases the total moisture in a cloud by 0.5-1.0%, leaving plenty of moisture available for down-wind locations.

Is it safe?

Our review of the science and studies indicate using silver iodide for this purpose is safe. The amount of silver iodide used in snowpack enhancement operations is extremely small. Because cloud seeding takes place on a microscopic level, very little silver iodide is needed for the process to work. These small amounts are then dispersed over an area of hundreds of square miles. The amounts of these chemicals are so small that they are only detectible in snow with high precision instrumentation. Once the silver iodide enters the environment after falling in snow, it breaks down into silver and iodine, both of which are naturally occurring. The silver and iodine in the water and soil after snowpack enhancement is so far below background or naturally occurring levels that they are undetectable.

More Information and News

The State of Colorado allows weather modification operations permitted by the CWCB. More information on the permitting process and the rules/regulations associated with the permit can be found on the CWCB website. The District’s snowpack enhancement program is operated by the North American Weather Consultants (“NAWC”).

View recent news stories on snowpack enhancement


Visit the District’s YouTube for videos on snowpack enhancement



1715 Iron Horse Drive, Suite 250
Longmont, CO 80501

Email: [email protected]
Phone: 303-772-4060

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