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Snowpack Enhancement Project

Snowpack enhancement (also known as cloud seeding or weather modification) 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 (“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.

Focused on the St. Vrain Creek and Left Hand Creek basins, the program is a safe and cost effective way to help build a reliable local water supply and increase the amount of water available for people, lakes, streams and the environment.

The District believes snowpack enhancement is a key creative solution to address water scarcity. Snowpack enhancement is a part of a comprehensive approach that includes water conservation, water sharing, improved water management, and multipurpose off-channel storage, that are necessary to meet our future water needs.

Common Snowpack Enhancement Questions:

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 in to silver and iodine, both naturally occurring and shown to be safe for the environment and people.

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 significant amount of water. Snowpack enhancement is estimated to increase snowpack by 5-10% over a season resulting in a like increase of streamflows for our area of up to 10,000 acre-feet (one acre-foot equals 325,851 gallons).

Are you “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

The State of Colorado can allow weather modification operations through an issuance of a permit from 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”).

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