How Windy Gap Works

The Windy Gap Project is located near the town of Granby on Colorado's West Slope. The project consists of a diversion dam on the Colorado River, a 445 acre-foot reservoir, a pump plant, and a six-mile pipeline to Lake Granby.

Windy Gap Project water is pumped from Lake Granby via the Farr Pump Plant to the Granby Pump Canal, where it flows to Shadow Mountain Reservoir and through a connecting channel to Grand Lake.

At Grand Lake Windy Gap Project water enters the 13.1-mile Alva B. Adams Tunnel and flows beneath Rocky Mountain National Park. The water is distributed to Front Range water users via a series of Colorado-Big Thompson Project East Slope storage reservoirs, canals and pipelines.

Aerial view of Windy Gap Reservoir on the Colorado River
Aerial view of Windy Gap Reservoir on the Colorado River

Windy Gap Participants
Six Colorado Front Range communities formed the Northern Water Municipal Subdistrict in July 1970 to plan, finance, build and operate the Windy Gap Project to provide additional future water supplies. The six original Windy Gap participants were:
  • Boulder
  • Estes Park
  • Fort Collins
  • Greeley
  • Longmont
  • Loveland
Following completion and approval of an Environmental Impact Statement, acquisition of 23 permits and licenses, and months of negotiations and a final agreement, Windy Gap Project construction began in July 1981. Completed in 1985, the project began delivering water to Municipal Subdistrict participants in July.

Windy Gap Firming Project Proposed The Windy Gap Project was designed to deliver an average of 48,000 acre-feet of water per year to its participants. However, during wet cycles Lake Granby is often full, leaving little or no space for Windy Gap water.

Windy Gap permits and legal decrees allow the project to divert a maximum of 90,000 acre-feet in a single year. Windy Gap diversions over a 10-year running average cannot exceed 65,000 acre-feet per year.
Colorado-Big Thompson Project and Windy Gap Project map
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More Reliable Water Deliveries
Additional storage, contemplated since the Windy Gap Project’s inception, will provide more reliable Windy Gap water deliveries. The Windy Gap Firming Project would include the 90,000-acre-foot Chimney Hollow Reservoir in the foothills west of Carter Lake.

The existing 445-acre-foot Windy Gap Reservoir was not built for water storage. Instead, it acts as a forebay to pool the water before it enters the Windy Gap Pump Plant and is pumped to Lake Granby.

Watchable Wildlife Area The Windy Gap Watchable Wildlife Area is located at Windy Gap Reservoir on the Colorado River, just west of the town of Granby along U.S. 40. The viewing area is open from May 1 through September 30 and has information kiosks, interpretive panels and viewing scopes along a handicapped-accessible nature trail.

For a detailed history of Windy Gap, download the Windy Gap Project Brochure or see the Windy Gap Project History page.