Colorado–Big Thompson Project

Eleven reservoirs, about 18 dams and dikes, the Alva B. Adams Tunnel under the Continental Divide, as well as six power plants, make up the project.

The C-BT is owned and primarily managed by the U.S. Bureau of Reclamation's Eastern Colorado Area Office under its Great Plains Region.

In the late 1930s a solution was found: divert the water via a 13.2-mile (21.2 km)-long tunnel under the Continental Divide and Rocky Mountain National Park.

As a result, the first feature built on the C-BT was Green Mountain Dam and Reservoir, a West Slope facility designed to provide for future water demands in the state's Upper Colorado River Basin.

While the project was originally built for agricultural purposes, it serves multiple demands including municipal and industrial supply, hydro-power generation, recreation, and fish and wildlife.

Today, the "C-BT" serves over 33 cities and towns in northeastern Colorado, including Fort Collins, Greeley, Loveland, Estes Park, Boulder, and Sterling, encompassed by 7 counties, providing a secondary source of water for around 1 million people and an irrigated area of 640,000 acres (2,500 km2).

Windy Gap Reservoir is a small diversion facility located directly below the confluence of the Colorado and Fraser rivers, about 5 miles (8.0 km) downstream of Granby.

The Windy Gap project is not owned by the Bureau of Reclamation, but by the Municipal Subdistrict, a consortium of 14 Front Range cities, water providers and an electric utility.

The water then flows 13.2 miles (21.2 km) under the Continental Divide through the Adams Tunnel, which can carry up to 550 cubic feet per second (16 m3/s) to the eastern slope.

Once the water emerges from the Adams Tunnel just southwest of Estes Park, the system is almost entirely gravity powered, dropping some 2,800 feet (850 m) as it descends to the foothills of the Rocky Mountains west of Loveland.