It rises in southern Summit County, on the western side of the continental divide in the Ten Mile Range, near Quandary Peak.

The west portal for the "Roberts Tunnel" is at the base of Dillon Reservoir.

The Roberts Tunnel is a trans-basin diversion, built by Denver Water in 1962, that diverts water under the Continental Divide from the Colorado River basin into the South Platte River Basin.

The east portal is approximately one mile upstream of Grant, Colorado.

[7] The Green Mountain Dam, 13 miles (21 km) upstream from Kremmling, forms the Green Mountain Reservoir, providing hydroelectric power and diversionary water for irrigation, as part of the Colorado-Big Thompson Project.