Facility

Roberts Tunnel / Dillon Reservoir (Denver Water)

Roberts Tunnel (24.7 miles; completed 1964; operated by Denver Water) is the world's longest water diversion tunnel at its time of construction — tunneling under the Continental Divide from Dillon Reservoir (Snake River/Blue River system; Summit County, CO; 10,000-foot elevation) to Denver Water's Forebay Reservoir on the Eastern Slope. Dillon Reservoir capacity: 257,304 AF. Roberts Tunnel capacity: up to 570 cfs. The diversion physically moves Western Slope Colorado River basin water to the Eastern Slope (Denver metro area) — a transmountain transfer. Western Slope interests in Grand and Summit Counties have contested this diversion for over 60 years. Roberts Tunnel represents the upstream chokepoint: if tunnel operations were disrupted, Denver's primary Upper Basin water supply would be severed. Source: https://www.denverwater.org/your-water/water-supply-and-planning/where-we-get-our-water