Granby Dam (National ID # CO01656) is an earthfill dam that dams the Colorado River 5.5 miles (8.9 km) northeast of Granby, Colorado in Grand County, Colorado. This 298-foot (91 m)-tall dam was constructed between 1941 and 1950 and has a drainage area of 311 square miles (810 km sq). The Granby Dam's reservoir is known as Lake Granby, the largest reservoir component of the Colorado-Big Thompson Project, which diverts water from the west slope of Colorado to populated areas, including Denver, on the east slope.
In addition to the waters of the Colorado, water from Willow Creek just below the dam is pumped up 175 feet (53 m) to Lake Granby. Water from Lake Granby is pumped 125 feet (38 m) higher by the Granby Pumping Plant to the Granby Pump Canal, which extents 1.8 miles (2.9 km) to Shadow Mountain Lake, from which water is diverted through the Alva B. Adams Tunnel to the East Slope. This damsite does not generate any power directly; power is generated at other locations in the Colorado-Big Thompson Project.