Shadow Mountain Dam is a zoned earthfill dam on the Colorado River in Grand County, Colorado. Constructed between 1944 and 1946, the Shadow Mountain Dam creates the Shadow Mountain Lake, with a structural height of 63 feet (19 m) and a drainage area of 187 square miles (480 km2). Shadow Mountain Lake is a holding reservoir for water pumped up from Lake Granby just to the south through the Granby Pumping Plant and Canal. Shadow Mountain Lake is connected by a short channel to the natural Grand Lake. The east portal of the Alva B. Adams Tunnel is located on Grand Lake. The Adams Tunnel diverts west slope water to the east slope of the Rocky Mountains for use in agriculture and to serve the populated areas of Colorado, including Denver.