High Quality Content by WIKIPEDIA articles! Arrowrock Dam is a concrete arch type dam on the Boise River, in Idaho, U.S.A. It opened in 1915 and is located on the border between Boise County and Elmore County, upstream of the Lucky Peak Dam and reservoir. The spillway elevation for Arrowrock is 3,219 feet (981 m) above sea level and its primary purpose is to provide irrigation water for agriculture.