Water provides about a third of the state's electric power and is used to irrigate farmlands. One of the largest federal water projects is the Missouri River's Fort Peck Dam, which was built by the U.S. Army Corps of Engineers and completed in 1940. During the 1950s three other large-scale projects were constructed—Hungry Horse, Canyon Ferry, and Tiber. In 1966 the Yellowtail Dam on the Bighorn River was completed. The Libby Dam on the Kootenai River was dedicated in 1975. State water projects are supervised by the Department of Natural Resources and Conservation. Other state conservation agencies include the Department of Fish, Wildlife, and Parks and the Department of State Lands.