The Gunnison Tunnel is a 5.8 mile (9.3 km) irrigation tunnel constructed between 1905 and 1909 by the Bureau of Reclamation.[2] At the time of its completion, it was the longest irrigation tunnel in the world. The tunnel diverts water from the Gunnison River in the Black Canyon of the Gunnison to the arid Uncompahgre Valley around Montrose, Colorado.