Chattahoochee (chătˌəhōˈchē) [key], river, 436 mi (702 km) long, rising in N Ga., and flowing generally SW to the Ala.-Ga. border and then S along it to join the Flint River in Lake Seminole on the Ga.-Fla. line; the combined waters form the Apalachicola River, c.90 mi (140 km) long, which flows S to Apalachicola Bay, NW Fla. The Jim Woodruff Dam impounds Lake Seminole and provides hydroelectricity. The Columbia, Walter F. George, Bartletts Ferry, and Goat Rock dams produce power and regulate navigation on the Chattahoochee. Northeast of Altanta, Buford Dam forms Lake Sidney Lanier, used for recreation and the main source of metropolitan Atlanta's water supply. The Flint River, 330 mi (531 km) long, rising in W central Georgia, is navigable to Bainbridge, Ga., and is a valuable source of power in W Georgia.