The Boise River is a tributary of the Snake River in the Northwestern United States. It drains a rugged portion of the Sawtooth Range in southwestern Idaho northeast of Boise, as well as part of the western Snake River Plain. The watershed encompasses approximately of highly diverse habitats, including alpine canyons, forest, rangeland, agricultural lands, and urban areas. Description The Boise River rises in three separate forks in the Sawtooth Range at elevations exceeding , and is formed by the confluence of its North and Middle forks. The North Fork, long, rises in the Sawtooth Wilderness Area, along the Boise–Elmore county line, northeast of Boise. It flows generally southwest through the remote mountains in the Boise National Forest. The Middle Fork, approximately in length, rises within of the North Fork in the southern Sawtooth Wilderness Area in northeastern Elmore County. It flows west-southwest near the town of Atlanta, joining the North Fork to form the Boise River, approximately southeast of Idaho City. The main stream flows southwest into Arrowrock Reservoir, joining the South Fork from the Anderson Ranch Dam. The South Fork rises in northern Camas County in the Smoky Mountains and Soldier Mountains of the Sawtooth National Forest north of Fairfield, east of Boise. It flows generally southwest, descending through a basalt canyon to fill the Anderson Ranch Reservoir, then turns northwest in central Elmore County. It joins the main stream as the southern arm of Arrowrock Reservoir, east of Boise. Downstream from its confluence with the South Fork, the river flows generally west, adds the major tributary of Mores Creek along Highway 21, and passes through Lucky Peak Dam to emerge from the foothills southeast of Boise. It passes over several irrigation diversion dams above the city, the first and largest is the century-old Boise River Diversion Dam for the concrete New York Canal, which terminates at Lake Lowell (a.k.a. Deer Flat Reservoir) southwest of Nampa in Canyon County. The next diversion is for the Ridenbaugh Canal (1878) at Eckert Diversion Dam, immediately above Barber Park, five miles (8 km) from downtown Boise. Wooded through the city, the river is lined by an extensive recreational greenbelt. It flows west across the western end of the Snake River Plain in the Treasure Valley and becomes a braided stream with a wide floodplain as it crosses northern Canyon County to the Snake River. At an approximate elevation of , it