The Boise River is a 102mi 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 4100sqmi of highly diverse habitats, including alpine canyons, forest, rangeland, agricultural lands, and urban areas.DescriptionThe Boise River rises in three separate forks in the Sawtooth Range at elevations exceeding 10000ft, 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, 60mi 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.
