Boise River, ID

The Boise River is a tributary of the Snake River, approximately 75 miles (121 km) long, 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 4,100 square miles (11,000 km2) of highly diverse habitats, including alpine canyons, forest, rangeland, agricultural lands, and urban areas.

The Boise River rises in three separate forks in the Sawtooth Range at elevations exceeding 10,000 feet (3048 m), and is formed by the confluence of its North and Middle forks. The North Fork, 50 miles (80 km) long, rises in the Sawtooth Wilderness Area, along the Boise-Elmore county line, 60 miles (100 km) northeast of Boise. It flows generally southeast through the remote mountains in the Boise National Forest. The Middle Fork, approximately 70 miles (110 km) in length rises, within 20 miles (32 km) of the North Fork in the southern Sawtooth Wilderness Area in northeastern Elmore County. It flows WSW near the town of Atlanta, joining the North Fork to form the Boise River, approximately 15 miles (25 km) southeast of Idaho City. The main stream flows southwest into Arrowrock Reservoir joining the South Fork from the Anderson Ranch Dam.

The South Fork (100 miles, 160 km) rises in northern Camas County in the Smoky Mountains of the Sawtooth National Forest north of Fairfield, 60 miles (100 km) 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, 20 miles (32 km) east of Boise.

Downstream from its confluence with the South Fork, the river flows generally west, and adds the major tributary of Mores Creek along Highway 21, and passes through Lucky Peak Reservoir 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. As the river passes through downtown Boise, it is lined by an extensive recreational greenbelt. The Boise River then flows west across the western end of the Snake River Plain, it becomes a braided stream with a wide floodplain as it crosses northern Canyon County to the Snake River. It enters the Snake River, the Idaho-Oregon border, west of Parma and three miles (5 km) south of Nyssa, Oregon.

The Boise river is also used for fishing, mostly for rainbow trout and, in the winter, steelhead. Spinfishermen use roostertail spinners and bait such as worms and powerbait while fly fishermen use a variety of nymphs, streamers, and dry flies.