The Bitterroot River is named for the bitterroot plantLewisia rediviva, whose fleshy taproot was an important food source for Native Americans. The Salish called the riverSpet-lum for "Place of the bitterroot" and In-shi-ttogh-tae-tkhu for "Willow River". French trappers knew the plant as racine amère. The early Jesuit priest, Father De Smet, named it St. Mary's River. By the time of Washington Territory surveys by Governor Isaac I. Stevens in 1853, the name had been translated to Bitterroot River.
Watershed
The Bitterroot River watershed drains in Ravalli and Missoula counties. The Bitterroot Valley averages 7–10 miles wide and is uniquely low gradient for western Montana streams. The river mainstem begins at the confluence of the East Fork Bitterroot River and the West Fork Bitterroot River. From there the mainstem receives numerous tributaries from the Bitterroot Mountains to the west and the Sapphire Mountains to the east. The watershed is a snowmelt dominated system with large interannual variations in streamflow and peak flows from mid-May to mid-June. The variation is compounded by extensive irrigation withdrawals and upstream reservoir storage at Painted Rocks Reservoir on the West Fork Bitterroot River with the most severely dewatered reaches along of the river located between Woodside Crossing near Corvallis and Bell Crossing near Stevensville. Major tributaries include Skalkaho Creek, and Lolo Creek. The Skalkaho Creek drainage subwatershed originates in the Sapphire Mountains and drains and flows west-northwest to it confluence with the Bitterroot River. Lolo Creek is the primary tributary in the northern portion of the Bitterroot watershed. Lolo Creek is often completely dewatered in late summer in its lower due to withdrawals for irrigation and rural water use.
Habitat and wildlife
Although the Bitterroot River passes close by to many residential areas, it is an excellent place for wildlife viewing. Many species of ducks and waterfowl are common along with osprey, bald eagles and heron. Elk, moose, and both white-tailed deer and mule deer frequent the river as a source of water and to graze near its banks. The most notable wildlife viewing locale along the river is the famous Lee Metcalf National Wildlife Refuge, named for U.S. Senator Lee Metcalf, a pioneer of the conservation movement. A renowned fly fishing stream, the Bitterroot River mainstem and many of its tributaries are important migratory corridors and spawning habitat for native westslope cutthroat trout and bull trout. Other native fish include mountain whitefish, longnose sucker, slimy sculpin, and longnose dace. Rainbow trout and brown trout are popular gamefish but are not native to the Bitterroot River watershed and pose significant threats to native trout. In Montana, rainbow trout are only native to the upper Kootenai River in the state's extreme northwest corner. Non-native rainbow trout pose one of the greatest threats to cutthroat trout by hybridization, producing "cutbows". In addition, non-native brook trout often displace native cutthroat trout and bull trout in small streams.
Recreation
The towns along the Bitterroot River, including Hamilton, Stevensville, Missoula, and are popular destinations for fly fishing, with rainbow trout being fairly prevalent and with smaller populations of brown trout and westslope cutthroat trout. The Bitterroot is a Class I river from the confluence of the East and West forks to its confluence with the Clark Fork River for public access for recreational purposes.
