Clark Fork (river)

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Clark Fork
Clark Fork, Missoula, Montana
Country	United States
States	Montana, Idaho
Major cities	Butte, Missoula
Length	310 mi (499 km) [1]
Watershed	22,905 sq mi (59,324 km²) [2]
Discharge at	Whitehorse Rapids near Cabinet, ID
- average	21,930 cu ft/s (621 m³/s) [3]
- maximum	153,000 cu ft/s (4,332 m³/s)
- minimum	762 cu ft/s (22 m³/s)
Primary source	Silver Bow Creek
- location	Butte, Silver Bow County, Montana
- coordinates	46°4′32″N 112°27′56″W / 46.07556, -112.46556 [4]
- elevation	6,882 ft (2,098 m) [5]
- length	20 mi (32 km)
Other source	Warm Springs Creek
- location	Flint Creek Range, Granite County, Montana
- coordinates	46°15′39″N 113°8′12″W / 46.26083, -113.13667 [6]
- elevation	7,466 ft (2,276 m) [7]
Source confluence
- location	Deer Lodge County, Montana
- coordinates	46°11′12″N 112°46′18″W / 46.18667, -112.77167 [1]
- elevation	4,795 ft (1,462 m) [8]
Mouth	Lake Pend Oreille
- location	Bonner County, Idaho
- coordinates	48°11′0″N 116°16′9″W / 48.18333, -116.26917 [1]
- elevation	2,064 ft (629 m) [9]
Major tributaries
- left	Bitterroot River
- right	Blackfoot River, Flathead River
Map of the Clark Fork, its main tributaries and downriver connection to the Columbia River via the Pend Oreille River.
Map of Montana rivers with Clark Fork in the west.

The Clark Fork is a river in the U.S. states of Montana and Idaho, approximately 360 mi (579 km) long. The largest river by volume in Montana, it drains an extensive region of the Rocky Mountains in western Montana and northern Idaho in the watershed of the Columbia River, flowing northwest through a long mountain valley and emptying into Lake Pend Oreille in northern Idaho. The Pend Oreille River, which drains the lake to the Columbia, is sometimes included as part of the Clark Fork, giving it a total length of 479 mi (771 km), with a drainage area of 25,820 sq mi (66,870 km²). In its upper 20 mi (32 km) in Montana near Butte, it is known as Silver Bow Creek. Interstate 90 follows much of the upper course of the river from Butte to northwest of Missoula.

The Clark Fork should not be confused with the Clarks Fork of the Yellowstone River, which is located in Montana and Wyoming.

[edit] Description

It rises as Silver Bow Creek in southwestern Montana, less than 5 mi (8 km) from the continental divide near downtown Butte, from the confluence of Basin and Blacktail creeks. It flows northwest and north through a valley in the mountains, passing east of Anaconda, where it changes its name to the Clark Fork, then northwest to Deer Lodge. From Deer Lodge it flows generally northwest across western Montana, passing south of the Garnet Range toward Missoula. Five miles east of Missoula, the river receives the Blackfoot River.

Northwest of Missoula, the river continues through a long valley along the northeast flank of the Bitterroot Range, through the Lolo National Forest. It receives the Bitterroot River from the south-southwest approximately 5 1/2mi west of downtown Missoula, and receives the Flathead River from the north near Paradise. It receives the Thompson River from the west near Thompson Falls in southern Sanders County.

At Noxon, Montana, along the north end of the Bitterroots near the Idaho border, the river is impounded by the Noxon Rapids Dam to form a 20 mi (32 km) long reservoir. It crosses into western Bonner County in northern Idaho near the town of Cabinet, Idaho. Approximately 5 mi (8 km) west of the Idaho-Montana state line, the river enters the eastern end of Lake Pend Oreille, near the town of Clark Fork.

[edit] History

During the last ice age, from approximately 20,000 years ago, the Clark Fork Valley lay along the southern edge of the Cordilleran ice sheet covering western North America. The encroachment of the ice sheet formed an ice dam on the river, creating Glacial Lake Missoula which stretched through the Clark Fork Valley across central Montana. The periodic rupturing and rebuilding of the ice dam released the Missoula Floods, a series of catastrophic floods down the Clark Fork and Pend Oreille into the Columbia which sculptured many of the geographic features of eastern Washington and the Willamette Valley of Oregon.

In the 19th century the Clark Fork Valley was inhabited by the Flathead tribe of Native Americans. It was explored by Meriwether Lewis of the Lewis and Clark Expedition during the 1806 return trip from the Pacific. The river is named for William Clark. A middle segment of the river in Montana was formerly known as the Missoula River.

Since the late 19th century many areas in the watershed of the river have been extensively mined for minerals, resulting in an ongoing stream pollution problem. Most pollution has come from the copper mines in Butte and the smelter in Anaconda. Many of the most polluted areas have been designated as Superfund sites. Nevertheless the river and its tributaries are among the most popular destinations for fly fishing in the United States.

Today, the Clark Fork watershed encompasses the largest Superfund site in America. As a mega-site, it includes three major sites: Butte, Anaconda, and Milltown Dam/Clark Fork River. Each of these major sites is split up into numerouse sub-sites known as Operable Units. Remediation and/or restoration of these sites is ongoing.

[edit] See also

• Clarks Fork Yellowstone River
• List of Idaho rivers
• List of Montana rivers
• George F. Grant
• Butte, Montana

[edit] References

[edit] External links

• Clark Fork Watershed Education Program
• EcoRover, a blog about Superfund and other environmental issues in the upper Clark Fork River basin
• Clark Fork Coalition
• Upper Clark Fork Restoration Program
• Environmental Protection Agency (EPA), Region 8, Butte/Silver Bow Creek
• EPA, Region 8, East Anaconda/Old Works
• EPA, Region 8, Milltown Dam
• Clark Fork River Technical Assistance Committee