Little Blackfoot River
| Little Blackfoot River | |
_-_Powell_County,_Montana.png) The Little Blackfoot River Bridge at Avon, Montana.
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| Country | United States |
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| State | Montana |
| County | Powell County |
| Source | |
| - location | West side of the Continental Divide in southeastern Powell County, Montana |
| - elevation | 7,476.5 ft (2,279 m) |
| - coordinates | 46°21′46″N 112°29′31″W / 46.36278°N 112.49194°W |
| Mouth | Clark Fork River |
| - location | Powell County, Montana |
| - elevation | 4,243 ft (1,293 m) |
| - coordinates | 46°21′46″N 112°29′31″W / 46.36278°N 112.49194°WCoordinates: 46°21′46″N 112°29′31″W / 46.36278°N 112.49194°W |
| Length | 48 mi (77 km) |
| Basin | 413 sq mi (1,070 km2) |
  Location of the headwaters of the Little Blackfoot River in Powell County, Montana
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The Little Blackfoot River is a 48-mile (77 km) long tributary of the Clark Fork River, located in Powell County, Montana in the state of Montana in the United States.
The Little Blackfoot River is located in Powell County, Montana. The river is 48-mile (77 km) long, and its watershed covers 413 square miles (1,070 km2). Its name refers to the Piegan Blackfeet tribe, which frequently visited the area. The first mention of the name was an 1831 entry in a diary kept by John Work, trader for the Hudson's Bay Company. Work implies that the name did not originate with him, but with American fur trappers who had been using the area extensively to hunt beaver for the previous two decades.
The river begins near the top of the west side of the Continental Divide, near Thunderbolt Mountain in the Boulder Mountains. The course of the upper of the Little Blackfoot river (above Dog Creek) was established some time before the start of the Wisconsin glaciation (approximately 85,000 years ago) when a glacier on Thunderbolt Mountain deepened the valley floor. This glacier was about 24 to 25 miles (39 to 40 km) long. The river then deepened its valley by about 250 feet (76 m) before another glacier about 20 miles (32 km) long again covered the valley during the Wisconsin glaciation (85,000 to 11,000 years ago).
The river discharges into the Clark Fork River near Garrison, Montana. For about three-fourths of its length, the river flows through densely forested mountain terrain. Another 15 to 20 percent of the watershed consists of open mountain valleys while about 5 percent of the watershed is irrigated ranchland. Just over half the land in the watershed is privately owned.
Precipitation in the Little Blackfoot River watershed varies widely, from 10 to 20 inches (25 to 51 cm) in the valleys to 30 to 50 inches (76 to 127 cm) in the mountains. Water flow in the river also varies considerably, with a peak in May due to snowmelt and heavy spring rains. Lowest flows are recorded in September. The average annual peak discharge over the past 33 years (the period during which records have been kept) was 1,505 cubic feet (42.6 m3) per second, while the average annual discharge was approximately 155 cubic feet (4.4 m3) per second. Three small reservoirs—on Snowshoe Creek, Spotted Dog Creek, and Threemile Creek (Quigley Reservoir)—impeded tributary flows to the Little Blackfoot River. Releases from these reservoirs generally only occur to meet irrigation needs during periods of low stream flow.
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