Aerial view Libby dam, upstream view, 1986
|Location||Lincoln County, Montana|
|Dam and spillways|
|Type of dam||Concrete gravity|
|Height||422 ft (129 m)|
|Length||3,055 ft (931 m)|
|Spillway capacity||160,000 cu ft/s (4,500 m3/s)|
|Total capacity||6,027,000 acre·ft (7.434 km3)|
|Catchment area||8,985 sq mi (23,270 km2)|
|Surface area||46,700 acres (18,900 ha)|
|Installed capacity||600 MW|
|Annual generation||1,574.4 GWh|
Dedicated on August 24, 1975, Libby Dam spans the Kootenai River 17 miles (27 km) upstream from the town of Libby, Montana. Libby Dam is 422 feet (129 m) tall and 3,055 feet (931 m) long. The reservoir behind the dam is Lake Koocanusa; it extends 90 miles (140 km) upriver from the dam and has a maximum depth of about 370 feet (110 m) . Forty-two miles (68 km) of Lake Koocanusa are in British Columbia, Canada. Lake Koocanusa was named for the treaty that was developed between the Kootenai Indians, the Canadian government, and the U.S. government to build the Dam and form the reservoir. It is the fourth dam constructed under the Columbia River Treaty. The Kootenai River is the third largest tributary to the Columbia river, contributing almost 20% of the total water in the lower Columbia. Libby Dam holds back an average of 5,800,000 acre feet (7.2 km3) of water.
The dam is operated by the United States Army Corps of Engineers. At full capacity, the dam can pass over 160,000 cubic feet per second (4,500 m3/s) of water. The dam is designed with a selective withdrawal system that allows water passage from various levels of Lake Koocanusa. This allows the dam operators to moderate water temperatures downstream. The river continues past Bonners Ferry, Idaho to Kootenay Lake and joins the Columbia River.
Libby Dam's powerhouse contains five turbines and is capable of generating 600 megawatts. The electricity is managed by the Bonneville Power Administration and services eight states: Montana, Idaho, Washington, Wyoming, California, Utah, Oregon and Nevada. The money earned from electricity sales goes to the United States Treasury to repay the cost of building and operating Libby Dam.