Libby Dam

Libby Dam is a dam on the Kootenai River in the U.S. state of Montana.

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. Lake Koocanusa is the name of the reservoir behind the dam; 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 consulting architect for the project was Seattle architect Paul Thiry, and the commission for its large granite bas-relief was awarded to sculptor Albert Wein by competition.

In order to make way for the dam, the town of Rexford, Montana was relocated and the Flathead Railroad Tunnel was dug.

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.