FACT SHEET - Chief Joseph Dam

Published July 6, 2018

­One of a kind dam
Chief Joseph Dam has the nation's longest straight-line powerhouse. At 2,039 feet, it's nearly one half mile long. Chief Joseph Dam is the nation's second leading producer of hydropower and the Corps of Engineers’ largest hydropower producer.

Shaped for power
The dam is 5,962 feet long in an area where the river is only 980 feet wide. The unique "L" shape enabled the Corps of Engineers to extend the powerhouse, providing room for additional generators. This design allows the power plant to take maximum advantage of the river for power production.


Run of the river dam
Chief Joseph Dam is a "run of the river" dam which means the lake behind the dam is not able to store large amounts of water. Water coming to Chief Joseph Dam from Grand Coulee Dam must be passed on to Wells Dam at approximately the same rate. With 27 main generators in the powerhouse, it has the hydraulic capacity of 213,000 cubic feet per second (cfs), or 1,593,000 gallons per second.

In the event more water was passed on to Chief Joseph Dam than could be used for power generation, the spillway gates would be opened to pass the excess water. With an average annual flow rate of 108,000 cfs, the Columbia River seldom exceeds the power plant's capability to pass water. Spilling of water is infrequent at Chief Joseph Dam.



Chief Joseph Dam was authorized as Foster Creek Dam and Powerhouse for hydroelectric power generation and irrigation by the River and Harbor Act of 1946 (H. Doc 693; P.L. 79-525, 79th Cong, 2nd Sess). The River and Harbor Act of 1948 (P.L. 80-858, 80th Cong, 2nd Sess) renamed the project Chief Joseph Dam in honor of the Nez Perce Chief and Statesman who lived his last years on the adjacent Colville Indian Reservation. The reservoir created by Chief Joseph Dam was designated Rufus Woods Lake in 1952 (P.L. 82-469, 82nd Cong, 2nd Sess). Recreation is authorized under the Flood Control Act of 1944 (P.L. 78-534).

Interesting facts about Chief Joseph Dam

  • About 2.2 million cubic yards of reinforced concrete was used to construct Chief Joseph Dam. That's enough concrete to build a two-lane highway between the dam and Salt Lake City, Utah.
  • Chief Joseph Dam has 27 main unit penstocks - one to deliver water to each generator. Each of these penstocks carries enough water to fill an Olympic - size swimming pool in seven seconds.
  • Chief Joseph Dam also has two small penstocks that supply water for two station service generators. The station service generators supply the power used to operate the dam.
  • There are 4.5 miles of galleries (passageways) in the dam.
  • The value of the electricity produced at Chief Joseph Dam is about $450 million annually.
  • Chief Joseph Dam has the nation's longest straight-line powerhouse. At 2039 feet, it's nearly one half mile long.
  • Chief Joseph Dam is the nation's second leading producer of hydropower.

    Hydropower facts
  • Hydropower is more efficient than any other form of electrical generation.  It is capable of converting 90% of available energy into electricity. The best fossil fuel plant is only about 50% efficient.
  • Hydropower is a low cost alternative. On average, hydropower production costs one-third that of nuclear or fossil fuel production.
  • Hydropower can easily respond to power needs. Hydropower dams have the ability to be turned on and off quickly. Other forms of electrical production, such as a coal power, require a great deal of time to start or stop producing electricity.
  • Hydropower is a clean, reusable source of electricity. It produces no emissions and its fuel (water) can be used at each downstream dam.
  • Hydropower is domestic. Our supply of water is continually replenished through rain and snowmelt. We are not dependent upon foreign fuel supplies and their possible interruption.