After some devastating floods along the Columbia Basin in the 1940's, Canada and The United States began to look into developing a plan for flood control and power supply along the Columbia River and its tributaries. The Columbia River Treaty was an agreement between the United States and Canada that funded the Canadian dams (Mica, Keeleyside, and Duncan) and Montana's Libby Dam, whose reservoir extends into Canada, with U.S. money. The United States gained flood control and power benefits from these storage dams. U.S. President Dwight Eisenhower and Canadian Prime Minister John Diefenbaker signed the treaty on 17 January 1961. The U.S. Senate quickly ratified the treaty but the Canadian Parliament feared that the U.S. had more to gain than did Canadians. They refused to ratify the treaty until the U.S. agreed to purchase excess power generated in British Columbia, power for which the province had no use. The U.S. Northwest treated the power as surplus and sold it to the American Southwest.
The treaty is a coordinated plan that viewed the Columbia River Basin as a transnational system. The storage dams built in Canada meant that downriver users were no longer dependent on seasonal river flows. The storage dams ensure the necessary amount of water will be in the riverbed to meet hydroelectric demands regardless of season within the basin and beyond its borders. In the words of journalist William Dietrich, "No longer were hydropower agencies at the mercy of seasonal flows. Now they could turn the Columbia on and off like a faucet."
Duncan Dam (controlling flow from the north into Kootenay Lake) Completed in 1967, owned and operated by BC Hydro. Duncan is a forty-foot-high earthfill dam that was built to provide storage (it does not have a powerhouse). It was built under the terms of the Columbia River Treaty.