A feasibility study proposes a dam on Lake Koocanusa to effectively manage water levels on the Canadian side of the reservoir. File photo.

A feasibility study proposes a dam on Lake Koocanusa to effectively manage water levels on the Canadian side of the reservoir. File photo.

Feasibility study looks at proposed dam on Lake Koocanusa

The proposal has been raised by local residents concerned with lower reservoir water levels

A proposed new dam on the Canadian side of Lake Koocanusa could cost hundreds of millions of dollars, according to a feasibility study that was done following concerns over water management.

The study, commissioned by the province, identified and facilitated a discussion of a number of issues such as recreation on the lake, flood risk management, analysis of historical water flows and impact to ecosystems that would arise through the construction of a new dam.

Hamish Weatherly, the consultant who completed the study on behalf of the province, told the Regional District of East Kootenay board that a dam stretching across the reservoir and maintaining a water elevation of 2,440 feet would be submerged for four to six months of the year.

“Ideally, that water level would be maintained from mid-May to the end of September,” Weatherly said.

Full pool for Lake Koocanusa is an elevation of 2,459 feet, which is fed into the Libby Dam in the United States.

The issue of a proposed weir — a smaller dam structure — in Lake Koocanusa has been raised by local residents concerned with low reservoir water levels in the summer months, which has impacted recreation and tourism.

“A weir is a very small structure for controlling water levels,” Weatherly said. “What we’re talking about would be many tens of metres, so officially it would be a dam.”

The feasibility study pegged a very preliminary cost estimate at greater than $400 million. Factors that will increase the cost include a navigation lock for boaters, fish passage, site geology constraints, construction accessibility, and the implications of constructing another dam within the context of the Columbia River Treaty, a water sharing agreement between Canada and the United States.

The Treaty, signed in 1964, led to the construction of the Libby Dam in Montana, and three other dams on the Canadian side — the Duncan Dam, Hugh Keenleyside Dam and the Mica Dam.

There has been a growing chorus of concerns from local residents over water levels on the Canadian side of the reservoir in the summer, which fluctuates based on the spring freshet and downstream water flow decisions made by the U.S. Army Corps of Engineers, which operates the Libby Dam.

The Libby Dam is used to generate power for American customers as well as manage water discharge for downstream flood control, while also ensuring enough is being released for endangered fish species.

Water discharge priorities has changed over the last few decades since it finished construction in 1973. Initially, the priority was standard flood control and power generation, however, that was augmented in 1992 to include maintaining in stream flow for downstream fisheries. By 2003, a variable flood control regime was adopted, which kept flood control as the top priority, but gave greater emphasis for downstream fisheries requirements as opposed to power generation.

A dam on the Canadian side of the reservoir would likely impact fish species that move freely in the lake right now, meaning the proposed dam would have to include options for fish passage. Additional impacts include the Libby Dam discharge regime necessary for downstream endangered species.

If the dam proposal has merit for residents or governments, further questions would need to be answered, such as identifying Canadian regulatory hurdles, the ‘owner’ of the dam and who pays for it, and whether the U.S. would agree to it’s construction under the terms of the Columbia River Treaty, which is currently being renegotiated between the two countries.

A public meeting over Zoom will be held by the province Jan. 12, 2021.



trevor.crawley@cranbrooktownsman.com

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