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Kootenay Lake levels

FortisBC generates hydroelectric power at four dams on the Kootenay River. Vital to these operations is the level of Kootenay Lake, which is governed by the 1938 International Joint Commission (IJC) order on Kootenay Lake, held by FortisBC.

Notification for large & unusual changes

Kootenay Lake water levels fluctuate. When we anticipate a significant or rapid fluctuation of the lake level, we will make every effort to inform customers who’ve asked to be notified, by email and/or automated call-out technology. 


Call us, toll free: 1-866-436-7847 (7am to 7pm, Monday - Friday)


Of FortisBC’s four facilities on the Kootenay River, Corra Linn dam is the closest to Kootenay Lake and can operate as the control point for water flows out of Kootenay Lake.  However, just upstream from Corra Linn is Grohman Narrows, which creates a physical restriction of water flowing out of Kootenay Lake during certain times of the year, especially during the high spring runoff period.

Kootenay Lake is subject to large natural inflows of water. Additionally, there are two dams upstream that play a key role in Kootenay Lake levels – Duncan Dam operated by BC Hydro and the Libby Dam operated by the U.S. Army Corps of Engineers. It is estimated that without the Libby and Duncan dams in place today, annual peak lake levels would be 6 to 10 feet higher than currently observed. 

The Kootenay Lake level is governed by the 1938 order from the IJC. This bi-national body administers the Boundary Water Treaty of 1909, between Canada and the United States. The treaty provides the regulatory principles, and mechanism to prevent and resolve disputes concerning waters that flow along or across the border.

IJC Members (three appointed by each country, and assisted by advisors and staff in Ottawa and Washington DC) issue orders of approval, in response to applications for the use, diversion, or obstruction of these waters.

Among these, the Order for Storage in Kootenay Lake provides the parameters for the elevations of Kootenay Lake through-out the year.

Annual Kootenay Lake Operations

September 1 - January 7:
The maximum geodetic elevation is 1745.32 feet.

January 7 - January 31:
The elevation gradually declines to a maximum of 1744.00 feet.

January 31 - February 28:
The elevation gradually declines to a maximum of 1742.40 feet.

February 28 - March 31:
The elevation gradually drops to a maximum of 1739.32 feet.

March 31 -
Rise in lake endeavor to keep the level below 1739.32 feet. 

In the period after March 31, when the elevation is forced above 1739.32 ft., the lake levels will rise and fall based on a calculated maximum allowable elevation. This maximum is based on actual lake inflow, calculated lake elevation given original discharge conditions prior to the excavation of Grohman Narrows, and a certain lowering below the calculated lake elevation.

Once the flood peak is passed and the lake levels recede to an elevation of 1743.32 feet at Nelson, the control becomes an upper elevation of 1743.32 feet at Nelson until September 1.

During the high summer runoff, the restriction of getting water out of Kootenay Lake is the Grohman Narrows between Nelson and the Corra Linn Dam. While the Corra Linn Dam can restrict water flow from Kootenay Lake, the number of gates opened or closed during this time is not an indication that the flow is being restricted. The practice at Corra Linn during this time is to open enough gates so that Grohman Narrows is the restriction. 


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