2026 Kootenay Lake Summer Conditions

The International Kootenay Lake Board of Control (IKLBC) reports that Kootenay Lake levels and Corra Linn operations this spring and summer have complied with the International Joint Commission’s (IJC) 1938 Order of Approval, which sets the maximum lake level through operation of the Corra Linn Dam. Kootenay Lake passed its 2026 freshet peak in early June and lake levels are now on the receding limb of the freshet, declining toward the summer rule curve maximum. 

Kootenay Lake inflows peaked at 86,100 cubic feet per second (1,215 cubic meters per second) on May 28. Inflows have since decreased to 29,000 cfs (821 cms) as of June 29. Outflows from Kootenay Lake peaked at 61,300 cfs (1,736 cms) on June 2 and have since decreased to 35,300 cfs (1000 cms) as of June 29. Both inflows and outflows are forecast to continue decreasing through the summer. 

Kootenai River downstream of Bonners Ferry, ID. Credit: IJC. 

The peak Kootenay Lake water level (the freshet peak) was 1,748.16 feet (532.8 meters) on June 1 (Figure 1). Lake levels have been falling since then. The lake level at Queens Bay is 1745.15 feet (531.9 meters) on June 28. Once Kootenay Lake drops to an elevation of 1,743.32 feet (531.36 meters), as measured at Nelson, British Columbia, this will mark the end of the freshet period for the Kootenay Lake basin. The graph at the bottom of Figure 1 indicated whether Corra Linn Dam or Grohman Narrows has been in control of lake outflows. 

The maximum lake level (the Rule Curve) will then remain at 1,743.32 feet (531.36 meters) at Nelson until September 1, when the Rule Curve maximum rises to 1,745.32 feet (531.97 meters) as measured at the Queens Bay gauge. The maximum lake level will remain at that elevation until January 7, 2027, after which lake draw down is started in preparation for the following year’s snowmelt. 

Information on the IJC 1938 Order of Approval for Kootenay Lake can be found here; the lowering formula is referenced on page 4 in item 2, part 6. 

Please monitor the Board website for further hydrologic updates or sign up for notifications. A follow-up news release detailing observed freshet conditions will be posted in coming months once the freshet peak has been recorded. Real-time Kootenay Lake levels can be found at the FortisBC website. 

Figure 1. 2025/2026 Water Year (October 1 to September 30) Kootenay Lake levels at Queens Bay (green) and Nelson (orange), lake outflow control by Corra Linn (pink) or Grohman Narrows (purple), and the International Joint Commission 1938 Order of Approval Rule Curve for 2026 (red). 

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