Update on Kootenay Lake Water Levels and Conditions
Date

The International Kootenay Lake Board of Control is reporting that Kootenay Lake levels remain in compliance with the International Joint Commission’s (IJC) 1938 Order of Approval which sets the limit for maximum lake levels.

Currently, Kootenay Lake is experiencing low inflows and lake levels due to above average temperatures and below average precipitation in the basin. Lake outflows are controlled by the Corra Linn Dam or by the natural constriction of the lake at Grohman Narrows.

Kootenay Lake inflows peaked at 73,700 cubic feet per second (2,087 cubic meters per second) on May 30 and have decreased through the late spring and early summer, reaching current, near-historic low flows. To allow farmers to work in their fields along the Kootenai River, the 1938 Order specifies that once the lake elevation falls below 1743.32ft (531.36 meters), as measured at the Nelson gauge, it should be held below this elevation until August 31. On July 2, Kootenay Lake at Nelson dropped below 1743.32 feet (531.36 meters) and the lake level will remain below this elevation until the end of August. Starting September 1, the Rule Curve for Kootenay Lake level will increase to 1,745.32 feet (531.97 meters) as measured at the Queens Bay gauge for compliance measurements.

Kootenay Lake Level July 2025

Figure 1. 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 2025 (red). Credit: FortisBC (data) and Environment and Climate Change Canada (plot), 2025.

During a six-week period starting in late April 2025, temperatures in the Kootenay Lake Basin were almost exclusively well above the long-term mean (Figure 2) and precipitation has been below the long-term mean (Figure 3). Snow in the basin began melting earlier than the median and fully melted earlier.

 

Daily Mean Temperature Nelson, BC

 

Figure 2. Nelson, BC daily mean temperatures for the past 3 months (black), long-term mean (dashed grey), standard deviations above and below the mean (red, and blue respectively).

 

Daily Precipitation Nelson, BC

Figure 3. Nelson, BC daily cumulative observed precipitation for the past 3 months (black) long-term mean (dashed grey).

 

Quick Facts

  • The International Kootenay Lake Board of Control is responsible for overseeing that FortisBC operate Corra Linn Dam, such that Kootenay Lake levels are in compliance with the International Joint Commission 1938 Order of Approval Rule Curve. 
  • The Kootenay Lake Visualization Tool is available to the public to better understand the complexities, competing interests, and physical limitations in the management of Kootenay Lake’s water levels.   
  • This year’s board and public meetings were held on May 7, 2025 in Nelson, BC. A recording of the public meeting is available here. 
  • Real-time hydrologic conditions for the Kootenay (Kootenai) basin can be found at the Canada Water Office website and the US Geological Survey WaterWatch website, with additional information found on the  Fortis BC dam operators website.
  • You may contact the board through the Contact form on its website. 
  • Stay in touch and subscribe to receive email news updates from the Kootenay Board. 

 

Contacts 

Sonja Michelsen, US Secretary 

Martin Suchy, Canadian Secretary 

International Kootenay Lake Board of Control