Public Consultation: Feedback on Potential Changes to Rainy Lake Rule Curves

The Water Levels Committee (WLC) of the International Rainy-Lake of the Woods Watershed Board (IRLWWB) has employed Temporary Orders for the past three years (2023 to 2025) as approved by the International Joint Commission (IJC). These Temporary Orders allowed the WLC to test the use and functionality of combining the 2018 Standard Rule Curve and High Flood Risk Rule Curve (HFRRC) for Rainy Lake into one large band and renaming the March 10 High Flood Risk Rule Curve decision date, to a date at which the Spring regulation plan will be announced. 

The WLC contracted modeling work to assess the application and impacts of these Temporary Orders under a variety of climate and inflow conditions when compared to the 2018 Order. The work concluded that the Temporary Orders provided more flexibility in spring operations, the risk of flood conditions occurring were similar and the use of the Temporary Orders did not induce significant additional risk of undesirable recreational or environmental impacts. Overall, the additional flexibility in water level target setting under the Temporary Orders was found to be advantageous during all three years they were employed. During the three-year testing period, water level targets for Rainy Lake were established and communicated to the dam operators as usual. 

Following completion of the three-year study, on July 10, 2025, the WLC offered recommendations to the IJC. The Commission invites you to provide comments on this proposal by January 22, 2026, by following this link.

The IJC plans to approve the following, pending results of this public engagement process:

    1) Issuing a new Supplementary Order, amending the 2018 Supplementary Order.

    2) In keeping with the 2023 to 2025 Temporary Orders regarding regulation of Rainy Lake, the new Order replace the March 10th high flood risk determination and announcement, with March 10th being the date by which the WLC will announce its initial spring regulation plan each year.

    3) The revised Order maintain the same standard rule curve for Rainy Lake as was established through extensive study during the last rule curve study ending in 2013. The WLC will oversee the regulation of Rainy Lake to stay within the standard rule curve, with target setting and water level references issued relative to the standard rule curve (i.e. "percent of band” of the standard rule curve).

    4) The HFRRC, as defined in the 2018 Supplementary Order, be maintained, but referred to as the “Spring Buffer Zone”  (Figure 1).

    5) The revised Order changes allow the WLC to use the “Spring Buffer Zone” at any time during the spring, as conditions warrant and as operationally feasible, with IJC approval. When targeting or reporting water levels in the Spring Buffer Zone, reference will be used relative to the bottom of the standard rule curve (e.g., target X cm/in below the rule curve by March 31, etc.).

The IJC believes that the above proposal respects the results and investment that went into the last rule curve study to achieve the best balance of outcomes for the lake, while also achieving an operationally improved version of what was intended to be achieved through the HFRRC. 

The IJC looks forward to hearing your feedback.