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Standard Rule Curve to Be Followed this Spring on Rainy Lake


In accordance with the 2018 Supplementary Order, the Water Levels Committee of the International Rainy-Lake of the Woods Watershed Board has determined that the standard rule curve will be used this spring to direct the operation of the dam at the outlet of Rainy Lake.  Current and forecast conditions, as outlined below, do not support the use of the high flood risk rule curve at this time.

On Tuesday, February 18th the Water Levels Committee hosted a Pre-Spring Engagement Webinar. During this webinar, the Engineering Advisors provided a summary of basin conditions and seasonal forecast information to the Water Levels Committee and the invited representatives of basin interests. Webinar participants were encouraged to provide their own local knowledge and expertise and share any concerns or additional information for consideration in advance of the freshet season. The Water Levels Committee made its decision based on the following information:

Current Conditions

  • Base flow conditions are higher than normal for this time of year.
  • To date, overall average winter temperatures are warmer than 2019, and much warmer than 2014 when significantly high water levels were experienced in the basin.
  • The accumulated snowpack is higher than normal, but lower than 2019 and 2014.
  •  Overall, the past winter has been less severe than average, and less severe than the winters of 2019 and 2014.

Forecasted Conditions

  • Current projections of the El Niño–Southern Oscillation (ENSO) in the Pacific Ocean show a 3% chance of a La Niña condition (cooler than normal Central Pacific Ocean temperature), 77% chance of a Neutral condition, and a 20% chance of an El Niño condition (warmer than normal Central Pacific Ocean temperature).
    • Historic data since 1970 show that high water years occur most often when La Niña conditions are present.
  • Current long-term forecasts of temperature show equal probabilities of low, normal or high temperature through March, April, and May.
  • The current NOAA long-term forecast of precipitation shows a 30% chance above normal precipitation through March, April, and May.


Feedback from basin interests

  • The Rainy Lake Property Owners’ Association stated its support for the use of the standard rule curve for Rainy Lake but asked the WLC to exercise caution due to heavy precipitation in the fall of 2019.
  • Another participant asked that the WLC target the high end of the Rule Curve for May 1st for the benefit of fisheries.

The Water Levels Committee will continue to monitor basin conditions and forecasts as the spring progresses. If conditions change as the year progresses and the risk of flooding changes, the Water Levels Committee may direct the Companies to target specific bands within the standard rule curve for Rainy Lake. For updated information on Water Levels Committee decisions, please visit the Water Level Decisions & Data page of the International Rainy - Lake of the Woods Watershed Board website.