The International Lake Ontario – St. Lawrence Board is optimistic that weather conditions the rest of this winter and spring won’t cause a damaging rise in Lake Ontario levels this year. However, it has been acting proactively since January 1 to reduce lake levels this winter just in case the weather turns wet.
Somewhat drier weather conditions over the past several months coupled with favorable river ice conditions and continued high outflows from Lake Ontario have caused a decline in the lake’s level, such that it is now a few centimeters below the seasonal long-term average. Under the board’s current deviation strategy, outflows from Lake Ontario have been maximized and set above some Plan 2014 prescribed limits, resulting in the removal of an additional 3.1 inches of water from Lake Ontario when compared to strict adherence to Plan 2014 rules. The board intends to continue this strategy through February 28.
The International Joint Commission (IJC) recently approved the board’s request for continued authority to deviate from Plan 2014, if necessary, until Lake Ontario reaches its peak level this spring. The previous deviation authority granted to the board is set to expire on February 28. The extended authority recently granted the board would only be applied should conditions worsen after March 1. This authority, if implemented, would allow for outflows from the Moses-Saunders dam on the St. Lawrence River may be increased to exceed Plan 2014 flows.
The risk of high water on Lake Ontario in 2021 remains a moderate possibility, but less likely than the risk was last spring at this time. While water levels on Lake Erie and the upper Great Lakes are all lower than a year ago, they are still very high. This will cause inflows to Lake Ontario from Lake Erie to remain high over the coming months. These expected high inflows, coupled with uncertain seasonal factors such as precipitation and snowpack runoff, cause a moderate risk of a high-water event in the Lake Ontario basin this spring.
The board and IJC recognize the threats posed by continued high inflows from Lake Erie into the system and the risk of another high-water event on Lake Ontario and the St. Lawrence River in 2021. Given that conditions can rapidly change in the spring months, the board sought extended deviation authority to allow it to react as quickly as possible with deviations from Plan flows should conditions worsen.
Basin conditions will be frequently assessed by the board and appropriate deviations applied should conditions worsen. This will help reduce the risk of high-water levels this spring in balance with the interests of other groups throughout the system. Given the lower risk of reaching flood levels on Lake Ontario this spring as compared to last year at this time, the board does not expect its deviation strategies would interrupt or negatively impact commercial navigation in the St. Lawrence Seaway.
The board emphasizes that, if basin conditions should become extremely wet, similar to those observed in 2017 and 2019, no deviation strategy will prevent water levels that can cause flooding and damage to shoreline properties. Eliminating such damages is beyond the reach of outflow regulation and are more reliably addressed through coastal resilience and planning.
Information on hydrologic conditions, water levels, and outflows, including graphics and photos, are posted to the board’s Facebook page and more detailed information is available on its website at https://www.ijc.org/en/loslrb.
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