Low risk of high-water levels for Lake Ontario in next 6 months

Photos by Tom Rivers: The sun sets on Lake Ontario in this photo on Aug. 9 at Lighthouse Christian Camp in Barker.

Press Release, International Lake Ontario-St. Lawrence River Board  

Recent Lake Ontario forecasts indicate that under average water supply conditions, water levels are expected to remain near average through November 2024 and well within the expected range for this time of year.

“Water supply conditions have resulted in one of the longest periods of sustained near long-term average water levels on Lake Ontario,” said General Quander, United States Co-Chair of the International Lake Ontario-St. Lawrence River Board.

Lake Ontario, which has been within (+9 cm/- 15 cm and +3.5 in/- 5.9 in) of the seasonal long-term average since the start of calendar year 2024, is anticipated to continue its gradual seasonal decline through the fall months. The risk of high-water levels remains low for the six-month forecast period.

In consideration of the current and projected conditions, the International Lake Ontario-St. Lawrence River Board plans to use its minor deviation authority to deviate from Regulation Plan 2014 through October 18, 2024.

This minor deviation is expected to provide more predictable water levels on Lake St. Lawrence and the upper St. Lawrence River for recreational navigation, while having minimal impacts on other interests throughout the system. The Board also plans to use its minor deviation authority to conduct a temporary flow reduction in early September to facilitate in-water inspections of Hydro-Quebec facilities.

Regulation Plan 2014 is the set of rules that govern Lake Ontario outflows, which influence water levels across the Lake Ontario-St. Lawrence River system. A rule within Plan 2014 known as the “September Rule” prescribes flow increases through the Moses-Saunders Dam if the water level of Lake Ontario measures above 74.8 m (245.4 ft.) at the beginning of September.

This photo from Aug. 9 shows the sunset from the shore in Barker.

Increased Lake Ontario outflows cause water levels of Lake St. Lawrence, immediately upstream of the Moses-Saunders Dam, to decrease. This reduction in Lake St. Lawrence water levels could negatively impact the recreational boating community in the final weeks of the season.

Therefore, the Board will use its authority to deviate from Plan 2014 and adjust flows through October 18, 2024, to target a minimum weekly mean water level of Lake St. Lawrence of 73.1 m (239.8 ft).  The Board cautions that levels may drop below this minimum target for periods during the week if strong easterly winds occur. As required by the Directive, the Board plans to fully offset the impacts of the deviation by increasing flows starting on October 19, 2024.

“As water levels throughout the system continue their gradual seasonal decline, the Board encourages recreational boaters to monitor the water level forecasts to determine the optimal time to remove their vessels and equipment for the season”, said Dr. Wayne Jenkinson, Alternate Canadian Co-Chair of the International Lake Ontario-St. Lawrence River Board.