Lake Ontario water levels increase following heavy rainfall, International Board to end outflow deviations


WATERTOWN, N.Y. (WWTI) — The St. Lawrence River Board will end deviations to the Lake Ontario- St. Lawrence River system following recent weather events.

The International Lake Ontario- St. Lawrence River Board announced on Friday that although drought conditions are persisting in the region, recent precipitation has increased Lake Ontario water levels. According to the Board, these water levels have increased by approximately 7 cm, or 2.8 inches.

 “The above average rainfall the first two weeks of July was unexpected but truly benefited the region”, said International Lake Ontario- St. Lawrence River Board United States Co-Chair Steve Durrett. “There is an unpredictable natural supply of water for the Great Lakes and it is important to recognize the full range of high and low water levels that have historically occurred within Lake Ontario.”

Due to this increase, the lake has risen above the low water deviation, Criterion H14, threshold, which is prescribed in the Plan 2014 regulation plan. The Board confirmed its authority to deviate from Plan-prescribed flows expired last week and returned to regulation plan flows on July 17, 2021.

Specifically, this return to regulation plan flows will result in an increase in Lake Ontario outflows. As a result, water levels are expected to decrease on the St. Lawrence River approximately 5.9 to 7.9 inches and rise on Lake St. Louis and at the Port of Montreal, approximately 3.9 to 5.9 inches.

Lake Ontario will increase or decrease depending on natural weather conditions; whether heavy precipitation continues, or drought conditions return.

The Board warned recreational boaters, anglers and other users to be aware of these expected water levels changes. It stated that it will continue to monitor weather forecasts and water supply conditions and re-evaluate the regulation strategy.

Current water level conditions will be posted on the International Lake Ontario- St. Lawrence River Board Facebook page.

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