CORNWALL – Water levels on Lake St. Lawrence will increase temporarily the second weekend of October to assist boaters with removing their craft for the season.
The International Lake Ontario – St. Lawrence River Board announced that it will reduce water outflows from the Moses Saunders and Long Sault Control Dams to bring water levels up.
After the Labour Day long weekend, water levels on the man-made lake continued to drop as the ILOSLR board allowed more water to be drained from Lake Ontario. High water levels from the upper Great Lakes, along with excessive spring run-off conditions caused record flooding on Lake Ontario in 2017 and 2019.
Water levels on that lake are still above seasonal averages. Late last year, the ILOSLR board allowed higher than normal water outflows to be maintained once the shipping season concluded. This drained water from Lake Ontario over the winter months and helped prevent record setting flooding in 2020.
Water flow from the two Cornwall-area dams will be reduced on October 9th, which will raise water on Lake St. Lawrence between 30 and 40 centimetres. Water level changes will be noticed closer to Cornwall, while on the extreme end of the affected area near Prescott there will be a negligible increase.
This will be the last time this season the water levels will increase. After October 11th, water levels will return close to seasonal norms, just above the minimum navigational limit required for the St. Lawrence Seaway to continue operation.
Details were unavailable if the ILOSLR board will deviate from the Plan 2014 water management plan over the winter of 2020-21 to take more water off Lake Ontario.