Increasing Water Levels Throughout the Lake Ontario-St. Lawrence River System due to Persistent Precipitation
Heavy rain in recent days across the Lake Ontario-St. Lawrence River basin has led to rapid increases in Ottawa River flows and rising Lake Ontario water levels. Lake Ontario levels have been rising at a rate of approximately 2 cm per day and are expected to reach 75.30 m (247.05 ft) today while levels of the St. Lawrence River at Pointe-Claire (Montreal) have risen above 22.20 m. (72.83 ft) Continued wet weather and runoff from the recent rains may result in flooding of vulnerable areas along the Lake Ontario shoreline as well as downstream along the St. Lawrence River, including Lake St. Louis and Lake St. Pierre.
At this time, the water levels of Lake Ontario and St. Lawrence River are expected to remain below the record-highs observed in 2017 and 2019.
The International Lake Ontario-St. Lawrence River Board is monitoring the situation. The Lake Ontario outflow into the St. Lawrence River continues to be adjusted in accordance with the Plan 2014 F limit.
Ontario Power Generation adjusted the gates at the Iroquois Dam this morning to prevent extremely high levels on Lake St. Lawrence. Lake St. Lawrence is the portion of the St. Lawrence River upstream from the Moses - Saunders dam to Iroquois, ON. This action does not change the outflow from Lake Ontario nor water levels elsewhere on the system.
An update will be provided on Thursday.
For more information on:
- Lake Ontario Outflow Changes: https://ijc.org/en/loslrb/watershed/outflow-changes
- Plan 2014 F limit: https://ijc.org/en/loslrb/watershed/faq/4#4-8-2
- Ottawa River Outflows: https://ottawariver.ca/
The International Lake Ontario-St. Lawrence River Board ensures that outflows from Lake Ontario meet the requirements of the International Joint Commission's Orders of Approval. Under any regulation plan, the ability to regulate the outflow from Lake Ontario does not mean that full control of lake levels is possible. This is because the major factors affecting water supply to the Great Lakes, precipitation, evaporation, and runoff cannot be controlled, and are difficult to accurately predict.