Flood Status

Flood Warning Cancelled
Flood Watch in Effect Along Lake Ontario Shoreline

Flood Potential: High
August 22, 2019  4:00PM                

The Ganaraska Region Conservation Authority advises that water levels on Lake Ontario have been slowly declining since reaching the record peak of 75.92 meters above sea level, which was last observed on June 15th at Cobourg. The level of Lake Ontario has since declined by 43cm and is now at 75.49 masl as of yesterday. The Flood Warning which was first issued on May 13th is therefore downgraded to a Flood Watch to reflect the current conditions.

Lake Erie continues to provide record inflows (via the Niagara River) for this time of year and with all the Great Lakes experiencing high water levels it is expected that Lake Ontario will continue to see above average water levels for the time of year even as they decline.

Recent dry weather is helping to reduce inflows from the surrounding watersheds, while record high outflows are working to gradually bring down the lake levels. So far the lake level has declined by 43cm at Cobourg as of yesterday but it still remains more than 60cm above normal for this time of year. Continued slow declines in water levels are expected for the next several weeks to months as high flows are released into the St. Lawrence River. Outflows will be gradually reduced as the level continues to decline. This will help to reduce water velocities in the St. Lawrence River which have been gradually increasing as the lake level declines.

The International Lake Ontario – St. Lawrence River Board (ILOSLRB) predicts the water level will decline by 4 to 8 cm per week and will fall below 75 masl by October with normal amounts of rainfall. Water levels are still relatively high and winds from a southerly direction will continue to be a concern as wave action may result in shoreline erosion and flooding in low-lying areas especially where streams meet the lake.

Eroding shorelines, submerged beaches, and flooded wetlands on Lake Ontario will continue to be hazardous with potentially unstable banks. Residents are asked to exercise caution around our shorelines and to alert any children in their care of these dangers.

This Flood Watch for the Lake Ontario shoreline will be in effect through Thursday, September 5th, 2019. Conservation Authority staff will continue to monitor conditions, and provide updates as necessary. Should you have any questions or wish to report flooding, please contact the following GRCA staff at 905-885-8173.

Mike Smith
Flood Operations Officer

Note: A Flood Watch is issued as notice that flooding is possible in specific watercourses or municipalities. Municipalities, emergency services and individual landowners in flood-prone areas should prepare.



No flood conditions exist.


Level 1 - Water Safety:

High flows, unsafe banks, melting ice or other factors that could be dangerous for recreational users such as anglers, canoeists, hikers, children, pets, etc. Flooding is not expected.

Level 1 - Flood Outlook:

Early notice of the potential for flooding based on weather forecasts calling for heavy rain, snow melt, high wind or other conditions that could lead to high runoff, cause ice jams, lakeshore flooding or erosion.


Level 2 - Flood Watch:

Flooding is possible in specific watercourses or municipalities. Municipalities, emergency services and individual landowners in flood-prone areas should prepare.


Level 3 - Flood Warning:

Flooding is imminent or already occurring in specific water courses or municipalities.