GRCA Cancels Flood Watch, Issues Watershed Conditions Statement: Flood Outlook for Lake Ontario Shoreline

Flood Potential: Low

The Ganaraska Region Conservation Authority advises that water levels on Lake Ontario have declined steadily since reaching the record peak of 75.92 meters above sea level (masl), which was last observed on June 15th at Cobourg. The level of Lake Ontario has since declined by 57cm and is now at 75.35 masl as of yesterday. The Flood Watch which was issued on August 22nd is therefore downgraded to a Watershed Conditions Statement 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 continue to decline.

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 57cm at Cobourg as of yesterday but it still remains 59cm 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 are being 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 3 to 5 cm per week and will fall below 75 masl by October with normal amounts of rainfall. As water levels are still relatively high compared to normal, winds from a southerly direction may 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. Residents are asked to exercise caution around our shorelines and to alert any children in their care of these dangers.

This Watershed Conditions Statement will be in effect through Friday, September 20th, 2019. Conservation Authority staff will continue to monitor watershed 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                                                                  Cory Harris, P.Eng.
Flood Operations Officer                                           Flood Warning Coordinator

Note: A Watershed Condition Statement for Flood Outlook is issued as 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.