lake ontario

Cataraqui Conservation is notifying residents and visitors about above average water levels for both Lake Ontario and the Upper St. Lawrence River, which are forecasted to continue to increase in the coming weeks.

The International Lake Ontario – St. Lawrence River Board (ILOSLRB), which manages water levels and outflows from Lake Ontario through the Moses-Saunders Dam in Cornwall, is reporting a Lake Ontario water level of about 75.15 metres IGLD85 (75.11 m GSC), as of April 19. This is about 0.25 metres above average for this time of year and already more than 0.1 metre above a typical summer peak water level, which usually occurs in June.

The ILOSLRB is forecasting that under average conditions, Lake Ontario water levels could exceed 75.3 metres IGLD85 in May (about 0.3 metres above a typical summer peak), prior to a slow decline beginning in June. If there happens to be wetter conditions, this will produce a higher peak. As a point of reference, the 2019 flood year saw Lake Ontario water levels peak at about 75.9 metres.

A higher-than-normal snowpack and wetter conditions so far this year is causing more runoff to all the Great Lakes, contributing to the above average water levels on Lake Ontario and the Upper St. Lawrence River.


Though currently not high enough to warrant issuing flood messaging to alert residents and municipalities about the possibility of widespread flooding, the current and forecasted water levels can increase the risk of localized impacts, especially during wind events with sustained southwest winds which can increase water levels at the east end of Lake Ontario.

Additional Information:

For further information on water levels, wind and wave forecasts, and Provincial flood messages visit

For information directly from the International Lake Ontario – St. Lawrence River Board (ILOSLRB) visit:

Cataraqui Conservation staff will continue to monitor ILOSLRB water level forecasts, Surface Water Monitoring Centre Provincial Statements, local water levels, and update Cataraqui Conservation messaging as needed.

(April 25, 2023)