Water Levels Reported Above Normal on Lake Ontario, Upper St. Lawrence River

Published on: 2023/04/25 - in News

Residents and visitors to Lake Ontario and the Upper St. Lawrence River are being warned of above-average water levels that are expected to continue to increase in the coming weeks. Cataraqui Conservation has issued a notification about this situation.

According to 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, Lake Ontario’s water level was at about 75.15 metres IGLD85 (75.11 m GSC) as of April 19. This is 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’s 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. However, if there happens to be wetter conditions, this will produce a higher peak. It is important to note that the 2019 flood year saw Lake Ontario water levels peak at about 75.9 metres.

The above-average water levels are attributed to a higher-than-normal snowpack and wetter conditions so far this year, causing more runoff to all the Great Lakes.

The current water levels do not warrant issuing flood messaging to alert residents and municipalities about the possibility of widespread flooding, although the risks of localized impacts are increased, especially during wind events with sustained southwest winds, which can increase water levels at the east end of Lake Ontario.

For more information on water levels, wind and wave forecasts, and Provincial flood messages, visit the Cataraqui Conservation’s Flood page.

Photo: Wikimedia Commons (pd)