Flood Watch- Lake Ontario
Lower Trent Conservation advises local municipalities and the public that a Flood Watch has been issued for Lake Ontario and Bay of Quinte shoreline from Grafton to Quinte West. Residents along the shoreline should be aware of the potential for erosion and flooding.
Water levels on Lake Ontario have rapidly increased and are expected to continue increasing this week and onwards in response to significant precipitation throughout the Lake Ontario Basin, high inflows for Lake Erie and spring freshet flows from local inputs. Cobourg gauge is currently 75.32 metres IGLD85, which is 0.30 metres above the long-term average for May. Although, Lake Ontario water levels are above average for this time of year, the observed water levels are currently well below the extreme highs of 2017 and 2019.
With the higher than average water level, surge related flooding along the shoreline is possible with high onshore winds as well as increased potential for erosion damages from high waves. Residents should be aware that high onshore winds can result in greater short-term fluctuations of water level. Coastal wetlands may become backwatered and flooding of low lying shorelines is possible as a result.
The International Lake Ontario – St. Lawrence River Board (ILOSLRB), which manages Lake Ontario outflows at the Moses-Saunders Dam in Cornwall and develops water level forecasts, is forecasting that under seasonally normal weather and water supply conditions peak water levels of around 75.46 metres IGLD85 on Lake Ontario would be expected by the end of May. This forecasted peak is well below the 75.88 m reached in 2017 and 75.92 m reached in 2019. Please note that there remains reasonable uncertainty and higher peak levels are possible if wetter than average conditions occur. Publicly available forecasts are updated weekly by ILOSLRB. https://ijc.org/en/loslrb/watershed/forecasts.
Water levels on the Great Lakes naturally vary, responding monthly, seasonally and annually to a variety of factors. Water levels are primarily influenced by natural factors, including precipitation, evaporation, winds, runoff from rivers or streams and inflow from upstream Great Lakes. The Moses-Saunders Dam, approved by the International Joint Commission in the 1950’s, also provides some control over water levels and flows.
Lake Ontario typically reaches its seasonal high water level in May/ June. Residents living along Lake Ontario and the Bay of Quinte should expect further increases in water levels for at least the next month.
Residents should ensure personal property (boats, docks, etc.) along the shoreline is secured. Property owners are also reminded that any work along the shoreline (e.g., place of fill, armour stone, etc.) will require a permit from Lower Trent Conservation and should call the office or visit the website for more information.
Lower Trent Conservation monitors water levels and weather forecasts closely as part of its flood forecasting and warning program. Daily water level updates are available at www.LTC.on.ca. If you have concerns about water levels, please contact Lower Trent Conservation at (613) 394-4829.
This Flood Watch will be in effect until (or updated before) Friday, June 23, 2023.
Manager, Watershed Management, Planning
Or Duty Officer phone (613) 848-4883