The Lake Ontario outflows are being adjusted as Ottawa River flows into the St. Lawrence River near Montreal continue to increase, in order to balance high levels upstream on Lake Ontario and the upper St. Lawrence, with those downstream on Lake St. Louis and the lower St. Lawrence.
Lake Ontario outflows will continue to be adjusted on a frequent basis to balance Lake Ontario levels with those downstream in response to dynamic conditions, but it is still expected that water levels on Lake Ontario will rise more than is typical this time of year. How much they will rise will depend on weather conditions in both the Ottawa River and Lake Ontario basins. Another factor contributing to Lake Ontario water levels is the inflow from Lake Erie that continues to be extremely high due to above average water levels on Lake Erie.
A significant storm with heavy rainfall is expected to spread across the basin today. Widespread areas are expected to see 25 to 50 mm (1 to 2 in.) of precipitation and rapidly increasing surface runoff in the Lake Ontario, St. Lawrence and Ottawa River basins.
With heavy and widespread rain forecasted, the Ottawa River is predicted to reach unprecedented outflows, resulting in higher levels in the lower St Lawrence River and temporary reductions in Lake Ontario outflows.
With the heavy rainfall expected within the Lake Ontario basin itself, and likely reduced outflows due to downstream flooding, a significant rise in lake levels is expected. It is worth noting that measured and forecast water level conditions can be subject to a high degree of uncertainty and do not account for local variations due to wind and wave effects.
Until the rain falls, we will not know the extent of the impacts. Public information is available online through the ILOSLRB website: https://ijc.org/en/loslrb and on Facebook: https://www.facebook.com/InternationalLakeOntarioStLawrenceRiverBoard/
*** Emergency response is typically provided through your local municipality ***
Current Conditions can be found here: https://ijc.org/en/loslrb/watershed/current-conditions
Forecasts can be found here: https://ijc.org/en/loslrb/watershed/forecasts