High Lake Ontario Water Levels Foreseeable as Wet Conditions Persist

Published on: 2020/02/14 - in Releases

RELEASE — Lake Ontario is again near record highs for this time of year and the risk of high levels this spring remains elevated. While considerable uncertainty in projections for spring still exists, the International Lake Ontario–St. Lawrence River Board is providing advanced notice so communities can begin planning for a foreseeable Lake Ontario peak of 75.5 m (247.7 feet) or higher in 2020. Please work with your local municipal officials to determine best preparedness and response measures.

The Board continues to deviate from Plan 2014 and maximize outflows as it removes as much water from Lake Ontario as conditions allow to reduce the risk of high water throughout the Lake Ontario-St. Lawrence River system this spring.

All of the other Great Lakes are above record high water levels for this time of year. Despite record outflows in recent weeks, Lake Ontario’s level is only slightly below seasonal record-highs, behind only the levels recorded in mid February during the previous high water years of 1952 and 1973, and at similar levels to those seen at this time in 1978 and 1993. Given the high levels across the Great Lakes basin currently, high waters are a distinct possibility again on Lake Ontario, in the 1000 Islands and along the lower St. Lawrence River in Quebec this spring.

Ice conditions along the St. Lawrence may continue to limit flows over the next few weeks of winter. High outflows will continue to be released to the extent possible in response to the high waters. This action will continue to increase levels in Quebec, and also draw down water levels on Lake St. Lawrence, where extremely low water levels are expected to return. The Board will continue to examine outflow strategies for late spring that may result in further exceptions to the limits for navigation (L Limit) and flooding (F Limit), while weighing the value of these exceptions against the cost of their impacts. All high-outflow strategies that deviate above Plan 2014 flows will depend on future weather events that impact downstream capacity, such as the timing of spring snowmelt and precipitation.

In the meantime, the Board is taking every opportunity to continue to release high outflows to help reduce the risk of high water whenever weather and ice conditions and local inflows to the lower St. Lawrence River permit. This remains a challenging balancing act that the Board’s technical staff are coordinating daily. A total of 28 flow changes proved necessary in January alone. The water level forecasts are adjusted weekly and reflect the probability of continued high water levels on Lake Ontario.

Please note that the Board has recently created a new website page focused on the recent high-water events:. All high-water related materials are now in one place. This was a recommendation in the Province of Ontario’s Special Advisor’s report on flooding.

Information on hydrologic conditions, water levels and outflows, including graphics and photos, are available on the Board’s website and posted to the Board’s Facebook page (English), and more detailed information is available on its website. Please consult your local officials for flood preparedness and response measures.

Release: International Lake Ontario-St. Lawrence River Board
Photo (FEMA): Wikimedia Commons