Moses-Saunders Dam

High water levels foreseeable as wet conditions persist


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 at (English), and more detailed information is available on its website at Please consult your local officials for flood preparedness and response measures.



Rob Caldwell:              (613) 938-5864                          

Susie Blair:                  (716) 879-4410                          

The International Lake Ontario – St. Lawrence River Board specifies the outflows from Lake Ontario, according to Plan 2014 as required in the 2016 Supplementary Order from the International Joint Commission. This plan was agreed to by the United States and Canada in December 2016 in an effort to improve environmental performance while maintaining most of the benefits provided to other interests by the previous Plan 1958-D, which was in use since 1963. In determining outflows, the Board, in conjunction with its staff, pays close attention to water levels in the Lake Ontario-St. Lawrence River system and on the Great Lakes upstream, and to the effects on stakeholders within the basin.

Water levels vary from year-to-year and throughout the year depending on weather and water supply conditions. Such variations benefit coastal wetlands and are critical to a healthy lake environment, but may at times and depending on individual circumstances increase the vulnerability of shoreline structures and reduce opportunities for recreational boating activities. The Board urges everyone to be prepared to live within the full range of levels that have occurred in the past and of those that may occur in the future. Based on historical observations and projected future conditions, at a minimum, Lake Ontario water levels are expected to range from a high of 75.92 m (249.1 ft.) to a low of 73.56 m (241.3 ft.) at infrequent intervals.  However, it is also recognized that future climate conditions are uncertain, and more extreme water levels may be reached and these extremes may occur more often.  Levels on the St. Lawrence River tend to vary more widely than on Lake Ontario. Also, these levels do not include the varying local effects of strong winds and wave action that significantly increase or decrease local water levels on both the lake and river, with temporary changes of over half a meter (two feet) possible in some locations.

For more information, please see the Board’s website ( and Facebook page ( receive a weekly email about water levels and flows in the Lake Ontario–St. Lawrence River system, please send a blank e-mail message to with the word ’subscribe’ in the title and body of your message.