Moses-Saunders Dam

Record Outflows Continue Through February; Maximized outflows in March


The International Lake Ontario–St. Lawrence River Board agreed on February 21 to continue deviating from Plan 2014 and maximize outflows through the spring.

As was the case in January, outflow for the month of February is expected to set a new record. Without the record outflows employed since the beginning of the year, water levels would be even higher than they are currently.

Because the risk of a high water event on Lake Ontario remains elevated, the Board agreed to continue maximizing flows through March 31. The Seaways Corporations have announced the date of April 1 for the opening of the 2020 navigation season for the Montreal to Lake Ontario section of the seaway. The April 1 opening allows for outflows to continue in excess of prescribed safe limits for navigation through the end of March.

The Board’s outflow strategy for April will be determined at a later date based on conditions upstream and downstream at the time and in consideration of all interests.  

The Board also considered ice conditions in the St. Lawrence River, and the effects of high outflows on lower St. Lawrence River water levels in order to continue maximizing outflows from Lake Ontario as much as possible.

Ice cover on the St. Lawrence River has been below normal throughout the winter, and mild weather over the past several weeks continued to provide favorable conditions to release exceptionally high outflows from Lake Ontario. 

Nonetheless, with high levels of Lake Ontario and the upper Great Lakes continuing, the risk of high water this spring remains elevated. Therefore, the Board will continue releasing high outflows in the coming weeks by maximizing outflows up to the higher tiers of the Plan’s limit intended to balance upstream and downstream high water impacts known as the F Limit.

Based on past experience and information, the Board assessed that there will be a low risk of impacts along Lake St. Louis when the lowest level of the F Limit at 22.10 m (72.5 ft) is passed. The Board agreed to surpass the lowest tier of the F Limit without reducing Lake Ontario outflows, in an effort to remove additional water from Lake Ontario this winter and spring. The second tier of the F Limit, which limits outflows when Lake St. Louis reaches 22.20 m (72.8 ft) while Lake Ontario levels are below 75.37 m (247.28 ft), will still be maintained.

Residents along the St. Lawrence River should be aware that water levels could fluctuate significantly over the coming weeks.

These deviation strategies will help remove a small amount of additional water from Lake Ontario in the coming weeks.  Given the current record high water levels for this time of year on the other Great Lakes, these actions will help reduce the risk of levels on Lake Ontario exceeding 75.50 m (247.7 ft) in 2020.

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. 

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.