Moses-Saunders Dam

IJC’s International Lake Ontario-St. Lawrence River Board announces that current conditions are stabilizing and expected to improve across Lake Ontario – St. Lawrence system


Water levels throughout the Lake Ontario – St. Lawrence River system in 2020 are expected to peak well below the record-highs of 2017 and 2019, according to the latest projections from the International Lake Ontario-St. Lawrence River Board. While Lake Ontario’s water level is currently well above average, improving conditions are the result of much more moderate weather and water supply conditions this year, as well as actions taken by the Board to increase Lake Ontario outflows and help the system recover faster following extreme water level periods.

With the expertise gained from 2017 and 2019, the Board and its technical team pushed beyond Plan 2014’s limits to increase outflow limits and downstream water level limits beyond those previously perceived as feasible, resulting in some positive gains this winter and spring - though with plenty of help from Mother Nature too. It’s worth reiterating that no regulation plan can be designed to address every imaginable and sustained extreme weather event and provide total protection for all water uses throughout the system at all times. While the Board is encouraged by current and projected water levels, the Board can’t predict what the weather will bring and encourage shoreline communities to not let their guards down.

Improving conditions can be seen on the International Lake Ontario – St. Lawrence River Board web page, and are outlined below: A key factor contributing to lower water levels is that the Ottawa River system has reached a peak earlier than in 2017 and 2019, and its current flow is much lower, as seen in the interactive graphic on the Ottawa River tab.

The Board has been able to continue increasing Lake Ontario outflows (see Lake Ontario tab), in part, because the Ottawa River has been declining and conditions downstream can now handle additional flow.

These conditions have allowed levels on Lake Ontario to see a much more moderate rise this spring, despite extremely high and sustained inflows from Lake Erie (see Lake Erie tab). All four of the upper Great Lakes are at or above record levels, whereas Lake Ontario is well above average, but still well below record levels.  

The Board constantly reviews the outflow regulation strategy in conjunction with real time prevailing conditions to make use of every opportunity to remove as much water as possible from Lake Ontario without causing undue impacts upstream and downstream of the Moses-Saunders Power Dam. In 2019-2020, these efforts were augmented through the deviation authority granted by the International Joint Commission. The Board used that deviation authority to make use of all windows of opportunity provided by actual regional weather and system conditions, which Plan 2014 rules (or any outflow regulation plan) could not take into account.

Looking Back

On April 23 of last year, the Ottawa River freshet had only recently begun.  Flooding in the St. Lawrence River below Montreal was severe, as this aerial video shows.  Despite a reduction in the Lake Ontario outflow ten days earlier, as the flow from the Ottawa River rapidly increased, the volume of water reaching downstream flooded overland, stranding houses and forcing the evacuation of 3,000 homes.  The level of Lake Ontario, starting below where it is this year, went up 16 cm (6 in) over this 10-day period, as reduced outflows combined with rapidly rising inflows from Lake Erie, precipitation and runoff following a series of heavy storms.  The Ottawa River in 2019 peaked even later, on May 1, leaving this area around Lake St. Peter flooded for several weeks.  Lake Ontario continued rising through May, not reaching its peak until June.

Looking Forward

As the Lake Ontario outflow continues to increase as the Ottawa River flow decreases, navigation will become the limiting factor for the system.  In previous years, the Lake Ontario summer outflow reached 10,400 cms (367,000 cfs), but with Lake Ontario water levels expected to be lower this year, it is unlikely that this outflow will be achieved in 2020.  With water levels lower, there is less capacity in the channel to move water without an increase in velocity that would impact navigation, recreation, and cause additional shoreline erosion.

Municipalities and residents along the Lake Ontario and St. Lawrence shoreline should continue to put action plans in place that will build resiliency into the shoreline and prepare for the high and low water events of the future. 

Please note that the Board has created a website page focused on the recent high-water events: (English) [ (French)]. All high-water related materials are now in one easily accessible 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


Rob Caldwell:              (613) 938-5864                          

Andrew Kornacki:       (716) 879-4349             

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.