Drone shot of Moses-Saunders Dam

The International Lake Ontario-St. Lawrence River Board continues to Act to Reduce Spring Flood Risk through 28 February


The International Lake Ontario - St. Lawrence Board is optimistic that weather conditions the rest of this winter and spring won’t cause a damaging rise in Lake Ontario levels this year. However, it has been acting proactively since 1 January to reduce lake levels this winter just in case the weather turns wet.

Somewhat drier weather conditions over the past several months coupled with favorable river ice conditions and continued high outflows from Lake Ontario have caused a decline in the lake’s level, such that it is now a few centimeters below the seasonal long-term average. Under the Board’s current deviation strategy, outflows from Lake Ontario have been maximized and set above some Plan 2014 prescribed limits, resulting in the removal of an additional 7.9 cm (3.1 in) of water from Lake Ontario when compared to strict adherence to Plan 2014 rules. The Board intends to continue this strategy through 28 February.

This week, the International Joint Commission (IJC) approved the Board’s request for continued authority to deviate from Plan 2014, if necessary, until Lake Ontario reaches its peak level this spring.  The previous deviation authority granted to the Board is set to expire on 28 February. The extended authority recently granted the Board would only be applied should conditions worsen after 1 March. This authority, if implemented, would allow for outflows from the Moses-Saunders dam on the St. Lawrence River may be increased to exceed Plan 2014 flows.

The risk of high water on Lake Ontario in 2021 remains a moderate possibility, but less likely than the risk was last spring at this time.  While water levels on Lake Erie and the upper Great Lakes are all lower than a year ago, they are still very high.  This will cause inflows to Lake Ontario from Lake Erie to remain high over the coming months. These expected high inflows, coupled with uncertain seasonal factors such as precipitation and snowpack runoff, cause a moderate risk of a high-water event in the Lake Ontario basin this spring.

The Board and IJC recognize the threats posed by continued high inflows from Lake Erie into the system and the risk of another high-water event on Lake Ontario and the St. Lawrence River in 2021.  Given that conditions can rapidly change in the spring months, the Board sought extended deviation authority to allow the Board to react as quickly as possible with deviations from Plan flows should conditions worsen. 

Basin conditions will be frequently assessed by the Board and appropriate deviations applied should conditions worsen.  This will help reduce the risk of high-water levels this spring in balance with the interests of other groups throughout the system.  Given the lower risk of reaching flood levels on Lake Ontario this spring as compared to last year at this time, the Board does not expect its deviation strategies would interrupt or negatively impact commercial navigation in the St. Lawrence Seaway.  

The Board emphasizes that, if basin conditions should become extremely wet, similar to those observed in 2017 and 2019, no deviation strategy will prevent water levels that can cause flooding and damage to shoreline properties. Eliminating such damages is beyond the reach of outflow regulation and are more reliably addressed through coastal resilience and planning.

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 https://www.facebook.com/InternationalLakeOntarioStLawrenceRiverBoard (English), and more detailed information is available on its website at https://www.ijc.org/en/loslrb.


Rob Caldwell:              (613) 938-5864                                    Rob.Caldwell@canada.ca

Bryce Carmichael:      (513) 418-8562                      ILOSLRB-USSection@usace.army.mil

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.  The IJC announced that they are reducing the size of the Board from 12 members to 6 members effective 1 December, 2020. The re-structured Board will continue to include one member each nominated by the Government of Canada, the Government of the United States, the Province of Quebec, the Province of Ontario and the State of New York and will include one additional member on the US side to ensure equal membership from both countries. Board members will continue to serve in their personal and professional capacity and consider interests of the entire Lake Ontario-St. Lawrence River system. The Board’s online membership page has been updated here to reflect this change. This re-structure does not fundamentally alter the process by which the Board makes regulatory decision.  All 6 previous Board members have been asked to serve on an Interim Advisory Group (IAG).  The IAG continues to attend meetings and their recommendations and input on regulatory decisions is still given significant weight in the Board’s final decision making process.

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 (ijc.org/loslrb) and Facebook page (https://www.facebook.com/InternationalLakeOntarioStLawrenceRiverBoard).To 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

stlaw-L-subscribe@cciw.ca with the word ’subscribe’ in the title and body of your message.