Lake Ontario Outflow Changes

The regulation plan (Plan 2014) specifies a weekly average Lake Ontario outflow from Saturday through the following Friday. Throughout the year, the Lake Ontario outflow, which is managed at the Moses-Saunders Dam, may be modified more frequently depending on the conditions in Lake Ontario and the St. Lawrence River. There are two different types of outflow modifications: 

  1. Operational Adjustments, which do not have to be offset at a later date, and
  2. Deviations, which are classified as "minor" or "major" and generally do have to be offset at a later date.

Further details are available in the Directive on Operational Adjustments, Deviations and Extreme Conditions (https://ijc.org/en/loslrb/who/directives/deviations)


New!

We've made some formatting updates on this page. 

The tabular summary of flow changes is now in an expandable section at the bottom of this page.

Similarly, flow change records for previous years are also available in an expandable section at the bottom of this page.

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Notices


The outflow target for the week of April 20 through April 26 is the applicable Rule Curve flow of 8,120 m³/s. 


The outflow target for the week of April 13 through April 19 is the applicable Rule Curve flow of 7,770 m³/s.


The outflow target for the week of April 6 through April 12 is the applicable Rule Curve flow of 7,760 m³/s.


The outflow target for the week of March 30 through April 5 is the applicable Rule Curve flow of 7,730 m³/s.


The outflow target for the week of March 23 through March 29 is the applicable Rule Curve flow of 7,840 m³/s.


The outflow target for the week of March 16 through March 22 is the applicable Rule Curve flow of 7,820 m³/s. 


The outflow target for the week of March 9 through March 15 is the applicable Rule Curve flow of 7,700 m³/s. 


The outflow target for the week of March 2 through March 8 is the applicable Rule Curve flow of 7,720 m³/s.


The outflow target for the week of February 24 through March 1 is the applicable Rule Curve flow of 7,710 m³/s.

If ice resumes forming in the Beauharnois Canal, the outflow will be operationally adjusted in accordance with the Plan 2014 I Limit.


The outflow target for the week of February 17 through February 23 is the applicable Rule Curve flow of 7,770 m3/s.

If ice resumes forming in the Beauharnois Canal, the outflow will be operationally adjusted in accordance with the Plan 2014 I Limit.


The outflow target for the week of February 10 through February 16 is the applicable Rule Curve flow of 7,820 m3/s.

If ice resumes forming in the Beauharnois Canal, the outflow will be operationally adjusted in accordance with the Plan 2014 I Limit.


The outflow target for the week of February 3 through February 9 is the applicable Rule Curve flow of 7,800 m3/s.

If ice resumes forming in the Beauharnois Canal, the outflow will be operationally adjusted in accordance with the Plan 2014 I Limit. The ice cover that had formed in January has melted. As of today (February 1), there is no significant ice cover in the Beauharnois Canal or on Lake St. Lawrence.


The outflow target for the week of January 27 through February 2 is the applicable Rule Curve flow of 7,580 m3/s.

However, the outflow will continue to be operationally adjusted in accordance with the Plan 2014 I Limit. On January 18, the outflow was temporarily reduced to 6,800 m3/s when ice started accumulating in the Beauharnois Canal. Ice formation has since paused with milder temperatures, allowing the outflow to be gradually increased again on January 22 and 23. As of today (January 25), a 5 km ice cover remains in the Beauharnois Canal. It is anticipated that the outflow will have to be reduced again when colder temperatures return.


(Updated)

The outflow target for the week of January 20 through January 26 is the applicable Rule Curve flow of 7,560 m3/s.

However, the Lake Ontario outflow has been reduced to promote the formation of an ice cover in the Beauharnois Canal. About 1 km of ice has accumulated in the Beauharnois Canal.

During the winter months, the outflow will continue to be operationally adjusted in accordance with the Plan 2014 I Limit, as needed, to promote the formation and stability of ice covers in the Beauharnois Canal and on Lake St. Lawrence.

For more information,


The outflow target for the week of January 13 through January 19 is the applicable Rule Curve flow of 7,460 m3/s.


The outflow target for the week of January 6 through January 12 is the applicable Rule Curve flow of 7,420 m3/s.


The outflow target for the week of December 30, 2023 through January 5, 2024 is the applicable Rule Curve flow of 7,400 m3/s.

 

Tabular Summary of Lake Ontario Outflow Changes
DATEHOUROUTFLOWOUTFLOWNOTES
(YYYY-MM-DD)(HHMM)(m3/s)(cfs) 
2024-04-2000018,120286,800Rule Curve
2024-04-1300017,770274,400Rule Curve
2024-04-0600017,760274,000Rule Curve
2024-03-3000017,730273,000Rule Curve
2024-03-2300017,840276,900Rule Curve
2024-03-1600017,820276,200Rule Curve
2024-03-0900017,700271,900Rule Curve
2024-03-0200017,720272,600Rule Curve
2024-02-2400017,710272,300Rule Curve
2024-02-1700017,770274,400Rule Curve
2024-02-1000017,820276,200Rule Curve
2024-02-0300017,800275,500Rule Curve
2024-01-2700017,580267,700Rule Curve
2024-01-2312017,560267,000Rule Curve
2024-01-2212017,200254,300I Limit
2024-01-1819016,800240,100I Limit
2024-01-1300017,460263,400Rule Curve
2024-01-0600017,420262,000Rule Curve
2023-12-3000017,400261,300Rule Curve