International Lake Ontario - St. Lawrence River Board

Outflows according to Plan as Board prepares for winter


The International St. Lawrence River Board of Control (Board) recently reviewed conditions in theLakeOntario-St.Lawrence River system and has decided to continue to follow the Plan-prescribed outflows until winter ice conditions require otherwise.  Water levels throughout the system are all close to their long-term averages, and well within the limits of the regulation Plan 1958-D.  The Board will continue to permit additional under- or over-discharges that may be necessary to address critical conditions, though none are foreseen at this time.  

Lake Ontario is currently slightly below its long-term average level for this time of year. The level on October 22 was 74.57 m (244.65 ft), 2 cm (0.8 in) below average. This is well within Lake Ontario’s 1.22 m (4 ft) range, being 80 cm (31.5 in) below the lake’s upper limit, and 42 cm (16.5 in) above the lake’s lower limit.  The level at Lake St. Lawrence, just upstream of the Moses-Saunders powerhouse, was about 42 cm (16.5 in) below average.  Downstream, the level at Lake St. Louis was 25 cm (9.8 in) above average; at Montreal Harbour, the level was 32 cm (12.6 in) above average. 

The Board, in conjunction with its staff, continues to monitor the system.  Outflow changes are posted to the Board’s Facebook site at (English) and its website at under the Maps & Data tab, Lake Ontario outflow changes. 

Water levels on bothLakeOntarioand theSt. Lawrence Rivervary considerably from year to year depending on the weather conditions. The Board urges everyone to be prepared to live within the full range of levels that have occurred.   Although the Board strives to maintain the range of monthly mean levels of Lake Ontario below the upper limit of 75.37 m (247.3 ft) and above the lower limit (from April through November) of 74.15 m (243.3 ft) specified in the Orders of Approval, since regulation began in 1960, actual monthly levels have ranged from a high of 75.73 m (248.5 ft.) to a low of 73.82 m (242.2 ft) due to climate conditions outside the design range.  Levels on the river tend to vary more widely.  Furthermore, excessive wind set up and wave action may significantly increase or decrease local levels on both the lake and river.   Strong winds can change water levels temporarily by over half a metre (2 feet) in some locations.  


Gail R. Faveri: (905) 336-6007;

Kyle McCune: (513) 684-3014;


The International St. Lawrence River Board of Control was established by the International Joint Commission in its 1952 order of approval. The Board’s main duty is to ensure that outflows from Lake Ontario meet the requirements of the IJC order; it also develops regulation plans and conducts special studies requested by the IJC. For more information, visit To receive a weekly e-mail 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.