International Lake Ontario - St. Lawrence River Board

Board follows Plan flow


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 Plan flows.  The Board will also continue to permit additional under- or over-discharges that may be necessary to address unforeseen critical conditions in the river. 

During the winter months, the Board did deviate from Plan flows to assist in ice management.  By February 21, 2014, Lake Ontario level was back to Plan level.  However, over-discharges were again made to assist ships in the Port of Montreal, resulting in the Lake Ontario level 3 mm (0.1 in) lower than they would have been under continuous Plan flows.   This water is expected to be restored either prior to or during the Ottawa River freshet, which is likely to begin in the coming weeks.

After starting the year slightly above average, Lake Ontario is currently below its normal seasonal rise. The level on March 27 was about 74.54 m (244.55 ft), about 18 cm (7.1 in) below long-term average for this time of year.  This is well within Lake Ontario’s 1.22 m (4 ft) range, being 83 cm (32.7 in) below the lake’s upper limit, and 39 cm (15.4 in) above its lower limit which starts later in April.  Lake St. Lawrence, just upstream of the Moses-Saunders powerhouse, was about 46 cm (18.1 in) below average.  Downstream, the levels at Lake St. Louis were 47 cm (18.5 in) below average, but 36 cm (14.2 in) above the Seaway Low Alert level, and at Montreal Harbour, levels were 116 cm (45.7 in) below average, but 26 cm (10.2 in) above chart datum.

The Board, in conjunction with its staff, continues to monitor the situation closely and is prepared to take further action as required.  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.