International Lake Ontario - St. Lawrence River Board

Board decides to restore water relative to Plan 1958-D levels


The International St. Lawrence River Board of Control (Board) recently reviewed conditions in the LakeOntario-St.Lawrence River system and agreed to release outflows slightly above those of the regulation plan, Plan 1958-D, to gradually reduce the 2.7 cm (1.1 in) of water stored on Lake Ontario.  The outflows will be above those specified by Plan 1958-D by 150 m3/s (5300 ft3/s) from November 2 to December 7, 2013 and 120 m3/s (4200 ft3/s) during the following week.  The Board will continue to permit additional under- or over-discharges that may be necessary to address unforeseen critical conditions in the river.  Earlier this year, when Lake Ontario was low and water supply conditions dry, the Board proactively retained water to meet potential critical needs.  This stored water is no longer needed now. 

After starting the year well below average, and peaking in July above average, Lake Ontario is currently in its normal seasonal decline.  The water level on October 23 was 74.63 m (244.85 ft), about 4 cm (1.6 in) above long-term average for this time of year.  This is well within Lake Ontario’s 1.22 m (4 ft) range, being 74 cm (29.1 in) below the lake’s upper limit, and 48 cm (18.9 in) above its lower limit.  Lake St. Lawrence, just upstream of the Moses-Saunders powerhouse, is about 36 cm (14.2 in) above average.  Downstream, the levels at Pte. Claire on Lac St-Louis are about 22 cm (8.7 in) below average, but 31 cm (12.2 in) above the Seaway Alert level, and at Montreal Harbour, levels are about 51 cm  (20.1 in) below average, but 20 cm (7.9 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 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;

John Kangas: (312) 846-5348;

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.