International Lake Ontario - St. Lawrence River Board

Board Will Assist with Boat Haul-Outs from Lake St. Lawrence


The International Lake Ontario - St. Lawrence River Board (Board) will temporarily reduce outflows through the Moses-Saunders Dam on October 7-8 in an effort to raise water levels on Lake St. Lawrence and provide a one-time opportunity to assist with end-of-season boat haul outs.

Lake St. Lawrence is the widening of the St. Lawrence River located immediately upstream (west) of the Moses-Saunders Dam at Cornwall, Ontario, and Massena, N.Y. Decreasing the outflow through the dam has the effect of raising the water level on Lake St. Lawrence, while increasing the outflow lowers the water level. Extremely high outflows have resulted in below average water levels in this area over the past several months.

The proposed flow decrease is expected to temporarily raise Lake St. Lawrence levels, which will assist marinas, yacht clubs and other recreational boaters in the area in removal of their boats prior to winter. This will be a one-time opportunity for this year and no further flow decreases will be considered for this purpose.

The exact amount of the water level rise will vary depending on a number of factors, including location, winds and other secondary factors. Areas immediately upstream of Moses-Saunders will see the greatest increase, with up to 60 cm (24 inches) possible. These effects will be gradually reduced moving further upstream and will be insignificant beyond Iroquois, Ontario.

The relatively brief outflow reduction will also have a negligible (less than 1 cm (0.4 inch)) and temporary impact on water levels on Lake Ontario, and any such impacts will be offset by a return to higher outflows shortly afterwards. With hydrologic conditions drastically improving since the extremely wet conditions experienced during April-July the Board has determined the temporary decrease in outflow will not significantly impact the steady decline of Lake Ontario water levels.

Gail Faveri: (905) 336-6007;
Arun Heer: (513) 684-6202;

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. 

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 75.73 m (248.5 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 ( and Facebook page ( 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.cawith the word ’subscribe’ in the title and body of your message.