Moses Saunders Dam

High Lake Ontario Outflows Continue


The outflow from Lake Ontario remains very high and it continues to be gradually increased in response to rising Lake Ontario levels and persistently high inflows from Lake Erie.  

Other than a brief pause, to allow ice to form on the St. Lawrence River in January, outflows have generally been increasing since October 2018.  This followed many months of very high outflows that go all the way back to the extreme high water event of 2017.  Today the outflow is 8,700 m3/s (307,200 ft3/s), which is one of the highest outflows for this date since 1960.  The high outflows are being set in accordance with Plan 2014 and in consideration of the effects on interests throughout the Lake Ontario – St. Lawrence River system.  Recently, the high flows have resulted in extremely low water levels on Lake St. Lawrence, immediately upstream of Moses-Saunders Dam, and this has required careful adjustments over the past several weeks to maintain a minimum level there of 71.80 m (235.6 ft) to protect municipal and domestic water intakes in this area.

The regulation plan is calling for these high outflows due to several factors.  The most significant factor is the high water levels of both Lake Ontario and Lake Erie.  The Niagara River, which connects Lake Erie to Lake Ontario, is a major contributor to the amount of water that drains into Lake Ontario.  Under extreme conditions, precipitation on the Lake and within its local drainage basin can also be a major contributor of water into Lake Ontario.  These uncontrolled, natural water supply conditions are the primary factor that determines Lake Ontario water levels. As a result, regulation of outflows cannot control the water levels of Lake Ontario, only influence them, and conditions throughout the St. Lawrence River must also be considered.

The Board, in conjunction with its staff, continues to monitor conditions on an ongoing basis. Information on hydrologic conditions, water levels and outflows, including graphics and photos, are available on the Board’s website and posted to the Board’s Facebook page at (English),
and more detailed information is available on its website at


Rob Caldwell: (613) 938-5864;

Bryce Carmichael: (513) 684-2010; Bryce

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 75.88 m (248.9 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 ( 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 with the word ’subscribe’ in the title and body of your message.