Moses Saunders Dam

Lake Ontario likely to exceed 2017 water levels


Lake Ontario water levels have reached 75.85 m (248.85 ft) and will likely reach or exceed the 2017 record high of 75.88 m (248.95 ft) with the next few days.  Forecasts show that Lake Ontario levels are expected to crest within the next one to three weeks, mostly likely within a few centimeters (approximately 1 in.) of the record high, but potentially higher levels are possible should wet weather continue.

The main drivers for the high water levels continue to be the uncontrolled and record-high inflows from Lake Erie, through the Niagara River, and above average precipitation across the Lake Ontario and Ottawa River basins for this time of year.

Outflows from Lake Ontario have been increasing since May 16, and further Lake Ontario outflow increases are expected to continue as frequently as conditions allow.

Levels are still above the criterion H14 high level that applies this time of year, authorizing the International Lake Ontario – St. Lawrence River Board to deviate from regulation Plan 2014.

With high water impacts continuing both upstream and downstream, the Board has decided to continue to adjust outflows according to the F-limit rules of Plan 2014. The F-limit tries to balance high levels upstream on Lake Ontario and the upper St. Lawrence, with those downstream on Lake St. Louis and the lower St. Lawrence. 

The intent is to balance high water levels in the interests of all stakeholders, and to regulate Lake Ontario outflows to provide all possible relief to shoreline property owners and communities both upstream and downstream of the Moses-Saunders Power Dam.

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;

Andrew Kornacki: (716) 879-4349, (716) 352-8669;


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.