Moses Saunders Dam

Lake Ontario Levels Continue to Decline as Outflows Reduced


Lake Ontario levels reached 75.50 m (247.7 ft) and the record outflows of 10,400 m3/s (367,270 cubic feet per second) were reduced to 10,110 m3/s (357,000 cubic feet per second) at 12:01AM on August 21, 2019.  This flow rate is 200 m3/s (7,060 cubic feet per second) above the normal safe navigation flow limit that applies at the current Lake Ontario elevation as defined by the regulation plan. This flow represents a 3% reduction of outflows and remains a record-high value for this time of the year. The sustained record outflows of 10,400 m3/s (367,270 cubic feet per second) were maintained from June 13, 2019 through August 20, 2019 for a total of 69 days, 15 days longer than in 2017. 

The Board’s major deviation strategy set in July included steps for transitioning off 10,400 m3/s and remaining 200 m3/s above the normal safe navigation limit for the St. Lawrence River. The outflow strategy for the remainder of 2019 is intended to sustain the accelerated decline of Lake Ontario levels through the end of the year.  The Board recognizes the need to address persistent elevated levels on Lake Ontario and the Board remains committed to providing the highest achievable relief to Lake Ontario in consideration of the impacts of that relief on the St. Lawrence River interests. 

Velocities increase because, as the lake level decreases, so does the water level within the upper part of the St. Lawrence River, reducing the amount of space for water being released to move in. Imagine the channel as a trough and as the water level lowers, the depth of water in the trough decreases. For the same flow (e.g., 10,400 m3/s) to go through that trough, the water has to move faster.

Given the current conditions, velocities are higher than normal throughout the river and they are already causing unsafe cross-currents and erosion and are impacting boating, swimming and navigation. Sustaining or increasing velocities would cause conditions to become much worse.

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 75.92 m (249.1 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.