Plan 2014 continues to reduce Lake Ontario flood risks. Boat haulout assistance planned for Lake St. Lawrence


Lake Ontario water levels have recently dipped below long-term average for the first time since January 2017. However, regulated outflows from Lake Ontario, as prescribed by Plan 2014, will remain high in response to persistent, high supplies into the basin, specifically from Lake Erie. The high outflows continue to reduce the risk of Lake Ontario flooding, but have impacted levels in the St. Lawrence River, particularly on Lake St. Lawrence where water levels are well below average due to its location immediately upstream of the Moses-Saunders dam. As such, the Board will temporarily decrease outflows significantly over two 45-hour periods during the first two weekends of October to provide an opportunity for residents of Lake St. Lawrence to remove their boats and other equipment while river levels briefly rise.

The Board will temporarily reduce outflows through the Moses-Saunders Dam from 7 pm on 5 October through 4 pm on 7 October and from 7 pm on 12 October through 4 pm on 14 October to raise water levels on Lake St. Lawrence and provide two opportunities to assist with end-of-season boat haulouts. Decreasing the outflow through the dam has the effect of raising water levels on Lake St. Lawrence (while increasing the outflow lowers water levels). High outflows have resulted in below-average water levels in this area over the past several months. These flow decreases will 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. The Board acknowledges the concerns identified at recent meetings with the public in the area, and the Board takes each concern very seriously. The exact amounts of the water level rises 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 70 cm (2.3 feet) possible. These effects will be gradually reduced moving further upstream and will be insignificant beyond Prescott/Ogdensburg. The relatively brief outflow reductions will also have a negligible (2 cm (0.8 inch) total) and temporary impact on water levels on Lake Ontario, and any such impacts will be offset by a return to higher outflows shortly after 14 October. With Plan 2014 continuing to prescribe high outflows, the Board has determined the temporary decreases in outflow will not significantly impact the steady decline of Lake Ontario water levels.

Lake Ontario outflows continue to be set according to Plan 2014, which continues to respond to the near-average levels of Lake Ontario and above-average inflows from the upper Great Lakes. As of 18 September, Lake Ontario’s level was 3 cm (1.2 in.) below average, but 34 cm (13.4 in.) below the level on this date last year. Lake Ontario continues to decline steadily, and while rain events may cause lake levels to temporarily stabilize or rise slightly, water levels are expected to generally continue to fall over coming weeks.

Prior to and following the temporary flow changes planned in early October, and in response to the falling Lake Ontario levels and high outflows, Lake St. Lawrence’s level has generally been well-below average for this time of year. The current Lake St. Lawrence level is 72.75 m (238.68 ft), which is 41 cm (16.1 in.) below average. Lake St. Lawrence levels are generally expected to remain stable in coming weeks.

Ottawa River flows have recently been near record high for this time of year, but are declining, and are expected to generally continue declining into the fall. Lake St. Louis’ levels have generally declined since the final week of May, but the rate of fall slowed after mid July as Ottawa River flows stabilized, then rose. The current level is 21.41 m (70.24 ft), which is 27 cm (10.6 in.) above average. The temporary flow decreases may cause levels on Lake St. Louis to decline by up to approximately 40 cm (16 in.), but they are expected to remain above or near average.

The Board wishes to remind readers that weather and hydrologic conditions play a more predominant role than water regulation in influencing water levels, and extreme conditions may occur at any time in any given year. During extreme rainfall events, water levels can rise quickly throughout the Lake Ontario – St. Lawrence River system and may be amplified by wind forces. The Board can do little to prevent this occurrence through outflow regulation, so it urges communities to stay in contact with their local government officials and emergency managers and make arrangement to identify an emergency action plan to protect their property should these conditions occur. Likewise, low water level impacts can also occur during periods of extreme conditions such as severe droughts, so shoreline property and business owners, recreational boaters and local government officials, should always be prepared for the full range of water levels on Lake Ontario and the St. Lawrence River in the future.

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).



Rob Caldwell: (613) 938-5864;

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 75.88 m (248.95 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.