Dry Conditions Lead to Low Water Levels: Board to Decrease Outflows
Lower than average precipitation and winter snowpack runoff have resulted in decreased inflows to Lake Ontario. The reduced inflows have resulted in lower water levels on Lake Ontario and the St. Lawrence River. In response to these conditions, the Board has decided to reduce outflows from Lake Ontario beginning on 10 April, 2021.
During January and February this year, the Board was deviating under authority granted by the International Joint Commission (IJC) to remove additional water from Lake Ontario as a result of the risk analysis in December 2020 showing approximately a 28% chance of water levels exceeding a damaging high water threshold in 2021. A total of 9.4 cm (3.7 in.) was removed from Lake Ontario to further reduce the risk of potentially damaging high water levels in late Spring and early Summer.
Due to the reduced spring runoff, the Board has decided to reduce outflows below those specified by the plan to restore the extra water removed during the winter to Lake Ontario at a rate of approximately 2 cm (0.8 in) of water to Lake Ontario per week for the next three weeks. After these 3 weeks, the Board will revert to plan-prescribed outflows.
This strategy will allow Lake Ontario and Lake St. Lawrence water levels to increase more than they would under plan-prescribed flows over the next few weeks. It now appears likely that Lake Ontario levels will remain below long-term average over the summer unless very wet weather occurs. Most forecast scenarios suggest that Lake Ontario levels will remain above critical low water level thresholds due to lower than average precipitation. Under this strategy, water levels in Lake St. Lawrence will experience short term increases as a result of its position as forebay of the Moses-Saunders Dam. However most forecast scenarios indicate dry conditions that will likely result in significantly below average Lake St. Lawrence levels this spring and summer.
This strategy is expected to have negligible impacts at Lake St. Louis near Montreal compared with the other strategies considered. Lake St. Louis levels may be up to 10 cm lower than they would be under plan-prescribed flows for the next few weeks. However, most forecast scenarios suggest that Lake St. Louis levels will remain above critical low-level thresholds for the spring and summer.
The Board will continue to monitor conditions closely through the summer. Should dry conditions persist, the Board will meet again regularly to discuss potential actions to adjust outflows.
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 https://www.facebook.com/InternationalLakeOntarioStLawrenceRiverBoard (English), and more detailed information is available on its website at https://www.ijc.org/en/loslrb.
Bryce Carmichael: (513) 418-8562
Sarah Lobrichon: (613) 794-8592
Or by email:
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.
The IJC announced that the size of the Board has been reduced from 12 members to 6 members effective 1 December, 2020. The re-structured Board continues to include one member each nominated by the Government of Canada, the Government of the United States, the Province of Quebec, the Province of Ontario and the State of New York and includes one additional member on the US side to ensure equal membership from both countries. Board members continue to serve in their personal and professional capacity and consider interests of the entire Lake Ontario-St. Lawrence River system. The Board’s online membership page has been updated here to reflect this change. This re-structure does not fundamentally alter the process by which the Board makes regulatory decisions. All 6 previous Board members are serving on an Interim Advisory Group (IAG). The IAG continues to attend meetings and their recommendations and input on regulatory decisions is still given significant weight in the Board’s final decision making process.
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 (ijc.org/loslrb) and Facebook page (https://www.facebook.com/InternationalLakeOntarioStLawrenceRiverBoard).