International Lake Ontario-St. Lawrence River Board to Increase Lake Ontario Outflows to Help Lake St. Louis Recreational Boaters Remove Their Watercraft on October 18

The International Lake Ontario-St. Lawrence River Board plans to increase Lake Ontario outflows by up to 500 m³/s (17,700 ft³/s) to temporarily raise the water level of Lake St. Louis on October 18. This temporary increase in Lake St. Louis water levels is intended to help people remove recreational boats more easily. To ensure that the water level of Lake St. Louis is raised for the entirety of daylight hours on October 18, the Lake Ontario outflow will be increased from 7:01 am on Friday, October 17, to 7:01 pm on Saturday, October 18. The exact water level of Lake St. Louis on October 18 will depend on water supplies but is expected to be at least approximately 20.80 m (68.24 feet). The Board last assisted with boat haul out on Lake St. Louis in 2012.

The Lake Ontario outflow increase is permitted by Minor Deviation Authority which allows the Board to deviate from prescribed Regulation Plan 2014 outflow to respond to short-term needs on the St. Lawrence River. Minor deviations are only permitted under certain circumstances:

• There must be no appreciable adverse effects to other interests.
• The Board shall not allow the cumulative effect of minor deviations to cause the Lake Ontario level to vary by more than +/- 2 cm (0.8 inch) from that which would have occurred had the releases prescribed by the approved regulation plan been strictly followed.
• Minor deviations require water flow accounting and restoration.

The minor deviation to help with Lake St. Louis recreational boat haul out on October 18 will not meaningfully affect water levels on Lake Ontario, but the water level of Lake St. Lawrence will temporarily decrease.

1. A 500 m³/s (17,700 ft³/s) flow increase would have a temporary -0.34 cm (0.1 inch) impact on Lake Ontario.
   • As required by the IJC’s Directive, the small amount of additional water that will be released from Lake Ontario during this temporary outflow increase will be completely restored in the coming months as conditions permit.
2. Lake St. Lawrence is a man-made widening in the St. Lawrence River, known as the forebay, that was created when the Moses-Saunders Dam was constructed. The forebay experiences more pronounced water level changes than Lake Ontario because of how close it is to the Moses-Saunders Dam.
   • It is expected that Lake St. Lawrence water levels will remain above 73.10 m (239.83 feet) during and after the minor deviation.
   • However, the water level will temporarily decrease by approximately 20-30 cm (8-12 inches) on October 18.
   • Recreational boaters are encouraged to monitor the Lake St. Lawrence water level forecast available on the second tab at this link: https://ijc.org/en/loslrb/watershed/forecasts 

As of August 31, the Canadian Drought Monitor shows the Lake Ontario and St. Lawrence River regions are experiencing a moderate to severe drought. Without knowing the water supplies that will occur over the next month, the Board commits to a maximum deviation of +500 m³/s (17,700 ft³/s). The Board will continue to monitor weather forecasts, water supply conditions, and refine the minor deviation strategy as necessary in the coming weeks. 

• Under a dry scenario, outflows are likely to be set in accordance with the minimum M Limit leading up to the deviation. The M-Limit rules maintain minimum water levels on Lake St. Louis in consideration of Lake Ontario, primarily for commercial navigation. When the M-Limit rules are in effect, Lake Ontario outflows are adjusted, as needed, to maintain a specified minimum water level on Lake St. Louis in accordance with Table B2 of the Compendium Report. The water level of Lake Ontario is expected to remain above 74.20 m (243.44 feet) in October. Therefore, the Lake Ontario outflow will be adjusted to maintain the water level of Lake St. Louis near or above 20.64 m (67.72 feet). On October 18, an increased outflow of +500 m³/s (17,700 ft³/s) would provide an approximate 15 cm (6 inch) increase in water levels to reach approximately 20.80 m (68.24 feet).
• Under an average water supply scenario, outflows would not need to be increased as much and would only be increased to what is needed to achieve 20.90 m (68.57 feet).
• Under a wet scenario, if the water level of Lake St. Louis is expected to be 20.90 m (68.57 feet) by following Regulation Plan 2014, the deviation would not be conducted.

For more information on:

• Lake Ontario Outflow Changes: https://ijc.org/en/loslrb/watershed/outflow-changes
• Water Levels: https://ijc.org/en/loslrb/watershed/water-levels
• Water Supplies: https://ijc.org/en/loslrb/watershed/flows
• Water Level Forecasts:
  • https://ijc.org/en/loslrb/watershed/forecasts
  • https://www.tides.gc.ca/en/monthly-water-level-bulletin-great-lakes-and-montreal-harbour
  • https://e-navigation.canada.ca/topics/water-levels/central/bulletin-en

Contacts:

United States: ILOSLRB-USSection@usace.army.mil 

Canada: ec.cilofsl-iloslrb.ec@canada.ca

The International Lake Ontario-St. Lawrence River Board ensures that outflows from Lake Ontario meet the requirements of the International Joint Commission’s Orders of Approval. Under any regulation plan, the ability to regulate the outflow from Lake Ontario does not mean that full control of lake levels is possible. This is because the major factors affecting water supply to the Great Lakes - precipitation, evaporation, and runoff - cannot be controlled, and are difficult to accurately predict.