International Lake Ontario-St. Lawrence River Board Approves Minor Deviation Request by New York Power Authority to Support In-Water Work

Ottawa – The International Lake Ontario-St. Lawrence River Board has approved a request from the New York Power Authority to allow a 10-hour period of reduced flows on June 19, 2024, to ensure safe conditions for in-water inspections of dam facilities. Plan 2014 is a set of rules that govern Lake Ontario outflows through the Moses-Saunders Dam and Long Sault Dam located between Massena, New York and Cornwall, Ontario. Board Directives from the International Joint Commission determine what approvals can or cannot be granted and may specify limitations to deviations.
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The New York Power Authority has requested a Minor Deviation to occur on Wednesday, June 19 to reduce the outflow by 600 m3/s (21,189 cfs) for a 10-hour duration. During this time, there will be no flow through Long Sault Dam. This structure is used to release flow when the capacity of the Moses-Saunders Dam is limited by outages and repairs. The total flow through the Moses-Saunders Dam and Long Sault Dam is set in accordance with Plan 2014 and the Board’s Directives. After the 10-hour period, flow will again be released from Long Sault Dam. The total flow will increase to 100 m3/s above the Plan 2014 Rule Curve flow, to offset the 10-hour period of flows below Plan 2014.

Since the Board will offset the deviation within the same regulation week, there will be no cumulative impact on the water level of Lake Ontario.

June 19, 2024, there will be a +0.09 cm (0.04 inches) temporary impact on Lake Ontario.

June 20, 2024, there will be a +0.03 cm (0.01 inches) temporary impact on Lake Ontario

June 21, 2024, there will be 0 cm (0 inch) impact on Lake Ontario by end of day.

June 22 through 28, 2024, return to the applicable Plan 2014 Rule Curve.

The flow adjustments will be documented on the Lake Ontario Outflow Changes webpage in the tabular summary located at the bottom of the page. 

​For questions related to the work to be conducted by New York Power Authority, please contact their Massena, NY office at 315-764-6863.

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 Forecast: https://ijc.org/en/loslrb/watershed/forecasts

​To contact the International Lake Ontario-St. Lawrence River Board:

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

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

Facebook: https://www.facebook.com/InternationalLakeOntarioStLawrenceRiverBoard

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.