IJC’s International Lake Ontario-St. Lawrence River Board Announces Better Water Conditions Downstream Allow Outflows To Be Set For Navigation

LAKE ONTARIO – Thanks to favorable weather and water supply conditions the board no longer needs to limit outflows to alleviate flooding risks downstream.

That means that outflows will now be at the maximum rate to lower water levels on Lake Ontario, while maintaining currents in the St. Lawrence River that allow for commercial navigation.

Water levels throughout the Lake Ontario – St. Lawrence River system are expected to peak well below the record-highs of 2017 and 2019.

Spring 2020 Weather Conditions Show Significant Improvements Over 2019

In the spring, the flows from the Ottawa River basin, a major tributary of the St. Lawrence River, combine with the outflow from Lake Ontario to contribute to the water level of downstream reaches of the St. Lawrence River, near Montreal.  Inflows from Lake Erie, precipitation on the lake and runoff from its drainage basin less any evaporation and the outflow, constrained by downstream conditions, continue to be the factors contributing to the water level of Lake Ontario.

• The International Lake Ontario – St. Lawrence River Board web page, at  https://ijc.org/en/loslrb/watershed/flows, shows the flows in the system.  The Board was able to keep Lake Ontario outflows high because the Ottawa River system reached a lower peak earlier than in 2017 and 2019, In addition, the current flow of the tributary is much lower, as seen in the interactive graphic on the Ottawa River tab. The decline in Ottawa River flow means that conditions downstream are able to handle additional outflow from Lake Ontario.

• Despite extremely high and sustained inflows from Lake Erie (see Lake Erie tab), water levels on Lake Ontario have had a much more moderate rise this spring (see https://ijc.org/en/loslrb/watershed/water-levels ) .

• In addition to the recent drier spring conditions in the Lake  Ontario – St. Lawrence River system, the Board has taken every opportunity to remove as much water as possible from Lake Ontario without causing undue impacts upstream and downstream of the Moses-Saunders Power Dam since its peak last June 2019.

Future Outflow Strategy

The Board may continue to deviate from Plan 2014 as it plans to continue to release as much water as possible while keeping currents at or below safe rates in the critical reaches of the St. Lawrence River.   The IJC granted the board deviation authority last fall, continuing until the peak of Lake Ontario is reached for 2020.

• The Board, with feedback from mariners, will attempt to release additional outflow than that prescribed in the L-Limits of Plan 2014.

• The St. Lawrence Seaway Corporations will undertake measures through its locks and critical reaches of the St. Lawrence River to mitigate the impacts of higher outflows on navigation.

• In previous years, the Lake Ontario summer outflow reached 10,400 m3/s (367,000 cfs), but with Lake Ontario water levels expected to be lower this year, it is unlikely that this outflow rate will be achieved this year.  With water levels lower, there is less capacity in the channel to move water without an increase in velocity that would impact navigation and recreation and cause detrimental river erosion.
• Temporary outflow reductions will be required this weekend and possibly again in late-May to allow Hydro-Quebec to safely install several safety booms around their structures prior to summer.  This work was started earlier this spring and would normally be completed during reduced flows for the Ottawa River freshet, but this year outflows have been high and increased more rapidly owing to the Board’s deviation strategy.

Municipalities and residents along the Lake Ontario and St. Lawrence shoreline should continue to discuss and undertake action plans that will build resiliency into the shoreline and prepare for the high and low water events of the future.

Please note that the Board has created a website page focused on the recent high-water events: https://ijc.org/en/loslrb/q&a (English) [https://www.ijc.org/fr/clofsl/questions (French)]. All high-water related materials are now in one easily accessible place.

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.

Press release from the International Lake Ontario-St. Lawrence River Board.

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