Flood Watch: St. Lawrence River

April 27, 2019

South Nation Conservation (SNC) has upgraded the Flood Outlook Statement issued on April 24, 2019 to a Flood Watch for the Saint Lawrence River.

Weather Forecast:
Environment and Climate Change Canada is forecasting up to 5 mm of rain today. An additional 20 to 30 mm of rain is expected Wednesday into Thursday, May 2, 2019.

Environmental Conditions:
According to the International Lake Ontario – St. Lawrence River Board (ILOSRB), Lake Ontario’s levels are increasing; a result of significant precipitation, reduced outflows, high inflows from Lake Erie, and spring runoff from tributaries.

Water levels between the Iroquois Dam and Moses-Saunders Dam have been rapidly increasing due to reduced outflows from Moses-Saunders Dam to limit flooding in the lower Saint Lawrence River near Montreal. Gates at Iroquois were lowered last week to supress water levels and keep them below flood values in the area.

Reduced outflows from the Moses-Saunders Dam to limit the flooding in the lower Saint Lawrence River are a direct result of the flooding currently occurring along the Ottawa River and its tributaries.

Water levels in the upper Saint Lawrence River area may have experienced a rapid increase over the past 24 hours due to a recent storm over Lake Ontario, causing strong winds and large waves.

While Lake Ontario’s current water level is above average, it is still within the historical range of observed levels at this time of year and currently well-bellow the extreme highs of 2017.

Risks:
According to the ILOSRB, Lake Ontario is expected to further increase this week as a result of forecasted precipitation combined with reduced outflows and high inflows from Lake Erie.

As a result of the increased outflows of Lake Ontario, Saint Lawrence River levels upstream of Iroquois throughout Edwardsburg/Cardinal and Augusta Township may increase.

Residents are also advised that wind may cause larger waves, further aggravating water levels which may affect structures close to shore.

ACTION:
Continued vigilance remains critically important; residents are advised to stay away from rivers as the forecasted weather may rapidly increase river flows and banks might be unstable and slippery. Parents are encouraged to explain these dangers to their children.

Residents in flood prone or low-lying areas historically susceptible to flooding are encouraged to closely follow evolving conditions, and should also take the necessary precautions to protect their property.

Duration:
This Flood Watch statement is in effect until Thursday, May 2, 2019.

SNC monitors the water levels and weather forecasts as part of the Flood Forecasting and Warning Program. Updates are provided as conditions change.

The International Lake Ontario – St. Lawrence River Board 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 at www.ijc.org/en/loslrb.

Please visit www.nation.on.ca for more information. To provide feedback with respect to changes in water related conditions please email waterwatch@nation.on.ca, posted on our Facebook (/SouthNationConservation) or Twitter (@SouthNationCA).

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