Lake Ontario shipping opens late to help prevent flooding

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ROCHESTER, NY (WROC) – As of April 1, Shipping lanes from Lake Ontario through the St. Lawrence seaway are now open. This is two weeks behind from a normal year thanks to push from organizations to keep outflows high through the winter and spring. Ideally, that would help prevent future flooding on Lake Ontario like what happened in both 2017 and 2019.

The International Lake Ontario-St. Lawrence River Board (a subsidiary of the International Joint Commission, IJC) regulates Lake Ontario outflow on the Moses-Saunders Dam along the St. Lawrence river. They said in a newsletter that outflows were allowed to be near or above record highs for the season thanks to a milder winter and less ice formation. Infrequent freeze/thaw cycles from a warm season allow higher outflows since the threat of ice jams lowers.

Many different factors are taken into consideration when it comes to managing outflows. That includes those along the southern shores of Lake Ontario, wildlife habitat, and shipping among others. The seaway corporation decides when the shipping season begins based on how water flows are being managed by the IJC. They made the decision to push back the start of the season from March 20 to April 1.

Among many factors, this took into account the potential of water levels remaining high and high outflow potential later in the shipping season. According to Bryce Carmichael, “The impacts are not as high as they would be in the middle of the season,” said Carmichael, US secretary of the Lake Ontario-St. Lawrence River Board and civil engineer for the US Army Corps of Engineers. “So part of the calculation on their part took into account that having more water removed now makes the risk lower in the mid season summer months.” Getting more water out now could prevent from shipping problems down the road if more water needs to be let out come peak shipping season in June, July, and August.

See below how 2020 outflow has remained higher than the past 3 years. While there was significant volatility, outflow was near the record set in the summers of 2017 and 2019.

Lake Ontario gets around 80% of its water over Niagara Falls from Lake Erie. Above is a graph of outflow downstream through the Moses-Saunders Dam on the St. Lawrence River.

According to the Army Corps of Engineers, the Lake Ontario water level is over a foot above average and is forecast to rise another 6-8 inches by the end of the month.

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