Records set for lake outflows, inflows

Record amounts of water were released from Lake Ontario during the month of January and into February, but inflows also set records over the same time period, according to representatives from a body that helps oversee water levels. 

The International Lake Ontario- St. Lawrence River Board, a subsidiary of the International Joint Commission, said Friday that mild temperatures and minimal ice cover along the St. Lawrence River made it possible to release record amounts of water from Lake Ontario last month.

The board also indicated that the continuing trend of extremely high water supplies, which has now lasted over three years, continues to hamper efforts to help reduce flood risks throughout the Lake Ontario-St. Lawrence River system.

According to the board, the total amount of water released from Lake Ontario from January 2017 through December 2019 was the highest on record for any 36-month period, however, total inflows were also the highest on record.

Representatives said the latest record outflows come as the International Lake Ontario – St. Lawrence River Board continues to deviate from Plan 2014 to maximize outflows and remove as much water from Lake Ontario as conditions will allow to reduce the risk of high water this spring.

An especially mild month in January and limited ice cover in critical areas of the St. Lawrence River provided favorable conditions to allow the release of an exceptional volume of water from Lake Ontario, the board indicated. 

Near Moses-Saunders Dam, at Massena, NY, it was the 6th warmest January on record going back to 1949. Mild weather at the start of the month delayed ice formation and allowed record outflows averaging 10,430 m3/s (368,300 cfs) during the first 11 days of January, the board noted. 

According to a release, exceptionally high Lake Ontario outflows pushed St. Lawrence River levels at Lake St. Louis near Montreal to just below flood elevation, and caused record-low levels at Lake St. Lawrence just upstream of Moses-Saunders Dam. Then on 11-12 January, a significant storm tracked through southern Ontario and Quebec, rapidly increasing tributary flows, and requiring temporary outflow reductions to keep Lake St. Louis below flood levels, the board indicated. 

Outflows remained above typical January values throughout the month, and by the end of January the ice cover had again thawed and broken up, allowing outflows to again be increased to record highs. Overall, the average outflow in January was 9,210 m3/s (325,200 cfs), 740 m3/s (26,100 cfs) above the previous January record set in 1987.

Despite these unprecedented outflows, Lake Ontario rose during January as record net total supplies (inflows) to Lake Ontario averaged 10,140 m3/s (358,100 cfs). The high inflows were largely the result of heavy rainfall that rapidly increased streamflows during and following the significant storm event on 11-12 January. This storm also caused rapidly rising Lake Erie levels and resulted in record-inflows to Lake Ontario from the Niagara River by the end of January.

The net result is that water levels have begun to rise from their seasonal low, reached in December, and Lake Ontario’s level was 75.13 m (246.49 ft) as of 6 February and again near record highs for this time of year. Lake Erie and the upper Great Lakes are all at record highs as well, and this continues to result in an increased risk of high water this spring.

The board indicated that flows will be reduced temporarily starting this afternoon as ice has begun to re-form in the Beauharnois Canal.

Board representatives say they continue to closely monitor conditions and look for every window of opportunity to continue maximizing outflows to the extent possible to reduce the risk of high levels in 2020

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