Lake Ontario outflows reduced

A view of Moses-Saunders power dam with Hawkins Point visitors center in the foreground. Christopher Lenney/Watertown Daily Times

WATERTOWN — Record amounts of water out of Lake Ontario, record amounts right back in.

That is the pattern for water levels on the lake and the St. Lawrence River, which remain near record-high levels for this time of year, continuing to raise concerns that levels in the coming months could reach flood stage, as they did in 2017 and 2019.

The International Lake Ontario-St. Lawrence River Board, which regulates lake levels according to the International Joint Commission’s Plan 2014, said Friday it has made little headway in combating the high levels, despite deviating from Plan 2014 and releasing as much water from the lake as possible under the conditions.

Lake and river levels are regulated through releases of water at the Robert Moses-Robert H. Saunders Power Dam in Massena and Cornwall, Ontario. The river board determines outflows following Plan 2014 criterion, but the board has received the IJC’s approval to deviate from the plan until at least June.

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, yet net total inflows were also the highest on record. About 85 percent of Lake Ontario’s water comes from the upper Great Lakes, which are similarly swollen, with the remainder coming from tributaries and precipitation.

The problem currently is that more supply is entering the system than the system can let out. The board says that mild weather and limited ice cover in critical areas on the St. Lawrence River in January “provided favorable conditions to allow the release of an exceptional volume of water from Lake Ontario.”

Near the dam in Massena, it was the sixth warmest January since 1949, which delayed ice formation and allowed for record outflows that averaged 10,430-cubic-meters-per-second during the first 11 days of January. These high lake 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 the Moses-Saunders Dam, the board said.

On Jan. 11 and Jan. 12, 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.

Also, a brief cold snap in mid-January caused ice to begin to form downstream of the Moses-Saunders dam in the area of the Beauharnois Canal in Quebec, which prompted the board to reduce outflows to facilitate ice formation. This needs to be done to prevent ice jams, which can lead to flooding.

The board said that, despite this, 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-cubic-meters-per-second, or 740-cubic-meters-per-second above the previous January record set in 1987.

Despite what the board termed “unprecedented” outflows, Lake Ontario rose during January as record net total supplies into Lake Ontario averaged 10,140-cubic-meters-per-second. The high inflows were largely the result of heavy rainfall that rapidly increased stream flows during and following the Jan. 11 and Jan. 12 storm, the board said. 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, according to the board, is that water levels have begun to rise from their seasonal low, reached in December, and Lake Ontario’s level was at 246.49 feet as of Thursday 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.

Flows through the Moses-Saunders dam were temporarily reduced starting Friday as ice has begun to re-form in the Beauharnois Canal. The board said it will continue to 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.”

Johnson Newspapers 7.1

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