Water control authorities will open the taps to drain Lake Ontario as much as possible after the Great Lakes shipping season shuts down on Tuesday.

The International Lake Ontario-St. Lawrence River Board says it will “substantially” increase flows through the Moses-Saunders Dam at Long Sault “as much as possible” until ice formation on the St. Lawrence River forces it to reduce flows again.

In a statement Monday, the board said it hopes to increase flows to as much as 10,000 cubic metres per second – up from 8,850 – if water and ice conditions allow it.

The increased flows at the dam will see higher water levels downstream, including in the Montreal area, but the water level will be monitored closely to avoid flooding, the board said.

Despite record outflows from Moses-Saunders in 2019, Great Lakes water levels remain stubbornly high, it said.

In a look-back at its operations in 2019, the board said an unprecedented spring saw record water levels and flows across the Great Lakes and Ottawa River basins.

In response, the board said it opened the taps to record flows in June as Lake Ontario water levels reached a record high of 75.92 metres.

“High outflows from Lake Ontario continued through the summer, fall and early winter, resulting in more water released from Lake Ontario during the last seven months of 2019 than in any year since the start of records in 1900,” the board said in its statement.

The average outflow from June through December was a record 9,560 cubic metres per second, which is equivalent to removing nearly 30 feet of water from Lake Ontario during this time.

But as fast as the international dam authorities could release the water, Mother Nature was refilling Lake Ontario.

“With all of the Great Lakes seeing record or near-record water levels in 2019, inflows to Lake Ontario have also remained high during that time,” the board said.

As of Sunday, Lake Ontario’s level was 75 metres, which is well above seasonal averages.

And the outlook remains grim for residents and businesses on the water: “High inflows are expected to continue into 2020,” the board forecasts.

Although many property owners blame the International Joint Commission’s Plan 2014 for keeping water levels high, the IJC blames the weather, not its plan.

“The International Lake Ontario-St. Lawrence River Board, under authority granted to it by the International Joint Commission, will continue to deviate from Plan 2014 and will look for any and all opportunities to remove additional water from Lake Ontario prior to the spring,” the board said.

The milder winter so far is working in the board’s favour by keeping down the water in the river. Although an ice formation in the Beauharnois Canal two weeks ago forced the board to reduce its flows temporarily, the more recent mild temperatures allowed it to crank up the volume again.

The board says it will continue with the record volumes until the next cold snap causes the river ice to form again.

wlowrie@postmedia.com