Balancing act when it comes to lake level

DAVE JOHNSON

POSTMEDIA NEWS

Water levels on Lake Ontario were at their highest Monday since records started being kept in 1918, says Gail Faveri, secretary of the Canadian Section of the International Lake Ontario-St. Lawrence River Board.

“It was 75.85 metres — three centimetres higher than the record in June 1952,” said Faveri, adding the readings come from an average of seven gauges in Ontario and New York.

As of 3 p.m. Wednesday, she said the outflow from Lake Ontario was increased to 9,200 cubic metres per second to alleviate flooding on both sides of the border.

Earlier in the day, the outflow from the lake, through 32 turbines at the Moses Saunders Dam between Cornwall, Ont., and Massena, N.Y, was 8,900 cubic metres per second.

“Last week, the outflow was 6,670 cubic metres per second for the whole week.”

Outflows from Lake Ontario are adjusted according to the inflow of water from Lake Erie and various rivers, creeks and streams in the watershed. An outflow of 300 cubic metres per second over a week would only change the level on Lake Ontario by one centimetre, but would increase levels on lakes Saint-Louis and Saint Pierre in Quebec by 10 to 12 centimetres

Faveri said the board must be conscious of what conditions are downstream, on the St. Lawrence River and the two lakes in Quebec.

“If we added more flow into the St. Lawrence, we would be damaging people further downstream. We have to balance what we do.”

Many municipalities along the St. Lawrence between Kingston and Cornwall, below Cornwall, and in areas of Quebec along the river and lakes have already experienced flooding damage, thanks in part of heavy rainfall throughout April.

“There are a lot of people underwater. It’s been an exceptional year.”

With the Ottawa River feeding into St. Lawrence River at Lake Saint-Louis at all-time highs on May 8, the board was unable to increase the outflow from Lake Ontario.

“As the Ottawa River goes down, we’re able to release more from the lake. We’re happy about the Ottawa River not delivering a lot any more.”

Faveri said the turbines at Cornwall and Massena, there are 16 on each side of the border, are very accurate when it comes to controlling the outflow.

Even with the release of more water, Faveri said there’s still a large inflow coming from Lake Erie through Niagara Falls and the Welland Canal. Lake Erie water levels are also above average.

“We don’t have control of what comes over Niagara Falls.”

She said even a small amount of rainfall can cause the lake levels to rise. Fifteen millimetres of rain can cause as much as a fivecentimetre rise in water levels, and that’s not factoring in runoff from throughout the basin.

While the amount of water being let out of the lake was increased Wednesday afternoon, Faveri said it could increase to as much as 10,000 cubic metres per second, which would cause problems for shipping on the St. Lawrence Seaway between Cornwall and Montreal.

St. Lawrence Seaway Management Corp. issued a mariner’s notice about the increased outflows from the lake and the effect it could have on vessels.

“These flows will create velocities higher than normal in the navigation channels and variations in the normal current patterns may occur. Mariners are advised to take these conditions into account when transiting the Montreal-Lake Ontario Section,” the Seaway said in its notice.

It has already issued a few notices on speed reductions on the lake and other areas of the seaway due to high water levels.

“If the board determines that it is necessary to increase outflows to above 10,200 cubic metres per second, it will be necessary to suspend navigation intermittently prior to which another notice will be issued. Mariners are to operate at the lowest safe speeds to minimize their wake, particularly when navigating close to shore.”