'Highest ever' outflow from Lake Ontario into St. Lawrence begins

CTV Montreal: Opening the dam Water levels in Lake St. Louis may rise as water flow increases through the Moses-Saunders Dam

Water levels along Lake St. Louis and the St. Lawrence river will rise as more water from Lake Ontario is being released through the Cornwall dam.

As of noon on Wednesday, more water from Lake Ontario is pouring into the St. Lawrence River than ever before.

The flood mitigation strategy is being implemented for three days as an emergency measure because Lake Ontario is experiencing record water levels this spring. Experts said it will likely take months to lower the lake to its normal level.

The International Lake Ontario-St. Lawrence River Board came up with the plan on Monday. .

It determined it would increase the flow through the Moses-Saunders Dam by 200 cubic metres per second to 10,400 cubic metres per second “in order to increase the rate of decline in Lake Ontario levels slightly and provide additional relief to Lake Ontario riparians,” it stated in a Facebook post.

This increase is being allowed now that floodwaters in Quebec have finally receded--even as water levels in Lake Ontario have flooded beaches, homes, and forced the closure of the Toronto Islands.

“This will be the highest Lake Ontario outflow that has ever been released on a sustained basis,” the post read.

Rob Caldwell of the Board said Lake St. Louis is "currently at 22.19 metres above sea level which is 14 centimeters below flood stage."

He anticipated water levels in Lake St. Louis would rise seven to eight centimetres.

The measure will be in place for three days as a trial period while authorities find out if ships can navigate the waters.

"It takes a whole lot of consideration, deliberation, weighing of benefits and impacts," said Caldwell.

Kerry Gillings, the owner of Marine Ste. Anne, is concerned about the impact that more water will have on riverside properties.

"Boaters that are currently using the waterways now have to be a little more aware because of the water height because of the wake of the boat. They should be more courteous for their neighbours as they're going along on the waterways," said Gillings.

The board said boaters on the St. Lawrence River should be cautious of the extreme conditions, although it does not expect that the measure will "have any significant effect on St. Lawrence River levels near Montreal as declining Ottawa River flows are expected to continue, and this will offset the effects of the increased Lake Ontario outflow.”

In many cases recreational boaters have had to wait to put their boats into the water because the docks and ramps were underwater, and anchorage has been limited

"It has a huge impact on the yacht clubs at the moment because there's a lot of yacht clubs that still have not been able to launch their boats," said Gillings.

The mayor of Ste. Anne de Bellevue, Paola Hawa, said although there was flooding in her city earlier this spring, she is not concerned about more flooding as a result of the dam being opened.

She said officials will be monitoring water levels in the days to come.

Cargo ships will be forced to slow down and captains will be required to monitor the wakes their ship produce in order to ensure that dikes are not swamped.

Shipping schedules will also be affected by the measure.