CORNWALL, Ont. – Water outflows have been reduced at one of the main control dams on the St. Lawrence River system for the first time since mid-June.
The International Lake Ontario-St. Lawrence River Board dropped the outflow at the Moses-Saunders Dam in Cornwall to 9,910 cubic meters (349,970 cubic feet) per second just after midnight this morning (Tuesday).
It had been at 10,400 cubic meters (367,300 cubic feet) per second since June 14 – an unprecedented level for the dam controlling water coming from Lake St. Lawrence, the St. Lawrence River and Lake Ontario.
The board notes the new flow is still a “record high for that time of year” but reduced it in the interest of public safety, shoreline landowners and commercial shipping and recreational boating.
Lake Ontario has dropped 30 centimeters (12 inches) since peaking in late May, but the lake is still above the International Joint Commission’s high level threshold.
Lake St. Lawrence (the section dammed between Cornwall and Iroquois) is actually “well below average” because the outflows from Lake Ontario into the St. Lawrence River cause Lake St. Lawrence to be drawn down.
The river board has to strike a careful balance because continuing to leave higher outflows at the Cornwall dam, while Lake Ontario is dropping would cause a dangerously strong current for shipping for points west of Iroquois all the way to the mouth of Lake Ontario, which includes the section of the river through Leeds-Grenville.