Shippers say high water levels could wash away more than $1 billion in revenues

Rising water levels in the St. Lawrence Seaway could cost the economy more than $1 billion, shippers and port operators say.

A new study from the Chamber of Marine Commerce warns that opening the floodgates further at a dam in Cornwall, Ont., would wash away between $1 billion and $1.75 billion in revenue for businesses on both sides of the border.

A board of control recently increased the flow at the Moses Saunders Dam — the only control point on the St. Lawrence Seaway, which includes the Great Lakes — to allow 10,400 cubic metres of water per second out of Lake Ontario. The exceptionally high rate — equivalent to about four Olympic swimming pools going over the dam each second — follows heavy spring snow melt and rains and record water levels on several Great Lakes.

The rapid outflow interrupts navigation on the St. Lawrence Seaway, as swift, swirling currents near the dam slow ships’ movement through the locks, Bruce Burrows, president of the Chamber of Marine Commerce, said Wednesday.

“The approach is a delicate operation,” he said, noting the locks are 80 feet wide for ships with widths that range up to 78 feet. “You have to squeeze in tight.”

Burrows estimated it costs businesses up to $4 million every day the current outflow is in place. The International Lake Ontario-St. Lawrence River Board will next consider boosting the outflow this Friday.

“Any flow over 10,400 requires some kind of stoppage — either temporary stop-and-go or full stoppage,” he told The Canadian Press.

“It’s an incremental benefit in terms of additional water being taken out of the system. It pales in comparison to the economic hit,” he said, pointing to the diverse range of products carried on the Seaway including Prairie grain, Central Canadian steel and car parts.

Upping outflow to near the maximum of 11,500 cubic metres per second — more could impact the turbines at the hydroelectric dam — would prompt a sustained stoppage at the locks, six weeks of which would rob businesses of about $1.8 billion in revenue, Burrows said.

“This is a key international trade corridor…so I think this is a reputational issue as well.”

He approved of the current outflow — a heightened level that the board opted to maintain last week — due to flood problems for homeowners on Lake Ontario and the Thousand Islands, but called on Ottawa and the provinces for a study into water levels and their causes along with a water management plan.

Lake Ontario rose to nearly 90 centimetres above average this spring, reaching a record 75.92 metres above sea level before stabilizing. Lakes Erie and Superior also hit record heights.

Overflowing rivers took a toll on residents in Quebec and New Brunswick, where at least 17,350 homes were hit by flooding or deemed at risk, according to Statistics Canada.

“There are obviously natural cycles, you see that over the years…but this is the second time in two years that we’ve had a one-in-100-year event,” Burrows said.

“I think there’s a certain consensus that climate change is probably connected one way or the other.”

Christopher Reynolds, The Canadian Press