Scott Forbes estimates flood damage at $2 billion and says most of it could have been prevented if there had been better drainage
Like the problem child in the family, Lake Winnipeg gets all the attention over its phosphorus problems, while its well-behaved smaller sister to the west tends to be ignored.
Or at least that was the case for Lake Manitoba until last year, said Scott Forbes, a professor of biology at the University of Winnipeg, who began studying the lake’s history after his cottage at Twin Beaches was wiped out.
“What happened was really astonishing, because Lake Manitoba’s water level has been remarkably constant for the last half-century,” Forbes said.
The lake, which has been effectively regulated by the Fairford water-control structure since 1961, has rarely stepped outside of its long-term average of 810 to 812 feet above sea level. Last year’s peak of just over 817 feet, a result of water levels of the Souris and Assiniboine rivers peaking just weeks apart, was “off the charts,” he said.
Forbes estimates the total damage around the lake and tributaries at $2 billion — 10 times what it would have been had the engineers who installed the Portage Diversion had the foresight to put in a drain on the back end of the lake.
The new seven-kilometre-long channel, being built at a cost of $100 million, is only a partial solution, said Forbes. It only will drain excessive flows from Lake St. Martin down the Dauphin River into Lake Winnipeg during the winter, he said. In summer, flows out of Lake Manitoba are hindered by the limited capacity of the Fairford channel. Its maximum flow rate of 17,000 cubic feet per second is “tiny” compared to the Portage Diversion’s 34,000 cf/s, said Forbes.
“When they opened the Portage Diversion last year, the levels in Lake Manitoba went straight up because it overwhelmed the capacity of Fairford,” he said.
Forbes said there are three possible solutions and he favours creating a second five-kilometre-long outlet channel south of Fairford that would follow a natural course of bogs and marshes from Watchorn Bay on Lake Manitoba to Lake St. Martin.
“It would have made a lot of sense to excavate it over the winter,” he added.
The Watchorn Bay channel outflow wouldn’t equal the Portage Diversion’s inflow, but wouldn’t have to, he said. If high water in spring is expected, then lake levels could be gradually dropped over the winter in preparation.
“We knew last spring there was going to be high water,” he added. “If we’d had the outflow capacity, we could have dropped the lake level to create extra room for the water.”
Until the province comes up with an effective solution, Forbes said he would be reluctant to rebuild his cottage. For now, he’s tearing down existing structures and clearing up the mess.
In an email, a spokesperson with Manitoba Agriculture, Food and Rural Initiatives stated the emergency channel dug last fall is working.
“As predicted, the emergency channel has allowed the Fairford structure to operate at maximum capacity all winter bringing down Lake Manitoba by almost four feet from its peak last July,” the official stated.