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Impact of lake levels on river uncertain


With the deadline for input on proposed changes to water level management on Namakan and Rainy Lakes coming up Friday, those downstream of the dam at Fort Frances are wondering what all this will mean for the river.

And it’s a question Jennifer Mercer hasn’t been able to get much of an answer to.

The ecologist in charge of the Rainy River First Nation’s watershed project, Mercer said the International Joint Commission’s Rainy Lake Board of Control has been looking at the effects of adjusting the rule curves on Namakan and Rainy Lake.

Its study was prompted by a report from the Rainy Lake and Namakan Reservoir Level International Steering Committee back in November, 1993.

The board of control’s final status report, published last March, covered several studies from several viewpoints, Mercer said, including hydrologic modelling, environmental data summary, and an evaluation of economic/social and recreation factors.

But other than a change in the average water level, Mercer said little to no work has been done on what impact this would have on the river’s plant and animal life.

Under the proposed rule curve change, Rainy River would see an average drop of 0.51 m below current levels in March, 0.2 m in April and May, 0.32 m in June, and 0.16 m in July.

Those are straight vertical drops, Mercer stressed, noting the increase in shoreline is bound to be greater.

“Spawning activity occurs in March, April, and May and that’s when we’re seeing our water levels drop,” she added. “We don’t know how much fish habitat we’re going to lose.”

But fish habitat isn’t the only unknown, Mercer said. Water velocity could be lost, spawning beds could be reduced, and “predation” could increase.

“Say you’re a baby walleye,” she said. “You’re fish food for other fish. That’s predation. The water level decreases, you have less places to hide [and] you have greater chances of being eaten.”

Mercer stressed these were all “unknowns” and wouldn’t necessarily happen with a new rule curve. But she believed a hydrographic study of the river, particularly of the spawning areas, would give people a better idea of how the river would respond to water level changes.

John Van den Broeck, a Ministry of Natural Resources biologist for the Rainy River/Manitou area, has been in contact with Mercer on the subject.

“We’re working towards a project with the Rainy River First Nations and the Department of Natural Resources [Minnesota] to evaluate the spawning substrate at three sites,” Van den Broeck said.

“The technology we’re using . . . gives you a bottom contour at a fine resolution that we can use to evaluate spawning substrate,” he added, noting he hopes to get the project approved by spring.

Van den Broeck agreed the MNR wasn’t sure what the impact on downstream habitat would be if water levels on Rainy Lake and Namakan changed.

Meanwhile, it isn’t definite the rule curves will change. Rudy Koop, an advisor/geographer with the IJC in Ottawa, said it will be getting a report this spring from the board of control and expects some recommendations.

“Depending on what those recommendations are, the [IJC] will, of course, have to look at those and make a decision,” Koop noted. “Whether it’s going to change the rules curves or not, it can’t say now.”

Meanwhile, Mercer is trying to contact municipalities on both sides of the river to advise them of the situation. Her hope is the IJC will allow for a more in-depth study on the river before changing anything upstream.

“Maybe the water level drop isn’t big,” Mercer said. “We don’t know. No one can tell us.

“Possibly the rule curve changes might be the best-case scenario,” she admitted. “The problem is, we don’t if this is the best-case scenario.”

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