A Great Lakes Adventure: Managing Water Levels (Dammed If You Do)

Muskrat surrounded by cattails. Courtesy of R. Town/USFWS
It's spring on Lake Ontario and, for a group of scientists and engineers from the U.S. and Canada, the annual headache can begin. The International St. Lawrence River Board of Control has the unenviable power of regulating Lake Ontario’s water levels. Higher levels make boaters and shipping companies happy, because they literally float their boats. But for lakefront homeowners, high water means watching waves steadily erode their backyards. If the board decides to keep levels lower, homeowners rejoice as the water recedes, but boats are left high and dry and shipping vessels must skim tons of cargo from their holds to float higher in the water.
As Frank Sciremammano knows, finding the water-level sweet spot is elusive. Sciremammano, an engineering professor at the Rochester Institute for Technology, is one of the five American members of the 10-member Board of Control, and he admits it’s a tough assignment - shippers will always want more water and homeowners will always want more shoreline.
But there is another resident of the lake that depends on “just right” water levels. The muskrat, which is nearly ubiquitous in the wetlands of the other Great Lakes (and throughout North America in general), is a rare sight on the shores of Lake Ontario. Its absence has to do with winter water levels, says Doug Wilcox, a professor of wetland science at Brockport State University of New York.
Doug Wilcox talks with IJNR fellows near Cape Vincent, NY.
Photo by Adam Hinterthuer

Wilcox and Sciremammano recently spoke to a group of journalists participating in a fellowship of the Institutes for Journalism and Natural Resources, a non-profit dedicated to getting journalists out in the field and up-close to environment stories. Standing amid tussocks of sedge grass and stands of cattails in a marsh near Cape Vincent, New York, he explained that muskrats have evolved to take advantage of steady winter water levels. They make mounded dens out of dirt and cattails and then dig a tunnel with an underwater entrance. When the lake and its marshes ice over, the muskrat spends winter underneath the ice cap, venturing out of its tunnel into the deeper, unfrozen water to find food. They often chew holes in the ice and create mini-lodges called “push-ups” that serve as rest stops during long swims.

Lake Superior and Ontario are the only Great Lakes with human-regulated water levels. Ontario’s levels are primarily controlled by retaining or releasing water via the Moses-Saunders hydroelectric dam on the St. Lawrence River. Since 1960, the Board of Control has kept water levels within a range of 243.3 to 247.3 feet. Those levels are set by the International Joint Commission (IJC) to better serve human interests on the lake. The IJC was formed by the 1909 Boundary Waters Treaty to mediate water-use conflicts between the U.S. and Canada.
Because boaters and shippers don’t use the lake in winter, the smart economic move is lower lake level by releasing more water through the Moses-Saunders dam, which consequently generates more electricity. But doing that effectively drops the water right out from under the muskrats that have settled in under the ice cap,, stranding them in their lodges and cutting them off from their “push-ups” and food sources.
A cascade of consequences ensue. For example, Wilcox says, during winter, muskrats chew pathways through the cattails that, in the spring, become important channels for spawning northern pike, a top predator of the Lake Ontario food web and popular sport fish. And marshes without muskrats can be overrun by cattails, meaning there’s less open water for ducks and geese, which often nest in such wetlands.
The good news, Wilcox says, is that muskrats could quickly rebound should their environmental needs be met. A single pair can have up to twenty-five offspring a year. A few good winters of the right water level would equal a population boom. But Wilcox knows landowners, sport fishers and shipping companies have more political pull than a march-dwelling rodent. Still, he hopes his research will be one more thing the Board of Control considers before opening the floodgates next winter.

Second Post in a Series:


Coming soon: The Curious Case of the American Eel.

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