By Jeff Kart
January 13, 2011
Regulating Great Lakes water levels isn’t as easy as adjusting a few knobs.
Members of the International Upper Great Lakes Study Board have been examining historical data on the variability of water supplies and outflows in the lakes. They’ve found that most of the time, the supply and outflow can be balanced. But that’s only on average. The ups and downs in between mean it’s important for the public to understand that regulation is a balancing act, rather than a sure-fire way of controlling lake levels.
The regulation of the water flow from Lake Superior at Sault Ste. Marie has a relatively small effect on Lakes Michigan-Huron, explains Al Steinman, director of the Annis Water Resources Institute at Grand Valley State University, and a member of the Study’s Public Interest Advisory Group (PIAG).
“The surface area of Michigan-Huron is 45,300 square miles,” said Steinman, also a member of the Study’s Ecosystems Technical Working Group. “So if you’re talking about trying to distribute water out of Superior over that surface area, it’s going to be muted.”
In essence, regulating the flow of water from Lake Superior into Michigan-Huron is akin to trying to move a swimming pool through a straw, into another, larger swimming pool. “There’s only so much you can do,” Steinman added.
Members of the Study Board and PIAG have been analyzing different methods to regulate the flow from Lake Superior as they prepare a proposed plan for the International Joint Commission, to be submitted some time in 2012.
“The relationship is not symmetrical,” Steinman said. “By changing the regulation schedule, you can have a noticeable influence on water levels in Lake Superior. But you can only have a relatively modest impact on Michigan-Huron, even at the extremes.”
The influence of Mother Nature, in terms of variation in climate, is a much larger influence on the levels of Michigan-Huron than the Lake Superior regulation schedule, he added.
By the numbers, there’s not much to work with in terms of water supplies and outflow capacity, adds David Fay, the Canadian member of the International Lake Superior Board of Control.
“The best we can do is hope to balance it out,” Fay said. “And it’s important to stress that anything we do affects the whole system.”
For instance, the amount of water delivered to Lake Superior per month by Mother Nature has varied from 32 to minus 9 centimeters. The minus means there was more evaporation than precipitation and runoff to the lake that month.
The outflow of water from Lake Superior has varied from 12 to 4 centimeters per month. That outflow is limited, based on the capacity of structures at Sault Ste. Marie. With all the structures flowing at full capacity, 12 centimeters of water can be removed from Lake Superior per month. To provide a minimum amount of hydropower generation and water for ships passing through, a flow equivalent to at least 4 centimeters off Lake Superior is needed.
“So you can see, the range outflow capacity of all the works at the Soo is much less than the range in the water supplies to Superior,” notes Fay. “It’s that difference between the water supply to the lake and the outflow that causes the lake level to vary.”
The monthly outflow that takes 12 to 4 centimeters off Lake Superior adds only 8 to 3 centimeters to the larger surface area of Lake Michigan-Huron. Precipitation and local runoff minus evaporation to Michigan-Huron, by comparison, has varied from 31 to minus 12 centimeters, and the outflow through the St. Clair River has historically removed from 15 to 7 centimeters of depth from Michigan-Huron, Fay said.
On average, this all works out: The Superior basin supply and Superior outflow are both 7 centimeters. The total of the water added to Michigan-Huron from Superior and the Michigan-Huron supply equals 12 centimeters, and the outflow from Michigan-Huron adds up to the same 12 centimeters.
Besides the variation in supplies, the same regional weather systems often affect all the upper Great Lakes at the same time, Fay said. “Typically, there are dry conditions over the lakes at once, or wet conditions over the lakes at once. This gives you less flexibility.”
In a new regulation plan, officials will try to take advantage of improved forecasting, perhaps using increased or decreased pre-releases of water to better balance the lakes, Fay said.
Members of the International Upper Great Lakes Study Board have been examining historical data on the variability of water supplies and outflows in the lakes. They’ve found that most of the time, the supply and outflow can be balanced. But that’s only on average. The ups and downs in between mean it’s important for the public to understand that regulation is a balancing act, rather than a sure-fire way of controlling lake levels.
The regulation of the water flow from Lake Superior at Sault Ste. Marie has a relatively small effect on Lakes Michigan-Huron, explains Al Steinman, director of the Annis Water Resources Institute at Grand Valley State University, and a member of the Study’s Public Interest Advisory Group (PIAG).
“The surface area of Michigan-Huron is 45,300 square miles,” said Steinman, also a member of the Study’s Ecosystems Technical Working Group. “So if you’re talking about trying to distribute water out of Superior over that surface area, it’s going to be muted.”
In essence, regulating the flow of water from Lake Superior into Michigan-Huron is akin to trying to move a swimming pool through a straw, into another, larger swimming pool. “There’s only so much you can do,” Steinman added.
Members of the Study Board and PIAG have been analyzing different methods to regulate the flow from Lake Superior as they prepare a proposed plan for the International Joint Commission, to be submitted some time in 2012.
“The relationship is not symmetrical,” Steinman said. “By changing the regulation schedule, you can have a noticeable influence on water levels in Lake Superior. But you can only have a relatively modest impact on Michigan-Huron, even at the extremes.”
The influence of Mother Nature, in terms of variation in climate, is a much larger influence on the levels of Michigan-Huron than the Lake Superior regulation schedule, he added.
By the numbers, there’s not much to work with in terms of water supplies and outflow capacity, adds David Fay, the Canadian member of the International Lake Superior Board of Control.
“The best we can do is hope to balance it out,” Fay said. “And it’s important to stress that anything we do affects the whole system.”
For instance, the amount of water delivered to Lake Superior per month by Mother Nature has varied from 32 to minus 9 centimeters. The minus means there was more evaporation than precipitation and runoff to the lake that month.
The outflow of water from Lake Superior has varied from 12 to 4 centimeters per month. That outflow is limited, based on the capacity of structures at Sault Ste. Marie. With all the structures flowing at full capacity, 12 centimeters of water can be removed from Lake Superior per month. To provide a minimum amount of hydropower generation and water for ships passing through, a flow equivalent to at least 4 centimeters off Lake Superior is needed.
“So you can see, the range outflow capacity of all the works at the Soo is much less than the range in the water supplies to Superior,” notes Fay. “It’s that difference between the water supply to the lake and the outflow that causes the lake level to vary.”
The monthly outflow that takes 12 to 4 centimeters off Lake Superior adds only 8 to 3 centimeters to the larger surface area of Lake Michigan-Huron. Precipitation and local runoff minus evaporation to Michigan-Huron, by comparison, has varied from 31 to minus 12 centimeters, and the outflow through the St. Clair River has historically removed from 15 to 7 centimeters of depth from Michigan-Huron, Fay said.
On average, this all works out: The Superior basin supply and Superior outflow are both 7 centimeters. The total of the water added to Michigan-Huron from Superior and the Michigan-Huron supply equals 12 centimeters, and the outflow from Michigan-Huron adds up to the same 12 centimeters.
Besides the variation in supplies, the same regional weather systems often affect all the upper Great Lakes at the same time, Fay said. “Typically, there are dry conditions over the lakes at once, or wet conditions over the lakes at once. This gives you less flexibility.”
In a new regulation plan, officials will try to take advantage of improved forecasting, perhaps using increased or decreased pre-releases of water to better balance the lakes, Fay said.