How Low Can it Go? The Ups and Downs of Water Levels on the Great Lakes

Nov. 26, 2003

If you think water levels on the Great Lakes are low now, then consider what they were like 9,500 years ago when they were 230 feet lower.
Talk about messing up your shoreline property. Back then, Lake Michigan was less than half its present size and the last of the Ice Age glaciers was retreating north through Canada. A gorge ran through the Mackinac Straits. In fact, the contour of Lake Michigan was so profoundly smaller than what it is today that geologists refer to that period of the lake‘s natural history as the time of Lake Chippewa.
Moral of the story? Things change, especially when it comes to the rise and fall of the Great Lakes.
“People think that the Great Lakes are low now, but Lake Michigan was even lower in 1964 and we‘ve got eight inches to go before we reach the level of back then,“ notes Mike Jacobson, who teaches environmental science, geography and meteorology (“basically dirt, rocks and weather“) at Northwestern Michigan College.
Jacobson has been following lake levels for years, keeping track of the latest reports from the U.S. Army Corps of Engineers. “The Corps monitors the lakes for shipping interests because you can‘t run freighters if you don‘t have enough water to float them,“ he says with a smile.
As a science instructor, Jacobson has a front row seat for some of the most dramatic fluctuations in lake levels in modern times. He notes that for purposes of study, the Corps of Engineers considers Lake Michigan and Huron to be a single body of water. The level for Lake Michigan/Huron is seven inches below what it was last year, 22 inches below the average for November, and 60 inches below the record high set in 1986. And yet, as low as the lake levels have dipped, they are still eight inches higher than they were in 1964.
“The lakes have fluctuated in the past and this up-and-down stuff is nothing new,“ Jacobson says.

SANDS OF TIME
Over the past few years, lakefront owners around the state have been in an uproar over falling water levels, which have left them with mucky, weed-tangled shores. The Save Our Shoreline movement has sought to overturn environmental legislation which prohibits property owners from rototilling the mess in order to reclaim beaches.
It‘s a subject which stirs Jacobson‘s ire. “What are they trying to save us from, our natural processes? Everybody owns the beach -- it‘s in the public domain.“
He says that shoreline fluctuations are a normal part of the lake‘s natural history. A satellite photo of Traverse City reveals ancient ridges of sand penetrating deep inland where the bay‘s boundary used to be. Jacobson notes that as the bay retreated thousands of years ago, new vegetation trapped sand, creating new beach ridges. That same process is in evidence today.
Present-day politics trumped natural history in June, however, when Governor Granholm okayed legislation that allows property owners to mow weeds down to a level of two inches without a permit from the Department of Environmental Quality (DEQ), as long as the roots and soil aren‘t disturbed. You can also pull weeds by hand, rake the beach for trash, and create temporary walkways or paths to the beach.

LONG TERM TRENDS
For lakefront property owners, only time will tell whether such grooming measures are a losing battle. Going back far beyond modern times, things get really interesting in terms of the Great Lakes‘ dramatic ups and downs. Through the millennia, Lake Michigan has gone through several transformations as the following ancient lakes:
• Lake Chicago existed more than 12,000 years ago and had a high-water mark of 620 feet above sea level, compared to 577 today.
• During the period of Lake Algonquin some 11,000 years ago, most of the lake was covered by a 5,000-foot-thick sheet of glacial ice.
• During the Lake Chippewa period of 9,500 years ago, the weight of retreating glaciers was so great on the continent north of here that it literally drained much of present day Lake Michigan and Huron of their water.
• Lake Nipissing of 4,000 years ago began to resemble the Great Lakes we know today, but was nearly 30 feet higher.

WHAT NEXT?
If retreating glaciers caused the rise and fall of prehistoric Lake Michigan, what‘s the problem today?
“It‘s a combination of a bunch of factors,“ Jacobson says. Those factors include how much inflow there is into the lakes in terms of rain, snow and groundwater; and how much outflow there is in terms of evaporation and water leaving the lakes via rivers or diversion.
“A lot of people want to blame municipal users for the lower lake levels, but the water used by communities goes right back into the water,“ he notes. Similarly, some feel that water diversion in the Chicago area is the culprit, since the city diverts up to 3,200 cubic feet per second. But that‘s a myth, Jacobson says, because even Chicago‘s constant diversion amounts to only about one percent of the total loss of Great Lakes water.
“The real problem is that over the past few years we‘ve had below-normal precipitation. There have also been increases in lake temperatures have have meant less ice cover on the Great Lakes. The loss of ice cover means there‘s more evaporation. We‘ve also had a below-normal snowpack over the past few years, and that runoff plays a big role in lake levels.“
Lake Superior, a powerhouse when it comes to supplying the lower lakes with water, is warmer now and evaporating.
“Global warming is the big question,“ Jacobson says, adding that there‘s still controversy as to the extent of global warming‘s impact. “What the long term effects of that will be, we don‘t know, but if it does get warmer, it‘s likely that the lakes will drop even more.“

A MYSTERY
What does the future hold for lake levels? The Army Corps of Engineers will make predictions only six months out; at this point, the Corps predicts that the lakes will rise somewhat.
But beyond that, it‘s anyone‘s guess. Jacobson notes that a researcher in the ‘70s predicted today‘s lake drop-off with remarkable accuracy. There have also been computer models, predicting rising temperatures in the Great Lakes region for the next century.
Using computer projections known as the Hadley Model, researchers in the United States forecast that the average winter temperature will rise by five degrees in the Great Lakes region by the end of the century. A Canadian computer model predicts an increase in winter temperatures by as much as 10 degrees. Based on those models, U.S. researchers claim there will be a 50% loss in lake effect snow by the 2090s, while Canadian researchers predict a 90% loss in snow.
If those predictions hold true, it could mean a drop in lake levels for decades to come. Then again, as Jacobson notes, there have been water diversions in Canada which have actually increased the volume into Lake Superior. And who would have predicted during the high-water crisis of 1986-‘87 that we‘d endure the exact opposite problem 15 years later?
We‘ll just have to wait and see which way the water runs.

For a closer look and the latest information on lake levels, check out the Army Corps of Engineers, Detroit District website at www.lre.usace.army.mil.