Chicago River Flowing Backwards Would Be Least of Region's Concerns

Photographer: George Rose/Getty Images

Trump Tower and the Wrigley Building along on the Chicago River. The worst U.S. drought since the 1930s is lowering the level of Lake Michigan, which in theory could reverse the flow of the Chicago River. Close

Trump Tower and the Wrigley Building along on the Chicago River. The worst U.S. drought... Read More

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Photographer: George Rose/Getty Images

Trump Tower and the Wrigley Building along on the Chicago River. The worst U.S. drought since the 1930s is lowering the level of Lake Michigan, which in theory could reverse the flow of the Chicago River.

The headlines were alarming: "Drought Could Reverse Flow of Chicago River," hailed the website of WLS-TV, the local ABC News affiliate. "Ongoing Drought Could Send the Chicago River Flowing in Reverse," read Smithsonian magazine's normally sedate web pages. 

It turns out, a backwards flow may be the least of the river’s concerns.  

Here’s the scenario: the worst U.S. drought since the 1930s is lowering the level of Lake Michigan, and if it drops another 6 inches or so this winter, it could fall below the level of the Chicago River. That means the dirty waters of the Chicago River, which were diverted 100 years ago to preserving the relatively pristine lake, would be sucked backwards. 

In practice, three sets of locks that divide the river from the lake would only allow a relatively small amount of river water to leak back into the lake when the locks are opened to ships, says Margaret Frisbie, executive director of Friends of the Chicago River. It’s roughly the equivalent of putting a thimbleful of dirty water into a bathtub. 

The bigger concern is that if the flow from the lake stops, so too does the flow of the Chicago River. The lake water that currently flushes the Chicago River and its burden of treated and untreated sewage through the Des Plaines and Illinois rivers into the Mississippi would stop flowing, temporarily transforming swaths of the Chicago River into a lifeless, de-oxygenated bog. 

The future of the river’s health is now in question, with the lake at its lowest point since accurate record keeping began.

"If you live around lot of water you don’t think of it as a precious resource," says David St. Pierre, executive director of the Metropolitan Water Reclamation District of Greater Chicago, the city's sewage utility. "Conservation is a conversation that’s just started to happen in the Chicago region."

The river spilling backwards into the lake wouldn’t be unprecedented. About once a year, heavy rains threaten to push the river over its banks and the locks are opened, reversing the river's flow for a day or less, with little ill effect, Fribsie says. She notes that water treatment plants have made the river far cleaner today than it was just two decades ago. 

The Great Lakes usually rise about a foot to 14 inches from snowmelt and runoff every spring. Last year, Lake Michigan rose only 4 inches. By last month, Lake Michigan and Lake Huron above it were 28 inches below the long-term average. 

Waterways made Chicago. Then Chicago remade its waterways. Engineers reversed the Chicago River a century ago to use the lake’s water to refresh the waterway. The future of the river’s health is now in question, with the lake at its lowest point since accurate record keeping began in 1918.

"There's more evaporation, less precipitation falling on the lakes and less runoff making it to the lakes," says Keith Kompoltowicz, chief of watershed hydrology for the Great Lakes with Army Corps of Engineers in Detroit. Just how permanent the shifts are is hard to know, he says. "We don’t even 100 years of data yet so it's impossible to determine if there are in fact cycles of low water and high water."

Like so many of the systemic challenges we face these days -- in financial markets, in public health, with climate change -- what happens to the short-term flow of the Chicago River over the next couple months may be just a shadow of the elevated risks we’re courting over the next couple of decades. 

"It’s a micro-story in a much larger problem of what we are doing to the environment,” says Frisbie. “One of the U.S.'s great water resources is vanishing."    

Analysis and commentary on The Grid are the views of the author and don't necessarily reflect the views of Bloomberg News. 

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