Your NPR news source

Floods, Carp, And Crap: The Environmental Impacts Of The Chicago River Reversal

SHARE Floods, Carp, And Crap: The Environmental Impacts Of The Chicago River Reversal
River Reversal Thumb Updated

Katherine Nagasawa

The reversal of the Chicago River in 1900 has been celebrated as not only an inspired solution to a vexing problem, but an engineering marvel. But little did anyone understand at the time how long the effects might linger, how far they might ripple and how controversial they might prove to be.

Thanks to its location at the southern tip of Lake Michigan, Chicago was a booming commercial hub by the end of the 19th century. But as the city grew, so too did its sewage problem. The Chicago River, once a shallow stream teeming with life, began to function more like a common gutter. It captured the waste of more than 1.5 million people (not to mention the growing stockyards), flushing it directly into Lake Michigan — where Chicago also sourced its drinking water.

In 1885, a violent storm flooded the river and belched a huge plume of sewage into the lake. It also inspired civic leaders to propose a radical new solution:

“Rather than clean up our act,” says Josh Mogerman, national media director at the Natural Resources Defense Council, “we decided we’d do something audacious and reverse the river and send our poo down to St. Louis instead.”

This much listener Eric Seidelman knew. But he’s always wondered what happened next, particularly downstream. So he wrote to Curious City, asking:

What was the environmental cost of reversing the direction of the Chicago River?

The reversal of the Chicago River in large part succeeded, and has mostly protected Lake Michigan from Chicago’s sewage, “preventing thousands of people from dying from a rogue’s gallery of waterborne illnesses,” as Mogerman puts it. Yet it was hardly a perfect solution. In the years and decades that ensued, the bold maneuver has flooded farmland downstream, opened the gates for new invasive species, and polluted areas as far south as the Gulf of Mexico.

Expanded river turns farmland into “frog ranch”

The complications piled up downstream almost immediately. The influx of water from Lake Michigan nearly doubled the size of the Illinois River, eroding the banks and swallowing farmland and wildlife habitat up and down the valley, writes Richard Cahan in The Lost Panoramas: When Chicago Changed Its River And The Land Beyond.

By 1905, nearly 300 landowners in the Illinois Valley filed suit against the Sanitary District of Chicago. In one especially prolonged case, three sisters who inherited their father’s farm near Eureka, roughly 100 miles southwest of Chicago, sued for $40,000 in damages.

Before the opening of the canal, they raised “the best crops in the world,” one sister boasted from the stand in December 1910. “We had so much corn we didn’t know what to do with it.” But now, she claimed, the sisters grew little more than cattails, buck brush, and water weeds. When it wasn’t flooded, she testified, their field was rough with crawfish holes and littered with debris that had floated down the river: wooden rails, pieces of boats and fish nets.

Asked by the defense attorney what other use the land could be put to, she dryly replied, “A frog ranch…That is it.”

Farmers soon began constructing levees to reclaim their land and, by 1929, Cahan writes, a total of 200,000 acres in the Illinois Valley floodplain had been manipulated by drainage and levee districts.

There was no going back.

“A wave of poo” heads downstream

Many communities downstream also considered the reversal a threat to public health. In 1900, Missouri filed a suit against the Sanitary District on behalf of St. Louis, arguing the reversal of the Chicago River would eventually pollute the Mississippi, where it sourced its own drinking water. It was the first pollution case tried in U.S. Supreme Court, but it was ultimately dismissed. For one, Missouri was unable to prove the pollution in the Mississippi came from Chicago. Missouri’s allegations rested “upon an inference of the unseen,” wrote Justice Oliver Wendell Holmes. And the hypocrisy didn’t help: St. Louis was sending its own waste downstream.

“If we are to judge by what the plaintiff itself permits,” Holmes wrote, “the discharge of sewage into the Mississippi by cities and towns is to be expected.”

Nevertheless, Mogerman says, it’s easy to understand Missouri’s concern.

“A wave of poo coming down from this giant metropolis is something to be less enthusiastic about,” he says.

Soon, fish in the Illinois River could also feel the effects of the polluted water. In the beginning, they thrived in their expanded environment. “But as pollution increased,” and as sewage solids gradually made their way downstream, Cahan writes in The Lost Panoramas, “the oxygen level in the water dropped, killing them off or forcing them into cleaner tributaries.”

Around 1920, Chicago and other cities finally began treating their sewage. But progress was slow and the technology was primitive. It wasn’t until the 1970s, following passage of the Clean Water Act, that rivers really began to recover. Since then, the number of fish species found in the Chicago River, for example, has increased nearly ten-fold, from less than 10 to more than 70 today.

Treated sewage contributes to a growing ‘dead zone’

But environmental groups say the work to mitigate the damage caused by the Chicago River reversal is hardly finished ⁠— and its effects can be found as far away as the Gulf of Mexico. That’s because when heavy rains flood the sewers, untreated wastewater still gets released directly into the river. And though it’s hardly unique to Chicago, even when the system does work properly, the discharge released into the river contains phosphorus at levels that are harmful to marine life.

While some of Chicago’s phosphorus is absorbed by various biological and chemical processes along the way, a portion of it eventually makes it all the way down the Mississippi River and into the Gulf, where it helps feed the growth of massive algal blooms. As the algae decomposes, it consumes the oxygen in the water ⁠— a process called “hypoxia”⁠— rendering these areas uninhabitable to marine life. Scientists call these areas “dead zones,” and they estimate the Gulf’s dead zone (roughly 5,300-square-miles on average) to be the second largest in the world.

Make no mistake: agricultural runoff (i.e. fertilizer) is by far the major culprit. But Chicago’s wastewater today is one of the largest single contributors of phosphorus pollution in the dead zone. It’s a fact environmental groups are quick to point out.

But, while the Metropolitan Water Reclamation District of Greater Chicago (MWRD), Chicago’s wastewater treatment authority formed in 1889 to oversee the reversal of the river, doesn’t entirely deny its contribution, it says quantifying individual sources is a “futile exercise.”

“The fact is whether you are spreading fertilizer on your lawn or flushing your toilet, we are all contributing to the Gulf Dead Zone,” writes Allison Fore, Public and Intergovernmental Affairs Officer for the MWRD. “Along the more than 1,400 river miles between the Chicago Area Waterway System and the Gulf of Mexico, nutrients are taken up by aquatic organisms and cycled through biological and chemical processes, so the extent to which nutrients from the Chicago metropolitan area actually reach the Gulf of Mexico is not certain.”

Regardless, Mogerman points out that Chicago’s wastewater doesn’t just affect the Gulf.

“This isn’t something where we make a mess in Chicago and it just comes out at the other end. We see algal blooms in the Illinois River, in the Des Plaines River, the whole way down,” he says.

The MWRD has been steadily working to cut its discharge levels over the past decade. In 2017, it agreed to a settlement with a host of environmental groups, including the Natural Resources Defense Council and Friends of the Chicago River, that will significantly reduce its phosphorus output even more by 2030. Though many environmental groups would prefer an even greater reduction, they say it’s a start.

New pathway opens for invasive species

The Chicago River reversal also connected two of the world’s largest freshwater ecosystems: the Great Lakes and the Mississippi River Basin. In doing so, we created a new pathway for invasive species.

Among them is the Asian carp. The invasive fish first escaped containment ponds in Alabama in the early 1970s, and by the ’90s, they were eating and breeding their way up the Mississippi, outcompeting native filter-feeders like Bigmouth Buffalo and Gizzard Shad and disrupting ecosystems along the way. They’ve since been found just miles outside of Chicago.

The Army Corp of Engineers is currently awaiting congressional approval for a $831 million plan to halt their spread through a system of electric barriers and underwater noisemakers. But many in the northern Great Lakes states, where sport and commercial fishing are still big business, are fearing the worst.

“Not only do the Asian carp undermine the ecology, they cause huge economic damage,” says Joel Brammeier, president and CEO of the Alliance for the Great Lakes, a non-profit environmental advocacy organization. “So, of course, when they eat all the food out of the water, and they breed better than any other fish, that totally undermines the native fishery those tourism economies are depending on.”

Is a re-reversal in our future?

In recent years, the Alliance for the Great Lakes and others have floated yet another bold idea: Construct a permanent barrier to disconnect the watersheds, in effect re-reversing the Chicago River.

“The surest way to stop critters from moving back and forth between these watersheds,” Brammeier says, “is to stop water from moving back and forth.”

But re-reversing the river would require a monumental upgrade to our current sewage treatment system. Without it, the city would essentially recreate its original problem.

“All the water that gets discharged into the river would have to be clean enough that we would all be okay with it going into Lake Michigan,” he says. “Today that’s not the case … We’ve got a lot of years and a lot of money between here and there.”

According to the Army Corp of Engineers, re-reversal would cost upwards of $18 billion dollars. In other words, don’t hold your breath.

“Well it’s a very novel idea, but not very practical,” says Dick Lanyon, former MWRD executive director and author of Building the Canal to Save Chicago. “We changed the basic plumbing here in Chicago, and to reverse that would be a Herculean task.”

Then again, if we did it once…

More about our questioner

He no longer remembers who told him. Or when, exactly — or why. But somewhere along the way, Aurora-native Eric Seidelman, 32, a navigator for new students at the College of DuPage, learned that Chicago had reversed its river. He understood the basics of damming a river; how creating the Hoover Dam backed up the Colorado, for example, forming Lake Mead.

“But I’d never really heard of rivers changing direction and the environmental effects that would have,” he says, “how that would affect the new downstream.”

After learning what we found, he says, “the word that comes to mind … is monstrosity.”

“I say that not only because of the sheer size of the undertaking you describe to reverse the flow of the river, but also the size of the impact, and the blindness I’d say most Chicagolanders have to the ever-compounding issues the Chicago River has caused.”

In truth, he says he feels “like an ant,” mostly powerless to affect change himself. But he hopes local politicians will take these issues more seriously moving forward, and prioritize the river’s health. Perhaps he’ll write them a letter urging them to “take true responsibility.”

“We made it,” he says, “and we’re culpable for the outcome of its continued harm.”

Editor’s Note: Richard Cahan, who is quoted in this story, is the husband of WBEZ editor Cate Cahan.

Carson Vaughan is a freelance journalist and the author of “Zoo Nebraska: The Dismantling of An American Dream.” Follow him @carsonvaughan, or visit his website at

More From This Show
Chicago’s geological history stretches back more than 400 million years. The region was once an underwater reef and, later, covered in ice.
Native Americans have always lived in Chicago, but in the mid-20th century they established a cultural enclave in Uptown, anchored by community centers and social connections.