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The River Runs in Reverse.
Chicago Continues to Grapple with its Impact.
In 1900, the Chicago River was reversed to protect the city from disease and water pollution. Today, this decision poses questions to a city that faces unprecedented climate conditions and irreversible changes in the ecosystem.
One weekend in July 2023, a relentless rainstorm hit Chicago. The Chicago River’s water levels rapidly rose as the threat of overflowing wastewater loomed over the city.
In response, city officials opened a set of heavy steel gates, the Harbor Lock, that connects to Lake Michigan. This decision unleashed gallons of polluted water away from the city, into the lake. On Sunday, city officials temporarily reversed the flow of the Chicago River.
The Outer Drive Bridge and Chicago Harbor Lock on the Chicago River lead out to Lake Michigan. Image courtesy of Nicholas Hartmann via Wikimedia Commons.
“Reversed,” however, might be a bit misleading — in reality, the river was already running backward, and officials simply set it straight again (temporarily, at least).
Chicago is no stranger to hydrological dilemmas. In 1900, quite literally overnight, the city permanently reversed the flow of the Chicago River in an attempt to address the city’s wastewater challenges.
A lively scene. The commercial and recreational side of the Chicago River is located around DuSable Bridge and Michigan Avenue. Image courtesy of Siva Seshappan via Pexels.
Over a century later, the city is still grappling with the impact of this decision; managing the Chicago River’s water flow has been one of the city’s most pressing and omnipresent concerns. One of the most obvious consequences are the threats posed by severe storms and flooding, like those of July 2023. The reversal a century ago, however, also spurred a chain reaction of effects that are largely invisible to the average Chicago resident.
The geography of this juncture at the Chicago River and Lake Michigan shaped the city’s wastewater management. With flat, low and nonporous terrain, mid-19th century Chicago streets were covered in a septic, muddy skin. But the city faced challenges with designing a sloped sewer system that had enough tilt to feed into the river.
Fur trading on the banks of a river or lake at the settlement of Chicago, 1820. Image courtesy of the Library of Congress.
Chicago attempted its first engineering feat to solve the sewage situation in 1852. They built streets above existing streets, sandwiching sewers in between, ultimately altering Chicago’s natural topography and pulling it out of the swamp.
View of Rush St. Bridge & Nortons Block on the Chicago River, 1861. Image courtesy of the Library of Congress.
This costly attempt was largely a failure. While streets became cleaner, pollutants began seeping into Lake Michigan, the city’s water supply. Waterborne diseases such as cholera, typhoid and dysentery posed threats to the city population, killing around 1,500 .
The second daring attempt to solve the sewage problem was altering the river’s flow. In 1885, the Chicago Sanitary and Ship Canal was conceived, which would direct the Chicago River’s flow away from Lake Michigan rather than into it.
But first, an existing canal connecting the Chicago River to the Des Plaines River needed to be removed. With a blast, the junction’s canal was obliterated overnight using a dynamite explosion. What was left was a diluted open sewer.
"The Great Chicago Sewer," Bridgeport, 1871. The immediate impact of the reversal. Image courtesy of the Newberry Library.
In 1900, The Chicago Sanitary and Ship Canal opened, engineering the Chicago River to flow in reverse by standing lower than Lake Michigan.
Then, in 1938, the Harbor Locks were added: steel gates that separated lake water from river water. This construction helped solidify a cycle, sending waves of wastewater downstream and pumping Lake Michigan’s freshwater up into the Chicago River.
“The feat of reversing the Chicago River did protect the health of Chicagoans for decades by moving pollution away from the city, but it didn't actually address the root cause of the pollution,” Joel Brammeier, CEO of Chicago-based conservation group Alliance of Great Lakes , said.
With the river’s thriving tourism and recreation, it may not be immediately apparent that Chicago is still dealing with the consequences of the reversal. But this commercial and industrial activity is subject to the management of elevation and flow — a continuation of the original reversal.
The Chicago River is far from a simple waterway. It is an enormous maintenance project, reliant on large-scale hydrological technology and infrastructure.
McCook Reservoir Phase I. Image courtesy of Allison Fore via Wikimedia Commons.
In response to maintenance demands of the Chicago River, such as water level control and wastewater carrying, the Sanitary District of Chicago (now the Metropolitan Water Reclamation District of Greater Chicago) was formed in 1889. It was not until much later that the city started treating sewage.
The MWRD existed for 81 years before the Environmental Protection Agency, so the organization became a quasi-environmental public health agency.
“The public health angle of our work has been brought forth more than ever now, these last few years,” Patrick Thomas, MWRD public affairs specialist, said. “When people talk about essential workers, they don't tend to think about a water reclamation plant.”
Under the MWRD, infrastructure such as the 1972 Tunnel and Reservoir Plan ( TARP ) assists with flood control and pollution from sewer overflow. The plan consists of 109 miles of deep tunnels that have diameters of up to 33 feet.
The final stage of the Tunnel and Reservoir Plan (TARP) looks into the Thornton Reservoir. Images courtesy of Andrew Gill.
“It's really difficult to balance, to maximize the benefits of all those uses, because the river is being called upon to do a lot of different jobs,” Brammeier said. “In the ideal ... it becomes as close to a natural space as it can be given how heavily engineered it is.”
The reality of a recreational and industrial Chicago River is an experience that Chicagoans are starting to recognize as possible and are starting to demand, according to Brammeier.
The Chicago River also must work towards counteracting the intense weather events of climate change, the consequences of which threaten the integrity of the city itself.
The city relies on these technologies to control flooding, but with month-long dry periods and record-breaking rainfall, Chicago and its waters are facing unprecedented challenges.
With intensifying climate extremes and rising global temperatures will come more flooding risks and overflow crises. Storms will become more frequent, more severe, longer and larger.
During these storms, the river becomes a reservoir for combined sewage and stormwater. The commercial use of the river becomes secondary in these moments.
For example, McCook Reservoir, situated between the Des Plaines River and the Chicago Sanitary and Ship Canal on the southwestern side of Chicago, holds about 3.5 billion gallons.
It was filled in a matter of hours during the storm. In turn, the MWRD is adding another stage to the reservoir, of 6.5 billion gallons.
Continuous expansion, however, is not completely sustainable.
“We realized we can't just build our way out of this,” Thomas said. “It's going to be a matter of green infrastructure and the combination of both the gray and the green to manage this stormwater.”
A Chicagoland resident speaks to pressing infrastructural and community problems in a tweet after July 2023 flooding (@CipotadeChicago).
Planners at the Chicago Metropolitan Agency for Planning ( CMAP ) envision a similar future for maintenance projects around the river.
“[Green infrastructure] is a great way to not only capture some of the stormwater on-site, but [it] also helps with greening communities and adding vegetation, which can feed into things like urban heat island effects,” Kelsey Pudlock, a senior planner at CMAP, said.
Click to Enlarge. Grissom Elementary School on Chicago’s Southeast Side, before and after green infrastructure improvements. Images courtesy of the MWRD.
With larger storm events escalating with climate change, the focus of these organizations will shift. For example, CMAP anticipates that the financial allocation devoted to stormwater management will increase over time. Currently, that number rests at around 40% of their total budget.
“If we try to retain that water on-site through green infrastructure or other tactics, we could limit the amount of our diversion that's going to stormwater management, and potentially allow us to use that water in other ways,” Nora Beck, program leader for air quality and water resources at CMAP, said.
While surrounding areas are experiencing the consequences of Chicago’s decision, it is undeniable that the city itself is experiencing improved waterway health.
“When I first started monitoring there was about 10 fish species in the river. Now it's grown up to about 77, 60 of which have been found since 2000,” Thomas said.
TARP and other technologies employed at the water reclamation plants have supported a resurgence in water quality and biodiversity.
“Looking at the events that recently occurred, trying to manage the stormwater has improved water quality in the rivers,” Pudlock said. “So from an ecological standpoint, you're certainly seeing water quality improve over time.”
Closeup of cable crossing on the Chicago River. Image courtesy of Mobilus In Mobili via Wikimedia Commons.
Nonetheless, discrepancies still exist between municipal and local organizations on how the effects of the Chicago River reversal shape the city’s waterways today.
“It made Chicago utterly dependent on a highly engineered, completely artificial system of tunnels and reservoirs to move stormwater around,” Brammeier said. “It solved a problem at the time, but it also created some others.”
The diversion of water away from the Great Lakes has since been, essentially, banned. Both in the U.S. and Canada, any proposal to divert water — from or beyond the Great Lakes watershed — has to meet a very high standard.
“It's not something that we can turn back in history, but we can recognize that that kind of a diversion of water is not something we ever want to repeat,” continued Brammeier.
On the other hand, those at the MWRD view the reversal as a beneficial necessity in protecting the city of Chicago.
“I think there's nothing but positive things [from] reversing the flow of the river,” Thomas said. “[The river] is really our front yard, with the river improving to the point where now people don't really see it as the backyard to Chicago.”
Image courtesy of Dom Schvegman via Pexels.
Moving forward, Chicago is adapting to the ever-changing infrastructure of the river and the imminent challenges of a changing climate.
The river is a project that relies on the hard work of municipal organizations and is protected by the mindful efforts of local conservation groups.
“The same growth of modern engineering technology and expertise that enabled spectacular things such as reversing an entire river, also now enable us to do what we do,” Botts said, in regard to his wetland restoration work.
A large part of these organizations’ work also rests on the public eye and contributions of Chicagoans, from city officials to residents.
Sightseers along the Chicago River riverwalk. Image courtesy of Chris Rycroft via Wikimedia Commons.
“I had a friend who used to … lead people out on tours. She would often encounter people who were just completely oblivious to the river [being] reversed,” Beck said. “People are much more aware of the re-reversal when we have these big rain events and the implications for Lake Michigan.”
To raise public awareness, Friends of the Chicago River , an organization dedicated to improving the health of the Chicago River system, issues community action posts on social media. For example, their Overflow Action Days emphasize what everyday residents can do to mitigate their contributions to the water that enters the river system.
An Overflow Action Day Twitter post from Friends of the Chicago River (@chicagoriver).
“There are things like not running your dishwasher, not doing laundry, that can help with bringing up capacity in the system to allow for more rainwater to flow through,” Pudlock explained.
After all, the Chicago waterways are the heart upon which the city was built. The threat of the waters flowing backward below will inevitably shape the lives of the residents above.
“That's a big issue for Chicago. And it's kind of the issue for Chicago, I would argue in a way,” Botts said.
“It's not clear to me that Chicago's political and media leaders really understand that yet. Maybe it'll take a few more storms like [July’s] to drive the point home, but this is going to keep happening.”
South branch of the Chicago River against the city skyline. Image courtesy of Sea Cow via Wikimedia Commons.