The Chicago Area Waterways System would experience the effects of a possible separation between the Mississippi River basin and Lake Michigan. Charles Melching developed a model to evaluate those effects under two different scenarios.
Water Resources Institute Research
By Aaron Conklin
It’s one of the biggest crises facing the Great Lakes in the modern era, and Charles Melching finds himself right in the middle of it.
Or, perhaps more accurately, behind the scenes of it. Backed by funding from the U.S. Army Corps of Engineers (Corps), through the University of Wisconsin Water Resources Institute, Melching, an environmental consultant and former pro- fessor at Marquette University, is using a computerized model to predict what will happen to the water flow—and water quality—in the Chicago Area Waterways System (CAWS) if the Corps reseparates the Mississippi River basin from Lake Michigan within the CAWS. This hydrologic separation is one of the alternatives proposed to permanently prevent aquatic nuisance species, including the invasive Asian carp, from colonizing and potentially ravaging the lake’s ecosystem.
The model’s known as DUFLOW, and it’s designed to map out the hydraulic and water quality properties of the entire river system, including predicting how flows and water quality might fluctuate when sewage systems overflow in cases of heavy rainfall. Melching, who developed the model in conjunction with Marquette University for the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC), will be looking at two separation scenarios and a baseline “without project” scenario.
According to Melching, the major factor influencing the baseline scenario is the MWRDGC’s and Corps’ plans to open two reservoirs to store combined sewer overflows along the Chicago and Calumet rivers. By 2017, it is anticipated that one reservoir will be fully operational while the other will be partially operational.
The first separation scenario involves building a barrier between the Lake Michigan basin and the Mississippi River basin near the current Lake Michigan diversion points on the North Shore Channel at Wilmette, Il., the Chicago River in downtown Chicago, and Calumet River at the O’Brien Lock and Dam in southeast Chicago. This scenario is similar to the “closing of the locks and gates” advocated by Great Lakes states governors to the federal courts, and it may have significant effects on potential flooding
in the Chicago area.
The second separation scenario involves reestablishing the natural divide between the Lake Michigan basin and the Mississippi River basin near the beginning point of the man-made Chicago Sanitary and Ship Canal.
“In this scenario, we’re saying we’ll let the original Chicago and Calumet rivers (and the effluent from two large wastewater treatment plants) drain back to Lake Michigan,” Melching explained. “Everything else, including the majority of the pumpback of captured and treated combined sewage, will go to the Mississippi River basin.”
This scenario, while accomplishing the goal of blocking Asian carp from reaching Lake Michigan through the waterway, will have a far more dramatic effect on the water quality of both the CAWS and the lake.
“The big question is, if we do this, how much of a pollutant load is going into Lake Michigan?” asked Melching.
Melching and his team are still months away from answering that question—in fact, they only submitted their initial model results to the Corps in February, with a full draft report due in June. He’s quite aware of the public scrutiny his work will generate.
“It’s interesting. All the work I’ve done in the waterway prior to this project was dealing with conditions as of now,” said Melching. “Now I’m looking at what’s projected to happen in the future. Can we properly characterize the changes in a logical, defensible way?”
As Melching knows, the health and survival of the Great Lakes ecosystem may depend upon it.