The advance of the invasive Asian carp up the Illinois River and into a canal leading toward Lake Michigan is leading many in the Great Lakes region to consider whether the man-made waterways connecting the Great Lakes and Mississippi River watersheds should be cut off.

Public officials in the Great Lakes states, including Chicago Mayor Richard Daley, say the time has come to consider re-reversing the flow of the Chicago River and closing off the canals linking it to the Illinois and Mississippi rivers.

Legislation proposed by members of Congress from Great Lakes states calls on the U.S. Army Corps of Engineers to expedite a study into hydrological separation of the two important basins. Plans would likely include re-reversing the flow of the Chicago River back into Lake Michigan, after the river was reversed more than a century ago in an engineering feat many say was remarkable at the time.

Josh Ellis, a water resources project manager for the Metropolitan Planning Council, a nonprofit in Chicago, explains that the Chicago River by Wolf Point is where the north and south branches of the river meet. From this point, the river used to flow east into Lake Michigan.

“And what used to flow back to the lake, now and for the last hundred years or so, flows southwest and ultimately to the Mississippi and the Gulf of Mexico.”

What was the water here like a century ago?

“Let’s just say I don’t think we would have wanted to be in the river at that point,” Ellis says.

According to Ellis, sewage, stormwater, snow melt-off and stockyard run-off drained into the Chicago River, which flowed out into Lake Michigan, polluting the city’s source of drinking water.

“And people were getting sick. Outbreaks of typhoid, cholera and other diseases were common. People were dying,” Ellis says.

Re-Engineering The Chicago River

In the late 1880s, local leaders decided to re-engineer the river. They reversed the flow and built a 28-mile-long canal to connect the Chicago River with the Des Plaines River, which leads to the Illinois and Mississippi rivers. With the river’s flow reversed, Chicago could flush its wastewater down toward Peoria, Ill., and St. Louis.

The diversion of the Chicago River was a remarkable engineering feat for its time, and the construction of the Chicago Sanitary and Ship Canal opened a vital transportation link between the Great Lakes and the Mississippi River.

But the canal also opened up a highway for invasive species to move between ecosystems that had never before been connected.

“If you set out with a goal of causing an invasion, there’d be no better way to do it than to build a hundred-foot-wide channel with free-flowing water and let a fish loose and see where it goes. And that’s what we’ve got here in Chicago,” says Joel Brammeier, president of the nonprofit Alliance for the Great Lakes.

Brammeier says electric barriers designed to jolt approaching fish into turning back may not be enough to keep Asian carp from advancing through the canal and up the Chicago River.

“If those fish come through the industrial part of the southwest side of Chicago, they end up [at Wolf Point] and downtown, and … it’s just a hop, skip and a jump into Lake Michigan,” Brammeier says.

Back To Nature?

That’s why Brammeier’s group and others from neighboring Great Lakes states are calling for the Mississippi and Great Lakes watershed to be re-separated and disconnected by creating a barrier in the canal. The plan would also call for re-engineering the Chicago River to flow back into Lake Michigan as it did more than 100 years ago.

According to Brammeier and others, a permanent barrier closing the link between Lake Michigan and the Illinois River would not just keep Asian carp from moving between the watersheds, but also other invasive species.

Round gobies, zebra mussels and scores of other invasive species have already traveled through the connection, wreaking havoc on ecosystems in lakes, rivers and streams all across the country.

“If you don’t have the connection, you don’t have the threat from Asian carp or any other invasive species,” Brammeier says.

As an added benefit of re-reversing the Chicago River, much of the water Chicago-area residents take out of Lake Michigan could be returned to the lake, instead of being flushed down to the Gulf of Mexico.

“Illinois gets to divert 2 billion gallons of water a day from the Great Lakes and send it away, never to be seen again,” says Brammeier, adding that “pulling water out of the Great Lakes and not sending it back is not sustainable.”

Changing the Chicago River’s flow would also force the Metropolitan Water Reclamation District of Greater Chicago to disinfect the treated but still bacteria-laden sewage it now dumps into the Chicago River — something many environmentalists say is long overdue.

The Cost Of Going Back

But none of this would be easy.

According to Richard Lanyon, executive director of the Metropolitan Water Reclamation District, separating the watersheds could sever a vital transportation link.

“This lock here at the mouth of the Chicago River is one of the busiest in the world with all of the recreational traffic,” says Lanyon. “And we have a lock out on the Calumet River, [and] the O’Brien Lock and Dam, which carries a lot of commercial traffic. A lot of commodities pass though that system.”

In addition, he says the entire stormwater sewer system for Chicago and 50 surrounding suburbs would have to be overhauled to prevent severe flooding.

“Without the opportunity to discharge to the lake during extreme storm situations, yes, you would have to have more infrastructure to convey water away from the city,” says Lanyon.

Add to that the billions he says it would cost to disinfect Chicago sewage, the massive cost for engineering and construction, and the fact that creating permanent separation between the watersheds would likely take years to complete. Lanyon questions whether it’s worth it to keep a breed of fish at bay.

“We haven’t found any Asian carp in our waterway system, so I’m not sure they’re here,” says Lanyon, adding that he thinks the Asian carp threat is “overblown” and “much ado about nothing.”

Advocates say hydrological separation between the Great Lakes and the Mississippi River produce many more benefits than just stopping Asian carp. It would also lead to cleaner water and conserve more of it in the Great Lakes.

The U.S. Army Corps of Engineers is now studying how and where to possibly sever the watersheds, and its cost and impacts.

But a federal judge in Chicago could step in and order the closing of the connection between Lake Michigan and the Mississippi as soon as the end of October, in response to a lawsuit filed by Michigan and other states that are seeking to keep Asian carp out of the Great Lakes. Copyright 2010 National Public Radio. To see more, visit http://www.npr.org/.