Myth: What Happens (and Pollutes) in Chicago Stays in Chicago

Think that since streams in Northern Illinois flow into Lake Michigan, Chicago’s water pollution remains local? Think again.

The Illinois River drains 11,000 square miles of our state, and draws water from three major river basins in the region. The river then flows west into the Mississippi River, not eastward towards Lake Michigan. Only water that flows across a very thin strip of Chicago’s shoreline runs directly into the lake.

Because waterways close to Chicago flow primarily away from the city and Lake Michigan, pollutants in these waters can become problems for our neighbors downstream. Pollution carried down the Mississippi into the Gulf of Mexico contributes to a notorious “dead zone”—an area of lifelessness in the Gulf that is now over 8,000 square miles.

Fortunately, in recent years, Chicago has cleaned up its water, enabling the city to become a better neighbor by sending less pollution downstream.

Exploring Deeper

The rivers and streams of the Chicago area drain water from large areas of land. Three significant basins form part of the watershed of the Illinois River: the Kankakee, the Fox, and the Des Plaines/Chicago Rivers. A watershed is the term for the geographical area drained by a single river.

Chicago is located close to a continental divide—water on one side flows east to Lake Michigan, water on the other flows to the west. Since most of the watershed of the Illinois River is west of the divide, that river forms part of the vast Mississippi River watershed.

With the reversal of the Chicago River in 1900, its waters have been artificially incorporated into the Mississippi watershed. The majority of our waterways flow away from the region bringing with them all residual pollutants remaining in these rivers. Good management in the watershed and of our rivers has local benefits but it also benefits a surprisingly large region of the United States and its coastal waters.

The Problem

When it was accomplished, the reversal of the Chicago River was one of the great engineering feats of its time. The project was undertaken with considerable urgency because the natural flow of the Chicago River resulted in its discharge into Lake Michigan.

Since the Chicago River was used as the sink for human sewage and for our industrial and commercial waste, this created an unwholesome environment for the young city. Not only were there problems with appalling smells but there were very grave health implications with water-borne diseases reaching epidemic proportions.

At that time, one can say that what happened in Chicago, stayed in Chicago—with deadly consequences. The reversal of the river was an attempt to export our problems, or at the very least, to dilute them in the larger watercourses of the Illinois and Mississippi Rivers. The story of the reversal of the river is an important illustration that when it comes to waterways there is no such thing as “local.” The impact in one part of a watershed can have consequences elsewhere.

Although modern sanitation and water treatment facilities have greatly decreased Chicago’s impact on other regions, we need to remain vigilant.

For instance, a recent review of environmental problems in the Gulf of Mexico indicates that hypoxia (the elimination of oxygen in the water), which is a consequence of the polluted water discharge from the Mississippi and Atchafalaya Rivers, has resulted in the world’s second largest dead zone.

The extent to which Chicago contributes to this problem is debatable. A recent study has suggested that Illinois is one of nine out of 31 states in the Mississippi and Atchafalaya River Basins that collectively contributes up to 75 percent of the nitrogen and phosphorus (the main sources of water pollution) to that watershed.


Water drains from the land into aquatic systems. Streams, rivers, lakes, and the sea are ultimately connected in a complex global hydrological system. Because land and water are interconnected, the management of land and water resources should be considered together. We can minimize adverse impacts both regionally and beyond by thoughtful practices that minimize polluted runoff from the land into waterways.

What You Can Do

Many of the practices discussed in last month’s Myth are relevant for minimizing Chicago’s impact on regions beyond ours.

  • Cover Bare Soil: Keep areas of bare soil in your yard to a minimum. Consider adding native groundcover plants or applying mulch products over the exposed soil.
  • Minimize Use of Fertilizer: Apply lawn and garden fertilizers only if soil tests indicate a specific need.
  • Dispose of Household Chemicals Properly: Help your municipal wastewater treatment plant discharge the cleanest water possible. Many household chemicals and pharmaceuticals are not able to be removed by the treatment plant, so rather than flushing them down the drain, keep them out of our rivers by disposing of them according to package directions. A good source for where you can dispose of household chemicals is Earth911.
  • Compost Produce Waste: In the kitchen, consider composing your fruit and vegetable waste instead of pushing it down the garbage disposal . If that’s not an option, then the garbage disposal is still way better than the trash can!. Some of the waste’s nutrients aren’t removed by the treatment plant, so it ends up “fertilizing” our river instead!
  • Support Clean Water Legislation: Support local ordinances and public policies designed to minimize the effects of urban development on river water quality. Check out the Metropolitan Water Reclamation District’s Cook County Stormwater Management Plan or the Lake County Stormwater Management Commission.

Written by Liam Heneghan, the Institute for Nature and Culture, DePaul University