Watersheds - Chicago/Calumet
USGS Cataloging Unit
The Chicago/Calumet watershed in northeastern Illinois and northwestern Indiana is part of the Illinois River basin. With drainage from three Illinois counties, the Illinois portion of the watershed has a total area of approximately 580 square miles. The Chicago/Calumet watershed is the most populous major watershed in Illinois, containing an estimated 3.3 million people. Residential and urban areas are the primary use of land within the watershed, but there are a few agricultural areas to the far south and some forested lands scattered throughout it.