A watershed is all of the landscape that drains into a particular
lake or river. The Illinois State Water Survey (ISWS) divided Illinois into
33 major watershed basins.
Joliet falls within the Des Plaines River Watershed on this map.
In addition, smaller sub watersheds have specialized groups that the City participates in including; the Hickory Spring Watershed, The Lower DuPage Watershed, the Aux Sable Watershed.