Driving back to Missouri from a wedding in Cincinnati, my wife and I took the "southern route," coming across Interstate 64 from Louisville to St. Louis. After crossing the broad Ohio River and undulating through the hills of the Hoosier National Forest, in southern Indiana, the highway enters relatively flat terrain north of Evansville and soon crosses the Wabash River to begin its trek across south-central Illinois; surprisingly, that 150 mile segment of the Interstate only crosses two rivers large enough to warrant highway signs, the Little Wabash in southeast Illinois and the Kaskaskia River in southwest Illinois, though a handful of creeks are also recognized.
Bordered on the west by the Mississippi and on the south by the Ohio, Illinois sends almost all of its water toward the Gulf of Mexico; while the Eastern Continental Divide passes through Chicago, canals link the Chicago and Calumet Rivers (which formerly emptied into Lake Michigan) with the Des Plaines River, which flows southward into the Illinois River, thus disrupting the Divide. The latter river, formed by the convergence of the Fox, Des Plaines and Kankakee Rivers, drains a broad swath of the State, from its northeastern corner to the St. Louis area, where it empties into the Mississippi. Northwest Illinois is drained by the Galena, Apple, Rock, Green and Edwards Rivers (north to south), all flowing westward to the Mississippi. In west-central Illinois, the Vermillion River rises from several tributaries and then flows southeastward to the Wabash (the largest northern tributary of the Ohio), while the Kaskaskia begins its long journey southwestward to the Mississippi and the Little Wabash snakes southward to the Ohio. Finally, the Big Muddy River and a host of smaller streams drain the Shawnee Hills of southern and southeastern Illinois, most flowing toward the Ohio River, itself a massive tributary of the Mississippi.
In landscapes with prominent ranges or dramatic relief, it is usually easy to visualize the component watersheds; but in a relatively flat expanse of terrain (which defines most of Illinois), one must pay close attention to subtle divides and maps to fully understand the regional hydrology. Of course, the river networks of Illinois are, in large part, the product of glacial erosion and meltwater flow, acting on the underlying geology.
Bordered on the west by the Mississippi and on the south by the Ohio, Illinois sends almost all of its water toward the Gulf of Mexico; while the Eastern Continental Divide passes through Chicago, canals link the Chicago and Calumet Rivers (which formerly emptied into Lake Michigan) with the Des Plaines River, which flows southward into the Illinois River, thus disrupting the Divide. The latter river, formed by the convergence of the Fox, Des Plaines and Kankakee Rivers, drains a broad swath of the State, from its northeastern corner to the St. Louis area, where it empties into the Mississippi. Northwest Illinois is drained by the Galena, Apple, Rock, Green and Edwards Rivers (north to south), all flowing westward to the Mississippi. In west-central Illinois, the Vermillion River rises from several tributaries and then flows southeastward to the Wabash (the largest northern tributary of the Ohio), while the Kaskaskia begins its long journey southwestward to the Mississippi and the Little Wabash snakes southward to the Ohio. Finally, the Big Muddy River and a host of smaller streams drain the Shawnee Hills of southern and southeastern Illinois, most flowing toward the Ohio River, itself a massive tributary of the Mississippi.
In landscapes with prominent ranges or dramatic relief, it is usually easy to visualize the component watersheds; but in a relatively flat expanse of terrain (which defines most of Illinois), one must pay close attention to subtle divides and maps to fully understand the regional hydrology. Of course, the river networks of Illinois are, in large part, the product of glacial erosion and meltwater flow, acting on the underlying geology.
