Watersheds of Illinois facts for kids

A watershed is like a giant funnel! It's an area of land where all the rain and snowmelt drain into one main river, lake, or ocean. Think of it as a big neighborhood where all the water flows to the same place. The state of Illinois has many watersheds, and understanding them helps us know where all the water goes.

Long ago, before many changes were made, almost all of Illinois's water flowed into the mighty Mississippi River. Only a small part near Lake Michigan drained into the lake. But over time, people built canals and changed how water flows, especially around Lake Michigan. Now, some of the water from Lake Michigan can even connect to the Mississippi River system!

Even though most of Illinois is now part of the huge Mississippi River watershed, it's helpful to divide the state into smaller watersheds. This makes it easier to find specific rivers and streams. The way Illinois is divided into watersheds is based on a system used by the Illinois State Water Survey. This system helps us locate any body of water in the state.

Some smaller rivers and streams flow directly into the Mississippi River or the Ohio River. These are called "direct tributaries." They are considered part of the larger "Mississippi watershed" or "Ohio watershed" in this system, even if they have their own names.

This article lists the main watersheds in Illinois. You can also use it with the List of rivers of Illinois to learn more about each river and where it fits in the water system.

Mississippi River Watershed

The Mississippi River is one of the longest rivers in North America. A huge part of Illinois drains into this river. Here are the main rivers that are part of the Mississippi River watershed in Illinois:

• Ohio River
  • Cache River
  • Saline River
  • Wabash River
    • Little Wabash River
    • Embarras River
    • Vermilion River (Wabash River tributary)
• Big Muddy River
• Kaskaskia River
• Illinois River
  • Macoupin Creek
  • La Moine River
  • Sangamon River
  • Spoon River
  • Mackinaw River
  • Kickapoo Creek
  • Vermilion River (Illinois River tributary)
  • Fox River (Illinois River tributary)
  • Des Plaines River
  • Kankakee River
    • Iroquois River
• Rock River
  • Green River (Illinois)
  • Kishwaukee River
  • Pecatonica River

Smaller Rivers Flowing into the Mississippi

Many smaller rivers and streams in Illinois flow directly into the Mississippi River. These are also part of the "Mississippi watershed":

• Marys River
• Wood River
• Edwards River
• Henderson Creek
• Hennepin Canal
• Plum River
• Apple River
• Galena River
• Sinsinawa River
• Little Menominee River
• Menominee River

Lake Michigan Watershed

The Lake Michigan watershed is much smaller in Illinois compared to the Mississippi River watershed. It includes rivers that originally flowed into Lake Michigan.

• Lake Michigan
• Calumet River
• Chicago River

The Chicago River's Journey

The Chicago River is special! It used to flow into Lake Michigan. But in 1900, engineers changed its direction. They made it flow away from the lake and towards the Mississippi River system. This was done to help with sanitation and shipping. Now, the Chicago River is a small outlet of the Great Lakes Basin. Its flow is carefully managed by the U.S.-Canadian Great Lakes Commission.