What's a River Basin? What's a Watershed?

What is a River Basin?

A river basin is the portion of land drained by a river and its tributaries. It encompasses all of the land surface dissected and drained by many streams and creeks that flow downhill into one another, and eventually into the Milwaukee River.  The final destination is than an estuary which eventually carries it to Lake Michigan. As a bathtub catches all the water that falls within its sides, a river basin sends all the water falling on the surrounding land into the Milwaukee River, then to Lake Michigan and eventually the Atlantic Ocean.

As an artery connects the parts of a body to one another, so a river threads together the creeks and streams, valleys and hills, lakes and underground springs that share a common assembly of water. Whatever happens to surface or groundwater in one part of the river basin will find its way to other parts. If water is diverted out of its downward course in one section, other parts will come to "know" of its absence. A river basin comes closer than any other defined area of land, with the exception of an isolated island, to meeting the definition of an ecosystem in which all things, living and non-living, are connected and interdependent.

What is a Watershed?

A watershed is simply the area of land that catches rain and snow and drains or seeps into a marsh, stream, river, lake or groundwater. 
 

What is the difference between a River Basin and a Watershed?

Both river basins and watersheds are areas of land that drain to a particular water body, such as a lake, stream, river or estuary. In a river basin, all the water drains to a large river. The term watershed is used to describe a smaller area of land that drains to a smaller stream, lake or wetland. There are many smaller watersheds within a river basin.