The land area whose runoff drains through a single stream is called that stream's DRAINAGE BASIN.  The area outside the Roney Building at GSW, for instance, provides runoff to the small stream that drains College Lake, and so is in the drainage basin of that stream.  That stream feeds Willet Creek a few dozen meters downstream and so we are also in the Willet Creek drainage basin.  Willet Creek is tributary to Mill Creek, Mill Creek to Muckalee Creek, Muckalee to the Flint River, and the Flint to the Appalachicola, which drains into the Gulf.  The Roney building therefore sits in the drainage basin of each of these streams in turn.

The high ground that separates two drainage basins is called a DRAINAGE DIVIDE.  The Pelham Escarpment (a hill which one climbs south of Cordele on I-75) separates the drainage basins of the Apalachicola system from that of the Suwannee system, and so is the drainage divide between those basins.

How water drains out of an area depends upon the bedrock geology of that area.  There are numerous patterns that drainage systems follow; we will examine only four of them as summarized in the diagram below.  The next page shows examples and discusses each in more detail.