What is a watershed?
The land area that contributes runoff to a particular stream or drainage course is known as the watershed. Each watershed is comprised of multiple subwatersheds. Columbia lies in the Chesapeake Bay watershed and in the Patuxent sub-watershed. The portions of the Patuxent River watershed that Columbia lies in are called the Little Patuxent, the Middle Patuxent and Dorsey Run.
When we speak of the Columbia watershed, we are including the streams, lakes, plants, land use and living organisms throughout the local drainage areas.