What is a Watershed?
A watershed is a specific land area, which can be identified by tracing a line along the highest elevations between two areas on a map (often a mountain ridge or divide) within which water flows to a common body of surface water (i.e., stream, river, lake, or ultimately, the ocean). Surface water is comprised of shallow ground water discharges (i.e., springs or seeps) and runoff from precipitation events. Please view the watershed diagram below.
Click here for larger diagram.
However, a watershed also includes the ground water that lies beneath the land surface and is associated with the surface water bodies, called ground water. Ground water infiltrates into the underlying soils and rocks. The underground boundaries of the ground water that discharge into the surface water body do not necessarily correlate to the surface topography and boundaries of the watershed; rather they are directly related to the underlying geology (rocks and soils) of the area.