Watershed Programs Homepage

To protect the water resources of the Commonwealth, it is increasingly important to use an integrated, comprehensive watershed approach with our environmental management programs.

What is a watershed?

A watershed is an area of land from which all water, sediments, and dissolved materials drain into a common outlet. When precipitation occurs, water runs to the lowest point -- usually a stream, river or lake. On its way to the lowest point, the water crosses over surfaces of forest land, suburban land and urbanized areas, or it may simply seep into the soil and travel through an aquifer. Everything that happens to a watershed can affect what ends up in the water. In natural areas with trees and other vegetation, water is slowed down as it makes contact with the vegetation. In addition, the vegetation helps to filter out pollutants and decreases surface erosion. In urbanized areas many vegetated/natural surfaces are replaced with impervious cover (or surfaces that do not allow water to soak into the ground). Impervious covers cause precipitation to flow swiftly toward the water low point and also can create floods due to rapid runoff.