What is a Watershed?
A watershed is an area of land where all precipitation that falls in it and drains off of it goes to a common outlet (creek, river, body of water). Watersheds can be as small as a footprint or large enough to encompass all the land that drains water into rivers that drain into Chesapeake Bay, where it enters the Atlantic Ocean. As defined by John Wesley Powell, a scientist geographer, a watershed is “that area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community.” Unlike the geographic boundaries which define the township, borough, state, or even the country in which we live, watersheds know no boundaries.
The East Branch of Indian Creek flows through Narberth, Lower Merion Township, and Philadelphia before its waters join Cobbs Creek and enters the Delaware River. Mill Creek flows through Lower Merion and joins the Schuylkill River upstream of Manayunk.