No matter where you are, you're in a watershed. Chester County's land area consists of portions of 21 watersheds that ultimately drain to the Delaware Bay or Chesapeake Bay.

A watershed is the area of land (catchment area) that captures rain and snow, and then stores, filters, seeps or drains this water into a common water body (marsh, stream, river, or lake). A watershed includes the network of streams that drains that surface land area, and the groundwater and aquifers located underground that contribute water to those streams.

Watersheds are separated from adjacent ones by a continuous ridgeline that forms the watershed’s boundary. Watersheds come in all shapes and sizes and can be broken down into subwatersheds (or subbasins). Each water body has its own watershed; some are millions of square miles in size; others are just a few acres.