A watershed is an areas of land where all the precipitation, rain and snow, drains to a common lake, stream or wetland. Watershed can be small or large. They cross geopolitical boundaries.
The Codorus Creek Watershed is located in York County, south central Pennsylvania. Geographically, the Codorus Creek drains 278 square miles into the lower Susquehanna River Basin, one of six subbasins in the river basin.
The Susquehanna River drains a total of 27,500 square miles, covering half the land area of Pennsylvania and portions of New York and comprises 43 percent of the Chesapeake Bay's drainage area.
The Chesapeake Bay -- the largest estuary in the U.S. -- is an incredibly complex ecosystem that includes important habitats and food webs. The Bay itself, its rivers, wetlands, trees and land all provide homes, protection or food for complex groups of species.