The Upper Octoraro Watershed includes the parts of Chester County and parts of Lancaster County in Pennsylvania that drain to the Octoraro Reservoir. The Octoraro Reservoir is the main source of drinking water for Chester Water Authority, which supplies water to more than 40,000 customers in 33 municipalities in the City of Chester, Western Delaware County, and Southern Chester County.

The entire Octoraro Watershed spans 208 square miles and has a population of about 45,000. It encompasses two states (PA and MD) and three counties (Lancaster PA, Chester PA, and Cecil MD). It includes many agricultural communities as agricultural land use makes up about 60% of the landscape, while forested land makes up 24% and developed land is 13% of the Watershed. While recognizing the critical role that farming plays in the Octoraro, agricultural activities can also have unintended consequences as stormwater runoff can carry pollutants such as sediment or soil, excess nutrients, pesticides, fertilizers, and bacteria into local waterways. As these pollutants can cause serious health concerns, the Watershed has been designated a Pennsylvania Department of Environmental Protection Priority Area.