Watersheds of Northern Chester County
The principle watersheds of Northern Chester County are French Creek, Pickering Creek, Pigeon Creek, Valley Creek and the East Branch of the Brandywine. Smaller watersheds include Stony Run and several unnamed tributaries which flow directly into the Schuylkill (Schuylkill Drainages). Over three quarters of the watersheds in Northern Chester County are designated as either Exceptional Value (EV) or High Quality (HQ); together they make up an intact region of healthy watersheds which is unique in Southeastern PA and notable at the state level.
These watersheds are uniformly recognized as being critically important environmental resources to our region and have special federal, state and local protections. The federal and state protections flow primarily from the Clean Water Act of 1972, which set the goal of making all surface waters “fishable and swimmable”.
Federal policy provides that Exceptional Value waters (“Tier 3”) maintains and protects water quality in Outstanding National Resource Waters (ONRWs). Except for certain temporary changes, water quality cannot be lowered in such waters. ONRWs generally include the highest quality waters of the United States. However, the ONRW classification also offers special protection for waters of exceptional ecological significance, i.e., those which are important, unique, or sensitive ecologically. Decisions regarding which water bodies qualify to be ONRWs are made by States and authorized Indian Tribes. Pennsylvania regulations add several additional pathways under which a surface water may be designated EV.
Federal policy provides that High Quality waters (“Tier 2”) maintains and protects “high quality” waters — water bodies where existing conditions are better than necessary to support CWA § 101(a)(2) “fishable/swimmable” uses. Water quality can be lowered in such waters. However, State and Tribal Tier 2 programs identify procedures that must be followed and questions that must be answered before a reduction in water quality can be allowed. In no case may water quality be lowered to a level which would interfere with existing or designated uses.
Northern Chester County’s EV and HQ “watersheds provide many ecosystem services that are necessary for our social and economic well-being. These services include water filtration and storage, air filtration, carbon storage, nutrient cycling, soil formation, recreation, food and timber. Many of these services have not been monetized and therefore the economic contributions of healthy intact ecosystems are often under-valued when making land use decisions. Ecosystem services provided by healthy watersheds are difficult to replace and most often very expensive to engineer (see chart). An engineered ecosystem service replacement may only provide a fraction of the services provided by highly functioning natural systems. Preventing impairments in healthy watersheds protects valuable ecosystem services that provide economic benefits to society and prevent expensive replacement and restoration costs. Maintaining riparian connectivity and natural processes in the landscape provide a supporting network for ecological integrity, ensuring the sustainable and cost effective provision of clean water over time”.
For more information on the process of designating a stream as EV or HQ, please visit the updated “Stream Designation Handbook”.
 North of latitude 40, which divides the county into roughly equal halves
 EV is a Pennsylvania term equivalent to the federal designation of “Tier 3”
 HQ is a Pennsylvania term equivalent to the federal designation of “Tier 2”
 U.S. Environmental Protection Agency. Water Quality Standards – Antidegradation Policy.
 U.S. Environmental Protection Agency. The Economic Benefits of Protecting Healthy Watersheds Fact Sheet. April 2012.