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Water Quality Network

The Pennsylvania Water Quality Network (WQN) is a statewide, fixed station water quality sampling system operated by the Department of Environmental Protection's (DEP) Bureau of Clean Water. It is designed to assess both the quality of Pennsylvania's surface waters and the effectiveness of the water quality management program by accomplishing four basic objectives:

  • Monitor temporal water quality trends in major surface streams throughout the Commonwealth of Pennsylvania
  • Monitor temporal water quality trends in selected reference waters
  • Monitor the trends of nutrient and sediment loads in the major tributaries entering the Chesapeake Bay
  • Monitor temporal water quality trends in selected Pennsylvania lakes

Major streams, for the purposes of this Network, are considered to be interstate waters and intrastate streams with drainage areas of roughly 200 square miles or greater. These waters receive both point and non-point source pollutants and are sampled at or near their mouths to measure overall quality before flows enter the next higher order stream or before exiting the Commonwealth. In this way, trends can be established and the effectiveness of water quality management programs can be assessed by watershed.

WQN Stations

The WQN is comprised of three station types: Standard, Chesapeake Bay Nutrient Loading and Reference.

  • Standard stations are generally sampled bimonthly for stream discharge measurements and physical/chemical analysis and annually for a biological evaluation.
  • The Chesapeake Bay Nutrient Loading stations are sampled monthly for stream discharge measurements and physical/chemical analysis, and every other year for a biological evaluation. In addition to the monthly samples, Bay Loading stations are sampled 8 additional times per year during storm events.
  • Reference stations are sampled monthly for stream discharge measurements and physical/chemical analysis and once a year (spring or fall) for a biological evaluation.

In addition, approximately 90 lakes are scheduled for annual sampling in groups of 15-20. Lake groups are sampled once a year for five consecutive years before initiating a new group. The 5-year data blocks are then used to assess lake water quality trends.

Reference stations are selected to represent: 1) "ambient" waters minimally affected by human activities; and 2) "typical" waters with quality representative of that normally found in the region of the state being sampled.

Although it may be argued that Pennsylvania has no unaffected waters (by virtue of atmospheric deposition), reference stations (ambient and typical) reasonably describe water quality that could be achieved in the absence of point source discharges and in the presence of minimal or typical nonpoint source impacts. Thus, these stations can provide, in the absence of site-specific data, a benchmark for use in the water quality management permitting program as well as a measure of changing water quality in areas of the state not directly impacted by development.

Lakes included in the WQN (except for Lake Erie and Presque Isle Bay which are part of the base sampling network) are selected after consideration of size, public access, intensity of use and availability of existing data. Large lakes with heavy public use and/or historical data are favored for inclusion in this program because changing trends in the water quality of these resources have the potential for serious impacts on water uses.

WQN station locational information and descriptions of the physical, chemical, and biological data to be collected is published in Pennsylvania's Surface Water Quality Network (WQN) manual which can be viewed and download via the link on this webpage. Detailed lists of both active and discontinued WQN stations are included in the Manual. The active WQN water chemistry and macroinvertebrate stations can be viewed using the WQN web application

Data Collection

Data collection is a collaborative effort between the United States Geological Survey (USGS) PA Water Science Center, Susquehanna River Basin Commission (SRBC), and Pennsylvania Department of Environmental Protection (PADEP). The data collected at these stations is downloadable from EPA's STORET/WQX website and the Water Quality Portal. The water chemistry data collected at the Chesapeake Bay Nutrient Loading stations is also downloadable from the Chesapeake Bay Program (CBP) Water Quality Database and the water chemistry data collected by USGS is also obtainable from their NWIS database. Reporting on data collected at WQN stations can be found in the USGS Annual Data Reports, SRBC Technical Reports, the SRBC Annual Reports, and in the PADEP Integrated Water Quality Monitoring and Assessment Report narrative. Links to the databases and reports can be found at the bottom of this page.

WQN Web Application

This GIS-based application allows users to view WQN water chemistry and macroinvertebrate site locations. The application contains the active stations, those currently being sampled. Future enhancements include adding the historic/inactive stations and the ability to download macroinvertebrate and water chemistry summary reports.
GIS illustration


For information and/or questions regarding the Water Quality Network call 717.787.9637.