Water-Quality Assessment of the Potomac River Basin:
Water-Quality and Selected Spatial Data, 1992-96


The U.S. Geological Survey (USGS) implemented the National Water-Quality Assessment (NAWQA) Program to describe the status and trends in the quality of the Nation's surface water and ground water and to provide scientific understanding of the natural and human-induced factors that affect water quality. In 1991, twenty study units were started. Additional study units began in 1994 and 1997. Data collection and analysis in each study unit follows national guidelines for the NAWQA Program,  but also addresses the issues most important to that study unit. NAWQA is designed to produce a wealth of water-quality information to assist policy makers and managers at the national, state, and local levels in making more informed decisions.

In 1991, the Potomac River Basin study unit began planning assessment activities. The basin was subdivided into eight subunits based on physiographic and geologic characteristics, which were determined to be the most influential natural factors affecting water quality. Water-quality sampling began in 1992. The first high-intensity data-collection phase of the study unit spanned from 1993 to 1995; much of the data collection focused on the Great Valley Carbonate, Piedmont, Triassic Lowlands, and Valley and Ridge subunits. Hundreds of water-quality characteristics were measured in different media during this time, including ground water, streamwater, streambed sediments, and aquatic biological tissues. Fish communities and stream habitat also were sampled. In addition, spatial data such as geology, land use, hydrography, and other watershed characteristics were compiled into a geographic information system (GIS) to support the assessment. After 1995 the project entered a period of less frequent sampling called the low-intensity phase.

Purpose and scope

This report presents data collected and compiled during the first high-intensity phase of the Potomac NAWQA study unit. Data are presented from 138 ground-water wells and 125 stream sites. Ground-water measurements compiled in this report include chemical, physical, and water-level data. Streamwater measurements compiled include chemical, physical, streamflow, bed-sediment contaminants, aquatic-tissue contaminants, fish community, and selected stream habitat data. Quality-control chemical data are also presented. Basinwide and site-specific spatial data compiled by the study unit are also distributed with this report.

Study design and sampling methods

The study design and sampling methods developed for the Potomac NAWQA study unit are consistent with the national NAWQA guidelines (Gilliom and others, 1995). The design permits an integrated assessment of conditions at local, regional, and national scales. For more information refer to the report, "Design and Implementation of a Sampling Strategy for a Water-Quality Assessment of the Potomac River Basin" (Gerhart and Brakebill, 1996). Sampling methods and protocols for the NAWQA Program are documented in a series of guideline documents. Citations for these can be found in the Selected references section of this report.

Using this report

The data presented in this report are organized according to the Potomac River Basin study unit's design. This report is a companion to the report, "Design and Implementation of a Sampling Strategy for a Water-Quality Assessment of the Potomac River Basin" (Gerhart and Brakebill, 1996). The data can be accessed two ways, viewing the data on screen or downloading the data. The 'view data' tables present selected analytes only. Due to size constraints on computer screens and the time it takes for larger tables to be viewed on screen, the analytes were abridged to facilitate an easy glance at the data presented in this report. The download files contain all data for each subheading. The download files are in a tab-delimited ASCII format with comment lines set aside by the pound key (#), a field name line, and a field definition line.

The selected spatial data section contains the metadata for those geographic information system (GIS) data sets that were used by the study unit for analysis. The metadata complies with Federal Geographic Data Committee (FGDC) standards. To download the actual data go to the Distribution Information link.


The authors would like to thank Scott Ator, John Battista, Bruce Bernard, Joel Blomquist, Matthew Ferrari, Gary Fisher, James Gerhart, Liz Gno, Michael Hackney, Kalman Illyefalvi, Phyllis Illyefalvi, James Jeffries, Jon Kaye, Stephen Maskol, Cherie Miller, Mastin Mount, Michael Shackelford, Gianni Venturi, William Werkheiser, and Humbert Zappia for their contributions to this report. These members of the study-unit team collected and reviewed these data. Thanks also to Jerry Garrett for the advice on producing this report. The authors would also like to recognize the numerous landowners that provided access to wells and stream sites for sample collection.

Special thanks to Dan Cincotta from the West Virginia Department of Natural Resources for verifying our fish specimens.

Some of the monitoring data included in this report were partially funded by the Interstate Commission on the Potomac River Basin. USGS personnel using sampling and analytical methods comparable to NAWQA protocols collected these data.

For more information

This report is being distributed by CD-ROM and on the World Wide Web.
Requests for information or data related to this report should be directed to:

Potomac NAWQA Chief
U.S. Geological Survey
8987 Yellow Brick Road
Baltimore, Maryland 21237

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Last modified: Wed Nov 12 16:34:39 1997