Water-Quality Assessment of the Potomac River Basin: Water-Quality and Selected Spatial Data, 1992-1996

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. 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. 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.