NAWQA: Study Components and Data

Ground Water

Ground-water samples have been collected and analyzed in the Potomac River Basin and Delmarva Peninsula (PODL) as part of the NAWQA program since the late 1980s. Sampling programs are designed and implemented to support the major objectives of the NAWQA program, including evaluation of the status and temporal trends in water-quality conditions, and identification of natural and human factors affecting those conditions.

Ground-water sampling during the first 10-15 years of NAWQA activities in the PODL have been directed largely toward evaluating spatial variability in ground-water quality among many of the diverse land-use and hydrogeologic settings that occur within the Potomac River Basin and Delmarva Peninsula. Sampling has been limited mainly to relatively shallow, unconfined ground water, and was designed to: 1) evaluate effects of particular agricultural or urban land uses on recently recharged ground water, and/or 2) estimate the distribution of pesticides, nutrients, or other chemicals in ground water that is widely used for domestic or public supply. Effects of agriculture on shallow ground water have been measured in the most intensively agricultural areas of the PODL, including the Delmarva Peninsula and the Great Valley, as well as in the Valley and Ridge. Effects of urbanization on ground-water quality have been evaluated in urbanizing areas of the Piedmont in the suburbs of Washington, DC. Regional ground-water quality has also been evaluated in major aquifers of the Piedmont and of the Coastal Plain along the Fall Line and on the Delmarva Peninsula. Studies of local-scale ground-water flow and quality have been conducted to supplement these regional investigations in the Great Valley and on the Delmarva Peninsula. Because ground water typically flows very slowly, studies of temporal trends in ground-water quality as part of the NAWQA program are planned for an approximately decadal time scale, and have just begun in recent years. Several of the regional land-use and major aquifer studies noted above will be resampled in the future at approximately ten-year intervals.