NAWQA Activities in the Potomac River Basin and Delmarva Peninsula

NAWQA activities in the Potomac River Basin and Delmarva Peninsula during Cycle I were primarily focused on understanding the occurrence and transport of nutrients and pesticides in groundwater and streams. These results are published in numerous reports, and summarized in Ator and others (1998) (for the Potomac River Basin), and Shedlock and others (1999) and Denver and others (2004), (for the Delmarva Peninsula). Data collected for these studies are available in Derosier and others (1998) and in the NAWQA data warehouse. See Study Components and Data for more information.

NAWQA study in the Potomac River Basin during Cycle I centered in the Valley and Ridge, Great Valley, Piedmont, and Triassic Lowlands. Work elements included studies of stream chemistry and ecology, and groundwater chemistry. Eleven streams were sampled routinely (typically at least monthly, 1993-1995) to evaluate the influence of seasonal and flow changes on water quality. Intensive ecological studies were also conducted in a subset of these streams. These streams were distributed throughout the area in primarily forested and agricultural watersheds; one was located in a small urban watershed near Washington, D.C. In addition, stream-chemistry and ecological studies were done at 89 small streams in four subunits during summer base-flow conditions, and a synoptic survey of stream chemistry was done at 23 larger stream sites during spring base flow in 1994. The distribution of organic contaminants and metals was also studied at 26 small stream sites. Of these sites, 21 were also sampled for aquatic tissues. Regional groundwater studies were conducted in the Piedmont and Triassic Lowlands (1994), and in agricultural areas of the Great Valley (1993) and Valley and Ridge (1995). A flow-path study was conducted in a small agricultural basin in the Great Valley.

The Coastal Plain Province was the focus of study on the Delmarva Peninsula during Cycle I. Most of the activities for the Delmarva Pilot (1987-1991) project were concerned with groundwater resources, with only a limited amount of sampling of surface water in local flowpath networks and a seasonal synoptic survey for nutrients. Groundwater samples were collected from several networks in the surficial aquifer system, and also from 36 wells in the confined-aquifer systems. Sampling in the surficial aquifer included an areal network of 32 pairs of randomly located shallow and deep wells, five peninsula-wide transects of five to 10 wells each, and 7 flowpath networks that represented major hydrogeologic settings on the Peninsula. During the Delmarva Cycle I project (1999-2001), 4 of the flowpath networks were resampled and the pilot areal well network was redesigned into a study of the effects of agricultural land use and a study of the parts of the aquifer used for domestic drinking water. Where these well networks included wells from the pilot areal network, changes in groundwater chemistry over time from the pilot (sampled in the late 1980s) to Cycle I (sampled in the late 1990s) were examined. Two surface-water fixed sites associated with flowpath networks were also sampled from 1999-2001. A network of 30 surficial aquifer drinking-water supply wells was sampled for nutrients, pesticides, volatile organic compounds, and radionuclides in cooperation with the State of Delaware.

NAWQA activities in the Potomac River Basin and Delmarva Peninsula (PODL Study Unit) during Cycle II were focused increasingly on quantifying and understanding changes in water quality over time, the fate and transport of nutrients and pesticides in streams and groundwater, and effects of observed water quality on stream ecosystems and drinking-water resources. Four streams in the PODL are included in the national NAWQA surface-water trends network and are therefore sampled routinely for water chemistry and (in three of the streams) ecology. In addition, four groundwater-quality networks from Cycle I are included in the NAWQA groundwater trends network; water quality in network wells is measured approximately every decade and water levels are measured annually. Water quality in a subset of wells is also measured every other year. Similarly, the cooperative study of water quality in Delaware water supply wells with the State of Delaware was repeated in 2008(?). Additional NAWQA activities in the PODL in Cycle II include a detailed study of agricultural chemical transport in the Morgan Creek Watershed, Maryland (link to Agricultural Chemical Transport under Study Components and Data), a study of effects of nutrient enrichment on stream ecology on the Delmarva Peninsula (link to Effects of Nutrient Enrichment under Study Components and Data), and a study of water quality in drinking-water resources, including the Potomac River and groundwater of the Piedmont.

Data-analysis and interpretive activities as part of NAWQA Cycle II have become increasingly regional and national in scope. Such activities for groundwater are conducted as part of regional principal aquifer teams for the Northern Atlantic Coastal Plain and the Piedmont and Valley and Ridge; regional activities for surface waters are conducted as part of the Northeast Major River Basin team (MRB1).

For more information about the NAWQA PODL Study Unit, contact Judy M. Denver, Supervisory Hydrologist, at: jmdenver@usgs.gov.