Introduction

In the Piedmont Physiographic Province of southeastern Pennsylvania and northern Delaware, ground-water discharge sustains the majority of streamflow. Thus, the quality of both streams and ground water can be affected by soluble contaminants that infiltrate to the ground-water system. Because ground water and surface water in the Red Clay Creek Basin are used for drinking-water supply, degradation of these resources is of concern.

The Red Clay Creek is known to be degraded by point-source discharges and runoff from industrial sites and agricultural land. Polychlorinated biphenyls (PCB's); pesticides, such as DDT; and metals, such as zinc, have been detected in the stream sediments (Rice, 1993; Hardy and other, 1995). Some stream reaches exhibit low benthic macroinvertebrate diversity (Moore, 1987; Hardy and others, 1995), indicating poor water-quality conditions that may include the presence of toxins, excessive sediment, elevated temperature, low dissolved-oxygen concentrations, elevated nutrient loads, or other problems.

Although the quality of stream water and sediments has been studied and continues to be monitored by state and federal agencies, (U.S. Environmental Protection Agency, Pennsylvania Department of Environmental Protection (PaDEP), Delaware Division of Natural Resources and Environmental Conservation, U.S. Fish and Wildlife Service, and the U.S. Geological Survey (USGS)), data on ground-water quality prior to 1993 in the Red Clay Creek Basin were limited to samples collected near suspected point sources of contamination. The effects of nonpoint-source pollution associated with land-use activities on ground-water quality in the basin were unknown. Results of other studies in the Piedmont in Pennsylvania (Fishel and Lietman, 1986) and in Maryland (McFarland, 1994) indicate that ground-water quality is related to land use.

A study to assess ambient ground-water quality and relate ground-water quality to hydrogeologic and land-use factors and to surface-water quality was begun in 1992 to provide basic data required to help manage the water resources of the basin. This study was conducted by the USGS in cooperation with the Chester County Water Resources Authority. Impetus and one half of the funding for the study came from the Red Clay Valley Association.

Posted August 2011