Development and Implementation of a Baseflow (groundwater) Monitoring Network for the Pepacton Watershed

The Pepacton watershed is an integral part of New York City's public-water supply system. Most of the watershed is within Delaware County with headwaters of some of its eastern tributary streams originating in Greene and Ulster Counties. Land use varies from dairy farms in the northern portion of the watershed to extensive forested areas in the south with small rural communities interspersed throughout the watershed. Sound management of the water resources in the region necessitates development of hydrologic data networks that will document current water-quality conditions in relation to watershed characteristics such as land use. Ground-water discharge to streams accounts for most of the water reaching the New York City reservoirs during periods of little or no rainfall (baseflow conditions), and a large proportion (60-70 percent) of total annual streamflow. Baseflow samples from carefully selected drainage areas provide a composite or integrated ground-water discharge sample that is a reflection of the most active part of the shallow ground-water flow system. The study addresses ground-water quality (major ions, nutrients, selected pesticides and their metabolites) through development of a monitoring network of baseflow sites that characterize spatial (land use, physical basin characteristics) and temporal water-quality variations within the Pepacton watershed.

Objectives

• Development of a ground-water (baseflow) monitoring network that will provide water-quality data that are representative of upland and valley shallow ground-water flow systems and the spatial variations in the type or intensity of land use in each sampled basin.
• Identification of temporal water-quality variations in baseflow.
• Interpretation of initial water-quality data on the basis of hydrogeologic setting, land-use type, distribution, and intensity.