BASELINE WATER QUALITY IN TRIBUTARIES TO THE UPPER DELAWARE SCENIC AND RECREATIONAL RIVER PRIOR TO POTENTIAL SHALE-GAS DEVELOPMENT

The Delaware River borders New York and Pennsylvania in an area underlain by the Marcellus Shale. Although a moratorium to ban drilling for shale gas in the Marcellus or other formations is currently in place in the Delaware River Basin, there remains potential for shale-gas development, especially in watersheds of tributaries to the Upper Delaware. Water quality is of primary importance to the 73.4 mile reach of the Delaware River managed by the National Park Service (NPS) as the Upper Delaware Scenic and Recreational River (UPDE). In 2012, the U.S. Geological Survey in partnership with NPS began a 3-year study to establish baseline water quality in selected tributaries to UPDE prior to extensive shale-gas development. Six tributaries were sampled monthly for 2.5 years and 12 other tributaries were sampled twice. Stream water samples were analyzed for a suite of inorganic constituents including major ions, nutrients, and trace metals. Results indicate that most stream waters are relatively dilute, commonly having low specific conductance (less than 100 microSiemens per centimeter) and low concentrations of most analytes. Seasonally, concentrations of some analytes increase (by a factor of two or more) during low-flow periods in summer and runoff periods in winter, as inferred from continuous water-quality data collected by NPS with in-stream sondes and discrete samples. Bromide concentrations typically are low (less than 0.03 milligrams per liter) and may be useful to differentiate sources of chlorides (road salt or shale-gas brines) associated with development using chloride/bromide ratios.