INVESTIGATION OF FLUVIAL MIXING ZONES IN THE MARSH-BEECH-BALD EAGLE CREEK SYSTEM IN CENTRE AND CLINTON COUNTIES, PA

The AMD-impaired Beech Creek and nutrient-rich Marsh Creek join the net-alkaline Bald Eagle Creek before it empties into the West Branch of Susquehanna River, which belongs to the Chesapeake Bay Watershed. The goal of this study was to observe the behavior of mixing zones as they relate to geochemical processes within the Bald Eagle Creek system.

Water quality data was assessed for a 6.2-mile stretch of Bald Eagle Creek, starting below the Foster Joseph Sayers Reservoir and ending at Mill Hall, PA during the summer of 2014. The field data were collected using two Hydrolab Sondes (MS-5) that recorded temperature, pH, DO, conductance, TDS, salinity, chlorophyll-a, and ORP at one-minute intervals. In addition, 8 water samples and 7 streambed sediment samples were collected for additional lab analysis that included total acidity, alkalinity, various metals, anions and nutrient concentrations. The results of the field and lab data were visualized using ArcGIS software and analyzed using statistical methods. The data provided insights into the impact that various physical, hydrologic, geological, anthropogenic, and chemical processes have on the water quality in the studied system.

The results indicated a decline in chlorophyll-a, specific conductance and DO concentrations, and an overall increase in pH in the downstream direction. The following trends were observed for tested parameters within the studied section: (1) Concentration of iron remains persistent after its addition to the Bald Eagle Creek by Beech Creek; (2) Manganese, Chloride and Sulfate concentrations decline due to dilution by additional discharges from aforementioned tributaries; (3) Aluminum appears to precipitate on the streambed sediments in Bald Eagle Creek shortly after its confluence with Beech Creek, which is attributed to an increase in the pH values; (4) Alkalinity demonstrates a decreasing trend due to dilution and bedrock geology in the watersheds of downstream tributaries; and (5) Concentrations of all elements measured in streambed sediments fell within the acceptable ranges for freshwater sediments prescribed by the US EPA.