| Summary: | Mathematical and Physical Sciences: 2nd Place (The Ohio State University Denman Undergraduate Research Forum) Hellbranch Run drains land near Columbus, Ohio that was subject to rapid conversion from agricultural to urban land use during the 1990s. The stream is a tributary to Big Darby Creek, a national scenic river that is valued for its biological diversity and health. Headwater areas in the Hellbranch Run watershed have been channelized, and the stream’s water quality is threatened from nutrient enrichment caused by agricultural runoff. In recent decades, State and private organizations have funded and implemented stream remediation within the Hellbranch Run watershed. The objective of this study was to synthesize historically measured flow and solute concentrations to identify trends in loading of select water quality constituents to Big Darby Creek and also investigate spatial and seasonal variations of water quality within the Hellbranch Run watershed. Water samples were collected from four sites within the Hellbranch Run watershed, bimonthly for one year (Nov. 2009 to Nov. 2010) for n=84 samples. Sites represent headwater areas with differing land use. Sampling involved filtering, measuring temperature, pH, and conductivity in situ and laboratory analyses of water samples were for total suspended solids (TSS), dissolved major ions, and major nutrients: nitrate + nitrite-(N), ammonium-N, total dissolved N, phosphate and total dissolved P (TDP) concentrations. Results show N, TDP and Cl- having high concentrations: N median 1.4 mg/L (~0.0 – 4.3 mg/L), TDP median 398 ug/L (67 – 1,773 ug/L), and Cl- median 99.5 mg/L (40.3 – 873.7 mg/L). Geographic information systems were used to investigate changes in land cover within the watershed from 1992–2006. The watershed of Clover Groff Ditch one of two major tributaries to Hellbranch Run, underwent substantial conversion from agricultural land to urban and showed a corresponding decrease in major nutrient and ion concentrations relative to other headwater areas in the Hellbranch Run watershed. Hamilton Ditch, the other major tributary that largely drains agricultural land, had the highest concentrations of all nutrients and major ions. Seasonal shifts exhibited a strong control on N with highest concentrations in the winter and lowest in the summer. TSS concentrations were highest immediately downstream of the two ditches. Historical flow and measured dissolved N, TP (unfiltered), Cl-, and TSS were used to estimate daily loads using the USGS computer program LOADEST. The resulting time series showed a decreasing trend in N between water years 1993 and 2010, which could be related to urbanization and stream remediation efforts that occurred over the time period. The Ohio State University School of Earth Science Byrd Polar Research Center Shell Exploration and Production company Academic Major: Geological Sciences
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