Spatial and Temporal Variations of Water Quality in Hellbranch Run: A Historical Perspective
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Date
2011-06
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The Ohio State University
Abstract
The Big Darby Creek west of Columbus, Ohio is a National Scenic River and is highly protected by governmental and nongovernmental agencies. A watershed tributary, Hellbranch Run, drains land that has recently seen conversion from agricultural land to urban. Urbanization can degrade streams due to increased impervious surfaces in the watershed which create pulses of sediments and pollutants to flow to streams during storm events. Study objectives are to determine and interpret the temporal and spatial dynamics of major nutrient and total suspended solids concentrations from four sites along Hellbranch Run. Sites represent different land-use catchments and upstream/downstream on the mainstem of the stream. Land-use records from 1992, 2001 and 2006 were used to compare changes in nutrient loads overtime to land-use changes. Bimonthly sampling took place from Nov. 2009 to Nov. 2010. Sampling involves measuring temperature, pH and TDS in situ in the stream. Samples were analyzed for major nutrients, including nitrate+nitrite-N, ammonium, total nitrogen, phosphate and total phosphorus concentrations. Results show total phosphorus having very high concentrations: median 398 ug/L and range (66.8 to 1,773 ug/L), whereas ammonium is closer to an environmentally acceptable level: median 52.8 ug/L, range (11.7 to 1623 ug/L). Additionally, Hamilton Ditch, a headwater draining cultivated crop, tends to have the highest concentrations of all nutrients, whereas the larger urban headwater streamreach showed lower values. Seasonal shifts exhibited a strong control on nitrate with highest values in the winter and lowest in the summer, while phosphorus shows a weaker trend with highest values in the fall. Suspended solids ranges from 4.4-612 with mean 38.5 mg/L and has lower values upstream and highest just downstream of the confluence of the two headwaters. Historical flow, nutrients and TSS data was used to estimate daily loads using the program LOADEST and the resulting time series shows an estimated decrease in nitrate loads over the last 18 years. Knowing the current state of the water quality along Hellbranch Run is important in understanding the effects that local land-use has on it and will aid land management policy-makers.
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Keywords
Hellbranch Run, Big Darby Creek, Headwater Streams, Nutrient Enrichment, Urbanization and Water Quality, N and P loads