WATER QUALITY ASSESSMENTS ASSOCIATED WITH THE OBION RIVER WATERSHED, NORTHWESTERN TENNESSEE

Over the 20^th century, streams and riparian environments in western Tennessee experienced major human-induced geomorphic changes with significant channelization, levee construction, and wetland alterations. The Obion River (OR) watershed exhibits many of these fluvial modifications on the 1,313 mi² it drains in northwestern Tennessee via the main branch and its four forks (North Fork, Middle Fork, South Fork, and Rutherford Fork). Land use adjacent to the ~250 miles of Obion River channels is predominately agricultural (68.1%) with forested areas (28.7%) and minor developed/urban areas (1.1%).

An undergraduate research project was initiated to gather water quality data on the Obion River and its major forks. Forty-four (44) water samples were collected over a four day interval (April 17-20, 2016). Field measurements include stream flow rate, width, and depth; temperature; pH; and total dissolved solids (TDS). Laboratory measurements at the University of Tennessee at Martin included Total Kjeldahl nitrogen (TKN; colorimetric UV-vis method), phosphorus (AA), and potassium (AA). The project’s goals are to establish background water quality measurements (field and laboratory) and to determine the potential for eutrophication within the Obion River watershed.

Initial results indicate subtle variations in water quality for April 2016. The main branch of the Obion River displayed the highest TDS values ranging from 60.5 ppm (upstream) to 126 ppm (downstream). The North (NF), Middle (MF), South (SF), and Rutherford (RF) Forks yielded lower TDS values (36.3-76 ppm). Measured nutrient loads for April 2016 were low. Potassium averaged 1.2 ppm across the watershed. The average phosphorus was 4.4 ppm with highest values observed in the Middle and Rutherford Forks. TKN averaged 2.4 ppm with higher values observed in the North and South Forks.