Nutrient Concentrations at Baseflow Conditions in the Upper White River Basin, Southwest Missouri and Northwest Arkansas

The Upper White River Basin (UWRB) is becoming increasingly vulnerable to water quality degradation from urban/population growth and increased agricultural production. This study examines the relationships among nutrient levels, water chemistry and watershed characteristics of 19 watersheds in the UWRB. Water samples were collected during baseflow conditions each month for one year at USGS continuous-flow gage stations. Watershed characteristics evaluated were land use, geology, drainage area, flow discharge, and wastewater treatment plant discharge (WTP). Measured chemical water quality indicators include total nitrogen (TN), total phosphorus (TP), specific conductivity, turbidity, pH and dissolved oxygen. Rapidly expanding urban areas are associated with relatively high nutrient concentrations at baseflow such as found in the James River Basin, where mean levels range from 0.9 to 11.7 mg/L for TN and 18 to 175 μg/L for TP. Nutrient concentrations have a strong positive correlation to specific WTP discharge (gal/day/km²). Non-point source-affected watersheds with no or only slight WTP inputs show a negative relationship between percent forest cover and nutrient concentrations. Higher nutrient concentrations are found in watersheds with less than 50% forest in non-point source watersheds, although these nutrient levels remain below the James River recommended Total Maximum Daily Load ( \u3c 75 μg/L TP and \u3c 1.5 mg/L TN). Agricultural watersheds ( \u3e 50% ag land) in karst limestone plain areas also show elevated nutrient concentrations ranging from 0.4 to 5.2 mg/L for TN and 9 to 103 μg/L for TP