During low flow periods in summer, portions of the Pigeon River, North Carolina, have experienced depressed dissolved oxygen concentrations. The Pigeon River receives multiple point source effluents from several wastewater treatment facilities and a large kraft paper mill located in Canton, NC, which contribute the oxygen-demanding and nutrient loads on the river. A water quality model was constructed to examine processes and sources contributing to the observed oxygen declines and to evaluate the specific management alternatives. Simulations showed that relatively little of the CBOD materials released by the mill were degraded within the river and were subsequently 'deposited' in the reservoir at the end of the modeled river segment. Reductions in CBOD concentrations could be generally accounted for by tributary dilution. However, nitrogenous oxygen demanding materials released by the mill (e.g., NH3) created a considerable demand for oxygen within the modeled segment of the river.