Modeling Nitrogen, Oxygen, Chattahoochee River, Ga.

A steady-state nitrogen, carbonaceous biochemical oxygen demand (CBOD), and dissolved oxygen (DO) model of a 67-mile (108-km) reach of the Chattahoochee River, near Atlanta, Ga., was calibrated and verified. Four data sets were collected during weekend low-flow steady-state conditions through the summers of 1976 and 1977. The nitrogen model predicts concentrations of organic-nitrogen, ammonia-nitrogen, nitrite-nitrogen, and nitrate-nitrogen. Also, an unsteady-state ammonia-nitrogen, CBOD, and DO model was tested using parameters calibrated in the steady-state model and unsteady-state flow data collected in July 1976. The steady-state model was calibrated and verified using two data sets for each step. The unsteady-state model predicted average daily DO concentrations accurately but did not account for daily temperature changes that led to a lack of prediction of diel DO changes. A comparison was made with results obtained using the Velz model on the same reach using the same data sets.