SENSITIVITY ANALYSIS OF SIMULATED DISSOLVED OXYGEN IN BAHR HADUS DRAIN, EGYPT

Modeling is an essential tool in decision making in water quality assessment. Uncertainty in model parameters can have a profound impact on the results. Failure to accommodate parameter uncertainty undermines the ability to make informed decisions regarding water quality issues. In this paper, we illustrate the use of the Monte Carlo simulation method to propagate the uncertainty from model input to model output. The methodology is illustrated on a Streeter-Phelps prototype model, where basic uncertainty in aeration parameter, biochemical oxygen demand decay parameter, water temperature, and initial concentrations of dissolved oxygen and biochemical oxygen demand is considered. The effect of the basic input parameter uncertainty on the simulated dissolved oxygen in a stream at a specific point in time is assessed by assigning prescribed probability density functions to these parameters. The sensitivity of the simulated dissolved oxygen concentration with respect to the uncertainty in the basic input parameters is evaluated using the Spearman rank correlation coefficient. The proposed model is applied to Bahr-Hadus drain which carries drainage flows that contain loads of municipal wastewater from treatment plants, and untreated wastewater from villages.