Two Dimensional Mathematical Model of Contamination Distribution in the Lower Reach of Diyala River

One of rivers that suffer from the effect of pollutants is Diyala River, due to the untreated effluents from Rustimiyah wastewater treatment plant (WWTP) and from other contaminants sources such as Army Canal Outfall. These outfalls are discharged continuously to the river and located at different positions along the lower reach of the river. In this context, a two-dimensional mathematical model is provided to simulate the distribution of pollutants transport in the river. Strong coupling between K-ε turbulent model and advection-dispersion equation. The mathematical model has been implemented with COMSOL Multiphysics 3.5a, which is a versatile computational fluid dynamics (CFD) software package that solves coupled PDEs based on the Finite Element Method. Total Dissolved Solids (TDS), Chloride (Cl-), and Heavy Metals (Fe, Cr), are selected as principal indicators of pollutants transport in the case study. Sensitivity analysis was performed to study the effect of different parameters on the results predicted by application the two-dimensional model. The calibration of the model indicates that the best roughness height is 0.024m and the best water slope is 9cm/km. The verification indicates that a good agreement between the observed and the predicted data with a percentage error less than 10%.