Application of Numerical Modeling for Solution of Flow Equations and Estimation ofWater Quality Pollutants in Rivers (Case Study: Karkheh River)

In recent years, many efforts have been made in the field of development of water quality models to estimate the amount and rate of pollution of rivers, coasts and the estuaries. Many factors are considered in these models. For example, coliforms, BOD, SOD, nitrogen cycle, dissolved oxygen (DO) and phosphorus can be pointed out. The purpose of this research is dynamic investigation of flow and water quality parameters in Karkheh River. According to available data, the parameters of salinity, BOD, and phosphorus for a reach of Karkheh River between Paye Pole and Hamidiyeh stations were analyzed and simulated and Abdelkhan hydrometric station was selected as a survey station. Before proceeding to the modeling of water quality and sediment transport in river systems, it is necessary to solve hydrodynamic equations affecting the river flows. For this purpose, FASTER model has been used. Two time periods between the years 1386-1388 were selected for the model calibration and verification. For solving the hydrodynamics of flow, it is necessary that Manning roughness coefficient (n) to be calibrated in FASTER model. With adjusting of this factor, value of 0.028 was chosen. In the next step Advection Dispersion Equation (ADE) must be solved. For this purpose, 4 Dispersion Coefficients (DL), were used and with trial and error, constant coefficients were determined for the quality parameters. By comparing the measured values and the calculated values by the model in Karkheh River, for the above parameters, the Fischer Dispersion Coefficient was selected by the reasonable and acceptable comparisons. Also run results and calculated errors showed that the model was able to accurately predict hydrodynamic characters and water quality parameters