Water quality and quantity modelling in Bahmanshir River and its channels

Bahmanshir River is one of the main water resources in southwest Iran. Salinity intrusion and other pollution sources have influenced the water quality in this river. In this study, quantitative and qualitative modeling of Bahmanshir River and the water channels of Choebdeh shrimp culture is performed using MIKE11 software.
First, manning number of the river is estimated as 0.018 by integrated hydraulic modeling of the river and its water channels. Then, dispersion factor of the river is calculated as (v: velocity) by solving Advection-Dispersion equation. Modeling of water quality parameters, such as dissolved oxygen, nitrate, ammonia, BOD and temperature, is performed using ECOLAB module in the MIKE11 software. The major parameters in the water quality model are determined using sensitivity analysis. These parameters were calibrated and the calibrated model is verified.
Findings: The results showed that the water channels behave as complete mix systems. Conversion coefficients of water quality parameters are calculated, and then the average values of salinity, dissolved oxygen, ammonia and nitrate in the channels are calculated as 27000, 3, 3 and 5 ppm, respectively. In addition, these parameters in the river are about 5300, 2.2, 1.2 and 11 ppm, respectively. The correlation coefficient of developed hydraulic model in verification step is 0.95 and the percent of absolute error of verified salinity, dissolved oxygen, temperature, ammonia and nitrate models are 7.9, 12, 1.2, 0.79 and 0.34, respectively.
The results demonstrated the capability of MIKE11 for water quality and quantity modeling in tidal rivers.