Faecal coliform (FC) microorganisms are one of the most important indicators in water quality management, since their presence reveals the possibility of existence of other dangerous microorganisms, leading to higher health risks. An accurate estimate of the concentration of this indicator helps better evaluation of the water pollution in riverine basins; thus, it is essential for future developments. The FC mortality rate depends on the physical, chemical, and biological processes in rivers. These processes are generally affected by environmental conditions. In this study, the decay coefficient (K) or mortality rate are related to the environmental parameters such as temperature, turbidity, pH, and salinity by an empirical equation. The results showed that turbidity and temperature are the most effective parameters. Moreover, an empirical equation was developed utilizing numerical model calibration, which describes the relationship of the mortality rate (K) with water temperature and turbidity. This equation was then added to the water quality module of the FASTER numerical model. Comparison of the measured FC concentrations with the predicted values obtained from the numerical model showed that the model accuracy significantly improved for the dynamic and variable decay coefficient.

粪大肠菌（FC）微生物是水质管理中最重要的指标之一，因为它们的存在表明存在其他危险微生物的可能性，从而导致更高的健康风险。准确估算该指标的浓度有助于更好地评估河流流域的水污染；因此，这对于未来的发展至关重要。FC死亡率取决于河流中的物理，化学和生物过程。这些过程通常受环境条件的影响。在这项研究中，衰减系数（K或死亡率与环境参数有关，例如经验公式涉及的温度，浊度，pH和盐度。结果表明，浊度和温度是最有效的参数。此外，利用数值模型校准建立了经验方程，该方程描述了死亡率（K）与水温和浊度之间的关系。然后将该方程添加到FASTER数值模型的水质模块中。将测得的FC浓度与从数值模型获得的预测值进行比较表明，动态和可变衰减系数的模型精度显着提高。