Modeling Suspended Sediments in Dez Basin

ABSTRACT: The flow discharge is always regarded as the most important sediment transport factor, but practically different sediment values have been measured for a certain value of flow discharge, hence other factors are also effective in sediment transport. In this research, it has been attempted to modify the sediment rating equation through considering factors affecting sediment transport such as measurement time. For this purpose, the data related to flow discharge and long-term daily sediment discharge in Tale Zang Hydrometric station were used which is among the first-class stations constructed on Dez river. The results of data homogeneity test in this station showed that all discharge data are homogenous with a significance level equal to 91.4%. Also based on the Kolmogorov goodness-of-fit test, the log-normal distribution was selected as the best statistical distribution for annual average discharge data. Then, the data related to sediment discharge and the daily flow discharge were modeled in five modes, i.e. monthly, seasonal, high-precipitation and low-precipitation months, classification and without data separation and the statistical index known as minimum mean square error (MSE) was used in order to select the best model. The model in which the data were separated in a monthly manner was introduced as the modified sediment rating equation and the amount of suspended load was estimated about 345 millions of tons during the entire statistical period, using the monthly model.