Analysis of Hysterics Curves of Suspended Sediment in the Lighvan River

Knowledge of variation of suspended sediment due to sudden and gradual fluctuations of river discharge is one of the important subjects in water studies specially watershed management. For this purpose sediment hysteretic loops based on hysterics theory have been utilized for last decade. Due to lack of such studies in Iran, this study attempts to investigate variations of suspended sediment hysteretic loops of 13 runoff events along 4 years for the first time. Therefore, after simulation of instantaneous suspended sediment concentration using Artificial Neural Networks and regression methods, hysteretic loops of suspended sediment plotted based on the best method from which 6 cases of single valued, 4 cases of eight-shaped, 2 cases of clockwise and one case of counter-clockwise were observed. The results showed that the linear hysteretic loops occurred in spring were because of low intensity precipitations and the 8-shaped loops mostly occurred in dry season with low river discharge and intense precipitations.