Performance Evaluation of Correction Factors in Optimization of Sediment Rating Curve (Case Study: Kamal Saleh Dam Watershed, Markazi Province, Iran)

Because of importance of sediment delivery of watersheds, sediment rating curve is used for estimation of suspended sediment concentration. But most often sediment rating curve can not represent sediment concentration well in high flows, because of bias in log-transformation and extrapolation of data. For optimization of sediment rating curve, this research carried out with data of Q-SSC in outlet of two sub watershed of the Kamal Saleh dam watershed, Markazi province, Iran. Sediment data analysis was carried out using sediment rating curve of single-line and mean of classes with different correction factors such as FAO, QMLE, Smearing, MVUE and β. The results of various evaluation indices showed that the optimum sediment rating curve in the Hasan-Abad station follows single-line sediment rating curve and in the Ghaleh-No station mean of classes sediment rating curve, both with average of MVUE correction coefficients. According to the results, β correction factor for mean of classes’ sediment rating curve could reduce the difference between observation and estimation for high flows, but because of high scatter of observed data and undesirable extrapolation the Smearing-linear and QMLE had the lowest efficiency. However, for high flows in torrential events, the mean of classes’ sediment rating curve with FAO correction factor gave more accurate results than other methods.