اعتبار روش هاي برون يابي در برآورد ميانگين رسوبدهي معلق سالانه (17 ايستگاه هيدرومتري كشور)

The validity of extrapolation methods in estimation of annual mean suspended sediment yield (17 Hydrometric Stations)

Sediment yield isnʹt usually estimated by interpolation methods; because of lacking of enough rivers concentration data. So the most common method to estimate mean suspended sediment load (SSL) is using sediment rating curve (SRC) in combination with discharge data classified as extrapolation methods. There are different methods for determination of SRCs equation and processing flow data. In this research we estimate the SSL in 17 hydrometric stations with 18 extrapolation methods to evaluate the accuracy and precision of them. These methods classified to 6 groups of SRC estimation and 3 types of flow data. In addition we computed the actual SSL on the basis of intensive sediment concentration data in Ghazaghly station using interpolation method. Comparison of results showed that the "Mean loads within discharge classes- Daily discharge" method has good agreement with actual load and therefore selected as the standard method. Finally differences among 17 methods are comprised and evaluated with standard one in other 16 stations. The results showed that FAO, Nonparametric, Parametric, and Fitting one line methods havenʹt good agreement with standard method. Also Flow duration method underestimated SSL about 14%.