COMPARATIVE EFFICACY OF SOME EMPIRICAL MODELS TO ESTIMATE SEDIMENT YIELD IN SMALL CATCHMENTS

Empirical models have been developed to estimate erosion for a certain area and their calibration is essential for use in off-site conditions. Empirical modeling with high accuracy and efficiency for estimating sediment load can lead to better estimates of sediment load, resulting in a more appropriate design of soil and water conservation practices. The aim of this study was to compare the efficiency of FSM, MPSIAC and PSIAC models in estimating erosion and sedimentation. In this study, 10 small watersheds were selected with areas between 14.3 and 556 hectares as the field of research. The model parameters were determined using available maps, satellite images and field operations. The amount of watershed sediment was estimated using empirical models described above. Observed sediment was calculated by determining sediment volume in check dam by field method. The minimum, average and maximum observed sediment were respectively 0.41, 0.82 and 1.18 m3ha^-1 year^-1. The correlation coefficients between the observed sediment and the estimated sediment by the empirical models of FSM, MPSIAC and PSIAC, respectively, were 0.56, 0.47 and 0.54. The estimated sediment data of the empirical models were compared with the observed sediment data of the relative error test. Values of the relative error estimated for FSM, MPSIAC and PSIAC models were 38.67, 1.22 and 2.35. Efficiency index of Nash and Sutcliffe for FSM, PSIAC and MPSIAC models were, respectively, -17386.37, -45.46 and -11.48. These results indicated that the FSM model compared with the other two models had more errors, and this model with the baseline coefficients has no efficiency to estimate the sediment of small watersheds, and the two PSIAC and MPSIAC models also faced with sediment overestimation, but the MPSIAC model showed relatively acceptable results.