Investigation of the relationship between land uses and the sediment load to evaluate the model accuracy EuroSEM in part of the northern Karoon sub-watershed

Determination of soil erosion and runoff for soil conservation practice requires dynamic model. The objective of this study was to evaluate EuroSEM (European Soil Erosion Model) to measure runoff, erosion and sediment in part of the sub-northern Karoon watershed. The model used in this research is a single event process-base model for predicting soil erosion and sediment. Actual runoff and sediment discharge was calculated using a metal rectangular weir installed at the outlet. Parameterization, calibration and validation of the model were carried out for simulation and also model efficiency was evaluated by determination of coefficient and ME index. Calibration results (Nov. 26, Dec. 16 storms) indicated that best calibration were achieved by decreasing effective net capillary drive and increasing initial volumetric moisture content for hydrographs and also increasing cohesion of the soil and the value of Manning's n in both the rill and interrill areas and decreasing values describing the detachability of the soil particles by raindrop impact for sedigraphs. Validation results (Mar. 8, Mar. 28, Apr. 21 storms) indicated that EuroSEM model simulated total runoff discharge and peak runoff rate well. Evaluation index showed that model efficiency is moderately well but different index showed different results. The simulated hydrograph and sedigraph follows more closely that of the rainfall intensity than does the observed data. Total runoff discharge varied in the range of 1.22 to 6.37 mm/ha depending on the storm being studied and total soil loss between 2.32 to 18 t/ha. The results of model simulation showed that net erosion increased by decreasing saturated hydraulic conductivity and soil erosion decreased by increasing vegetation cover during Nov. 26 to Mar. 28 in each element. Rill erosion increased from 0.16 to 0.54 and interrill erosion decreased 4.28 to 3.45 ton/ha in growing period, inversely.