Estimating of the amount of soil loss using universal soil loss equation in the Jonghan watershed

In the recent years, the effects of economic and environment, resulting from soil erosion and sediment yield is one of the most important joint issues in around the world and watersheds from Iran especially. So many scientists use indirect methods mainly erosion and sediment relations and models. These relations that are usually used in the country were imported and less compatible with the country's conditions. So, when applying these relations, the results should be calibration and statistical validation using observation data, so that if high precision, are used in the same region. The objective of this study was the estimating ofthe efficiency of universal soil loss equation with measuring observation erosion in study area.
This study was carried out on the soil dam of the Aij watershed in the Chaharmahal va Bakhtyari province. The six factors of model include: Rain erosivity factor using the rainfall erosivity map, soil erodibility factor by soil sampling in the homogenous units and using the wischmeier's anemograph (1987), slope factor using digital elevation model (DEM), land cover using satellitesimagine, the mean amount 2.75 Mj.mm per hec.yr.hr, 0.24 Mg.hec. Year per hec. MJ. mm, 0.44, 0.43 and 1, respectively. In the following, the amount of sediment using scale was measured for 4 last years.
Combining the factors of universal soil loss equation using ARCGIS9.3, the amount of annual soil erosion was estimated about 0.13 tons per hectare per year. On the other hand, using the amount of observed sediment load and sediment delivery ration, the observed erosion calculated about 3.3 tons per hectare per year.
The difference of the amount of estimated erosion using soil loss equation with observation erosion showed that, the model has low ability to use in the study area and areas with similar characteristics.