عنوان مقاله [English]
Background and Objectives: 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. To this reason, the extensive studies is began to estimate of soil erosion in watersheds in the last years.
To measure of amount of soil loss and sediment usually can use the two methods, contains the direct and indirect methods. Since, the direct measure methods are difficult, costly, and time consuming, and there are not any station and measure tools in many watersheds of country as well as. So many scientists use indirect methods include: 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.
This study was aimed to estimate the efficiency of universal soil loss equation with measuring observation erosion in study area.
Materials and Methods: This study was carried out in the watershed of aij's soil dam in the Chaharmahal va Bakhtyari province. The 6 factors of model include: Rain erosivity factor using regression relations, soil erodibility factor by soil sampling in the homogenous units, and using the wischmeier's anemograph (1987), slope factor using digital elevation model (DEM) and flow accumulation, land cover using satellite's imagine, and conservation management factor using relating table obtained the mean amount 84.84 Mj.mm per hec.yr.hr, 0.24 Mg.hec. y 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.
Then, the sediment’s bulk density the area of lake dam were calculated using ring method, and Google Earth, Expert GPS, AutoCAD softwares respectively. Sediment delivery ratio using the relationship graph of the area of watershed and soil texture was determined about 0.41, and in the end, the amount of observation erosion was calculated by combining the items listed.
Results: combining the factors of universal soil loss equation using ARCGIS9.3, the amount of annual soil erosion was estimated about 4.06 ton per hec.yr
Conclusion: the difference of the amount of estimated erosion using soil loss equation with observation erosion showed that, the model has ability to use in the study area and areas with similar characteristics