This research was conducted to compare EPM and MPSIAC models efficiencies for estimating sediment yield. Taleghan waterr.hed (Tehran province, Iran) with 948.5 km2 area, complex topography and climatic, Vegetative, and geological diversity was chosen as the study area. A part of the essential data were obtained through field survey and labratory analysis, and others from the documents (maps, 1 :50000, and reports) of the Taleghan complete watershed managment study. Digital data preparation was done using digitizer (maps) and keyboard ( other data). All of the required operations such as editing, manipulation, transformation. processing and analysis of data were done by Geographic Information Systems (GIS). The UTM coordinate system was used for aU of the data layers. lvleanwhile, with
digitizing contour line (100 m interval) and interpolation (50x50 m grid), Digital Elevation Model (DEM) of the study area was provided for preparing slope layer as well as other necessary processings and calculations. The related operations of model structures were done on data layers by means of GIS. The results revealed that the MPSIAC model has more efficiency than EPM.
These two models estimated observed annual sediment yields at,98.31 and.
74.96 percent, respectively. Also, mean rate of annual sediment yield was determined at 871 and 666 m3fkm2jyr respectively by MPSIAC and EPM models. It became known that most parts of the watershed have been covered by fourth class erosion condition and a minimum area by one of the first calss.
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