Sedimentation in reservoirs is a prerequisite for sustainable water management. The Dez dam is very important the country because of its role in electricity frequency adjustment. The main objective of this research is to identify the sources of sediment in the catchment using satellite images, GIS and hydro-geological information. For this purpose, the lab results of sediments mineralogy revealed that 75 percent of sediments constitute calcite, dolomite and quartz. By processing the ASTER images and applying the methods such as Band Ratio, SAM and PCA sediments resources were identified and by matching geologic formations lithology formations of the study area accuracy of the results were verified. However, the quartz mineral could not be enhanced using the mentioned methods due to its low absorptance and reflectance in visible and infrared regions For this reason the band composition (RGB) (10, 12, 13) method was applied and the best results were revealed based on the Optimum Index Factor (OIF) which then demonstrated the high purity quartz area in red and the mid purity in pink color. The results concluded that the satellite images can be a useful tool to identify sources of sediments in the reservoirs dams.