Modeling and simulation of watershed erosion: Case study of Latian dam watershed

The Latian Dam is one of the important drinking water resources of Tehran, and it also has a role in preventing the flood. It is very important to keep the quality of water and preventing the dam from filling. Considering the special aspects of RUSLE model, it was used for estimating the amount of erosion in the watershed of dam including the sub-basins: Jajrood River, Kond River and Afjeh River, and then compared with the actual values measured. The results of modeling show that the degree of erosion is high because of steep slopes, lack of plant coverage. The results of modeling the amount of erosion in The Jajrood basin have been estimated about 1,524 ton/year, in Kond basin about 228.5 ton/ year, and in the Afjeh basin about 103.1 ton/year. By using the results of the water samples analyses, the amount of phosphorus entering the reservoir by the rivers were calculated. This research shows that, by using the proper coverage in the basin, the amount of sediment and phosphorus entering the reservoir, decreases considerably. Key words: Latian Dam, phosphorus, reservoir.