Numerical modeling of flushing process in Dez Dam reservoir by HR wallingford method

Dez dam is one of the key dams in Iran. It is 203 m high with a reservoir of 2.3 BCM volume. This double arch dam has been constructed in a narrow gorge in 1962, southern west of Iran. It has three irrigation outlets at level of 222.7 m asl, two power intakes at elevation of 270 m asl. No bottom outlet have been designed and installed for Dez dam and consequently the sediment-entering reservoir cannot be evacuated easily. Considering an annual 15.8 million cubic meter sediment inflow into the reservoir, the bed level is increasing about 1.2 meter per year and therefore it is very necessary to take an appropriate measure saving dam reservoir. One of existing method to save dam reservoir is to flush the sediment out through existing bottom outlets. In this study, the feasibility and efficiency of pressure and free flow sediment flushing techniques have been studied and some good points are presented. The results of present study shows that the flushing method cannot resolve the sedimentation problem of Dez dam and it must be applied jointly by other methods to save the reservoir from being decommissioned.