THE EFFECT OF SAND TRAP ON SEDIMENTATION DISTRIBUTION OF CIRATA DAM TO MAINTAIN THE RESERVOIR AGE OF USE

Cirata Reservoir is one of the largest reservoirs in Indonesia.This study aims to perform a numerical analysis of the sedimentation distribution pattern based on geometry, sediment, and discharge of the Cirata Reservoir.Numerical analysis was performed using SSIIM-2 (Sediment Simulation in Intakes with Multiblock Option) software.From the simulation results of 5 years from 2013 to 2017, an average addition of sediment volume was 8.966 million m 3 /year.When inspected from each river inflow of Cirata Reservoir, the distribution of the contribution of sedimentation in the Cikundul River, Cibalagung River, Cisokan River and Citarum River are 12.19%, 20.34%, 28.39% and 39.07%respectively.From the analysis of the sedimentation distribution to the position of the dead storage in the reservoir, it was found that of the total sediment that entered Cirata Reservoir, only 4.10% reached the elevation of the dead storage in the downstream area of the reservoir.These results were used to determine the appropriate sedimentation treatment pattern, with the treatment recommended being a sand trap.The sand trap type recommended for sediment treatment would be located downstream of each river at inlet to the reservoir.These sand traps are expected to withhold up to 70% of sediment that would settle in the reservoir.