THE EFFECT OF SEDIMENTATION IN CIRATA RESERVOIR TO ITS EFFECTIVE LIFETIME AND THE DESIGN OF SAND TRAP TO MAINTAIN THE REMAINING LIFETIME

• Main Author: Dio Oriandra, Regina
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/43126
• Institution: Institut Teknologi Bandung

By the year 2017, Cirata reservoir has already operated for more than 30 years with a lifetime plan of 100, supposedly Cirata Reservoir’s lifetime still has 70 years left. The annual sedimentation rate plan of Cirata Reservoir was 5.7 x 106 m3, but as calculated in 2017 the annual sedimentation rate increased to 8.4 x 106 m3, which has increased 77.78%. To predict the remaining lifetime of Cirata Reservoir, the empiric method of reservoir lifetime was used, the result of Cirata Reservoir remaining lifetime using empirical method is 65 years which means the dead storage will be filled in the year of 2082. This essay also uses method by hydraulics and sediment approach to calculate reservoir’s lifetime by predicting the changes of storage volume in each elevation, with this approach the time needed to fully fill the dead storage is 60 years, or the reservoir will be defunct in 2077. The measure taken to solve this problem is to construct sand traps in the upstream river. By emphasizing on sediment that fall into dead storage, sediments that needed to be settled before entering the reservoir is around 0.57 x 106 m3. Each upstream rivers of the reservoir have different percentage of sediment contribution into the reservoir, which are, for Cikundul River the percentage is 8,47%, for Cibalagung River is 6,42%, for Cimeta River is 7,73%, and for Cisokan River is 77,38%. By considering how substantial each river contribution is, two alternatives were planned. Which the first alternative is to construct sand traps in every upstream rivers, with storage area divided according to the contribution percentage, and the second alternative is to construct only one sand trap in the river with the highest contribution percentage, by settling the entire 0.57 x 106 m3 of sediment that needed to be settled before entering the reservoir. With the construction of sand trap, sediment rate that entering the reservoir is reduced, making the remaining age of the reservoir which only had 60 years left has now returned to normal, that is Cirata Reservoir lifetime now have 70 years remaining.