CIRATA RESERVOIR LIFETIME PREDICTION USING NEW HYDROMETRICS AND SEDIMENT APPROACHES

By the year 2017 Cirata reservoir has already operated for more than 30 years with a lifetime plan of 100. 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, empiric method of reservoir lifetime was used alongside a new approach to predict the storage volume of a river in years coming by using a hydrometric and sediment approach. The result of Cirata Reservoir remaining lifetime using empirical method is 65 years, this number then used as reference to predict the remaining volume of Cirata Reservoir dead storage using sediment approach. Reservoir lifetime prediction by hydrometric and sediment approach uses the same principle by understanding that a reservoir lifetime is over by the time the dead storage full. What makes this approach differ from the empirical method is that this approach does not only focus on the when dead storage will be full, but also calculating or predicting the changes of storage volume in each elevation. Using this approach, the result shows that the volume of dead storage will already be full and exceeds its capacity by 41.9 x 106 m3 in the next 65 years. Then by using the same approach and by trials and errors, the time needed to fully fill the dead storage is 60 years, or the reservoir will be defunct in 2077.