CIRATA RESERVOIR LIFETIME PREDICTION USING NEW HYDROMETRICS AND SEDIMENT APPROACHES

Abstract

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.