RATIONALIZATION OF DISCHARGE DATA FLUCTUATIONS USING MINIMUM RESIDUALS MODEL OF MOVING AVERAGE METHODS IN CITARUM CASCADE RESERVOIRS

Abstract

Since 1981, a cascade of dams consisting of the Saguling, Cirata, and Jatiluhur reservoirs has been
constructed along the Citarum River in order to fulfill demands for flood control, water supply, and electrical
power generation, and this requires the implementation of an appropriate hydrological approach. The efficient
operation of a water resource system requires an accurate water flow analysis that approximates the actual fact as
closely as possible to minimize risks in decision-making. Discharge is a random and stochastic component in
hydrology, influenced by rainfall variations with a maximum in the tropical wet season and a minimum in the dry
season. Thus, discharge analysis requires a statistical approach especially minimum residuals. Values for average
annual inflows has constructed through four different calculation techniques for the moving average method to
rationalize the fluctuations in discharge data Citarum cascade reservoirs by reducing randomness in the data, with
the eventual aim of obtaining more rational trend lines. An analysis of minimum residuals between the results of
the calculation and those of model regressions has demonstrated that the cumulative moving average calculation
technique provides the best fit among all the models with the smallest residual value, as shown in its lowest mean
squared error values of 0.83, 2.04, and 1.77 for the three reservoirs.