Pemodelan Debit Menggunakan Metode Arima Guna Menentukan Pola Operasi Waduk Selorejo

Abstract

Selorejo dam is located in the village of Pandansari, Ngantang Sub Regency, Malang Regency. It is located in Kali Konto, a tributary of the Brantas River. Selorejo dam has a very important function, especially for the purposes of hydroelectric power generation and irrigation. As an old dam, completed in 1970, Selorejo experiences a decreasing volume of its reservoir due to a high sedimentation rate. The decreasing volume Selorejo reservoir has impacted the function of the dam and it is important to formulate a better operating rule to optimalize the current volume. During the planning of the operating rule of Selorejo reservoir, Perum Jasa Tirta I as an operator of the Selorejo Dam use a dependable discharge in predicting inflow discharge. This study predict the inflow discharge using ARIMA forecasting method, which then used to formulate a new operating rule. This study used 10 years of 10 days period inflow discharge data, which 9 years of it used to generating the ARIMA model and the last 1-year data for calibration. The study result suggest that the best ARIMA model in predicting the dam’s inflow discharge is ARIMA (1,1,1)(2,1,1) 36. Compare to a current method, this model is proved predicts better inflow discharge which has smaller Relative Error (KR) to the real data (Model’s KR 5.5 and Operator’s KR 17.8).

Keywords: ARIMA, inflow discharge, the operating rule of reservoir, reservoir of Selorejo Dam.