Page - 278 - in Book of Full Papers - Symposium Hydro Engineering

COMMISSION INTERNATIONALE DES GRANDS BARRAGES ------- VINGT-SIXIÈME CONGRÈS DES GRANDS BARRAGES Autriche, juillet 2018 ------- EVALUATION OF SEDIMENT MANAGEMENT EFFECTIVENESS TO EXTEND THE WLINGI RESERVOIR LIFETIME Zainal ALIM Head of Internal Control Unit, JASA TIRTA I PUBLIC CORPORATION INDONESIA 1. ABSTRACT Wlingi Reservoir is one of the reservoirs in the Brantas River Basin management system. Besides as a flood control, this reservoir has an important role as a supplier of 2 x 27 MW of electrical and serves irrigation area of 15,132 Ha. The reservoir was completed in 1979 and has total storage capacity of 24 million m3, however due to severe sedimentation caused by Mt. Kelud eruption and critical catchment condition, by the year of 2016 its capacity decreased to only 2.55 million m3 or 10.63% of the initial capacity. To extend the economic lifetime of the reservoir, many efforts have been undertaken, including some preventive activities through conservation in the upstream areas as well as some corrective measurements. Some corrective measurements that have been done are sedimentation dredging (through spoil bank disposal and riverine disposal) and sedimentation flushing. Based on technical and financial aspect, sedimentation flushing is considered more efficient than the other measurements. Based on the technical evaluation, sedimentation flushing can remove approx. 300,000 m3 to 1,2 million m3 sediment per year from reservoir, which is higher than the sedimentation dredging that only remove approx. 100,000 to 350,000 m3 per year. Based on the financial evaluation, sedimentation flushing can save the cost of Rp. 35.85 billion compared to dredging with spoil bank disposal, while dredging with riverine disposal to channel below can save about Rp. 14.96 billion compared to the dredging with spoil bank disposal. Another advantage of sedimentation flushing is the supply of 278