Seite - 302 - in Book of Full Papers - Symposium Hydro Engineering

SETTING UP DREDGING AND SPOILBANK MANAGEMENT METHOD TO RECOVERY HYDROPOWER PRODUCTIVITY OF SENGGURUH DAM Aris Yhadhianto Civil Engineer, JASA TIRTA I PUBLIC CORPORATION, INDONESIA INDONESIA Ulie Mospar Dewanto Deputy of Operational II, JASA TIRTA I PUBLIC CORPORATION, INDONESIA ABSTRACT Sengguruh dam located in Brantas River watershed, East Java, Indonesia was completed in 1988. The objectives is for generating hydroelectric power plant with installed capacity 2 x 14,5 mW produce of 91 million kWH per year. Located at uppermost of the series dams in Brantas River Basin and therefore is utmost suffered of sedimentation. Also, it prevents sediment comes to the Sutami which is the biggest reservoir at down stream part. The inflow come from two main rivers, namely Brantas River and Lesti River has a catchment area of 1.659 km2. The condition currently declining due to the high rate of sedimentation. Based on the echosounding result conducted in 2016, is known that effective capacity has been reduced to 0,6 million m3, or approximately 24% of the initial conditions of 2,5 million m3 and electric generation has been reduced to 68,8 x 106 kWH. The dredging activity has been done routine every year from year of 2001 with an average dredging volume of 300,000 m3/year. Total achievement of the volume of dredging result seems large, but it is not adequate. Based on the present evaluation, particularly in the zone at front of hydropower intake (namely zone 1), was in fact already quite critical because the sediment is getting closer. The zone distance is about 100-200 m with the difference elevation from sediment surface reaching 7-12 m above desired reference base elevations. On contrary, the dredging has been done in the upstream area which is quite far away + 1,500- 2,000 m from zone 1 due to get close of spoilbank location. In order to sort out the problem and to support President Joko Widodo's Government policy in energy security, the dredging method in 2016 was changed. The innovation and 302