Page - 222 - in Book of Full Papers - Symposium Hydro Engineering

COMMISSION INTERNATIONALE DES GRANDS BARRAGES ------- VINGT-SIXIÈME CONGRÈS DES GRANDS BARRAGES Autriche, juillet 2018 ------- DETERMINATION OF CONTROL WATER LEVEL ON SUTAMI AND LAHOR RESERVOIR TO AVOID THE POSSIBILITY OCCURS OVERTOPPING DUE TO PROBABILITY MAXIMUM FLOOD Ulie Mosphar Dewanto 1), Arief Satria Marsudi 2), Rahmah Dara Lufira 3) Deputy Operational II of Jasa Tirta I Public Corporation 1), Civil Engineering Expert of Jasa Tirta I Public Corporation 2), Lecturer in Water Resources Enginering of Brawijaya University 3) INDONESIA 1. INTRODUCTION Sutami Dam and Lahor Dam is located on Malang Regency, Province of Jawa Timur, Indonesia. This study needs to be done considering the extreme weather changes in recent years and the issue of global warming in the last decade that impacted the high intensity of rainfall and the change of land use in the upstream which affects the rise of runoff so that the flood discharge in the river becomes larger. Beside that, Sutami Dam and Lahor Dam at the time of planning (1975) is still designed with 1000 year return period of flood, while the dam safety standard set by the Dam Security Commission is currently the flood discharge of Probability Maximum Flood (PMF). it is necessary to raise awareness of the possibility of a PMF by evaluating the spillway performance of the PMF discharge that exceeds the initial flood discharge. So that the effort of awareness raising that can be done by the dam operator is by maintaining the Control Water Level (CWL) of the reservoir, so that during the PMF discharge, the reservoir can still reduce the flood and the overtopping can be avoided or the frequency can be reduced minimally. It is an effort to manage the dam safety in the Brantas River Basin. 222