Analysis of the Partition Method in Reservoirs to Enhance Operation and Maintenance Efficiency at the Mengkoang Reservoir

Abstract

Dams are one of the critical infrastructures for water resource development extensively developed in Indonesia. As hydraulic structures, dams function to store river water in a reservoir and can also serve as hydroelectric power plants, flood control systems, and recreational areas. One dam experiencing sedimentation is the Mengkoang Dam, which is administratively located in Lape Village, Lape Lopok District, Sumbawa Regency. The Mengkoang Reservoir serves as a source of irrigation for the surrounding villages' plantations and agricultural activities. River sedimentation affects the reservoir's function; hence, sediment-related issues must be addressed promptly as they cause sand accumulation in the dam's water channels, disrupt irrigation flow, and shorten the dam's lifespan. To address these issues, a sedimentation control system was implemented to concentrate sediment at a specific point. This study requires geographical, geological, and climatological data to assess the conditions around the Mengkoang Reservoir. Hydrological and hydraulic analyses are then conducted to calculate rainfall, water discharge, and sedimentation rates occurring in the Mengkoang Reservoir, which are applied using the HEC-RAS 2D application. HEC-RAS is one of the tools used to model sediment flow. The modeling results indicate that a concrete sediment control system can retain 80% of sediment but causes backwater, while a system using gabions can retain 65% of sediment with less backwater effect. Based on sedimentation analysis, the sedimentation rate is 1,838 tons/year under original field data conditions and 1,541 tons/year with the sediment control system.

Keywords: HECRAS, Hydraulics, Hydrology, Mengkoang Reservoir, Sedimentation.