The benefits of river normalization of Guntur weir upstream to irrigation area service in Demak Regency Central Java Indonesia

Abstract

Guntur weir is located in Demak Regency, Central Java Province, Indonesia. The damage occurred in the upstream of Guntur Weir, mainly due to sedimentation. The cross-sectional area of the river becomes smaller so that when heavy rainfall, river water overflows and breaks the levees. These problems also disrupt water supply to irrigation channels where sedimentation covers the entrance of the Guntur Intake Weir. The purposes of this study are to determine the condition of the Guntur weir before and after the normalization work, the benefits of the Jragung river normalization work. This study was performed by analyzing hydrological data to find out the water balance, flood discharge, and the benefits analysis of the Jragung River normalization work. Based on the analysis using the HEC RAS application at Guntur Weir, an increase of Guntur Weir storage from 1002.5 m3 to 88280.525 m3. Flood discharge calculation using the HEC RAS application shows normalization work has benefits to reduce the potential flooding in the upstream of the Guntur Weir and also increase the ability of Guntur Weir to supply water needs for the Guntur Irrigation Area. The result used to adapt the operation Guntur Weir gate.