SEDIMENT DEPOSITION ANALYSIS OF NAUMURE RESERVOIR

Abstract

The proposed Naumure Multipurpose project is located near Bhalubang of western Nepal. The project's benefits include hydropower production, irrigation, flood control and navigation. The proposed dam height of the Naumure reservoir is 165 m. Sedimentation deposition in reservoirs leads to the loss of the capacity of reservoirs, damaging the reservoirs and dam infrastructures thus, by sediment analysis such problems can be mitigated by making the policy. Therefore, this study aims to assess the sustainability of the Naumure multipurpose project with respect to the probable sedimentation in it. HEC-RAS 1D is used as the numerical modelling tool for the simulation of sediment transport. Rating curve calculator using HEC-RAS is used for obtaining sediment rating curve at Chernata station and Bagasotigaon station. The submergence is extended in the main and two tributaries, so sufficient length i.e. 2.21 km for main West Rapti, 25.46 km and 18.58 km for Mari and Jhimruk River respectively from Confluence point with Main West Rapti are considered for modelling. The Correlation coefficient obtained using observed and simulated sediment load at Bagasotigaon station for calibration of the model for three years (1985-1988) is 65.1% and the correlation coefficient using computed and simulated sediment load for Validation of model at Bagasotigaon station for three years (1990-1993) is 86.27%. Delta propagation deposition pattern is seen in the reservoirs. The percentage loss in the storage of Naumure reservoir for 10, 20, 30, 40 and 50 years are 0.61%, 1.46%, 2.39%, 3.37% and 7.4% respectively. The most influential and important five parameters: computational increment, transport function, maximum scour depth, sorting method and fall velocity method are selected for the sensitivity analysis. Among this transport function is the most sensitive parameter