Erosion index formulation with respect to reservoir life in the upper Citarum watershed

Bakhtiar Bakhtiar,D Roosmini,I.K Hadihardaja,B Sugeng,K Pribadi

doi:10.1051/matecconf/201814703002

Abstract

This study aimed to formulate erosion index in the upper Citarum watershed with respect to the Saguling reservoir life. Soil and Water Assessment Tool model was incorporated to simulate hydrological processes in the catchment. From the calibration and validation results, the model is considerably of good performance. The simulated sediment inflow at Nanjung outlet was then extrapolated to determine the sediment inflow into the reservoir. The study revealed that the average value of sediment inflow into the reservoir is 29.24 tonnes/ha/year just below the tolerable erosion limit of 30 tonnes/ha/year assumed by Hammer (1981). It was also found that the relationship between sediment yield and sediment inflow is non linear. Erosion index is formulated as the ratio between the mean annual sediment yield generated in the watershed and the mean annual sediment yield that leads dead storage to be full in the designated life of the reservoir. Erosion index equals to 1.0 indicates that the dead storage will be full in the designated life of the reservoir. A classification of erosion index can be subsequently be made based on erosion index and reservoir life relationship.

Highlights

The upper Citarum watershed covers the fountain of the Citarum river down to Saguling with an area of 1744.98 km2 as a part of the Citarum watershed, one of the biggest watershed in West Java
Erosion index (IE) is formulated as the ratio between the mean annual sediment yield generated in the watershed (Sed) and the mean annual sediment yield that leads dead storage to be full in the designated life of the reservoir (Sedt)
If the values of erosion index found in this study are compared to the values of erosion hazard index (Hammer, 1981 in Arsyad [5]), the same sediment yield will fall into a different category

Summary

Introduction

The upper Citarum watershed covers the fountain of the Citarum river down to Saguling with an area of 1744.98 km as a part of the Citarum watershed, one of the biggest watershed in West Java. The sedimentation rate in the Upper Citarum watershed in the last decade is reported to be increasing. It is indicated by the mean sedimentation rate of 4,048,132 tonnes per year (PT Indonesia Power [1]). This fact is due to the ecosystem degradation and the decreasing forest area over the watershed and the catchment of the Saguling reservoir. The aim of this study is to analyse the effect of rainfall and land use scenarios on sediment yied in the Upper Citarum watershed

Objectives

Methods

Conclusion