RESERVOIR SEDIMENTATION - A CASE STUDY OF WONOGIRI RESERVOIR (INDONESIA)

Abstract

Sedimentation of reservoirs is a matter of vital concern as it adversely affects the useful life of reservoir and benefits from the reservoir. The two aspects of the sedimentation problem, whose knowledge is essential, are the erosion rate from catchment and the pattern of deposition in the reservoir. These two aspects are addressed in this study Total global sediment discharge is about 14 x 109 tones/year (UNEP, 2003). The global suspended sediment discharges to sea range between 15 to 20 x 109 tones/year, where the best estimate may be about 20 x 109 tones/year (Takeuchi 2004). More than 25% of this sediment discharge may be trapped by large reservoirs. Matatila dam has already lost more than 38% of its live storage capacity. This dissertation study has focus on GIS based assessment of soil erosion from the catchment (1243.3 km2) of Wonogiri Reservoir and effect of sediment deposition on elevation-area-capacity relation. The Bengawan Solo basin- area is 16,100 km2 lying on both Central and East Java provinces, which covers approximately 12% of the total area of the Java, Indonesia, Objectives of this dissertation work are: i. To critically examine the Area Reduction Method for estimation sediment distribution in reservoir and analyse the effect of progressive sedimentation on elevation-area-capacity relationship of Wonogiri reservoir. ii. To assess soil erosion and its geographic distribution catchment of Wonogiri reservoir using GIS based estimation of R,K,LS,C,P factors and application of USLE model. iii. To use GIS based USLE model as a management tool for identification of critical areas and manipulation of C or and P factors to reduce soil erosion. iv. To predict deposition profile (longitudinal) in Wonogiri Reservoir using an empirical method..