STUDIES ON SEDIMENTATION IN A LARGE-SCALE RESERVOIR FOR POWER GENERATION

Abstract

The initial total storage capacity of 327 Mm³ of Sakuma dam reservoir in 1957 has been reduced to 213 Mm³ in 2002 due to sedimentation of 114 Mm³. In order to reduce flood damage in the upstream area caused by the sedimentation, attempts to lower the riverbed is being continued by dredging and flushing with river water. However, riverbed has not been lowered sufficiently, hence more efficient measures are required. So, accumulated reservoir data of flow discharge, cross sectional surveying and grain size distribution were examined to clarify actual state of the sedimentation. Results of the examination show that sediment concentration is decreasing clearly implying that a flood cannot convey the same amount of sediment as it could before. Another results of sediment movement were compared with those evaluated from 1-D analyses of non-uniform flows, indicating the efficiency of the sediment flushing. Accumulation curves of volumetric changes of cross sections were obtained for individual grain sizes, which can express sediment movement in the reservoir properly.