Assessment on the efficiency of sediment flushing due to different timings (a case study of Mrica reservoir, central Java, Indonesia)

The issue of the sedimentation problem of reservoirs has been growing significantly during the last two decades, particularly in areas where human activity increases pressure on the land. However, some researchers believe that such situation is also (partly) affected by the significant shift in hydro-meteorological conditions, accompanied with higher rainfall erosivity and hence an increase in land erosion. Various efforts have been suggested to control the erosion process, whether by sediment control at the catchment area or placing a ground sill and/or check dam in the stream. However, additional activities to remove sediment from reservoirs through sluicing, flushing, and dredging are often still necessary. This paper deals with the evaluation of the effectiveness of flushing at different timings. The results showed that the uncertainty of the sedimentation process and the hydrograph inflow characteristics are dominant factors affecting the problems. A further recommendation is to determine the procedure for establishing reliable advance timing that is considered most efficient for carrying out the flushing activities.