Desilting Basin Efficiency Estimation for Run-of-River Small Hydropower Plants

Abstract

Suspended sediment concentration and discharge are important factors affecting the operational reliability of run-of-river small hydro power (SHP) plants. Elimination of sediment transported with the flow across the turbines of run-of-river plants is therefore a critical issue for the sustainability of the SHP industry. Comprise of a small diversion weir throughout a stream, the SHP plants does not have space to pile sediments but should be able to divert the incoming bed loads to the river downstream. Sediments in the water entering through the turbines with extreme velocity erode the contact surfaces of turbine mechanisms which results in reduced hydraulic efficiency and increased maintenance cost. Subsequently, desilting basins have become an essential part of the water conductor system of run-of-river SHP to reduce the impact of damage due to suspended sediment. Desilting basins are devised as settling basins to settle sediments larger than a targeted size. They are constructed just after power intake and discharge is despatched through them before pass into the head race tunnel. This study is aimed to estimate the sediment removal efficiency of SHP desilting basins based on data recorded at the intake of a run-of-river SHP. Considering the hydrological variability, probabilistic approach was used to obtain mathematical function for the probability density of suspended sediment concentration (SSC) based on the recorded data.