Length optimization of Desilting Basin – A case study

Abstract

The high sediment carrying rivers cause difficulty in developing hydropower as projects on these rivers deal with high sediment-laden water that is withdrawn for power production. This results in severe damage to the turbines and other underwater components, requiring significant maintenance expenses that have an effect on their overall economy. To overcome the sediment problem in such projects, a viable solution is to pass the water through desilting basins before its entry into the head race tunnel and ultimately to the power house. The majority of the hazardous sediment is removed using desilting basins, which helps to reduce the amount of sediment that hydraulic machinery is exposed to. Additionally, these basins guarantee the consistency of power output, particularly during the monsoon season when rivers carry large amounts of sediment. Increased cross-section of the desilting basin lowers the mean flow velocity inside the basin, causing suspended sediment to settle. The water enters the basin by widening its breadth and lowering its floor via an inlet transition, and it exits through an outlet transition at the basin's end. A desilting basin's performance is assessed by looking at both its settling efficiency and flushing efficacy. These desilting basins are enormous and expensive structures, so their design must be verified on a physical model to ensure optimal design and performance. This study focuses on the optimization of the length of desilting basin by examining its settling efficiency with the help of model studies for Kholongchhu H.E. Project, Bhutan.