Author(s): Sudesh Dahal; Frederic M. Evers; Robert M. Boes; David F. Vetsch

Linked Author(s): David Vetsch, Robert Boes

Keywords: Reservoir sedimentation; Sediment-Bypass-Tunnel; Numerical modelling

Abstract: Sustainable operation of many hydropower reservoirs is impacted by reservoir sedimentation which is not only causing a reduction of storage capacity but may also impair the functionality of dam outlets thereby implicating dam safety issues. Sediment Bypass Tunnels (SBTs) represent an effective countermeasure to mitigate sedimentation problems as they allow for bypassing incoming sediment (bedload and parts of the suspended load) around the dam into the tailwater reach. This study considers the Solis reservoir (Switzerland) which has effectively implemented an SBT with intake within the reservoir (type-B SBT) for managing high sediment inflow. The aim is to evaluate the performance of the Solis SBT by conducting 1D numerical simulations. The results show that a 1D model can closely reproduce the processes of sedimentation and SBT operation. Furthermore, the effect of the reservoir water level on SBT efficiency is assessed by conducting a scenario simulation. We found that the reservoir water level has a major impact on the SBT efficiency. For type-B SBTs, synchronous lowering of water level is recommended during SBT operation to ensure effective sediment bypassing.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0190-cd

Year: 2023