A numerical modeling study of sediment bypass tunnels at shihmen reservoir, Taiwan

Abstract

Many reservoirs in the world were built years ago and losing their storage capacities At Shihmen reservoir Taiwan topological geological and seismological factors greatly increased sediment delivery to the reservoir A large amount of fine sediments entered the reservoir in the form of turbidity current Due to limited desilting facilities majority of the sediments deposited near the dam leading to a significant loss of the storage capacity Moreover extreme typhoon events produced sufficiently high sediment concentrations that water supply was interrupted causing social and economic problems A number of sediment management projects have been planned for the reservoir in order to extend the reservoir life and maintain water supply but few tools are available to understand the effectiveness of the proposed projects In this study a two dimensional D layer averaged turbidity current numerical model is presented and used as a reservoir evaluation tool The sediment bypass tunnel is the study focus as it has been proposed as an important sediment removal measure The model is presented and then validated using the available physical model data Once validated the model is used to evaluate the effectiveness of two proposed sediment bypass plans Further the physical model scale effect is investigated using the numerical model which is often unknown This study serves as a further verification that the newly developed D turbidity current model is robust and useful for practical project applications