Numerical Simulation of Sediment Yield and Reservoir Sedimentation Under Varied Hydrological Conditions: A Case Study of Shimen Reservoir, Taiwan

The sedimentation issue in Taiwan's reservoirs has been a longstanding problem, significantly diminishing the operational lifespan of these reservoirs and impacting the water supply to the northern regions. To project future sedimentation trends at Shimen Reservoir, this study utilizes numerical simulations to estimate sediment yield, taking into account both landslides and soil erosion. Aerial photography and depth-area relationships were employed alongside a landslide risk assessment of the upstream Sqzyacing watershed to evaluate landslide-derived sediment. Furthermore, this research implemented the Universal Soil Loss Equation (USLE), integrating future rainfall projections from the Taiwan Climate Change Projection Information and Adaptation Knowledge Platform (TCCIP) and streamflow data from the past decade to calculate soil erosion rates. Sediment dynamics within the Sqzyacing watershed were modeled using the SRH-2D hydrodynamic simulation, with parameters such as flow velocity, average slope, and watershed area aiding in the sediment yield estimates from individual sub-watersheds. Accompanying these calculations, sediment yields for Shimen Reservoir under various flow conditions, including Q5, Q10, Q25, Q50, and Q100, were estimated.