Sediment management and desilting strategies for Wushe Reservoir

Wushe Dam is a key component of the Zhuoshui River hydropower system, located in the upper reaches of the Zhuoshui River, Ren’ai Township, Nantou County, Taiwan. Wushe Dam was built in 1959 and has been in operation for over 60 years. The average annual sediment rate is 1.76 million cubic meters per year, causing the reservoir bed near the dam area to rise by 1.3 meters per year. The reservoir capacity was reduced to 28.686 million cubic meters by 2023, down from its original design capacity of 150 million cubic meters. This sediment problem has significantly impacted the key functions of Wushe Dam, including power generation, flood control, irrigation, and public water supply. To address the sediment issue and maintain the capacity of Wushe Dam, a comprehensive sedimentation prevention strategy was implemented, involving the flushing of 750,000 cubic meters of sediment per year, land excavation of 200,000 cubic meters per year, and dredging of 600,000 cubic meters per year from the reservoir. Following thorough evaluation, a sediment bypass tunnel (SBT) was selected as the solution for hydraulic sediment flushing. Furthermore, the tunnel not only helps achieve the goals but also increases the dam’s flood discharge capacity by an additional 530 cubic meters per second.