Shimen Reservoir Reaches 100% Capacity After Typhoon Bailu, Saving NT$80 Million in Dredging Costs

Shimen Reservoir has reached 100% capacity following the passage of Typhoon Bailu, holding 205.95 million tons of water as of September 12. The reservoir's flood control operations, guided by real-time monitoring and hydrological forecasts, managed a total inflow of 39.86 million cubic meters and an outflow of 32.76 million cubic meters during the typhoon. This careful management reduced downstream flood pressure and maintained a stable regional water supply.

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During the typhoon, in addition to closely monitoring the weather and reservoir inflow changes 24 hours a day, we discussed water discharge operations with the New Taipei City Government Water Resources Bureau, Taipei City Government Water Affairs Bureau, and the Tenth River Branch of the Water Resources Agency on August 9 via video conference. The focus was on controlling downstream water levels to prevent flooding of high-risk areas and causing disaster damage. Simultaneously, large water releases had to be coordinated to avoid high tides in the Tamsui River, thereby reducing the drainage pressure on downstream areas.

During the typhoon, the reservoir's catchment area received 166 millimeters of rainfall. The North Region Water Resources Branch of the Water Resources Agency coordinated with local government water authorities and the Tenth River Branch to plan water discharge operations. Key considerations included controlling downstream water levels to prevent flooding of high-risk areas and timing releases to avoid high tides in the Tamsui River, thereby easing the drainage burden on downstream regions. Discussions with Taiwan Water Corporation also ensured the continuity of water supply, particularly addressing potential impacts of high turbidity.

Furthermore, the Amuping silt-flushing tunnel was activated on August 9, removing approximately 158,000 cubic meters of silt. This operation not only extends the reservoir's lifespan by mitigating siltation but also resulted in significant cost savings, estimated at NT$80 million, by avoiding the expense of transporting the dredged material to Taipei Port.

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We also discussed strategies with the Second, Third, and Twelfth District Management Offices of Taiwan Water Corporation to ensure a stable water supply, especially regarding the impact of high turbidity on the water supply system. Through close inter-agency cooperation, the reservoir operations during the typhoon did not cause downstream disaster damage and maintained normal water supply.

Despite the successful management of Typhoon Bailu, the North Region Water Resources Branch reminds the public that afternoon thunderstorms remain possible. The reservoir will continue to adjust water releases based on rainfall and real-time conditions. Residents are advised to monitor broadcasts and avoid activities in riverine areas to ensure their safety and protect property.

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By continuously monitoring reservoir inflow and sediment transport during the typhoon and taking advantage of the hydraulic conditions brought by the rainfall, we activated the Amuping silt-flushing tunnel for silt-flushing operations at 10 a.m. on August 9. This removed approximately 158,000 cubic meters of silt from the silt-flushing pool and discharged it into the sea. This not only functions to prevent siltation and extend the reservoir's lifespan but also saves approximately NT$80 million in silt dredging costs.