Using hydraulic-based countermeasures to increase sediment fluxes in a reservoir desilting operation

This study focuses on the Nanhua Reservoir, where a two-dimensional numerical model was developed and validated to evaluate desilting efficiency under various operational strategies during Typhoon Lupit. The research highlights the critical role of a dredged guiding channel in enhancing turbidity concentration near the dam, which significantly improved desilting performance. The incorporation of this channel increased sediment desilting efficiency during sluicing operations. It reliably reflects turbid water transport dynamics and sediment load patterns. Simulation outcomes revealed that sediment transport time under flood mitigation operations was shortened by 5.5 hrs. The sluicing operation yielded the highest desilting efficiency of 16.47 %, while free overflow conditions had the least impact. Notably, the desilting tunnel demonstrated superior performance over the spillway for comparable outflow volumes, achieving the highest sediment concentration ratios during sluicing. Key strategies identified for maximizing sediment discharge benefits included the early activation of the desilting tunnel during high turbidity inflow events and increasing discharge rates. The sediment transport analysis indicated reduced concentrations during reservoir passage, with a strong correlation between upstream inflows and critical measurement points within the reservoir. These findings underscore the importance of integrating dredged guiding channels and optimizing desilting tunnel operations to improve sediment control during high inflow events and elevated reservoir levels. This research provides new hydraulic insights for effective reservoir sediment management, contributing to sustainable water resource management in sediment-impacted regions. • Dredged guiding channel greatly improved reservoir desilting efficiency. • Early tunnel use and higher flow during turbidity peaks boost sediment discharge. • Dredged channels and tunnel control aid sediment management in high-inflow periods.