Integrated numerical–physical modeling for optimizing riverbed dredging in Mixed Pumped-Storage Power Stations: a case study of Lianghekou project

The Mixed Pumped-Storage Power Station (MPSPS) constitutes an emerging strategy for the development of integrated clean-energy bases that combine hydropower, wind, and solar resources. However, a critical literature gap exists regarding effective engineering measures to mitigate the "pumping funnel" phenomenon in the lower reservoir, which remains a key operational challenge for MPSPS. Taking the Lianghekou MPSPS as a case study, this study proposes riverbed dredging as a mitigation measure and develops an integrated numerical-physical modeling approach for its optimization. The optimal scheme was selected based on a combined criterion of pumping-effect improvement and construction cost. The most promising scheme was further verified through large-scale physical model experiments of the entire lower reservoir. The results show that the selected riverbed dredging strategy substantially improves the pumping reliability of the Lianghekou MPSPS system, expanding the river's cross-sectional area by 15-23%, reducing reverse flow by 30-42%, suppressing pumping funnel depth to 65% of its original value, and increasing the continuous pumping duration by 61%. Within the context of the Lianghekou project, these findings provide a quantitative basis for engineering design, construction, and operational scheduling, while also offering potential reference for similar MPSPS applications in large-scale renewable energy integration.