System Dynamics Simulation Model for Flood Management of the Three Gorges Reservoir

The operation of Three Gorges Reservoir (TGR) during flood seasons is of high importance for ensuring the wellbeing of the people living in the downstream flood-prone areas. Therefore, protecting the downstream areas from flooding is the primary focus of TGR operation. Understanding the interaction between the benefits of flood control and the impacts of flood regulation on the local environment can help improve the operation of the TGR during the flood season. A system dynamics (SD) flood management simulation model of the TGR (SD_TGR) was developed in this study to explore how the operation of the TGR benefits the flood-prone areas and affects the local environment. Scenario-based simulations were performed with the SD_TGR model to understand the interactions between flood control, fish production, sediment flushing, and potential landslide risks under different events during the flood season. Results show that current operation that purely focuses on protecting downstream from flooding causes significant risks of landslides and significantly impairs the production of carp eggs during extreme flood events. The scenario that maintains the natural flow regime for carp spawning results in a substantial increase in the yield of carp eggs at the cost of potentially downstream alert flooding, but it has no impact on downstream critical flooding. The scenario of sediment flushing policy significantly reduces reservoir sediment accumulation, especially during extreme flood events, but its impact on downstream flood warning and critical flooding should not be ignored. The scenario of controlled reservoir drawdown rate reduces the risk of landslides at a considerable degree during small flood events without significantly impairing TGR's flood control performance.