Adaptive gate operation for salinity control and flood management in the Cai Lon–Cai Be system, Vietnamese Mekong delta

ABSTRACT

Conceptual schematic illustrating adaptive gate operation in the Cai Lon-Cai Be hydraulic system of the Vietnamese Mekong Delta. The diagram shows dry-season and wet-season operational strategies, including early gate closure for salinity control, controlled saline intake for shrimp-rice aquaculture, coordinated freshwater flushing during severe intrusion events, and tidal-cutting operation for flood drainage. The figure highlights the role of forecast-informed and regionally coordinated hydraulic regulation in reducing salinity intrusion, improving inland drainage efficiency, and supporting climate-resilient water management in a low-gradient tropical delta system.

The Cai Lon–Cai Be hydraulic system is a major tidal-control infrastructure developed to regulate salinity intrusion, flood drainage, and water allocation in the Ca Mau Peninsula of the Vietnamese Mekong Delta. This study applied a coupled MIKE 11/21 hydrodynamic–salinity model to evaluate adaptive operational scenarios under representative hydroclimatic conditions during 2020–2023. Model calibration and validation showed satisfactory agreement between observed and simulated water levels and salinity, with Nash–Sutcliffe efficiency values generally exceeding 0.80 for water level and 0.70 for salinity. Simulation results showed that early gate closure reduced peak inland salinity by 20–35%, while coordinated emergency flushing reduced saline persistence by 30–50% during severe intrusion periods. Controlled saline intake maintained suitable conditions for shrimp–rice aquaculture without major upstream freshwater instability. During wet-season events, adaptive tidal-cutting and coordinated drainage operation reduced inland peak water levels by 10–25 cm and improved regional drainage efficiency. Coordinated regional operation substantially improved hydraulic stability compared with isolated local control. The results highlight the importance of adaptive and forecast-informed operation for climate-resilient water management in tropical tidal deltas.