A River Network-Estuary Coupled Numrical Modeling System And Its Application On Pearl River Estuary

River, estuary and shallow sea composes a consecutive and integral water system, in which multiple forces (river discharge, tide, wave, wind, etc.) and different natures (temperature, density, salinity, etc.)coexist and interact with each other. Its dynamic is rather comprehensive. Further more, the Pearl River Estuary (PRE) is a multiple river/estuarine system with complex coastal geometry and abruptly varying bathymetry. These pose a great challenge for researchers to develop a computationally efficient and accurate numerical modeling system for the synchronous simulation of this integral and consecutive water system of PRE, especially its application on seawater intrusion.In order to study the physical mechanism and spatial/temporal structure of the seawater intrusion at PRE, A river network-estuary coupled numrical modeling system has been developed in this paper. For gaining computational efficiency, the river network is treated as one-dimensional and a one-dimensioanl river network model has been developed firstly. For keeping the vertically stratified nature of the estuarine hydrodynamics, and computational efficiency as well, a three-dimensional unstructured-grid Finite-Volume Coastal Ocean Model (FVCOM) is introduced and utilized.These two individual models are coupled through the principle of the conservation of mass, and that of momentum, at their interfaces. By doing so, a good balance between accuracy of large-scale simulation and computational efficiency has been properly achieved. The newly developed modeling system is then tested for the Pearl River and its estuary. Good agreements between calculated results and field data indicate that employing this coupled modeling system is highly efficient and capable of capturing dynamic processes of the entire water system correctly.Then, the developed numerical modeling system has been successfully applied to the simulation of seawater intrusion in PRE.According to calculated results, the basic mechanism of seawater intrusion in PRE has been indicated that the diluted water drifts westward following the ebb tidal current and seawater mainly intrudes upward into estuarine bays from east-south. In addtion, several process-oriented model runs has been conducted to study the effect of river discharge, bathymetry and wind on seawater intrusion.