Numerical Modeling of Tidal Effects on Groundwater in the Coastal Aquifer of Donghai Island
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In coastal region, tide takes an important role to affect the dynamics of the groundwater flow and saltwater transport. To analyze tidal effects on groundwater flow and saltwater transport in the unconfined coastal aquifer of Donghai Island, we develop a two-dimensional, finite-difference groundwater model. The model which is based on density-dependent fluid flow theory considers dynamic tidal boundary conditions and sloping beach surface. We simulated groundwater flow and the salt concentration distribution which forms the salt wedge in the coastal aquifer, as well as analyzed the dynamic characteristics of the groundwater flow and the salt concentration distribution during the flood-and-ebb process. Simulations indicate that fluid velocity in freshwater is greater than that in saltwater. Velocity decreases with depth, but increases along the freshwater-saltwater interface or dispersion zone in the coastal aquifer. Tidal action drives seawater recirculation through the intertidal beach zone, thereby creating an upper saline plume in the aquifer. And the water table in the upper saline plume area is higher than that in the freshwater area.
KeywordsTidal effects Groundwater flow Salt concentration distribution
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