A numerical modelling of seawater intrusion with a 3D density dependent model in Shenzhen

Over exploitation of groundwater resulted in seawater intrusion in coastal aquifer of Shenzhen city, China, during the 1980s and 1990s. In recent years, the improvement of water supply facilities alleviate seawater intrusion, however, it is still of great concern in some local region. A three dimensional density dependent numerical model using FEFLOW code has been developed to simulate the extent of seawater intrusion considering tidal effects and different groundwater pumping scenarios. Model calibration with water heads and chloride concentration has been performed using the monitored data from a total of 15 boreholes, recorded from May of 2008 to December of 2009. A fairly good fitness between the observed and computed values is obtained by a manual trial-and-error method. Model prediction has been carried out forward 3 years (till the end of 2013) with the calibrated model taking into account different groundwater exploitation schemes. The numerical results obtained from model prediction reveals a decreased tendency of seawater intrusion if groundwater exploitation is not enlarged, and a maximum exploitation quantity, 1.32 × 10⁴ m³/d, is obtained by comparing the simulated results from different pumping schemes in the study area. The results provide insights for controlling seawater intrusion in such coastal aquifer systems.