The Investigate Of Impacts Of Sea-level Rise On Seawater Intrusion And Its Control Measures

Sea-level rise,as an indicator and a consequence of global climate change,has a significant impact on seawater intrusion,which has caused widespread attention at home and abroad.Seawater intrusion has become one of the most serious environmental problems in the world,which seriously threatens the limited underground freshwater resources and restricts the socioeconomic development of coastal areas.Therefore,it is imminent to prevent and control the seawater intrusion.The main research contents and results are as follows:(1)First we established a gas-liquid two-phase flow and solute transport model to simulate the classical seawater intrusion problem and verify the validity of the model.(2)Numerical simulations were performed to investigate the impacts of sea-level rise on seawater intrusion in confined and unconfined coastal aquifers under three inland boundary conditions(flux-controlled,head-controlled and general-head boundary)and then we determined the reasonable boundary condition and compared with analytical solutions.The simulation results show that:In both confined and unconfined coastal aquifers,seawater intrusion is remarkably vulnerable to the effects of sea-level rise owing to the resulting decreased head difference under head-controlled systems,while it is almost not change with the rise of sea level under flux-controlled systems because the equivalent freshwater head at the inland boundary can increase by a similar magnitude to the sea-level rise and the extent of seawater intrusion due to sea-level rise under general-head boundary is between the other two.The general-head boundary is more realistic than the other two boundary conditions: the recharge decreases because of sea-level rise depending on the aquifer properties and the head difference between the reference head and the equivalent freshwater head at seaside boundary.The results of the numerical simulations under the general-head boundary are significant different from the analytical solutions because of the different principles they based on.(4)Finally,a three-dimensional numerical model was established combined with the actual coastal stratum to study the effects of abstraction of saline water,recharge freshwater,the combination of abstraction and recharge,aeration method on the prevention and controlling of seawater intrusion.And the study results indicate that the effect of abstraction of saline water on prevention and controlling seawater intrusion is limited.They are both very effective measures to prevention and controlling seawater intrusion for recharge freshwater and the combination of abstraction and recharge.What is more,the latter effect is better.Although the aeration method has the best effect against seawater intrusion in the numerical simulation and it not only saves freshwater resources but also economizes money and no pollution,the technology still needs to be further improved in practical application.