Numerical Simulation Of Coastal Aquifer Management Based On Sandbox Experiments

The coastal aquifer is the main source of freshwater resources in coastal areas,the management of which is of great significance to the development of society and economy in coastal areas.As the most extensive natural disaster in the coastal areas,seawater intrusion holds an important impact on the water resources in coastal aquifers.Through constructing the model of two-dimensional sandbox,this study focuses on the effect of extraction of underground saltwater near the interface of seawater intrusion on interface migration.In addition,numerical simulation is applied to study the control and prevention of seawater intrusion and optimizational mining on coastal aquifer groundwater.And thus,a multi-objective management system and reasonable suggestions are put forward for the management of coastal aquifers.Based on building an indoor sandbox physical model and color tracing techniques,the movement law of seawater intrusion into fresh-salt groundwater interface and the evolution mechanism of groundwater flow field under different saltwater-pumping strengths and well configurations have been analyzed in this paper.Furthermore,the control effect of pumping saltwater on seawater intrusion under different conditions has also been studied.The results of experiments showed that,because the groundwater flow field is influenced by different pumping intensities and well configurations,the best effect of pumping saltwater pulling to control seawater intrusion can be achieved by increasing the saltwater pumping intensity and optimizing the well configuration.With a certain fixed intensity of saline pumping,the effect of superimposed wells water pumping far away from the fresh-saline water interface does not have any advantage over that of the single well water pumping.When pumping saltwater at the upper part of the seawater body below the saline intrusion interface,it can prevent the seawater intrusion interface from moving to the inland during the seawater pumping;and it can accelerate retreating of seawater wedge toe towards seawater area to arrange wells to pump saline water at the location nearby the toe of seawater intrusion interface;and when remaining certain intensity of saltwater pumping,it can achieve the effect of integrative restoration of coastal aquifer to carry out dispersed well configurations at the upper and toe part of the seawater body below the saline intrusion interface.Through building the numerical simulation model of pumping underground saltwater against seawater intrusion,as well as analyzing the effect of the different saltwater pumping strengths under the same well configuration on the prevention on seawater intrusion,the result shows that the increase of saltwater pumping intensity can achieve the better control effect through pumping underground saltwater.However,when pumping saltwater reaches a certain amount of saltwater with high intensity,fresh water and saltwater will be mixed in the pumping well,gradually close to the fresh-saline groundwater wedge interface.In this paper,the Multi-objective Management System for Coastal Aquifer is constructed with a series of subsystems including database subsystem,evaluation model subsystem,numerical simulation subsystem,control technology subsystem,management scheme subsystem,etc.In addition,the decision and recommendations of coastal aquifer management are also put forward to providing technical supports for multi-objective management of coastal aquifers.