Research On Seawater Intrusion Model Considering Rainfall Effect

The groundwater environment system of the costal zone is a complicated system which includes the freshwater environment, the tide environment and the salt-fresh water environment system. In recent years, for the activity of the human has been more and more continually which caused the research of the groundwater environment system of the costal zone became a focus of the academe. Groundwater is not only an important proportion of the water cycle, but also an indispensable nature resource, for the steady supplement and the well quality, it becomes more and more important in the social development and the people's daily life. With the rapid growth of the population and the fast development of the industry production, the exploited range of the groundwater grew day by day, and caused a series of geological disaster and environment problem, the seawater intrusion is one of the outstanding environmental geology problems in the costal zone and many islands. Based on the theory of predecessor, in the dissertation, the seawater intrusion model and the solute travel model under the precipitation leach condition were established, the hydrodynamic dispersion coefficient was determined, and the solute travel equation was derived, in terms of the boundary conditions, the equation was solved, compared with the field test, the correctness of the model was verified. Through summarizing and analyzing the experimental data, according to the advection-dispersion solution, using analytic solution, studied the solute travel rule in the soil, and summed up empirical formula, described the decay process of the solute concentration in company with the time. Aimed at the travel behavior, such job was carrying on as follows:(1) Based on the essential character of the groundwater in the costal zone, analyzed the mechanism of seawater intrusion, and established the unstable seepage equation of seawater intrusion model, solved the analytic solution. Analyzed the factors which influence the concentration change of groundwater, derived the concentration distribution of the costal groundwater. Using the approximate formula of error function to derive the travel parameter of groundwater, determined the dispersion coefficient and the delay factor.(2) Considering influence which caused by the precipitation leach, analyzed the infiltration condition, established the control equation of the moisture movement in the soil, and solved the analytic solution. Analyzed the factors which influenced theinfiltration intensity, and analyzed the expression of the infiltration, verified the correctness of the infiltration solution of the Green-Ampt model. According to the Green-Ampt model, established the unstable seepage equation considered the precipitation, and solved the analytic solution. Established the vertical saline matter model considered the precipitation leach, and solved the analytic solution.(3) Determined the control equation of the two dimensional tidal movement of the groundwater, according to the different boundary condition, established the finite solution equation of the two dimensional tidal movement, which concluded a quarter of quadrant model and half plane model, using Green function and separation of variables to solve the equation separately, and derived the function of water head in company with the time. Put forward a theory and method to solve the tidal movement of anisotropic aquifer using a concise mathematical manipulation.(4) Combining with the engineering example, established the solute travel model, and used the field experiment data to verify the correctness of the model.