Determination Of Paleo-saltwater Intrusion Processes By Use Of Deterministic And Stochastic Models

The research addresses the problem of paleo-saltwater intrusion in a confined aquifer in the Liao River Basin. The transverse and longitude dispersity coefficients of the aquifer were initially estimated using results of field tracer tests (which used Cl- as the tracer) and curve-fitting methods. The tests showed that even in the case of a homogeneous aquifer, the scaling effect of diffusion coefficient is significant when using the conventional solute transport equation based on Fick's law.As a result, the scaling effect was considered during a Modflow simulation by recociling the scale of the mesh units and the field test. To determine the saltwater intrusion rate, the location of the 250 mg/L contour line was monitored in a network of boreholes with different extraction (pumping, well-spacing, and well-structure) strategies.To determine when density will have a noticeable effect and to what extent, the spectral method was used in the calculations of concentration variance. It was concluded that the influence of density depend on the gradient of the density and Peclet number.(or the convection and dispersion.) The influence is noticeable when density gradient is lower than about 0.5. This means that in the dispersion-dominant transportation, the density play more role to the groundwater flow when compared to the conversion-dominant flow. However, as the density gradient continue increase, the influence of the density refuse to progress any more and maintain in a certain value, which relate to the spatial variation of hydraulic conductivity (K). Correspondly. the relationship between the "maximum density gradient" and Pe has been concluded asηGmax=13.039Pe,0.3748Use SATRU to simulate the macro-density-dependent flow to determinate the average distribution of the choloride and express the result in the formation of moment by use of spectral and Monte Carlo method. Beside, it is concluded that the concentration gradient is the main factor affecting the degree of density influence. Within density coefficient of 850 kg-/kgm3.when the gradient is less than 3mg/L-m. the density influence can be ignored.