AN EXTENDED FORMULATION OF THE INTEGRATED FINITE-DIFFERENCE METHOD FOR GROUNDWATER-FLOW AND TRANSPORT

An extension to the integrated finite difference method, applied to tw o-dimensional problems, has been developed that permits a more accurat e approximation of the governing equations for groundwater flow and ma ss transport in heterogeneous anisotropic media. The method adopts a l inear two-dimensional interpolation over triangular elements for the n umerical evaluation of gradients at any point of the spatial domain. A pplications of the method are presented for various test cases. A comp arison is also made between the results obtained by applying both the extended method and the finite element method to the same test problem s. This comparison illustrates the utility of the extended integrated finite difference method for simulating flow in anisotropic media. The application of an automatic calibration procedure, based on Kalman fi ltering, to several test problems and the validation of the resulting models further confirms the advantages of the new formulation. The sou rces of error introduced by ignoring anisotropy in the integrated fini te difference method are found to be significant in the cases presente d.