Abstract
This paper studied finite difference numerical methods for threedimensional unsaturated subsurface flow model. The equation is mathematically classified as a type of heat diffusion equation. Therefore three-dimensional numerical methods for heat diffusion equation can be applicable to solve the flow equations. For the numerical methods, purely explicit method, ADE methods, and ADI methods are investigatedi n terms of accuracy, stability, and calculation time using analytical solutions for the linearized equation by Philip. As a results of comparison among the five numerical methods, ADE method proved to be the most excellent.
