Direct solution algorithm for the two-dimensional ground-water flow model

Abstract

Alternating diagonal ordering of node points for a two-dimensional finite-difference model of ground-water flow can be used to produce a direct solution algorithm that is computationally more efficient than iterative methods for moderately sized grids. Comparisons with the strongly implicit procedure, line-succesive overrelaxation, and the iterative alternating direction implicit procedure indicate that a direct method using alternating diagonal ordering can be competitive for as many as 3,000 equations. A FORTRAN computer code is included that is compatible with the two-dimensional ground-water flow model developed by the U.S. Geological Survey. The performance characteristics, computer storage requirements, and input data requirements for the direct solution algorithm are also included.