A numerical procedure for the solution of the steady state variable density groundwater flow equation

A numerical code is developed for the solution of the three-dimensional steady state groundwater flow equation in which groundwater density varies with spatial position and is treated as known spatially dependent parameter. The integrated finite difference grid elements of the numerical code are rectangular when viewed along the vertical direction, but their top and bottom surfaces parallel or are coincident with the interfaces between the geologic strata within the solution region. Conditions that are sufficient for the accuracy of the code are derived. Approximate solutions for pressure head, as determined from the code, are compared for accuracy with several exact analytic test solutions.