ABSTRACT
The finite-difference flow model described herein is based on the finite-difference flow model developed by T. A Prickett and C. G. Lonnquist. The derivation is based on the instantaneous flow balance at the end of a discrete time increment around discretized finite aquifer or aquifer layer volumes centered at nodes and extending the full aquifer or aquifer layer thickness. The edges of the finite-difference grid represent barrier boundaries located one half of the grid spacing beyond border nodes. An effective infinite aquifer or aquifer layer may be simulated by making the number of columns and rows and grid spacings sufficiently large so that the heads at interior nodes of interest are not affected by the finite-difference grid boundary. The grid spacing is kept small in comparison to the simulation area to insure high precision head calculations. Smallest grid spacings are specified where the head gradient varies significantly such as in the vicinity of production or injection wells, rivers, mines, and drains.
