MODFE is a modular 2D finite element model for simulation of steady-state or transient areal, cross-sectional, and axi-symmetric ground-water flow. Geometric and hydrologic aquifer characteristics in two spatial dimensions are represented by triangular finite elements and linear basis functions; 1D finite elements and linear basis functions represent time. Finite element matrix equations are solved by the direct symmetric-Doolittle method or by the iterative modified, incomplete Cholesky, conjugate gradient method. Physical processes that can be represented by the model include: 1) confined flow; unconfined flow (using the Dupuit approximation), a combination of both, and conversion in time between confined and unconfined conditions; 2) leakage through either rigid or elastic confining beds; 3) specified recharge or discharge at points along lines and over areas; 4) flow across specified flow, specified head or head dependent boundaries; 5) decrease of aquifer thickness to zero under extreme water table decline and increase of aquifer thickness from zero as the water table rises; and 6) head dependent fluxes from springs, or drainage wells; leakage across riverbeds or confining beds combined with aquifer dewatering; and evapotranspiration. Boundary conditions and stresses may change on a stress-period basis, time-step basis, or both. The model allows for zoned input of heterogeneous, anisotropic hydraulic properties and boundary conditions. The program produces tabular file output for the heads.

Includes manual, source code, executable images and example data sets.

SYSTEM REQUIREMENTS

Intel 80386 with 4 Mb RAM and math coprocessor, DOS 3.1 or higher, 3 Mb free disk space runs in a DOS window.

Authors: R.L. Cooley and L.J. Torak.