MODFLOWT

Contaminant Transport with MODFLOW (1996)

TPS 59-1 Standard or TPS 59-2 Professional. Contact igwmc@mines.edu for more info

MODFLOWT is a new version of MODFLOW that includes modules for simulating three-dimensional transport. The new model, authored by Glenn Duffield of HydroSOLVE, solves equations for advective-dispersive transport with adsorption and first-order decay using a fully-implicit finite-difference technique developed for the public domain code FTWORK by GeoTrans, Inc (see elsewhere in this catalog). The model uses central differencing and upstream weighting approximation options for advective terms, and a fully implicit (backward-in-time) or Crank-Nicolson (central-in-time) approximation options for the time derivative. The model supports optional expansion of cross products in the dispersion tensor.

MODFLOWT is fully-compatible with previous MODFLOW versions. MODFLOWT implements transport simulation through the addition of new packages for Basic Transport (BST), Block-Centered Transport (BCT), and an Orthomin solver. The new program provides full support of existing MODFLOW modules including the transport aspects of these modules (i.e., concentration of river water, distributed recharge, well recharge, and the General Head Boundary package; scale factors for concentration for ET; and calculation of mass fluxes for these and other MODFLOW packages). MODFLOWT includes the SSOR, SIP, and PCG solvers for flow. For transport, in addition to the Orthomin solver, an enhanced version of the SSOR solver is available. The code includes automatic time stepping with adaptive controls for transport. It also has restart options for both flow and transport through importing initial head and concentration distribution generated in previous MODFLOWT runs. A new Observation Well Package allows recording of heads and concentrations at observation nodes. Output includes a detailed mass budget history.

Documentation of the proprietary MODFLOWT program consists of a user guide and a benchmarking/verification report. The latter includes extensive comparison with analytical solutions and with the MT3D transport code. MODFLOW and STR1 documentation is optional. The packages also includes the GWPOST utility to reformat MODFLOWT into formats suitable for contouring and graphing. MODFLOWT is supported by the Groundwater Vistas modeling system (see elsewhere in this catalog).

MODFLOWT comes in two versions: 1) STANDARD - executable for Intel 80386/486/Pentium based computers running under MS-DOS/PC-DOS/DR-DOS; 2) PROFESSIONAL - executable and source code for porting to non-PC environments.

SYSTEM REQUIREMENTS

Intel 80386/80486 based computer, 4 Mb RAM, DOS 3.0 or higher, math coprocessor.

Developer: Glenn Duffield, HYDROSOLVE.