NAME
mocdense - A two-constituent solute transport model for ground water
having variable density
ABSTRACT
This model simulates solute transport in flowing ground water. It
is applicable to two-dimensional, cross-sectional problems involving
ground water with constant or variable density. The model computes
changes in concentration over time caused by the processes of
advective transport, hydrodynamic dispersion, mixing or dilution
from fluid sources. The concentrations of two independent solutes
can be modeled simultaneously. Temperature is assumed to be
constant, but fluid density and viscosity are assumed to be a linear
function of the first specified solute. If a second solute is
specified, it is assumed to be of a trace amount such that it does
not affect the fluid density or viscosity. The aquifer may be
heterogeneous and anisotropic. The model has been used mostly in
studies of either saltwater intrusion or dense contaminant plumes.
The model was documented by Sanford and Konikow (1985). For a
documentation of the numerical method used, see the report by
Konikow and Bredehoeft (1978).
METHOD
The model couples the ground-water flow equation with the solute-
transport equation. The digital computer program uses an iterative
strongly-implicit procedure to solve a finite-difference
approximation to the ground-water flow equation. The model uses the
method of characteristics to solve the solute-transport equation.
This incorporates a particle-tracking procedure to represent
advective transport and a two-step explicit finite-difference
procedure to solve equations that describe the effects of
hydrodynamic dispersion and fluid sources. This explicit procedure
has several stability criteria associated with it, but the
consequent time-step limitations are automatically determined by the
program.
HISTORY
Version 3.2 1995/01 - Most current version. This version includes
several upgrades and fixes to minor bugs from earlier versions.
Version 1.0 1985 - Original version released.
DATA REQUIREMENTS
Initial conditions, boundary conditions, aquifer properties at every
node, grid descriptors, and linear equation parameters that relate
fluid density and viscosity to solute concentration.
OUTPUT OPTIONS
See documentation.
SYSTEM REQUIREMENTS
MOCDENSE is written in Fortran 77 with the following extensions:
use of integer*2 declarations and use of the $ format descriptor.
Generally, the program is easily installed on most computer systems.
The code has been used on UNIX-based computers and DOS-based 386 or
greater computers having a math coprocessor and 4 mb of memory.
DOCUMENTATION
Sanford, W.E., and Konikow, L.F., 1985, A two-constituent solute
transport model for ground water having variable density: U.S.
Geological Survey Water-Resources Investigations Report 85-4279,
89 p.
REFERENCES
Konikow, L.F., and Bredehoeft, J.D., 1978, Computer model of two-
dimensional solute transport and dispersion in ground water: U.S.
Geological Survey Techniques of Water-Resources Investigations,
book 7, chap. C2, 90 p.
TRAINING
One-day introduction during the class Modeling Transport of Ground-
Water Solutes (GW2080TC), offered annually at the USGS National
Training Center.
CONTACTS
Operation and Distribution:
U.S. Geological Survey
Hydrologic Analysis Software Support Program
437 National Center
Reston, VA 20192
h2osoft@usgs.gov
Official versions of U.S. Geological Survey water-resources analysis
software are available for electronic retrieval via the World Wide
Web (WWW) at:
http://water.usgs.gov/software/
and via anonymous File Transfer Protocol (FTP) from:
water.usgs.gov (path: /pub/software).
The WWW page and anonymous FTP directory from which the MOCDENSE
software can be retrieved are, respectively:
http://water.usgs.gov/software/mocdense.html
--and--
/pub/software/ground_water/mocdense
See http://water.usgs.gov/software/ordering_documentation.html for
information on ordering printed copies of USGS publications.
SEE ALSO
moc(1) - Two-dimensional method-of-characteristics ground-water
flow and transport model
modflow(1) - Modular three-dimensional ground-water flow
model
Modflowp(1) - Parameter-estimation version of the modular model
sutra(1) - Saturated and (or) unsaturated, constant or
variable-density fluid flow, and solute or energy
transport (2-dimensional finite-element code)
vs2di(1) - A graphical software package for simulating fluid flow
and solute or energy transport in variably saturated
porous media