NAME
moc - Two-dimensional method-of-characteristics ground-water flow
and transport model
ABSTRACT
This model simulates solute transport in flowing ground water. It
is applicable to one- or two-dimensional problems involving steady-
state or transient flow. The model computes changes in
concentration over time caused by the processes of advective
transport, hydrodynamic dispersion, mixing or dilution from fluid
sources, and certain types of chemical reactions (first-order
irreversible-rate reaction or equilibrium-controlled sorption-
desorption and ion exchange). Gradients of fluid density,
viscosity, and temperature are assumed not to affect the velocity
distribution. However, the aquifer may be heterogeneous and
anisotropic. It is one of the most used models for solute-transport
problems. Complete documentation of the current version of this
model requires both the report by Konikow and Bredehoeft (1978) and
the report by Goode and Konikow (1989).
METHOD
The model couples the ground-water flow equation with the solute-
transport equation. The digital computer program uses an iterative
alternating-direction implicit procedure to solve a finite-
difference approximation to the ground-water flow equation
(alternative modules to solve the flow equation using SIP or using a
direct solver based on D4 ordering are also available). 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 3.2.2 1996/01/22 - In separate velocity output file, change
in code to write Vy assuming y-axis increases upward
Version 3.2 1995/03/21 - Minor bug fixes and improvements
Version 3.1 1994/07/06 - WRDAPP tape 2.1 update release with minor
bug fixes
DATA REQUIREMENTS
Initial conditions, boundary conditions, aquifer properties at every
node, and grid descriptors. PLEASE NOTE: there is a typographical
error on page 16 of the 1994 documentation (WRIR 94-4115) regarding
the input format for the NODEID matrix. The correct format is
(20I1) instead of (40I1).
OUTPUT OPTIONS
See documentation.
SYSTEM REQUIREMENTS
MOC is written in Fortran 77 with the following extensions: use of
variable names longer than 6 characters 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
Konikow, L.F., Granato, G.E., and Hornberger, G.Z., 1994, User's
guide to revised method-of-characteristics solute-transport model
(MOC--Version 3.1): U.S. Geological Survey Water-Resources
Investigations Report 94-4115, 63 p.
REFERENCES
Goode, D.J., and Konikow, L.F., 1989, Modification of a method-of-
characteristics solute-transport model to incorporate decay and
equilibrium-controlled sorption or ion exchange: U.S. Geological
Survey Water-Resources Investigations Report 89-4030, 65 p.
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
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 MOC software
can be retrieved are, respectively:
http://water.usgs.gov/software/moc.html
--and--
/pub/software/ground_water/moc
See http://water.usgs.gov/software/ordering_documentation.html for
information on ordering printed copies of USGS publications.
SEE ALSO
modflow(1) - Modular three-dimensional ground-water flow
model
Modflowp(1) - Parameter-estimation version of the modular model
premoc - A preprocessor for the two-dimensional method of
characteristics (MOC) solute-transport model
(version 4.1.2)
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