Water Resources Applications Software

Geochemical || Ground Water || Surface Water || Water Quality || General

Summary of MOC

       moc - Two-dimensional method-of-characteristics ground-water flow
             and transport model

       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).

       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

       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

       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).

       See documentation.
       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.

       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.

       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.

       Modeling Transport of Ground-Water Solutes (GW2080TC), offered
       annually at the USGS National Training Center.

       Operation and Distribution:
          U.S. Geological Survey
          Hydrologic Analysis Software Support Program
          437 National Center
          Reston, VA 20192

       Official versions of U.S. Geological Survey water-resources analysis
       software are available for electronic retrieval via the World Wide
       Web (WWW) at:


       and via anonymous File Transfer Protocol (FTP) from:

         (path: /pub/software).

       The WWW page and anonymous FTP directory from which the MOC software
       can be retrieved are, respectively:

       See for
       information on ordering printed copies of USGS publications.

       modflow(1) - Modular three-dimensional ground-water flow
       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

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