GGSD Program Details for MOC

MOC

Category	Contaminant transport (2D FD)
Publisher	US Geological Survey
Platform	DOS, Mac, UNIX, DG, SGI, Sun
Status	Public domain
Description	MOC is a 2D model for the simulation of non-conservative solute transport in saturated ground-water systems. It computes changes in the spatial concentration distribution over time caused by convective transport, hydrodynamic dispersion, mixing or dilution from recharge and chemical reactions. The chemical reactions include first-order irreversible rate reaction (such as radioactive decay), reversible equilibrium-controlled sorption with linear, Freundlich, or Langmuir isotherms, and reversible equilibrium-controlled ion exchange for monovalent or divalent ions. The model assumes that fluid density variations, viscosity changes, and temperature gradients do not affect the velocity distribution. Allows modelling of heterogeneous and anisotropic, confined aquifers. Solves the ground-water flow equation and the non-conservative solute-transport equation in a step-wise (uncoupled) fashion. Uses the method of characteristics to solve the solute transport equation with a particle tracking procedure to represent convective transport and a two-step explicit procedure to solve the finite-difference equation that describes the effects of hydrodynamic dispersion, fluid sources and sinks, and divergence of velocity. Uses a rectangular, block-centred finite-difference grid for flux and transport calculations. The grid size for flow and transport equations allows up to 100 rows and 100 columns. The program allows spatially varying diffuse recharge or discharge, saturated thickness, transmissivity, boundary conditions, initial heads and initial concentrations, and an unlimited number of injection or withdrawal wells. Up to five nodes can be designated as observation points for which a summary table of head and concentration versus time is printed at the end of the calculations. An interactive pre-processor, PREMOC, allows data entry and editing. The program produces tabular output which can be processed in a commercial contouring package. Includes the pre-processor, PREMOC, and two versions of the MOC program, one that can handle a 40 by 40 grid and a version that can handle a 100 by 100 grid. A batch file capability is also included for conducting multiple runs during calibration and sensitivity analysis. Links to MOCGRAF to contour output and MOCTIME to generate time history plots.
Cost	Free on WWW
Data formats supported	None stated
Supplier in United States of America	International Ground Water Modeling Center
Supplier in United States of America	Scientific Software Group
Supplier in United States of America	US Geological Survey