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Simulating contaminant attenuation, double-porosity exchange, and water age in aquifers using MOC3D

Fact Sheet 086-99

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Abstract

MOC3D is a general-purpose computer model developed by the U.S. Geological Survey (USGS) for simulation of three-dimensional solute transport in ground water (Konikow and others, 1996). The model is an update to the widely used USGS two-dimensional solute-transport model (MOC) and is implemented as an optional “package” for the ground-water flow model MODFLOW (Harbaugh and McDonald, 1996). Directly coupling the time-tested MOC transport algorithms with the widely used MODFLOW program makes MOC3D a powerful tool for simulation of solute transport in ground water in many hydrogeologic settings. The model simulates transport processes that include:

  • Advection - Transport of dissolved solutes at the same rate as the average ground-water flow velocity.
  • Diffusion - Spreading of solute from areas of high concentration to areas of low concentration, caused by “random” molecular motion
  • Dispersion - Diffusion-like spreading of solute that is caused primarily by spatial variability in aquifer properties, which results in spatial variability in transport velocity.
  • Retardation - Reduction in the apparent solute velocity, compared to the ground-water velocity, caused by linear equilibrium sorption on aquifer materials.
  • Decay - Disappearance of solute caused by reactions such as radioactive decay or biodegradation that are proportional to concentration.
  • Growth - Creation (or disappearance) of solute mass caused by reactions that proceed independent of the solute concentration, such as some cases of biodegradation
  • Double-porosity exchange - rate-limited exchange of solute mass between mobile and immobile zones; for example, between fractures and the rock matrix.

Suggested Citation

Goode, D.J., 1999, Simulating contaminant attenuation, double-porosity exchange, and water age in aquifers using MOC3D: U.S. Geological Survey Fact Sheet 1999–0086, 4 p., https://pubs.er.usgs.gov/publication/fs08699.

ISSN: 2327-6932 (online)

Table of Contents

  • MOC3D - A General-Purpose Solute-Transport Model
  • Attenuation of Contaminants in Aquifers Having Spatially VAriable Geochemistry
  • Double-Porosity Exchange: Matrix Diffusion in Fractured Rock
  • Effects of Dispersion on Ground-Water Age
  • Model Compatibility and Availability
  • References Cited

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Simulating contaminant attenuation, double-porosity exchange, and water age in aquifers using MOC3D
Series title:
Fact Sheet
Series number:
086-99
Year Published:
1999
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Pennsylvania Water Science Center
Description:
4 p.