MT3DMS (Modular 3-Dimensional Transport model - Multi-Species structure)

MT3DMS is a three-dimensional multi-species solute transport model for solving advection, dispersion, and chemical reactions of contaminants in saturated groundwater flow systems.

three-dimensionalmulti-speciessolute transportadvectiondispersionchemical reactionscontaminantsgroundwater



Initial contribute: 2021-01-17


University of Alabama
University of Alabama
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Quoted fromZheng, Chunmiao, and P. Patrick Wang. "MT3DMS: a modular three-dimensional multispecies transport model for simulation of advection, dispersion, and chemical reactions of contaminants in groundwater systems; documentation and user’s guide." (1999). 

      The new mass transport model documented in this manual is referred to asMT3DMS, where MT3D stands for the Modular 3-Dimensional Transportmodel, and MS denotes the Multi-Species structure for accommodating add-onreaction packages.  MT3DMS has a comprehensive set of options andcapabilities for simulating advection, dispersion/diffusion, and chemicalreactions of contaminants in groundwater flow systems under generalhydrogeologic conditions.  This section summarizes the key features ofMT3DMS. 

      MT3DMS is unique in that it includes three major classes of transport solu-tion techniques (the standard finite-difference method, the particle-tracking-basedEulerian-Lagrangian methods, and the higher-order finite-volume TVD method)in a single code.  Since no single numerical technique has been effective for all transport conditions, the combination of these solution techniques, each havingits own strengths and limitations, is believed to offer the best approach forsolving the most wide-ranging transport problems with efficiency and accuracy. 

      In addition to the explicit formulation of the original MT3D code, MT3DMSincludes an implicit formulation that is solved with an efficient and versatilesolver.  The iterative solver is based on generalized conjugate gradient (GCG)methods with three preconditioning options and the Lanczos/ORTHOMINacceleration scheme for nonsymmetrical matrices.  If the GCG solver is selected,dispersion, sink/source, and reaction terms are solved implicitly without anystability constraints.  For the advection term, the user has the option to select anyof the solution schemes available, including the standard finite-differencemethod, the particle-tracking-based Eulerian-Lagrangian methods, and the third-order TVD method.  The finite-difference method can be fully implicit withoutany stability constraint to limit transport step sizes, but the particle-tracking-based Eulerian-Lagrangian methods and the third-order TVD method still havetime-step constraints associated with particle tracking and TVD methodology.  Ifthe GCG solver is not selected, the explicit formulation is automatically used inMT3DMS with the usual stability constraints.  The explicit formulation isefficient for solving advection-dominated problems in which the transport stepsizes are restricted by accuracy considerations.  It is also useful when the implicitsolver requires a large number of iterations to converge or when the computersystem does not have enough memory to use the implicit solver.

      MT3DMS is implemented with an optional, dual-domain formulation formodeling mass transport.  With this formulation, the porous medium is regardedas consisting of two distinct domains, a mobile domain where transport ispredominately by advection and an immobile domain where transport ispredominately by molecular diffusion.  Instead of a single “effective” porosityfor each model cell, two porosities, one for the mobile domain and the other forthe immobile domain, are used to characterize the porous medium.  Theexchange between the mobile and immobile domains is specified by a masstransfer coefficient.  The dual-domain advective-diffusive model may be moreappropriate for modeling transport in fractured media or extremely heterog-eneous porous media than the single-porosity advective-dispersive model,provided the porosities and mass transfer coefficients can be properlycharacterized. 

      MT3DMS retains the same modular structure of the original MT3D codewhich is similar to that implemented in the U.S. Geological Survey modularthree-dimensional finite-difference groundwater flow model, MODFLOW(McDonald and Harbaugh 1988; Harbaugh and McDonald 1996).  The modularstructure of the transport model makes it possible to simulate advection,dispersion/diffusion, source/sink mixing, and chemical reactions separatelywithout reserving computer memory space for unused options; furthermore, newpackages involving other transport processes and reactions can be added to themodel readily without having to modify the existing code. 

      As in the original MT3D code, MT3DMS is developed for use with anyblock-centered finite-difference flow model such as MODFLOW and is based on the assumption that changes in the concentration field will not affect the flowfield significantly.  After a flow model is developed and calibrated, the informa-tion needed by the transport model can be saved in disk files which are thenretrieved by the transport model.  Since most potential users of a transport modelare likely to have been familiar with one or more flow models, MT3DMS pro-vides an opportunity to simulate contaminant transport without having to learn anew flow model or modify an existing flow model to fit the transport model.  Inaddition, separate flow simulation and calibration outside the transport model canresult in substantial savings in computer memory.  The model structure alsosaves execution time when many transport runs are required while the flow solu-tion remains the same.  Although this report only describes the use of MT3DMSin conjunction with MODFLOW, MT3DMS can be linked to any other block-centered finite-difference flow model in a simple and straightforward fashion. 

      MT3DMS can be used to simulate changes in concentrations of misciblecontaminants in groundwater considering advection, dispersion, diffusion, andsome basic chemical reactions, with various types of boundary conditions andexternal sources or sinks.  The chemical reactions included in the model areequilibrium-controlled or rate-limited linear or nonlinear sorption and first-orderirreversible or reversible kinetic reactions.  It should be noted that the basicchemical reaction package included in MT3DMS is intended for single-speciessystems.  An add-on reaction package such as RT3D (Clement 1997) orSEAM3D (Widdowson and Waddill 1997) must be used to model more sophis-ticated multispecies reactions.  MT3DMS can accommodate very general spatialdiscretization schemes and transport boundary conditions, including:  (a) con-fined, unconfined, or variably confined/unconfined aquifer layers; (b) inclinedmodel layers and variable cell thickness within the same layer; (c) specifiedconcentration or mass flux boundaries; and (d) the solute transport effects ofexternal hydraulic sources and sinks such as wells, drains, rivers, areal recharge,and evapotranspiration. 


Chunmiao Zheng, Pu Patrick Wang (2021). MT3DMS (Modular 3-Dimensional Transport model - Multi-Species structure), Model Item, OpenGMS,


Initial contribute : 2021-01-17



University of Alabama
University of Alabama
Is authorship not correct? Feed back

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