Widespread acceptance of MT3D is a bonus! Besides being easy to use, accurate, and fast, MT3D and its precursors have been widely accepted by regulators and the groundwater consulting and research communities and have been successfully applied at thousands of sites around the world.

Introduction to MT3D
New Features in MT3D99
MT3D Pre- and Post-Processing Packages


MT3D is a comprehensive three-dimensional numerical model for simulating solute transport in complex hydrogeologic settings. MT3D has a modular design that permits simulation of transport processes independently or jointly. MT3D is capable of modeling advection in complex steady-state and transient flow fields, anisotropic dispersion, first-order decay and production reactions, and linear and nonlinear sorption. The new MT3D99 can also handle bioplume-type reactions, monad reactions, and daughter products. This enables MT3D99 to do multi-species reactions and simulate or assess natural attenuation within a contaminant plume. MT3D99 is linked with the USGS groundwater flow simulator, MODFLOW, and is designed specifically to handle advectively-dominated transport problems without the need to construct refined models specifically for solute transport.


The MT3D99 upgrade incorporates significant new enhancements to improve performance and increase the functionality of the MT3DMS and MT3D96 codes.

MT3D99 Enhancements Include:

  • Implicit Solver

The implicit finite difference solver in the advection and sink/source terms enables the user to solve a wide array of problems while using less computer time.

  • New Solution Technique

The new higher-order finite-volume TVD (total-variation-diminishing) solution method has been shown to be effective where other solution techniques fail. This includes better mass balance calculations and minimal numerical dispersion.

  • Dual Porosity Model

MT3D99 provides a better estimate of mass transfer in fractured media or extremely heterogeneous media. The porous medium is divided into two domains: a mobile domain where advective transport dominates and an immobile domain where diffusion dominates.

  • Nonequilibrium Sorption and Monod Kinetics

The nonequilibrium sorption model enables the user to examine the role of sorption in solute transport and remediation processes without the restrictive local-equilibrium assumption. In addition to the first-order kinetics, MT3D99 supports zero-order and mixed-order Monod kinetics reactions.

  • Reaction Packages

MT3D99 can handle Bioplume-type reactions, monad reactions, and daughter products. This enables MT3D99 to do multi-species reactions and simulate or assess natural attenuation within a contaminant plume. These enhancements preclude the need for RT3D.

  • Automatic Restart Option

MT3D99 supports a new automatic restart option to greatly facilitate the continuation run from a previous simulation.

  • Improved Mass Balance

MT3D99 includes cell-by-cell mass budget calculations.

  • Multi-Species Reactions

MT3D99 can simulate basic chemical reactions including: equilibrium controlled, rate-limited linear or non-linear sorption, and first-order irreversible or reversible kinetic reactions.

Why choose MT3D99 as your 3D Solute Transport Simulator?

  • Full Compatibility with MODFLOW. MT3D99 is designed to work directly with the industry-standard groundwater flow code MODFLOW and MODFLOW96.
  • Three Major Classes of Transport Solution Techniques. MT3D99 is unique in that it contains three types of solution classes in one code. These include the Standard Finite Difference Method, the Particle Tracking Eulerian-Lagrangian Methods, and the Higher-Order Finite-Volume TVD Method.
  • More Precise Calibrations. The new dual porosity option for modeling mass transport may enable better calibrations. The assignment of mobile and immobile domains may enable better calibrations in areas where the effective porosity model has failed in the past.


MT3D is supported by many graphical pre- and post-processors including PROCESSING MODFLOW for Windows (PMWIN), Visual MODFLOW , GMS - Groundwater Modeling System, and Groundwater Vistas. MT3D99 also includes several useful and flexible postprocessing programs: PostMT3DfModflow for creating 2D or 3D data files for any graphic and visualization software package including Surfer and TecPlot; HCOMP for computing residuals and summary statistics between observed and mode-calculated heads and concentrations; and FBUDGET for calculating detailed groundwater flow and solute mass budgets in any user-specified subregion of the model grid.

MT3D99 accepts input files prepared for all previous versions of MT3D. MT3D has been successfully applied at thousands of sites, and is widely accepted by regulators and the groundwater consulting and research communities. MT3D99 incorporates many enhancements requested by users that make it more accurate, efficient, and flexible.

The MT3D99 package includes a comprehensive manual, source and executable codes, and postprocessing utility programs. MT3D99 also includes a version of MODFLOW with the most significant new packages. The executable codes in MT3D99 are compiled using dynamic memory allocation and can take advantage of all available extended memory.

MT3D99 Requirements: PC 486/Pentium with 4 MB RAM.