SUMMARY OF MT3D-USGS


NOTE: Any use of trade, product, or firm names is for descriptive purposes only
      and does not imply endorsement by the U.S. Government.


ABSTRACT 

     MT3D-USGS, a U.S. Geological Survey updated release of the groundwater  
solute transport code MT3DMS, includes new transport modeling capabilities 
to accommodate flow terms calculated by MODFLOW packages that were previously 
unsupported by MT3DMS and to provide greater flexibility in the simulation 
of solute transport and reactive solute transport. Unsaturated-zone transport 
and transport within streams and lakes, including solute exchange with 
connected groundwater, are among the new capabilities included in the MT3D-USGS 
code. MT3D-USGS also includes the capability to route a solute through dry 
cells that may occur in the Newton-Raphson formulation of MODFLOW (that is,
MODFLOW-NWT). New chemical reaction package options include the ability to 
simulate interspecies reactions and parent-daughter chain reactions. A new
pump-and-treat recirculation package enables the simulation of dynamic 
recirculation with or without treatment for combinations of wells that are 
represented in the flow model, mimicking the above-ground treatment of 
extracted water.  A reformulation of the treatment of transient mass storage
improves conservation of mass and yields solutions for better agreement with 
analytical benchmarks. Several additional features of MT3D-USGS are (1) the 
separate specification of the partitioning coefficient (Kd) within mobile and 
immobile domains; (2) the capability to assign prescribed concentrations to the 
top-most active layer; (3) the change in mass storage owing to the change in 
water volume now appears as its own budget item in the global mass balance 
summary; (4) the ability to ignore cross-dispersion terms; (5) the definition
of Hydrocarbon Spill-Source Package (HSS) mass loading zones using regular and 
irregular polygons, in addition to the currently supported circular zones; and 
(6) the ability to specify an absolute minimum thickness rather than the 
default percent minimum thickness in dry-cell circumstances. 
     Benchmark problems that implement the new features and packages test the 
accuracy of new code through comparison to analytical benchmarks, as well as to 
solutions from other published codes. The input file structure for MT3D-USGS 
adheres to MT3DMS conventions for backward compatibility: the new capabilities 
and packages described herein are readily invoked by adding three-letter 
package name acronyms to the name file or by setting input flags as needed. 
Memory is managed in MT3D-USGS using FORTRAN modules in order to simplify
code development and expansion.
     MT3D-USGS is described in the documentation report by Bedekar and others 
(2016).


HISTORY

      MT3D-USGS Version 1.0.1 02/28/2019 - Bug-fix release
      MT3D-USGS Version 1.0.0 09/30/2016 - Initial release. 

        
SYSTEM REQUIREMENTS

     MT3D-USGS is written in Fortran 90 programming language. The code has 
     been used on personal computers running various forms of the Microsoft
     Windows operating system.


FUNTIONALITY

     MT3D-USGS can be run from the command line by first typing the name of 
     the executive file followed by the MT3D-USGS simulation's name file (e.g.,
     'c:\MT3D-USGS.exe modelname_mt.nam'). MT3D-USGS is backward compatible and
     therefore supports the following MT3DMS Packages (Zheng and Wang, 1999):
    
     MT3DMS packages supported in MT3D-USGS:
         ADV -- Advection Package
         BTN -- Basic Package
         DSP -- Dispersion Package
         FMI -- Flow-Model Interface
         GCG -- Generalized Conjugate Gradient Solver Package
         HSS -- Hydrocarbon Spill Source Package
         RCT -- Reactions Package
         SSM -- Source-Sink Mixing 
         TOB -- Time Observation Package
         
     New MT3D-USGS packages not available in MT3DMS:
         CTS -- Contaminant Treatment System Package
         LKT -- Lake Transport Package        
         SFT -- Streamflow Transport Package
         UZT –- Unsaturated-Zone Transport Package
     

DOCUMENTATION

Bedekar, V., Morway, E.D., Langevin, C.D., and Tonkin, M., 2016, MT3D-USGS 
version 1: A U.S. Geological Survey release of MT3DMS updated with new and 
expanded transport capabilities for use with MODFLOW: U.S. Geological Survey 
Techniques and Methods 6-A53, 69 p., Available online at 
http://dx.doi.org/10.3133/tm6A53


REFERENCE

Zheng, C., and Wang, P., 1999, 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: 
Contract Report SERDP-99-1: Vicksburg, Miss., U. S. Army Engineer Research
and Development Center.  Available online at: http://hydro.geo.ua.edu/mt3d/ 


CONTACT

    Vivek Bedekar
    S.S. Papadopulos & Assoc.
    7944 Wisconsin Ave.
    Bethesda, MD 20814
    (301) 718-8900

    Eric Morway
    U.S. Geological Survey
    2730 N. Deer Run Rd. 
    Carson City, NV 89701
    (775) 887-7668