Versions of MODFLOW

What Version of MODFLOW Is the Most Suitable for Your Project?

Visual MODFLOW supports the most widely used versions of MODFLOW developed by the USGS and others, and we strive to include the most widely used packages. The following is a summary of each version, and some remarks as to the inclusion in the VMOD Flex interface.

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Chronology of USGS MODFLOW Releases

For more than 30 years, the USGS MODFLOW family of codes has been used to address challenging groundwater modeling problems around the world. Originally released in 1984, the first version of MODFLOW implemented generalized solutions to the groundwater flow for saturated conditions and simple boundary conditions based on an open-source FORTRAN code with a modular framework.  Over the years, the USGS and collaborating partners have added significantly to the capabilities of MODFLOW to support groundwater resource evaluations by the USGS and its partners, to the benefit of the wider scientific community. The following infographic provides a chronology of the various versions of MODFLOW and related codes that are supported in Visual MODFLOW Flex:

The six core versions of MODFLOW are presented above the timeline, while specialized variants and partner software are presented below the timeline. Each of these codes (or engines) are described below.

What Version of MODFLOW Is the Most Suitable for Your Project?

Visual MODFLOW supports the most widely used versions of MODFLOW developed by the USGS and others, and we strive to include the most widely used packages. The descriptions below provide a summary of each version and some useful links.

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Groundwater Flow Engines

MODFLOW-2000, MODFLOW-2005

MODFLOW-2000 and MODFLOW-2005 are based on the finite difference formulation and utilize structured rectilinear grids. These versions are likely still the most widely used, even though the USGS has already retired MODFLOW-2000 and is in the process of winding down its usage/support for MODFLOW-2005.

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MODFLOW-NWT

First released in 2011, this version of MODFLOW overcomes the long-standing issue with dry cells (which occurs when the hydraulic head drops below the cell bottom). If you are encountering dry cells in your model, then it is recommended that you switch to MODFLOW-NWT; the main differences in this version of MODFLOW are the property package (uses Upstream Weighting, UPW) and the solver (NWT).

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MODFLOW-LGR

This version of MODFLOW supports the ability to add locally refined “child” grids inside of a regional-scale “parent” numerical grid. This is an efficient grid refinement approach and is ideal for refinement around good fields or localized areas of interest.

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MODFLOW-USG

First released in 2013, MODFLOW-USG is an advanced version of MODFLOW that uses the more advanced control volume finite difference approach and supports unstructured grids. MODFLOW-USG is supported only in the conceptual modeling workflow of the VMOD Flex interface, and Voronoi or Quadtree grids are used.

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MODFLOW-6

As the newest core version, MODFLOW-6 combines the major features of the most-popular MODFLOW variants including:

  • Unstructured Grids (MODFLOW-USG)
  • Newton-Raphson formulation (MODLFOW-NWT),
  • Connected/Nested Grids (MODFLOW-LGR),
  • Dual-Domain Solute Transport (MT3D-MS)
  • Density-dependent flow and solute transport (SEAWAT) and some new features unique to MODFLOW-6:
  • as well as some new/unique features:
  • full 3D anisotropy tensor support (via the XT3D formulation),
  • multiple stress package instances, and mover/exchange packages

Note that not all these features are supported in the latest version of Visual MODFLOW Flex; however, we plan to add support based on user demand. If there is a feature of MODFLOW-6 that is not yet available that you’d like to see added in a future version of Visual MODFLOW Flex, please let us know at support@waterloohydrogeologic.com to help us prioritize your needs.

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MODFLOW-SURFACT

MODFLOW-SURFACT is a powerful three-dimensional finite-difference flow and transport program containing many advancements and improvements over the standard public-domain versions of MODFLOW. With more robust solution methods and enhanced simulation capabilities for handling complex saturated/unsaturated subsurface flow and transport processes, MODFLOW-SURFACT is specifically designed to address the many limitations and shortcomings of the standard MODFLOW codes. Use MODFLOW-SURFACT when simulating:

  • multiple water tables, or perched water table systems
  • steep water table gradients crossing multiple model layers
  • over-pumped wells screened across multiple model layers
  • surface water infiltration through the vadose zone to the water table
  • large water table fluctuations causing desaturation/resaturation (drying/wetting) of grid cells
  • soil vapor flow through the unsaturated zone

This enhanced MODFLOW run engine is ideally suited for complex models with variably saturated conditions! MODFLOW-SURFACT requires a separate 3rd party license to be purchased. VMOD Flex works with SURFACT v.4 and supports flow and transport models. A limited demo license is included with Visual MODFLOW Flex.

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Groundwater Transport and Coupled Engines

MT3D-MS

MT3D-MS is a three-dimensional (3D) finite-difference multi-species groundwater transport model developed by Chunmiao Zheng (1990) at S.S. Papadopulos and works with outputs from core versions of MODFLOW, particularly MODFLOW-2000, MODFLOW-2005, and certain variants. The code solves the advection-dispersion equation using a variety of available techniques and includes processes, such as various sorption models, mass transfer to/from an immobile domain, and simple irreversible reactions.

 

RT3D

RT3D is an extended reactive transport model based on MT3D-MS and developed by the Pacific Northwest National Laboratory (PNNL). It incorporates several common reaction pathways that are commonly encountered in projects involving bioremediation and/or natural attenuation.

 

SEAWAT

The SEAWAT numeric engine introduces the capability of simulating three-dimensional, variable-density, groundwater flow coupled with heat transport. The concept of SEAWAT is to combine a flow code (MODFLOW-2000) with a solute-transport code (MT3DMS) to form a single program that solves the coupled flow and solute-transport equations with solute-concentration dependent variable density and viscosity relationships. It formulates the flow equation using mass conservation instead of volume conservation like MODFLOW-2000. SEAWAT-2000 was the original release; SEAWAT v.4 enhanced the capabilities with additional support for heat transport.  SEAWAT derives the governing equation for variable-density groundwater flow in terms of the equivalent freshwater head.

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MODFLOW-SURFACT

See above. 

MODFLOW-6

See above.

 

Related Versions and Utilities

MODPATH and MOD-PATH3DU

MODPATH and MOD-PATH3DU are utilities used to evaluate the path of user defined-particles through the (steady-state or transient) output flow field from a MODFLOW simulation forwards or backward in time. Particle pathlines are typically based on purely advective flow, although MOD-PATH3DU may also simulate dispersion by using a random walk method. MODPATH is developed by the USGS; while MOD-PATH3DU is developed by S.S. Papadopulos & Associates (SSPA) in partnership with the Department of Civil Engineering at the University of Waterloo. While MOD-PATH3DU is supported in Visual MODFLOW Flex and is free to use, it is based on proprietary code and must be obtained via a registered download from the SSPA website (http://mp3du.sspa.com/)

 

ZoneBudget

ZoneBudget is a utility developed by the USGS to evaluate sub-regional flow budgets in a MODFLOW model by subdividing the model domain into zones and tracking the inward, outward, and net flows between a given zone itself and its internal storage, its internal boundary conditions, and its neighboring zones.

 

PEST

PEST is an application (and a suite of associated utilities) developed by John Doherty (Watermark Numerical Computing) that is used to automate parameter estimation to facilitate model calibration (history matching) and to evaluate model uncertainty using a variety of techniques. Overall, PEST is a framework to interact with the input and output files of a model (or a series of models) and it uses this framework to run the model(s) iteratively to adjust input parameter values to minimize a user-defined set of goals (such as minimizing the difference between a given set of observations and corresponding simulated outputs subject a set of user-defined constraints).

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Additional Engines

Additional versions of MODFLOW and related codes that have functionality similar to engines supported in Visual MODFLOW Flex or that are less commonly used and have not been implemented in Visual MODFLOW Flex include:

  • GWM: Groundwater Management Process, a response-matrix solver for groundwater management objective functions subject to constraints (Link)
  • VSF: Variably Saturated Flow Process, a version of MODFLOW with an implementation of the 3D Richard’s Equation (Link)
  • PHT3D: Geochemical reactions and transport, a coupled version of MT3D-MS and PHREEQC-2 (Link)
  • CFP: Conduit Flow Process: an extended version of MOFLOW-2005 that simulates laminar or turbulent flow in a 1D linear network and/or groundwater flow through alternative preferential domain(s) (Link)
  • SWR: Surface Water Routing, an extended version of MODFLOW-NWT that supports surface water routing through 1D and 2D surface water features (Link)
  • OWHM: One-Water Hydrologic Flow Model, a coupled groundwater-surface water that combines several variants of MODFLOW (LGR, FMP,SWR, CFP, NWT) (Link)
  • GSFLOW: integrated groundwater-surface water modeling (MODFLOW-2005+PRMS) (Link)