Versions of MODFLOW
What Version of MODFLOW Is the Most Suitable for Your Project?
Visual MODFLOW supports the most widely used versions of USGS MODFLOW and MODFLOW-SURFACT (HGL), and we strive to include the most widely used packages. The following is a brief summary of each version, and some remarks as to the inclusion in the VMOD Flex or VMOD Classic interface.
MODFLOW-2000 and MODFLOW-2005 are based on the finite difference formulation, and utilize structured rectilinear grids. These versions are likely the most widely used. All process such as MODPATH, ZoneBudget, PEST, MT3DMS, RT3D, and PHT3D are compatible with MODFLOW-2000 and MODFLOW-2005. Both versions are supported in VMOD Flex.
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) with a solute-transport code (MT3DMS) to form a single program that solves the coupled flow and solute-transport equations. It formulates the flow equation using mass conservative instead of volume conservative like MODFLOW-2000. SEAWAT-2000 was the original release; SEAWAT v.4 enhanced the capabilities with the additional support for heat transport. SEAWAT derives the governing equation for variable-density groundwater flow in terms of equivalent freshwater head. Equivalent freshwater head is a very important terminology in variable-density groundwater flow.
SEAWAT is currently only supported in VMOD Classic; add-on programs such as MODPATH, ZoneBudget, and PEST are supported in VMOD Classic.
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 is the property package (uses Upstream Weighting, UPW) and the solver (NWT). Otherwise, all boundary conditions and standard packages are supported. All accessory programs such as MODPATH, ZoneBudget, PEST, MT3DMS, RT3D, and PHT3D are compatible with MODFLOW-NWT. MODFLOW-NWT is supported in VMOD Flex, along with support for ZoneBudget, MT3DMS, and MODPATH; (PEST, RT3D, and PHT3D are not supported.
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 well fields or localized areas of interest.
MODFLOW-LGR (v.1) is supported only in the VMOD Flex interface. There is no support for PEST, Transport (MT3DMS, RT3D, SEAWAT), or MODPATH (particle tracking). MODFLOW-LGR is only available when you create a new model (there is no option to load an existing MODFLOW (structured grid) model, and convert it to MODFLOW-LGR)
More details on MODFLOW-LGR concepts can be found below:
Released in 2013, MODFLOW-USG is a new version of MODFLOW that supports UnStructured Grids. MODFLOW-USG is supported only in the VMOD Flex interface, and Voronoi grids are used. Only basic flow simulations are supported. There is no support for PEST, Contaminant Transport, MODPATH, or ZoneBudget in VMOD Flex. MODFLOW-USG will only work when you create a new model (there is no option to load an existing MODFLOW (structured grid) model, and convert it to MODFLOW-USG)
More details on MODFLOW-USG concepts can be found below:
- MODFLOW-USG Webinars on YouTube
- Visual MODFLOW Flex – MODFLOW-USG Tutorial
- Comparison of MODFLOW-USG grid geometries
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 short-comings 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 ideally suited for complex models with variably saturated conditions!
MODFLOW-SURFACT requires a separate 3rd party license to be purchased. VMOD Classic works with SURFACT v.3 and v.4 and supports flow only. VMOD Flex works with SURFACT v.4 and supports flow and transport models.
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.
(Note: Timeline figures are not to scale)
USGS MODFLOW Releases: 1980-2005
USGS MODFLOW Releases: 2005-present
|LGR: Local Grid Refinement|
GWM: Groundwater Management Process
VSF: Variably Saturated Flow
CFP: Conduit Flow Process
GSFLOW: Groundwater – Surface Water Flow
CDSS: Colorado Decision Support Systems
SWR: Surface Water Routing
USG: UnStructured Grids
OWHM: One-Water Hydrologic Flow Model
Thanks to Chris Langevin, USGS, for reviewing content of the MODFLOW Chronology figures.