Visual MODFLOW Flex: Supported Packages and Engines
MODFLOW Engines and Utilities
With Visual MODFLOW Flex you have a comprehensive set of tools necessary for addressing water quality, groundwater supply, and source water protection initiatives, including:
MODFLOW-2000, 2005, NWT | Worldwide standard for simulating groundwater flow. |
MODFLOW-6 | The updated core version of MODFLOW – supports structured and unstructured grids, flow and transport modeling – Learn More |
MODFLOW-USG | Control volume Finite Difference version of MODFLOW that uses unstructured grids – Learn more |
MODFLOW-LGR | Shared-node local grid refinement (LGR) for regional-local scale simulations. |
MODFLOW-SURFACT* | Enhanced simulations of complex saturated/unsaturated subsurface flow and transport processes. |
MODPATH | Standard utility for forward and reverse particle tracking. |
MOD-PATH3DU** | Advanced utility for forward and reverse particle tracking. |
Zone Budget | Standard package for sub-regional water budget calculations. |
* MODFLOW-SURFACT is a proprietary version of MODFLOW, developed by HydroGeoLogic, Inc. (HGL). A demo version of MODFLOW-SURFACT is included with Visual MODFLOW Flex. The full version is available as an add-on.
** distributed separately and available for download by registering at the MOD-PATH3DU website.
MODFLOW Packages:
Groundwater Flow Packages
- BAS – Basic Package
- DIS – Discretization Package for structured grids
- DISU – Discretization Package for unstructured grids (MODFLOW-USG)
- DISV – Discretization by Vertices Package for unstructured grids (MODFLOW-6)
- BCF – Block Centered Flow Package
- LPF – Layer Property Flow Package
- HUF – Hydrogeologic Unit Flow Package
- UPW – Upstream Weighting Flow Package
- NPF – Node Property Flow Package
- STO – Storage Package
- IC – Initial Conditions Package
Boundary Condition Packages*:
- RIV – River package
- CHD – Constant-Head boundary package
- DRN – Drain package
- WEL – Well package
- LAK – Lake Package
- EVT – Evapotranspiration package
- SFR – Streamflow-Routing Package
- RCH – Recharge package
- FHB – Flow and Head boundary package
- MNW1/2 – Multinode Well Package
- HFB – Horizontal Flow Barrier Package
- UZF – Unsaturated Zone Flow Package
- RSF** – Recharge Seepage Face package
- TMP** – Time-Varying Material Properties package
* Not all packages are available with every groundwater flow engine, please refer to the Visual MODFLOW Flex documentation.
** Package available in MODFLOW-SURFACT only. MODFLOW-SURFACT is a proprietary version of MODFLOW, developed by HydroGeoLogic, Inc. (HGL). A demo version of MODFLOW-SURFACT is included with Visual MODFLOW Flex. The full version is available as an add-on.
Solver Packages*:
- GMG – Geometric Multigrid Solver
- NWT – Newton-Raphson Solver
- PCG – Pre-conditioned Conjugate Gradient Solver
- SAMG – Algebraic Multi-Grid Solver
- SIP – Strongly Implicit Solver
- WHS – Waterloo Hydrogeologic Solver (Bi-Conjugate Gradient Stabilized [Bi-CGSTAB] acceleration)
- SMS – Sparse Matrix solver for MODFLOW-USG (Learn More)
- IMS – Iterative Matrix Solution for MODFLOW-6 (Learn More)
* Not all solvers are available with every edition of Visual MODFLOW Flex or with every groundwater flow engine, please refer to the Visual MODFLOW Flex documentation for more details.
Transport Engines:
- MT3DMS –Standard simulation of multi-species solute transport including advection, dispersion, sorption, and chemical reactions.
- MODFLOW-6 – The updated core version of MODFLOW includes integrated transport modeling
- MODFLOW-SURFACT* – Enhanced simulations of complex saturated/unsaturated subsurface flow and transport processes.
- SEAWAT –Variable-density groundwater flow coupled with multi-species solute and heat transport.
- RT3D – Advanced and specialized multi-species reactive solute transport simulations.
* MODFLOW-SURFACT is a proprietary version of MODFLOW, developed by HydroGeoLogic, Inc. (HGL). A demo version of MODFLOW-SURFACT is included with Visual MODFLOW Flex. The full version is available as an add-on.
Parameter Estimation and Sensitivity Analysis:
PEST – Automated parameter estimation, calibration and sensitivity analysis. With Visual MODFLOW Flex, defining PEST inputs and interpreting results are made easy with an intuitive, easy-to-use interface that guides you through the PEST process from start to finish. Includes support for pilot points, various regularization options and advanced kriging.
Grid Types
Structured Finite Difference Grids: model domain is divided into layers, rows, and columns that extend through the entire model domain. Horizontal discretization allows variable widths of columns and variable lengths of rows.
There are three types of vertical discretization supported in Visual MODFLOW Flex:
Deformed Grid:
Model layers conform to and represent hydrostratigraphic layers.

Uniform Grid:
Model layers are flat with uniform thickness and hydrostratigraphic layer properties are assigned based on the location of the model cells.
Semi-Uniform Grid:
Top and bottom model layers conform to surfaces, intermediary layers are

Unstructured Control Volume Finite Difference Grids
QuadTree Grid (Q-grid):
Refinements are achieved by recursively bisecting cells in a rectilinear grid in areas of interest.
Voronoi Grid (V-Grid)
Refinements are achieved using Voronoi tessellation in areas of interest.

Supported File Types
Import spatial and attribute data from a wide variety of data types including:
- Spatial/Vector Data:
- Points: tabulated data (.XLS, .XLSX, .TXT, .CSV, .MDB), shapefiles (.SHP), CAD exchange files (.DXF), particle files (.TRP)
- Polylines: shapefiles (.SHP), CAD exchange files (.DXF)
- Polygons: shapefiles (.SHP), CAD exchange files (.DXF)
- Raster Data:
- 3D Surfaces: Surfer Grid Files (.GRD), ESRI ASCII Grid Files (.ASC)
- 3D Gridded Data: Model Outputs (.HDS, .UCN), Tecplot (.DAT)
- Images and Basemaps: Images (.BMP, .TIF, .JPG), CAD Exchange Files (.DXF)
- Time Schedules: Tabulated data (.XLS, .XLSX, .TXT, .CSV, .MDB)
- Cross-Sections: Hydro GeoAnalyst (HGA) Cross Sections (.3XS)
- Vertical and Non-vertical Wells: Tabulated Data (.XLSX, .CSV)