Visual MODFLOW Flex Readme

Version 10.0 | Build (April 2024)

Defects Addressed:

  • The layer number for observations in the calibration dashboard was off by 1 unstructured grids
  • Comparing heads from a transient run to a steady state run (and vice versa) only produced one results for one time step
  • Missing layer parameter data resource (*.dat.res) files for unstructured MODFLOW-6 models in a PEST run for layers other than 1
  • PEST does not improve calibration for flux observations when MODFLOW-6 is the selected engine
  • Unhandled Exception visualizing RCH or EVT terms in budget plugin
  • Isosurface is not immediately updated in 3D view upon changing Color settings


Version 10.0 | Build (March 2024)


PEST Workflow:

Visual MODFLOW Flex includes significant upgrades to the PEST workflow:

  • Workflow Steps: The PEST workflow includes a number of new and improved workflow steps:
    • Define Observations: add flux observations and improved usability for assigning observation groups, observations, and weights
    • Define Property Parameters: add recharge (RCH), evapotranspiration (EVT), and unsaturated zone flow (UZF) property parameters to the PEST run
    • Define Kriging Variograms: an optional new setting that allows PEST utilities to automatically calculate the kriging variograms based on the density of pilot points
    • Select PEST Variant: you can select which variant of PEST to use (PEST v17.5, PEST_HP),
    • PEST Control settings: define/edit settings for the PEST run including for the Objective Function, Parameter Updates, Iterations, Marquardt Lamda, Singular Value Decomposition, etc.
  • Parameter Estimation: Stop and Restart PEST Runs
  • Support for PEST_HP: significantly speed up PEST runs by using PEST_HP, a parallelized version of PEST that can make use of multiple cores on your machine
  • Support for MODFLOW-6: include structured finite difference or unstructured MODFLOW-6  flow models in a PEST workflow
  • Pilot Point Interpolation: The scripts in a PEST run that link parameter updates in PEST to pilot points include a number of improvements:
    • Pilot point interpolation makes use of the PLPROC utility for improved performance and clarity of the script files
  • Optional automated calculation of the kriging variogram parameters based on the density of pilot points
    Improved Validation: Visual MODFLOW Flex includes additional checks in the PEST workflow to reduce input errors
  • Observation Weights: automatically calculate observation weights so that observation groups contribute equally to the initial objective function with and without normalizing observations using the target residual

Color Handling

Visual MODFLOW Flex includes the following improvements for visualization:

  • Color Ramps: objects with distributed values such as surfaces, model properties, boundary conditions, and model outputs can be rendered using predefined or custom color ramps:
    • define a list of custom, linearly distributed, logarithmically distributed, or custom values and associated colors
    • select from a list of predefined, custom, or imported color ramps
    • you can include hard breaks/color stops in a ramp to render an abrupt change in colors when values cross a specified threshold (e.g. positive/negative or above/below a regulatory limit)
  • Manage Color Ramps:
    • Visual MODFLOW Flex includes over a dozen predefined color ramps or you can create your own custom color ramp
    • You can import color ramps using the color map (.clr) file format supported in other applications such as QGIS, ArcPro, and Surfer
    • The project palette variables include all color fill settings including colors and values
  • Project Palette: the project palette includes all value and color settings, so you have more fine control over rendering

Boundary Conditions and Properties

  • MAW and MWT Package Support: Support for the multi-aquifer well (MAW) and multi-aquifer well transport (MWT) packages in MODFLOW-6 models.
    • Create or import MAW/MWT wells
    • Dynamically switch between supported well models (WEL/MNW1/MNW2/MAW)
    • Import and edit well information including head loss, well skin, and pump constraint parameters supported in the MAW package
  • Conceptual Wells: pumping wells in the unstructured grid workflow are grid-independent, conceptual, and support the WEL or MAW well model.
  • Flux Observations: Support for boundary condition flux observations for unstructured grid models (MODFLOW-6 and MODFLOW-USG)
  • Assign Properties: the assign properties in the unstructured grid workflow includes additional tools for setting property zones and values similar to the tools available in the workflow for structured finite difference grid models
  • Layer Properties: the translation step in the unstructured grid workflow includes layer type settings for MODFLOW-USG and MODFLOW-6 modelsThe unstructured grid workflow now uses the more familiar and intuitive conceptual well controls that uses coordinates and well screen information instead of cell indices

Performance, Usability, and Other Enhancements

  • Performance Enhancements:
    • Assigning time steps to models with many stress periods
    • Model translation for MODFLOW-6 models with many stress periods
    • Converting a conceptual model to an unstructured Q-grid model with many cells
    • Applying/saving changes to model properties for an unstructured grid model with many cells
  • The following features can be exported from Visual MODFLOW Flex:
    • model outputs including heads, concentrations, and drawdowns as contours for unstructured grid models (MODFLOW-6 and MODFLOW-USG)
    • boundary conditions as points or polygons for unstructured grids
    • calibration dashboard charts as images
  • SAMG solver:
    • Updated versions of the SAMG solver for the MODFLOW-USG and MODFLOW-6 engines
    • Available in the Pro (serial-SAMG) and Premium (multi-core-SAMG)
    • New Add-on available for Visual MODFLOW Flex Premium Edition that includes a more advanced edition called SAMG+ that also handles models with transport and CLN
  • Other Enhancements:
    • The view will be centered on the mouse pointer when using the mouse wheel to zoom in/out in 2D views
    • The View/Edit Grid step for structured finite difference grid numerical workflows includes a toolbar with buttons to interact with the view
    • The Translation Step in numerical workflows includes a general setting to translate models using external arrays/files to facilitate working with PEST
    • The output times table in the Output Control settings page for MT3D-MS, RT3D, or SEAWAT models will expand if you can paste more output times than there are rows
    • Consolidate boundary conditions in a model into a single boundary condition
    • Intermediary layer elevations automatically update after changing the min and max elevations or the number of layers when defining the grid in a numerical workflow
    • Some informational messages that appear repeatedly have settings to automatically suppress them


  • The preferred homogeneous Tikhonov regularization method was removed from the PEST workflow – it is not supported for MODFLOW-6 and is no longer recommended by the author of PEST

Defects Addressed:

  • Conceptual to Numerical conversion did not honor the “Assign to appropriate layer” flag for constant head cells in structured and unstructured grids
  • SFR2 Translation omitted stream reaches/cells if the entire segment was contained in a single model cell
  • Various issues with windows, forms, buttons, and other components when using high resolution monitors:
    • Create new Object window
    • Run Tabs are clipped
    • Labels overlap workflow step buttons
  • Model runs will fail with an obscure warning if the combined engine call and model path exceed 256 characters
  • Grid Preview at Create Grid Step does not update when the grid extents are changed or data objects are added to the view
  • Dispersion and diffusion were disabled by default in the DSP6 package settings for MODFLOW-6 models
  • Certain regional settings prevented the creation of conceptual boundary conditions
  • Property Zone Conversion incorrect in Qgrids with subrefined layers
  • In some circumstances added custom contour intervals were not rendered
  • Unhandled exception while assigning Boundary Conditions by Polyline
  • In some circumstances, “object reference is not set to the instance of the object” error occurs while converting the conceptual model to a numerical model and also while translating it
  • PEST parameter zones get unchecked in some circumstances when returning to the Define Property Zones step
  • MODFLOW-6 RCH/EVT translation includes incorrect cell references when using the AsArrays translation setting
  • In some circumstances, Visual MODFLOW Flex is unable to read model outputs/attributes after running the model successfully
  • Constant- head package translator. Translation failed. Exception: The given key was not present in the dictionary
  • Certain regional settings caused a “Common Time Horizon Error” when translating well pumping schedules for some dates
  • “Edit grid” and “Edit layers” button does not work from View Finite Difference Grid
  • Model run failure for MODFLOW-6 runs when a pumping well screen spans a pinchout layer
  • MODFLOW-USG translation did not include all wells in certain circumstances
  • “Error in loading boundary polygon” message shown repeatedly when loading a project, when showing the error once would be sufficient
  • For some regional settings the project start date was not saved and reset to today
  • New grids created in a Conceptual Model with edited horizons did not reflect the updated structural zones
  • Error exporting particle pathlines in some circumstances
  • In some circumstances a new numerical workflow with optimized parameters was not correctly created following a successful PEST run
  • In some circumstances grids that were both rotated and refined shifted coordinates after revisiting the Create Grid step in the numeric workflow
  • MODFLOW-USG translation did not respect the Active flag for some boundary conditions (DRN, RIV, GHB)
  • Sensitivity PEST control file not generated when using tied parameters
  • Drawdowns are not always calculated/displayed correctly when the flow engine is MODFLOW-6
  • MODFLOW-6 RCH translation does not respect user selection of active/inactive cells over boundary condition editor
  • Error when activating the current view
  • Transport run failure if injection well has multiple screens that span the same cell
  • Zone Budget (time series, in/out, etc.) of a model had to be retranslated and rerun if it was not run during the current session of Flex
  • Concentration time series calibration tables and charts are not created properly for certain transient models in MODFLOW-6
  • Model start date does not always display correctly after NM conversion if regional date settings are DD/MM/YYYY
  • MF-2005 translation of WEL package does not always include a space between values leading to run failures
  • SFR2 illegal geometry warning gives incorrect stream reaches
  • SFR2 ISTCB1 variable not written correctly for viewing/processing budget terms


Version 9.0 | Build 9.0.412.44834 (March 2023)


MODFLOW-6 Groundwater Flow and Transport:

Visual MODFLOW Flex now supports MODFLOW-6, the newest core version of the groundwater modeling code developed by the USGS. MODFLOW-6 is based on a redesigned framework that supports 3D groundwater flow, solute transport, and various processes with an all new and more legible input file structure for both structured and unstructured grids. The following MODFLOW-6 flow packages are supported in Visual MODFLOW Flex:

  • Simulation Packages:
    • NAM – Simulation Name File
    • TDIS – Time Discretization
    • IMS – Iterative Model Solution
  • Groundwater Flow Model (GWF): Simulate saturated groundwater flow using structured finite difference grids or unstructured control volume finite difference grids (Voronoi or Quadtree).
    • NAM – Groundwater Flow Model Name File
    • DIS – Discretization Package
    • DISV – Discretization by Vertices Package
    • IC – Initial Conditions (Heads)
    • OC – Output Control Package
    • NPF – Node Property Flow Package
    • STO – Storage Package
    • CHD* – Time Varying Constant Head Package
    • WEL* – Well Package
    • DRN* – Drain Package
    • RIV* – River Package
    • GHB* – General-Head Boundary Package
    • RCH – Recharge Package
    • EVT – Evapotranspiration Package
  • Solute Transport Model (GWT): Simulate groundwater solute transport using structured finite difference grids or unstructured control volume finite difference grids (Voronoi or Quadtree), including a variety of sorption, reaction, and immobile domain models.
    • NAM – Groundwater Transport Model Name File
    • DIS – Discretization Package
    • DISV – Discretization by Vertices Package
    • IC – Initial Conditions (Concentrations)
    • OC – Output Control Package
    • ADV – Advection Package
    • DSP – Dispersion Package
    • MST – Mobile Storage Transfer Package
    • IST – Immobile Storage Transfer Package (up to three immobile domains)
    • SSM – Source Sink Mixing Package
    • CNC* – Time Varying Constant Concentration Package
    • SRC* – Mass Source Loading Package
  • Multiple Instance Packages: MODFLOW-6 allows you to include multiple instances of certain packages (marked with * above) in a simulation and track budgets separately for each package.
  • Support for ZoneBudget-6: Evaluate sub-regional flows for your groundwater flow models using MODFLOW-6

Engines and Packages

  • Assign Grid (In)active cell zones using data objects: You can use point, polyline, and polygon data objects to set the active/inactive flag for grid cells in the Finite Difference grid workflows
  • Import MNW1 Wells from Classic Projects: Well information using the MNW1 well model in Classic Projects can be imported into Visual MODFLOW Flex
  • Minimum thickness for Unstructured Grids: You can specify a minimum cell thickness below which unstructured grid cells will be removed from the grid so that you have more control on grid design around pinchout areas.
  • MODPATH with SEAWAT: You can run a MODPATH particle tracking simulation based on a SEAWAT flow (and transport) run.
  • Compare: Compare results for heads, drawdowns, or concentrations between two model runs using the same unstructured grid.

Performance, Usability, and Other Enhancements

  • The unstructured grid workflow now uses the more familiar and intuitive conceptual well controls that uses coordinates and well screen information instead of cell indices
  • You can specify default Total and Effective Porosity values at the Define Modeling Objectives step
  • You can add particles for a particle track simulation based on Well objects in the Model Explorer as well as in the Data Explorer
  • Improved speed and performance saving and loading projects
  • You can specify a custom default project save location to save time when creating new projects
  • New Keyboard Shortcuts:
    • Press CTRL+T at the Translate Step to translate a model
    • Press CTRL+R at the Run Step to run a model

Defects Addressed:

  • Unhandled exception when replacing layer elevations with a surface containing holes (NoData) values
  • Contour lines not shown for intervals with high precision/very small increments in some cases
  • Intermittent “Failed to apply settings” error when visualizing recharge or evapotranspiration rates in some views
  • Some view style settings do not honor the “Show in Cutaway” option
  • In some cases, boundary condition schedules are not translated correctly in the SSM package
  • Various windows issues with high resolution monitors:
    • Expression Builder window
    • Create Surface/Interpolation Settings window
    • Editing Conceptual Boundary Conditions
    • Define Property Zones step in the Conceptual Workflow
  • In some cases, pathlines would not be exported as a shapefile
  • Error editing numerical boundary condition in some cases
  • Unhandled “index was out of range” error while copying property zones to another model property
  • Error using the fill buttons on the Active checkbox field in the Edit Boundary Condition window
  • Can’t save lake gauge data when there are no streams in the SFR workflow
  • Errors realizing lakes using SFR workflow without streams
  • In some cases, importing concentrations via a UCN file resets inactive cell flag to active in the associated grid where the water table is below grid layer 1
  • Error creating boundary condition using a surface as a data source in some cases
  • Error importing well schedule using absolute date with certain formats
  • Editing the recharge database did not always edit the recharge boundary condition
  • Transient Model with Steady-State stress period does not translate correctly
  • Unable to run MODPATH due to null reference error
  • Calibration Dashboard did not correctly report units in the summary statistics based on the selection
  • Issue with defining boundary conditions for certain shapefiles
  • Issue running PEST in some situations when parameter zones do not extend through all model layers
  • Failed to move to target step error of Surface Water Workflow in some conceptual models
  • Errors creating variograms in the PEST workflow in some cases
  • Particle tracking pathlines do not display correct units/values due to unit conversion errors for some combinations of project units
  • Unable to translate MNW2 package under some circumstances
  • When draping basemap images onto a surface using the operations, a only limited number of points were sampled

Version 8.0 | Build (January 2023)

Defects Addressed:

  • In some cases, importing a UCN file resets active/inactive grid cell status if the water table is below layer 1
  • Null Reference Exception when assigning elevation values for a conceptual Drain Boundary Condition using a surface in some cases
  • Resolved some issues with running MODPATH
  • Issue with define boundary condition
  • High resolution screen settings hid part of the Create Conceptual Boundary Condition window
  • Issues running PEST in some cases with pilot points in zones spanning multiple layers
  • Failed to move to target step errors when using the Surface Water Workflow in the conceptual modeling workflow
  • Error creating variograms for PEST under certain conditions
  • Flex becomes non-responsive when exporting horizons of larger models due to performance issues


Version 8.0 | Build (October 2022)

Defects Addressed:

  • Incorrect schedule/concentrations translated to SSM file for some well boundary conditions in projects with time units other than days.
  • Problem Visualizing Recharge Rates in 3D views in some models
  • “StartIndex cannot be less than zero” error while running models with the Dashboard still open
  • JSON reader error when editing well boundary condition
  • Export pathlines to shapefiles option does not create the shapefiles
  • Unhandled exception “Index was out of range” while copying property zones to another property
  • RCH/EVT boundary conditions may get corrupted with “Object reference not set to an instance of an object” errors
  • ‘True’ (or ‘False’) is not a valid number or expression error when setting the active flag for boundary conditions
  • Can’t save lake gauge data when no streams are present in the surface water model
  • X-Rate budget output terms may not be read correctly from MODFLOW-USG run results for some models using Voronoi grids with certain structural complexities
  • Errors realizing Lakes from the surface water workflow without streams
  • Issues with Constant Head Boundary Condition set to “inactive” in model results
  • In some cases, grid cells set to inactive when importing a UCN file with dry cells


Version 8.0 | Build (March 2022)



  • Boundary Condition Flow: net volumetric flow exchange between groundwater and a specified boundary condition
  • ZoneBudget Zone Flow: net volumetric flow exchange of groundwater in/out of a specified zone, between a specified zone and another zone or a specified boundary condition type
  • Stream (SFR): stage, depth, outflow, head difference between stream midpoint and associated groundwater cell centroid, flow diverted (diversion segments only), groundwater head, streambed seepage through the unsaturated zone
  • Lakes (LAK): stage, volume, inflow, outflow

Calibration and Run Result Visualization:

  • Calibration Dashboard: Model observations and associated model results can be displayed in the new model results dashboard which includes dynamic tabulation and charting of results:
    • Tabulated results: observations and corresponding simulated results are presented in a tabular format with dynamic filtering. Tabulated observations include observation metadata, including time, location, observation group/type, model layer, and conductivity zone, so that you can quickly display all the data or limit the view to what is relevant.
    • Charts: simultaneously display one or more charts including: simulated vs observed values charts to evaluate model calibration/history matching and time series charts to display and evaluate transient result
    • Text Outputs: all observations and associated simulated results are output as tab separated variable text files for use in both Visual MODFLOW Flex and in external applications.
  • Flooded Cells: Display cells with simulated heads above the top of the model as a flood depth map or as a solid color to facilitate model calibration and interpretation:
  • Easily switch the location of subviews in a Flex Viewers so that you can customize the layout.
  • Save and reload standalone 2D and 3D viewers
  • Proportionally sized calibration residuals can be viewed for unstructured grid model runs

Packages and Model Runs:

  • Single Engine Runs: run a secondary model such as transport, particle track, or zone budget simulation without having to rerun your flow model.
  • Update Solvers: update your flow model solvers without having to retranslate your whole model
  • Copy Property Zones: copy/paste zones from one material property zone type to another so that you can more easily have consistent material zones across property types such as conductivity, storage, and transport parameters
  • Default SMS Settings: the default settings for the SMS solver package in MODFLOW-USG have been updated based on recommendations by the author of MODFLOW-USG
  • Gage Package: gage package is supported in models using the surface water network workflows for streams (SFR) and lakes (LAK).

Surface Water Workflow:

  • Conceptual Workflow: Build surface water stream and lake networks in a conceptual model and convert it to numerical models
  • Clone Workflow: surface water workflows are copied into applicable runs when editing a grid or cloning a model run

Data Handling:

  • Data Operations: data objects use the expression builder, facilitating greater control and flexibility when adjusting data object elevations for surfaces, points, polylines, and polygons.
  • Expression Builder functions: added a function called ifgaps() to handle expressions with non-overlapping surfaces – now you can combine surfaces with different extents/scales such as regional and site surfaces using a single expression.
  • Horizons: are now treated the same as other surfaces: they can be shown in 2D views with control over display settings
  • Cell Inspector Feedback: Typing a cell ID in the cell inspector provides (optional) feedback on where the specified cell is located in the active view
  • Export more data objects:
    • Grids: shapefile,
    • Output Comparisons: shapefile, contours, and surfaces
    • Horizons: surfaces
    • Water Table: surfaces

Performance, Usability, and Other Enhancements:

  • Performance enhancements:
    • Loading and editing model properties and boundary conditions in larger models
    • Conceptual model conversion to numerical models using unstructured Q-Grids
    • Using the Cell inspector
    • Model Translation of Boundary Conditions
  • Backup your project and related files as a zip file from the Main Menu to archive your project or easily share it with colleagues.
  • Generate all grid types from the Model Domain context menu of conceptual models
  • Define particles around screens of non-vertical wells in the 3D plane perpendicular to the path of the well screen

Defects Addressed:

  • Changing numeric values in color ramp settings has no effect
  • Improper validation when importing a model that uses the BCF package having inactive cells with 0 thickness causes model runs to fail.
  • Pilot Point values not correctly assigned using property values from the model leading to issues with preferred-value Tikhonov regularization
  • PEST implementation incorrectly assumed pilot points were present in all layers and was corrected to only assign pilot points to cells/layers in their respective zone.
  • ZoneBudget fails to run if Conceptual Model name has leading or trailing spaces
  • Flow model translation fails if the SFR workflow schedule/data is empty. Flex will now skip SFR translation in this case.
  • Project files grow after each save
  • SFR2 Feature layer order and symbology does not persist after closing and reopening the project
  • WEL package disables MNW2 translation in some cases
  • Error assigning MNW wells to numerical model in certain cases
  • Flex fails to create child grids in one-layer grids
  • PEST workflow does not create Variograms when some layers do not contain a zone.
  • Quality and aspect ratio of exported images from 2D views was incorrect
  • DRT package not included in run using Advanced translation settings
  • Layer View is corrupted in some cases when viewing T=1 in View Maps step
  • Surface Water Workflows are not included in cloned runs present in the original run
  • Insufficient validation at translation may lead to LGR models that fail because dry cells propagate to the interface between parent and child grids.
  • MODFLOW-SURFACT BCF package translation formatting is incorrect for layers with negative elevations
  • Transport run window only reports up to 9999 time steps. The max number of reported time steps for a transport run is now 100,000,000.
  • Cannot extract a subgrid if the project has been run previously, but not in the current session
  • Importing well objects having measured depths resulting in negative elevations fails
  • During transport engine translation, .BTN file does not always honor the ‘Simulation time length’ value entered in MT3DMS translation settings
  • When a single 2D sub view is active at the view maps step, the view toolbar buttons may be hidden
  • Grid color cannot be changed in Flex 2D subviews
  • Export null values in dry cells/inactive cells does not respect user selection
  • Error while trying to import UCN files with unknown units
  • Error opening constant concentration in standalone viewers
  • Error trying to access color settings in certain numerical workflows
  • SFR dataset2 is missing cells during translation of model with certain topological configurations
  • Property zone data entry section of Define Property Zone value is missing or clipped when high-resolution font-scaling/screen settings are used
  • Compare heads functionality did not allow comparison of 3D gridded data with transient schedules
  • Problems reading time units for .HDS and other 3D gridded data files from certain engines

Version 7.0 | Build 7.0.7187.36895 (January 2021)


Surface Water Modeling (SFR2):

  • New Surface Water workflow to develop and define connected networks of stream segments, diversions, and lakes
  • GIS editing capabilities for digitizing the surface water network including add, remove, edit, delete, snap, split, flip
  • Surface water network attribute editing dialog for streams and lakes
  • Support for the Streamflow-Routing (SFR2) package in Finite Difference Models
  • Translated SFR2 package including lake connections and 1-D vertical unsaturated flow beneath perched streams

Well and Multi-Node Well (MNW1/2):

  • Support for multi-node well (MNW1/2/I) packages in Finite Difference Models:
    • Dynamically switch between supported well models (WEL/MWN1/MNW2)
    • Import and edit well information including head loss, well skin, and pump constraint parameter supported in MNW1/2 packages
    • Support for non-vertical wells (also known as deviated or horizontal) wells
  • Define conceptual Wells by drawing or by assigning wellhead points
  • Multi-select editing of well parameters and schedules

Model Import:

  • When importing a MODFLOW model, you can now define an offset and rotation angle for the grid to set the model in world coordinates.
  • Import MODFLOW-NWT model and supported packages
  • When importing files MODFLOW files, invalid values that will cause issues during a simulation (such as negative conductivities) are replaced with project default values.

Model Calibration:

  • Import and/or set target residuals for Head/Concentration Observations
  • Display spatial distribution of residuals relative to target residuals by layer or observation group at the View Maps workflow step
  • The number of observations is included as a statistic below Calculated versus Observed calibration charts

Model Runs:

  • Flow and Transport model run results are graphically displayed in real time including the global residual error and the max head/concentration change, as supplied by the active solver package settings.
  • Modified MODFLOW-USG to report solver progress in real time to the display console including global residual error

Usability and Other Enhancements:

  • Visualize Flow Budgets/Fluxes for MODFLOW-USG simulations
  • When visualizing multi-attribute plugins (such as Flux, Velocity) to visualize you can select the active attribute to be shown in the view and in the status bar
  • Edit individual top/bottom of individual cells via the mouse or via script when editing grid layers
  • Graphically select refinement rows/columns using the mouse when editing the grid in plan view
  • A link to the model files is available at the Parameter Estimation step in PEST workflow
  • Translation log is copyable to the Windows Clipboard
  • NWT translation settings include option for the IPHDRY setting

Defects Addressed:

  • Error during Visual MODFLOW Classic project import in projects with zero thickness cells when loading conductivity values
  • The selected background color was not included in exported images of 2D views
  • Property Zones listed in alphabetical order rather numerical order in the Edit Properties window
  • Style settings of polygon were not retained between sessions
  • Error “MS Office is not installed…” shows up during import occurs when certain versions of Office are installed
  • The internal handling of time units was refactored to handle schedules and values with varying time units and scales with improved precision, accuracy, and consistency to within one second regardless of schedule duration and time units selected
  • Unable to enter negative model coordinates when defining a grid
  • In some cases, when reloading a project, the “Failed to move to target step” error appears
  • Voronoi grid not generated correctly when input features nearly coincide with the model boundary
  • Some dialog and workflow step buttons were missing/cutoff when using lower resolution display settings
  • Unable to edit/assign boundary conditions if the duration of the schedule too large
  • Background color was not saved between sessions in some views
  • The option to use shapefile attribute data to define conceptual property zones not functional
  • In some cases, errors prevented the export of calibration data
  • Unable to convert a conceptual model to USG when certain shapefiles are used to define the model domain
  • The option to use shapefile attribute data to define conceptual property zones not functional
  • Errors preventing MODPATH runs in 32-Bit Versions of Flex
  • Extract Subgrid failed if any model run under the original grid was previously deleted
  • In some cases, concentration observations were not correctly displayed at the View Charts step
  • Edit grid script failed when using shift model origin commands on variably refined grids
  • Head and concentration observations were not displayed due to translation errors in some SEAWAT models
  • Concentrations were not available in the Project Color Palette
  • In rare cases, the pumping schedule was not correctly translated in the WEL package
  • In some cases, the project could enter a state where it could no longer be saved due to the presence of larger shapefiles
  • In some cases, the RT3D simulation time was not correctly translated into the BTN package
  • Rerunning a model reset/removed the outputs selected in the cell inspector
  • Immobile concentrations were not correctly read on successful dual domain runs of MT3DMS or SEAWAT
  • PEST workflows did not correctly support overlapping zones in multi-layer models
  • In some cases, observations could not be read with a Wall BC was present in the simulation
  • In some cases, importing a 3D-gridded data object deleted certain property values in related numerical model(s)
  • Pilot Point values not correctly assigned in distributed models, particularly in Tikhonov Regularization
  • In some cases, very thin model cells in a Q-grid cause errors when converting conceptual model to a MODFLOW-USG workflow

Version 6.1 | Build 6.1.7088 (July 2019)


Usability and Other Enhancements:

  • Expression Builder includes round and significant digit functions
  • You can Assign/Edit Model Properties and Boundary Conditions using an input surface, horizon, or water table object in the Expression Builder
  • You can zoom to an object in the Model Explorer in a 2D viewer using the context menu
  • The SAMG solver is available with MODFLOW-USG
  • You can specify ground surface or heads from a previous model run instead of instead of using the initial head property values at the translation step for MODFLOW-USG runs
  • Visual MODFLOW Flex warns you and allows you to back up a project before irreversibly upgrading projects created in previous versions

Defects Addressed:

  • Adding a data object such as a bitmap that is non-transparent during the grid creation process will overlay it on top of the grid rendering it invisible.
  • Row/Column views for rotated grids are projected on NS/EW planes rather than on rotated model co-ordinate axes
  • In some cases, surfaces generated using the model domain polygon did not fully span the model domain due to differences in numerical precision.
  • LST file takes a long time to print for transient models
  • Unhandled Exception when viewing certain .DXF files with unsupported components in a 2D Viewer
  • Performance Issues on Project Load and Reload
  • In some cases, not all observations are included when exporting data from the Calc. vs Obs. Chart
  • In some cases, linear boundary condition features were skipped during conceptual to numerical model conversion.
  • Concentration output nodes are not always created in RT3D runs
  • Conceptual BCs assigned to the model sides not assigned as expected following conceptual to numerical model conversion to a finite difference grid if the grid cells are thin and/or there are steep gradients at the model edge.
  • Uncaught exception visualizing Fluxes when budget file is removed
  • View Maps not showing heads output
  • Can’t assign wells using Wells data object on Q-Grid
  • Well Edit form dives under the main Flex window
  • Only the first stress period values for bed leakance were included in LAK package translation

Version 6.0 | Build 6.0.7003.0 (Mar 2019)


MODFLOW-USG Workflow Enhancements:

  • Build your unstructured MODFLOW-USG model using the same workflow steps and tools as in a structured Finite Difference model:
    • Define Modeling Objectives
    • Specify Model Properties
    • Add Boundary Conditions
    • Define ZoneBudget Zones
    • Add Particles
    • Translate and Run
    • View Results as Maps and Charts
  • Define quadtree grids (Q-Grids)
  • Refine vertical layers when creating unstructured grids
  • Make use of advanced translation settings allow you to fine tune package settings and control which individual packages are translated and run during model simulations
  • Support for the MODFLOW-USG Ghost Node Correction (GNC) Package
  • Flex is now installed with MODFLOW-USG v1.4, the latest official USGS version as of the release date of Flex 6.0

Particle Tracking:

  • Support for MOD-PATH3DU which enables particle tracking in unstructured grid (MODFLOW-USG) models. NOTE: MOD-PATH3DU must be downloaded and installed separately.  It is available for free by registering at the S.S. Papadopulos, Inc website for MOD-PATH3DU (
  • Enhanced particle tracking capabilities allowing you to define:
    • Groups of particles that can be tracked and visualized separately
    • Separate particle release times for each particle group
    • Locations of particles based on existing or drawn point, polyline, polygon, or well features
    • Particles in cross-section views (i.e. row and column views) of a finite difference model
    • Particle elevations based on layer(s), a surface, or a constant elevation

ZoneBudget Improvements:

  • ZoneBudget is now supported in unstructured MODFLOW-USG models
  • You can use point, polyline, or polygon features to define Zone Budget zones and zones can be specified directly using feature attributes from a data field

Visualization and Settings:

  • Visualize velocity vectors in finite difference and unstructured grids:
    • In-plane velocity vectors
    • Color maps of out-of-plane velocities
    • Display average or Darcy velocities (total or in-plane) or by direction
  • Specify a line feature along which to show cross-sectional color maps of unstructured grid model properties and outputs
  • Cell Inspector now includes Layer/Model Top and Bottom elevations, and the magnitude and X-, Y-, and Z-components of the average/Darcy groundwater velocity
  • When creating horizons, you can preview how the rules will be enforced in the 3D Viewer rather than viewing the raw surfaces.

Packages, Properties, and Boundary Conditions:

  • Field calculator/expression builder includes
    • cell geometry variables: Cell Bottom ($BOT), Model Bottom ($MBOT), Cell Thickness ($DZ), Cell Width ($DX), and Cell Length($DY) and
    • additional functions: LOG, LOG10, NOT, ABS, DOT
  • Copy Model (Flow/Transport) Properties and Boundary Conditions to from one Layer, Row, or Column to other Layers. Rows, or Columns
  • Edit cells (active/inactive, zone budget) in row/column views

Data Import/Export:

  • Import distributed property values from Classic Models
  • Use a source data field to map feature elevations when importing point, polyline, and polygon data
  • Model outputs including groundwater heads, drawdown, velocity, and concentrations can be exported to text files
  • Export contours as polyline shapefiles

Usability and Other Enhancements:

  • Observation Wells can be specified as separate groups
  • Performance improvements on project open and close operations for larger projects
  • Output Control file translation supports keywords or codes and the standard or compact budget formats to provide support of MODPATH and mod-PATH3Du.
  • Added MT3D-MS and RT3D summary output (.OT) files to the open files dialog at the model run step

Defects Addressed:

  • Intermittent and unhelpful translation error “Vmac is running in the task bar, please close it and try again”.
  • Deleting particles by drawing a box does not actually delete particles
  • Well schedule not translated correctly if the project time unit is not in days
  • In some cases, particularly if the whole output water table exceeds the model ground surface it was rendered at Elevation=1
  • Modifications to a pumping well boundary condition propagate to all runs under the same grid
  • Concentration observations contained incorrect column names
  • Project Clean-up/Remove orphan objects from model
  • If all boundary conditions of a given type were deleted, they would still run in the model due to advanced run settings. You are now prompted to remove the translated file or back-it up so that it no longer runs in the model
  • In some cases, the schedule for pumping wells with relative times does not import correctly
  • In some cases, assigning a schedule to a conceptual boundary condition results in an error message that the schedule occurs before the model start date even if this is not true
  • Concentration observations incorrectly handled for simulations with multiple species
  • Transient Fluxes (Model Results) are not shown or exported, only Flux from first time step.
  • Fluxes not displaying properly in 3D Viewer
  • Cells remain active if boundary condition is applied to ‘Top’ of model domain
  • MODFLOW-USG, BCF package fails to translate if property values are edited
  • When using a uniform grid, the CM->NM conversion does not add conceptual BCs assigned to model top to Layer 1 rather than the upper-most active layer
  • When importing heads file as 3D gridded data to a Rotated Grid Project, error “Object reference not set to instance of object” appears
  • Inconsistent/compound units are not correctly converted for certain RT3D reaction parameters
  • Water table for USG does not take ponding into account
  • Reinstalling Visual MODFLOW Flex does not replace MODFLOW-SURFACT with the demo version in the engines folder
  • Flex does not always cleanly delete elements from the Model Explorer, resulting in large file sizes
  • In some cases, MODFLOW-USG conceptual model conversion results in incorrect parameter values, and causes parameter editing to fail
  • Out of memory error when attempting to display certain DXF files in 2D view of Flex viewer or standalone 2D viewer
  • Multiple Lake BCs result in a multiple key error upon translation

Version 5.1 | Build 5.0.6759.0 (Jul 2018)

Defects Addressed:

  • SSM schedule not correctly translated for models when the flow model was steady state.

Version 5.1 | Build 5.0.6750.0 (Jun 2018)


Data Import/Export:

  • Surfaces created in Visual MODFLOW Flex can be exported as Surfer ASCII grid files (.GRD) for use in other Visual MODFLOW Flex projects and other software packages (e.g. Surfer, ArcMap, QGIS).
  • Pumping Wells in Visual MODFLOW Flex numerical models can be imported as text files (.CSV) using the same format that they are exported from Flex projects allowing you to transfer Wells between projects.

Visualization and Settings:

  • Vertical exaggeration in 3D views can be manipulated by keyboard commands.

Packages, Properties, and Boundary Conditions:

  • Field values for Properties and Boundary Conditions are available as variables in the Expression Builder.

Grid Editing:

  • You can now specify which numerical model run(s) are carried over when performing grid edits.

Defects Addressed:

  • In some scenarios (for instance if CHD cells are specified at the very bottom of the model [such as in the Henry model]), the parallel version of SEAWAT may have convergence problems that cannot be resolved by changing solver parameters.
  • SEAWAT engine run output was truncated and formatted incorrectly.
  • Concentration values of -1 in the specified concentration boundary condition (indicating the species should be skipped) were incorrectly translated to the SSM file as 0.
  • Error in translating diffusion arrays to the DSP package when specifying the Multidiffusion option in MT3D-MS or SEAWAT runs.
  • In rare occasions, property zones were set to -1 and uneditable.
  • In some cases, successive model translation times increased due to a memory leak.
  • In ZoneBudget runs, Flex does not read in values for zones that are not directly adjacent to Zone 1.
  • Errors thrown if user skips straight to Translate without selecting an engine.
  • In some cases, changes to stress periods do not update instantly to the translation settings resulting in incorrect translated time discretization and/or output control (.OC) files, following changes.
  • In some cases, PEST results will not update correctly into a new run.
  • An error is shown when user clicks […] button to change the path to Previous MODFLOW Run HDS file if the HDS file is not present.
  • Hitting Apply in the Settings dialog for a concentration doesn’t update the BC view properly.

Version 5.0 | Build 5.0.6597.0 (Jan 2018)



  • Visual MODFLOW Flex now supports SEAWAT (v4.00.05), a three-dimensional variable density flow and multi-species solute transport model developed by the USGS, based on a combination of MODFLOW and MT3D-MS.  Version 4 of SEAWAT also supports viscosity effects and heat transport.
  • The following SEAWAT flow packages are supported in Visual MODFLOW Flex:
    • BAS6 – Basic Package
    • DIS – Discretization Package
    • BCF6 – Block-Centered Flow Package
    • LPF – Layer Property Flow Package
    • OC – Output Control Package
    • RCH – Recharge Package
    • EVT – Evapotranspiration Package
    • WEL – Well Package
    • DRN – Drain Package RIV – River Package
    • GHB – General-Head Boundary Package
    • FHB – Flow and Head Boundary Package
    • CHD – Time-Variant Constant Head Package
    • LAK – Lake Package (LAK3)
    • HFB6 – Horizontal Flow Barrier package (HFB6)
    • OBS – Observation
    • HOB – Hydraulic-Head Observation
    • GMG – Geometric Multi-Grid Solver
    • PCG – Pre-conditioned Conjugate Gradient Solver (PCG2)
    • WHS – BiCGSTAB-P Matrix Solver
    • LMG – Link Multi-Grid package for using the SAMG (Systems Algebraic Multi-Grid) Solver
  • The following SEAWAT transport packages are supported in Visual MODFLOW Flex:
    • VDF – Variable Density Package
    • VSC – Viscosity Package
    • BTN – Basic Transport
    • ADV – Advection
    • DSP – Dispersion
    • SSM – Source/Sink Mixing
    • RCT – Reaction Package
    • GCG – Generalized Conjugate Gradient Solver

NOTE: Advanced Translate/Run Settings (see below) enable partial support for simulating additional processes/packages (e.g. subsidence, drain return) developed outside of Flex.


  • Visual MODFLOW Flex now supports RT3D (v2.50), an advanced reactive transport engine based on the popular MT3DMS transport engine.
  • The following RT3D reaction modules are supported in Visual MODFLOW Flex:
    • Instantaneous aerobic degradation of BTEX.
    • Six Species, First-Order, Rate-Limited, BTEX Degradation using Sequential Electron Acceptors
    • Rate-Limited Sorption
    • Double Monod Model
    • Sequential First-Order Decay (up to 4 species, e.g., PCE/TCE/DCE/VC)
    • Aerobic/Anaerobic PCE/TCE Dechlorination

Visualization and Settings:

  • Cell Inspector: View and inspect structured and unstructured models at the cell-level using the new cell inspector, available in the workflow viewers. The cell inspector displays cell values for user-specified input and output data fields.
  • Status Bar: Cell dimensions have been added to the status bar.
  • Time-Picker: A time-picker is now available for unstructured grid workflow viewers.
  • Layer-Picker: A layer-picker is now available for unstructured grid workflow viewers.


  • Additional Translation/Run Settings: Added advanced settings for all supported engines (excluding MODFLOW-USG) so that you can specify whether individual packages are translated and/or run with the model, which provides the flexibility to integrate your own package input files within the Flex environment.

Property and Boundary Condition Tools:

  • Field Calculator: Populate boundary condition fields using a calculator that includes an expression builder dialog to facilitate the inclusion of variables based on your model’s properties (e.g. grid dimensions, elevations).
  • Dispersion Parameters: Values can be edited in the Dispersion Parameter Dialog using copy, paste, and fill commands.

Usability and Other Enhancements:

  • Easy Classic Importing: Import your Classic project into Visual MODFLOW Flex directly from the file menu.
  • Import Classic Concentrations: Boundary condition concentrations are now imported from Classic Projects.
  • Animate Relative times in 3D views: in 3D View animations, the time stamp label for heads can be specified in relative or absolute time.
  • Descriptive Title Bars for Settings Windows: settings windows now display descriptive window titles including the data layer and viewer settings to which they apply.
  • Rename Objects: objects in the Data Explorer and most objects in the Model Explorer can be renamed.
  • Feedback Button: added anonymous feedback buttons so that you can easily report what features you like or don’t like.
  • SAMG Solver: added a single-processor version of the SAMG solver for Visual MODFLOW PRO users.

Defects Addressed:

  • Defining BCs along irregular polylines that are close to the active model limits produced unexpected results
  • Reorder Tool was missing in some views
  • The Show/Hide Gridlines button and associated toolbar disappeared intermittently from the viewer
  • Well Data import failed without warning the user that the pumping schedule had inconsistencies, including pumping start date before model start date or pumping start date after pumping end date
  • User could not assign polygon attribute data to conceptual recharge/evapotranspiration elements
  • Problem(s) with Time Series Viewer
  • Multiple PEST Workflows could be created for the same model run which corrupted the PEST workflow.
  • Multiple issues in the advanced run/translation settings
  • PCG Solver translation settings of the PCG2, PCG4, and PCG5 solver packages for MODFLOW-SURFACT models

Version 4.1 | Build 4.0.6408.0 (July 2017)


Visualization and Settings:

  • 2D/3D View Keyboard Navigation: Navigate in the active 2D or 3D view using the keyboard. Arrow keys pan the view, +/- keys (on the number pad) and page up/page down keys zoom in and out. In an active 3D view, the +arrow up/down keys changes the inclination of the model relative to the horizon and +arrow right/left rotates the model about the vertical axis
  • Custom Contours: Customize contours in 2D, 3D, and Flex Viewers by setting start and finish contour values for contour lines and isolines. You can also specify a contour interval. Changes in one part of the Flex Viewer are reflected in the other parts.
  • 3D View Setting Defaults: Create and Save Project-Specific Default View Settings for each each data type in the 3D Viewer.
  • Time-Series Viewer: View time series data such as heads, saturation, and concentration at points within transient models without specified observation points


  • Modeling Objectives: Modeling Objectives for Transport Simulations can be changed at any time, not just during initial setup or conversion.
  • Model Settings for Translate/Run: You can now specify whether individual packages are translated and/or run with the model, which provides the flexibility to use your own packages similar to the advance settings in Classic for model translate/run

Grid Editing Enhancements:

  • Cell Size Control for Conceptual Models: Similar to numerical grids, you now have full control over the grid cell size specification during initial grid creation; you can set grid cells to whole numbers for ease of calculation and reporting.

Property and Boundary Conditions:

  • Boundary Conditions in LGR Models: Boundary conditions that span the parent/child grid interface(s) in an LGR model can be specified in both the Conceptual and Numerical workflows.
  • Dual Domain mass transfer: Flex now supports dual domain mass transport modeling through the MT3DMS and MODFLOW SURFACT (see below) transport engines.
  • Unsaturated Zone Flow (UZF) Package: Flex now supports 1-D unsaturated flow associated with the UZF package.
  • Time-varying Material Properties (TMP) Package: Flex now supports the TMP package associated with MODFLOW-SURFACT

Updated Engines:

  • Upgraded MODFLOW 2005: Flex is now packaged with MODFLOW-2005 v1.12.00, the latest official USGS version as of the release date of Flex 4.1.
  • Upgraded MODFLOW NWT: Flex is now packaged with MODFLOW-NWT v1.1.2, the latest official USGS version as of the release date of Flex 4.1


  • Added Support for MODFLOW SURFACT: Visual MODFLOW Flex now supports MODFLOW SURFACT Version 4.0, a fully-coupled flow and transport engine developed by Hydrogeologic, Inc. which features many robust methods and enhanced simulation capabilities for handling complex saturated/unsaturated subsurface flow and transport processes. Based on the USGS modular groundwater flow model, MODFLOW, it supports the following packages:
    • BAS4 – Basic Package
    • BCF4 – Block-Centered Flow Package
    • BTN1 – Basic Transport Package
    • TMP1 – Time-Varying Material Properties Package
    • CHD – Time-Variant Specified Head
    • DRN – Drain Package
    • EVT – Evapotranspiration Package
    • FHB – Flow and Head (Time-Varying) Boundary
    • FWL5 – Multi-Node Fracture Well
    • GHB – General-Head Boundary
    • HCN1 – Prescribed-Head-Concentration Boundary
    • HFB – Horizontal Flow Barrier (Wall)
    • LK3 – Lake Package V3
    • PCN1 – Prescribed-Head-Concentration Boundary
    • RSF4 – Recharge-Seepage Face Package
    • RIV – River Package
    • WEL – Well Package
    • HOB – Head Observation Package
    • OBS – Observation Nodes
    • OC – Output Control
    • PCG5 – Preconditioned Conjugate Gradient Solver
    • SIP – Strongly Implicit Procedure
    • SAMG – Algebraic Multi-Grid Solver
    • GMG – Geometric Multi-Grid Solver
    • WHS – BiCGSTAB-P Matrix Solver
  • NOTE: MODFLOW SURFACT was developed by Hydrogeologic, Inc. and is sold as a separate add-on for Visual MODFLOW Flex. A demo-version that supports model grids of up to 10,000 cells is included for evaluation purposes. Additional packages (e.g. subsidence [SUB], streamflow routing [SFR], etc.) are supported by SURFACT and may be developed outside Flex.


  • Undock/redock Tabs: Tabs can be undocked as separate windows. Simply drag and drop or right-click on the Tab name and select the “Undock Tab” option and you can place the new window anywhere on your monitor screen(s). Redock a window back to the main program window using drag and drop or right-click and select “Dock Tab” option.
  • Explorer Support: Open a Visual MODFLOW Flex .AMD file directly from Windows Explorer.
  • .Net Framework 4.6.1: now bundled with Flex installation
  • About/Splash Screen: Version and Build number are displayed on the Splash Screen and on the About Screen.
  • Improved Performance: Improved memory handling and performance enhancements

Defects Addressed:

  • Could not edit or define a Boundary Condition when multiple grids were present as part of the same LGR grid
  • Inconsistency between calculating and displaying leakance in the lake boundary condition when using certain time units
  • Some PEST runs were not successful due to incorrect observation files.
  • Issue when importing time schedules for recharge package
  • Translation issue when importing some Visual MODFLOW 2010.1 Classic projects into Flex.
  • Progress bar does not provide adequate feedback when opening large projects
  • Issue with extracting multiple species from sub-grids for MT3DMS runs
  • Toolbox was blank after translating/running the model and clicking Define Properties step
  • Translation issue in MT3DMS RC3 file for bulk density values when using inconsistent units
  • Improved feedback/reporting for certain engine runs that do not converge

Version 4.0 | Build 4.0.1039.3 (December 2016)


Grid Editing Enhancements:

  • Numerical grid editing – you can now edit your numerical grids after they have been created.
  • Fractional grid refinement – Allows you to change grid spacing by a fraction, rather than just whole number. For example; you can choose over a specified model area to convert every 3 rows or columns to 2 rows or columns (or whatever fraction you wish). This is particularly useful for grid smoothing to ensure that grid step sizes aren’t too large.
  • Cell size control – Full control over the grid cell size specification during initial grid creation; you can set grid cells to whole numbers for ease of calculation and reporting.
  • Grid quality indicators – Visual indication during grid editing of cells that violate the maximum cell step size, and flexibility to define the cell step size tolerance for each grid, so you can ensure a high quality grid and reduce potential for grid-based dispersion and/or larger computational times.

Property and Boundary Condition Editing Enhancements:

  • Cross-Section assignment – Assign or edit boundaries and properties in cross-sectional views.
  • Calculated value support – Use calculated values to determine boundary condition attributes, such as conductance and cell in-flow rates.
  • Boundary condition validation – Internal system checks on assigned boundary conditions to ensure that they meet MODFLOW engine requirements – For example; start and ending heads are above cell top. Flex automatically suggests corrective actions for any violations.
  • Multi-segment linear interpolation for boundary condition values – Now you have full control to define linearly interpolated values over a section of a boundary, or multiple segments with different linear interpolations as needed, to simplify assigning the boundary values you want.
  • Copy/paste and bulk property or boundary value assignment – If you have your values already defined outside of Flex, you can now quickly copy and paste them right into the boundary or property zone dialogues.
  • Need a way to insert the same value in multiple cells? Now you can do that too with one click or keystroke.
  • Visually interactive editor – Would you like to edit boundary or cell values cell-by-cell to improve your model calibration? The new visually interactive editor lets you select a value and see where the cell is located in the grid viewer, or, select a cell in the grid viewer and directly edit the cell values.

Other Enhancements:

  • Sub-grid creation – quickly create a new model based on a sub-grid from a larger model (including creation of all appropriate boundary conditions) with two mouse clicks.  This is particularly useful for creation of local transport models from larger scale flow models.
  • DXF support – display 2D or 3D DXFs in any of the Flex viewer windows to use as base-maps and help understand and place simulation results in real-world context.
  • Heads from a previous run – use heads files from previous model runs as the starting point for new model runs.
  • FlexScript DSL scripting – Hate the mouse and love your keyboard?  Now you can use FlexScript to make quick adjustments or exact replicas of grid designs, property, and boundary specifications without having to click-through the user interface.

Defects Addressed:

  • Numbering of Conceptual Model horizons is now consistent with zones.
  • Updated the import project file dialog to allow all supported file types.
  • Fixed a cosmetic issue with the Workflow Diagram legend message.
  • User cannot enter invalid characters when creating a numeric grid.
  • An issue with project naming which prevented the model from running has been resolved.
  • Inactive legend labels are no longer shown in the chart view.
  • The Next and Previous workflow arrows are now disabled during engine run and translation.
  • Inconsistencies with how the Model Explorer handles click events have been fixed.
  • Rotated surfaces in the 3D viewer now always align and correctly cover the grid.
  • The “User Virtual Grid” style setting is now correctly saved during project save/load.
  • An intermittent issue displaying wells in the 2D viewer has been corrected.
  • Enabled Wells in View Charts is now saved after successive translate and run operations.
  • Transport settings are now correctly synced between the conceptual model and numerical model.
  • An intermittent error when drawing a polygon property zone has been resolved.
  • You are no longer able to launch multiple identical property dialog boxes.
  • VMOD Flex now saves your current workflow step when saving a project.
  • All style settings are now saved when a project is saved.
  • Some minor color issues with the 2D/3D view have been corrected.
  • An occasional error when unchecking the “User Virtual Grid” checkbox in the standalone 3D viewer has been resolved.
  • When cloning a model run the wall boundary condition is now always included.
  • Occasionally duplicate run nodes were displayed in the Model Explorer.  This scenario has been resolved.
  • Minor label fixes were applied to the calibration charts.
  • Issues adding initial head and storage properties in the conceptual workflow have been addressed.
  • MODFLOW run project files are now always cleaned up when a model run is deleted.
  • An incorrect warning message presented during the conceptual model boundary condition creation step has been removed.
  • All boundary condition attributes are now being correctly saved when edited.
  • Some project properties which are not editable are now correctly displayed.
  • The 3D view wireframe selector’s state is now correctly saved during project save/load.
  • All chart settings are now correctly retained on project save/load.
  • An incorrect warning message no longer displays when changing the Damping Factor (DAMP).
  • Installation issues with the MS Visual C++ package have been addressed.
  • Duplicate entries in the Windows Programs & Features list have been removed
  • An error adding data to the composite view for certain projects has been corrected.
  • When exporting the Water Table the elevations column has now been included.
  • A validation message displayed during River boundary condition validation now lists the problems detected.
  • A warning message is no longer incorrectly displayed when a well pump start date is the same as the model start date.
  • Icons in the view charts legend have been resized.
  • The “Open Workflow” window has been made resizable.
  • Improper translation of a constant head boundary condition between conceptual and numerical models has been fixed.
  • Settings for Flux boundary conditions are now available.
  • Shapefiles that contain attributes are now able to be imported.
  • Error log location has been added to error messages.
  • The (S)AMG solver feature is now available to premium users.
  • A scenario where mass balance results were not available has been resolved.
  • Creating a USG boundary condition of the same name no longer causes an error.
  • Inactive cells are no longer rendered with flux values.
  • A rare condition where the boundary condition dialog opens and is blank has been resolved.

Build 3.0.786.16 (March 2016)

Defects Addressed

  • Recharge boundary, assign to polygons with “Apply to All” was not working
  • River boundary condition with linear interpolation conceptual to numerical conversion was not working
  • Updated website links for web help and release notes
  • Added support for Windows 10

Build 3.0.653.1 (December 2015)

Defects Addressed

  • Error when exporting heads to shapefile, and selecting all output times
  • Opening project gives error “Error loading finite difference mesh” numerous times
  • Trying to export Calc vs Obs chart data to .CSV causes “Cannot export Calibration data. the given key was not present in the dictionary” error (project specific)
  • Translating and running the project and viewing the output node, shows concentrations for elements undefined in the model
  • Conceptual Model is frozen, non-responsive (on Windows 10)
  • Error during saving project (on Windows 10)
  • USG model cannot load water-table after model run
  • Sink/Source Boundary condition Package translator. Translation failed error
  • Assigning Isosurfaces for conductivity causes error
  • Transient model flux output does not change with time in 3D Viewer
  • Using polyline object to assign constant head boundary condition creates various numbered zones in define boundary condition step
  • Well Translation Failed (project specific)
  • Heads results are different/incorrect for imported Classic models (when using distributed property zones)
  • Create Pumping Wells window, the OK button is cut off on low resolution or large font sizes
  • When importing 3D Gridded data, Tecplot .DAT format, rotated grids are now supported

Build 3.0.507.4, v.2015.1 Release (June 2015)


  • Added support for MODFLOW-NWT: translate NWT and UPW package, import MODFLOW-NWT model from VMOD Classic.
  • Added options to modify MODPATH results: adjust pathline travel time and time marker frequency
  • During import of wells (pumping or observation) in absolute times, show warnings of any well data that comes before the model start date
  • When define obs. wells, added check for observation dates to be equal to or greater than the modeling objectives start date, and show any offending records
  • Added option to Assign Single or Assign Line for define properties, in the numerical modeling workflow (regular MODFLOW)
  • Added option to “Assign/Single” for inactive cells in numerical workflow
  • Added option to copy boundary condition cell geometry and parameters to other layers in the numerical modeling workflow (regular MODFLOW and MODFLOW-LGR only)
  • Update Export option for Forward/Backward pathlines to use the adjusted pathline length and defined time markers
  • Added units to the Boundary Condition parameter windows
  • Added a new “Object list in view” section to the Flex viewer, to simplify access to settings and options for data objects displayed at a particular workflow step
  • When creating pumping well boundary conditions, added validation for start time for source data to ensure schedule comes on or after the model start date. In addition, for wells that start at different times, added option to automatically insert zero pumping rate until the schedule is defined
  • During Conceptual Model to Numerical Model conversion (regular grids), honour varying boundary condition end times in the resulting numerical model
  • Remove default start date (of today) in the modeling objectives section, for Numerical Model and Conceptual Model
  • Disabled option the change the model start date in the modeling objectives, since this had no impact on the numerical model start time, and only affected the start date for conceptual boundary condition objects; this created confusion for pumping wells/obs. well data that may have been imported with different absolute times
  • Added option to set time periods as active/inactive for numerical boundary conditions (CHD, RIV, GHD, DRN, Specified Flux, LAK), for regular MODFLOW
  • Translate boundary condition time periods “inactive” to appropriate packages (CHD, River, Drain, GHB), by inserting 0 cells for the specific stress periods
  • In the settings for wells data object spreadsheet, added an option to show pumping well schedule or observation times, as relative times.
  • Added option to show water table as a surface (contours/color shading) in 3D Viewer, for MODFLOW-USG runs
  • Added an option to export water table to CSV file, for MODFLOW-USG models
  • Add a legend option to the style settings for water table (surface) for 3D viewer, for MODFLOW-USG and regular MODFLOW
  • When defining active/inactive cells (regular MODFLOW), provide option to have the cell assigments span multiple layers in the model
  • Added an option to change an existing numerical boundary condition from steady state to transient
  • Added new operation for surfaces: Add, Subtract, Multiply, or Divide Z value for a surface, and save as a new surface data object
  • Added option to import observation wells object (heads and concentrations) in relative times from XLS file.
  • Adjusted the import from VMOD Classic option, for wells with point source concentrations, to account for the new pumping wells object with species concentrations
  • Added option to import raw pumping wells in relative times from XLS file.
  • Added option to view/edit observation data (in the regular MODFLOW numerical model) in CSV file, then reload edits back into the model
  • During translation, extend boundary condition stresses to the maximum end time from all boundary conditions, and add “zero” entry for the cell count to the translated package (regular MODFLOW-2000); behaviour similar to VMOD Classic.
  • Added an option to export new pumping wells object to CSV file.
  • Improved error handling and warning message in the event that a MODFLOW run does not converge.
  • Added a mechanism to notify user if they open a project that is created in a newer version of VMOD Flex, when running an older version (will only work for projects in v.2015.1 and future versions of the software)
  • Added a “Finish and Cancel” button to toolbox when doing assign and editing in the numerical model workflow, to improve usability
  • Added warning message when users attempt to edit “old” numerical pumping wells, with suggestion to convert these into “new” pumping wells.
  • Added translate active flag for new well, to basic WEL package
  • Added option to define species concentrations to entire well interval, for new wells object
  • When define boundary condition, using polyline or polygon, added option for attributes to apply defined values/methods for one polygon/polyline to all other polygons/polylines in the selected data object
  • Added option to add one or more new wells with a mouse click, in layer view, for regular MODFLOW models
  • Added option to recognize the active/inactive flag for pumping wells, when import a model from VMOD Classic
  • Added option to set pumping wells as active/inactive, in the new wells interface
  • Added option to see contours/color shading for Fluxes (in X, Y, or Z direction) in 3D viewer (for regular MODFLOW models)
  • Added option to edit conceptual pumping well boundary condition object, after it has been created (for new well model only)
  • Added option for color legends for USG models (properties, heads) to recognize user-defined values from the color settings
  • Added option to save the scene manipulation for USG models in 3D Viewer, after doing save and reload project
  • Added option to create new well boundary condition from within a numerical workflow (using existing well data object from data explorer)
  • Added option to create new well boundary condition in a conceptual workflow, using data object
  • Added a maximum horizon quality of 1000 rows * 1000 columns to improve performance based on “typical” model surfaces and scales; for more details on adjusting this, please contact technical support
  • Added options and toolbar to Data tab and Model explorer to collapse, move, and hide this panel
  • When import model from VMOD Classic, with recharge and EVT time periods set as inactive, set these time periods to have 0 recharge or EVT rate
  • Renamed Logger to Obs.Point in the wells import at the data mapping step
  • Renamed Logger to Obs.Point in the wells settings

Defects Addressed

  • After edit the end time of an existing transient numerical boundary condition, returning and editing the value, it was not saved
  • After importing a model from VMOD Classic, some rewetting options at the Translate/Settings step were not correctly set
  • In certain cases, data objects on Data panel were disabled for 3D viewer inside the MODFLOW-USG workflow
  • Anisotropy calculation for LPF package (regular MODFLOW) used Kx/Ky instead of Ky/Kx (when using the anisotropy as specified option)
  • BCF package translation (for regular MODFLOW) was incorrect for layer type 0 and 2 (transmissivity values not correctly calculated)
  • In the Edit Boundary Condition window, the defined data values were not being saved in the scenario where you add a time schedule to a transient boundary condition
  • BTN translation (for MT3DMS) did not take into account spatially-varying porosity values; it always translated one constant value per layer
  • BTN translation (for MT3DMS) was incorrect for dY calculation (column array (DELC)
  • Could not delete boundary condition items from Model Explorer in a MODFLOW-USG numerical model
  • Incorrect cells rendering of Concentration output in a stand-alone 3D viewer
  • Colors of conceptual property zone objects were not saved in 3D viewer, after save/reload
  • Species concentration numerical attributes did not appear when editing specified flux boundary condition object, with concentration values defined
  • In some cases, species concentration values assigned to specified flux oundary Condition were not translated to SS3 (MT3DMS) package
  • Conceptual to Numerical conversion failed when river boundary condition was selected when the option “Define values at vertices (Linear Interpolation)” was used
  • Conductance value for river object after Conceptual to Numerical Model conversion was incorrect (due to river in inactive cells)
  • Contour lines of surface object were not properly turned off in 3D view
  • Delete menu option for head or concentration obs wells object on Model Explorer did not work
  • Deleting files from conceptual model explorer did not delete all files from the “Arrays” folder on data repository.
  • Deleting grids from the Model Explorer tree, after save and close, and reload, the numerical grids sometimes re-appeared on the model explorer
  • Deleting model run from the Model Explorer in a USG workflow did not delete all related files from the project folder on the hard drive
  • Deleting grid from Model Explorer did not delete GriddedPlugin objects from the .data folder.
  • Deleting numerical models with recharge did not delete .CDF files from data repository.
  • Deleting objects from model explorer did not clean up corresponding files in data repository, and leads to large data repository folders with obsolete files.
  • Deleting runs from model tree did not delete associated files in the data folder
  • Fixed the description of parameter names in the .MPT package
  • Could not close 2D viewer when in pick/edit mode, after doing edit wells, then close project.
  • Addressed errors when opening a complex polygon in 3D viewer
  • Improved error handling when MODFLOW-LGR run fails to converge
  • Addressed errors when using the operation Z=Surface for a map image.
  • Addressed errors when assigning particles, if circle of particles are outside model domain
  • Fixed buttons that were cut off on the Grid at the Translate step in numerical workflow
  • Fixed color legend in 3D viewer when you change background color to anything but black
  • Fixed order of columns for head and concentration obs. data in raw wells spreadsheet
  • Addressed error during Conceptual to Numerical Model conversion (regular grid) for constant head with linear gradient, which used intermediation layer option
  • Addressed errors “Cannot find finite difference grid” after loading old project where a grid was deleted
  • Addressed cleanup of the Grid folder (from project data repository) when an UnStructured grid was deleted from the Model Explorer
  • Addressed problem of MODPATH, ZoneBUDGET and MT3DMS starting in the event that the MODFLOW model failed to converge
  • Fixed issues with .WEL package not matching the .WEL package from a VMOD Classic model (project specific)
  • Added units to the property zone database window in numerical model workflow
  • Addressed problem of incorrect assignment of active cells when creating a new numerical grid with rotation angle exactly 45 degrees
  • Addressed problem of incorrect observation values after copy from excel, save, close and reopen View Spreadsheet
  • Addressed problem of LMG file being included with translation even though this solver was not selected
  • Addressed problem of MODPATH .MPT.ep porosity translation (only when you have spatially-varying porosity values)
  • Multiple forward particle data objects were added to the model explorer, when working with multiple model runs (there should be only one per numerical model)
  • Improved the behavior of assigning new property zone in the numerical model using polygon, where the polygon extends outside of model domain or covers inactive cells
  • Improved the display of the validation screen at the end of data importing, on Windows 8.1
  • Addressed incorrect import of porosity values when importing a model from VMOD Classic
  • Property zones with polygons were not converted correctly to all layers in the model
  • Encounter out-of memory issue when doing concpetual to numercial conversion, with large grids, when consecutive executions (typically more than 10 times)
  • Improved the Project/Save As performance and processing time
  • Improved the Project Save and Project Open time, due to the large project directory size that contained obsolete grids and model runs files
  • SSM (MT3DMS) translation did not include values from constant concentration, after save and reload project
  • Storage values are translated incorrectly for LPF and BCF package (for regular MODFLOW), when values are spatially-varying per layer
  • Surface in 3D or 2D viewer did not allow to turn off color fill and show only contour lines.
  • The check box beside boundary condition group folders in the model explorer (Numerical Model) did not show up after save and reload project
  • The defined name for new Conceptual Models was not being used in the Model Explorer
  • Translation for FHB package was incorrect for Transient mode
  • Translation for WEL package was incorrect for MODFLOW-LGR model, when well is screened over multple layers.
  • Addressed error when viewing water table (project specific)
  • Addressed error when trying to assign Constant Concentration to “Sides” of model domain
  • Improved usability issues when defining Boundary Conditions to the sides (selecting faces/sides)
  • Improved the save/reload states for 3D viewer in a USG numerical model workflow, including selected data objects, property zone selection, and style settings
  • Addressed problem of incorrect constant head attributes converted to numerical model, when using linear interpolation and transient attributes
  • Addressed problem of incorrect constant head cell location after converting from a conceptual model (project specific)
  • Addressed problem of contour interval setting not working for Layer View, when viewing Heads/Concentrations
  • Addressed problem with program not responding during Conceptual to Numerical Model conversion for complex Drain Boundary Condition and multi-layer numerical grid (project specific)
  • Addressed problem of incorrect .WEL translation in certain cases where there are inactive cells
  • Addressed problem of incorrect .WEL translation in the case where a well lies in a child grid that had layer refinement different from parent grid
  • Addressed incorrect Conductance calculation (for River, Gen Head, and Lake) in the case where the units for Conductivity were in a different convention then the project length and time units
  • Improved clean up of project data repository folder, after deleting Grid and Run objects from the model explorer
  • Addressed problem of icon changing in 2D viewer when doing editing.
  • Addressed problem of last selected folder not being saved, when doing consecutive import of data objects using File/Import.
  • Addressed incorrect .LPF package translation (regular MODFLOW) in the scenario where cell re-wetting is active and the model contains inactive cells.
  • Addressed differences in the displayed output times for Heads & Drawdown when comparing the list of times in 3D viewer settings vs. those shown in the Flex viewer, for transient MODFLOW runs

Build 2.1.300.0 (November 2014)

Defects Addressed

  • Long processing time for .CSV editing and re-loading for a General Head Boundary condition group (MODFLOW-2000/2005)
  • After converting conceptual model to numerical model for a General Head  boundary condition assigned to the sides of the model domain, conductance value was being incorrectly calculated as 0 (MODFLOW-2000/2005)
  • Empty attribute data contained in the .csv file of river boundary after converting to a numerical model (MODFLOW-2000/2005) (project-specific)
  • Transport charts not showing up for models that used rotated grid (MODFLOW-2000/2005)
  • Transport charts not showing up when a grid cell contained more than one observation point (XY) (MODFLOW-2000/2005)
  • After refining a MODFLOW-2000/2005 grid, layer elevations were not re-calculated correctly.
  • Error when running animation for conceptual model structure in 3D view.
  • Error in converting the Specified Flux conceptual boundary condition (assigned to the sides of model domain) to numerical model (MODFLOW-2000/2005)
  • Translation error “The given key was not present in the dictionary” for certain projects. (MODFLOW-2000/2005)
  • Data operations, unable to assign the Z values of a polygon from the selected surface
  • Fixed Airport-Transport tutorial solution project files (previously was showing error when loading and also at the Translation step)

Build, v.2014.2 Release (July 2014)


  • Define New Zone Budget zones using Point, Polyline, and Polygon. (Available for MODFLOW-2000 and 2005)
  • Define Wall (HFB) boundary condition. (Available for MODFLOW-2000 and 2005)
  • Improved Options for Defining/Removing Particles
  • Show water table for structured MODFLOW models (plan, XS, 3D view). (Available for MODFLOW-2000 and 2005)
  • Edit numerical property zones or boundary condition attributes in CSV format, and reload back into the numerical model.
  • User-defined color classifications for color rendering (Heads, Conductivity, etc.)
  • Improved coloring of property/recharge zones, when render by ZoneID
  • Export chart data to CSV file
  • Support for rotated numerical grids in numerical workflow (when create new grids, for MODFLOW-2000 and 2005)
  • Improved usability for workflows (better defaults when importing models or generating numerical models from conceptual models)
  • Fix the default zoom level for the 2D (layer view) in the Flex Viewer, when at the View/Grid step and View/BC step (in MODFLOW-2000,2005 workflows)
  • Create the Grid Specification File (GSF) during MODFLOW-USG translation (reserved for future development, including MODPATH-3DU and PEST)
  • Export pathlines to polyline shapefiles
  • Add option to assign new Specified Flux Boundary (assign / polyline, assign/polygon), in the numerical workflow (Available for MODFLOW-2000, 2005)
  • When show unstructured grids in 3D viewer, added option to view the cell geometry as smoothed continuous  surfaces (and not discrete flat top/bottoms)
  • At the Define Boundary Condition step in numerical workflow, added option to create numerical boundary condition from existing data objects (polygon, polyline), (excludes Well objects.) (Available for MODFLOW-2000 and 2005)
  • Improvement in the way time schedules are handled for boundary conditions, to catch boundary conditions that have start/end times that are inconsistent with other boundary conditions.

Defects Addressed

  • Could not create thin layers (less than 0.01 m or ft) at the Create Grid step in Numerical workflow (MODFLOW-2000 and 2005)
  • When export raw point, polyline, or polygon data to shapefiles, VMOD Flex did not create shapefiles correctly. In some cases, the shapefiles could not be loaded in Third-party software
  • In the Import Data window, wells shows up twice in the list of data object types, after you close and reopen a project
  • The attributes below the Layer view (on status bar) did not refresh when changing the mouse locations for rotated grids.
  • Inactive cells were not showing up correctly for models with rotated grids
  • At the end of the PEST workflow, after save results as new run, in the new model run the head observations were not included on the model tree.
  • Could not create numerical grid with certain layer number configurations
  • PEST – after doing update model inputs,  the PEST workflow was also being cloned
  • When edit a conceptual boundary condition, the attribute values for species concentrations did not show up
  • In settings for imported 3D Grid object (.HDS) the transient output times were not showing correctly
  • During import VMOD Classic model with a few thousand wells, there was a very long delay when calculating time schedules
  • For a USG Grid, 3D Viewer, displaying Cells, the Legend option was not working
  • After import 3d grid object (HDS), the time values were not using the correct units from the project settings
  • Transparency did not work for 3D Gridded objects (eg. MODFLOW conductivity) for cells view
  • Error saving project, with USG numerical models (only occurred in certain computer/regional setting configurations)
  • Stand-alone 3D viewer was showing results from previous MODFLOW run (and was not refreshing after a re-run of the model)
  • After importing a Surface data object, when View Spreadsheet, values were showing duplicate XYZ values.
  • Storage property zone values were flipped/mirrored after importing a model from VMOD Classic
  • Error during import of project with rotated particles, and particles did not show in the correct location
  • 3D view, Z axis labels were mirrored/flipped, when viewing simple surfaces.
  • Improved the loading time in Flex viewer when displaying Recharge and EVT Boundary Condition cell zones.
  • Define Properties step in numerical workflow was reverting back to displaying Conductivity every time you return to this step
  • The status bar was cutting off the last few digits for Kx, when the value is E-04 range, and was incorrectly rounding up
  • When importing a surface, if you chose a text file that contains XYZ points, and not gridded ESRI ASCII .GRD, you got an error.
  • Improved engine run times by disabling detailed logging.
  • In PEST workflow,  were encountering error when trying to generate .PST file at the Sensitivity Analysis step (with certain parameter configurations)
  • When edit attributes for Specified Flux numerical boundary condition, the wrong units were being displayed.
  • MT3D runs failed due to problem with MXSS value in the SSM package
  • Improved error message at Translate step, when using the Initial Heads option “ Use Heads from previous MODFLOW Run” and the .HDS file could not be found
  • Error “object reference” occurs if you add a structural zone to the grid without first creating a new property zone (in Conceptual Model workflow)
  • Fixed the zoom level for 2D view by Row or Column,  when you adjust the vertical exaggeration
  • In 2D viewer, when editing points, it was taking a long time to add new points when other viewers were opened.
  • Unable to import well data (Excel data file-specific), and unable to convert pumping rates from L/day to project units.
  • 3D viewer, Settings/Isosurface, the correct values were not appearing when returning back to Edit an Isosurface
  • Added option to Edit/Single and Edit/Group for Specified Flux boundary condition in the numerical modeling workflow (MODFLOW-2000 and 2005)
  • MODFLOW USG, 3D viewer, showing slice, when reload style settings, make change to slice, it restores the Cells view.
  • Increased precision for the label for time values in the Head style settings
  • Improved the conversion time for Recharge and Evapotransperation boundary conditions when going from Conceptual Model to Numerical Model (MODFLOW-2000, 2005 and LGR)
  • Error when trying to create a surface with a blank point data object
  • Get error when creating a Surface if using points object created from an operation. (eg. well tops or HGA XS)
  • Fixed the behavior of the Assign and Edit buttons at the Define Boundary Conditions step (Numerical Workflow) in the event when you do not complete one of the selected actions; added an option to “Cancel Editing” when right-clicking on the view, will take you back to the original state.
  • Define Particles, when add new particles this was always overwriting the previously defined set of particles
  • Import Surface data object, if you chose a .txt file that is not ESRI ASCII grid format (such as XYZ points), you would encounter a non-user friendly error
  • When creating Voronoi USG grid consecutive times with the same grid generator settings, the resulting grid cell count was not exactly the same
  • Error message and program freezes when importing certain polyline objects

Build 2.0.102 (January 2014)

Defects Addressed

  • Problems importing 3D Gridded Data Object, TecPlot .DAT file format
  • PEST utilities were being flagged as potential virus threat on certain virus scanners
  • Inactive cells were showing up incorrectly in all layers of the model, instead of the specified layers
  • When using initial heads from a previous MODFLOW run, if the model contained inactive cells, the heads were not rendered correctly in the results
  • In some cases there was a problem using a .HDS file from a previous MODFLOW run for initial heads, when cycling between multiple projects
  • An error would occur when defining a new property zone with a polygon, after doing conversion from the conceptual model
  • Unable to create horizons for surfaces that have undefined values around the edges
  • When import polygon as .DXF format, in some cases the file would not load as a closed polygon

Build 2.0.88, v.2014.1 Release (November 2013)


  • added support for MODFLOW-USG
  • added option to define inactive cells for MODFLOW-2000/2005 grids in the numerical workflows
  • import transport boundary conditions when importing a VMOD Classic .VMF file project
    import concentration observation well data when importing a VMOD Classic .VMF project

Defects Addressed

  • in some cases, the cell attribute value for linear conceptual boundary conditions calculated using the method “Use Surface” were incorrect. The value was an average based on the min and max value from the start and end point of the line, as opposed to the actual surface value at the cell’s XY location. The magnitude of the error increases when the selected surface object has a wider range of max-min, and the line segment is longer.
  • fixed incorrect BT3 translation for initial concentrations for models that have inactive cells
    PEST translation, in some cases observations were not converted to the correct layer

Build 1.0.437.1, v.2013.1 Release (June 2013)


  • added support for defining and running transport models using MT3DMS
  • enabled the Create Numerical Grid step, with options to define the grid extents and define layer elevations (constant value) or with surfaces
  • improved the selection of workflow windows and viewer windows, with a “tab” approach across the top of the main window.
  • added option to define the layer order in 2D Layer views (and move layers up, down, to top and to the bottom)
  • improved Export PEST results to Charts; now populates pre-defined chart templates.
  • added option to delete Pilot points in the PEST workflow
  • improved error handling in PEST workflow, if you change the selected parameters, or adjust the numerical model.
  • in PEST workflow, added option to export sensitivity results to Excel charts.
  • added option to delete a PEST workflow from the model tree.
  • PEST will not run using a numerical model generated from conceptual model boundary conditions that are all steady-state
  • moved log files from …SchlumbergerHGB” to “…SchlumbergerVMODFlex”.
  • PEST, default transformation set to log for Kx and Kz parameters
  • provided an option to view/edit pumping well attributes at the Define Boundary Conditions step in the numerical model workflow.
  • added option to import MT3DMS results, .UCN file
  • added GUI shortcut to Define New Pumping Wells, at the Define Boundary Conditions step in the numerical model workflow.

Defects Addressed

  • constant head BC cells were not being assigned to the correct layer, when using the “Use Surface” option, after converting conceptual model to numerical model
  • fixed project specific issue, converting to numerical model caused error with incorrect Kx calculation
  • could not add particles to a numerical model – project specific
  • pathlines were shifted in the results with rotated grids
  • received error when trying to edit boundary condition cells, if the numerical model originated from a conceptual model.
  • unable to run Sensitivity Analysis in the PEST workflow – project specific
  • error occurred when trying to show a structural zone or property zone in 3D viewer, if geometry was invalid.
  • MODFLOW-LGR was not giving correct results with the SAMG solver.
  • exception occurs during “Edit Grid” step (refine rows/cols), if you set End row to be the last row.
  • error during translation to Finite Element model (project specific)
  • error when closing the 2D viewer if it is in pick/edit mode.
  • error in 2d viewer when showing a corrupted polyline (with only 1 vertex)
  • in some cases, Heads and Drawdown were removed from the model tree, after reloading a previously saved project.
  • the “Project/Save As” option was not working correctly; the MODFLOW packages were not being copied to the new directory.

Known Issues with VMOD Flex

The following issues may occur in Flex under described/applicable conditions. Where available, a workaround is provided.

  • When working with an extracted sub-grid model, whose parent model used a .HDS file as input for starting heads, the initial heads may not be correct. Workaround: extract the heads into surfaces and assign to the appropriate layer(s)
  • Property and boundary condition zones may appear to be incorrect for child grids in 2D- or composite Viewers, particularly for the recharge and evapotranspiration packages. This is caused by the parent grid values being drawn on top of the child grid values in the viewer and parent grid properties are generally null within child grids. Workaround: reorder the layers.
  • In certain cases where grids have previously been generated, the grid refinement buttons in the View Finite Difference Grid step may not work following a subsequent model grid creation. Workaround: ensure that the grid is the active/turned on in the view (sometimes the conductivity grid is activated on top of or instead of the grid itself)
  • At the View Maps step sometimes the 3D view does not display data and legend. Workaround: Use a new 3D window to display data instead.
  • When running a model from a subgrid unable to use initial heads from a previous MODFLOW run option. Workaround: export the results to one or more surfaces and use the surface(s) to assign the initial head values
  • User is unable to select RCH or EVT for edit if another boundary condition is assigned to the cell and is currently turned on for display – user needs to turn off other boundary conditions to be able to select RCH or EVT for edit.
  • When assigning RCH and EVT zones to an unstructured model – each zone is assigned as its own Boundary Condition
  • After importing wells when viewing the Layer View – the Layer combo box becomes disabled (unable to view other layers of model) – user needs to close and reopen the workflow tab and the combo box will become enabled again
  • If the parent node for a boundary condition is selected (to turn on all of the individual boundary conditions) in the model explorer – when user selects Edit – the boundary condition disappears from view. User needs to uncheck the parent node and select the individual boundary conditions in the model explorer.
  • Some boundary conditions (Recharge, Evapotranspiration, and Wells) are not removed from border cells when extracting/creating a subgrid as expected (since they should be replaced with a constant head boundary that takes boundary condition affects into consideration). User must make wells not active or delete them and reassign recharge and evapotranspiration rates to the border cells to be zero so that these effects are not duplicated.
  • PEST: when plotting parameter sensitivity values, if a parameter is log-transformed, the sensitivity is expressed with respect to the log of that parameter. The relative composite sensitivity of a log-transformed parameter is determined by multiplying the composite sensitivity of that parameter by the absolute log of the value of that parameter.
  • Calibration residual map values are approximate and are estimated using a linear interpolation in both time and space. Concentration residuals are estimated using a linear interpolation of log-transformed concentrations. Interpolated values and derived residuals are an approximation only, particularly for output simulation times that do not match an observed time.  Forcing output times that match observation times exactly reduces errors associated with this approximation.
  • If you are importing a Visual MODFLOW Classic project with distributed properties, please be sure the $CND file (and $STR, $IHD) files have been generated in Visual MODFLOW Classic. To do this, open your project in Visual MODFLOW Classic Interface, go to Inputs/Properties. Select Tools/Cell Inspector. Turn on All Flow properties. Then, scroll through each layer in your model. When you are finished, save and close the project, and import into Visual MODFLOW Flex.
  • When displaying a grid that contains a child grid (for LGR), and viewing in the Flex Viewer, the selected row, column, or layer is applied only to the parent grid; it is not applied to the child grid.
  • Some data object style settings are not saved to the project, e.g., points color, symbol size, etc.
  • For some objects 3D viewer does not fully support color rendering/labeling
  • Polygons with holes are not rendered properly in the 2D Viewer; holes in the polygons will appear the same color as the polygon as the polygon(s) they overlap. Holes are not supported in Visual MODFLOW Flex.
  • When draping polygon or polyline over a surface, this is an approximation, since it relies on the vertices of the polygon or polyline to position this in 3D; there will be gaps/locations where it is “poorly” draped where the density of points is low relative to changes in surface elevations. The same problem occurs when viewing areal or linear boundary conditions in 3D Viewer
  • Vertical datum shifts are currently not supported. VMOD Flex assumes that all data you import is in the same vertical datum.
  • Imported 3D Gridded TecPlot (.DAT) data objects cannot be applied to rotated grids
  • In 3D Viewer, child grids may not display correctly if the parent grid only has one layer.
  • In a minority of cases where the user has restricted rights on Windows, an error will occur when starting VMOD Flex due to the TEMP folder being set as read-only. Granting full access to the TEMP folder resolves the issue.
  • If recharge boundaries are defined with a time schedule with multiple time entries for the same date, translation will be treated as static instead of transient.
  • When working with a project in Local Cartesian coordinate system, coordinate conversions are not supported. Please ensure that any data you import is in the same coordinates, and length (XY) units, as your project local coordinates.
  • MODFLOW-USG Issues:
    • In the conceptual model, Property zones defined with the method “Use 3D Gridded Data” is not supported when converting to a USG numerical model
    • Boundary condition attribute method “Use Shapefile Attribute” is not supported when converting to a USG numerical model.
    • Conversion of transient boundary condition objects, with attributes defined at vertices, will show an error.
    • For existing projects, if your conceptual boundary condition has multiple parts, and you edit the attributes, you may face a problem that the “Edit Boundary Condition” GUI does not display the selection correctly (the 2D preview may not show the correct selection) or the attributes grid may be empty. If this is the case, re-create the conceptual boundary condition object.
  • Wall Boundary (HFB) is supported only on MODFLOW-2000 and MODFLOW-2005 models. When doing conceptual to numerical model conversion, only Deformed Grid types are supported.
  • Unsaturated Zone Flow (UZF) package is supported only on MODFLOW-2005 models.
  • MODFLOW-LGR flux visualization, values may not be correct for those cells along the parent/child grid interface
  • MODFLOW-USG translation does not take into account boundary conditions that end at different times;
  • Translate to FEFLOW Model option will not work with the new pumping wells object. Workaround: re-define the pumping wells in FEFLOW
  • SFR segments that are fully contained by a single model cell will not be included in the translated SFR file. Workaround: refine the grid or add one or more dummy vertices outside of the model cell.