Visual MODFLOW Flex includes significant upgrades to the PEST workflow:

•Workflow Steps: The PEST workflow includes a number of new and improved workflow steps:

oDefine Observations: add flux observations and improved usability for assigning observation groups, observations, and weights

oDefine Property Parameters: add recharge (RCH), evapotranspiration (EVT), and unsaturated zone flow (UZF) property parameters to the PEST run

oDefine Kriging Variograms: an optional new setting that allows PEST utilities to automatically calculate the kriging variograms based on the density of pilot points

oSelect PEST Variant: you can select which variant of PEST to use (PEST v17.5, PEST_HP),

oPEST Control settings: define/edit settings for the PEST run including for the Objective Function, Parameter Updates, Iterations, Marquardt Lamda, Singular Value Decomposition, etc.

oParameter 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:

oPilot point interpolation makes use of the PLPROC utility for improved performance and clarity of the script files

oOptional 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 Ramps: objects with distributed values such as surfaces, model properties, boundary conditions, and model outputs, can be rendered using predefined or custom color ramps

odefine a list of custom, linearly distributed, logarithmically distributed, or custom values and associated colors

oselect from a list of of predefined, custom, or imported color ramps

oyou can include hard breaks/color stops in a ramp to render an abrupt breaks in the color fill when values cross a specified threshold (e.g. positive/negative or above/below a regulatory limit)

•Manage Color Ramps:

oVisual MODFLOW Flex includes over a dozen predefined color ramps or you can create your own custom color ramp

oYou can import color ramps using the color map (.clr) file format supported in other applications such as QGIS, ArcPro, and Surfer

oThe 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

•MAW and MWT Package Support: Support for the multi-aquifer well (MAW) and multi-aquifer well transport (MWT) packages in MODFLOW-6 models.

oCreate or import MAW/MWT wells

oDynamically switch between supported well models (WEL/MNW1/MNW2/MAW)

oImport 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 models

•Performance Enhancements:

oAssigning time steps to models with many stress periods

oModel translation for MODFLOW-6 models with many stress periods

oConverting a conceptual model to an unstructured Q-grid model with many cells

oApplying/saving changes to model properties for an unstructured grid model with many cells

•The following features can be exported from Visual MODFLOW Flex:

omodel outputs including heads, concentrations, and drawdowns as contours for unstructured grid models (MODFLOW-6 and MODFLOW-USG)

oboundary conditions as points or polygons for unstructured grids

ocalibration dashboard charts as images

•SAMG solver:

oUpdated versions of the SAMG solver for the MODFLOW-USG and MODFLOW-6 engines

oAvailable in the Pro (serial-SAMG) and Premium (multi-core-SAMG)

oNew 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

•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

•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:

oCreate new Object window

oRun Tabs are clipped

oLabels 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