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    What's New in Visual MODFLOW v4.2?

    Visual MODFLOW Interface

    Building the Visual MODFLOW Model - The Input Module

    Running a Visual MODFLOW Simulation - The Run Module

    Calibrating a Visual MODFLOW Model

    Display and Interpret the Visual MODFLOW Results - The Output Module

    MODFLOW-SURFACT

    Minimum System Requirements

What's New in Visual MODFLOW v4.2?

MIKE 11, developed by DHI, is a world-recognized surface water modeling package designed for simulating the hydrodynamic conditions found in rivers, lakes, reservoirs, and irrigation canals. Visual MODFLOW Premium v4.2 and MIKE 11 are now available as a fully coupled, groundwater and surface water simulation environment. This combination is ideally suited for:

• Analyzing the hydraulic connection between rivers, streams, and aquifer systems
• Determining groundwater base-flow and potential impacts to ecologically sensitive areas
• Calculating infiltration rates from surface water to groundwater during rainfall event
• Developing comprehensive watershed management plans

Link directly to PHT3D multi-component transport models, for advanced three-dimensional reactive transport in saturated, porous media. Ideally suited for:

• Assessing water-rock interaction during aquifer storage and recovery projects
• Addressing acid-mine drainage and metal contamination problems in groundwater
• Simulating transport, attenuation and nitrification of ammonium-contaminated groundwater
• Optimizing groundwater remediation through in-situ reactive zones/wells

The multi-species contaminant transport engine RT3D, for reactive transport simulations can now simulate zeroth-order decay or production. This feature can also conveniently provide a direct simulation of groundwater ages or calculation of parameter sensitivities.

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Visual MODFLOW Interface

The Visual MODFLOW interface has been specifically designed to increase modeling productivity and decrease the complexities typically associated with building three-dimensional groundwater flow and contaminant transport models. The interface is divided into three separate modules, the Input Module, the Run Module, and the Output Module. When you open or create a file, you will be able to seamlessly switch between these modules to build or modify the model input parameters, run the simulations, and display the results (in plan view or full-screen cross section). Each module of the Visual MODFLOW interface has the same basic screen layout as shown in the figure below.

The ability to quickly and easily switch between plan view and cross-section display of the model is a powerful feature of Visual MODFLOW that allows the user to gain a better perspective on the three-dimensional aspects of the model input parameters and simulation results. The display control buttons have the same function for each module and are located in the same location for each module. Simply select the desired display button and then click on the row, column or layer you would like to view.

The Navigator Cube provides a 3-D schematic representation of the model grid and layers. This navigator cube gives a quick visual reference of your active position within the model domain. This is particularly useful when you are dealing with multilayer models or if you are viewing a model in cross section. In addition, the active mouse location (X,Y,Z model coordinates and I, J, K grid coordinates) are interactively displayed below the Navigator Cube as you move the mouse around the screen.

Each menu screen of the Visual MODFLOW interface has a set of shortcut buttons located along the bottom of the screen. These buttons allow the user to quickly access some of the more common graphical functions such as zooming in or zooming out, panning the display in any direction, adding or removing overlay displays, saving the existing data file, and returning to the Main Menu.

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Building the Visual MODFLOW Model - The Input Module

The process of building the input data file for a groundwater flow and/or transport model is often the most time-intensive and tedious task associated with groundwater modeling projects. The logical structure and layout of the Visual MODFLOW interface eliminates these difficulties by guiding the user through the sequence of steps necessary to build a groundwater flow and contaminant transport model. Once you start using Visual MODFLOW, you will immediately realize the benefits of easily switching between plan view and cross-sectional view at any time. In addition, the many powerful and easy-to-use graphical tools give you all the flexibility you need to assign complex property distributions, multiple pumping wells and steady-state or transient boundary conditions. The following section describes the sequence of Visual MODFLOW input screens and model building tools which are provided for creating your model input data.

Visual MODFLOW allows you to rotate the model domain over the site map (.DXF or .BMP format) to align the model grid with the site characteristics and groundwater flow direction. The finite difference grid can be modified by adding, deleting, moving and automatically refining rows, columns and layers using standard 'point-and-click' methods.

A poorly designed grid can cause numeric instability and may lead to non-convergence of the model solution. Therefore, it is important to design the model grid with proper grid spacing to give you the level detail you need in important regions of the model and still maintain the numerical stability you need for the solution to converge. Automatic grid smoothing is used to identify and fix regions of the grid which are poorly designed and optimize (smooth) the transition from small grid spacing to large grid spacing.

Since most aquifers are not ``flat" layers, Visual MODFLOW allows you to import layer surface data from ASCII (X,Y,Z) text files or SURFER (.GRD) files. It even has a built-in check to prevent layer surfaces from intersecting each other. The layer surface elevations and thicknesses can be visualized using plan view contours or by viewing the model grid in cross section.

A new feature in the latest version of Visual MODFLOW is the grid cell elevation editor. This tool allows you to modify the individual elevations of each cell using an array editor to modify the elevation value. The cell elevations can also be modified in cross section using 'drag-and-drop' methods to stretch or compress a cell thickness.

Pumping wells or injection wells can be added, deleted, copied or moved using the intuitive well edit tools that allow you to graphically delineate the well screen interval and enter or import real-time pumping schedules from an ASCII text file. For sites with many pumping wells, Visual MODFLOW can also import all relevant pumping well data. Multiple well screens for a single well are easily accommodated while the pumping rate distribution between layers is automatically calculated based on the transmissivity of the layers through which it is screened. The well details and pumping schedule can be readily accessed and changed at any time. Observed head at the well can be adjusted according to the position of the well within the grid cell and radius of the well.

Visual MODFLOW defines a model property as a physical or chemical attribute of the model that remains static throughout the entire simulation. Visual MODFLOW separates the model properties into two distinct categories.

1. Flow Properties:

Those physical model properties affecting the groundwater flow simulation. Flow properties include: hydraulic conductivity (Kx, Ky, and Kz), specific storage (Ss), specific yield (Sy), porosity and initial heads. Each of these flow properties must be defined for each cell in the model domain.

2. Transport Properties

Those physical and chemical model properties affecting the fate and migration of a contaminant plume in groundwater. Transport properties include dispersion (Dx, Dy and Dz), bulk density, distribution coefficient (Kd), decay constants, and initial concentrations. All model properties are assigned to individual grid cells or to zones of grid cells by either painting single cells, delineating polygons, or stretching a window around the selected grid regions. Each different property zone is color-coded to visually differentiate it. Visual MODFLOW also has many time-saving tools that allow you to copy the property distribution from a single layer to any other layer(s) to eliminate repetitive steps involved in developing the model input files. Individual property values and property zones can be edited at any time using the property database to make global modifications.

For complex stratigraphy and varying hydraulic conductivity, it is important to be able to display and modify the model property distributions in plan view and cross section to gain a proper perspective on the geologic characteristics of the site. Visual MODFLOW is the only modeling environment that provides an active cross-sectional view allowing you to edit and modify cell properties.

MODFLOW boundary conditions supported by Visual MODFLOW include both steady-state and transient Constant Heads, Rivers, General Heads, Drains, Recharge and Evapotranspiration. The Horizontal Flow Barrier package is also supported. Visual MODFLOW also supports all contaminant transport boundary conditions available for the latest versions of MT3D (including MT3D99 for cell-by-cell mass budgets, MT3DMS for multispecies transport, and RT3D for reactive transport and natural attenuation simulations). MT3D99, the latest commercial version of MT3D, is also fully supported. Each type of boundary condition has a specific color code to differentiate them from one another. The convenient graphical tools allow you to assign these boundaries as either single cells, a polyline of cells with automatic interpolation of values, a polygon of cells, or a rectangular window of cells. For transient simulations, real-time schedules of boundary condition values can be entered directly or imported into the time schedule from an ASCII text file.

Forward or backward tracking particles can be easily assigned for determining advective transport, preferred flow pathways and delineating well capture zones. Visual MODFLOW's intuitive graphical tools allow you to easily assign single particles, lines of particles and a circle of particles anywhere in your model domain. These particles can be easily toggled from forward to backward tracking with the click of the mouse. For transient simulations, the release times for the particles can also be assigned to groups of particles or individually to single particles or groups of particles. This is particularly useful for demonstrating how the flow system and directions of flow change with time during varying pumping schedules or flow variation due to seasonal influences.

The Zone Budget package allows you to produce zone-to-zone flow summaries for regions of interest in your model domain. This can be used to estimate flow contributions to a well from specific layers in your model or to predict groundwater discharge to specific sections along a river. Visual MODFLOW allows you to assign zones by painting single cells, delineating polygons or by stretching a window across the selected cells in the zone. Each zone is color coded to differentiate the various zones throughout the model domain. These zones can be copied to other layers in the model to save time and avoid unnecessary repetition.

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Running a Visual MODFLOW Simulation - The Run Module

The Visual MODFLOW Run Module allows the user to select and modify the various MODFLOWP, MODPATH and MT3D run-time options and start the model calculations using the Win32 MODFLOW Suite directly from within the Visual MODFLOW modeling environment.

Visual MODFLOW allows you to customize the various MODFLOW run settings including:

• Initial head estimates (import from ASCII or Surfer)
• Number of timesteps and timestep multiplier
• Solver selection and convergence settings
• Recharge layer settings
• Layer types (e.g. confined, unconfined)
• Rewetting options
• Anisotropy option

Visual MODFLOW now allows you to maintain a minimum saturated thickness for dry cells and to specify a head value in these cells equivalent to the cell bottom elevation. This enables you to run WinPEST on models even when dry cells are occurring. MT3D run settings include:

• Initial concentrations (import from ASCII or Surfer)
• Advection package settings (FD, MOC, MMOC, HMOC)
• Simulation ouput times

For the advanced users of MODFLOW, you can substitute your own manually created input data files for any MODFLOW files by using the Advanced Settings. The Advanced Settings feature allows you to specify which files you will use from Visual MODFLOW and which files you will substitute.

Visual MODFLOW also now allows you to easily set up a batch file to run several models in succession. This is a very powerful feature that allows you to create several versions of the same model and then run the models while you are doing other tasks.

Visual MODFLOW includes the Win32 MODFLOW Suite with MODFLOW-96, MODPATH, Zone Budget, MT3DMS and RT3D compiled to run as true Windows 32-Bit applications. This unique and powerful modeling utility actually provides you with the ability to control the numerical solution process by manipulating the solver parameters and convergence criteria while the solution is in progress. In addition, it provides a real-time graphical display of the solution convergence data and a detailed graphical summary of the Zone Budget results. After each successful run has completed, the Win32 MODFLOW Suite automatically produces all of the necessary files required for you to analyze and interpret the results, and to produce full-color, report-quality graphical presentations using Visual MODFLOW's postprocessing graphical features. Visual MODFLOW is the only modeling software package that provides a truly seamless integration with 32-Bit Windows versions of MODFLOW, MODPATH, MT3D, Zone Budget and RT3D.

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Calibrating a Visual MODFLOW Model

Visual MODFLOW comes with an extensive selection of built-in model calibration plots and statistical summaries to give you all the interpretation capabilities you need to properly and thoroughly analyze the model calibration data. All of the calibration plots are fully customizable in terms of axis scaling, titles, legends, fonts, and colors. In addition, Visual MODFLOW now fully supports automated calibration using WinPEST, the only true Windows version of PEST.

Visual MODFLOW provides a scatter plot of calculated vs. observed values of heads or concentrations for the flow and contaminant transport models, respectively. This plot can be used to examine all calibration targets from the entire model domain or it can be used to examine specified groups of observation points relating to certain sections of the model. The ability to select predefined groups of observation points is particularly useful for large, complex groundwater models involving several different aquifer systems. Calibration statistics are also displayed with the graph and are updated according to the data displayed on the scatter plot. Calibration statistics include:

• Mean Error
• Absolute Mean Error
• Standard Deviation
• Root Mean Square of the Error
• Normalized Root Mean Square of the Error

The 95% confidence interval is indicated on the calculated vs. observed plot. The calibration data located within this interval can be expected to provide correct results 95% of the time.

The calibration residuals histogram plots the normalized population of the observations vs. the interval range of normalized residual values. This plot is compared to a Student t distribution and is used to: (i) assess the quality of the fit between the calculated and observed data and (ii) identify any positive or negative bias in the calibration data.

For transient simulations, Visual MODFLOW creates temporal plots of calculated and observed heads, drawdown or concentrations at any observation point in the model domain. Temporal plots of calibration statistics can also be created to determine the quality of the model calibration throughout the simulation.

Visual MODFLOW is the only modeling environment that provides a truly seamless integration with WinPEST for selecting the model parameters, setting the WinPEST controls, and launching the WinPEST simulation. Once the WinPEST simulations have started, you will continue to have full control over the optimization process. The run-time graphical reporting of the WinPEST data lets you know how the optimization procedure is progressing and you can pause the procedure to modify the settings at any time. Furthermore, Visual MODFLOW is in constant communication with WinPEST, whereby every time WinPEST modifies a parameter value, it is automatically updated in the Visual MODFLOW data files as well. This is a very important step that other modeling software programs do not incorporate. If this step is missing, it becomes very difficult to reload the calibrated model data files. After the WinPEST optimization procedure is completed, the calibrated model data files can be easily loaded back into Visual MODFLOW for graphical display of the simulation results or for further modifications and fine-tuning. In addition, WinPEST produces a graphical interpretation of the analytical optimization data.

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Display and Interpret the Visual MODFLOW Results - The Output Module

The ability to visualize the simulation results is almost as important as creating the model in the first place. In order to get the most out of the model that you build, it is critical that you have the tools necessary to properly analyze and interpret the results. The Visual MODFLOW Output Module automatically reads the results files from each successful simulation and provides a comprehensive selection of graphical formats for displaying full-color results in plan view and cross-sectional views.

The contouring menu selection allows you to contour the results of the modeling simulation in plan view or cross section. The contouring selections are as follows: Heads, Drawdown, MT3D concentrations, Water table elevations, Head difference between layers, Flux between layers, Layer elevations (top, bottom and thickness), and Net recharge.

Visual MODFLOW accommodates multiple contour overlays to be able to compare several types of plots together. Color shading is also available for high-impact presentation of all contoured results. The contouring options button along the left-hand menu bar allows you to adjust the maximum, minimum, and interval of the contour lines, assign customized contour levels, adjust the speed/resolution of the contouring, change the color of the contour lines, and produce color fills of contours.

The right mouse button can also be used to activate contour options that allow you to add, move or delete contour labels, or add a contour line at any location by pointing and clicking. For transient simulations, Visual MODFLOW allows you to advance to successive output times or to manually select the desired output time from a list of available time steps.

The flow velocity vectors provide an important representation of the groundwater flow direction within a particular layer, row or column. Each velocity vector is color coded to indicate whether it is flowing up or down relative to the plane being displayed. Display options include setting the number of velocity vectors per line, adjusting the scale, and toggling between simple direction vectors or magnitude vectors.

The flow pathlines provide an important representation of the flow direction and the path that the groundwater will follow from a specific location. Backwards particle tracking can also be used to indicate where the groundwater is coming from. Display options include viewing all pathlines as a projection through the entire model, viewing only those pathlines that start in the current layer, or viewing only the pathline segments which occur in the current layer. Time-related pathlines and time markers can also be displayed, and individual pathlines or groups of pathlines can be toggled on or off using the mouse.

Visual MODFLOW provides a detailed summary of the mass balance results and zone-to-zone flow exchanges. These mass balance results provide important information on the quality and reliability of the groundwater model you have built. If you do not achieve a reasonable mass balance between the flow entering the system and the flow leaving the system, your model will not yield reliable results. The mass balance results are summarized according to flow contributions from each type of boundary condition and can be used to identify regions where there are unreasonable flux rates. For a more localized summary of zone-to-zone flow exchanges, Visual MODFLOW uses Zone Budget to provide a detailed summary of the inflows and outflows from specified zones throughout the model domain.

Visual MODFLOW prints full-color, high-resolution graphics to any printer or plotter supported by Windows 95/98/NT. The graphical display of the simulation results and/or input files can be printed in portrait or landscape format as a full page image or with a title block that describes the details of the model and the results being displayed. Color-shaded contours can be printed with or without a color legend. For all X-Y graphs, the WYSIWYG print preview and page design features allow you to customize the page design and import bitmap logos for display on the printed page. Visual MODFLOW also exports the on-screen display to several graphics file formats including AutoCAD (dxf), Enhanced Windows Metafile (emf) and ESRI shape files (shp). Data files of the results can also be exported to 2-D or 3-D ASCII data files for use in virtually any 3-D visualization software product.

Visual MODFLOW project files can be visualized and animated in 3-D using the built-in Visual MODFLOW 3-D Explorer. All input parameters and modeling results are read into the Visual MODFLOW 3-D Explorer and displayed using color-shaded contouring on slices, multiple 3-D isosurfaces, and 3-D pathlines.

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MODFLOW-SURFACT

MODFLOW-SURFACT is a robust 3D finite-difference flow and transport program that contains several improvements over the public-domain versions of MODFLOW. Using advanced solution methods and enhanced simulation capabilities for handling complex variably-saturated flow and transport processes, MODFLOW-SURFACT is designed to overcome the many limitations of standard MODFLOW codes. MODFLOW-SURFACT can be used when you have:

• Multiple water tables or perched aquifers
• Steep flow gradients crossing several layers
• Over-pumped wells screened across multiple layers
• Analyzing infiltration through the vadose zone to the water table
• Significant water table fluctuations causing drying/wetting of grid cells
• Vapor flow through the unsaturated zone

Advanced Flow Capabilities:

• Variably-saturated flow
• Unsaturated vapor flow
• Adaptive time-stepping
• Solver incorporates Newton-Raphson linearization

Advanced Transport Capabilities:

• Multi-phase, multi-component solute transport
• Advective-dispersive transport incorporating both linear and nonlinear retardation options
• Biochemical degradation and first-order decay in both the water and soil matrix
• Dual-porosity options for aggregated or fractured systems
• NAPL phase partitioning into air and water phases

Integration into Visual MODFLOW Pro and Premium Visual MODFLOW Pro and Premium provide seamless graphical interfaces to MODFLOW-SURFACT in order to take advantage of MODFLOW-SURFACT's advanced features while maintaining the feature-rich GUI, 3D graphics, and animation tools within the Visual MODFLOW Pro and Premium environments.

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Minimum System Requirements

• Pentium II 300 MHz
• Windows 2000/XP (Service Pack 3)
• 128 Mb RAM
• 800x600 w/ Hi-color (min.)
• 100 Mb Disk Space

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