Define Modeling Objectives |
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Define Modeling Objectives |
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The first step in defining your conceptual model is to Define the Modeling Objectives, as shown below. Modeling Objectives are divided into two sections:
Visual MODFLOW Flex supports numerous groundwater flow modeling codes (or generalized models) developed by the USGS and others. For the purposes of clarity and to distinguish these generalized models from particular regional and site-specific models that are developed to run with them, these modeling codes are referred to as "engines" within the Visual MODFLOW Flex interface. Each engine was developed to support simulations of groundwater systems with a certain set of conditions, processes, and underlying assumptions, some of which are common to all engines and some of which may only be applicable to one or a subset of engines. Visual MODFLOW Flex currently supports the following engines to facilitate simulations of groundwater systems under a wide variety of conditions:
Engines supported in Visual MODFLOW Flex |
Flow Engine |
Compatible Transport Engine |
Compatible Utilities |
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•MODFLOW-2000 •MODFLOW-2005 •MODFLOW-NWT
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•MT3DMS •RT3D |
•ZONEBUDGET •MODPATH •MOD-PATH3DU5 •PEST |
•MODFLOW-LGR
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•MODFLOW-USG1 |
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•ZONEBUDGET-USG •MOD-PATH3DU5
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•MODFLOW-62 |
•MODFLOW-62 |
•ZONEBUDGET-6
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•MODFLOW-SURFACT3 |
•MODFLOW-SURFACT3 |
•MODPATH
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•SEAWAT4 |
•SEAWAT4 |
•ZONEBUDGET •MODPATH
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Notes: 1 - MODFLOW-USG uses unstructured grids and is supported under a separate workflow process as compared to the standard numerical workflow. 2 - MODFLOW-6 may be configured to run flow and transport simulations in series or within a single coupled simulation. 3 - MODFLOW-SURFACT is a commercial groundwater modeling engine that supports coupled groundwater flow and transport simulations. A demo version of MODFLOW-SURFACT is included with Visual MODFLOW Flex; the full commercial version is sold separately. 4 - SEAWAT is a coupled variable density groundwater flow and transport model 5 - MOD-PATH3DU is a particle-tracking algorithm developed by a collaboration between S.S. Papadopulos & Associates (SSPA) and the University of Waterloo. It is not installed directly with Visual MODFLOW Flex and must be downloaded and installed separately from the mod-PATH3DU website. |
The first step in the workflow for developing and running numerical models in Visual MODFLOW Flex is to define the modeling objectives. This entails selecting the desired flow and transport simulation options. The selected combination of flow options (e.g. saturated groundwater flow) and transport options (e.g. reaction and sorption models) will narrow the list of available flow and transport engines and generate associated input variables (including units and default values). The purpose of this step is to develop the necessary inputs required to build the model based on your understanding of the relevant physical processes present within the study area.
The flow engines supported in Visual MODFLOW Flex are presented in the table below, which provides a preview of what engines are available based on your selected flow and simulation types.
Flow Engines, Grid Types, and Modeling Objectives Supported in Visual MODFLOW Flex |
Flow Type |
Grid Type |
Saturated Flow |
Variably Saturated Flow1 |
Zone Budget |
Particle Tracking |
Transport |
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Simulation |
Structured Grids |
Unstructured Grids |
Constant Density |
Variable Density |
Groundwater |
Vapor Flow |
MODPATH |
MOD-PATH3DU |
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UZF |
V |
BC |
V |
BC |
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Engines |
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MF-2000 |
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MF-2005 |
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MF-62 |
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ZoneBudget-6 |
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MF-6 |
MF-NWT |
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MF-LGR |
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MF-USG2 |
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ZoneBudget-USG |
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SEAWAT |
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SEAWAT |
MF-SURFACT |
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MF-SURFACT |
Notes: 1 - Abbreviations for variably saturated flow processes in the Vadose Zone: UZF = unsaturated zone flow package is based on 1-D unsaturated flow of a diffusion wave pseudo soil V = Van Genuchten relative permeability and saturation relationship BC = Brooks-Corey relative permeability and saturation relationship
2 - MODFLOW-6 and MODFLOW-USG support more modeling objectives than currently available in Visual MODFLOW Flex, these will be added in subsequent releases. In order to help us better prioritize these, please reach out to our support team (support@waterloohydrogeologic.com) to let us know which objectives you'd like added.
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Under Property Settings, you can modify the default flow parameters.
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The MODFLOW-LGR and MODFLOW-USG flow engines do not currently support solute transport. |
The Start Date of the model corresponds to the beginning of the simulation time period. It is important to define a relevant start date since your field measurements (observed heads and pumping schedules) will be defined with absolute (calendar) date measurements, and must lie within the simulation time period.
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The start date will be used to retrieve pumping well and head/concentration observation data for the model run. When you define well data with absolute (calendar) dates, it is important that your start date reflects the actual start time for the model run. Absolute time well data must fall on or after that start date. Otherwise, these data will not be included in the simulation.
Also the start date cannot be changed once it has been set. If you inadvertently set the wrong start date, you can import your pumping well data and observation data in relative times (e.g. starting at 0), and you will see no difference in the numerical model inputs/outputs. |
Visual MODFLOW Flex uses a standard Windows date picker; a few tips are shown below on how to use this. By default, the current date will be set as the Start Date but you are encouraged to set this to an appropriate date for your model simulation.
Click on the button shown below, to load the Windows date picker.
The standard Windows calendar will appear.
Click on the month in the header (as shown below):
All months for the current year will appear as shown below.
Click on the year in the header:
A range of years will then appear as shown below.
Click on the range of years in the header:
A list of years for the previous decade will appear.
You can then use the < or > buttons to change the year.
Once you have reached the desired year (2000 for this example), select this on the calendar as shown below:
A list of months will then appear for that year.
Select January for this example, as shown below.
Finally, select "1" from the calendar as shown below:
The selected date will then appear for the Start Date.
An explanation of the Transport Objectives is available in the section Numerical Model - Define Objectives
Contaminant transport simulation can be enabled and setup in the conceptual model workflow. The species concentrations (for sinks/sources) can be defined while you define your conceptual boundary conditions. However, the transport properties (initial concentrations, dispersion, etc.), are defined in the Numerical Model workflow, after you have defined a grid, and completed the "Convert to Numerical Model" step. This is explained in the section Define Properties (Numerical Model)
•Click 
(Next Step) to proceed.
Page url:http://www.waterloohydrogeologic.com/help/vmod-flex/index.html?vm_define_objectives.htm
