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| {{MODFLOW Links}} | | {{MODFLOW Links}} |
| Once the MODFLOW simulation has been initialized, the next step is to enter the data required by the Global Options/Basic package. This includes data defining fundamental program options such as the computational time intervals (stress periods), an array defining which cells are inactive and which cells have constant heads, an array of starting head values for a transient simulation, and a set of flags defining which of the other packages are to be used. The input data for this package should be entered before editing any of the other packages. The MODFLOW ''Global Options/Basic Package'' dialog is accessed through the '''Global Options''' command in the ''MODFLOW'' menu. The options in the dialog are as follows: | | Once the MODFLOW simulation has been initialized, the next step is to enter the data required by the Global Options/Basic package. This includes data defining fundamental program options such as the computational time intervals (stress periods), an array defining which cells are inactive and which cells have constant heads, an array of starting head values for a transient simulation, and a set of flags defining which of the other packages are to be used. The input data for this package should be entered before editing any of the other packages. The MODFLOW ''Global Options/Basic Package'' dialog is accessed through the '''Global Options''' command in the ''MODFLOW'' menu. |
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| === Headings ===
| | The options in the dialog are as follows: |
| [[File:MODFLOWglobaloptions.jpg|thumb|310 px|The ''MODFLOW Global / Basic Package'' dialog.]] | | |
| | == Headings == |
| | [[File:MODFLOWglobaloptions.png|thumb|310 px|The ''MODFLOW Global / Basic Package'' dialog.]] |
| The two headings are optional text strings which are written to the MODFLOW text output file. | | The two headings are optional text strings which are written to the MODFLOW text output file. |
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| === Version ===
| | == Version == |
| The MODFLOW version can be specified with the choices being (as of July 2013): | | The MODFLOW version can be specified with the choices being (as of Apr 2014): |
| *MODFLOW-2000 | | *MODFLOW-2000 |
| *MODFLOW-2005 | | *MODFLOW-2005 |
| *MODFLOW-NWT | | *MODFLOW-NWT |
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| The following choices will soon be added to the list:
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| *MODFLOW-LGR | | *MODFLOW-LGR |
| *MODFLOW-USG | | *MODFLOW-USG |
| | *MODFLOW-USG Transport |
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| | The type of binary executable can be specified using one or more of the following choices: |
| | *Double precision – Uses 8 bytes rather than 4 bytes to store the number so they are more precise but calculations may take longer and binary files that store double-precision variables will be bigger than if single-precision had bee used. |
| | *Parallel – Enables parallel processing capabilities. |
| | *64 bit – Process using 64 bytes to store the number. |
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| Additionally, the type of binary executable can be specified using one or more of the following choices:
| | The ''Save native text copy'' option will save native ascii MODFLOW input files when the project is saved. An additional folder named ''myProject''_MODFLOW_text is created that contains these files. |
| *Double precision
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| *Parallel
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| *64 bit
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| === Run Options ===
| | The ''Use custom Run dialog'' option will bring up the [[GMS:Custom Run MODFLOW|''Custom Run MODFLOW'']] dialog when the ''MODFLOW'' | '''Run MODFLOW''' menu command is selected. |
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| | The '''Set as Default''' button will set the selected model run options as the default MODFLOW model run options for GMS. |
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| | == Run Options == |
| The run options are not part of the actual MODFLOW input files, but present different ways that MODFLOW 2000 can be run from GMS. | | The run options are not part of the actual MODFLOW input files, but present different ways that MODFLOW 2000 can be run from GMS. |
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| ===== Forward Run =====
| | *''Forward Run'' |
| :A forward run is a normal MODFLOW simulation. If parameters have been defined for either a stochastic or parameter estimation run, the mean or starting values of the parameters are used for the forward run. | | *:A ''Forward'' run is a normal MODFLOW simulation. If parameters have been defined for either a stochastic or parameter estimation run, the mean or starting values of the parameters are used for the forward run. |
| | *''Parameter Estimation'' |
| | *: |
| | <!--*'' Sensitivity Analysis'' |
| | *:The ''Sensitivity Analysis'' option is used to perform a sensitivity analysis on a set of selected parameters. The results can be presented with a set of plots or by contouring datasets representing grid sensitivities. This option is only available with the [[GMS:MODFLOW Packages Supported in GMS|LPF and HUF flow packages]]. This option is not available in GMS 6.5 and later (see [[GMS:MODFLOW_with_HDF5#Parameters|MODFLOW with HDF5]]). |
| | *:After running PEST, sensitivities are displayed in the *.sen file. Click [[GMS:Automated Parameter Estimation#Sensitivity Analysis|here]] for more information. |
| | *'' Parameter Estimation''--> |
| | *:In the ''Parameter Estimation'' mode, a set of parameters is found that minimizes the residual between observed and simulated heads and flows. These options are described in more detail on the [[GMS:Automated Parameter Estimation|Automated Parameter Estimation]] page. This option is only available with the [[GMS:MODFLOW Packages Supported in GMS|LPF and HUF flow packages]]. |
| | *'' Stochastic Simulation '' |
| | *:The ''Stochastic Simulation'' option is used to perform a stochastic simulation using the [[GMS:Stochastic Modeling#Using Parameter Zonation With Stochastic Modeling|Monte Carlo]] or [[GMS:Stochastic Modeling#Using Parameter Zonation With Stochastic Modeling|Latin Hypercube]] methods for randomizing a selected set of parameters. Stochastic simulations can also be performed using a material set approach (indicator simulations). A risk analysis wizard can be used to analyze the results for a probabilistic threshold analysis or a probabilistic capture zone delineation. These options are described in more detail on the stochastic simulation page. |
| | * ''Stochastic Inverse Model'' |
| | *:If the ''Material Set'' option is used for stochastic simulations, the ''Stochastic Inverse'' option can be used to perform automated parameter estimation on each of the N candidate model instances in the stochastic. The weighted RMS errors for each of the resulting optimized solutions can be used to weight the computations performed by the risk analysis wizard. This option is only available with the [[GMS:MODFLOW Packages Supported in GMS|LPF and HUF flow packages]]. |
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| ===== Sensitivity Analysis ===== | | == Model Type == |
| :The sensitivity analysis option is used to perform a sensitivity analysis on a set of selected parameters. The results can be presented with a set of plots or by contouring datasets representing grid sensitivities. This option is only available with the [[GMS:MODFLOW Packages Supported in GMS|LPF and HUF flow packages]]. This option is not available in GMS 6.5 and later (see [[GMS:MODFLOW_with_HDF5#Parameters|MODFLOW with HDF5]]).
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| :After running PEST, sensitivities are displayed in the .sen file. Click [[GMS:Automated Parameter Estimation#Sensitivity Analysis|here]] for more information.
| | The simulation can be designated as either ''Steady state'' or ''Transient''. If a steady state simulation is specified, certain portions of the MODFLOW interface such as the ''Stress Period'' dialog are inactivated since they are not relevant. |
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| ===== Parameter Estimation ===== | | == No Flow Head (HNOFLO) == |
| :In the parameter estimation mode, a set of parameters is found that minimizes the residual between observed and simulated heads and flows. These options are described in more detail on the [[GMS:Automated Parameter Estimation|Automated Parameter Estimation]] page. This option is only available with the [[GMS:MODFLOW Packages Supported in GMS|LPF and HUF flow packages]].
| | This is the value of head to be assigned to all inactive (no flow) cells (IBOUND=0) throughout the simulation. |
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| ===== Stochastic Simulation =====
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| :The stochastic simulation option is used to perform a stochastic simulation using the [[GMS:Stochastic Modeling#Using Parameter Zonation With Stochastic Modeling|Monte Carlo]] or [[GMS:Stochastic Modeling#Using Parameter Zonation With Stochastic Modeling|Latin Hypercube]] methods for randomizing a selected set of parameters. Stochastic simulations can also be performed using a material set approach (indicator simulations). A risk analysis wizard can be used to analyze the results for a probabilistic threshold analysis or a probabilistic capture zone delineation. These options are described in more detail on the stochastic simulation page.
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| ===== Stochastic Inverse Model ===== | | == Stress Periods == |
| :If the material set option is used for stochastic simulations, the "stochastic inverse" option can be used to perform automated parameter estimation on each of the N candidate model instances in the stochastic. The weighted RMS errors for each of the resulting optimized solutions can be used to weight the computations performed by the risk analysis wizard. This option is only available with the [[GMS:MODFLOW Packages Supported in GMS|LPF and HUF flow packages]].
| | The '''Stress Periods''' button is used to bring up the [[GMS:Stress Periods|''Stress Period'' dialog]]. The stress periods should be defined before any of the sources/sinks are entered. If the steady state option is selected, the '''Stress Periods''' button is dimmed. |
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| === Model Type === | | == Packages == |
| | The '''Packages''' button brings up the [[GMS:MODFLOW Packages Supported in GMS|''Packages'' dialog]]. |
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| The simulation can be designated as either steady state or transient. If a steady state simulation is specified, certain portions of the MODFLOW interface such as the ''Stress Period'' dialog are inactivated since they are not relevant. | | == Units == |
| | The '''Units''' button the ''Basic Package'' dialog brings up the [[GMS:Units|''Units'' dialog]]. |
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| === No Flow Head === | | == IBOUND == |
| This is the value of head to be assigned to all inactive (no flow) cells (IBOUND=0) throughout the simulation.
| | The '''IBOUND''' button of the [[GMS:Global Options/Basic Package|''Global Options\Basic Package'']] dialog brings up the [[GMS:MODFLOW Array Editor|''Array Editor'']]. The IBOUND array contains a value for each cell in the grid defining the type of the cell as constant head, inactive, or variable head. |
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| === Stress Periods ===
| | * Constant Head |
| The Stress Periods button is used to bring up the [[GMS:Stress Periods|''Stress Period'' dialog]]. The stress periods should be defined before any of the sources/sinks are entered. If the steady state option is selected, the '''Stress Periods''' button is dimmed. | | *:A negative value indicates that the cell has a constant head. The value of the constant head is defined in the starting heads array. |
| | * Inactive |
| | *:An IBOUND value of zero indicates that the cell is inactive (no-flow). |
| | * Variable Head |
| | *:A positive IBOUND value indicates that the cell has a variable head (i.e., the head value will be computed as part of the simulation). |
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| === Packages === | | === Editing the IBOUND Array === |
| The Packages button brings up the [[GMS:MODFLOW Packages Supported in GMS|''Packages'' dialog]].
| | There are several ways to change the active/inactive status (positive vs. zero) of a cell before or after initializing the IBOUND array. One method is to directly edit the IBOUND array using the ''IBOUND'' dialog. Another method is to select the '''Cell Attributes''' command in the ''MODFLOW'' menu. In most cases, the most efficient method is to use the [[GMS:Activate Cells in Coverage|'''Activate Cells in Coverage''']] command in the [[GMS:Map Module|Map module]]. This method uses a polygon to define the active and inactive regions. |
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| === Units ===
| | The constant head cells are typically assigned or edited in one of three ways. One method is to directly edit the IBOUND array. Another method is to select a set of cells and use the [[GMS:Cell Properties|''Cell Properties'']] dialog in the ''MODFLOW'' menu. The simplest method is to define the constant head zones using feature objects as part of a [[GMS:MODFLOW Conceptual Model Approach|conceptual model]] in the [[GMS:Map Module|Map module]]. |
| The Units button the ''Basic Package'' dialog brings up the [[GMS:Units|''Units'' dialog]]. | |
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| === IBOUND === | | == Starting Heads == |
| ==== Values ====
| | The starting head values are used as initial conditions for head for both steady state and transient simulations. The '''Starting Heads''' button on the left side of the ''Basic Package'' dialog is used to enter the values of the starting heads array. Selecting the '''Starting Heads''' button brings up the [[GMS:MODFLOW Array Editor|MODFLOW Array Editor]]. |
| The IBOUND button of the [[GMS:Global Options/Basic Package|''Global Options\Basic Package'']] dialog brings up the [[GMS:MODFLOW Array Editor|array editor]]. The IBOUND array contains a value for each cell in the grid defining the type of the cell as constant head, inactive, or variable head. | |
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| ===== Constant Head ===== | | == Force Convergence (CONVERGE) == |
| :A negative value indicates that the cell has a constant head. The value of the constant head is defined in the starting heads array.
| | Forces converging. |
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| ===== Inactive ===== | | == Top Elevation == |
| :An IBOUND value of zero indicates that the cell is inactive (no-flow). | | The '''Top Elevation''' button brings up an [[GMS:MODFLOW Array Editor|''Array Editor'']] that allows editing of the top elevation of each layer. GMS requires that the top and bottom elevations for adjacent layers be the same. This means that when editing the bottom of one layer, move down to the next layer, and edit the top of that layer, the bottom of the previous layer will also be changed. Note that the top and bottom layer elevations must be entered regardless of the which layer data package (BCF, LPF, HUF) is chosen even though these values may not be used because of certain package options. |
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| ===== Variable Head ===== | | == Bottom Elevation == |
| :A positive IBOUND value indicates that the cell has a variable head (i.e., the head value will be computed as part of the simulation). | | The '''Bottom Elevation''' button brings up an [[GMS:MODFLOW Array Editor|''Array Editor'']] that allows editing the bottom elevation of each layer. Note that the top and bottom layer elevations must be entered regardless of the which layer data package (BCF, LPF, HUF) is chosen even though these values may not be used because of certain package options. |
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| ==== Editing the IBOUND Array ====
| | [[File:LayerConfiningBed.png|thumb|200 px|The ''Layer Confining Bed'' dialog.]] |
| There are several ways to change the active/inactive status (positive vs. zero) of a cell before or after initializing the IBOUND array. One method is to directly edit the IBOUND array using the ''IBOUND'' dialog. Another method is to select the '''''Cell Attributes''''' command in the ''MODFLOW'' menu. In most cases, the most efficient method is to use the [[GMS:Activate Cells in Coverage|'''''Activate Cells in Coverage''''']] command in the [[GMS:Map Module|Map module]]. This method uses a polygon to define the active and inactive regions.
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| The constant head cells are typically assigned or edited in one of three ways. One method is to directly edit the IBOUND array. Another method is to select a set of cells and use the [[GMS:Cell Properties|''Cell Properties'']] dialog in the ''MODFLOW'' menu. The simplest method is to define the constant head zones using feature objects as part of a [[GMS:MODFLOW Conceptual Model Approach|conceptual model]] in the [[GMS:Map Module|Map module]]. | | == Confining Beds== |
| | The ''Layer Confining Beds'' dialog, accessed from the ''Global Options/Basic Package'' dialog, allows selecting which layers will have a confining bed below them. The last layer in the grid may not have a confining bed. |
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| === Starting Heads ===
| | Confining beds are most common in older models where the user was trying to conserve memory in solving the groundwater model. In general, it is recommended that users explicitly model all of the layers in the system instead of using confining beds. This feature is supported in GMS to make it possible for users to read in older models. |
| The starting head values are used as initial conditions for head for both steady state and transient simulations. The '''Starting Heads''' button on the left side of the ''Basic Package'' dialog is used to enter the values of the starting heads array. Selecting the '''Starting Heads''' button brings up the [[GMS:MODFLOW Array Editor|MODFLOW Array Editor]].
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| === Top Elevation ===
| | In the spreadsheet, the user may turn on the confining bed option for any of the layers except the last layer in the grid. |
| The '''Top Elevation''' button brings up an [[GMS:MODFLOW Array Editor|array editor]] that allows you to edit the top elevation of each layer. GMS requires that the top and bottom elevations for adjacent layers be the same. This means that when you edit the bottom of one layer, move down to the next layer, and edit the top of that layer, the bottom of the previous layer will also be changed. Note that the top and bottom layer elevations must be entered regardless of the which layer data package (BCF, LPF, HUF) is chosen even though these values may not be used because of certain package options.
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| === Bottom Elevation ===
| | The '''Confining Bed Elevations''' button brings up the [[GMS:MODFLOW Array Editor|''Array Editor'']] that allows the user to edit the elevation of each layer. |
| The '''Bottom Elevation''' button brings up an [[GMS:MODFLOW Array Editor|array editor]] that allows you to edit the bottom elevation of each layer. Note that the top and bottom layer elevations must be entered regardless of the which layer data package (BCF, LPF, HUF) is chosen even though these values may not be used because of certain package options. | |
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| === Confining Beds=== | | == LGR Options == |
| The ''Layer Confining Beds'' dialog, accessed from the ''Global Options/Basic Package'' dialog, allows you to select which layers will have a confining bed below them. The last layer in the grid may not have a confining bed. | | The '''LGR Options''' button opens the [[GMS:MODFLOW-LGR#LGR_Options|''LGR Options'']] dialog to place values for each specified simulation. |
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| Confining beds are most common in older models where the user was trying to conserve memory in solving the groundwater model. In general, it is recommended that you explicitly model all of the layers in the system instead of using confining beds. This feature is supported in GMS to make it possible for users to read in older models.
| | == Layers == |
| | Opens the [[GMS:MODFLOW Array Editor|''Layer'']] dialog which allows values to be assigned to the cells on a specific layer. |
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| In the spreadsheet, the user may turn on the confining bed option for any of the layers except the last layer in the grid.
| | == Porosity == |
| | The '''Porosity''' button brings up the Aquifer Layer Porosity dialog. The array defining the porosity of each cell in the model can be defined and edited by selecting the Porosity button. |
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| The '''Confining Bed Elevations''' button brings up the [[GMS:MODFLOW Array Editor|array editor]] that allows the user to edit the elevation of each layer.
| | == Set Pass Through == |
| | For use with MODFLOW-USG and MODFLOW-USG Transport. This options allows defining cells as pass through cells. Click the '''Set Pass Through''' button will access the ''Pass Through Thickness'' dialog where the ''Maximum call thickness'' can be set. Cells smaller than the specified thickness will be set as pass through cells. Pass through cells will have an inactive IBOUND and will be bypassed when making vertical connections when saving the DISU package. Top and bottom cells will be adjusted sop the cell has zero thickness. To be a vertical pass through cell the cell must have an active cell above and below a series of pass through cells. Pass through cells greater than the specified thickness will be removed. Setting pass through cells requires a stacked grid. |
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| [[Category:MODFLOW]] | | [[Category:MODFLOW]] |
| [[Category:MODFLOW Packages]] | | [[Category:MODFLOW Packages]] |
| | [[Category:MODFLOW Dialogs]] |
| | [[Category:Needs Update]] |
| MODFLOW |
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| Pre-processing |
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MODFLOW Commands |
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Building a MODFLOW Model |
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Map to MODFLOW |
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Calibration |
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Packages Supported in GMS |
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Saving a MODFLOW Simulation |
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Importing MODFLOW Files |
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Unsupported MODFLOW Features |
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Run MODFLOW |
| Post-processing |
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MODFLOW Display Options |
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MODFLOW Post-Processing Viewing Options |
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Reading a MODFLOW Simulation |
| Tutorials |
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| Packages |
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| Flow: |
BCF6, HUF, LPF, UPW |
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| Solvers: |
DE4, GMG, NWT, PCG,
PCGN, LMG, SIP, SOR,
SMS |
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| Other: |
BAS6, BFH, CHD1, CLN,
DRN1, DRT1, EVT1, ETS1,
GAGE, GHB1, GNC, HFB1,
HUF, LAK3, MNW1, MNW2,
OUT1, RCH1, RIV1, SFR2,
STR1, SUB1, SWI2, WEL1,
UZF1 |
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Once the MODFLOW simulation has been initialized, the next step is to enter the data required by the Global Options/Basic package. This includes data defining fundamental program options such as the computational time intervals (stress periods), an array defining which cells are inactive and which cells have constant heads, an array of starting head values for a transient simulation, and a set of flags defining which of the other packages are to be used. The input data for this package should be entered before editing any of the other packages. The MODFLOW Global Options/Basic Package dialog is accessed through the Global Options command in the MODFLOW menu.
The options in the dialog are as follows:
Headings
The
MODFLOW Global / Basic Package dialog.
The two headings are optional text strings which are written to the MODFLOW text output file.
Version
The MODFLOW version can be specified with the choices being (as of Apr 2014):
- MODFLOW-2000
- MODFLOW-2005
- MODFLOW-NWT
- MODFLOW-LGR
- MODFLOW-USG
- MODFLOW-USG Transport
The type of binary executable can be specified using one or more of the following choices:
- Double precision – Uses 8 bytes rather than 4 bytes to store the number so they are more precise but calculations may take longer and binary files that store double-precision variables will be bigger than if single-precision had bee used.
- Parallel – Enables parallel processing capabilities.
- 64 bit – Process using 64 bytes to store the number.
The Save native text copy option will save native ascii MODFLOW input files when the project is saved. An additional folder named myProject_MODFLOW_text is created that contains these files.
The Use custom Run dialog option will bring up the Custom Run MODFLOW dialog when the MODFLOW | Run MODFLOW menu command is selected.
The Set as Default button will set the selected model run options as the default MODFLOW model run options for GMS.
Run Options
The run options are not part of the actual MODFLOW input files, but present different ways that MODFLOW 2000 can be run from GMS.
- Forward Run
- A Forward run is a normal MODFLOW simulation. If parameters have been defined for either a stochastic or parameter estimation run, the mean or starting values of the parameters are used for the forward run.
- Parameter Estimation
- In the Parameter Estimation mode, a set of parameters is found that minimizes the residual between observed and simulated heads and flows. These options are described in more detail on the Automated Parameter Estimation page. This option is only available with the LPF and HUF flow packages.
- Stochastic Simulation
- The Stochastic Simulation option is used to perform a stochastic simulation using the Monte Carlo or Latin Hypercube methods for randomizing a selected set of parameters. Stochastic simulations can also be performed using a material set approach (indicator simulations). A risk analysis wizard can be used to analyze the results for a probabilistic threshold analysis or a probabilistic capture zone delineation. These options are described in more detail on the stochastic simulation page.
- Stochastic Inverse Model
- If the Material Set option is used for stochastic simulations, the Stochastic Inverse option can be used to perform automated parameter estimation on each of the N candidate model instances in the stochastic. The weighted RMS errors for each of the resulting optimized solutions can be used to weight the computations performed by the risk analysis wizard. This option is only available with the LPF and HUF flow packages.
Model Type
The simulation can be designated as either Steady state or Transient. If a steady state simulation is specified, certain portions of the MODFLOW interface such as the Stress Period dialog are inactivated since they are not relevant.
No Flow Head (HNOFLO)
This is the value of head to be assigned to all inactive (no flow) cells (IBOUND=0) throughout the simulation.
Stress Periods
The Stress Periods button is used to bring up the Stress Period dialog. The stress periods should be defined before any of the sources/sinks are entered. If the steady state option is selected, the Stress Periods button is dimmed.
Packages
The Packages button brings up the Packages dialog.
Units
The Units button the Basic Package dialog brings up the Units dialog.
IBOUND
The IBOUND button of the Global Options\Basic Package dialog brings up the Array Editor. The IBOUND array contains a value for each cell in the grid defining the type of the cell as constant head, inactive, or variable head.
- Constant Head
- A negative value indicates that the cell has a constant head. The value of the constant head is defined in the starting heads array.
- Inactive
- An IBOUND value of zero indicates that the cell is inactive (no-flow).
- Variable Head
- A positive IBOUND value indicates that the cell has a variable head (i.e., the head value will be computed as part of the simulation).
Editing the IBOUND Array
There are several ways to change the active/inactive status (positive vs. zero) of a cell before or after initializing the IBOUND array. One method is to directly edit the IBOUND array using the IBOUND dialog. Another method is to select the Cell Attributes command in the MODFLOW menu. In most cases, the most efficient method is to use the Activate Cells in Coverage command in the Map module. This method uses a polygon to define the active and inactive regions.
The constant head cells are typically assigned or edited in one of three ways. One method is to directly edit the IBOUND array. Another method is to select a set of cells and use the Cell Properties dialog in the MODFLOW menu. The simplest method is to define the constant head zones using feature objects as part of a conceptual model in the Map module.
Starting Heads
The starting head values are used as initial conditions for head for both steady state and transient simulations. The Starting Heads button on the left side of the Basic Package dialog is used to enter the values of the starting heads array. Selecting the Starting Heads button brings up the MODFLOW Array Editor.
Force Convergence (CONVERGE)
Forces converging.
Top Elevation
The Top Elevation button brings up an Array Editor that allows editing of the top elevation of each layer. GMS requires that the top and bottom elevations for adjacent layers be the same. This means that when editing the bottom of one layer, move down to the next layer, and edit the top of that layer, the bottom of the previous layer will also be changed. Note that the top and bottom layer elevations must be entered regardless of the which layer data package (BCF, LPF, HUF) is chosen even though these values may not be used because of certain package options.
Bottom Elevation
The Bottom Elevation button brings up an Array Editor that allows editing the bottom elevation of each layer. Note that the top and bottom layer elevations must be entered regardless of the which layer data package (BCF, LPF, HUF) is chosen even though these values may not be used because of certain package options.
The
Layer Confining Bed dialog.
Confining Beds
The Layer Confining Beds dialog, accessed from the Global Options/Basic Package dialog, allows selecting which layers will have a confining bed below them. The last layer in the grid may not have a confining bed.
Confining beds are most common in older models where the user was trying to conserve memory in solving the groundwater model. In general, it is recommended that users explicitly model all of the layers in the system instead of using confining beds. This feature is supported in GMS to make it possible for users to read in older models.
In the spreadsheet, the user may turn on the confining bed option for any of the layers except the last layer in the grid.
The Confining Bed Elevations button brings up the Array Editor that allows the user to edit the elevation of each layer.
LGR Options
The LGR Options button opens the LGR Options dialog to place values for each specified simulation.
Layers
Opens the Layer dialog which allows values to be assigned to the cells on a specific layer.
Porosity
The Porosity button brings up the Aquifer Layer Porosity dialog. The array defining the porosity of each cell in the model can be defined and edited by selecting the Porosity button.
Set Pass Through
For use with MODFLOW-USG and MODFLOW-USG Transport. This options allows defining cells as pass through cells. Click the Set Pass Through button will access the Pass Through Thickness dialog where the Maximum call thickness can be set. Cells smaller than the specified thickness will be set as pass through cells. Pass through cells will have an inactive IBOUND and will be bypassed when making vertical connections when saving the DISU package. Top and bottom cells will be adjusted sop the cell has zero thickness. To be a vertical pass through cell the cell must have an active cell above and below a series of pass through cells. Pass through cells greater than the specified thickness will be removed. Setting pass through cells requires a stacked grid.
