Numerical Modeling Workflow - Finite Difference Grids > Translation Settings > MODFLOW > Advanced Settings

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Advanced Settings

 

Advanced translation settings are available for flow simulations to enable more advanced control of translation and package settings.  General and package-specific advanced settings are described below.  General advanced settings are available for all Flow and Transport engines supported by Visual MODFLOW Flex, while certain engines have additional package-specific advanced settings available:

 

General

MODFLOW-2005

MODFLOW-SURFACT

 

Advanced settings for SEAWAT warrant more detailed discussion and are presented separately for the VDF and VSC packages in individual sections.

Advanced Settings - General

The following settings are available for all packages:

 

CUnit: The index for the package in the CUNIT array of the BAS file [read-only]

Ext: The file extension of the package [read-only]

LUnit: The file unit number to which the package will be read/written during the engine run [read-only]

Run: Yes/No switch to determine whether the package will be added to the .NAM/.IN file and run during the simulation. Note: certain packages are required as part of a simulation (e.g. BAS file) and cannot be selected to not run.

Translate: Yes/No switch to determine whether the package will be translated. Note: packages that do not have sufficient data will not be translated (e.g. a river package file will not be translated if no rivers are listed in the model explorer in the active numerical model workflow).

 

Note: If a supported package is not represented in the model, by default it will not be translated and run, even if translate and run are both set to "Yes".  For example if there are no drains represented in the model, then the DRN package will not be translated and run.  

 

Custom/Pre-existing Input Files

If you develop or modify a package input file outside of Visual MODFLOW Flex, you can still use it as part of your modeling workflow within the Flex environment. This is particularly useful if you want to use one or more packages that are not yet supported in Visual MODFLOW Flow or if you have custom methods/utilities to generate input files.  To use a custom input file:

1.Set Run = Yes

 

2.Set Translate = No

 

3.Add the input file to the model run folder with the correct name and extension: [model].[ext]. The model run folder can be found by selecting the folder icon button [], the model name will correspond to the name of your conceptual model, and the extension will be the Ext value for the package in question. For example, if you will to run the drain return package (DRT), and you are running a model where:

 

the Visual MODFLOW Flex project file is called SiteModel.amd,

the Conceptual Model is called Concept1,

the Grid is called NumericalGrid,

the Run is called Run 1, and

the Flow Engine is MODFLOW-2005

then the DRT file must be saved as:
.\SiteModel.data\MODFLOW\NumericalGrid\Run1\MODFLOW-2005\Concept1.DRT

 

If the above conditions are met, the custom package file will inserted into the relevant .NAM/.IN file and run with the model. Note that certain results from unsupported packages will not be read back into Visual MODFLOW Flex, such as the flow balance terms associated with the SFR package.

Advanced Settings - MODFLOW-2005

UZF Settings

The following settings are specific to the UZF package:

 

Unsaturated Zone Connection Option (NUZOPT) - An integer value used to define which cell in a vertical column that recharge and discharge is simulated.

o1 - Recharge to and discharge from only the top model layer. This option assumes land surface is defined as top of layer 1.

o2  - Recharge to and discharge from the specified layer in variable IUZFBND. This option assumes land surface is defined as top of layer specified in IUZFBND.

o3 - Recharge to and discharge from the highest active cell in each vertical column. Land surface is determined as top of layer specified in IUZFBND. A constant head node intercepts any recharge and prevents deeper percolation.

 

Vertical Hydraulic Conductivity Option (IUZFOPT) - An integer value equal to 0, 1, or 2.

o0 - flow will not be routed through the unsaturated zone, rather infiltration will be applied directly to the saturated zone.

o1 - vertical hydraulic conductivity will be specified within the UZF1 Package input file using array VKS. [not supported]

o2 -vertical hydraulic conductivity will be specified within either the BCF or LPF Package input file

 

Water Routing (IRUNFLG) - An integer value that specifies whether ground water that discharges to land surface will be routed to stream segments or lakes as specified in the IRUNBND array (IRUNFLG not equal to zero) or if ground-water discharge is removed from the model simulation and accounted for in the ground-water budget as a loss of water (IRUNFLG=0). The Streamflow-Routing (SFR2) and(or) the Lake (LAK3) Packages must be active if IRUNFLG is not zero.

Evapotranspiration (IETFLG) - An integer value that specifies whether or not evapotranspiration (ET) will be simulated. ET will not be simulated if IETFLG is zero, otherwise it will be simulated.

Unsaturated Budget Output Method 1 (IUZFCB1) - An integer value used as a flag for writing ground-water recharge, ET, and ground-water discharge to land surface rates to a separate unformatted file using subroutine UBUDSV. If IUZFCB1>0, it is the unit number to which the cell-by-cell rates will be written when “SAVE BUDGET” or a non-zero value for ICBCFL is specified in Output Control. If IUZFCB1 ≤ 0, cell-by-cell rates will not be written to a file.

Unsaturated Budget Output Method 2 (IUZFCB2) - An integer value used as a flag for writing ground-water recharge, ET, and ground-water discharge to land surface rates to a separate unformatted file using module UBDSV3. If IUZFCB2>0, it is the unit number to which cell-by-cell rates will be written when “SAVE BUDGET” or a non-zero value for ICBCFL is specified in Output Control. If IUZFCB2≤0, cell-by-cell rates will not be written to file.

Number of Trailing Waves (NTRAIL2) - An integer value equal to the number of trailing waves used to define the water-content profile following a  decrease in the infiltration rate. The number of trailing waves varies depending on the problem, but a range between 10 and 20 is usually adequate. More trailing waves may decrease mass-balance error and will increase computational requirements and memory usage. This variable is not specified if IUZFOPT is zero or less.

Number of Wave Sets (NSETS2) - An integer value equal to the number of wave sets used to simulate multiple infiltration periods. The number of wave sets should be set to 20 for most problems involving time varying infiltration. The total number of waves allowed within an unsaturated zone cell is equal to NTRAIL2 * NSETS2. An error will occur if the number of waves in a cell exceeds this value. This variable is not specified if IUZFOPT is zero or less.

Average Undulation Depth (SURFDEP) - A real value equal to the average undulation depth within a finite-difference cell.

 

Advanced Settings - MODFLOW-SURFACT

 

Basic Flow (BAS) Package Settings

The following settings are specific to the BAS package:

IDUAL - An integer value used to define the dual-domain model for transport simulations:

oIf IDUAL=0, the simulation is for a single domain continuum.

oIf IDUAL=1, the simulation is for a dual domain representation with no equilibrium sorption occurring in the immobile domain.

oIf IDUAL=2, the simulation is for a dual domain representation with equilibrium sorption characteristics of the immobile domain being equal to that of the mobile domain at any node in the system.

oIF IDUAL=3, the simulation is for a dual domain representation with equilibrium adsorption characteristics of the immobile domain being distinct from those of the mobile domain, requiring additional input of these properties.

 

ITRAN - An integer flag that determines if the simulation is either flow only or flow and transport.

oIf ITRAN = 0, the simulation is for flow only.

oIf ITRAN = 1, the simulation is for both flow and transport.

 

The above settings will override the Modeling Objectives selections and can be used to simplify the model without affecting the values stored in at the Modeling Objectives step or in the model explorer.

Note: you will likely encounter errors running the model if you select a higher value of IDUAL or ITRAN than you have set up your model to handle, for example: selecting ITRAN=1 without first having set up transport species.

 

Block-Centered Flow (BCF4) Package Settings

The following settings are specific to the BCF4 package:

ATMGP - Standard atmospheric pressure

COMPAIR - Compressibility of air

COMPWATER - Compressibility of water

GRAV - Gravitational acceleration contant

IREALSL -  is a flag indicating which soil moisture functions are used to define flow in the unsaturated zone above the water-table:

IREALSL = 0

Pseudo-soil relations are used

IREALSL > 0

Flow in the vadose is treated rigorously

IREALSL = 1

groundwater flow is simulated in the vadose zone and the van Genuchten functions are used for retention and relative permeability characteristics of the unsaturated layer(s).

IREALSL = 2

groundwater flow is simulated in the vadose zone and the van Genuchten function is used for retention and the Brooks-Corey function is used for relative permeability characteristics of the unsaturated layer(s).

IREALSL = 3

soil vapor flow is simulated in the vadose zone and the van Genuchten functions are used for retention and relative permeability characteristics of the unsaturated layer(s).

IREALSL = 4

soil vapor flow is simulated in the vadose zone and the van Genuchten function is used for retention and the Brooks-Corey function is used for relative permeability characteristics of the unsaturated layer(s).

 

RHOAP - Density of air at reference pressure.

RHOWP - Density of water.

VISG - Viscosity of air.

VISW - viscosity of water

 

Basic Transport (BTN) Package Settings

The following settings are specific to the BTN package:

LINR - is an integer flag indicating which retardation model will be used:

o0 - retardation is not applied

o1 - linear retardation is applied

o2 - non-linear retardation is applied using the Freundlich isotherm sorption model

 

Recharge-Seepage Face (RSF4) Package Settings

The following settings are specific to the RSF4 package:

IUNCNF - is an integer flag for the unconfined option:

o0 - the specified recharge (RECH) is applied always like in a confined case even if the calculated water table exceeds the top elevation in layer 1.

o1 - Recharge seepage face boundary condition is employed and recharge (RECH) will be applied until water table reaches the ponding elevations described in PNDEL array.

 

NRCHOP - is an integer flag for the recharge option. Recharge rates are defined in a two-dimensional array (RECH) with one value for each vertical column. Accordingly, recharge is applied to one cell in each vertical column, and the option code determines which cell in the column is selected for recharge. NRCHOP can have the following values:

o1 - Recharge is only applied to the top grid layer

o2 - Vertical distribution of recharge is specified in array IRCH [option not currently supported]

o3 - Recharge is applied to the highest active cell in each vertical column. Note: a constant-head node intercepts recharge and prevents deeper infiltration

 

Time-Varying Material Properties (TMP1) Package Settings

The following settings are specific to the TMP1 package:

ICRREAD - is a switch for reading/using the vertical hydraulic conductivity (Kzz) scaling information (Cannot be used with ICVREAD).

ICVREAD - is a switch for reading/using the vertical leakance scaling information. (Cannot be used with ICRREAD).

IHYREAD - is a switch for reading/using the horizontal hydraulic conductivity (Kxx, Kyy) scaling information

ISC1READ - is a switch for reading/using the specific storage (Ss) scaling information

ISC2READ - is a switch for reading/using the specific yield (Ss) scaling information

 

NOTE: if ISC1READ/ISC2READ are scaled, IHYREAD is required (even if the scaling values are all set to 1).

 

 

 

 

 


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