| 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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MODFLOW is divided into a series of components called "packages." Each package performs a specific task. The input for each package is generally contained in a separate file. The MODFLOW packages supported by GMS are listed in the following tables.
The MODFLOW packages to be used in the MODFLOW simulation are specified in the Packages dialog. This dialog is accessed in the Global Options\Basic Package dialog. Some of the packages are always required for a simulation and some are optional. One of the flow model packages and one of the solver packages must be selected. Each of the boundary condition/source/sink packages is optional.
For any package not currently supported in GMS, the file associated with that package will be ignored when the model is imported. However, GMS keeps track of unsupported packages it encounters when reading the name file and, when the project is saved, GMS lists the unsupported packages in the name file and copies the unsupported package files from the old directory to the new directory.
Global Options & Output
| Package/File Name
|
Abrev Name
|
USGS
|
Description
|
Always Req'd?
|
Extension
|
| Name file |
MFN |
[1] |
The MODFLOW name file. GMS uses "mfn" as the extension. |
Yes |
*.mfn
|
| Basic Package |
BAS6 |
[2] |
Used to specify the grid dimensions, the computational time steps, and an array identifying which packages are to be used. |
Yes |
*.bas
|
| Discretization File |
DIS |
[3] |
The Discretization File is used to specify certain data used in all models. These include, the number of rows, columns and layers, the cell sizes, the presence of Quasi-3D confining beds, the time discretization. |
Yes |
*.dis
|
| Output Control |
OUT1 |
[4] |
Controls what information is to be output from MODFLOW and when it is to be output. |
No |
*.oc
|
Flow Packages
Interfaces to three different flow packages are provided in GMS: the block centered flow (BCF), the layer property flow (LPF), and the hydrogeologic unit flow (HUF) packages. One of these three packages must be selected in the Packages dialog.
| Package Name
|
Abrev Name
|
USGS
|
Description
|
Always Req'd?
|
Extension
|
| Block Centered Flow Package |
BCF6 |
[5] |
Performs the cell by cell flow calculations. The input to this package includes layer types and cell attributes such as storage coefficients and transmissivity. Parameters for sensitivity analysis or parameter estimation are NOT supported. |
Yes1 |
*.bcf
|
| Layer Property Flow Package |
LPF |
[6] |
Performs the cell by cell flow calculations. The input to this package includes layer types and cell attributes such as storage coefficients and transmissivity. |
Yes1 |
*.lpf
|
| Hydrogeologic Unit Flow Package |
HUF |
[7] |
Defines the model stratigraphy in a grid independent fashion (in the vertical direction). |
Yes1 |
*.huf
|
1 One of the flow packages must be used.
Solver Packages
| Package Name
|
Abrev Name
|
USGS
|
Description
|
Always Req'd?
|
Extension
|
| Geometric Multi-Grid |
GMG |
[8] |
The Geometric Multigrid Solver is used to solve the finite difference equations in each step of a MODFLOW stress period. |
Yes1 |
*.gmg
|
| Strongly Implicit Procedure |
SIP |
[9] |
The Strongly Implicit Procedure package is used to solve the finite difference equations in each step of a MODFLOW stress period. |
Yes1 |
*.sip
|
| Preconditioned Conjugate Gradient Method |
PCG2 |
[10] |
The Preconditioned Conjugate-Gradient package is used to solve the finite difference equations in each step of a MODFLOW stress period. |
Yes1 |
*.pcg
|
| Slice-Successive Overrelaxation Method |
SOR |
[11] |
The Slice-Successive Overrelaxation package is used to solve the finite difference equations in each step of a MODFLOW stress period. |
Yes1 |
*.sor
|
| Algebraic MultiGrid for Systems Solver |
SAMG or LINK-AMG |
[12] |
The Link-AMG package is used to solve the finite difference equations in each step of a MODFLOW stress period. |
Yes1 |
*.lmg
|
1 One of these solvers must be selected in the Packages dialog.
Once a solver has been selected, the appropriate solver package dialog can be accessed through one of the solver commands (LMG, SIP, PCG2, or SSOR) in the MODFLOW menu. The default values shown in each dialog are typically adequate.
For more information on Solver Packages visit: http://water.usgs.gov/nrp/gwsoftware/modflow2000/MFDOC/index.html
Optional Packages
| Package Name
|
Abrev Name
|
USGS
|
Description
|
Always Req'd?
|
Extension
|
| Drain Package |
DRN1 |
[13] |
Simulates drain type boundary conditions. |
No |
*.drn
|
| Drain Return Package |
DRT1 |
[14] |
Simulates drain return type boundary conditions. |
No |
*.drt
|
| Evapotranspiration Package |
EVT1 |
[15] |
Simulates the effect of evapotranspiration in the vadose zone. |
No |
*.evt
|
| Evapotranspiration Segments Package |
ETS1 |
[16] |
"allows simulation of evapotranspiration with a user-defined relation between evapotranspiration rate and hydraulic head."[1] |
No |
*.ets
|
| General Head Boundary Package |
GHB1 |
[17] |
Simulates a general purpose head-dependent source/sink. Commonly used to simulate lakes. |
No |
*.hff
|
| Horizontal Flow Barrier Package |
HFB1 |
[18] |
Simulates the effect of horizontal flow barriers such as sheet piles and slurry trenches. |
No |
*.hfb
|
| Lake Package |
LAK3 |
[19] |
A more sophisticated alternative to the typical approach of using the General head package to simulate the effect of lakes and reservoirs. Computes the stage based on the water budget unlike the GHB. |
No |
*.lak
|
| Multi-Node Well Package |
MNW1 |
[20] |
used to simulate wells that extend over more than one cell. |
No |
*.mnw
|
| Recharge Package |
RCH1 |
[21] |
Simulates recharge to the groundwater from precipitation. |
No |
*.rch
|
| River Package |
RIV1 |
[22] |
Simulates river type boundary conditions. |
No |
*.riv
|
| SFR Package |
SFR2 |
[23] |
Simulates the exchange of water between the aquifer and surficial streams. Includes routing and automatic computation of stage. Parameters for sensitivity analysis or parameter estimation are NOT supported. |
No |
*.sfr
|
| STR Package |
STR1 |
[24] |
Simulates the exchange of water between the aquifer and surficial streams. Includes routing and automatic computation of stage. Parameters for sensitivity analysis or parameter estimation are NOT supported. |
No |
*.str
|
| Time Variant Specified Head Package |
CHD1 |
[25] |
Simulates specified head boundary conditions where the head is allowed to vary with time. |
No |
*.chd
|
| Well Package |
WEL1 |
[26] |
Simulates injection/extraction wells. |
No |
*.wel
|
| UZF Package |
UZF1 |
[27] |
Simulate percolation of water through the unsaturated zone. |
No |
*.uzf
|
Other Files
Other files that GMS reads and writes with MODFLOW simulations.
| File Name
|
Description
|
Extension
|
| MFS |
MODFLOW "Super" file, created by GMS to keep track of extra information GMS needs. |
*.mfs
|
| MFS |
MODFLOW World file, created by GMS to keep track of the geographic location of a MODFLOW model. |
*.mfw
|
| PRJ |
Projection file in ArcGIS well-known text format specifying a geographic coordinate system. |
*.prj
|
| H5 |
An HDF5 formatted file containing array and list data referenced from other package files. See MODFLOW_with_HDF5 for more information |
*.h5
|
| ASP |
A file used with a special version of MODFLOW modified to use PEST. |
*.asp
|
| PARAM |
Extra information about the parameters used by GMS and our modified version of MODFLOW. |
*.param
|
| M2P |
Used by MF2PEST.EXE program. |
*.m2p
|
Output Files
Standard Extensions for OUTPUT files.
| Package |
Extension
|
|
*.ccf
|
| Drawdown |
*.drw
|
| Global |
*.glo
|
| Head |
*.hed
|
| Output |
*.out
|
If a fort.# file occurs the MODFLOW file was written to the given unit number.
If a file has an underscore (*_...) followed by an extension refer to pages 29 and 30 of the MODFLOW Documentation linked here:MF2K Obs-Sen-Pes
Notes
