# GMS:MODFLOW Packages Supported in GMS

MODFLOW | |
---|---|

Pre-processing | |

MODFLOW Commands | |

Building a MODFLOW Model | |

Map to MODFLOW | |

Calibration | |

Packages Supported in GMS | |

Saving a MODFLOW Simulation | |

Importing MODFLOW Files | |

Unsupported MODFLOW Features | |

Post-processing | |

MODFLOW Display Options | |

MODFLOW Post-Processing Viewing Options | |

Reading a MODFLOW Simulation | |

Tutorials | |

MODFLOW Tutorials | |

Packages | |

Flow: |
BCF6, HUF, LPF, UPW |

Solvers: |
SMS |

Other: |
UZF1 |

## Contents

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.

After specifying packages for a MODFLOW simulation, the package parameters for each package can be reached through the *MODFLOW* menu; or by right-clicking on the package icon in the Project Explorer and selecting the **Properties** command.

## Global Options & Output

Abbrev. Name | Package/File Name | USGS | Description | Always Req'd? | Extension |
---|---|---|---|---|---|

MFN | Name file | [1] | The MODFLOW name file. GMS uses "mfn" as the extension. | Yes | *.mfn |

BAS6 | Basic Package | [2] | Used to specify the grid dimensions, the computational time steps, and an array identifying which packages are to be used. | Yes | *.ba6 |

DIS | Discretization File | [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 |

OUT1 | Output Control | [4] | Controls what information is to be output from MODFLOW and when it is to be output. | No | *.oc |

## Flow Packages

Interfaces to four different flow packages are provided in GMS: the block-centered flow (BCF), the layer property flow (LPF), the hydrogeologic unit flow (HUF), and the upstream weighting (UPW) packages. One of these four packages must be selected in the *Packages* dialog.

Abbrev. Name | Package Name | USGS | Description | Always Req'd? | Extension |
---|---|---|---|---|---|

BCF6 | Block-Centered Flow Package | [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. | Yes^{[n 1]} |
*.bcf |

LPF | Layer Property Flow Package | [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. | Yes^{[n 1]} |
*.lpf |

UPW | Upstream Weighting Flow Package | [7] | Based on the LPF package. Modified to provide a linear formulation that can be used with the NWT solver. | Yes^{[n 1]} |
*.upw |

HUF | Hydrogeologic Unit Flow Package | [8] | Defines the model stratigraphy in a grid independent fashion (in the vertical direction). | Yes^{[n 1]} |
*.huf |

## Solver Packages

Abbrev. Name | Package Name | USGS | Description | Always Req'd? | Extension |
---|---|---|---|---|---|

GMG | Geometric Multi-Grid | [9] | The Geometric Multigrid Solver is used to solve the finite difference equations in each step of a MODFLOW stress period. | Yes^{[n 2]} |
*.gmg |

SIP1 | Strongly Implicit Procedure | [10] | The Strongly Implicit Procedure package is used to solve the finite difference equations in each step of a MODFLOW stress period. | Yes^{[n 2]} |
*.sip |

PCG | Preconditioned Conjugate Gradient Method | [11] | The Preconditioned Conjugate-Gradient package is used to solve the finite difference equations in each step of a MODFLOW stress period. | Yes^{[n 2]} |
*.pcg |

PCGN | Preconditioned Conjugate Gradient Solver with Improved Nonlinear Control | [12] | The Preconditioned Conjugate-Gradient package is used to solve the finite difference equations in each step of a MODFLOW stress period. | Yes^{[n 2]} |
*.pcgn |

SOR1 | Slice-Successive Overrelaxation Method | [13] | The Slice-Successive Overrelaxation package is used to solve the finite difference equations in each step of a MODFLOW stress period. | Yes^{[n 2]} |
*.sor |

SAMG or LMG | Algebraic Multi-Grid for Systems Solver | [14] | The LMG or Link-AMG package is used to solve the finite difference equations in each step of a MODFLOW stress period. | Yes^{[n 2]} |
*.lmg |

DE4 | Direct Solver | [15] | The DE4 package is used to solve the finite difference equations in each step of a MODFLOW stress period. | Yes^{[n 2]} |
*.de4 |

NWT | Newton Solver | [16] | The NWT package is used to solve the finite difference equations in each step of a MODFLOW-NWT stress period. | Yes^{[n 2]} |
*.nwt |

SMS | Sparse Matrix Solver | [17] | The SMS package is used to solve the finite volume equations in each step of a MODFLOW-USG stress period. | Yes^{[n 2]} |
*.sms |

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

Abbrev. Name | Package Name | USGS | Description | Always Req'd? | Extension |
---|---|---|---|---|---|

BFH | Boundary Flow and Head Package | [18] | Used with MODFLOW-LGR to use coupled flows and heads when running parent or child model independently. | No | *.bfh_hed, *.bfh_flw |

CLN | CLN Process | MODFLOW-USG process to simulate Connected Linear Network. | No | *.cln | |

DRN1 | Drain Package | [19] | Simulates drain type boundary conditions. | No | *.drn |

DRT1 | Drain Return Package | [20] | Simulates drain return type boundary conditions. | No | *.drt |

EVT1 | Evapotranspiration Package | [21] | Simulates the effect of evapotranspiration in the vadose zone. | No | *.evt |

ETS1 | Evapotranspiration Segments Package | [22] | "allows simulation of evapotranspiration with a user-defined relation between evapotranspiration rate and hydraulic head."^{[1]} |
No | *.ets |

GAGE | Gage Package | [23] | Allows SFR and lake gaging stations. Gaging station prints time series values for gage location. | No | *.gag |

GHB1 | General Head Boundary Package | [24] | Simulates a general purpose head-dependent source/sink. Commonly used to simulate lakes. | No | *.ghb |

GNC | Ghost Node Correction Package | Only in MODFLOW-USG, corrects for cells whose connector does not perpendicularly bisect the face. | No | *.gnc | |

HFB1 | Horizontal Flow Barrier Package | [25] | Simulates the effect of horizontal flow barriers such as sheet piles and slurry trenches. | No | *.hfb |

LAK3 | Lake Package | [26] | 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 |

MNW1 | Multi-Node Well 1 Package | [27] | older revision of MNW package used to simulate wells that extend over more than one cell. | No | *.mnw |

MNW2 | Multi-Node Well 2 Package | [28] | updated revision of MNW1 package used to simulate wells that extend over more than one cell. | No | *.mnw2 |

RCH1 | Recharge Package | [29] | Simulates recharge to the groundwater from precipitation. | No | *.rch |

RIV1 | River Package | [30] | Simulates river type boundary conditions. | No | *.riv |

SFR2 | Streamflow-Routing Package | [31] | 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 |

STR1 | Stream-Routing Package | [32] | 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 |

CHD1 | Time Variant Specified Head Package | [33] | Simulates specified head boundary conditions where the head is allowed to vary with time. | No | *.chd |

SUB1 | Subsidence Package | [34] | Simulates simulates aquifer compaction and land subsidence. | No | *.sub |

SWI2 | Seawater Intrusion Package | [35] | Simulates variable-density seawater intrusion in MODFLOW-2005. | No | *.swi |

WEL1 | Well Package | [36] | Simulates injection/extraction wells. | No | *.wel |

UZF1 | Unsaturated-Zone Flow Package | [37] | 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 |

MFW | 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 | An Advanced Spatial Parameterization file (unavailable in USG) 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 Documentation.

## Notes

- ↑
^{1.0}^{1.1}^{1.2}^{1.3}One of the flow packages must be used. - ↑
^{2.0}^{2.1}^{2.2}^{2.3}^{2.4}^{2.5}^{2.6}^{2.7}^{2.8}One of these solvers must be selected in the*Packages*dialog.

## References

- ↑
Banta, Edward R. (2000),
*MODFLOW-2000, The U.S. Geological Survey Modular Ground-Water Model-Documentation of Packages for Simulating Evapotranspiration with a Segmented Function (ETS1) and Drains with Return Flow (DRT1). Open-File Report 00-466.*, Denver, Colorado, http://water.usgs.gov/nrp/gwsoftware/modflow2000/ofr00-466.pdf

GMS – Groundwater Modeling System | ||
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