Packages Supported in GMS

MODFLOW is divided into a series of components called "packages." Each package performs a specific task. The MODFLOW packages supported by GMS are listed in the following table. Some of the packages are always required for a simulation and some are optional. The input for each package is contained in a separate text file. These packages are the most commonly used packages in MODFLOW.

Each of the packages shown in the table are fully supported by GMS. All of the input for each package can be input or edited using GMS. The package files generated by GMS can be read directly by MODFLOW to perform a simulation. Existing MODFLOW input files can be read directly into GMS for viewing and editing, if desired.

Package Name	Abrev Name	Description	Always Req.'d?
Basic Package	BAS6	Used to specify the grid dimensions, the computational time steps, and an array identifying which packages are to be used.	Y
Output Control	OUT1	Controls what information is to be output from MODFLOW and when it is to be output.	N
Block Centered Flow Package	BCF6	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.	Y†
Layer Propery Flow Package	LPF	Performs the cell by cell flow calculations. The input to this package includes layer types and cell attributes such as storage coefficients and transmissivity.	Y†
Hydrogeologic Unit Flow Package	HUF	Defines the model stratigraphy in a grid independent fashion (in the vertical direction).	Y†
River Package	RIV1	Simulates river type boundary conditions.	N
Recharge Package	RCH1	Simulates recharge to the groundwater from precipitation.	N
Well Package	WEL1	Simulates injection/extraction wells.	N
Drain Package	DRN1	Simulates drain type boundary conditions.	N
Evapotranspiration Package	EVT1	Simulates the effect of evapotranspiration in the vadose zone.	N
General Head Boundary Package	GHB1	Simulates a general purpose head-dependent source/sink. Commonly used to simulate lakes.	N
Stream/Aquifer Interaction Package	STR1	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.	N
Horizontal Flow Barrier Package	HFB1	Simulates the effect of horizontal flow barriers such as sheet piles and slurry trenches.	N
Time Variant Specified Head Package	CHD1	Simulates specified head boundary conditions where the head is allowed to vary with time.	N
Geometric MultiGrid Solver	GMG	An iterative solver based on a multi-grid approach.	Y*
Strongly Implicit Procedure Package	SIP1	An iterative solver based on the strongly implicit procedure.	Y*
Preconditioned Conjugate Gradient Package, Version 2	PCG2	An iterative solver based on the preconditioned conjugate gradient technique.	Y*
Slice Successive Overrelaxation Package	SOR1	An iterative solver based on the slice successive overrelaxation technique.	Y*

† One of the flow packages must be used.
* One of the solver packages must be used.

The MODFLOW Packages Supported by GMS.