The BTN: Basic Transport pane is is on the MODFLOW Packages and Programs dialog box under MT3DMS or MT3D-USGS. It is used to specify some of the data for the BTN package in MT3DMS or MT3D-USGS. Some other data for the BTN package are specified in the the MODFLOW Time and MODFLOW Output Control dialog boxes. The BTN package is required in all MT3DMS and MT3D-USGS models.
The comments can be used to record any information. The first two lines will be the heading for the simulation and will be printed in the MT3DMS output file.
MUNIT is the name of unit for mass, such as LB or KG. Note that this names is used for identification purposes only and does not affect the model outcome.
CINACT is the value for indicating an inactive concentration cell (MT3DMS_Active = False). Even if inactive cells are not anticipated in the model, a value for CINACT still must be submitted.
THKMIN is the minimum saturated thickness in a cell, expressed as the decimal fraction of the model layer thickness (DZ) below which the cell is considered inactive. The default value is 0.01 (i.e., 1 percent of the model layer thickness).
The names of the Mobile and Immobile chemical species are defined on the Chem Species (MT3D and GWT) pane.
The user also defines the names of the Mobile and Immobile chemical species. The names of the chemical species are not part of the MT3DMS or MT3D-USGS input but they are used to identify data sets and output files related to individual chemical species.
The Lake, Stream-Flow, and Unsaturated-Zone Transport packages in MT3D-USGS can only be used if the flow model is a MODFLOW-NWT model.
