1. GWF BASIC PACKAGE
Reads data specifying initial and boundary conditions (IBOUND, STRT).
Select options such as plan-view model or cross-section model (XSECTION), free format or fixed format (FREE), and performing or not performing certain constant head node calculations (CHTOCH).
Reads a dummy head value to indicate inactive cells (HNOFLO)
BAS6

2. GWF BASIC PACKAGE
Basic input data from file type specified as BAS6 in the Name File
Options
Is a character variable scanned for words. Three options are currently recognized
XSECTION
CHTOCH
FREE
A blank record is acceptable as no options (so is the words No Options)
BAS6

3. GWF BASIC PACKAGE OPTIONS XSECTION
Indicates that the model is a 1-row cross section with arrays dimensioned (NCOL,NLAY).
CHTOCH
Indicates that the flow between adjacent constant-head cells should be calculated.
FREE
Specifies that free format is to be used in all packages where applicable.
Note: Be sure all variables read using free format have non-blank values, and have blanks or commas between adjacent values.
BAS6

4. GWF BASIC PACKAGE IBOUND
An array for each layer that contains a code for each layer cell which indicates that
1. The head varies with time,
2. The head is constant (constant head cell), or
3. No flow takes place within the cell (no flow cell)
BAS6

5. GWF BASIC PACKAGE IBOUND(NCOL,NROW) or (NCOL,NLAY) – U2DINT
Is the boundary array, if
IBOUND(I,J,K) < 0 Constant head cell,
IBOUND(I,J,K) = 0 Inactive,
IBOUND(I,J,K) > 0 Variable head
One value is read for every cell, layer at a time except when XSECTION option is specified.
BAS6

6. GWF BASIC PACKAGE
HNOFLO
Is the value head to be assigned to all inactive cells (IBOUND=0) throughout the simulation.
STRT
Is the initial starting head. STRT must be specified for all simulations, including steady state. One value is read for every cell, layer at a time except when XSECTION option is specified.
BAS6

7. GWF BASIC PACKAGE
BAS6