BAS6 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

OptionsIs a character variable scanned for words. Three options are currently recognized

XSECTIONCHTOCHFREE

A blank record is acceptable as no options (so is the words No Options)

BAS6 3

GWF BASIC PACKAGEOPTIONS

XSECTIONIndicates that the model is a 1-row cross section with arrays dimensioned (NCOL,NLAY).

CHTOCHIndicates that the flow between adjacent constant-head cells should be calculated.

FREESpecifies 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

IBOUNDAn array for each layer that contains a code for each layer cell which indicates that1. The head varies with time,2. The head is constant (constant head cell), or3. 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, ifIBOUND(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 PACKAGEHNOFLO

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