Lipan Groundwater Availability Model v1.01
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BCF PACKAGE FLAGS
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HDRY
The head value that is assigned to cells that are converted to dry during a simulation.

HDRY 	= 999 (for all layers)

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Ltype
0 = confined =  		Transmissivity and storage coefficient of the layer are constant for the entire simulation.
1 = unconfined =		Transmissivity of the layer varies. It is calculated from the saturated thickness and
						hydraulic conductivity. The storage coefficient is constant. This type code is valid only for layer 1.
2 = unconfined/confined=Transmissivity of the layer is constant. The storage coefficient may alternate
						between confined and unconfined values. Vertical flow from above is limited if the layer desaturates.
3 = unconfined/confined=Transmissivity of the layer varies. It is calculated from the saturated thickness
						and hydraulic conductivity. The storage coefficient may alternate between confined and unconfined
						values. Vertical flow from above is limited if the aquifer desaturates.

LAYTYP = 1 (for all layers)

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TRPY
is a one-dimensional variable containing a horizontal anisotropy factor for each layer. It is the ratio of
transmissivity or hydraulic conductivity (whichever is being used) along a column to transmissivity or hydraulic
conductivity along a row. Set to 1.0 for isotropic conditions. This is a single variable with one value per layer. Do
not read a variable for each layer—that is, include only one array control record for the entire variable. Note that
the LPF Package can be used to represent horizontal anisotropy that varies in magnitude within a model layer.

TRPY = 1 (for all layers)
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IWDFLG
0 	=	wetting is inactive
not 0 = wetting is active

IWDFLG	= 0 (for all layers)
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WETFCT
is a factor that is included in the calculation of the head that is initially established at a
cell when it is converted from dry to wet.

WETFCT = .2 (for all layers)

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IWETIT
is the iteration interval for attempting to wet cells. Wetting is attempted every IWETIT
iterations. If using the PCG solver (Hill, 1990), this applies to outer iterations, not inner
iterations. If IWETIT is 0, it is changed to 1.

IWETIT = 2 (for all layers)

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IHDWET
is a flag that determines which equation is used to define the initial head at cells that
become wet:
If IHDWET = 0, equation (3a) (McDonald and others, 1992) is used:
h = BOT + WETFCT (hn - BOT)
If IHDWET is not 0, equation (3b) (McDonald and others, 1992) is used:
h = BOT + WETFCT (WETDRY)

IHDWET = 0 (for all layers)

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BOUNDARY CONDITION PACKAGE FLAGS
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RECHARGE PACKAGE

NRCHOP
is the recharge option code. Recharge fluxes are defined in a two-dimensional array,
RECH, with one value for each vertical column. Accordingly, recharge is applied to one cell in
each vertical column, and the option code determines which cell in the column is selected for
recharge.
1 - Recharge is only to the top grid layer.
2 - Vertical distribution of recharge is specified in array IRCH.
3 - Recharge is applied to the highest active cell in each vertical column. A constant head
	node intercepts recharge and prevents deeper infiltration.

NRCHOP = 1

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EVT PACKAGE

NEVTOP 
is the evapotranspiration (ET) option code. ET parameters (ET surface, maximum ET
rate, and extinction depth) are specified in two-dimensional arrays, SURF, EVTR, and EXDP,
with one value for each vertical column. Accordingly, ET is calculated for one cell in each
vertical column. The option codes determine for which cell in the column ET will be calculated.
1 = ET is calculated only for cells in the top grid layer.
2 = The cell for each vertical column is specified by the user in array IEVT.

NEVTOP = 1
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