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LPF - Layer-Property Flow Package

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LPF - Layer-Property Flow Package

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LPF - Layer-Property Flow Package

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Abbreviation in Name file

LPF

Purpose

The Layer-Property Flow package is used to specify properties controlling flow between cells.

Documentation

Related Packages

The Block-Centered Flow package (BCF) and the Hydrogeologic-Unit Flow package (HUF2) are two other packages that can be used to specify properties controlling flow between cells.

The Horizontal Flow Barrier (HFB) package modifies the horizontal conductances between certain, specified pairs of cells.

Supported in

MODFLOW-2000
MODFLOW-2005
MODFLOW-LGR
MODFLOW-CFP
MODFLOW-NWT
MF2005-FMP2

Other Notes

Every model must  use one and only one of the three packages (BCF6, LPF, and HUF2) that are used to specify properties controlling flow between cells.
See the Frequently Asked Questions for information on how to read data from binary files generated by MODFLOW.
The SOR solver (not included in MODFLOW-2005) doesn't work well with the wetting capability.

Input Instructions

Input for the Layer-Property Flow (LPF) Package is read from the file that is type "LPF" in the name file.  Free format is used for reading all values. The LPF Package is an alternative to the BCF Package and HUF2 Package. No more than one of these packages should be used simultaneously.

FOR EACH SIMULATION

Data Set 0

[#Text]

Item 0 is optional—“#” must be in column 1. Item 0 can be repeated multiple times.

Text—is a character variable (199 characters) that starts in column 2. Any characters can be included in Text. The “#” character must be in column 1. Except for the name file, lines beginning with # are restricted to these first lines of the file. Text is printed when the file is read.

Data Set 1

ILPFCB HDRY NPLPF [Options]

ILPFCB—is a flag and a unit number.

If ILPFCB > 0, it is the unit number to which cell-by-cell flow terms will be written when "SAVE BUDGET" or a non-zero value for ICBCFL is specified in Output Control. The terms that are saved are storage, constant-head flow, and flow between adjacent cells.
If ILPFCB = 0, cell-by-cell flow terms will not be written.
If ILPFCB < 0, cell-by-cell flow for constant-head cells will be written in the listing file when "SAVE BUDGET" or a non-zero value for ICBCFL is specified in Output Control. Cell-by-cell flow to storage and between adjacent cells will not be written to any file.

HDRY—is the head that is assigned to cells that are converted to dry during a simulation. Although this value plays no role in the model calculations, it is useful as an indicator when looking at the resulting heads that are output from the model. HDRY is thus similar to HNOFLO in the Basic Package, which is the value assigned to cells that are no-flow cells at the start of a model simulation.

 

Options—are optional key words that activate options:

STORAGECOEFFICIENT indicates that variable Ss and SS parameters are read as storage coefficient rather than specific storage.
CONSTANTCV indicates that vertical conductance for an unconfined cell is computed from the cell thickness rather than the saturated thickness.  The CONSTANTCV option automatically invokes the NOCVCORRECTION option.
THICKSTRT indicates that layers having a negative LAYTYP are confined, and their cell thickness for conductance calculations will be computed as STRT-BOT rather than TOP-BOT.
NOCVCORRECTION indicates that vertical conductance is not corrected when the vertical flow correction is applied.
NOVFC turns off the vertical flow correction under dewatered conditions.  This option turns off the vertical flow calculation described on p. 5-8 of USGS Techniques and Methods Report 6-A16 and the vertical conductance correction described on p. 5-18 of that report.
NOPARCHECK turns off the checking that a value is defined for all cells when parameters are used to define layer data.

Consult pages 5-18 to 5-19 of the MODFLOW-2005 report for information on when it is appropriate to use these options.

 

Data Set 2

LAYTYP—contains a flag for each layer that specifies the layer type. Use as many records as needed to enter a value for each layer.

0—confined
>0 – convertible
<0 – convertible unless the THICKSTRT option is in effect. When THICKSTRT is in effect, a negative value of LAYTYP indicates that the layer is confined, and its saturated thickness will be computed as STRT-BOT.

Data Set 3

LAYAVG—contains a flag for each layer that defines the method of calculating interblock transmissivity. Use as many records as needed to enter a value for each layer.

0—harmonic mean (This is most appropriate for confined and unconfined aquifers with abrupt boundaries in transmissivity at the cell boundaries or for confined aquifers with uniform hydraulic conductivity.)
1—logarithmic mean (This is most appropriate for confined aquifers with gradually varying transmissivities.)
2—arithmetic mean of saturated thickness and logarithmic-mean hydraulic conductivity.  (This is most appropriate for unconfined aquifers with gradually varying transmissivities.)

Data Set 4

CHANI—contains a value for each layer that is a flag or the horizontal anisotropy. If CHANI is less than or equal to 0, then variable HANI defines horizontal anisotropy. If CHANI is greater than 0, then CHANI is the horizontal anisotropy for the entire layer, and HANI is not read. If any HANI parameters are used, CHANI for all layers must be less than or equal to 0. Use as many records as needed to enter a value of CHANI for each layer. The horizontal anisotropy is the ratio of the hydraulic conductivity along columns (the Y direction) to the hydraulic conductivity along rows (the X direction).

Data Set 5

LAYVKA—contains a flag for each layer that indicates whether variable VKA is vertical hydraulic conductivity or the ratio of horizontal to vertical hydraulic conductivity. Use as many records as needed to enter a value for each layer.

0—indicates VKA is vertical hydraulic conductivity
not 0—indicates VKA is the ratio of horizontal to vertical hydraulic conductivity, where the horizontal hydraulic conductivity is specified as HK in item 10.

Data Set 6

LAYWET—contains a flag for each layer that indicates if wetting is active. Use as many records as needed to enter a value for each layer.

0—indicates wetting is inactive
not 0—indicates wetting is active

Data Set 7

[WETFCT IWETIT IHDWET]

(Include item 7 only if LAYWET indicates at least one wettable layer.)

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. (See IHDWET.)

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

IHDWET—is a flag that determines which equation is used to define the initial head at cells that become wet:

If IHDWET = 0, equation 33A is used:

h = BOT + WETFCT (hn - BOT) .

(hn is the head in the neighboring cell that is causing the dry cell to convert to an active cell.)

If IHDWET is not 0, equation 33B is used:

h = BOT + WETFCT(THRESH) .

Repeat Items 8-9 for each parameter to be defined (that is, NPLPF times).

Data Set 8

[PARNAM PARTYP Parval NCLU]

PARNAM—is the name of a parameter to be defined. This name can consist of 1 to 10 characters and is not case sensitive. That is, any combination of the same characters with different case will be equivalent.

All parameter names must be unique.

PARTYP—is the type of parameter to be defined. For the LPF Package, the allowed parameter types are:

HK—defines variable HK, horizontal hydraulic conductivity

HANI—defines variable HANI, horizontal anisotropy

VK—defines variable VKA for layers for which VKA represents vertical hydraulic conductivity (LAYVKA=0)

VANI—defines variable VKA for layers for which VKA represents vertical anisotropy (LAYVKA0)

SS—defines variable Ss, the specific storage. However, when the STORAGECOEFFICIENT option is used, Ss is confined storage coefficient.

SY—defines variable Sy, the specific yield

VKCB—defines variable VKCB, the vertical hydraulic conductivity of a Quasi-three-dimensional confining layer.

Parval—is the parameter value. This parameter value may be overridden by a value in the PVAL file.

NCLU—is the number of clusters required to define the parameter. Each repetition of Item 9 is a cluster (variables Layer, Mltarr, Zonarr, and IZ). There is usually only one cluster for each layer that is associated with a parameter. For example, if the parameter applies to cells in a single layer, there will generally be just one cluster. However, it is acceptable to have more than one cluster for the same layer.

Data Set 9

[Layer Mltarr Zonarr IZ]

Each repetition of Item 9 is called a parameter cluster. Repeat Item 9 NCLU times.

Layer—is the layer number to which a cluster definition applies.

Mltarr—is the name of the multiplier array to be used to define variable values that are associated with a parameter. The name “NONE” means that there is no multiplier array, and the variable values will be set equal to Parval.

Zonarr—is the name of the zone array to be used to define the cells that are associated with a parameter. The name “ALL” means that there is no zone array, and all cells in the specified layer are part of the parameter.

IZ—is up to 10 zone numbers (separated by spaces) that define the cells that are associated with a parameter. These values are not used if ZONARR is specified as “ALL”. Values can be positive or negative, but 0 is not allowed. The end of the line, a zero value, or a non-numeric entry terminates the list of values.

A subset of the following two-dimensional variables is used to describe each layer. All the variables that apply to layer 1 are read first, followed by layer 2, followed by layer 3, and so forth. If a variable is not required due to simulation options (for example, Ss and Sy for a completely steady-state simulation), then it must be omitted from the input file.

These variables are either read by the array-reading utility module, U2DREL, or they are defined through parameters. If a variable is defined through parameters, then the variable itself is not read; however, a single record containing a print code is read in place of the array control record. The print code determines the format for printing the values of the variable as defined by parameters. The print codes are the same as those used in an array control record. If any parameters of a given type are used, parameters must be used to define the corresponding variable for all layers in the model.

Data Set 10

HK(NCOL,NROW)- U2DREL

If there are any HK parameters, read only a print code.

HK—is the hydraulic conductivity along rows. HK is multiplied by horizontal anisotropy (see CHANI and HANI) to obtain hydraulic conductivity along columns.

Data Set 11

[HANI(NCOL,NROW)]- U2DREL

Include item 11 only if CHANI is less than or equal to 0. If there are any HANI parameters, read only a print code.

HANI—is the ratio of hydraulic conductivity along columns to hydraulic conductivity along rows, where HK of item 10 specifies the hydraulic conductivity along rows. Thus, the hydraulic conductivity along columns is the product of the values in HK and HANI. Read only if CHANI < 0.

Data Set 12

VKA(NCOL,NROW)- U2DREL

If there are any VK or VANI parameters, read only a print code.

VKA—is either vertical hydraulic conductivity or the ratio of horizontal to vertical hydraulic conductivity depending on the value of LAYVKA.

If LAYVKA is 0, VKA is vertical hydraulic conductivity.
If LAYVKA is not 0, VKA is the ratio of horizontal to vertical hydraulic conductivity. In this case, HK is divided by VKA to obtain vertical hydraulic conductivity, and values of VKA typically are greater than or equal to 1.0.

Data Set 13

[Ss(NCOL,NROW)]- U2DREL

Include item 13 only if at least one stress period is transient. If there are any SS parameters, read only a print code.

Ss—is specific storage unless the STORAGECOEFFICIENT option is used. When STORAGECOEFFICIENT is used, Ss is confined storage coefficient. Read only for a transient simulation (at least one transient stress period).

Data Set 14

[Sy(NCOL,NROW)]- U2DREL

Include item 14 only if at least one stress period is transient and LAYTYP is not 0. If there are any SY parameters, read only a print code.

Sy—is specific yield. Read only for a transient simulation (at least one transient stress period) and if the layer is convertible (LAYTYP is not 0).

Data Set 15

[VKCB(NCOL,NROW)]- U2DREL

Include item 15 only if LAYCBD (in the Discretization File) is not 0. If there are any VKCB parameters, read only a print code.

VKCB—is the vertical hydraulic conductivity of a Quasi-three-dimensional confining bed below a layer. Read only if there is a confining bed. Because there cannot be a confining bed beneath the bottom layer, VKCB cannot be specified for the bottom layer.

Data Set 16

[WETDRY(NCOL,NROW)]- U2DREL

Include item 16 only if LAYWET is not 0 and LAYTYP is not 0.

WETDRY—is a combination of the wetting threshold and a flag to indicate which neighboring cells can cause a cell to become wet.

If WETDRY < 0, only the cell below a dry cell can cause the cell to become wet.
If WETDRY > 0, the cell below a dry cell and the four horizontally adjacent cells can cause a cell to become wet.
If WETDRY is 0, the cell cannot be wetted.

The absolute value of WETDRY is the wetting threshold. When the sum of BOT and the absolute value of WETDRY at a dry cell is equaled or exceeded by the head at an adjacent cell, the cell is wetted. Read only if LAYTYP is not 0 and LAYWET is not 0.

The Lake package requires that WETDRY be set to 0 in Lakes.