Online Guide to MODFLOW-LGR

LVDA - Model-Layer Variable-Direction Horizontal Anisotropy Capability

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LVDA - Model-Layer Variable-Direction Horizontal Anisotropy Capability

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LVDA - Model-Layer Variable-Direction Horizontal Anisotropy Capability

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Abbreviation in Name file

LVDA

Purpose

The LVDA capability allows the principal directions of horizontal anisotropy to be different than the model-grid row and column directions, and for the directions to vary on a cell-by-cell basis within model layers.

Documentation

Anderman, E.R., Kipp, K.L., Hill, M.C., Valstar, Johan, and Neupauer, R.M., 2002, MODFLOW-2000, the U.S. Geological Survey modular ground-water model -- Documentation of the Model-Layer Variable-Direction Horizontal Anisotropy (LVDA) capability of the Hydrogeologic-Unit Flow (HUF) Package: U.S. Geological Survey Open-File Report 02-409, 60 p.

Supported in
•MODFLOW-2000
•MODFLOW-2005
•MODFLOW-LGR
•MODFLOW-NWT
•MODFLOW-OWHM

Other Notes
•The "Model-Layer Variable-Direction Horizontal Anisotropy" capability is provided in the LVDA input file but is part of the Hydrogeologic-Unit Flow package (HUF2).
•The "Model-Layer Variable-Direction Horizontal Anisotropy" capability is incompatible with the Horizontal Flow Barrier (HFB) package.
•The "Model-Layer Variable-Direction Horizontal Anisotropy" capability is incompatible with the Sensitivity (SEN) process when convertible layers are used.

Input Instructions

The LVDA capability is a modification to the existing Hydrogeologic-Unit Flow (HUF) Package (Anderman and Hill, 2000). This section describes the new input file needed with the LVDA capability and the changes in the HUF Package output files resulting from using the LVDA capability. There are no changes in the HUF Package output files if the LVDA capability is not used. Although the HUF input file is not changed when using the LVDA capability, the definition of two parameter types does change. The new definitions are presented below.

Printing of the LVDA model layer arrays is not supported by the print capability represented by item 12 of the HUF Package input file. Printing these arrays requires use of the new printing capability for the HUF Package documented by Anderman and Hill (in review).

Input for the Model-Layer Variable-Direction Horizontal Anisotropy capability is read from the file that has type “LVDA” in the Name file. Free format is used for reading all values. This file defines the horizontal anisotropy direction for each cell of the finite-difference grid.

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 (up to 199 characters) that starts in column 2. Any characters can be included in Text. The “#” character must be in column 1. Text is printed when the file is read.

Data Set 1

NPLVDA – is the number of LVDA parameters.

In MODFLOW-2005,-LGR, and -CFP the maximum number of allowed parametersis 2000.

Repeat Items 2 and 3 for each parameter to be defined (that is, NPLVDA times).

Data Set 2

PARNAM PARTYP Parval NCLU

PARNAM – is the name of a parameter to be defined. This name can consist of up to 10 characters and is not case sensitive. All parameter names must be unique.

PARTYP – is the parameter type to be defined. For the LVDA capability, the only allowed parameter type is:

•LVDA - defines the angle between the grid axis and the principal direction of horizontal hydraulic conductivity. Angle is positive in a clockwise direction with the positive x direction being zero. The angle can vary between –90 and 90 degrees. Hydraulic conductivity along the principal axis (Kmax of figure 2) is defined in the HUF Package input file by an HK parameter; the hydraulic conductivity along the minor axis (Kmin of figure 2) axis is defined by a HANI parameter in conjunction with the HK parameter. Using the LVDA capability, HANI values need to be less than or equal to 1.

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 Item-3 record is a cluster (variables Layer, Mltarr, Zonarr, and IZ).

Data Set 3

Layer Mltarr Zonarr IZ

Each Item 3 record is called a parameter cluster. Repeat Item 3 NCLU times.

Layer – is the layer to which the direction applies.

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

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

IZ – is up to 10 zone numbers (separated by spaces) that define the array elements that are associated with a parameter. The first zero or non-numeric value terminates the list. These values are not used if Zonarr is specified as “ALL”.