KDEP - Hydraulic-Conductivity Depth-Dependence Capability

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Abbreviation in Name file

KDEP

Purpose

Hydraulic-Conductivity Depth-Dependence Capability allow the horizontal hydraulic conductivity of hydrogeologic units to vary with depth using an exponential decay function. The vertical hydraulic conductivity changes accordingly if specified using vertical-anisotropy (VANI) parameters.

Documentation

Anderman, E.R., and Hill, M.C., 2003, MODFLOW-2000, the U.S. Geological Survey modular ground-water model -- Three additions to the Hydrogeologic-Unit Flow (HUF) Package: Alternative storage for the uppermost active cells, Flows in hydrogeologic units, and the Hydraulic-conductivity depth-dependence (KDEP) capability: U.S. Geological Survey Open-File Report 03-347, 36 p.

Supported in

•MODFLOW-2000

•MODFLOW-2005

•MODFLOW-LGR

•MODFLOW-NWT

•MODFLOW-OWHM

Other Notes

•The "Hydraulic-Conductivity Depth-Dependence" capability is provided in the KDEP input file but is part of the Hydrogeologic-Unit Flow package (HUF2).

The depth-dependence capability is a modification to the existing HUF Package (Anderman and Hill, 2000). This section describes the new input file needed with the depth-dependence capability and the changes in the HUF Package output files resulting from using the depth-dependence capability. There are no changes in the HUF Package output files if the depth-dependence capability is not used.

Input Instructions

Input for the Hydraulic-Conductivity Depth-Dependence capability is read from the file that has type “KDEP” in the Name file. Free format is used for reading all values.

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

NPKDEP IFKDEP

NPKDEP – is the number of depth-dependence parameters.

In MODFLOW-2000, the maximum number of allowed parameters is 999.  In MODFLOW-2005,-LGR, and -CFP the maximum number of allowed parametersis 2000. In MODFLOW-OWHM, the maximum number of allowed parameters is specified in the Basic package.

IFKDEP – is a flag indicating the source of the array specifying reference-surface elevation.

•0 – the TOP array specified in the Discretization Package Input File will be used.

•> 0 – an array will be specified in Item 2.

Data Set 2

RS(NCOL,NROW)- U2DREL

Include Item 2 only if IFKDEP is greater than 0. Item 2 is read using the array-reading utility module U2DREL (Harbaugh and others, 2000, p. 86-88).

RS – is the elevation of the reference surface to be used to calculate the depth.

Repeat Items 3 and 4 for each parameter to be defined (that is, NPKDEP times).

Data Set 3

PARNAM PARTYP Parval NCLU

PARNAM – is the name of a depth-dependence 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 type of parameter to be defined. For the depth-dependence capability, the only allowed parameter type is:

•KDEP – defines the depth-dependence coefficient used to modify horizontal hydraulic conductivity with depth for the hydrogeologic unit(s) specified in Item 4. NOTE: horizontal hydraulic conductivity is only modified for cells in units defined by depth-dependence parameters and not for other cells, so depth-dependence parameters do not need to be specified for the entire model.

Parval—is the parameter value. This parameter value may be overridden by a value in the PVAL file, the Sensitivity Process (SEN) input file, or by a value generated by the Parameter-Estimation (PES) Process.

NCLU – is the number of clusters required to define the parameter. Each Item-4 record is a cluster (variables HGUNAM, Mltarr, Zonarr, and IZ).

Data Set 4

HGUNAM Mltarr Zonarr IZ

Each Item 4 record is called a parameter cluster. Repeat Item 4 NCLU times.

HGUNAM – is the hydrogeologic unit to which the parameter 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 the zone 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”.