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Online Guide to MODFLOW

Navigation: Groundwater Flow Process > Subsidence

SWT - Subsidence and Aquifer-System Compaction Package for Water-Table Aquifers

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Abbreviation in Name file

SWT

Purpose

SWT simulates vertical compaction in models of regional groundwater flow. The program simulates groundwater storage changes and compaction in discontinuous interbeds or in extensive confining units, accounting for stress-dependent changes in storage properties. Several features of the program make it useful for application in shallow, unconfined flow systems. Geostatic stress can be treated as a function of water-table elevation, and compaction is a function of computed changes in effective stress at the bottom of a model layer. Thickness of compressible sediments in an unconfined model layer can vary in proportion to saturated thickness.

Documentation

Leake, S.A., and Galloway, D.L., 2007, MODFLOW ground-water model -- User guide to the Subsidence and Aquifer-System Compaction Package (SUB-WT) for Water-Table Aquifers: U.S. Geological Survey Techniques and Methods, Book 6, Chap. A23, 42 p.

Related Packages

Interbed Storage package

Subsidence package

Supported in

MODFLOW-2000

MODFLOW-2005

MODFLOW-LGR

MODFLOW-CFP

MODFLOW-NWT

MODFLOW-OWHM

Other Notes

See the Frequently Asked Questions for information on how to read data from binary files generated by MODFLOW.

Input for the SUB-WT Package is read from the file that has the type “SWT” in the name file. Optional variables are shown in brackets. All single-valued variables in data items 1, 3, 16, and 17, and layer assignments for systems of interbeds in data item 2 are read in free format. Data items 1, 2, 3, and 16 consist of, at most, one record. Two-dimensional arrays in data items 4–15 are read with MODFLOW utility array readers U2DREL. For instructions on use of array readers, refer to Harbaugh and others (2000) or Harbaugh (2005).

FOR EACH SIMULATION

Data Set 0

[#Text]

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

Data Set 1

ISWTCB ISWTOC NSYSTM ITHK IVOID ISTPCS ICRCC

Data Set 2

LNWT(NSYSTM)

(Enter NSYSTM integers separated by one or more spaces or by commas.)

Data Set 3

IZCFL IZCFM IGLFL IGLFM IESTFL IESTFM IPCSFL IPCSFM ISTFL ISTFM

Data Set 4

GL0(NCOL,NROW) U2DREL

Data Set 5

SGM(NCOL,NROW) U2DREL

Data Set 6

SGS(NCOL,NROW) U2DREL

The arrays in data items 7–13 are read for each of NSYSTM systems of interbeds. Read all arrays for system 1 first, then all arrays for system 2, and so on for each system.

Data Set 7

THICK(NCOL,NROW) U2DREL

Data Set 8

Sse(NCOL,NROW) U2DREL if ICRCC0

Data Set 9

Ssv(NCOL,NROW) U2DREL if ICRCC0

Data Set 10

Cr(NCOL,NROW) U2DREL if ICRCC=0

Data Set 11

Cc(NCOL,NROW) U2DREL if ICRCC=0

Data Set 12

VOID(NCOL,NROW) U2DREL

Data Set 13

SUB(NCOL,NROW) U2DREL

The arrays in data items 14 and 15 are read for each of NLAY model layers. Depending on the value of ISTPCS, read item 14 or item 15 sequentially from layer 1 to layer NLAY.

Data Set 14

[PCSOFF(NCOL,NROW)] U2DREL if ISTPCS 0

Data Set 15

[PCS(NCOL,NROW)] U2DREL if ISTPCS = 0

Data Set 16

[Ifm1 Iun1 Ifm2 Iun2 Ifm3 Iun3 … Ifm13 Iun13] if ISWTOC > 0

(Data item 16 consists of one record with 26 integers separated by one or more spaces or by commas.)

Data Set 17

[ISP1 ISP2 ITS1 ITS2 Ifl1 Ifl2 Ifl3 … Ifl26] if ISWTOC > 0

(Data item 17 consists of ISWTOC records with 30 integers separated by one or more spaces or by commas. See the section entitled “Package Output” for a detailed explanation of the use of data item 17.

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