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Online Guide to MODFLOW

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Array Reading Utility Modules

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Purpose

The Array Reading Utility Modules are used to read arrays of data in a variety of packages.

Documentation

Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, M.G., 2000, MODFLOW-2000, the U.S. Geological Survey modular ground-water model -- User guide to modularization concepts and the Ground-Water Flow Process: U.S. Geological Survey Open-File Report 00-92, 121 p.

Other Notes

The Array Reading Utility Modules are never used independently from packages so they do not have a separate symbol in the name file.

Input Instructions

The array reading utility modules provide a common way for all packages to read variables that have multiple values. The term “array” is simply a programming term for a variable that contains multiple values. There are three modules: U2DREL, U2DINT, and U1DREL. U2DREL reads real two-dimensional variables, U2DINT reads integer two-dimensional variables, and U1DREL reads real one-dimensional variables. All of these modules work similarly. They read one array-control record and, optionally, a data array in a format specified on the array-control record. Several alternate structures for the control record are provided. The original fixed-format control records work as documented in McDonald and Harbaugh (1988), and four free-format versions have been added. The free-format versions are described first because they are easier to use.

FREE-FORMAT CONTROL RECORDS FOR ARRAY READERS:

Values in bold italics are keywords that can be specified as uppercase or lowercase. Each control record is limited to a length of 199 characters.

For each array, specify the values for the array using one of the four methods below.

Data Set 1

CONSTANT CNSTNT

All values in the array are set equal to CNSTNT.

Data Set 2

INTERNAL CNSTNT FMTIN IPRN

The individual array elements will be read from the same file that contains the control record.

Data Set 3

EXTERNAL Nunit CNSTNT FMTIN IPRN

The individual array elements will be read from the file unit number specified by Nunit. The name of the file associated with this file unit must be contained in the name file.

Data Set 4

OPEN/CLOSE FNAME CNSTNT FMTIN IPRN

The array will be read from the file whose name is specified by FNAME. This file will be opened on unit 99 just prior to reading the array and closed immediately after the array is read. This file should not be included in the name file. A file that is read using this control record can contain only a single array. The OPEN/CLOSE option is particularly useful for running simulations that require more than 99 files using a computer that allows only 99 files to be opened simultaneously.

FIXED-FORMAT CONTROL RECORD FOR ARRAY READERS:

Data Set 1

A fixed-format control record contains the following variables:

LOCAT CNSTNT FMTIN IPRN

These variables are explained below. LOCAT, CNSTNT, and IPRN are 10-character numeric fields. For U2DREL and U1DREL, CNSTNT is a real number. For U2DINT, CNSTNT is an integer and must not include a decimal. FMTIN is a 20-character text field. All four variables are always read when the control record is fixed format; however, some of the variables are unused in some situations. For example when LOCAT = 0, FMTIN and IPRN are not used.

Table of IPRN Values

IPRN

U2DREL

U2DINT

U1DREL

0

10G11.4

10I11

10G12.5

1

11G10.3

60I1

5G12.5

2

9G13.6

40I2

 

3

15F7.1

30I3

 

4

15F7.2

25I4

 

5

15F7.3

20I5

 

6

15F7.4

10I11

 

7

20F5.0

25I2

 

8

20F5.1

15I4

 

9

20F5.2

10I6

 

10

20F5.3

 

 

11

20F5.4

 

 

12

10G11.4

 

 

13

10F6.0

 

 

14

10F6.1

 

 

15

10F6.2

 

 

16

10F6.3

 

 

17

10F6.4

 

 

18

10F6.5

 

 

19

5G12.5

 

 

20

6G11.4

 

 

21

7G9.2

 

 

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