FOR EACH SIMULATION
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Data Set 0
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[#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.
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Data Set 1a
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[ PARAMETER NPGHB MXL]
This optional item must start with the word “PARAMETER”.
MXL—is the maximum number of general-head-boundary cells that will be defined using parameters. MXL must equal or exceed the sum of NLST×N for all parameters, where N is the greater of 1 and NUMINST.
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Data Set 1b-1 (MODFLOW-OWHM only)
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[TABFILE NTAB FILEIO TIMEOPTION]
TABFILE is a keyword that triggers reading subsequent tabfile information.
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NTAB is the number of tabfiles that will be read.
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FILIO is a flag that determines if the tabfile is loaded entirely into memory or if only the portion that pertains to the current timestep is read in. If FILEIO is set to 0, then the entire tabfile is loaded into memory. If it is set to a nonzero value, then only the portion of the tabfile that pertains to the current time step is loaded into memory.
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TIMEOPTION is a required flag that must be one of the two following keywords.
| • | SIMTIME The keyword “SIMTIME” (without quotes) specifies that tabfile times use the model simulated time with time units specified by the DIS and a starting point of 0. This is the default operation and will occur if TIMEOPTION is not specified. |
| • | REALTIME The keyword “REALTIME” (without quotes) specifies that tabfile times use decimal years that begin with the date specified in the DIS with the keyword STARTTIME. IF STARTTIME is not specified in the DIS, then MODFLOW will raise an error message and stop the program. |
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Data Set 1b-2 (MODFLOW-OWHM only)
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[TABNAM TABLOCATION]
READ NTAB TIMES IF NTAB>0
TABNAM is a unique name (max of 20 characters) that identifies the tabfile. It is also used to link a model feature (i.e. layer, row, and column) to a specific tabfile.
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TABLOCATION is either the path and filename (relative or absolute) of the tabfile or is the keyword “EXTERNAL” followed by a unit number. The unit number must refer to the tabfile that is opened by the Name file. The tabfile is self-counted, stored, and associated with the unique ID TABNAM.
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Data Set 2
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MXACTB IGHBCB [Option]
MXACTB—is the maximum number of general-head boundary cells in use during any stress period. MXACTB includes cells that are defined using parameters as well as cells that are defined without using parameters.
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IGHBCB—is a flag and a unit number.
| • | If IGHBCB > 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. |
| • | If IGHBCB = 0, cell-by-cell flow terms will not be written. |
| • | If IGHBCB < 0, boundary leakage for each GHB cell will be written to the listing file when "SAVE BUDGET" or a non-zero value for ICBCFL is specified in Output Control. |
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Option—is an optional list of character values.
| • | “AUXILIARY abc” or “AUX abc”—defines an auxiliary variable, named "abc", which will be read for each general-head boundary as part of Items 4 and 6. Up to 20 variables can be specified, each of which must be preceded by "AUXILIARY" or "AUX." These variables will not be used by the Groundwater Flow Process, but they will be available for use by other processes. The auxiliary variable values will be read after the Cond variable. |
Auxiliary parameters are used with MODPATH and the Groundwater Transport process. In MODPATH, the variable IFACE is specified with an auxiliary parameter. In the Groundwater Transport process, concentration is specified with an auxiliary parameter. The option COMPACT BUDGET AUXILIARY must be used in the Output Control when IFACE is used for MODPATH.
| • | “CBCALLOCATE” or “CBC”—indicates that memory should be allocated to store cell-by-cell flow for each general-head boundary in order to make these flows available for use in other packages. (This option is only available in MODFLOW-2000.) |
| • | NOPRINT—suppresses the printing of cell lists. |
| • | TABPRINT The keyword "TABPRINT” (without quotes) will produce a detailed output of the tabfile information that is applied at each time step to the list file. This option is only available in MODFLOW-OWHM. |
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Repeat Items 3 and 4 for each NPGHB parameter.
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Data Set 3
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[PARNAM PARTYP Parval NLST [INSTANCES NUMINST]]
If PARNAM is to be a time-varying parameter, the keyword “INSTANCES” and a value for NUMINST must be entered.
PARNAM—is the name of a parameter. 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.
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PARTYP—is the type of parameter to be defined. For the GHB Package, the only allowed parameter type is GHB, which defines values of the general-head boundary hydraulic conductance.
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NLST—is the number of head-dependent boundary cells that are included in a non-time-varying parameter or in each instance of a time-varying parameter.
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INSTANCES – is an optional keyword that designates a parameter as time varying. The keyword is case-insensitive; that is, it may be entered in any combination of upper- and lower-case letters. If INSTANCES is present, it must be followed by a value for NUMINST. If INSTANCES is absent, PARNAM is non-time-varying and NUMINST should not be present.
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NUMINST – is the number of instances that are included in the definition of a time-varying parameter, where each instance is a list of general-head boundary cells and associated properties. If the keyword INSTANCES is present, NUMINST must be present and must be at least 1. If the keyword INSTANCES is absent, NUMINST should not be present.
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Data Set 4a
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INSTNAM
Item 4a is read only if PARNAM is time-varying. NUMINST repetitions of Item 4 (parts a and b) are read. After each repetition of Item 4a, NLST repetitions of Item 4b are read.
INSTNAM – is the name of an instance associated with the parameter PARNAM specified in the corresponding Item 3. The 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. Names entered for INSTNAM must be unique for any given parameter, but names may be reused for instances associated with different parameters.
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Data Set 4b
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Layer Row Column Bhead Condfact [xyz] [TABNAM TSFAC]
NLST repetitions of Item 4b are required; they are read by module ULSTRD. (SFAC of the ULSTRD utility module applies to Condfact). The NLST repetitions of Item 4b follow each repetition of Item 4a when PARNAM is time-varying.
Layer—is the layer number of the cell affected by the head-dependent boundary.
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Row—is the row number of the cell affected by the head-dependent boundary.
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Column—is the column number of the cell affected by the head-dependent boundary.
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Bhead—is the head on the boundary.
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Condfact—is the factor used to calculate hydraulic conductance from the parameter value. The conductance is the product of Condfact and the parameter value.
See also "What is conductance?"
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[xyz]—represents any auxiliary variables for a boundary that have been defined in Item 2. The auxiliary variables must be present in each repetition of Items 4 and 6 if they are defined in item 2.
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TABNAM is a unique name (max of 20 characters) that identifies the tabfile. It is also used to link segments to a specific tabfile.
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TSFAC is a feature’s scale factor. This factor is multiplied with the tabfile value before it is applied to a feature.
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TABNAME and TSFAC are only available in MODFLOW-OWHM.
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FOR EACH STRESS PERIOD
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Data Set 5
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ITMP NP
ITMP—is a flag and a counter.
| • | If ITMP < 0, non-parameter GHB data from the preceding stress period will be reused. |
| • | If ITMP ≥ 0, ITMP is the number of non-parameter general-head boundaries read for the current stress period. |
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NP—is the number of parameters in use in the current stress period.
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Data Set 6
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Layer Row Column Bhead Cond [xyz] [TABNAM TSFAC]
ITMP repetitions of Item 6 are read by module ULSTRD if ITMP > 0. (SFAC of the ULSTRD utility module applies to Cond.) Item 6 is not read if ITMP is negative or 0.
Layer—is the layer number of the cell affected by the head-dependent boundary.
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Row—is the row number of the cell affected by the head-dependent boundary.
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Column—is the column number of the cell affected by the head-dependent boundary.
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Bhead—is the head on the boundary.
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Cond—is the hydraulic conductance of the interface between the aquifer cell and the boundary.
See also "What is conductance?"
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[xyz]—represents any auxiliary variables for a boundary that have been defined in Item 2. The auxiliary variables must be present in each repetition of Items 4 and 6 if they are defined in item 2.
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TABNAM is a unique name (max of 20 characters) that identifies the tabfile. It is also used to link segments to a specific tabfile.
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TSFAC is a feature’s scale factor. This factor is multiplied with the tabfile value before it is applied to a feature.
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TABNAME and TSFAC are only available in MODFLOW-OWHM.
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Data Set 7
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[Pname [Iname]]
Item 7 is repeated NP times. It is not read if NP is negative or 0. Iname is read if Pname is a time-varying parameter.
Pname—is the name of a parameter that is being used in the current stress period. NP parameter names will be read.
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Iname – is an instance name that is read only if Pname is a time-varying parameter. Multiple instances of the same time-varying parameter are not allowed in a stress period.
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