The input variables for MODFLOW 6 are described using a customized format that allows us to build input instructions in a variety of different ways. Each input variable is described using multiple definition attributes. These attributes are stored in definition files, with one definition file for each MODFLOW 6 input file. A python script, also present in this folder mf6ivar.py, is used to convert the definition files into a markdown file ./md/mf6ivar.md and latex files that are pulled into the user guide.
A MODFLOW 6 variable, and its place within a block and on a line is defined using variable definition attributes. Some of the attributes are optional and do not need to be specified (because they have a default value) and others are required. The following list defines the variable definition attributes:
- block -- this is the name of the block that contains the variable. Required.
- name -- this is the name of the variable. Required.
- type -- this is the type of variable. Valid values are: keyword, string, integer, double precision, recarray, record, recordrepeating, keystring. Required.
- valid -- list of valid values or keywords
- shape -- this is the size of the array. Only required for arrays. Optional.
- tagged -- if set to false, then a keyword is not required prior to value itself. tagged is set to true if not specified. Optional.
- in_record -- if true, then this means that the variable is part of a record, and so it should not be listed on its own line. in_record is False if not specified. Optional.
- layered -- if true, then the LAYERED keyword will be written to the input instructions. Default is false.
- reader -- this is the MODFLOW 6 subroutine or method that reads the data. Valid values are: urword, u1ddbl, u2ddbl, readarray.
- optional -- this is a logical keyword. When true, the variable is an optional variable for MODFLOW 6. Optional.
- longname -- this is a long name for the variable. Required.
- description -- this is a written description of the variable. Required.
- preserve_case -- default is false, but should be set to true for file names
- default_value -- default value for the variable. Should be executable with Python
- numeric_index -- default is false. if true, then this is an index variable. Is useful for Flopy to treat as zero-based.
- deprecated -- default is ''. if not '' then this MODFLOW 6 variable is considered deprecated. The string for deprecated should be the version (such as 6.1.1) that corresponds to when the option was deprecated.
Definition files contain all the information necessary to construct all of the blocks and variables for a MODFLOW 6 input file. A '#' symbol can be used to insert a comment anywhere within the definition file. These comments are used here to separate the definition files into parts for each block.
The .dfn files are located in the dfn folder.
For your definition file to work with flopy:
- Follow the file naming convention <model abbr>-<package abbr>.dfn.
- When your package is ready for release copy the dfn file to the flopy distribution in the flopy/mf6/data/dfn folder, run createpackages.py, and check in your new dfn file. Also check in the package class and the updated _init_.py that createpackages.py created.
A subpackage is a package referenced by another package (vs being referenced in the name file). The tas, ts, and obs packages are examples of subpackages. There are a few additional steps required when creating a subpackage definition file. First, verify that the parent package's dfn file has a file record for the subpackage to the option block. For example, for the time series package the file record definition starts with:
block options
name ts_filerecord
type record ts6 filein ts6_filename
Verify that the same naming convention is followed as the example above, specifically:
name <subpackage-abbr>_filerecord
record <subpackage-abbr>6 filein <subpackage-abbr>6_filename
Next, create the child package definition file (see sections below for more information).
When your child package is ready for release follow the same procedure described in "Creating a Definition File that will Work with Flopy" above along with a few additional steps required for subpackages. At the top of the child dfn file add two lines describing how the parent and child packages are related. The first line determines how the subpackage is linked to the package:
# flopy subpackage <parent record> <abbreviation> <child data> <data name>
- Parent record is the MF6 record name of the filerecord in parent package that references the child packages file name
- Abbreviation is the short abbreviation of the new subclass
- Child data is the name of the child class data that can be passed in as parameter to the parent class. Passing in this parameter to the parent class automatically creates the child class with the data provided.
- Data name is the parent class parameter name that automatically creates the child class with the data provided.
The example below is the first line from the ts subpackage dfn:
# flopy subpackage ts_filerecord ts timeseries timeseries
The second line determines the variable name of the subpackage's parent and the type of parent (the parent package's object oriented parent):
# flopy parent_name_type <parent package variable name> <parent package type>
An example below is the second line in the ts subpackage dfn:
# flopy parent_name_type parent_package MFPackage
There are three possible types (or combination of them) that can be used for "parent package type", MFPackage, MFModel, and MFSimulation. If a package supports multiple types of parents (for example, it can be either in the model namefile or in a package, like the obs package), include all the types supported, seperating each type with a / (MFPackage/MFModel).
To create a new type of model choose a unique three letter model abbreviation ("gwf", "gwt", ...). Create a name file dfn with the naming convention <model abbr>-nam.dfn. The name file must have only an options and packages block (see gwf-nam.dfn as an example). Create a new dfn file for each of the packages in your new model, following the naming convention described above.
When your model is ready for release copy the dfn file to the flopy distribution in the flopy/mf6/data/dfn folder, run createpackages.py, and check in your new dfn files, the package classes, and updated init.py that createpackages.py created.
This example shows how to construct an options block with a couple of optional keywords.
# --------------------- gwf dis options ---------------------
block options
name length_units
type string
reader urword
optional true
longname model length units
description is the length units used for this model. Values can be ``FEET'', ``METERS'', or ``CENTIMETERS''. If not specified, the default is ``UNKNOWN''.
block options
name nogrb
type keyword
reader urword
optional true
longname do not write binary grid file
description keyword to deactivate writing of the binary grid file.
This information will be converted into an ASCII representation of the options block as follows:
BEGIN OPTIONS
[LENGTH_UNITS length_units]
[NOGRB]
END OPTIONS
In addition, a latex file will be created. The name of the latex file will be the prefix of the definition file plus -desc.tex. This latex file will have the descriptions, written in latex, for the variables in the definition file.
% DO NOT MODIFY THIS FILE DIRECTLY. IT IS CREATED BY mf6ivar.py
\item \texttt{length\_units}---is the length units used for this model. Values can be ``FEET'', ``METERS'', or ``CENTIMETERS''. If not specified, the default is ``UNKNOWN''.
\item \texttt{NOGRB}---keyword to deactivate writing of the binary grid file.
The variables will also be listed in the markdown file as:
| component | package | block | variable name | type | description |
|---|---|---|---|---|---|
| GWF | DIS | OPTIONS | LENGTH_UNITS | STRING | is the length units used for this model. Values can be FEET'', METERS'', or CENTIMETERS''. If not specified, the default is UNKNOWN''. |
| GWF | DIS | OPTIONS | NOGRB | KEYWORD | keyword to deactivate writing of the binary grid file. |
As shown in the simple example above, a keyword type is simply one that is specified using a text string. The keyword name is automatically converted into upper case. Upper case is used in the input instructions to indicate a word that is recognized by the MODFLOW 6 program.
A simple example of a keyword is:
# --------------------- gwf dis options ---------------------
block options
name nogrb
type keyword
reader urword
optional true
longname do not write binary grid file
description keyword to deactivate writing of the binary grid file.
which renders as,
BEGIN OPTIONS
[NOGRB]
END OPTIONS
Note that the optional tag being set to true results in square brackets around NOGRB.
As shown in the simple example above, a string type is simply a keyword followed by a text string. This type allows the user to provide text information to MODFLOW 6.
A simple example of a keyword is:
# --------------------- gwf dis options ---------------------
block options
name length_units
type string
reader urword
optional true
longname model length units
description is the length units used for this model. Values can be ``FEET'', ``METERS'', or ``CENTIMETERS''. If not specified, the default is ``UNKNOWN''.
which renders as,
BEGIN OPTIONS
[LENGTH_UNITS length_units]
END OPTIONS
Again the optional tag is used here to indicate that the keyword and string value are optional.
Though it wouldn't make sense in this context, we could also have set tagged to False. By doing so, we would have ended up with:
BEGIN OPTIONS
[length_units]
END OPTIONS
In this case, the user would provide length_units directly without a preceding keyword. Eliminating tags is used later to construct records consisting of multiple data entries.
As you might expect, the integer and double precision types allow for specification of integer and double precision input by the user. A simple example from the Solution Sparse Matrix Solver Nonlinear block is:
# --------------------- sln sms nonlinear ---------------------
block nonlinear
name outer_hclose
type double precision
reader urword
optional false
longname head change criterion
description real value defining the head change criterion for convergence of the outer (nonlinear) iterations, in units of length. When the maximum absolute value of the head change at all nodes during an iteration is less than or equal to \texttt{outer\_hclose}, iteration stops. Commonly, \texttt{outer\_hclose} equals 0.01.
block nonlinear
name outer_maximum
type integer
reader urword
optional false
longname outer maximum iterations
description integer value defining the maximum number of outer (nonlinear) iterations -- that is, calls to the solution routine. For a linear problem \texttt{outer\_maximum} should be 1.
This of course renders as:
BEGIN NONLINEAR
OUTER_HCLOSE outer_hclose
OUTER_MAXIMUM outer_maximum
END NONLINEAR
Note that in this case, both of the variables are required (optional false) and so they are not enclosed in brackets.
The recarray type is pattered after the recarray type that is available in the numpy package for Python.
An example of a recarray record is shown below for the drain package. First you'll note that the recarray has a shape. This shape is of maxbound, which is the maximum number of records that the user can enter. Also note that following the ``recarray'' identifier is cellid, elev, cond, aux, and boundname. These are all additional variables that are described after the recarray. Because these are listed next to recarray, the protocol as that they will all be listed on one line. You'll also note that the cellid, elev, cond, aux, and boundname variables have the in_record attribute set to true. This is required so that the variables are not written again after the recarray; they are only written inside the recarray. These variables all have the tagged attribute set to false so that they are not preceded by a keyword.
block period
name periodrecarray
type recarray cellid elev cond aux boundname
shape (maxbound)
reader urword
longname
description
block period
name cellid
type integer
shape (ncelldim)
tagged false
in_record true
reader urword
longname cell identifier
description REPLACE cellid {}
block period
name elev
type double precision
shape
tagged false
in_record true
reader urword
longname drain elevation
description is the elevation of the drain. If the Options block includes a TIMESERIESFILE entry (see the ``Time-Variable Input'' section), values can be obtained from a time series by entering the time-series name in place of a numeric value.
block period
name cond
type double precision
shape
tagged false
in_record true
reader urword
longname drain conductance
description is the hydraulic conductance of the interface between the aquifer and the drain. If the Options block includes a TIMESERIESFILE entry (see the ``Time-Variable Input'' section), values can be obtained from a time series by entering the time-series name in place of a numeric value.
block period
name aux
type double precision
in_record true
tagged false
shape (naux)
reader urword
optional true
longname auxiliary variables
description REPLACE aux {'{#1}': 'drain'}
block period
name boundname
type string
shape
tagged false
in_record true
reader urword
optional true
longname drain name
description REPLACE boundname {'{#1}': 'drain'}
When these lines are rendered, we get the following:
BEGIN PERIOD
cellid(ncelldim) elev cond [aux(naux)] [boundname]
cellid(ncelldim) elev cond [aux(naux)] [boundname]
...
END PERIOD
A record type is similar to the recarray type, except that it doesn't have a shape. A record can be just a list of values on one line. A simple example of this is in the SMS Linear block, where we have the rcloserecord consisting of the inner_rclose and rclose_option variables.
block linear
name rcloserecord
type record inner_rclose rclose_option
reader urword
optional false
longname rclose record
description
block linear
name inner_rclose
type double precision
in_record true
reader urword
optional false
longname flow residual tolerance
description real value that defines the flow residual tolerance for convergence of the SMS linear solver and specific flow residual criteria used. This value represents the maximum allowable residual at any single node. Value is in units of length cubed per time, and must be consistent with \mf length and time units. Usually a value of $1.0 \times 10^{-1}$ is sufficient for the flow-residual criteria when meters and seconds are the defined \mf length and time.
block linear
name rclose_option
type string
tagged false
in_record true
reader urword
optional true
longname flow residual tolerance
description an optional keyword that defines the specific flow residual criterion used. \texttt{L2NORM\_RCLOSE}--an optional keyword that is used to specify that \texttt{inner\_rclose} represents a L-2 Norm closure criteria instead of a infinity-Norm (absolute convergence criteria). When \texttt{L2NORM\_RCLOSE} is specified, a reasonable initial \texttt{inner\_rclose} value is $\left( 1.0 \times 10^{-1} \times \text{active nodes} \right)$ when meters and seconds are the defined \mf length and time. \texttt{RELATIVE\_RCLOSE}--an optional keyword that is used to specify that \texttt{inner\_rclose} represents a relative L-2 Norm reduction closure criteria instead of a infinity-Norm (absolute convergence criteria). When \texttt{RELATIVE\_RCLOSE} is specified, a reasonable initial \texttt{inner\_rclose} value is $1.0 \times 10^{-4}$ and convergence is achieved for a given inner (linear) iteration when $\Delta h \le$ \texttt{inner\_hclose} and the current L-2 Norm is $\le$ the product of the \texttt{RELATIVE\_RCLOSE} and the initial L-2 Norm for the current inner (linear) iteration. If \texttt{rclose\_option} is not specified, an absolute residual (infinity-norm) criterion is used.
This renders as the following. The inner_rclose variable is tagged by default and so the INNER_RCLOSE keyword precedes inner_rclose. The rclose_option variable has tagged set to false, and so there is no keyword preceding it. It also has optional set to true, and so there are square brackets around it.
BEGIN LINEAR
INNER_RCLOSE inner_rclose [rclose_option]
END LINEAR
The recordrepeating type is the same as the record type. We've given it another name to indicate that the user can specify more than on line. The only place this is used at present is in the Output Control.
A keystring is a final record type. A keystring identifies that a variable can specified using multiple different types of input. It is most often used by the advanced packages to adjust individual comments of the package. The following is an example of the mawsetting variable:
block period
name mawsetting
type keystring status flowing_wellrecord rate well_head head_limit shutoffrecord rate_scalingrecord auxiliaryrecord
shape
tagged false
in_record true
reader urword
longname
description line of information that is parsed into a keyword and values. Keyword values that can be used to start the \texttt{mawsetting} string include: \texttt{FLOWING\_WELL}, \texttt{RATE}, \texttt{WELL\_HEAD}, \texttt{HEAD\_LIMIT}, \texttt{SHUT\_OFF}, \texttt{RATE\_SCALING}, and \texttt{AUXILIARY}.
block period
name status
type string
shape
tagged true
in_record true
reader urword
longname well status
description keyword option to define well status. \texttt{status} can be \texttt{ACTIVE}, \texttt{INACTIVE}, or \texttt{CONSTANT}. By default, \texttt{status} is \texttt{ACTIVE}.
block period
name flowing_wellrecord
type record flowing_well fwelev fwcond
shape
tagged
in_record true
reader urword
longname
description
block period
name flowing_well
type keyword
shape
in_record true
reader urword
longname well is a flowing well
description keyword to indicate the well is a flowing well. The \texttt{flowing\_well} option can be used to simulate flowing wells when the simulated well head exceeds the specified drainage elevation.
block period
name fwelev
type double precision
shape
tagged false
in_record true
reader urword
longname flowing well elevation
description elevation used to determine whether or not the well is flowing.
block period
name fwcond
type double precision
shape
tagged false
in_record true
reader urword
longname well flowing well elevation
description elevation used to determine whether or not the well is flowing.
block period
name rate
type double precision
shape
tagged true
in_record true
reader urword
longname well pumping rate
description is the volumetric pumping rate for the multi-aquifer well. A positive value indicates recharge and a negative value indicates discharge (pumping). \texttt{rate} only applies to active (\texttt{IBOUND}$>0$) multi-aquifer wells. If the Options block includes a \texttt{TIMESERIESFILE} entry (see the ``Time-Variable Input'' section), values can be obtained from a time series by entering the time-series name in place of a numeric value. By default, the \texttt{rate} for each multi-aquifer well is zero.
block period
name well_head
type double precision
shape
tagged true
in_record true
reader urword
longname well head
description is the head in the multi-aquifer well. \texttt{well\_head} is only applied to constant head (\texttt{STATUS} is \texttt{CONSTANT}) and inactive (\texttt{STATUS} is \texttt{INACTIVE}) multi-aquifer wells.
block period
name head_limit
type string
shape
tagged true
in_record true
reader urword
longname head limit
description is the limiting water level (head) in the well, which is the minimum of the well \texttt{rate} or the well inflow rate from the aquifer. \texttt{head\_limit} is only applied to discharging wells (\texttt{rate}$<0$). \texttt{head\_limit} can be deactivated by specifying the text string `\texttt{off}'. By default, \texttt{head\_limit} is `\texttt{off}'.
block period
name shutoffrecord
type record shut_off minrate maxrate
shape
tagged
in_record true
reader urword
longname
description
block period
name shut_off
type keyword
shape
in_record true
reader urword
longname shut off well
description keyword for activating well shut off capability. Subsequent values define the minimum and maximum pumping rate that a well must exceed to shutoff or reactivate a well, respectively, during a stress period. \texttt{shut\_off} is only applied to discharging wells (\texttt{rate}$<0$) and if \texttt{head\_limit} is specified (not set to `\texttt{off}'). If \texttt{head\_limit} is specified, \texttt{shut\_off} can be deactivated by specifying a minimum value equal to zero. By default, \texttt{shut\_off} is not used.
block period
name minrate
type double precision
shape
tagged false
in_record true
reader urword
longname minimum shutoff rate
description is the minimum rate that a well must exceed to shutoff a well during a stress period. \texttt{minrate} must be less than \texttt{maxrate}.
block period
name maxrate
type double precision
shape
tagged false
in_record true
reader urword
longname maximum shutoff rate
description is the maximum rate that a well must exceed to reactivate a well during a stress period. \texttt{maxrate} must be less than \texttt{minrate}.
block period
name rate_scalingrecord
type record rate_scaling pump_elevation scaling_length
shape
tagged
in_record true
reader urword
longname
description
block period
name rate_scaling
type keyword
shape
in_record true
reader urword
longname rate scaling
description activate rate scaling. If \texttt{rate\_scaling} is specified, both \texttt{pump\_elevation} and \texttt{reduction\_length} must be specified. \texttt{rate\_scaling} cannot be used with \texttt{head\_limit}.
block period
name pump_elevation
type double precision
shape
tagged false
in_record true
reader urword
longname pump elevation
description is the elevation of the multi-aquifer well pump (\texttt{pump\_elevation}). \texttt{pump\_elevation} cannot be less than the bottom elevation (\texttt{bottom}) of the multi-aquifer well. By default, \texttt{pump\_elevation} is set equal to the bottom of the largest \texttt{GWF} node number connected to a MAW well.
block period
name scaling_length
type double precision
shape
tagged false
in_record true
reader urword
longname
description height above the pump elevation (\texttt{scaling\_length}) below which the pumping rate is reduced. The default value for \texttt{scaling\_length} is the well radius.
block period
name auxiliaryrecord
type record auxiliary auxname auxval
shape
tagged
in_record true
reader urword
longname
description
block period
name auxiliary
type keyword
shape
in_record true
reader urword
longname
description keyword for specifying auxiliary variable.
block period
name auxname
type string
shape
tagged false
in_record true
reader urword
longname
description name for the auxiliary variable to be assigned \texttt{auxval}. \texttt{auxname} must match one of the auxiliary variable names defined in the \texttt{OPTIONS} block. If \texttt{auxname} does not match one of the auxiliary variable names defined in the \texttt{OPTIONS} block the data are ignored.
block period
name auxval
type double precision
shape
tagged false
in_record true
reader urword
longname auxiliary variable value
description value for the auxiliary variable.
The mawsetting variable renders very simply in the block description as
BEGIN PERIOD iper
WELL wellno mawsetting
WELL wellno mawsetting
...
END PERIOD
But, the description for the mawsetting contains the additional information specified for the keystring. For example, the following is written as the latex description for mawsetting:
\item \texttt{mawsetting}---line of information that is parsed into a keyword and values. Keyword values that can be used to start the \texttt{mawsetting} string include: \texttt{FLOWING\_WELL}, \texttt{RATE}, \texttt{WELL\_HEAD}, \texttt{HEAD\_LIMIT}, \texttt{SHUT\_OFF}, \texttt{RATE\_SCALING}, and \texttt{AUXILIARY}.
\begin{verbatim}
STATUS status
FLOWING_WELL fwelev fwcond
RATE rate
WELL_HEAD well_head
HEAD_LIMIT head_limit
SHUT_OFF minrate maxrate
RATE_SCALING pump_elevation scaling_length
AUXILIARY auxname auxval
\end{verbatim}
The reader attribute indicates what reader is used by MODFLOW 6 for the information. There are several reader types that result in specialized input instructions. For example, the delr array of the DIS package is read using u1ddbl. Because the MODFLOW 6 array readers often require a control record, when this reader type is specified, information about the control record is written. For example, the following block identifies how delr is specified:
block disdata
name delr
type double precision
shape (ncol)
reader u1ddbl
longname spacing along a row
description is the is the column spacing in the row direction.
This results in the following block description:
BEGIN DISDATA
DELR
delr(ncol) -- U1DDBL
END DISDATA
The READARRAY reader is another reader that results in specialized input. It allows for a LAYERED keyword to be specified. The icelltype variable is read using readarray and is specified as:
block npfdata
name icelltype
type integer
shape (nodes)
valid
reader readarray
layered true
optional
longname confined or convertible indicator
description flag for each cell that specifies how saturated thickness is treated. 0 means saturated thickness is held constant; $>$0 means saturated thickness varies with computed head when head is below the cell top; $<$0 means saturated thickness varies with computed head unless the THICKSTRT option is in effect. When THICKSTRT is in effect, a negative value of icelltype indicates that saturated thickness will be computed as STRT-BOT and held constant.
This results in the following block description:
BEGIN NPFDATA
ICELLTYPE [LAYERED]
icelltype(nodes) -- READARRAY
END NPFDATA
Many of the MODFLOW 6 input variables share common description information. This information can be defined in one place and then referenced as many times as needed throughout the definition files. The definition file ./dfn/common.dfn is where common infomation is defined. For example, there is a text string defined as:
name auxnames
description defines an array of one or more auxiliary variable names. There is no limit on the number of auxiliary variables that can be provided on this line; however, lists of information provided in subsequent blocks must have a column of data for each auxiliary variable name defined here. The number of auxiliary variables detected on this line determines the value for naux. Comments cannot be provided anywhere on this line as they will be interpreted as auxiliary variable names. Auxiliary variables may not be used by the {#1} model, but they will be available for use by other parts of the program. The ``AUX'' and ``AUXILIARY'' keywords can be used as a substitute for ``AUXNAMES''. The program will terminate with an error if auxiliary variables are specified on more than one line in the options block.
This can be used in the description for auxnames throughout in the following manner:
block options
name auxnames
type string
shape (naux)
reader urword
optional true
longname keyword to save GWFGWF flows
description REPLACE auxnames {'{#1}': 'Groundwater Flow'}
In the description attribute, the capital REPLACE instructs the processor to replace auxnames with the text string defined by auxnames in common.dfn. Also included here is a Python dictionary, which instructs the processor to replace the text string '{#1}' with 'Groundwater Flow'.
The Python script mf6ivar.py will process all of the definition files and create a markdown file, latex files of the variable descriptions, and text files containing the blocks.