NPWEL—is the number of well parameters.

In MODFLOW-2000, the maximum number of allowed parameters is 999.

MXL—is the maximum number of wells that will be defined using parameters.

MXACTW—is the maximum number of wells in use during any stress period. MXACTW includes wells that are defined using parameters as well as wells that are defined without using parameters.

IWELCB—is a flag and a unit number.

•If IWELCB > 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 IWELCB = 0, cell-by-cell flow terms will not be written.

•If IWELCB < 0, well recharge for each well will be written to the listing file when "SAVE BUDGET" or a non-zero value for ICBCFL is specified in Output Control.

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 well 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 Q 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 well 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.

SPECIFY is a keyword option used to specify a value for PHIRAMP. If SPECIFY is not specified then a default value of 0.05 is used.

PHIRAMP is the fraction of the cell thickness used as an interval for smoothly adjusting negative pumping rates to 0 for dry cells. Negative pumping rates are adjusted to 0 or a smaller negative value when the head in the cell is equal to or less than the calculated interval above the cell bottom (see equations 24 and 25 on page 14 of Niswonger and others, 2011).

Changes were made to report wells with reduced pumping due to dewatered conditions to a separate output file or to the main listing file. If the wells with reduced pumping rates are written to a separate output file then a file of type "DATA" must be included in the Name file with a unit number that matches the unit number specified in the Well file (following the variable PHIRAMP in Item 2b). For example, a value of PHIRAMP (see MODFLOW-NWT documentation report) of 0.3 and a unit number of 50 can be specified in the second line of the Well file using the key word "SPECIFY" as:

SPECIFY  0.3  50

The following line must be added to the Name file:

DATA     50    Reduced_wells.out

Thus, wells with reduced pumping will be written for each time step to the output file "Reduced_wells.out" with unit number 50. For example, wells with reduced pumping will be reported to file "reduced_wells.out" as:

 WELLS WITH REDUCED PUMPING FOR STRESS PERIOD     6 TIME STEP     2

   LAY   ROW   COL         APPL.Q          ACT.Q        GW-HEAD       CELL-BOT

     4    91    69  -0.104400E+04  -0.104399E+04   0.208142E+04   0.205380E+04

     4    91    69  -0.208800E+04  -0.208798E+04   0.208142E+04   0.205380E+04

     4    91    69  -0.208800E+04  -0.208798E+04   0.208142E+04   0.205380E+04

 WELLS WITH REDUCED PUMPING FOR STRESS PERIOD     6 TIME STEP     3

   LAY   ROW   COL         APPL.Q          ACT.Q        GW-HEAD       CELL-BOT

     4    91    69  -0.104400E+04  -0.967118E+03   0.207686E+04   0.205380E+04

     4    91    69  -0.208800E+04  -0.193424E+04   0.207686E+04   0.205380E+04

     4    91    69  -0.208800E+04  -0.193424E+04   0.207686E+04   0.205380E+04

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.

PARTYP—is the type of parameter. For the WEL Package, the only allowed parameter type is Q, which defines values of the volumetric recharge rate.

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

NLST—is the number of wells that are included in a non-time-varying parameter or in each instance of a time-varying parameter.

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.

NUMINST – is the number of instances that are included in the definition of a time-varying parameter, where each instance is a list of wells 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.

Layer—is the layer number of the model cell that contains the well.

Row—is the row number of the model cell that contains the well.

Column—is the column number of the model cell that contains the well.

Qfact—is the factor used to calculate well recharge rate from the parameter value. The recharge rate is the product of Qfact and the parameter value.

[xyz]—represents any auxiliary variables for a well that has 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.

ITMP—is a flag and a counter.

•If ITMP < 0, non-parameter well data from the last stress period will be reused.

•If ITMP ≥ 0, ITMP will be the number of non-parameter wells read for the current stress period.

NP—is the number of parameters in use in the current stress period.

Layer—is the layer number of the model cell that contains the well.

Row—is the row number of the model cell that contains the well.

Column—is the column number of the model cell that contains the well.

Q—is the volumetric recharge rate. A positive value indicates recharge and a negative value indicates discharge (pumping).

[xyz]—represents any auxiliary variables for a well that has 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.

Pname—is the name of a parameter that is being used in the current stress period. NP parameter names will be read.

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.