GWF-DRN

Structure of Blocks

FOR EACH SIMULATION

    BEGIN OPTIONS
      [AUXILIARY <auxiliary(naux)>]
      [AUXMULTNAME <auxmultname>]
      [AUXDEPTHNAME <auxdepthname>]
      [BOUNDNAMES]
      [PRINT_INPUT]
      [PRINT_FLOWS]
      [SAVE_FLOWS]
      [TS6 FILEIN <ts6_filename>]
      [OBS6 FILEIN <obs6_filename>]
      [MOVER]
    END OPTIONS

    BEGIN DIMENSIONS
      MAXBOUND <maxbound>
    END DIMENSIONS

FOR ANY STRESS PERIOD

    BEGIN PERIOD <iper>
      <cellid(ncelldim)> <elev> <cond> [<aux(naux)>] [<boundname>]
      <cellid(ncelldim)> <elev> <cond> [<aux(naux)>] [<boundname>]
      ...
    END PERIOD

Explanation of Variables

Block: OPTIONS

auxiliary 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 package, but they will be available for use by other parts of the program. The program will terminate with an error if auxiliary variables are specified on more than one line in the options block.
auxmultname name of auxiliary variable to be used as multiplier of drain conductance.
auxdepthname name of a variable listed in AUXILIARY that defines the depth at which drainage discharge will be scaled. If a positive value is specified for the AUXDEPTHNAME AUXILIARY variable, then ELEV is the elevation at which the drain starts to discharge and ELEV + DDRN (assuming DDRN is the AUXDEPTHNAME variable) is the elevation when the drain conductance (COND) scaling factor is 1. If a negative drainage depth value is specified for DDRN, then ELEV + DDRN is the elevation at which the drain starts to discharge and ELEV is the elevation when the conductance (COND) scaling factor is 1. A linear- or cubic-scaling is used to scale the drain conductance (COND) when the Standard or Newton-Raphson Formulation is used, respectively. This discharge scaling option is described in more detail in Chapter 3 of the Supplemental Technical Information.
BOUNDNAMES keyword to indicate that boundary names may be provided with the list of drain cells.
PRINT_INPUT keyword to indicate that the list of drain information will be written to the listing file immediately after it is read.
PRINT_FLOWS keyword to indicate that the list of drain flow rates will be printed to the listing file for every stress period time step in which “BUDGET PRINT” is specified in Output Control. If there is no Output Control option and “PRINT_FLOWS” is specified, then flow rates are printed for the last time step of each stress period.
SAVE_FLOWS keyword to indicate that drain flow terms will be written to the file specified with “BUDGET FILEOUT” in Output Control.
TS6 keyword to specify that record corresponds to a time-series file.
FILEIN keyword to specify that an input filename is expected next.
ts6_filename defines a time-series file defining time series that can be used to assign time-varying values. See the “Time-Variable Input” section for instructions on using the time-series capability.
OBS6 keyword to specify that record corresponds to an observations file.
obs6_filename name of input file to define observations for the Drain package. See the “Observation utility” section for instructions for preparing observation input files. Tables ref{table:gwf-obstypetable} and ref{table:gwt-obstypetable} lists observation type(s) supported by the Drain package.
MOVER keyword to indicate that this instance of the Drain Package can be used with the Water Mover (MVR) Package. When the MOVER option is specified, additional memory is allocated within the package to store the available, provided, and received water.

Block: DIMENSIONS

maxbound integer value specifying the maximum number of drains cells that will be specified for use during any stress period.

Block: PERIOD

iper integer value specifying the starting stress period number for which the data specified in the PERIOD block apply. IPER must be less than or equal to NPER in the TDIS Package and greater than zero. The IPER value assigned to a stress period block must be greater than the IPER value assigned for the previous PERIOD block. The information specified in the PERIOD block will continue to apply for all subsequent stress periods, unless the program encounters another PERIOD block.
cellid is the cell identifier, and depends on the type of grid that is used for the simulation. For a structured grid that uses the DIS input file, CELLID is the layer, row, and column. For a grid that uses the DISV input file, CELLID is the layer and CELL2D number. If the model uses the unstructured discretization (DISU) input file, CELLID is the node number for the cell.
elev 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.
cond 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.
aux represents the values of the auxiliary variables for each drain. The values of auxiliary variables must be present for each drain. The values must be specified in the order of the auxiliary variables specified in the OPTIONS block. If the package supports time series and 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.
boundname name of the drain cell. BOUNDNAME is an ASCII character variable that can contain as many as 40 characters. If BOUNDNAME contains spaces in it, then the entire name must be enclosed within single quotes.

Example Input File

    #The OPTIONS block is optional
    BEGIN OPTIONS
      BOUNDNAMES
      PRINT_INPUT
      PRINT_FLOWS
      SAVE_FLOWS
    END OPTIONS
    
    #The DIMENSIONS block is required
    BEGIN DIMENSIONS
      MAXBOUND 5
    END DIMENSIONS
    
    #The following block of drains will be activated for for the entire stress period
    BEGIN PERIOD 1
      #node elevation conductance boundname
            73        10.2             1000.        my_drn
            76        10.2             1000.        my_drn
            79        10.2             1000.        my_drn
            80        10.2             1000.        my_drn
            81        10.2             1000.        my_drn
    END PERIOD

Available Observation Types

Stress Package	Observation Type	ID1	ID2	Description
DRN	drn	cellid or boundname	--	Flow between the groundwater system and a drain boundary or group of drain boundaries.
DRN	to-mvr	cellid or boundname	--	Drain boundary discharge that is available for the MVR package for a drain boundary or a group of drain boundaries.

Example Observation Input File

    BEGIN OPTIONS
      DIGITS 8
      PRINT_INPUT
    END OPTIONS
    
    BEGIN CONTINUOUS FILEOUT my_model.drn01.csv
    # obsname      obstype   ID
      drn_73       DRN       73
      drn_79       DRN       79
    END CONTINUOUS
    
    BEGIN CONTINUOUS FILEOUT my_model.drn02.csv
    # obsname     obstype   ID
      drn_80      DRN       80
      drn_all     DRN       my_drn
    END CONTINUOUS