GWF-CHD

Structure of Blocks

FOR EACH SIMULATION

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

    BEGIN DIMENSIONS
      MAXBOUND <maxbound>
    END DIMENSIONS

FOR ANY STRESS PERIOD

    BEGIN PERIOD <iper>
      <cellid(ncelldim)> <head> [<aux(naux)>] [<boundname>]
      <cellid(ncelldim)> <head> [<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 CHD head value.
BOUNDNAMES keyword to indicate that boundary names may be provided with the list of constant-head cells.
PRINT_INPUT keyword to indicate that the list of constant-head information will be written to the listing file immediately after it is read.
PRINT_FLOWS keyword to indicate that the list of constant-head 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 constant-head 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 constant-head 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 constant-head package.

Block: DIMENSIONS

maxbound integer value specifying the maximum number of constant-head 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.
head is the head at the boundary. 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 constant head. The values of auxiliary variables must be present for each constant head. 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 constant head boundary 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
      AUXILIARY temperature
      BOUNDNAMES
      PRINT_INPUT
      PRINT_FLOWS
      SAVE_FLOWS
    END OPTIONS
    
    #The DIMENSIONS block is required
    BEGIN DIMENSIONS
      MAXBOUND 2
    END DIMENSIONS
    
    #The following block of constant-head cells will be activated
    #for stress period 1.  This block will remain active throughout
    #the simulation.
    
    BEGIN PERIOD 1
    #l r c  head  temperature  boundname
     1 1 2  100.  20.5         chd_1_2
     1 1 3  100.  20.4         chd_1_3
    END PERIOD 1

Available Observation Types

Stress Package	Observation Type	ID1	ID2	Description
CHD	chd	cellid or boundname	--	Flow between the groundwater system and a constant-head boundary or a group of cells with constant-head boundaries.

Example Observation Input File

    BEGIN OPTIONS
      DIGITS 8
      PRINT_INPUT
    END OPTIONS
    
    BEGIN CONTINUOUS FILEOUT my_model.chd01.csv
    # obsname  obstype   ID
      chd_2_1  CHD       1 1 2
      chd_2_2  CHD       1 2 2
      chd_2_3  CHD       1 3 2
      chd_2_4  CHD       1 4 2
    END CONTINUOUS
    
    BEGIN CONTINUOUS FILEOUT my_model.chd02.csv
    # obsname     obstype   ID
      chd_3_flow  CHD       CHD_1_3
    END CONTINUOUS