GWF-EVTA

Structure of Blocks

FOR EACH SIMULATION

    BEGIN OPTIONS
      READASARRAYS
      [FIXED_CELL]
      [AUXILIARY <auxiliary>]
      [AUXMULTNAME <auxmultname>]
      [PRINT_INPUT]
      [PRINT_FLOWS]
      [SAVE_FLOWS]
      [TAS6 FILEIN <tas6_filename>]
      [OBS6 FILEIN <obs6_filename>]
      [EXPORT_ARRAY_NETCDF]
    END OPTIONS

FOR ANY STRESS PERIOD

    BEGIN PERIOD <iper>
      [IEVT [NETCDF]
            <ievt(ncol*nrow; ncpl)> -- READARRAY]
      SURFACE [NETCDF]
            <surface(ncol*nrow; ncpl)> -- READARRAY
      RATE [NETCDF]
            <rate(ncol*nrow; ncpl)> -- READARRAY
      DEPTH [NETCDF]
            <depth(ncol*nrow; ncpl)> -- READARRAY
      AUX [NETCDF]
            <aux(ncol*nrow; ncpl)> -- READARRAY
    END PERIOD

Explanation of Variables

Block: OPTIONS

  • READASARRAYS indicates that array-based input will be used for the Evapotranspiration Package. This keyword must be specified to use array-based input. When READASARRAYS is specified, values must be provided for every cell within a model layer, even those cells that have an IDOMAIN value less than one. Values assigned to cells with IDOMAIN values less than one are not used and have no effect on simulation results.

  • FIXED_CELL indicates that evapotranspiration will not be reassigned to a cell underlying the cell specified in the list if the specified cell is inactive.

  • 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 evapotranspiration rate.

  • PRINT_INPUT keyword to indicate that the list of evapotranspiration information will be written to the listing file immediately after it is read.

  • PRINT_FLOWS keyword to indicate that the list of evapotranspiration 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 evapotranspiration flow terms will be written to the file specified with “BUDGET FILEOUT” in Output Control.

  • TAS6 keyword to specify that record corresponds to a time-array-series file.

  • FILEIN keyword to specify that an input filename is expected next.

  • tas6_filename defines a time-array-series file defining a time-array series that can be used to assign time-varying values. See the Time-Variable Input section for instructions on using the time-array series capability.

  • OBS6 keyword to specify that record corresponds to an observations file.

  • obs6_filename name of input file to define observations for the EVT package. See the “Observation utility” section for instructions for preparing observation input files. Table ref{table:gwf-obstypetable} lists observation type(s) supported by the EVT package.

  • EXPORT_ARRAY_NETCDF keyword that specifies input gridded arrays should be written to the model output NetCDF file with attributes that support using the generated file as a MODFLOW 6 simulation input. This option only has an effect when an output model NetCDF file is configured and the simulation is run in VALIDATE mode, otherwise it is ignored.

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.

  • ievt IEVT is the layer number that defines the layer in each vertical column where evapotranspiration is applied. If IEVT is omitted, evapotranspiration by default is applied to cells in layer 1. If IEVT is specified, it must be specified as the first variable in the PERIOD block or MODFLOW will terminate with an error.

  • surface is the elevation of the ET surface (L).

  • rate is the maximum ET flux rate (LT-1).

  • depth is the ET extinction depth (L).

  • aux is an array of values for auxiliary variable AUX(IAUX), where iaux is a value from 1 to NAUX, and AUX(IAUX) must be listed as part of the auxiliary variables. A separate array can be specified for each auxiliary variable. If an array is not specified for an auxiliary variable, then a value of zero is assigned. If the value specified here for the auxiliary variable is the same as auxmultname, then the evapotranspiration rate will be multiplied by this array.

Example Input File

    BEGIN OPTIONS
      READASARRAYS
      AUXILIARY var1 var2
      PRINT_INPUT
      PRINT_FLOWS
      SAVE_FLOWS
    END OPTIONS
    
    BEGIN PERIOD 1
      #For a structured grid, IEVT defaults to model
      # layer 1, so no need to enter IEVT here.
    
      #ET surface elevation
      SURFACE
        constant 150.0
      #Maximum ET rate
      RATE
        constant 0.007
      #ET extinction depth
      DEPTH
        constant 15.0
      #auxiliary variable (var1) array
      var1
        constant 100.0
      #auxiliary variable (var2) array
      var2
        constant 0.0
    END PERIOD