GWT-IST

Structure of Blocks

FOR EACH SIMULATION

    BEGIN OPTIONS
      [SAVE_FLOWS]
      [BUDGET FILEOUT <budgetfile>]
      [BUDGETCSV FILEOUT <budgetcsvfile>]
      [SORPTION <sorption>]
      [FIRST_ORDER_DECAY]
      [ZERO_ORDER_DECAY]
      [CIM FILEOUT <cimfile>]
      [CIM PRINT_FORMAT COLUMNS <columns> WIDTH <width> DIGITS <digits> <format>]
      [SORBATE FILEOUT <sorbatefile>]
      [EXPORT_ARRAY_ASCII]
      [EXPORT_ARRAY_NETCDF]
    END OPTIONS

    BEGIN GRIDDATA
      POROSITY [LAYERED] [NETCDF]
            <porosity(nodes)> -- READARRAY
      VOLFRAC [LAYERED] [NETCDF]
            <volfrac(nodes)> -- READARRAY
      ZETAIM [LAYERED] [NETCDF]
            <zetaim(nodes)> -- READARRAY
      [CIM [LAYERED] [NETCDF]
            <cim(nodes)> -- READARRAY]
      [DECAY [LAYERED] [NETCDF]
            <decay(nodes)> -- READARRAY]
      [DECAY_SORBED [LAYERED] [NETCDF]
            <decay_sorbed(nodes)> -- READARRAY]
      [BULK_DENSITY [LAYERED] [NETCDF]
            <bulk_density(nodes)> -- READARRAY]
      [DISTCOEF [LAYERED] [NETCDF]
            <distcoef(nodes)> -- READARRAY]
      [SP2 [LAYERED] [NETCDF]
            <sp2(nodes)> -- READARRAY]
    END GRIDDATA

Explanation of Variables

Block: OPTIONS

  • SAVE_FLOWS keyword to indicate that IST flow terms will be written to the file specified with “BUDGET FILEOUT” in Output Control.

  • BUDGET keyword to specify that record corresponds to the budget.

  • FILEOUT keyword to specify that an output filename is expected next.

  • budgetfile name of the binary output file to write budget information.

  • BUDGETCSV keyword to specify that record corresponds to the budget CSV.

  • budgetcsvfile name of the comma-separated value (CSV) output file to write budget summary information. A budget summary record will be written to this file for each time step of the simulation.

  • sorption is a text keyword to indicate that sorption will be activated. Valid sorption options include LINEAR, FREUNDLICH, and LANGMUIR. Use of this keyword requires that BULK_DENSITY and DISTCOEF are specified in the GRIDDATA block. If sorption is specified as FREUNDLICH or LANGMUIR then SP2 is also required in the GRIDDATA block. The sorption option must be consistent with the sorption option specified in the MST Package or the program will terminate with an error.

  • FIRST_ORDER_DECAY is a text keyword to indicate that first-order decay will occur. Use of this keyword requires that DECAY and DECAY_SORBED (if sorption is active) are specified in the GRIDDATA block.

  • ZERO_ORDER_DECAY is a text keyword to indicate that zero-order decay will occur. Use of this keyword requires that DECAY and DECAY_SORBED (if sorption is active) are specified in the GRIDDATA block.

  • CIM keyword to specify that record corresponds to immobile concentration.

  • cimfile name of the output file to write immobile concentrations. This file is a binary file that has the same format and structure as a binary head and concentration file. The value for the text variable written to the file is CIM. Immobile domain concentrations will be written to this file at the same interval as mobile domain concentrations are saved, as specified in the GWT Model Output Control file.

  • PRINT_FORMAT keyword to specify format for printing to the listing file.

  • columns number of columns for writing data.

  • width width for writing each number.

  • digits number of digits to use for writing a number.

  • format write format can be EXPONENTIAL, FIXED, GENERAL, or SCIENTIFIC.

  • SORBATE keyword to specify that record corresponds to immobile sorbate concentration.

  • sorbatefile name of the output file to write immobile sorbate concentration information. Immobile sorbate concentrations will be written whenever aqueous immobile concentrations are saved, as determined by settings in the Output Control option.

  • EXPORT_ARRAY_ASCII keyword that specifies input griddata arrays should be written to layered ascii output files.

  • 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: GRIDDATA

  • porosity porosity of the immobile domain specified as the immobile domain pore volume per immobile domain volume.

  • volfrac fraction of the cell volume that consists of this immobile domain. The sum of all immobile domain volume fractions must be less than one.

  • zetaim mass transfer rate coefficient between the mobile and immobile domains, in dimensions of per time.

  • cim initial concentration of the immobile domain in mass per length cubed. If CIM is not specified, then it is assumed to be zero.

  • decay is the rate coefficient for first or zero-order decay for the aqueous phase of the immobile domain. A negative value indicates solute production. The dimensions of decay for first-order decay is one over time. The dimensions of decay for zero-order decay is mass per length cubed per time. Decay will have no effect on simulation results unless either first- or zero-order decay is specified in the options block.

  • decay_sorbed is the rate coefficient for first or zero-order decay for the sorbed phase of the immobile domain. A negative value indicates solute production. The dimensions of decay_sorbed for first-order decay is one over time. The dimensions of decay_sorbed for zero-order decay is mass of solute per mass of aquifer per time. If decay_sorbed is not specified and both decay and sorption are active, then the program will terminate with an error. decay_sorbed will have no effect on simulation results unless the SORPTION keyword and either first- or zero-order decay are specified in the options block.

  • bulk_density is the bulk density of this immobile domain in mass per length cubed. Bulk density is defined as the immobile domain solid mass per volume of the immobile domain. bulk_density is not required unless the SORPTION keyword is specified in the options block. If the SORPTION keyword is not specified in the options block, bulk_density will have no effect on simulation results.

  • distcoef is the distribution coefficient for the equilibrium-controlled linear sorption isotherm in dimensions of length cubed per mass. distcoef is not required unless the SORPTION keyword is specified in the options block. If the SORPTION keyword is not specified in the options block, distcoef will have no effect on simulation results.

  • sp2 is the exponent for the Freundlich isotherm and the sorption capacity for the Langmuir isotherm. sp2 is not required unless the SORPTION keyword is specified in the options block and sorption is specified as FREUNDLICH or LANGMUIR. If the SORPTION keyword is not specified in the options block, or if sorption is specified as LINEAR, sp2 will have no effect on simulation results.

Example Input File

    BEGIN OPTIONS
      SORPTION
      FIRST_ORDER_DECAY
      CIM FILEOUT gwtmodel.imd1.ucn
    END OPTIONS
    
    BEGIN GRIDDATA
      ZETAIM
        CONSTANT 0.01
      THETAIM
        CONSTANT 0.025
      BULK_DENSITY
        CONSTANT       0.25000000
      DISTCOEF
        CONSTANT       0.01000000
      DECAY
        CONSTANT       0.01000000
      DECAY_SORBED
        CONSTANT       0.01000000
    END GRIDDATA