GWT-IST

Structure of Blocks

FOR EACH SIMULATION

    BEGIN OPTIONS
      [SAVE_FLOWS]
      [SORBTION]
      [FIRST_ORDER_DECAY]
      [ZERO_ORDER_DECAY]
      [CIM FILEOUT <cimfile>]
      [CIM PRINT_FORMAT COLUMNS <columns> WIDTH <width> DIGITS <digits> <format>]
    END OPTIONS

    BEGIN GRIDDATA
      [CIM [LAYERED]
            <cim(nodes)> -- READARRAY]
      THETAIM [LAYERED]
            <thetaim(nodes)> -- READARRAY
      ZETAIM [LAYERED]
            <zetaim(nodes)> -- READARRAY
      [DECAY [LAYERED]
            <decay(nodes)> -- READARRAY]
      [DECAY_SORBED [LAYERED]
            <decay_sorbed(nodes)> -- READARRAY]
      BULK_DENSITY [LAYERED]
            <bulk_density(nodes)> -- READARRAY
      DISTCOEF [LAYERED]
            <distcoef(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.

  • SORBTION is a text keyword to indicate that sorbtion will be activated. Use of this keyword requires that BULK_DENSITY and DISTCOEF are specified in the GRIDDATA block.

  • 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 sorbtion 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 sorbtion is active) are specified in the GRIDDATA block.

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

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

  • cimfile name of the output file to write immobile concentrations.

  • 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.

Block: GRIDDATA

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

  • thetaim porosity of the immobile domain specified as the volume of immobile pore space per total volume (dimensionless).

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

  • 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 affect 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 sorbtion are active, then the sorbed decay rate will be set equal to the aqueous decay rate. decay_sorbed will have no affect 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 the aquifer in mass per length cubed. bulk_density will have no affect on simulation results unless the SORBTION keyword is specified in the options block.

  • distcoef is the distribution coefficient for the equilibrium-controlled linear sorption isotherm in dimensions of length cubed per mass. distcoef will have no affect on simulation results unless the SORBTION keyword is specified in the options block.

Example Input File

    BEGIN OPTIONS
      SORBTION
      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