GWT-DSP

Structure of Blocks

FOR EACH SIMULATION

    BEGIN OPTIONS
      [XT3D_OFF]
      [XT3D_RHS]
      [EXPORT_ARRAY_ASCII]
      [EXPORT_ARRAY_NETCDF]
    END OPTIONS

    BEGIN GRIDDATA
      [DIFFC [LAYERED] [NETCDF]
            <diffc(nodes)> -- READARRAY]
      [ALH [LAYERED] [NETCDF]
            <alh(nodes)> -- READARRAY]
      [ALV [LAYERED] [NETCDF]
            <alv(nodes)> -- READARRAY]
      [ATH1 [LAYERED] [NETCDF]
            <ath1(nodes)> -- READARRAY]
      [ATH2 [LAYERED] [NETCDF]
            <ath2(nodes)> -- READARRAY]
      [ATV [LAYERED] [NETCDF]
            <atv(nodes)> -- READARRAY]
    END GRIDDATA

Explanation of Variables

Block: OPTIONS

XT3D_OFF deactivate the xt3d method and use the faster and less accurate approximation. This option may provide a fast and accurate solution under some circumstances, such as when flow aligns with the model grid, there is no mechanical dispersion, or when the longitudinal and transverse dispersivities are equal. This option may also be used to assess the computational demand of the XT3D approach by noting the run time differences with and without this option on.
XT3D_RHS add xt3d terms to right-hand side, when possible. This option uses less memory, but may require more iterations.
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

diffc effective molecular diffusion coefficient.
alh longitudinal dispersivity in horizontal direction. If flow is strictly horizontal, then this is the longitudinal dispersivity that will be used. If flow is not strictly horizontal or strictly vertical, then the longitudinal dispersivity is a function of both ALH and ALV. If mechanical dispersion is represented (by specifying any dispersivity values) then this array is required.
alv longitudinal dispersivity in vertical direction. If flow is strictly vertical, then this is the longitudinal dispsersivity value that will be used. If flow is not strictly horizontal or strictly vertical, then the longitudinal dispersivity is a function of both ALH and ALV. If this value is not specified and mechanical dispersion is represented, then this array is set equal to ALH.
ath1 transverse dispersivity in horizontal direction. This is the transverse dispersivity value for the second ellipsoid axis. If flow is strictly horizontal and directed in the x direction (along a row for a regular grid), then this value controls spreading in the y direction. If mechanical dispersion is represented (by specifying any dispersivity values) then this array is required.
ath2 transverse dispersivity in horizontal direction. This is the transverse dispersivity value for the third ellipsoid axis. If flow is strictly horizontal and directed in the x direction (along a row for a regular grid), then this value controls spreading in the z direction. If this value is not specified and mechanical dispersion is represented, then this array is set equal to ATH1.
atv transverse dispersivity when flow is in vertical direction. If flow is strictly vertical and directed in the z direction, then this value controls spreading in the x and y directions. If this value is not specified and mechanical dispersion is represented, then this array is set equal to ATH2.

Example Input File

    BEGIN OPTIONS
    END OPTIONS
    
    BEGIN GRIDDATA
      DIFFC
        CONSTANT  1.e-9
      ALH
        CONSTANT 1.
      ALV
        CONSTANT 1.
      ATH1
        CONSTANT 0.1
      ATH2
        CONSTANT 0.1
      ATV
        CONSTANT 0.1
    END GRIDDATA