Assign solutions to MODFLOW 6 cells with native input file syntax

Boundary conditions

Modify the file mf6/gwf_cat_ex_1d.wel and add another auxiliary variable rtmf6_sol_number in addition to concentration you already used in the transport simulation:

BEGIN options
  auxiliary  concentration  rtmf6_sol_number
  SAVE_FLOWS
END options

BEGIN dimensions
  MAXBOUND  1
END dimensions

BEGIN period  1
  1 1 1 1 0 0
END period  1

The last value 0 specifies that the solution SOLUTION 0  CaCl2 in the file advect.pqi is used for the boundary condition.

You need to specify this file name with relative path to the project root in TOML config file under bc_concentrations

Initial concentrations

Modify the file mf6/gwt_cat_ex_1d.ic and replace concentration value with the solution number:

BEGIN options
END options

BEGIN griddata
  strt
    CONSTANT       1.00000000
END griddata

While the value of STRT has a datatype of float, it will be converted into an integer to represent an solution number in the file advect.pqi.

You need to specify this file name with relative path to the project root in TOML config file under initial_concentrations.

Note

You can copy the file mf6/gwt_cat_ex_1d.ic into a different directory first, modify it and specify this new paths in the TOML configuration file. See also: how exchanges are specified.

Exchanges

Copy the file mf6/gwt_cat_ex_1d.ic to rtmf6/init_exchanges.ic. Modify the file rtmf6/init_exchanges.ic and replace concentration value with the solution number:

BEGIN options
END options

BEGIN griddata
  strt
    # rtmf6_exchange_number
    CONSTANT       1
END griddata