### GWT-IC

#### Structure of Blocks

_FOR EACH SIMULATION_

```
    BEGIN OPTIONS
      [EXPORT_ARRAY_ASCII]
      [EXPORT_ARRAY_NETCDF]
    END OPTIONS
```
```
    BEGIN GRIDDATA
      STRT [LAYERED] [NETCDF]
            <strt(nodes)> -- READARRAY
    END GRIDDATA
```

#### Explanation of Variables

##### Block: OPTIONS

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

  * <span style="color:red">`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.</span>

##### Block: GRIDDATA

  * `strt` is the initial (starting) concentration---that is, concentration at the beginning of the GWT Model simulation.  STRT must be specified for all GWT Model simulations. One value is read for every model cell.

#### Example Input File
```
    #The OPTIONS block is optional
    BEGIN OPTIONS
    END OPTIONS
    
    #The GRIDDATA block is required
    BEGIN GRIDDATA
      STRT LAYERED
        CONSTANT   0.0  Initial Concentration layer   1
        CONSTANT   0.0  Initial Concentration layer   2
    END GRIDDATA
```