### GWF-HFB

#### Structure of Blocks

_FOR EACH SIMULATION_

```
    BEGIN OPTIONS
      [PRINT_INPUT]
    END OPTIONS
```
```
    BEGIN DIMENSIONS
      MAXHFB <maxhfb>
    END DIMENSIONS
```

_FOR ANY STRESS PERIOD_

```
    BEGIN PERIOD <iper>
      <cellid1> <cellid2> <hydchr>
      <cellid1> <cellid2> <hydchr>
      ...
    END PERIOD
```

#### Explanation of Variables

##### Block: OPTIONS

  * `PRINT_INPUT` keyword to indicate that the list of hydraulic flow barriers will be written to the listing file immediately after it is read.

##### Block: DIMENSIONS

  * `maxhfb` integer value specifying the maximum number of hydraulic flow barriers that will be entered in this input file.  The value of MAXHFB is used to allocate memory for the hydraulic flow barriers.

##### Block: PERIOD

  * `iper` integer value specifying the starting stress period number for which the data specified in the PERIOD block apply.  IPER must be less than or equal to NPER in the TDIS Package and greater than zero.  The IPER value assigned to a stress period block must be greater than the IPER value assigned for the previous PERIOD block.  The information specified in the PERIOD block will continue to apply for all subsequent stress periods, unless the program encounters another PERIOD block.

  * `cellid1` identifier for the first cell.  For a structured grid that uses the DIS input file, CELLID1 is the layer, row, and column numbers of the cell.   For a grid that uses the DISV input file, CELLID1 is the layer number and CELL2D number for the two cells.  If the model uses the unstructured discretization (DISU) input file, then CELLID1 is the node number for the cell.  The barrier is located between cells designated as CELLID1 and CELLID2.  The program will terminate with an error if CELLID1 and CELLID2 are not horizontally or vertically adjacent.

  * `cellid2` identifier for the second cell. See CELLID1 for description of how to specify.

  * `hydchr` is the hydraulic characteristic of the hydraulic-flow barrier. The hydraulic characteristic is the barrier hydraulic conductivity divided by the width of the hydraulic-flow barrier. If the hydraulic characteristic is negative, then the absolute value of HYDCHR acts as a multiplier to the conductance between the two model cells specified as containing the barrier. For example, if the value for HYDCHR was specified as -1.5, the conductance calculated for the two cells would be multiplied by 1.5.

#### Example Input File
```
    BEGIN OPTIONS
      PRINT_INPUT
    END OPTIONS
    
    BEGIN DIMENSIONS
      MAXHFB 1
    END DIMENSIONS
    
    BEGIN PERIOD 1
      #L1 R1 C1 L2 R2 C2 HYDCHR
        1  1  4  1  1  5 0.1
    END PERIOD 1
```