In the General Head Boundary (GHB) package, there is a linear relationship between the head in the general head boundary cell and the flow of water into or out of the groundwater system at the boundary. This linear characteristic is advantageous for automated calibration of models. The pane for this package is on the MODFLOW Packages and Programs dialog box under Head Dependant Flux.
In MODFLOW 6 models, "multipliers" can be used with GHB boundaries. Multipliers will be used if the "Use Multiplier (MODFLOW 6)" checkbox is checked.. Ordinarily, multipliers are not needed. If multipliers are used, the GHB conductance is multiplied by the value of the multiplier. One use for multipliers might be when the GHB conductances are defined using a time-series and it is desired to multiply the GHB conductance values in the time series by a different amount at different locations.
On the GHB: General-Head Boundary package pane, the user can define parameters for the general-head boundaries. These parameters will be multiplied by user-specified multipliers to determine the general-head conductances defined by parameters. The user can also set up general-head boundaries that do not involve parameters. Objects must be used to define the locations of the general-head boundaries.
Parameters can also be edited in the Manage Parameters dialog box.
