The SRC: GWT Mass Loading Package pane is on the MODFLOW Features tab of the Object Properties dialog box.
The data that can be specified for the SRC package are the Starting time, Ending time, and Mass Loading and the Chemical Species. The Mass Loading is the mass source loading rate for the selected Chemical Species. A positive value indicates addition of solute mass and a negative value indicates removal of solute mass.
"Mass Loading Active" can be used to turn on or off a CNC boundary. If the formula for Mass Loading Active evaluates to True, a mass loading boundary will be defined. If it evaluates to False, a mass loading boundary will not be defined. This can be used to turn on or off mass loading boundaries at different locations based on a criterion specified by the user. Such a capability can be useful for specifying tidal boundaries where some locations may be alternately flooded or exposed.
Mass Loading Multiplier is only used if it has been activated in the SRC: GWT Mass Source Loading Package Pane. If Mass Loading Multiplier is specified, the concentration is multiplied by the Mass Loading Multiplier value.
Starting time and Ending time are explained in the help for the MODFLOW Features tab.
