The Time-Varying Storage Package is used to specify time-varying values of specific storage and specific yield at individual cells. The TVS: Time-Varying Storage Package pane is on the MODFLOW Packages and Programs dialog box under Flow Packages. Time-Varying Storage Package is documented in chapter 6 of mf6suptechinfo.pdf distributed with MODFLOW 6.
Changing the storage properties affects the head. For example, increasing the specific yield in a convertible cell under unconfined conditions will cause the head in the cell to decrease. By default, he TVS package will automatically adjust the head to account for the change in the storage properties. However, this effect can be disabled by unchecking the checkbox labeled "Enable storage change integration (Inverse of DISABLE_STORAGE_CHANGE_INTEGRATION)." If the check box is checked, the head will be unaffected by changes in the storage properties.
