When water is removed from an aquifer, the aquifer will frequently undergo compaction which then causes subsidence at the land surface. Three packages in MODFLOW, the Interbed-Storage package, the Subsidence and Aquifer-System Compaction package, and the Subsidence and Aquifer-System Compaction Package for Water-Table Aquifers can be used to model this process. However, the Interbed-Storage package can not be used in the same model as either of the other two subsidence packages. Attempting to do so will cause MODFLOW to print an error message and stop. The Interbed-Storage package has no capabilities that are not provided by the other two packages. It simulates compaction of clay interbeds within an aquifer but does not account for possible delays between when the head is reduced and the compaction occurs. The Subsidence and Aquifer-System Compaction package was developed by modifying the Interbed-Storage package to simulate such time delays.
