Subsidence

MODFLOW has several packages that can be used to simulate subsidence due to groundwater withdrawal. The ones supported in ModelMuse are the SUB and SWT packages.

The Subsidence and Aquifer-System Compaction (SUB) package is used for simulating the drainage, changes in groundwater storage, and compaction of aquifers, interbeds and confining units that constitute an aquifer system. Delays in the release of groundwater from interbed storage, and thus delays in aquifer-system compaction, can be simulated. Delayed drainage and compaction in confining units can also be simulated.

The Subsidence and Aquifer-System Compaction Package for Water-Table Aquifers (SWT) package simulates vertical compaction in models of regional ground-water flow. The program simulates ground-water storage changes and compaction in discontinuous interbeds or in extensive confining units, accounting for stress-dependent changes in storage properties. Several features of the program make it useful for application in shallow, unconfined flow systems. Geostatic stress can be treated as a function of water-table elevation, and compaction is a function of computed changes in effective stress at the bottom of a model layer. Thickness of compressible sediments in an unconfined model layer can vary in proportion to saturated thickness.

The Skeletal Storage, Compaction, and Subsidence (CSUB) package combines the capabilities of the SUB and SWT packages to simulate subsidence in MODFLOW 6 models.