The MODFLOW SUB-WT code has been developed to simulate vertical compaction in regional groundwater flow models due to pumping.

MODFLOW SUB-WT can simulate changes in groundwater storages and compaction in discontinuous layers or extensive confining units. The MODFLOW SUB-WT modeling code considers the compaction of a particular layer of the numerical model as a function of effective effort changes in the layer.

This code works as a MODFLOW package and has been developed by the USGS. MODFLOW SUB-WT use is recommended in unconfined aquifers and also not too deep.

Fig. 1 – Vertical section of an aquifer system with compaction potenctial for fine sediment.

A. Hydrogeologic conceptualization, B. Three layer system model representation (1).

Theoretical framework

To incorporate the compaction calculus in groundwater flow models, a relation between compaction and the change of effective efforts in the soil has been established. This relation is based on Terzaghi´s theory: the effective effort. The compaction (consolidation) occurred when effective efforts (intergranular) increase.

Fig 2. Result of a compaction simulation SUB-WT in an aquifer with MODFLOW .

A. Model section showing model layer, properties and initial and final water table.
B. Vertical displacement calculated for the top of all layers. (2)

(1) y (2) text: Höffmann, J., Leake, S.A., Galloway, D.L., and Wilson, A.M., 2003, MODFLOW-2000 Ground-Water Model–User Guide to the Subsidence and Aquifer-System Compaction (SUB) Package: U.S. Geological Survey Open-File Report 03-233, 44 p. Link