Groundwater-related subsidence

It is a growing problem in the developing world as cities increase in population and water use, without adequate pumping regulation and enforcement.

[1] Groundwater can be considered one of the last free resources, as anyone who can afford to drill can usually draw up merely according to their ability to pump (depending on local regulations).

[2] As shown in the USGS figure, aquifers are frequently associated with compressible layers of silt or clay.As the groundwater is pumped out, the effective stress changes, precipitating consolidation, which is often non-reversible.

A study in an arid agricultural region of Arizona[3] showed that, even with a water level recovery of 100 ft after groundwater pumping was stopped, the land surface continued to subside for decades.

This is a result of the continued dewatering of aquitards (fine-grain layers that slow the movement of groundwater) from stresses mentioned in the previous paragraph.

Major areas affected include the San Joaquin Valley in California,[8] Central Arizona,[2] Mexico City,[9] and Jakarta, Indonesia.