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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsCities can sink when groundwater pumping lowers water pressure in compressible sediments beneath them. As pressure falls, the sediment framework carries more of the overlying load and fine-grained layers compact. If groundwater levels later recover, some elastic deformation may reverse, but permanent compaction can remain—and different parts of the same region may subside, stay stable, or rise.
How groundwater pumping makes the land sink
An aquifer system is not usually an empty underground lake. It is a layered body of sediment and rock whose pores hold water. Groundwater pressure helps support the sediment framework. Pumping lowers that pressure, increasing the load carried by the solid material. Where layers are compressible—especially fine-grained sediments—the layers can compact and the land surface above them can descend.
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A wet sponge can be a rough analogy, but it has limits: aquifer systems are layered geological materials, and compaction is not simply water being squeezed out of one uniform sponge. In the San Joaquin Valley, for example, much of the studied compaction occurred beneath the regional confining unit known as the Corcoran Clay.
The U.S. Geological Survey (USGS) identifies aquifer-system compaction associated with groundwater withdrawals as a principal cause of land subsidence. Its 1999 national report estimated that more than 80 percent of identified land subsidence in the United States was a consequence of human impact on subsurface water. That figure is specific to the United States and to that report; it is not a current global estimate.
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Why some sinking reverses—and some does not
The important distinction is between elastic and inelastic deformation. If groundwater pressure changes remain within the sediment’s previous stress range, some layers can deform elastically: when pressure recovers, they may expand and the land may rise. But if water levels fall below historical lows and the sediment experiences stress beyond its previous range, compaction can become inelastic. That elevation loss may persist, and the aquifer may lose some of its capacity to store water.
So a rise in groundwater level does not automatically restore the land to its earlier elevation or recover lost storage. Recovery can slow or stop further compaction and may produce uplift where the geology responds elastically. Elsewhere, residual compaction can continue, or the surface can remain at a lower elevation.
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What the evidence shows in three California and Mexico cases
| Place and period | Groundwater and land response | Practical consequence or qualification |
|---|---|---|
| San Joaquin Valley, California; 1926–1970 and later periods | USGS reports that groundwater withdrawals caused widespread aquifer compaction from 1926 to 1970, with subsidence locally exceeding 8.5 meters. Imported surface water beginning in the 1950s and early 1970s reduced pumping, helped water levels recover, and reduced compaction in some areas. Drought-related reductions in surface-water deliveries later prompted more pumping, falling water levels, and renewed compaction. | The 8.5-meter figure is a local maximum, not a valley-wide rate. In the 2003–2010 study, some locations showed seasonal uplift and subsidence with little or no longer-term elevation loss; other locations subsided, in some cases largely inelastically after deep groundwater levels reached historical lows. Subsidence reduced freeboard and flow capacity in the California Aqueduct, Delta-Mendota Canal, and other canals. |
| Coachella Valley, California; 2010–2017 | Groundwater levels generally stabilized or rose from about 2010. USGS and the Coachella Valley Water District have investigated subsidence since 1996. Measures described in a 2020 USGS report include imported Colorado River water through the Mid-Valley Pipeline, budget-based tiered rates, and managed recharge at the Thomas E. Levy Groundwater Replenishment Facility. | GPS and InSAR observations found stable areas, areas that subsided, and areas that uplifted. In measurements at 24 GPS monuments from August 2010 to September 2015, 17 were stable; of the seven that changed, three subsided by 0.17–0.43 feet and four uplifted by 0.11–0.18 feet, with measurement uncertainties reported by USGS. The agency interprets ongoing subsidence during recovering water levels as possible residual compaction and uplift as possible expansion of coarse-grained materials or thin aquitards. |
| Mexico City region; October 2025–January 2026 | NASA’s April 29, 2026 report describes preliminary NISAR satellite observations showing parts of the region subsiding by more than 2 centimeters per month. NASA says extensive groundwater pumping, alongside urban development, has compacted the ancient lakebed for more than a century. | The rate applies to parts of the region, not the whole city. NASA cautions that some yellow and red map signals likely represent residual noise that should decrease with additional observations. NASA also reports that parts of the metropolitan area sank around 35 centimeters per year in the 1990s and 2000s, damaging infrastructure including the Metro; that historical figure is not a current citywide rate. |
The Coachella observations illustrate why groundwater recovery is not a uniform rebound: even within one valley, monuments can record stability, subsidence, or uplift over the same broad period. In the San Joaquin Valley, surface-water substitution reduced pressure on groundwater in some areas, but later drought-related pumping was associated with renewed water-level decline and compaction.
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How scientists tell whether the ground is moving
Researchers combine measurements because water levels alone do not show exactly how much the land surface or buried sediment has moved. Common methods include:
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- Groundwater wells: track water levels, or hydraulic head, over time.
- Extensometers: measure compaction within an aquifer system at depth.
- InSAR: compares satellite radar observations to map surface movement across broad areas.
- Continuous or campaign GPS: tracks elevation changes at fixed stations or monuments.
- Spirit leveling: measures precise elevation differences along surveyed routes.
USGS’s San Joaquin Valley work combined extensometers, GPS surveys, InSAR, spirit leveling, and groundwater wells. Bringing together surface movement, subsurface compaction, and water levels—especially continuous measurements—helps researchers assess aquifer response, estimate the water-level threshold associated with prior stress, and calculate storage properties. No single method answers every question: satellite maps show broad patterns, while wells and extensometers help connect those patterns to groundwater and deformation at depth.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Subsidence is not always caused by groundwater pumping
Groundwater-related compaction is a major mechanism, but it is not the explanation for every sinking landscape. USGS also identifies processes such as drainage of organic soils, mining, natural compaction, sinkholes, and permafrost thaw. For any particular city, the cause depends on local geology and activity; a map of downward movement by itself does not establish that groundwater pumping is responsible.
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Rates from different places should not be ranked casually. A local maximum, a satellite result over several months, and a long-term survey measurement may cover different areas, periods, and methods. Mexico City’s preliminary NISAR map, for example, is evidence of rapid movement in parts of the region, not a directly comparable citywide ranking against California basin measurements.
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