Cities can sink when groundwater pumping lowers pressure in compressible sediments, allowing those layers to compact under the weight above them. If water levels later recover, some ground may rise, but recovery does not necessarily restore lost elevation or aquifer storage. The outcome varies across a basin: some places stabilize, some continue sinking, and others uplift.
How groundwater pumping can make the ground sink
In a sediment-filled basin, groundwater occupies pores between grains and helps support pressure within the layers. Pumping lowers groundwater pressure, shifting more of the overlying load onto the sediment framework. Compressible layers—especially fine-grained deposits—can then compact, lowering the land surface. This is aquifer-system compaction, which the U.S. Geological Survey identifies as a principal cause of land subsidence associated with groundwater withdrawals.
A wet sponge can help illustrate the idea, but an aquifer system is not one uniform sponge or an empty underground lake. It is a stack of geological materials with different properties. In the San Joaquin Valley, much of the compaction documented by the USGS occurred beneath the Corcoran Clay, a regional confining layer.
Elastic movement versus lasting compaction
Some deformation is elastic: if groundwater pressure rises again, part of the material can expand and the surface may move upward. But when water levels fall below previous historical lows, the resulting stress can cause inelastic compaction. That compaction may leave permanent land-surface lowering and reduce the aquifer system’s capacity to store water. A water-level drop does not automatically mean permanent sinking, and recharge does not guarantee measurable uplift; the result depends on the materials and their stress history.
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What happens when groundwater levels recover
Here, “groundwater returns” means water levels rise after pumping is reduced, surface water substitutes for some pumping, or managed recharge adds water to the aquifer. It does not mean lost land elevation or storage returns automatically. Recovery can slow or stop further compaction and may cause uplift where the response is elastic. Elsewhere, residual compaction can continue for a time, or the surface can remain at a lower elevation.
That mix is visible in the Coachella Valley. The USGS reported that groundwater levels generally stabilized or rose from about 2010. Across 24 GPS monuments measured from August 2010 to September 2015, 17 remained stable; among the other seven, three subsided and four uplifted. The three subsiding monuments lowered by 0.17–0.43 feet, while the four that uplifted rose by 0.11–0.18 feet. In a broader 2010–17 analysis, some areas had stopped subsiding and a few had uplifted, while a few continued to subside at slower rates. USGS researchers suggest that continued sinking during recovery can reflect residual compaction, while uplift can reflect expansion of coarse-grained materials or thin aquitards.
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Three places show why local context matters
| Place and source | Period and evidence | What was observed |
|---|---|---|
| Mexico City region — NASA, April 29, 2026 | Preliminary NISAR radar analysis, October 2025–January 2026 | Parts of the region were subsiding by more than 2 centimeters per month; this is not a uniform rate for the whole city. |
| San Joaquin Valley — USGS, 2018 report | Historical subsidence, 1926–1970; later study of aquifer-system response, 2003–10 | Subsidence locally exceeded 8.5 meters during 1926–70. The later study found both seasonal movement and areas of longer-term subsidence. |
| Coachella Valley — USGS, 2020 report | GPS and InSAR observations, including the 2010–17 analysis | Locations were stable, subsiding, or uplifting as groundwater conditions improved; the monument measurements for 2010–15 are described above. |
Mexico City: a preliminary satellite view of a long-running problem
NASA describes Mexico City as built over an aquifer and an ancient lakebed. Extensive groundwater pumping, together with urban development, has compacted the lakebed for more than a century; an engineer documented the issue in 1925. NASA says parts of the metropolitan area sank around 35 centimeters per year in the 1990s and 2000s, damaging infrastructure including the Metro. Those historical figures and the recent NISAR result describe different periods and should not be treated as one continuous or citywide rate.
NISAR observations are useful because they allow repeated measurements across a broad area. NASA says the mission observes land and ice surfaces twice every 12 days, and its radar can operate day or night, through cloud cover, and over vegetation. The agency cautions that some yellow and red signals in its preliminary Mexico City map likely represent residual noise that should decrease with additional observations. The map is therefore evidence of substantial local movement, not a final measurement for every neighborhood.
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San Joaquin Valley: reduced pumping can slow compaction, but drought can reverse progress
The USGS reports that groundwater withdrawals drove widespread aquifer compaction and subsidence in the San Joaquin Valley from 1926 to 1970. Imported surface water, introduced beginning in the 1950s and early 1970s, reduced groundwater pumping in some areas, helped water levels recover, and reduced compaction. When drought cut surface-water deliveries, pumping increased, water levels fell, and compaction returned.
In the 2003–10 study, some locations showed seasonal uplift and subsidence with little or no longer-term elevation loss; other locations subsided over the longer term. In some rapidly sinking places, deep groundwater levels reached historical lows and compaction was largely inelastic. Subsidence also reduced freeboard and flow capacity in the California Aqueduct, the Delta-Mendota Canal, and other canals.
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Coachella Valley: management can improve water conditions without producing uniform uplift
The USGS and Coachella Valley Water District have investigated subsidence since 1996. The 2020 USGS report describes a mix of measures: imported Colorado River water delivered through the Mid-Valley Pipeline, budget-based tiered rates, and managed recharge at the Thomas E. Levy Groundwater Replenishment Facility. The report associates these measures with improved groundwater conditions in some areas that had historically been overdrafted. The varied land response described above shows why better groundwater conditions do not translate into the same surface movement everywhere.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How scientists tell whether land is sinking or rising
Surface movement is not enough by itself to explain what is happening underground. Researchers compare deformation with groundwater levels and, where possible, direct measurements of compaction at depth. The USGS San Joaquin Valley study found that combining surface deformation, subsurface deformation, and water-level records—especially continuous measurements—helps analyze aquifer response, estimate preconsolidation head, and calculate storage properties.
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- Groundwater wells: Track water levels, which indicate changes in hydraulic head and pressure.
- Extensometers: Measure compaction at depth within an aquifer system.
- InSAR: Uses repeated radar observations to map surface movement over broad areas.
- Continuous or campaign GPS: Tracks elevation change at fixed monuments or stations, continuously or during survey campaigns.
- Spirit leveling: Measures precise elevation differences along survey routes.
The USGS describes elevation-change measurements as fundamental to subsidence monitoring. No single method answers every question: a satellite map shows where the surface moves, while wells and extensometers help connect that movement to changing groundwater conditions and compaction at depth.
Groundwater pumping is not the only cause of subsidence
Subsidence has other causes, including drainage of organic soils, mining, natural compaction, sinkholes, and permafrost thaw, according to the USGS. A sinking surface alone does not establish that groundwater pumping caused it; the local geology, groundwater record, and deformation measurements have to support that explanation.
The scale of human influence is substantial in the United States: a 1999 USGS report estimated that more than 80 percent of identified U.S. land subsidence was a consequence of human impact on subsurface water. That is a dated national estimate, not a current or global percentage.
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