The Slow Collapse: What Happens When Groundwater Runs Out Beneath Cities

The Hidden Architecture of Our Cities

Most people never think about what's beneath their feet when they walk through a city, but the truth is startling. Buildings, roads and even the soil itself all put pressure on everything below them. The ground beneath consists of several layers of sediment, including aquifers with a lot of porous space between sediment grains. Water fills the spaces and helps support some of the weight from above. Think of it like a giant sponge holding up your entire world. When water is removed and soil is compressed, the land is weighed down. This underground architecture has been supporting human civilization for millennia, but we've only recently begun to understand how fragile it really is.

America's Sinking Crisis Revealed

At least 20% of the urban area is sinking in all cities, mainly due to groundwater extraction, affecting ~34 million people. A groundbreaking 2025 study using satellite data revealed something that shocked even the researchers themselves. Researchers mapped out how land is moving vertically across the 28 most populous U.S. cities and found all the cities were compressing like a deflated air mattress to some extent. Twenty-five of them are dropping across two-thirds of their land. About 34 million people — about 10 percent of the U.S. population — live in the subsiding areas. This isn't just a coastal problem anymore — it's happening everywhere, from Chicago to Denver, affecting millions who have no idea their homes are slowly sinking.

The Thirsty Cities of the American West

Phoenix, Arizona: The Phoenix metro area has recorded annual subsidence rates of up to 3.5 inches (9 cm), making it one of the fastest-sinking inland cities. According to the study, "notable subsidence greater than 5 mm per year" was observed in Phoenix, with 98% of the city experiencing some level of land sinking. The region's dependency on groundwater during long droughts has led to significant aquifer depletion. In Las Vegas, the situation is equally dramatic. Subsidence in the Las Vegas Valley has also reached 3.5 inches per year in certain locations. The researchers noted two particularly vulnerable neighborhoods: Northgate and Los Prados. These areas are sinking at rates above 5 mm per year, a threshold known to heighten risks to roads, utilities, and buildings.

Texas: Where Everything Really Is Bigger

In Texas, the subsidence problem reaches epic proportions. Texas is home to the fastest subsiding places in the country, which pump groundwater but also a lot of oil and gas. Houston has long been known for sinking at the fastest rate, more than 5 millimeters per year. But the team found several other Texas cities further inland moving at similarly high rates, including Dallas and Fort Worth. The country's fastest sinking metropolis, Houston, has 40 percent of its area dropping more than a fifth of an inch annually, with another 12 percent of its land subsiding at twice that rate. Parts of the city have already sunk by several feet, the result of decades of people pumping out too much groundwater and too much fossil fuel. Houston already struggles with flooding from hurricanes and rainstorms made worse by climate change, while subsidence creates depressions for all that water to accumulate.

The Great Water Heist

Whereas natural processes influence urban land subsidence in the United States, most of the sinking land results from human-driven activities, with 80% of the subsidence associated with groundwater withdrawals. We're essentially stealing water from the future, and the earth is sending us the bill in the form of sinking cities. Groundwater over exploitation compacts the underground reservoirs because water is the element partly responsible for holding up the ground. The excess water withdrawal leads to compaction of the underlying depleted porous formation thus inducing land subsidence. It's like removing the filling from a sandwich and wondering why it collapses.

When Floods Meet Sinking Ground

Sinking land exacerbates flooding risks because it can trap stormwaters for longer periods, Shirzaei said. For instance, during Hurricane Harvey in 2017, he found that 85 percent of the flooded area in the Houston-Galveston area subsided by more than 5 millimeters per year. During Hurricane Helene in 2024, subsided areas may have made it harder to clear the flooding in the following days. "Land subsidence changed the drainage network so water could not drain out of the city," Shirzaei said. It's a cruel irony — cities sink because they need water, but when water finally arrives as floods, the sinking ground makes the disaster even worse.

Jakarta: The Fastest-Sinking City on Earth

Jakarta is sinking. And it's doing so at a rate faster than any of the world's megacities — from 1 centimeter (about half an inch) a year in some areas, up to 20 cm (8 in) in the worst-affected areas, like here in northern Jakarta. The worst case is Indonesia's capital, Jakarta, with parts of the port city sinking as much as 10 in (25 cm) per year. Today, 40% of the city is below sea level, protected by a 6 ft (2 m) seawall. At the current rate of subsidence, more than a third of the city could be submerged by 2050. The Indonesian government has made the unprecedented decision to abandon their capital city entirely, relocating to Borneo by 2045. But that still leaves 11 million residents behind.

Mexico City: Built on Ancient Waters

That lake bed was once Lake Texcoco, home of the Aztec city Tenochtitlán. As water extraction drove groundwater deeper underground, the 100-meter-thick, salty, clay-rich lake bed was left high and dry. Its very fine mineral grains have since been steadily repacking themselves more tightly, causing the ground to shrink and subside. That kind of compaction is irreversible, the researchers report, and it's responsible for the appearance of extensive fractures that damage buildings, historical sites, sewers, and gas and water lines in the city. Although it is not on the coast, Mexico City was built on a dried-up lakebed, and groundwater extraction from underlying aquifers has caused more than 12 in (30 cm) of subsidence in some parts of the city in some years—even more than in Jakarta taken as a whole.

Venice: The Floating City That's Still Sinking

Venice, the romantic city of canals, has been fighting subsidence for decades. Probably the most famous example of a sinking city is Venice in Italy. The city is sinking at around 1 to 2 mm a year. Best known for its extensive waterways and romantic history, the city is built in a muddy lagoon with inadequate foundations. However, Venice represents a success story. Venice also managed to get a grip on subsidence. The world heritage in the Italian lagune was sinking due to a combination of compaction of sediments and water extraction beneath the city. The city's administration stopped extracting groundwater and now acquires its drinking water from the Italian mainland. As a result, Venice now sinks by only one millimetre per year.

The Infrastructure Nightmare

Even modest rates of urban subsidence can profoundly impact the structural integrity of buildings, roads, bridges and dams. While often considered solely a coastal hazard due to relative sea-level rise, subsidence also threatens inland urban areas, causing increased flood risks, structural damage and transportation disruptions. Underground pipes and cables are vulnerable to ground movement. Water mains and sewers can crack or collapse, leading to leaks and contamination. Gas pipes may rupture, creating explosion risks. Electrical and communication lines can be damaged or severed. This disrupts power and internet services to homes and businesses. Roads and railways can develop bumps, dips, and cracks. These make travel dangerous and require frequent repairs. Bridges and overpasses are at risk of structural failure if their supports shift.

The Building Tilt Phenomenon

Damage to critical infrastructure can occur when a city experiences different levels of subsidence across a small area. For instance, a building sitting on partly elevated and partly sinking ground is more likely to be destabilized. It doesn't take a large difference in elevation either. Across the 28 cities, the densest urban cores had issues with precarious destabilized ground — threatening 29,000 buildings. If an urban area sinks at a uniform rate, it might not be much of an issue since all the infrastructure would be moving together. But the problem, the researchers find, is "differential subsidence," where the rates differ on a small scale. If one end of a building sinks a quarter of an inch a year and the other end sinks a third of an inch, the difference will destabilize the building's foundation.

The Global Scale of the Crisis

Our assessment shows that 5% of the global area and 25% of the population are affected by significant land subsidence. These numbers are expected to rise, as changing climate, increasingly prolonged periods of drought, and growing population only exacerbate global dependency on groundwater. By combining publicly available data with the predictive capabilities of computer modeling, they found global aquifer storage capacity is disappearing at a rate of approximately 17 km3 per year (about the size of 7,000 Great Pyramids of Giza). This loss of groundwater storage is permanent, forever reducing the amount of water that can be captured and stored. Approximately 75% of this subsidence is occurring over cropland and urban regions, underscoring the importance of improving groundwater management globally.

Economic Devastation

Subsidence causes significant financial harm to property owners and communities. It reduces real estate values and leads to costly repairs. Homes affected by subsidence often lose market value. Buyers are wary of properties with a history of sinking or structural issues. This can make it hard to sell or refinance. Insurance costs may rise for homes in subsidence-prone areas. Some insurers even refuse to cover properties with subsidence problems. This further lowers their appeal and value. High maintenance costs for roads, railways, pipelines, and buildings are only a few examples of stresses brought upon by land subsidence. Although it is a gradual process, taking years to decades to develop, land subsidence presents serious socioeconomic, environmental and security challenges globally.

Water Wars: The Human Story

Forty percent of Jakarta is already below sea level, but the main reason why the city is sinking is not climate change. Instead, it's a thirst for clean water. Less than half of the city's population has access to piped water, leading to a proliferation of wells and pumps, often installed illegally. Massive groundwater extraction is one of the main drivers of land subsidence in Jakarta, a sprawling concrete labyrinth that's not supported by a reliable water supply network. Jakarta's piped-water system serves fewer than one million households, a little over a quarter of the city's total. The rest rely primarily on pumping groundwater. But the provincial government is unable to monitor and tax the untold numbers of unregulated deep wells scattered across the city, mostly hidden behind closed doors.

The Climate Change Amplifier

The report adds a climate warning. As prolonged droughts reduce surface water supplies, cities turn more aggressively to groundwater. That, in turn, leads to further aquifer depletion and land subsidence. The study states: "The compounding effect of climate change and urban population and socioeconomic growth emerges as a critical concern, potentially accelerating subsidence rates." In the Colorado River Basin—where declining reservoir levels and a drying climate already threaten water security—subsidence adds a new layer of complexity. As urban areas grow — and as climate change exacerbates droughts, especially in the American West — their people and industries demand more water.

Managed Aquifer Recharge: A Ray of Hope

Managed aquifer recharge (MAR) – through mitigating groundwater over-extraction – has been used as a tool to mitigate land subsidence in many regions around the world. Managed aquifer recharge (MAR) – through mitigating groundwater over-extraction – has been used as a tool to mitigate land subsidence in many regions around the world. MAR has been used with significant success to slow or stop land subsidence in many areas. MAR can mitigate land subsidence through injection wells, which normally require a supply of high-quality surface water. The water can be used to offset the groundwater withdrawals that are producing the subsidence, which contributes to water resilience. Well-formulated Flood-MAR projects can benefit Californians and the environment through improved water supply reliability, flood-risk reduction, drought preparedness, aquifer replenishment, ecosystem enhancement, subsidence mitigation, water quality improvement, working landscape preservation and stewardship, climate change adaptation, recreation, and aesthetics.

Success Stories: Cities That Fought Back

Similar measures taken in Bangkok (Thailand) halted subsidence. 'Bangkok was sinking by some ten cm per year when the director of the water management institute took a bold decision. Despite protests, he decided to shut down many pumps and levy hefty taxes on the extraction of groundwater. Strict enforcement was also introduced. The city invested in alternative water sources. All of these measures have stabilised the situation in Bangkok. A true story of success.' Tokyo, for example, faced similar land subsidence challenges in the 1940s when factories began utilizing enormous amounts of groundwater. Underground aquifers were drained and caused land subsidence of up to 4.5 metres in some areas – a number very similar to the land subsidence in Jakarta. Once the severity of the problem was recognized, city officials began by disseminating information on groundwater usage to raise awareness of the issue. New policies were adopted and laws enacted to limit or even prohibit groundwater usage, particularly for industrial purposes. The government invested heavily in infrastructure, including several seawalls, an extensive drainage system, pumping stations, floodgates etc., to help mitigate the risk of flooding from sea level rise.

Technology to the Rescue

The frontier for MAR today clearly lies in the safe reuse of reclaimed water through sub-surface solutions, which typically have much smaller land footprints than surface water storage and hence are well-suited for urban and peri-urban contexts, provided proper nature-based solutions are incorporated to protect groundwater from contamination. Newer technologies for water reuse, such as membrane aerated biofilm reactors (MABR), can improve many different kinds of source water from stormwater to sewage at lower energy