New Delhi, India—A critical study published in Nature Sustainability has issued a stark warning that several of India’s largest metropolitan areas, including Delhi, Mumbai, Chennai, Kolkata, and Bengaluru, are experiencing significant land subsidence a gradual sinking of the ground due to unsustainable groundwater extraction.
Using eight years of satellite radar data, researchers found that the ground is compressing as water is pumped from underground layers faster than it can be naturally replenished. This process puts nearly 1.9 million people at risk in areas subsiding faster than four millimeters each year, with over 2,400 buildings already at high risk of structural damage. If current trends continue, projections show more than 23,000 buildings could face very high risk within the next five decades.
Over-Extraction Drives Structural Damage
The study confirms that groundwater overexploitation is the dominant factor driving the sinking across all five megacities. As water pressure is lost in the underground compressible aquifer layers, the soil and rock compact, leading to measurable sinking of the land surface over time. Chennai and Delhi face the most worrying levels of subsidence, with areas like Delhi’s Bijwasan, Faridabad, and Ghaziabad, and Chennai’s Adyar river floodplain, showing the fastest rates of decline.
Crucially, the research highlights that sinking rates are often unequal across a city, which causes differential settlement the uneven sinking of the ground beneath a structure. This unevenness creates strain that weakens foundations, a finding that applies disproportionately to densely populated, informal settlements like Mumbai’s Dharavi, where poorer neighborhoods are sinking faster due to greater dependence on groundwater and thinner foundational structures.
As Nitheshnirmal Sadhasivam, a co-author of the study, noted, their motivation was to address the absence of prior research explicitly linking land subsidence to structural damage risk in Indian cities, a geohazard well-recognized globally in places like Jakarta and Mexico City.
A Compounding Urban Hazard
Land subsidence is compounding India’s existing urban vulnerabilities, especially concerning flooding and climate change. When the ground sinks, it alters drainage patterns and lowers the surface elevation, severely impairing a city’s capacity to discharge floodwaters, thereby making even moderate rainfall more destructive.
M. Rajeevan, former Secretary of the Ministry of Earth Sciences, emphasized that subsidence adds a dangerous new dimension to the climate vulnerability of Indian cities already struggling with sea-level rise and intense tropical cyclones. Inland areas like Delhi, built on soft alluvial soil and facing intense groundwater depletion, are particularly susceptible.
However, the study also offers a blueprint for mitigation. Regions like Dwarka in southwest Delhi showed signs of ground stabilization following the implementation of groundwater recharge programs and extraction restrictions, demonstrating that targeted policies can help slow the rate of sinking.
Need for Predictive Resilience
Experts are calling for an urgent policy overhaul to address the risk, noting that current building codes lack provisions for the long-term monitoring of ground deformation. The way forward involves a combination of strict groundwater governance and advanced technology. The upcoming NASA–ISRO NISAR satellite mission is expected to transform monitoring capabilities, providing high-resolution radar imaging that can detect millimetre-scale ground movement in near real-time.
Scientists agree that integrating such satellite data into hydrological models and city planning will enable India’s megacities to move from a reactive approach to one of predictive resilience, protecting vast urban infrastructure and the millions who rely on it.