Half of China’s Cities Sinking, Imperiling Millions: Groundwater Extraction and Urban Weight at Fault

A startling revelation emerges from a recent study: nearly half of China’s major cities are sinking, their descent driven by a combination of groundwater extraction and the burgeoning weight of urban infrastructure. This alarming trend poses a significant threat to millions of people residing in these urban centers, potentially exposing them to flooding and irreversible damage within the next century.

Published in the journal Science, the study scrutinized land subsidence in all Chinese cities with populations exceeding 2 million inhabitants between 2015 and 2022. Shockingly, 45% of these cities are sinking at a rate surpassing 0.1 inches (3 millimeters) per year, with 16% experiencing even more precipitous declines of over 0.4 inches (10 mm) annually.

These sinking cities, home to three-quarters of China’s urban populace, face a dire predicament exacerbated by factors like groundwater withdrawal and the relentless expansion of high-rise buildings and transportation networks. Coupled with rising sea levels, this phenomenon threatens to inundate coastal regions, imperiling an estimated 55 to 128 million individuals by 2120.

Satellite data from the Sentinel-1 satellites, coupled with groundwater assessments and building weight data, unveiled the magnitude of the problem on a national scale. The study delineated a strong correlation between city subsidence and groundwater depletion, with anthropogenic activities accounting for the lion’s share of this loss.

Urban transportation systems, hydrocarbon extraction, and mining further compound the issue by creating voids in the earth’s crust that eventually collapse and consolidate, exacerbating subsidence. The study underscores the imperative of curbing groundwater extraction to mitigate this existential threat.

The ramifications of city subsidence extend beyond mere land deformation; they imperil infrastructure integrity and exacerbate flood risks, particularly in coastal cities. If left unchecked, sinking cities along China’s eastern seaboard could plummet below sea level, with up to 26% of the nation projected to submerge within the next century.

Experts concur that emulating successful interventions, such as those witnessed in Tokyo, holds promise for averting catastrophe. By implementing stringent measures to curtail groundwater extraction, cities can thwart the downward spiral and safeguard their inhabitants from the perils of subsidence-induced calamities.