Alarming subsidence impacting China’s coastal areas poses a serious threat to millions of people, new research shows. Probe International revisits its proposed solutions from 2008.

By Lisa Peryman for Probe International

One in 10 residents of China’s coastal cities could see the land beneath their feet slip below sea level within a few decades due to land subsidence primarily caused by groundwater extraction.

According to a study of nationwide satellite data released last week by Science Magazine, an assessment of land subsidence in China’s major cities from 2015 to 2022 reveals 16% of urban lands are sinking “rapidly” (faster than 10 millimetres every year), with an even greater area of roughly 45% subsiding at a velocity of more than 3 millimeters a year, affecting 29% (67 million) and 7% of the urban population, respectively.

One of the primary drivers behind the subsidence threat is rampant groundwater extraction to meet the demands of rapid urbanization. Unprecedented in human history, China’s urban migration reached 66.2% in 2023. By comparison, in 1950 only 13% of the country’s population lived in cities. The study notes groundwater withdrawal in tandem with the weight of building expansion could sink 22 to 26% of China’s coastal lands below sea level by 2120.

Responding to the finding on groundwater withdrawal the report exposes, Chinese geologist and environmentalist, Fan Xiao, confirmed to Probe International that this was the “fundamental” cause of land subsidence in China’s cities but that the so-called “sinking of nearly half of the country’s cities” was misleading. Entire cities are not sinking, said Fan, but certain areas within cities are experiencing subsidence and these areas tend to share a common denominator. Areas with thicker aquifers experience more severe subsidence compared to those with thinner aquifers. Another factor, he said, is urbanization and the construction of high buildings, as well as the development of underground utilities such as subways.

Sinking land in China is by no means new. Shanghai and Tianjin showed evidence of sinking in the 1920s. Widespread subsidence in a number of cities has expanded in recent decades as urbanization has accelerated following China’s reform and opening policy. The rate of urbanization is projected to reach 75-80% by 2035.

According to a report on the country’s water woes, estimates suggest 70% of the country’s population relies on groundwater as their primary source for drinking water and 40% of China’s farmland uses groundwater for irrigation. In northern China, groundwater accounts for 50 percent of industrial water usage. Around the time Beijing played host to the 2008 Summer Olympics, China’s water problem had become an unwelcome headline for an event touted as a sustainability showcase.

Dai Qing, a prominent journalist well known for waging environmental fights against Beijing’s obsession with large-scale engineering works, questioned the wisdom of holding a ‘green Olympics’ in “a city so lacking of water.”

According to a Probe International report on Beijing’s water crisis released that same year, edited by Dai, the city’s 200 or so rivers and streams were parched and the city’s reservoirs nearly empty. However, the extent of the crisis and Beijing’s reliance on underground water resources had been kept “top secret,” said Dai.

“There are five underground reservoirs for tapping groundwater in Beijing but there is no stopping the city government’s plans for further expansion,” she told the Foreign Correspondents Club of China at the launch of the report.

The extraction of water underneath or near cities for use by local populations is the primary issue behind the scale of subsidence flagged by the most recent study. A problem by no means isolated to China. Groundwater loss leading to subsidence has been an issue for major urban areas around the world including Houston, Mexico City and Delhi, reports the BBC.

The BBC cited Tokyo as one example for combating and slowing decline. In an effort to address up to five metres of subsidence around the city’s port area by the 1970s, Tokyo piped in water from other areas and adhered to a law that forbade the use of well water.

Fan Xiao highlighted the example of Shanghai where subsidence had emerged as a “very serious” problem in the last century. Since then, he said, measures had been undertaken to alleviate and control the issue, including the recharging of groundwater.

With a focus on water conservation and full-cost pricing, Probe International’s 2008 report on Beijing’s water crisis proposed a range of solutions. These options included reducing demand through the use of rule of law and economic incentives, the enforcement of existing laws and regulations, and the assignment of tradable water rights to manage competing water demands. The report also looked at why water transferal from one region to another merely displaced the problem and deprived other watersheds of resources. This report is available in full here.

Related Reading

Beijing’s Water Crisis: 1949-2008 Olympics (includes 2010 update)