Beijing, Venice, and Mexico City have something in common—they're all sinking.
A new study led by Beijing-based researchers used radar to survey land elevation and found that the Chinese capital has sunk an alarming 14 inches in the last decade. Some districts are sinking by as much as four inches (11 centimeters) per year, CNN reported.
While the Forbidden City, the CCTV tower, and the bird’s nest like Beijing National Stadium aren’t at risk of disappearing into a sinkhole anytime soon (smog would take them out of the picture first), the sinking could affect buildings and public works projects. The city is most nervous about the impact on the rail network, which transports millions of the city’s workers each day. “We are currently carrying out a detailed analysis of the impacts of subsidence on critical infrastructure (e.g. high-speed railways) in the Beijing plain,” the study’s authors wrote in an email to The Guardian. “Hopefully a paper summarizing our findings will come out later this year.”
One of the culprits behind the sinking city is that Beijing’s nearly 20 million residents have helped drain the subterranean aquifers that maze across the city. As the underground caverns empty, the soil compacts. As Beijing continues to expand with tall buildings, new roads, and other large-scale construction projects, the city is slowly dropping into the now-empty aquifers with the bustling Chaoyang district being the most effected area by the sinking.
If a slowly lowering city wasn’t troubling enough, the groundwater is the main source of water for most of the city’s denizens. As it disappears, so do options for drinking water. In 2015, China began a massive engineering project to divert water to the capital in the hopes of mitigating Beijing’s water crisis.
For more advice on how to slow their descent, Beijing need look no further than Shanghai. According to the Christian Science Monitor, back in the 1950s and ‘60s Shanghai was sinking by up to four inches a year, but by switching from groundwater to river water, they were able to slow that down to just 2/5 of an inch a year.