If New Orleans is sinking, Beijing might as well be in freefall. A new study in the journal Remote Sensing finds depleted groundwater is causing the Chinese capital—the growing Chaoyang district, in particular—to sink as much as four inches per year; a recent study found New Orleans was sinking up to two inches per year. As CNN reports, Beijing is the world's fifth most water-stressed city, using an estimated 3.5 billion liters per year—two-thirds of which comes from groundwater accumulated over millennia. As the water is extracted, surrounding soil dries up and compacts. Researchers, who used satellite imagery and GPS data, say Beijing has sunk about 14 inches in the last decade alone. The weight of new buildings and roads is also playing a role, per Christian Science Monitor.
Researchers predict the continued subsidence will produce "a strong impact on train operations" in the city. A separate study on subsidence effects is due out later this year, per the Guardian. In the meantime, the sinking could be eased by proper enforcement of groundwater pumping regulations. "There are some rules but the enforcement is doubtful," one Chinese environmentalist says. Beijing could also learn from Shanghai, which was sinking at about four inches per year in the 1950s and '60s but now falls less than half an inch annually after opting to use river water for daily use. Last year, China began building tunnels and canals to alleviate stress on aquifers. But elsewhere, concerns are greater. Mexico City and Jakarta are sinking up to 11 inches per year, researchers say. (Parts of this US state are also sinking.)