New studies are showing that Chinese cities are slowly sinking as a result of rapid development and excess groundwater use. According to reports, as many as 50 cities across the country are affected by soil subsidence, including the country’s largest - Shanghai. Apparently, Shanghai has been slowly sinking for at least 90 years.
Shanghai’s business center has sunk by at least 8.5 feet (2.6 meters) since 1921. For decades, the city sank from one to five inches a year until strict groundwater pumping laws were implemented in 1996. But as China’s economy opened up to the world during the 1980s, the city’s residents and businesses depleted groundwater supplies at a faster rate. The ground beneath Shanghai is hardly solid: most of the city is perched atop 1000 feet (300 meters) of sediment, brought in over millennia by the Yangtze River. Speculation that massive construction is accelerating the city’s submersion has been the subject of blogs in recent weeks.
One example is in Pudong, Shangai’s newer business district on the other side of the Yangtze and home to the city’s modern skyline. Evidence of the city’s foundation shifting has raised more concern amongst locals. At the foot of the Shanghai Tower project, which will be China’s tallest building upon completion, a 26 foot long crack has emerged, and photos taken of it were quickly circulated on the internet. Growing speculation about safety led the Shanghai Tower’s developer to issue a statement insisting that usual settlement was behind the shift and that the project not in danger.
With the growing number of migrants moving from the countryside to cities, the continued strain on groundwater has spurred Chinese authorities to take action. The country’s land and resources ministry will try to slow subsidence by limiting groundwater withdrawal by 2015, and the plan will be rolled out across China by 2020. In the meantime, Shanghai is diverting 60,000 tons of water into its aquifers in order to reverse the trend of its cities sinking.
Via The Guardian