More than 300 of China's 657 cities are short of groundwater, with over 70 seeing land-subsidence hazards due to exploitation, including Shanghai.
The overdrafting of water has formed around 150,000 square kilometers of sinking areas, from Harbin in the northeast to Haikou in the far south, from Shanghai in the east to Urumqi in the west, said Wang Guangqian, a member of the Chinese Academy of Sciences.
Authorities tested small amounts of toxic pollutants in underground water in cities and suburbs in the Yangtze River Delta, Zhujiang River Delta and the Beijing area, said the Ministry of Land and Resources.
It announced that the underground water quality is better in south China, where 90 percent is of high grade, and in mountain areas compared to the plains areas. The coastal areas tested as the poorest in the research.
The situation has improved somewhat in eastern China while worsening in northern China, the ministry said.
More than 400 cities nationwide use groundwater, the ministry said, adding that in northern China more than 65 percent of household water, 50 percent of industrial water and 33 percent of irrigation water comes from aquifers.
The excessive exploitation and the contamination pose great threats to the safety of drinking water, the ministry said.
Large amounts of sewage, including industrial discharge and pesticides, have leaked into aquifers, deteriorated the water quality and to some extent decreased the storage of the recoverable water, which is clean and safe.
"It needs at least decades to clear the tainted underground water," said a professor who wished to remain anonymous. "It's also hard to monitor the underground water pollution."
The Chinese Academy of Geological Sciences said in a research paper that nearly 4 billion cubic meters of groundwater was excessively extracted in the North China Plain every year. The region, in fact, can't draw any more, it said, because it has essentially sucked the aquifer dry.
Meanwhile, nearly 72,000 square kilometers of land surrounding the Bohai Sea has subsided in the last 50 years. The over-exploitation causes cracks in the ground and poses great threats to the urban infrastructure.
Shanghai, Tianjin, and Taiyuan, capital of north China's Shanxi Province, have sunk more than two meters. In February, a 10-meter-long road crack emerged in the Lujiazui area, Shanghai's financial zone.
More than 300 of China's 657 cities are short of groundwater, with over 70 seeing land-subsidence hazards due to exploitation, including Shanghai.
