Subsidence brings down Yangtze Delta
By Bao Xinyan (China Daily)
Updated: 2005-03-22 07:35

NANJING: Shanghai has sunk by nearly 3 metres over the last 80 years, causing damage worth 14.5 billion yuan (US$1.7 billion), according to a report.

The report also shows that 16 provinces and regions in China, and 46 major cities also suffer from subsidence.

A bird's eye view of Lujiazui, Shanghai [newsphoto/file]

Researchers believe the pumping of underground water is causing the problems.

The situation was discovered in a report on underground water resources in the Yangtze River Delta, and elsewhere, as well as other geological problems.

The report shows that south of the Yangtze River, the land has sunk by an average of more than 20 centimetres over an area of almost 10,000 square kilometres.

Subsidence

The most serious ground subsidence occurs in the urban districts of Shanghai Municipality and Suzhou, Wuxi and Changzhou in East China's Jiangsu Province, and Jiaxing in Zhejiang Province. Subsidence here can reach 2.63 metres.

Suzhou, Wuxi and Changzhou have lost 2.575 billion yuan (US$310 million) because of subsidence that affects both urban and rural areas.

It causes damage to buildings and problems such as floods on farmland.

Guo Kunyi, vice-director of the Nanjing Geological Survey Centre and the person in charge of the report, said land subsidence is mainly a result of the excessive pumping of underground water.

He stressed that underground water was not unlimited, but could be pumped with restrictions.

According to Guo, replacing underground water could prevent further land subsidence.

Monitoring machines

The government should also pay attention to the investment of monitoring machines and survey equipment, Guo added.

Most evidence of problems underground comes from cracks and subsidence, which should be checked.

This means effective measures can be taken to prevent further subsidence before it is too late.

The report was also written by researchers from the geological departments of Jiangsu and Zhejiang provinces and Shanghai Municipality.

It took them almost five years to complete their task. The survey cost more than 40 million yuan (US$4.8 million).

The Yangtze River Delta has a long history of land subsidence which can be traced back to the 1920s.

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