China's Dams

Largest network for monitoring sinking land OK’d


February 10, 2007

China’s largest network for monitoring land subsidence, or land sinking, has passed appraisal tests, the China Geological Survey, a bureau of the Chinese Ministry of Land and Resources, said yesterday.

The network, focusing on Suzhou, Wuxi and Changzhou cities in east China’s Jiangsu Province, covers 30,000 square kilometers of land along the Yangtze River valley. Experts from the geological survey bureau said the network has begun to play an important role in controlling land subsidence on the Yangtze River Delta.

Besides the Suzhou-Wuxi-Changzhou network, another land subsidence monitoring network, covering nearly 5,000 square kilometers, has been launched for the Hangzhou-Jiaxing-Huzhou city group in Zhejiang Province. Shanghai is the Chinese city most affected by land subsidence. According to the bureau, the metropolis has records of land subsidence dating to 1921, and has seen 1,000 square kilometers of land subside, at depths of up to 2.6 meters. Land subsidence has cost Shanghai more than 100 billion yuan (US$12.9 billion). The city loses 10 million yuan when the land subsides by one millimeter.

The Suzhou-Wuxi-Changzhou city group in Jiangsu is also seriously affected. About 5,700 square kilometers of land, or half of the total area of the three cities, subsided, with the deepest subsidence measuring 2.8 meters. The geological survey bureau said more than 70 Chinese cities suffer from land subsidence. Inappropriate siphoning of underground water and poorly thought-out urban construction projects have contributed to land subsidence, said Lin Xueyu, an academician with the Chinese Academy of Sciences.

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