Despite the city's vigorous efforts to control the ground subsidence problem, downtown Shanghai is still sinking, according to a report recently issued by the municipal water authority.

Shanghai sunk 11.02 millimeters in 2000, and the figure is not expected to see a radical reduction in the near future, the report said.

The report presented to the municipal government was based on a general survey of the city's water resources conducted by the water authority over the past two years.

"The surface subsidence at the speed of 10 millimeters a year is internationally allowable," said Ruan Renliang, director of the Water Resources Management Division of Shanghai Water Authority.

"We still face challenges to get it under control for effective urban management and sustainable development of such a populous metropolis," he said.

Due to excessive exploration of underground water, Shanghai suffered a severe annual subsidence of 37.6 millimeters from 1921 to 1965.

The government since then has taken administrative actions to mitigate the situation.

The water authority set limits on the yearly total amount of underground water that could be used and fixed a water quota for manufacturers.

Meanwhile, big water consumers such as steel factories are obliged to re-pump a certain amount of tap water, in proportion to the water they use, back into the underground.

The measures were effective but since 1998, the slowed subsidence has gained momentum again. Due largely to the growing number of high-rises being built and underground construction, subsidence hit 11.13 millimeters a year.

In 2001, Shanghai had 142 million cubic meters (5,015 million cubic feet) of usable underground water, but actually only around 8,000 (282,517 cubic feet)-9,000(317,832 cubic feet) cubic meters of water will be consumed.

Some 14 million cubic meters will be poured back into the underground this year in an attempt to control the subsidence speed.

"It takes time for the limiting of the water exploration to show its effect in stopping the downtown area from sinking," Ruan said.

Ruan assured the public that Shanghai is well equipped to control the problem, and that plans for the construction of a strong anti-flood wall will keep any threat to the city at bay.

(China Daily November 13, 2001)