Over half of China's 668 cities are facing severe shortages of adequate underground water.

Illnesses related to unhygienic water still exist in many areas, leaving over 70 million people using sub-standard underground water, according to a recent report from the Ministry of Land and Resources.

The report is based on the country's second national survey on underground water resources which was started in year 2001 and wrapped up earlier this year.

It is time for local governments to impose stricter measures to improve the situation, said Jiang Jianjun, director of the Geological Environment Department under the ministry.

Jiang said excessive exploitation of underground water is to blame for most of the troubles.

According to him, the country's extraction of underground water has increased by an average annual rate of 2.5 billion cubic metres over the past two decades and reached a total of 119.1 billion cubic metres last year.

Underground water now comprises 30 per cent of the country's total urban water supply, but due to environmental problems caused by excessive extraction, only 63 per cent of China's urban areas enjoy underground water that is potable without treatment.

One explanation of this is that the same amount of pollutants now has less water to dilute, said Xu Huizhen, an expert with the China Institute for Geo-Environment Monitoring.

But the negative impact goes beyond deteriorating underground water quality. Land subsidence and the invasion of sea water are other major concerns.

"Most of these negative impacts were not very noticeable initially, but now they are too huge to be ignored," said Xu.

For example, severe ground subsidence might have drastically increased tidal plains in some of Zhejiang Province's seaside cities by 2030.

"But before that (year 2030), the invasion of sea water to take up the place originally occupied by fresh underground water might have already given local people a hard time," said Yu.

"Serious invasion of sea water might leave those cities little good fresh underground water to use."

(China Daily November 3, 2003)