A powerful, massive tide is expected to sweep over the Qiantang River in Hangzhou, capital city of east China's Zhejiang Province, later this month, posing a potential danger to people outside the designated tide-watching areas, experts said yesterday.

The tidal waves are likely to reach a height of 2.5 metres much higher than that of past years on Wednesday, the 18th day of the eighth month of the lunar calendar year, the traditional tide-watching day, said Bao Yuepeng, director of the Hangzhou Water Resource Monitoring Station.

"Thanks to the strong rainfall, which swept away much of the sediment, the tide this year will be as tall and grand as it was said to be before," Bao told China Daily.

The Qiantang River bore, known as the "No 1 Tide in China" for its high tides, usually happens around the 15th day of the eighth month of the lunar year, with its climax on the 18th day.

The tide warnings labelled with five different dangerous levels are designed to warn people of the danger of the tide, and the fifth grade is the most violent one, said Lou Maoyuan, director of the Hangzhou Meteorological Bureau.

The bores at the Qiantang River on September 21 are expected to reach the fourth grade, which means huge waves and a high degree of danger.

"It will be absolutely safe for outsiders to watch the tide in the designated areas," Lou says.

To inform people of the exact time the tide will occur and avoid the possible danger for tide watchers, the local meteorological observatory has issued the tide-watching grade every day since the eve of the Mid- Autumn Day.

"Each year, many people die from tide-watching, since most of them were not quite aware of the power of the tidal waves and go beyond the designated tide-watching areas," said Lou.

Despite the attraction of the natural wonder, a combination of cold air and huge mud sediment on the riverbed of the Qiantang River resulted in low tidal waves in the previous years, disappointing most tide watchers.

The tradition for people living by the mouth of the Qiantang River to watch the tide has a history of 2,000 years, with many ancient literati leaving a rich legacy of poems and writings.

The extraordinary surging tide of the Qiantang River is caused by the gravitation of the celestial body, the centrifugal force produced by the rotation of the earth and by the peculiar bottleneck shape of the Hangzhou Bay.

The best place to watch the natural wonder is in Haining County of Zhejiang Province as well as other places nearby, including Xiaoshan and Haiyan.

(China Daily September 19, 2005)