A serious saltwater tide has been threatening the Pearl River Delta and was expected to peak today under the influence of two strong tides.

One of the tides was expected to appear at 4 a.m. today, when the moon was closest to the earth, and the other at 8:31 a.m. today, when the sun, the earth and the moon will line up, according to the Guangdong astronomy association. It¡¯s rare for two tides to appear within a span of only four hours.

Under the influence of the coming tides, 5.13 grams of chlorine per liter seawater was recorded near the Dayongkou sluice at the Pearl River mouth from Feb. 17 to Feb. 25, one of the longest saltwater tides in recent years.

Another monitoring station at the Xiaoyin sluice recorded 5.5 grams of chlorine per liter of seawater, 21 times the acceptable chlorine level, Feb. 23. The chlorine density was the highest since last autumn.

The Guangdong astronomy association said the saltwater tide would recede after tomorrow.

Experts said the frequency and density of saltwater tides had been increasing in the Pearl River Delta in recent years. One of the main reasons for that was the continuing drought, they said. The last three months in 2005 saw a record low rainfall of seven millimeters, which was only about 5 percent of the average in previous years.

Editor: Yan