The Pearl River Delta region is witnessing another major salt tide due to the combined effects of a tidal pull and a prolonged drought.

It comes at a time when a diversion project directing water from Guangdong's northern Beijiang River to the lower reaches of the Xijiang River is due to be completed soon.

The scheme, which started in mid-January, has already helped cities along Xijiang River, including Zhuhai and Zhongshan, better control the worst salt tide that the delta has seen in years.

However, another powerful tidal pull over the course of this weekend, coupled with the long-term drought in south China's Guangdong Province, will cause another major salt tide in the area, sources with the Guangdong Provincial Astronomers Society said.

"The flow of fresh water from the upper reaches of Xijiang River is continually slowing down, which is another reason for the new salt tide," Li Jianji, director of the society, told China Daily on Thursday.

The new salt tide is expected to last until Tuesday, according to Li.

Water in the Dayongkou in the lower reaches of Xijiang River will have higher concentrations of salt and chlorine hydronium because of the tidal phenomenon.

They are expected to reach more than 6,000 milligrams per liter.

The national standard for chlorine hydronium in drinking water is only 250 milligrams per liter.

However, the Guangdong water authority said on Thursday that the new salt tide should not affect water supplies too greatly as it has been conserving large quantities of fresh water since the start of the water diversion project.

"Fresh water supplies to Zhuhai, Zhongshan and Macao will be guaranteed during the upcoming Spring Festival," said Huang Qingliang, vice-director of the Guangdong Department of Water Resources.

Sources with the department said that a total of 3,500 cubic meters of fresh water have been diverted to some small rivers and reservoirs along the lower reaches of Xijiang River.

Zhuhai, a city that has been severely hit by previous salt tides, has reserved nearly 1,600 cubic meters of fresh water.

As a result, the content of chlorine hydronium in drinking water has reduced from 800 milligrams per litre to 400 milligrams in Zhuhai.

The salt content of supplies to Macao, which relies mostly on Zhuhai for its fresh water, has returned to normal levels.

(China Daily January 27, 2006)