The Pearl River Delta region is witnessing another major salt tide due to the combined effect of an upcoming 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 Xijiang River to ensure supplies is set for completion 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 in the delta for several years. It began towards the end of last year.

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.

Guangdong has experienced a shortage in rainfall since September last year.

"The ever slower flow of fresh water from the upper reaches of Xijiang River has also led to the new salt tide," Li Jianji, director of the society, told China Daily 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 show a higher content of the main salt element, chlorine hydronium, because of the tidal phenomenon.

It is expected to reach more than 6,000 milligrams per litre.

However, the Guangdong water authority said Thursday that the new salt tide should not affect water supplies too greatly as it had conserved 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 metres 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 metres of fresh water during the diversion period.

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

The standard content in drinking water is only 250 milligrams per litre.

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

Ahead of the new salt tide, Liang's department said that a series of measures have been drawn up to better use and conserve water that has been diverted.

Editor: Yan