Water diversion from northern Guangdong's Beijiang River to its western Xijiang River is expected to start in mid-January to control the severe salt tide, an official with the local water authority said yesterday.

Fresh water supplies in the southern Chinese province is currently seriously affected by the tidal phenomenon, caused by drought, which experts said will last until April.

It has seriously affected the Xijiang River, which is the main water source for Zhuhai and Macao.

The water authority in Zhuhai is introducing fresh water from the upper reaches of Xijiang River to dilute the salt content before the Beijiang diversion scheme begins. It follows the end of a powerful tidal pull, caused by the particular formation of planets.

The tidal pull has increased the salt content in the Xijiang River, but with its ebbing, fresh water from the upper reaches of the river will also flow into the city.

"It is a good time for us to store fresh water to curb the salt tide," said Chen Zhuhuang, an official with the Zhuhai Water Supply Company.

Now the fresh water from the upper reaches of the river is coming into the city at about 1,400-1,800 cube meters per second, higher than usual.

It is expected that the city will store a total of 20 million cube meters of fresh water in the days to come.

At present, the content of chlorine hygronium, the main salt element, in some water gates in Zhuhai exceeds 4,000 milligrams per liter, which will be reduced dramatically after the introduction of fresh water.

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

Thousands of residents in the city have had to fetch fountain water and buy bottled water for daily use as the content of chlorine hygronium in water from taps still remains high at 800 milligrams per liter.

Zhongshan, another city affected by the salt tide, has also diverted fresh water into Zhuhai.

Residents in Zhuhai and Macao, which draw most of its water from the Xijiang River, are expected to use drinking water with salt content to be leveled beneath 800 milligrams per litre within the upcoming days thanks to the diversions, according to Chen.

"However, the fresh water to be stored can be only used for 20 days, and the city may encounter another more powerful tide pull in mid-January," Chen said.

"As a result, the water diversion project from Beijiang River to Xijiang River is currently urgent."

The city is also waiting for another powerful tidal pull, which is expected to occur in about 10 days, to introduce more fresh water from the upper stream of the Xijiang River.

"As the upcoming tidal pull will cause another serious salt tide, which will increase the salt content in the river, the water diversion from the Beijiang River will start as soon as possible," Chen said.

The Beijiang River, which was heavily polluted by cadmium, a toxic chemical early in December last year, has returned to a safe situation.

"The water diversion from the Beijiang River is only part of short-term measures, as it will also cause fresh water shortage there," Chen said.

As a result, another long-term water diversion project from Guizhou Province and Guangxi Zhuang Autonomous Region, which neighbors Guangdong Province in the west, will be completed in 2007.

(China Daily January 5, 2006)