Guangdong Province is under threat of a "salt tide" that could severely affect its water supplies, according to the Guangdong Provincial Department of Water Resources.

The salt tide, which happens every year, occurs when water reserves dry up in a drought, only to make way for seawater to flood them.

The chlorine hydronium - the main element in salt - content in the water in Modaomen Watercourse, a main channel between Zhuhai and the sea, has exceeded 6,000 milligrams per liter, much higher than the maximum 250 milligrams per liter limit allowed in drinking water.

Zhuhai City, which has been grappling with the problem since September 18, cut off water reclamation for two days, the Zhuhai Municipal Department of Water Resources said.

From the end of last year to May 2005, Guangdong experienced the most serious salt tide "attack" in two decades as a result of a severe drought in South China.

"Guangdong had little rainfall after it suffered serious floods in June, and Typhoon Damrey did not make much of a difference to levels of precipitation," Tu Xinjun, a professor on water resources from Guangzhou's Sun Yat-sen University, told China Daily yesterday.

"The salt tide will be more serious from January to March next year, as past experience indicates," Tu added.

The water volume in all of Guangdong's reservoirs only increased by 140 million cubic meters after Damrey hit, too little to ease the drought.

According to a provincial department report, the water in the Xijiang River, which runs through southern Guangdong Province and the Guangxi Zhuang Autonomous Region, was reduced by 52.9 percent from last year because of drought and the lack of rainfall.

Tu said salt tides can't be prevented but the damage caused can be mitigated. 

He gave the example of a creative water dispatch project carried out in May in which the Ministry of Water Resources ordered the provinces in the upper reaches of the Xijiang River to discharge 851 million cubic meters of water to Guangdong.

The Guangxi Zhuang Autonomous Region and Guizhou Province participated in the dispatch project. The discharged water flowed over more than 1,000 kilometers in 18 days to the salt tide-affected areas.

(China Daily September 29, 2005)