Salt tide, an annual natural disaster, posed a greater threat to south China's Guangdong Province earlier this year than in previous years, according to the Guangdong Provincial Department of Water Resources.

Zhuhai, a city in the province often threatened by salt tide, has been affected on September 18, according to the department.

The salt tide occurs when seawater floods coastal areas because of serious drought.

The chlorine hydronium (the main element of salt) content in the water in Modaomen Watercourse, a main channel between Zhuhai and the sea, has exceeded 6,000 milligrams per litre, while the maximum limit of content in drinking water is only 250 milligrams per litre.

The waterworks of Zhuhai had to stop taking water for two days, resulting in a lack of water supply, the Zhuhai Municipal Department of Water Resources said.

Zhongshan, another city affected, has recorded a salt tide on Friday, nine days earlier than last year. It is also the earliest salt tide in the city, according to the provincial department.

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

Just four months later, the drought came earlier than before, causing the province to encounter a new salt tide ahead of the low-water season, which should be from October to March of next year.

"Guangdong had few rainfalls after it suffered a serious flood in June, and the strong typhoon Damrey did not bring a large amount of precipitation to the province," Tu Xinjun, a professor on water resources from Guangzhou's Zhongshan University, told China Daily yesterday.

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

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

According to a provincial department report, the water of 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 lack of rainfalls.

Sea water flooded the land in most cities in the Pearl River Delta, located in the lower reaches of the Xijiang River, leading to the salt tide, according to Tu.

Tu said people can't prevent salt tide but can help cut down its damage.

The serious salt tide in May was controlled by a creative water dispatch project, he said.

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 at that time.

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

(China Daily September 29, 2005)