Fresh water supplies to Hong Kong and Macao could be affected if the present severe salt tide in South China's Guangdong Province continues to flow, it was claimed yesterday.

The tidal phenomenon, caused by drought, is at its worst in several years. Salt water levels in some local rivers in the province were 12 times higher than standard drinking requirements earlier this month.

"If the salt tide goes further, it will affect the water supply across the Pearl River Delta region, including Hong Kong and Macao," said Li Jianji, an official from the Guangdong Provincial Astronomers Society.

He blamed a shortage of rainfall and the effect of a powerful tidal pull, caused by a particular formation of planets upcoming on December 31, for the emergence of the salt water tide.

"Water in Hong Kong and Macao, which neighbours Guangdong, comes mainly from the province," Li told China Daily.

Supplies to the eastern Pearl River Delta region, such as Guangzhou, Dongguan, Shenzhen and Hong Kong, is currently guaranteed as water levels in the Dongjiang River, the cities' water source, remains high due to water diversion, according to Huang Qiangliang, vice-director of Guangdong Department of Water Resources.

The Guangdong water authority introduced water rationing in the area of the Dongjiang River from mid-December to control levels.

As a result, the river's salt content has been diluted, Li said.

The water rationing project will last until April next year, when the drought season is expected to end, in a bid to ensure water quality for residents' use, according to Li.

Sources with the authority added that a new water diversion project from Beijiang River in northern Guangdong to Xijiang River will be introduced early in January next year, to better combat the salt tide.

The Xijiang River is currently the most severely affected area by the phenomenon.

Macao's water supply could be greatly affected if the salt tide continues in Zhuhai of Guangdong, which draws most of its water in Xijiang River. At present, nearly 99 per cent of supplies in Macao come from Zhuhai.

The drinking water content of chlorine hygronium, the main salt element, in Zhuhai has been controlled at 800 milligrams per litre.

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

"There is only one reservoir in Macao, and if Zhuhai is greatly affected by the salt tide, the water supply in Macao will also be severely affected," said Chen Zhuhuang, an official with the Zhuhai Water Supply Company.

Editor: Yan