Fresh water supplies in South China's Guangdong Province are being severely threatened by salt tides.

The annual natural problem is currently the worst it has been for several years and officials have been working to control it since the autumn, a local water resource official said yesterday.

"The biggest saltwater tide this year has now reached the province and it will last for eight days until January 3 next year," said Huang Qingliang, vice-director of the Guangdong Department of Water Resources.

According to the department, the content of chlorine hydronium, the main salt element, in the Dayongkou, a main water gate in the lower reach of Xijiang River, reached 7,500 milligrams per litre on December 15, a record high in recent years.

Despite the government's prompt measures to control the seawater tide, it exceeded 3,000 milligrams per litre yesterday. The standard content in drinking water is only 250 milligrams per litre.

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

The drought in the Pearl River Delta region has been worsening since September. As a result, seawater is flowing into the Pearl River and its tributaries in the coastal province, Huang said.

The Xijiang and Beijiang rivers, two major tributaries of the Pearl River, witnessed their lowest-ever water levels in mid-December.

Levels in the Xijiang River, which runs through the Guangxi Zhuang Autonomous Region and the southern Guangdong Province, reached a record low of less than 0.12 metres several days ago.

Official statistics show levels fell by 52.9 per cent from last year because of drought and lack of rainfall.

Experts said that if the drought continues in the province, the serious salt tide is expected to last until February and March next year.

"Winter and spring are often seen as the low water seasons in the province, and it may encounter a lasting severe salt tide in early next year," Huang said.

From the end of 2004 until May this year, Guangdong also experienced a serious salt tide as a result of the severe drought in South China.

Just four months later, the drought came in September, earlier than usual, causing the southern Chinese province to encounter another salt tide ahead of the low water season.

According to Huang, his department has worked together with other governmental institutions to draw up prompt measures to control the salt tide.

"One of the effective ways is to introduce more fresh water into the Pearl River, to reduce the high content of chlorine hydronium," Huang said.

The serious salt tides in May and September were also controlled by new measures, according to Huang.

Due to the salt tide, the fresh water supply in Zhuhai, Zhongshan, two cities in the province often threatened by seawater tide, and Panyu District of Guangzhou, will be affected.

Zhuhai government has advised people in the city to drink bottled water instead of tap water, which mainly comes from Xijiang River.

It has also stopped water supplies to gardening in public areas and communities, car washing and sauna bath businesses for a week.

In the urban centre of Guangzhou, however, the fresh water supply will not be affected since the city's water plant can offer sufficient supplies.

The seawater tide will not affect Shenzhen, another coastal city of the province, as the water level in the Dongjiang River, the city's water source, has remained high.

Editor: Yan