A salt tide has hit Shanghai, but has not disrupted the water supply for the city's 17 million people, according to the local hydrology monitoring authority.

The salt tide arrived at the mouth of the Yangtze River around 8:00 PM Monday when chloride in the water reached 270 miligrams per liter, 20 mg higher than the normal level, said Chen Guoguang, director of Shanghai Monitoring Station under the National Water Quality Monitoring Network.

The salt tide, the seventh since September last year, is likely to last another two or three days, said Chen.

The tide would have little impact on the water supply as sufficient water has been stored in the city's reservoirs, said Sheng Daisun, director of the Yangtze River Raw Water Plant.

The plant had also increased the number of pumps to ensure a safe water supply during a major salt tide, added Sheng.

An exceptional drought last year led to low water level in the upper reaches of the Yangtze River, causing salt tides to occur two months earlier than in previous years.

The worst salt tide in Shanghai started on Oct. 9 last year when chloride was almost five times higher than normal. The tide lasted nine days and affected water supplies in a few districts.

The salt tide usually occurs at the mouth of the Yangtze River from November to April, when water reserves decrease and seawater flows in.

(Xinhua News Agency January 10, 2007)