China's earthquake, one month on

Torrents of muddy water gushing from a "quake lake" in southwest China have contaminated water sources for 600,000 people living downstream, state media reported Thursday.

At least two towns along the Fujiang River have had to switch to alternative water supplies since the controlled release of water from Tangjiashan lake began on Saturday, the Xinhua news agency reported.

Tangjiashan lake was created when landslides blocked a river in southwest China's mountainous Sichuan province during the May 12 earthquake.

The runoff raised the level of the Fujiang river by two metres (6.6 feet) in Tongliang county, where residents are now relying on reservoirs instead of the river for water, local government spokesman Zhao Wuqiang was quoted as saying.

The local water plant was no longer able to purify the river water for the town of 100,000 people, Zhao said.

The reservoirs, which the country capital has been relying on since Wednesday, contain enough water to last three months, the report said.

Waterworks in Mianyang, the major town on flatlands downstream of the river, were also suspended Tuesday after a local monitoring centre found the runoff had contaminated the water there, Xinhua said.

Mianyang's 500,000 people are now also drawing their water from underground reserves, Xinhua reported.

Authorities said the controlled operation to release the vast quantities of water from Tangjiashan, which involved the evacuation many days earlier of more than 250,000 people from the flood zone, had proceeded relatively smoothly.