BEIJING, June 1 (Reuters) - Chinese officials promised swift steps on Friday to clean up a lake after an algae outbreak choked off water to an eastern city amid a rising public outcry about the nation's sullied water sources.

Taihu Lake in Jiangsu province has been struck by a rapidly spreading canopy of blue-green algae that has left water supplies for nearby Wuxi putrid and undrinkable. Convoys of trucks have been taking bottled water to aid residents.

Jiangsu was seeding clouds in an effort to bring rain to flush out the lake, the Chinese government Web site (www.gov.cn) reported. It had also launched efforts to draw more water from the Yangtze River into the lake, the country's third largest.

But the Communist Party chief of Jiangsu, Li Yuanchao, acknowledged that the scare exposed deeper failings.

"In future development we must be determined to make stronger efforts to clean up Taihu Lake and ensure its water quality and safety," Li said, according to a report posted by the State Environmental Protection Administration (www.sepa.gov.cn).

Li said small chemical plants around the lake must be closed and more waste water plants must be built.

A Wuxi city official, Zhu Zhongxian, said water drawn from the lake was becoming cleaner, a Jiangsu newspaper reported. He denied an Internet-spread rumour that Wuxi was preparing to blow up walls separating the lake from the Yangtze.

But residents and media said the emergency steps merely exposed a long-term failure to protect lakes and rivers, tainted by pollution and strained by population and economic growth.

In 2005, millions of residents of Harbin in northeast China had their taps turned off for weeks after a toxic spill in the Songhua River.

"CRISIS POINT"

"We've got a lot of complaints," one Wuxi resident, an engineer surnamed Xiang, told Reuters by phone.

"The impact on our life has been very big. The government should be monitoring beforehand. Don't wait until something explodes and it's too late until you deal with it."

One commentator said the problem was a symptom of widespread environmental destruction threatening many vital water sources.

"Along with our country's rapid economic growth there's been a constant build-up of pollution and checks on it have lagged," said the commentary on the Web site of the People's Daily, the Communist Party's newspaper (www.people.com.cn).

"Our country's environmental protection has reached a crisis point, and we must adopt extraordinary measures to contain the spread of environmental pollution."

China planned to provide safe drinking water for all by 2015, the China Daily citied Minister of Water Resources Chen Lei as saying. About 300 million people in the country of over 1.3 billion still did not have access to clean water, another official told the paper.

But many of China's lakes and rivers are threatened by run-off from fertilisers, dumped industrial waste and untreated sewage. Algae blooms can burst out in water rich in nutrients from farm and domestic run-off.

Wuxi is a thriving industrial centre with an urban population of more than 2.3 million.

Residents voiced frustration, but not outright panic.

"I haven't washed for days. We can only rub down, and use bottled water for food, drink and washing," said Wang Chunye, a mining company worker.

"The government has not taken the environment seriously enough. The whole effort is still not very effective. This has happened before, but it was especially bad this year."

AlertNet news is provided by