The worst of the Wuxi water crisis appears to be over, authorities said Friday night.

The tap water in Wuxi, rendered undrinkable earlier this week by foul-smelling blue-green algae blanketing the Taihu Lake, has improved "considerably" in quality, though it may take days for a full recovery.

Workers from the Wuxi tap water company collect blue-green algae in a water source area in Taihu Lake, in the eastern Chinese city of Wuxi, Jiangsu Province, Thursday, May 31, 2007. [Xinhua]

"Thanks to the concerted and strenuous efforts in the past few days, the water quality has improved considerably," Mao Xiaoping, mayor of Wuxi, said on Friday night.

An industrial city famed for centuries by its beauty in East China's Jiangsu Province, Wuxi is coping with its worst ever water crisis, after the rapidly-spreading algae heavily tainted its water source, Taihu Lake.

Looking like green oil paint, the canopy of algae covered at least 70 percent of the lake's surface.

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Continuous high temperatures and a lack of rainfall since this spring are mainly to blame for the blue-green algae outbreak, experts said.

The quality of the water, which became yellow-colored and putrid on May 28, had improved by Friday.

Methods used to flush away the bloom included diverting water from the Yangtze River, the nation's longest river, to dilute the lake water, seeding clouds to bring rain, in addition to improving water treatment techniques, Mao said.

The Ministry of Water Resources had requested the Taihu Lake Valley Administration to double the frequency of quality monitoring - to four times a day.

On Friday, Minister Chen Lei also urged the agency to work with local government to help reduce pollutants being piped into the lake.

Thirty-nine rockets containing silver iodide were fired at eight different sites surrounding Taihu Lake on Thursday afternoon and Friday morning.

The operation induced moderate rain for most areas around the lake and even heavy rain in some parts, a spokesman of the Jiangsu Provincial Meteorological Station said.

In addition to the artificially induced rain, the city is expected to have "remarkable rainfalls" in coming days, Zheng Guoguang, chief of the China Meteorological Administration, said.

"Both the precipitations will help improve the scenario," he told China Daily, adding Chinese meteorological satellites are also keeping a close eye on the alga bloom.

Residents in the city have relied on bottled water for consumption in the past few days.

The ample supplies of bottled water - some allocated from neighboring cities as well as Shanghai and Zhejiang Province - have helped quell public panic. But residents have been warned that they may need to keep drinking bottled water for some time.

"Although quality of the water supply has improved significantly on Friday and now it is safe for washing hands or clothes, it still takes some time to become drinkable," Zhang Xiaojian, a professor with Environmental Science and Engineering Department of the Beijing-based Tsinghua University, said.

It will take some time before the residuals of the tainted water in the pipelines are completely flushed out, said the professor, a specialist invited by the municipal government to help deal with the water supply crisis.

"It will be a long-term campaign to battle the algae crisis," he said.