NANJING, June 19 (Xinhua) -- Every evening Li Fang sits in front of the television to watch the weather forecast, and frowns when the temperature is projected to top 30 degrees Celsius.

    "The blue-green algae reproduces faster when the temperature rises," says Li, 58, who was born and grew up by Taihu Lake, drinking its water. "As a child I used to see algae in the lake, but it was not as bad as it is now. The water smells fishy every summer these days."

    She cannot understand why the pollution is still such a problem. "I had to retire three years early when the chemical plant I worked in was shut down last year for discharging too many pollutants into the lake."

    However, a severe algae outbreak at the end of May still left tap water undrinkable for a week for half of the 2.3 million residents in her home city of Wuxi, in the eastern Jiangsu Province.

    Barely two weeks after the water returned normal, satellite pictures captured on June 15 indicated another algae bloom spanning 800 square kilometers in the central-western and northernparts of the lake, causing wide-spread concern in cities along the lake.

    About 30 million people rely on Taihu Lake, China's third largest fresh water lake, for drinking water, including nine cities in the provinces of Jiangsu and Zhejiang as well as Shanghai municipality.

    A Chinese Academy of Sciences (CAS) researcher says the algae is likely to threaten water safety in almost every city along the lake. "Algae will keep growing in the lake until the end of August," says Qin Boqiang, a CAS expert on geography and lake studies.

    An environment official admits the algae has posed more challenges to his organization this year. "Our conventional solutions don't work any more," says Gu Gang, vice director of the environment protection bureau in Wuxi. "One outbreak after another. It was never like this in the past."

    Gu says his bureau has been watching industrial waste discharges closely. "There're too many plants around the lake and together, they discharge too many pollutants."

    Jiangsu Province will have to close another 2,000 small chemical plants around the lake in the next two years, says Shi Zhenhua, director of the environment protection bureau.

    But Shi says industrial discharges are not the only cause of the pollution on Taihu Lake: farmers around the lake use an average 66.7 kg of fertilizer on every hectare of land, triple theupper limit in developed countries.

    His view is echoed by Zhang Lijun, vice director of the State Environmental Protection Administration, who says agricultural pollution is to blame for 40 percent of the phosphorus and nitrogen in the lake.

    High levels of nitrogen and phosphorus are believed to be major causes of algae blooms, which develop in water that is rich in nutrients, often because of run-off from heavy fertiliser use, industrial waste and untreated sewage -- all readily available in the developed east.

    Water pollution in the lake has also aroused the concern of the central government, which has demanded that no more nitrogen or phosphorus discharging industrial projects are to be approved along the lake.

    Environment experts say it is impossible to eradicate all the algae or pollutants anytime soon, and cities have begun to search for alternative drinking water sources.

    Wuxi is stepping up a new water supply project which, on its completion in a year, will give citizens access to Yangtze water in case the Taihu Lake is polluted again.

    Algae blooms were also detected in Chaohu Lake, China's fifth largest freshwater lake in Anhui Province that neighbors Jiangsu.

    Yet the environment watchdog in Anhui insisted on Monday that the lake water quality was "stable" and media reports had exaggerated the situation.

    Satellite pictures captured on Friday indicated 280 square kilometers of blue algae on Chaohu Lake.

    "Our figure is six square kilometers, largely in the western half of the lake," said Xiao Pu, an official with the environment protection bureau in the provincial capital, Hefei.

    But he said blue algae was always found in small quantities floating on the lake surface. "There's no sign of deterioration."

    The Chinese are becomingly increasingly aware of pollution and public opinions at times convinces governments to suspend highly polluting projects.

    Last month, Xiamen, a port city in east China's Fujian province,decided to put a highly polluting chemical project on hold amid fears of pollution.

    The city government suspended a 10.8-billion-yuan (1.4 billion U.S. dollars) paraxylene project that was expected to produce 800,000 tons of paraxylene and generate revenues of 80 billion yuan (10.45 billion U.S. dollars) a year. Its planned location 16 kilometers from the city center sparked pollution fears among the public.

    Paraxylene is a highly polluting, cancer-causing petrochemical. Health experts say it can cause fetus abnormalities.

    Amid nearby residents' worries over magnetic radiation pollution, the state environment watchdog has decided to reassess a planned magnetic levitation train line linking Shanghai and Hangzhou.

    Approved by the central government in March 2006, the 35-billion-yuan (4.5 billion U.S. dollars) maglev project using German technology would cover its 175 km at a maximum speed of 450km per hour.