In May, Chinese environmental officials warned that Beijing in 2008 would face a water shortage of up to 1.1 billion cubic metres if current trends prevail.

Beijing would need an extra 5.75 million cubic metres of water to supply an estimated 2.5 million Olympic visitors, the Beijing News said.

Beijing is currently suffering its worst drought in 50 years. From 1999 to 2005, rainfall was down 25 percent on average levels, a Beijing water authority spokesman said on Thursday.

State media said last year that vast stretches of the Yellow River, which supplies water to 12 percent of China's 1.3 billion people and 15 percent of its farmland, were so polluted it was unsafe for drinking or swimming.

China's longest river, the Yangtze, was "cancerous" with pollution, state media said in May.

Beijing authorities are also under pressure to protect the capital's "Green Olympics" from sandstorms and enduring poor air quality.