China's population officially hit 1.3 billion in January.

"In 2030, the population will reach 1.6 billion and there will be 1,760 cubic metres of water resources per person," Qiu Baoxing, vice minister of construction, was quoted as saying by the official People's Daily.

That represents nearly 400 cubic metres less per person than in 2004.

China had 21 percent of the global population and only 7 percent of the world's total water resources, Qiu said. Measured against its economy, China consumed five times more water than the global average.

Over-exploration of groundwater, heavy pollution and widespread waste are taking a heavy toll on the country's limited liquid assets.

Domestic industries and residents discharged 200 billion tonnes of untreated waste water into rivers every year and 90 percent of rivers that passed through Chinese cities were polluted, Qiu said.

Exacerbating the problem was the uneven distribution of water in China, particularly in the drought-prone north.

The region was home to one third of the country's people but only 6 percent of its water, Qiu said, noting per-capita water reserves in the northern city of Tianjin were one-ten thousandth of those in mountainous Tibet.

China has launched an ambitious South-North water diversion scheme, but pollution and failure by regional governments to improve waste treatment were ruining available supplies, an official said on UN World Water Day in March.

Nearly 45 billion cubic metres of water from the Yellow, Yangtze and other rivers will be sent north every year when the project is finished in 2050, at an estimated total cost of almost 500 billion yuan ($60.42 billion), twice that of the Three Gorges Dam, the world's biggest hydroelectric project.