The Yangtze, Asia's longest river and the water lifeline for millions of Chinese, appears to be drying up and climate change is to blame, a Chinese expert says.

Chen Xi Qing, a professor at Shanghai Normal University, has studied the Yangtze for more than 20 years but has never seen anything like the current situation, which he calls a potential environmental and economic disaster.

"In the Yangtze, it seems that it has become dry," he said. "Most of the population, most of the economy are located in the middle and lower Yangtze River."

Roughly 500 million people depend on the river, which flows from Tibet through seven Chinese provinces and sustains cities like Chongqing, Wuhan, Nanjing and Shanghai, where the river empties into the East China Sea.

Farming gobbles up 60 per cent of the available water, but Chen said this year's extraordinary dryness has another explanation: global warming.

Ships grounded

Water levels are so low that more than 10 ships that normally sail the 6,300-kilometre waterway have been grounded over the past two weeks, the Beijing News reported.

The situation is particularly dire near the city of Chongqing in central China, where its 30 million inhabitants have started limiting water supplies and are drilling wells to tap from reservoirs.

Pumping capacity at Shapingba Waterworks — one of the largest suppliers of drinking water — has plummeted in the industrial city and only one of 10 pipes used to pump water from the Yangtze was still in operation, the Xinhua News Agency reported.

The lack of rainfall and fast flows of fresh water also means pollution is fouling up the Yangtze more than usual.

"If the water levels in Yangtze and its upper tributary Jialing River continue to decline, we'll face a real crisis," Xinhua quoted an unnamed Shaping water bureau spokesman as saying.

The drought is expected to continue until the rainy season begins in May, Xinhua said.

With files from the Associated Press