BEIJING: For China, global warming has become something of a convenient truth.

Beijing blames climate change for wreaking havoc on scarce water resources, but critics say the country's headlong drive to build its industrial prowess and huge hydro projects are just as responsible.

On the eve of a global climate change conference in Stockholm, a U.N. climate body says shrinking glaciers in central Asia and the Himalayas would affect water resources in downstream river catchments, which include China.

"Some regions are already near the critical temperature threshold," the Intergovernmental Panel on Climate Change (IPCC) said in a draft summary report obtained by Reuters.

"In parts of Asia, increases in flood and drought will exacerbate rural poverty, due to negative impacts on rice crops and increases in food prices and costs of living."

Rising temperatures are likely to speed icecap melting in the Himalayas, which could bring first floods and then severe drought, with diminished seasonal melts unable to replenish China's rivers, including the mighty Yangtze.

This year, China published a national "water census" showing that as many as 28,000 rivers logged in a government database had vanished since the 1990s, leaving just under 23,000.

The census gave no reason for the disappearance, but China's weather bureau said several major rivers, including the Yellow River, a massive northern waterway linking nine provinces, had been dwindling since 1970 and the trend was likely to continue.

"We have witnessed major fluctuations in precipitation in different parts of China," said Ma Jun, a water expert and director of the Institute of Public and Environmental Affairs (IPE), which monitors China's rivers.

"One thing in the mind of policymakers and researchers is that climate change will add to uncertainties -- in some areas, the water supply situation is already quite tense."

But rising temperatures are only part of China's problems, many of which have resulted from overpopulation, aggressive industrialisation and a huge reliance on elaborate engineering schemes to irrigate crops and harness scarce supplies.

"China's water shortages stem more from problematic urbanisation and water resource management, rather than the scapegoat of climate change," said Zhou Lei, a fellow at Nanjing University who studies how industry affects the environment.

"In my home town in Jiangxi, the water system consisted of underground springs, ponds, wetlands, brooks, streams, and seasonal rivulets, but all these have been totally ruined in the last 20 years due to a catastrophic urbanisation plan, a construction mania and transport megaprojects," he said.

Wringing China dry

China has vowed to spend trillions of yuan to boost supplies, clean rivers and protect water tables.

But even if supplies remain steady, water resources per person, now at 2,100 cubic metres or 28 percent of the global average, are expected to decline further as the population grows.

At the same time, Beijing still needs to feed its growing food, energy and industrial demand.