The flooding, the worst for many years, has caused devastation across a wide swathe of heavily populated and productive areas along the Yangtse with huge economic losses.

Deluge has caused severe economic damage

Around 3,000 people have been killed and millions left homeless.

Some 21 million hectares of farm land have been inundated, with economic losses estimated at $20bn.

But the director-general of China's State Environment Protection Agency, Madame Liu Xiuru, admitted the weather had only been a superficial factor.

An official investigation in Beijing has concluded the real cause of flooding was damage to the environment along the river banks.

Mme Liu said the floods had been a profound lesson for the country.

She was speaking at an international conference on the development of Central Asia which opened on Monday in Urumqi, western China.

The admission comes as China steps up its battle against illegal logging.

Deforestation robs the land of its ability to absorb and retain rainwater and channels it into riverbeds.

It also leads to soil erosion which causes the riverbeds to rise.

Forestry administration chief Li Changjian has said illegal logging is ''rampant'' with around 440,000 hectares of forest stripped every year.

Water worth more than gold

Millions have been left homeless

Environmental disasters under discussion at the international conference will include one of the century's worst - the drying up of the Aral Sea.

Other problems include over-grazing, soil degradation and a legacy of polluting industries and nuclear testing.

A representative from the Altay republic of Russia told the conference that Central Asia was feeling the force of the Altay proverb that water was worth more than gold.