Mega dams meant to control siltation will add to ecological woe, experts warn

China is paying a heavy price for underestimating silt accumulation in the Three Gorges reservoir with plans to build more mega dams upstream of the Yangtze River, which themselves will have serious ecological impact, mainland experts have warned.

Siltation has long been a cause for concern for critics of the gigantic hydropower project even before it was built. But the government has sought to play it down, along with other environmental and geological concerns over the years, in a bid to defend the politically charged project.

'Authorities used to dodge questions over siltation and insisted that it posed no threats to the Three Gorges,' said Fan Xiao , a geologist in Sichuan . 'But now siltation at the dam reservoir has been cited as a main reason to build a succession of big dams on the upper reaches of the Yangtze and its tributaries, such as Jinsha and Dadu rivers.'

Twelve hydroelectricity dams have been designed on the middle and lower reaches of the Jinsha, while 22 dams are planned on the mainstream of the Dadu River. They are part of at least 106 dams planned or already built on the mainstream of six tributaries of Yangtze's upper reaches, including 38 large dams with a capacity over 1,000MW, according to Professor Fan.

The other four tributaries are the Yalong, Min, Jialing and Wu rivers.

'The silt problems at the Three Gorges reservoir have fuelled the much-criticised dam-building frenzy in the southwestern region,' he said.