A decade after China began filling the world's largest dam -- The Three Gorges -- concerns about the project's environmental and human cost endure even as the country prepares a huge hydropower expansion.

More than 1.2 million people were displaced as the waters in the monumental dam, which started accumulating 10 years ago on Saturday, submerged scores of towns and communities, and thousands of poorly compensated migrants remain mired in poverty.

But China's growing thirst for energy means that the Three Gorges -- which generates roughly as much electricity as a dozen commercial nuclear reactors -- is a model for 50 large dams to be built in the country, according to its current five-year plan.

Those barrages will crank out more than the current hydropower capacity of the US, putting China -- already the world's largest hydropower consumer -- on the way to providing 15 percent of its energy from renewable sources by 2020.

China's state-run media has praised the Three Gorges dam for generating over 88.2 terawatt hours (TWh) of electricity last year -- more than France's entire yearly renewable energy output, and exceeding the project's original goal.

The barrier's huge reservoir has also been hailed for lessening floods which have for millennia plagued the mighty Yangtze river as it cuts through central China, claiming thousands of lives as recently as 1998.

As flood waters upstream from the dam reached a peak last year, television images showed thundering torrents of water spraying from the structure -- as it held the bulk of the deluge in its huge reservoir.

But the dam has also been blamed for amplifying changes in weather patterns which in 2011 produced the Yangtze's largest drought in half a century, while heavy rains have continued to flood cities downstream, killing hundreds.

As dam officials sacrificed energy generation to release water to combat the drought, China's State Council, or cabinet, made a rare admission that the Three Gorges faced "urgent problems", including the relocation of migrants and ecological damage.

One migrant whose home was submerged by the dam said he refused to accept government compensation money, claiming it was too low and that land assigned to migrants had been sold by local officials to build a shopping mall.

"The land they compensated us with was scattered in the areas across the city that no one else wants. We can't run a business there. Of course we can't sign the agreement," Luo Xianwen, 69, told AFP.

The much-touted powers of the dam to boost shipping on the Yangtze -- turning it into a superhighway for large tankers which would for the first time be able to reach the inland megacity of Chongqing -- have proved limited.

Ships can wait for up to a week before being allowed to pass through the dam's choked locks, which can in itself take seven hours, shifting freight to newly built roads and railways nearby, reports say.

Fish stocks in the Yangtze have declined rapidly since the dam was built and fecal substances that can cause death have been detected in the reservoir, scientists have found -- while mountains of trash have accumulated in the water.

But despite the problems, the Three Gorges will be joined by a wave of new hydropower projects over the next decade -- mostly spread across China's mountainous and earthquake prone southwest.

The Xiluodu dam, the largest in the world in terms of the amount of water that it can release at any given time, is scheduled to begin producing electricity in June.

China's environment ministry approved the Shuangjingkou dam in a Tibetan area of southwestern Sichuan province earlier this month, the world's tallest at 314 metres high.

Most controversially, at least five major dams will be built on the Nu river -- which flows into Myanmar and Thailand, where it is known as the Salween -- despite concerns about their impact on unique flora and fauna in a region abutting the Himalayas.

Environmentalists fought a fierce battle against early proposals for a dam on the river, winning a rare government climbdown by then Premier Wen Jiabao in 2004.

The rapid expansion in hydropower has prompted fears among China's neighbours, with India's Prime Minister Manmohan Singh raising concerns in March over Beijing's plans to construct three dams across the Brahmaputra river, which rises in Tibet and runs for hundreds of kilometres through the region.

The ambitious plans have left some in China's growing environmental movement feeling powerless.

"We continue to oppose the hydropower plans... they will create all the same problems with migration and the environment," said Dai Qing, who spent time in prison for her opposition to the Three Gorges dam.

"Industry and local governments support these hydropower projects, because they'll profit from them," she added. "And they will be built no matter what local people say."