Several months of drought in the upper reaches of the Yangtze River, China's longest, had reduced its capacity to clean itself, Xinhua news agency quoted Cao Guangjing, vice manager of the Three Gorges Corporation, as saying.

Now as the water in the reservoir is set to rise to increase the hydro-electric potential of the dam, a lot of garbage on the banks will end up floating in its huge reservoir, he said.

"As the water in the reservoir is being raised 21 meters (70 feet) from 135 meters to 156 meters, the increase in floating debris in the reservoir is going to make clean up work much more difficult," Cao was quoted as saying.

The amount of floating garbage in the reservoir is expected to surpass 200,000 cubic meters (seven million cubic feet), Cao said.

To make matters worse, a specialized boat to clean up floating debris is inoperable due to a lack of spare parts, he added.

Environmental opponents of the dam have long said that such garbage, coupled with raw sewage from tens of millions of residents above the dam, will turn the Three Gorges reservoir into a huge cesspool.

The Chinese governmment says the controversial 25-billion-dollar dam will control chronic and sometimes deadly flooding of the Yangtze.

The government also argues it will help meet China's energy needs from a renewable source that will not add to greenhouse gases that drive global warming.

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