Environment Minister Xie Zhenhua told journalists on World Environment Day that "there is a strong probability that the water quality will worsen in the [Three Gorges] reservoir."
Sluice gates on the Three Gorges hydro-electric project on the Yangtze river were shut last Sunday.
The projected 463 kilometre-long reservoir has since been forming behind the dam and water levels are set to rise to 135 metres by 15 June.
Behind the dam, the city of Chongqing and its municipality - with a population of approximately 30 million people - is likely to pour around 940 million tons of industrial waste water and 245 million tons of domestic sewage within the coming year into the expanding reservoir, according to the US Inland Rivers Network.
Only 28 percent of industrial and eight percent of urban domestic waste water from the city is treated, according to China’s 2002 Environmental Report.
China is spending the equivalent of $2.4 billion dollars in an effort to cut pollution in the reservoir and is building a series of water treatment plants, Zhenhua said.
|Reservoir set to rise 135 metres|
in 10 days
"Sixty percent of the factories in the cities around the reservoir will have water treatment plants by the end of June, while 100 percent will have them by the end of 2003," Zhenhua said.
But the city of Chongqing, some 600 kilometres up-river from the dam, is not expected to have water treatment facilities in place until the end of 2004, he added.
When completed, the Three Gorges Dam will be the largest hydroelectric dam in the world.
It will stretch nearly a mile across and tower 180 metres above the world's third longest river.
The creation of the reservoir has displaced close to 1.9 million people. Construction began in 1994 and is scheduled to take 20 years at a cost of over $24 billion.
Other river concerns
According to China's 2002 Environmental Report, an annual assessment issued on Thursday, water quality at 41 percent of monitoring stations along all Chinese rivers did not meet the nation's lowest grade.
Twenty-five percent of the water on the Yangtze failed to reach standards, while nearly 50 percent of the water inspected on the Yellow River did not make the lowest grade, the report said.
"The water quality in the Yellow River has worsened this year as the water levels in the river have reached the lowest in 50 years," Wang Jirong, vice minister of environment said.