The two spills occurred during the past week along the Yellow River in northern China and on a tributary of the Yangtze River in southern China's Hunan Province.
The two incidents come a month after a benzene spill on the Songhua River forced the provincial capital of Harbin to shut off the water supply to its 3.8 million residents. That spill became an international scandal because officials in northeastern China initially tried to hide the problem.
The domestic news coverage of the spills suggests that the Songhua episode has created pressure on local governments to stop concealing such potentially dangerous accidents. But some experts also believe that the flurry of news coverage is merely revealing how common such accidents are.
"These things happen all the time, all over the place, probably on a weekly basis," said Elizabeth C. Economy, the author of "The River Runs Black," a recent book on China's environmental challenges.
Unquestionably, water pollution is an extreme problem in China. Government studies show that 70 percent of the country's lakes and waterways are polluted.
A vice minister for water resources has estimated that 360 million rural residents lack safe drinking water.
Water pollution has also been blamed for high cancer rates in villages along several Chinese waterways.
Local officials responding to the two new spills say that neither has forced shutdowns of municipal water systems. In Hunan Province, a spill occurred Jan. 4 in the industrial city of Zhuzhou after workers cleaning up a wastewater ditch mistakenly diverted the sewage water into the nearby Xiangjiang River.
The water was laced with cadmium, a metal used in manufacturing that has been linked to neurological disorders and cancer. Initial water quality tests showed that cadmium levels in the river were at least 25 times above the safety standard. Last month, a different cadmium spill on the Beijiang River in Guangdong Province threatened water supplies to millions of people and forced some temporary water supply shutdowns in the densely populated region.
In Hunan, Jiang Yimin, head of the provincial environmental protection bureau, said officials had used neutralizing chemicals to dilute the toxicity. He said the 60-mile slick had already flowed past the provincial capital, Changsha, without contaminating the drinking supply.
The city draws its drinking water from the Xiangjiang, and Mr. Jiang said that tests had initially showed that cadmium levels at city intake pipes were five times above the national safety standard. But he said the water was treated at municipal water quality plants so that it would be safe for public consumption.
Mr. Jiang said the toxicity of the river water now met quality standards. He also denied a report in China Youth Daily, a Beijing-based newspaper, which accused Hunan officials of intentionally playing down the levels of contamination to prevent a public panic.
"All of the downstream cities have met the water quality standard," Mr. Jiang said in a telephone interview.
A second major accident occurred last Friday, when a spill in Henan Province created a slick of diesel fuel flowing down the Yellow River. By the time the slick had reached neighboring Shandong Province, state news media reported that officials had shut down 63 pumping stations that draw drinking water from the river along the river, including in the provincial capital, Jinan. Officials in Jinan said the city would instead depend on water from reservoirs.
Meanwhile, a smaller spill was reported last Friday in central China along the Qijiang River, when a sulfur leak forced communities along the river to go without running water for two days.
This week, the central government announced plans to spend an additional $3 billion to clean up the Songhua River. Last Sunday, the State Council, China's cabinet, announced a new national emergency response plan, partly because of the Songhua controversy. The plan requires that natural disasters, major accidents and other incidents threatening public health should be reported to the State Council within four hours. The plan also requires that the public should be given timely and accurate information through the Chinese news media.
Ms. Economy applauded the idea of a faster, more public response, but said it did not represent a solution to the country's water pollution problem. She noted that factories commonly dump wastewater into rivers and that environmental officials lack the political power to stop it.
Indeed, the Xiangjiang River suffered such serious pollution problems even before last week's spill that local legislative delegates had complained that normal discharges of cadmium had long exceeded national standards.
Ms. Economy noted that a 2004 government study found that half of the sewage treatment facilities built under the last five-year economic plan were not being used because local officials considered operating them too expensive.