Many were shocked when thousands of dead pigs were found floating on Shanghai's Huangpu River this month, but animal carcasses are not the only things that end up in the nation's waterways.
Rivers and lakes are among the major dumping sites of some 190 million tonnes of household waste generated in rural areas every year, most of which are casually dumped without being recycled or properly treated, according to a bill submitted to the annual session of the Chinese People's Political Consultative Conference in Beijing last week.
Research by the China Association for Promoting Democracy, one of the mainland's eight non-communist political parties, shows that most household refuse in the rural areas is piled on the side of roads, dumped under bridges, in fields or on river banks, or simply burned.
Researchers said the variety and amount of rural waste had risen markedly over the past decade as living standards improved.
In rural areas, household refuse used to comprise mainly of kitchen waste and ash from burning coal or firewood, but Wang Jinxia, a researcher at the Chinese Academy of Sciences' Centre for Chinese Agricultural Policy, said there was now more plastic packaging, sanitation products and even furniture in the thrown-away waste.
Wang said the limited amount of household waste, most of it biodegradable, could be absorbed by nature's self-cleaning capacity in the past, but now the amount and variety of trash had far exceeded that capacity, threatening the environment.
"It [dumping refuse in rivers] is a rather prevalent phenomenon … in some extreme cases, the rivers are even clogged," Wang said.
In the past month, photos have been posted online in a campaign to record polluted rivers, some completely covered by garbage. A stream in the Yongding county of Fujian province was used as a dump for waste including glass bottles, plastic bags, used lanterns and even furniture.
Last month, a Zhejiang businessman offered a 200,000 yuan (HK$247,000) reward to an environmental official in Ruian in challenging him to swim in a river full of household refuse and waste rubber from a shoe factory.
Every summer, 150,000 to 200,000 cubic metres of refuse is retrieved from the reservoir above the massive Three Gorges Dam to prevent it from jamming the floodgates, official media reports say. The waste include tree branches washed into the Yangtze by torrential rains, but most of it is household refuse from families living along the river's upper reaches. Some rivers in cities have also become casual dump sites. For example, The Beijing News reported this month that the authorities had retrieved more than 10,000 corncobs from the moat of the Forbidden City - among the four tonnes of refuse that tourists threw into the Tongzi River.
Some sections of the waterway in the old town of Lijiang , a popular city for tourism in Yunnan province, were also found to be congested with plastic bottles, disposable tableware and other refuse, China National Radio reported last year, while some restaurants were accused of discharging their wastewater - containing grease and detergent - directly into the river.
The mainland banned the dumping of household refuse and industrial waste in rivers, lakes, canals and reservoirs in 2004 when the Solid Wastes Pollution Prevention Law was amended.
But researcher Wang, who did a survey of about 120 villages in seven provinces in 2010, said there was no such government oversight in some regions.
The high cost of refuse collection and treatment had also discouraged some local governments from tackling the problem, Wang said. For instance, a town with 50,000 residents would need to spend at least 3.5 million yuan a year for proper waste disposal, Wang said.
"Without a public service to collect and cart away the trash, people in rural villages have no choice but to dump it in the waterways or fields," she said.