As authorities push ahead with an ambitious hydroelectric construction boom, the threat of a disastrous dam collapse looms over more than 179 Chinese cities, amid increasingly unpredictable global weather patterns, local media have reported.
China is home to more than 40,000 "at risk" reservoirs, which, along with flood defenses beside major rivers, were built between 1950 and 1980, the online news site Easynet said in a recent article.
Most are of rock and clay construction, and are reaching the end of their intended lifespan of 50 years, causing major headaches for the government, it said.
Xue Shikui, a water resources management expert at Florida University, said reservoirs, like any other man-made structure, have a limited lifespan.
"When they get old, they should be decommissioned or rebuilt," he said, adding that China built huge numbers of reservoirs and dams from the 1950s to the 1970s. "Otherwise, the natural aging process is unavoidable."
He said decommissioning a dam in itself is a major project.
"If you demolish it, that costs money, and if you don't demolish it by blowing it up, you have to use other methods, such as allowing the river flow gradually to become more natural," Xue said.
China's State Council has lifted a ban on major dam projects in the southwest imposed by then premier Wen Jiabao in 2004, and earmarked around 62 billion yuan (U.S. $10.1 billion) to repair the 40,000 "at risk."
But the central government has yet to deliver all of the promised funding, and local governments are seen as unlikely to make up the shortfall.
Aging dams
The number of dams in mainland China rose from around 20 at the founding of the People's Republic in 1949 to more than 86,000 today. This figure doesn't take into account more than 10 million small-to-medium size water-holding structures like dikes and irrigation canals, official statistics show.
According to Wu Yegang, a water resources expert at Connor Environmental Services in the United States, China's aging dams could face a "perfect storm" of factors in the years to come.
"You have the construction methods used in the 1950s, which are primarily clay, and on top of that you have contemporary climate change, along with numerous thunderstorms," Wu said.
"There have also been [geological] changes in the valleys holding the reservoirs, so it will become extremely dangerous," he said.
China, which has been hit by extreme flooding in a number of provinces in the wake of two major tropical storms this summer, is no stranger to failed dams and collapsed dikes.
From 2007 to 2011, China's reservoir dams were collapsing at the rate of around 68 a year, a rate that has now slowed to 20 in the past two years, the Easynet article said.
In 1975, the catastrophic collapse of the Banqiao dam at Zhumadian in central Henan province caused the deaths of an estimated 171,000 people, according to international experts.
The majority of those deaths were among people who survived the initial tsunami and were stranded with no food or medical assistance, eventually succumbing to starvation or disease in huge numbers, water resources expert Eric Fish wrote in China's Economic Observer website in February.
"When the Banqiao reservoir had emptied and the waters had settled on the morning after the collapse, the horror was only beginning," Fish's article said.
"Survivors were left to wait on rooftops or huddled together on small patches of dry land ... Disease spread quickly while people battled hunger and the summer heat."
'Domino effect'
The Chinese government's ability to manage the country's water resources has been bound up with political power and credibility since the early emperors.
The Banqiao dam was built after then supreme leader Mao Zedong called on officials to "harness the Huai River" in order to generate electricity and a reliable water supply, leading to a cascade of dams being constructed in the basin which were hit by a once-in-2,000 year rainfall.
But environmental group Probe International has warned that a similar strategy is being used again today in southwestern China.
"If one dam fails, the full force of its ensuing tsunami will be transmitted to the next dam downstream, and so on, potentially creating a deadly domino effect of collapsing dams," the group said in a recent report.
"A cascade of catastrophic dam failures would almost certainly cause an unprecedented number of casualties and deaths in major downstream population centers, such as Chengdu, and along these major river valleys."
Incalculable environmental damage could also result from the flooding of chemical plants that cluster along Chinese rivers, officials have warned.
Reported by Shi Shan for RFA's Mandarin Service. Translated and written in English by Luisetta Mudie.