China's 98,000 Dams Have a Hidden Problem
October 11, 2026 · 23 min
China has more than 98,000 reservoirs, nearly 40% of the large dams on Earth. Its modern megadams are among the best-engineered structures in the world. This story is about something quieter: the tens of thousands of old, small earthen dams that sit above ordinary towns and farmland.
The core argument is that the weakness is not new and not mainly about weather. It was built into the soil more than half a century ago, and the clock on it is running out.
The night Banqiao failed
On 8 August 1975, in Henan province, workers piled sandbags on the Banqiao Dam while a record storm filled the lake behind it. The dam was designed for a once-in-a-thousand-years flood, but a planned spillway had been cut back during construction to save steel and money, and the sluice gates jammed with sediment. Water topped the crest, cut a breach 118 metres wide, and set off a chain of failures that took down 62 dams.
Where the dams came from
- In 1949 China had roughly 20 large and medium reservoirs. By the end of the 1970s it had over 80,000.
- About 80 to 90% of all dams are earth-fill embankments, and more than 80% were built between the 1950s and late 1970s.
- Many were designed, surveyed and built at the same time by local crews, using whatever soil was nearby rather than tested clay.
How an earth dam fails
Unlike concrete, an earth dam can fail from the inside out. Water finds a path through poorly compacted soil and carries fine grains away. The channel widens into a pipe, a process called internal erosion or piping. The surface can look perfectly normal until the crest sags and the reservoir pours over it.
A countdown, and an official list
- An earth embankment is typically designed for about 50 years before major overhauls. Dams from the 1950s to 1970s are at or past that point now.
- China’s own Ministry of Water Resources keeps a category for “sick and dangerous” reservoirs. Early 2000s surveys put more than 30,000 small and medium reservoirs in it.
- Between 2006 and 2020 the government spent tens of billions of yuan on grouting, spillway widening and monitoring. In 2021 officials said new sick reservoirs were still appearing faster than repairs.
- About 94,000 of the 98,000 reservoirs are small, often run by poor local governments with no staff or budget. Some were leased to fish farmers who blocked spillways to keep water high.
Silt and modern storms
Rivers like the Yellow River carry heavy sediment, and it settles in reservoirs. A dam built to hold 50 million cubic metres may now hold 20 million, so it overtops faster in a storm. In July 2021 Henan saw another once-in-a-thousand-years rainstorm. The Yihetan Dam developed a 20-metre breach, and in Inner Mongolia the Yong’an and Xinfa dams collapsed from overtopping after residents had been evacuated.
The fair picture
The video is clear that the Three Gorges, Xiluodu and Xiangjiaba dams are heavily instrumented and unlikely to fail. The risk lies with the small, ageing earthen dams. Repairing them is slow, and decommissioning is hard too, because old sediment can release sludge downstream.
Key takeaways
- Most of China’s 98,000 dams are old earth-fill embankments built quickly between the 1950s and 1970s.
- Earth dams can fail internally with little visible warning.
- Banqiao in 1975 killed 26,000 people officially, and independent estimates run far higher once famine and disease are counted.
- Thousands of reservoirs have been classed as sick, and repairs are racing ageing, silting dams.
- The modern megadams and the legacy small dams are two very different stories.
More from the channel: @ChinaUnderStress