20 July 2021
Hulunbuir: a very serious double dam failure in China on 18 July 2021
There has been surprisingly little international reporting of a very serious double earthen dam failure in the Hulunbuir area of Inner Mongolia in northern China on Sunday 18 July 2021. This looks to have been one of the most serious dam failure events in recent years, with 46 million cubic metres of water having been released, causing massive flooding. Reuters has a report of the event, but there are few other outlets providing much attention to it.
The dams in question are called Yong’an Dam and Xinfa Dam, located in Morin Dawa Daur. There is dramatic footage of the collapse of the Xinfa Dam on Youtube (apologies for the awful music):-
This dam is located at 48.609, 124.241. This is a Google Earth image in happier times:-
Note that this dam has a substantial spillway structure, so overtopping is surprising. However, the video of the collapse shows that a very substantial volume of water had already overtopped the structure:-
A good working hypothesis is therefore that this dam was affected by the collapse of the Yong’an Reservoir, which would have released a catastrophic volume of water. About 10 km upstream of the Xinfa Dam there is another dam, located at 48.675, 124.327. The Google Earth image below shows the comparative position of these two structures. Interestingly the adjacent town is called Yongfu:-
One of the videos of the dam collapses, posted to twitter, appears to show the failure of a structure that is definitely not the Xinfa Dam:-
内蒙古 呼伦贝尔市 莫旗自治州 境内二座水库 新发及永安水库决堤
2021年7月18日 一部曲 pic.twitter.com/at4FEGw9qF
— 白七 (@tw_tomy_) July 19, 2021
This is a still from this video:-
I’m reasonable confident that this is the dam located upstream of the Xinfa Dam – the configuration looks to be identical. Edit: indeed this is now the confirmed location of the Yong’an Dam – see comments below:-
Thus, my hypothesis (untested at the moment) is that the Yong’an Dam failed due to the intense rainfall, which released a huge wave of water that overtopped and failed the Xinfa Dam, releasing a far greater volume to inundate the surrounding area.
There are images and videos online showing very extensive and damaging flooding from this event, such as this:-
A report on Apollo News details the damage (I have edited lightly to improve the English):
“16,660 people were affected; 325,622 mu [21,775 hectares] of farmland was flooded; 22 bridges, 124 culverts, and 15.6 kilometres of highway were destroyed….Casualties are unknown.”
Given the sale of the disaster it would be surprising if there were no human casualties although the Reuters report claims that there were no casualties. In the past such reports from China have not been reliable, so the jury is still out.
Large-scale dam collapses such as this are rare but very serious. Interestingly, the Reuters reports includes the following:
China has more than 98,000 reservoirs used to regulate floods, generate power and facilitate shipping. More than 80% of them are four decades old or older, and some pose a safety risk, the government has acknowledged.
Given the rate of change of intense rainfall events, this must be of great concern.