But what lies beneath the dam? Do these photos really show a submerged cemetery on which the dam was built?
Several Facebook posts making the same claim have been flagged as possibly false by the company’s fact-checking system. They generally share the same collection of photos, and variations on the claim that the dam was built on a cemetery.
Are these claims true? We investigated.
Graves exist, occasionally visible
The online branch of the Genealogical Society of South Africa, or eGSSA, keeps records of grave sites around the country, including those in the photos shared on Facebook.
GPS coordinates on the eGSSA website indicate that the graves are located on a roughly three-kilometre-long island in the Vaal Dam.
They are occasionally visible when the water level is low, like in this 2005 photo.
Photos collected by the eGSSA show that the graves include that of Jacobus Johannes Meyer, who lived between 1861 and 1893. The only other surviving grave is that of Jacobus Frederik Janse van Vuuren, who died in 1928, ten years before the dam was first completed.
However, the original dam wall was 9.15 metres shorter than it is today. The dam wall was raised in the 1950s and again in the 1980s and the dam’s capacity more than doubled.
So was the dam “built on a cemetery” or were the graves only submerged when the dam wall was raised?
Dams regularly submerge human settlements
Many Facebook users reacted to the posts of the graves with shock and concern. But while often controversial, it is not unusual for dams to flood occupied or previously occupied land.
An estimated 80 million people worldwide have been displaced by large dams, according to the Internal Displacement Monitoring Centre, part of the Norwegian Refugee Council but based in Geneva, Switzerland.
Photos show graves visible when water levels low
We were unable to locate the exact position and elevation of the graves, or to determine exactly when the photos were taken, which makes it difficult to determine when the graves were submerged.
Some of the flagged Facebook posts suggest that the photos “were taken in 2016 when the water level was extremely low”. But other posts imply the photos are more recent.
The dam was at only 26.3% capacity on 6 November 2016, just two days after the timestamp on most of the eGSSA photos. Photos posted on Facebook in early November 2020 would have been taken when the dam was at around 30% capacity.
The original operating capacity of the dam was roughly 38% of its 2020 full supply capacity. So it is possible that the waters of the original dam would have covered the graves.
We can be sure that the graves pictured in the Facebook post are submerged beneath the Vaal Dam, and they have been revealed by low water levels many times.
It is difficult to say for certain whether the graves were submerged by the original 1938 dam. But it is likely. – Keegan Leech
Editor's note: This article was updated to reflect the correct name of the Genealogical Society of South Africa, which had been misidentified as the Geological Society of South Africa. The error is regretted.
For publishers: what to do if your post is rated false
A fact-checker has rated your Facebook or Instagram post as “false”. What should you do? First, don't delete!
Click on our guide for the steps you should follow.
Africa Check teams up with Facebook
Africa Check is a partner in Facebook’s third-party fact-checking programme to help stop the spread of false information on social media.
The content we rate as “false” will be downgraded on Facebook and Instagram. This means fewer people will see it.
You can also help identify false information on Facebook. This guide explains how.