Environment

Too big to fail

Operator of Three Gorges Dam rebuffs online rumours about safety

Three-Gorges-Dam-w

China’s mega-dam in Hubei

Apoor quality image or evidence that the world largest hydroelectric dam is structurally unsound? That’s what Chinese netizens were asking earlier this month after photos from Google Earth appeared to show that the outer wall of the Three Gorges Dam had buckled.

Previous satellite images had shown the two-kilometre long concrete wall to be straight and without kinks. But a close-up of the barrier taken from Google’s eye-in-the-sky service hinted that the concrete structure had warped under the pressure of 40 square kilometres of water behind it.

The photographic discovery – which went viral on Chinese social media – was said to have been made by “Japanese geologist Hayashi”, although Japan’s media outlets such as Asahi Shimbun said the photos appeared to have originated from Twitter users.

Yet the fact that it became an instant trending news item in China underlines the shaky confidence in the huge infrastructure project.

The dam has always attracted a degree of suspicion because its approval was rammed through despite many dissenting voices. When the National People’s Congress was asked to rubber stamp the project in 1992, only 67% of the 2,633 lawmakers voted in favour, the lowest approval rate ever in China’s parliamentary body.

In 2011, five years after the primary structure was completed, China’s State Council under then Premier Wen Jiabao admitted that the dam had in fact contributed to environmental damage such as landslides, downstream water shortages and greater risk of seismic activity due to the weight of the water.

But in this particular case it seems the alarm was unfounded. The distortion – as seen on the Google images – was most likely a technical glitch, a consequence of the fact that all satellite photos are composite images glued together. If the images aren’t aligned, a straight-lined object can look as if certain chunks of it have shifted.

It is also possible that people online were further doctoring the images to create alarm. Indeed, as one expert speaking to ThePaper.cn pointed out “if the distortions shown in the photos were real, the dam would have collapsed already”.

The Three Gorges Corporation also put out a statement saying the dam “was second to none in terms of integrity”.

Displacement is “normal” for dams – which have to have some elasticity – but thousands of pieces of monitoring equipment had only detected vertical and horizontal shifts of between 0.2mm and 2.6cm, the state-owned firm said.

China’s Aerospace Science and Technology Corp also stepped in to help clear up the confusion by publishing a satellite image of the dam showing it to be straight.

The Global Times accused “foreign forces” of starting the rumours “to intentionally tarnish the project and the Chinese government”.

Yet at the same time there is a question to be asked about the impact of big dams in the era of climate change. Over 370 Chinese rivers flooded this year according to the Ministry of Water Resources, 80% more than average. In total some 20 million Chinese have been affected or displaced by this year’s heavy rains. The deluge has also caused $7.7 billion in damage, Xinhua said. Yet at the same time China is home to 98,000 dams designed to prevent catastrophes like floods.

Some environmental experts say dams – especially large ones – will cause more problems as the weather becomes more erratic. They can deprive people of water downstream during dry periods but may then have to release large amounts of water in cases of heavy rain. Furthermore reservoirs have been found to produce huge amounts of the greenhouse gas methane as algae and other organic matter rots in the stilled water.

Perhaps this month’s headlines about the Three Gorges Dam will turn out to be yet another instance of ‘fake news’, but debates about the broader consequences of the giant structure will likely continue.


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