The sheer scale of the Tibetan Plateau can be hard to fathom. Its mountain peaks stretch kilometres into the sky, while canyons below sink so deep that few people have ever been able to reach them.
It's wild and spectacular but it's also vitally important to about a fifth of the world's population that relies on its immense freshwater reserves.
The ice sheet stretching across the plateau is so vast that it's often referred to by glaciologists as the Third Pole behind Antarctica and the Arctic. After the north and south poles, this region is the world's largest store of fresh water.
The plateau's glaciers feed 10 of Asia's major rivers. For centuries, they have played a crucial role in sustaining life in the region.
In recent decades, the rivers have provided more than just fresh water — they've become a vital source of energy for the world's most populous country. Since the 1950s, more than 20,000 dams higher than 15 metres have been built in the country, including the world's largest hydropower station, the Three Gorges Dam on the Yangtze River.
Hydroelectricity is China's second-biggest source of energy, after coal. It makes up almost a fifth of the total energy production— and its dam building shows no signs of easing.
As China seeks to meet its targets of becoming carbon neutral by 2060, it is turning its sights to some of the wildest reaches of the Tibetan Plateau, where it plans to build a hydropower plant so ambitious that it could produce three times as much power as Three Gorges.
Late last year, as the world grappled with the COVID pandemic, the Chinese Government announced it would seek to exploit the hydropower potential of the lower reaches of the Yarlung Tsangpo — a transboundary river that flows from Tibet into India, where itbecomes the Brahmaputra, and then into Bangladesh as the Jamuna.
The announcement was made as part of the government's 14th five-year plan, a series of guidelines spelling out China's economic and social priorities.
Experts believe it could be the riskiest mega structure ever built. Not only is the location prone to massive landslides and some of the most powerful earthquakes ever recorded, it's also precariously close to the disputed border between India and China. Meaning any major project could further escalate discontent in a tense territorial dispute between the world's two most populous countries.
It's here, in the western reaches of Tibet,where a waterway so wild and powerful that adventurers have called it the Mount Everest of riversbegins its course.
The Yarlung Tsangpo runs almost 3,000 kilometres through the plateau to the Indian states of Arunachal Pradesh and Assam, and then out into the Bay of Bengal via Bangladesh.
It's the highest major river on Earth, running at an average elevation of 4,000 metres, and until recently was one of China's last major free-flowing rivers.
In the last decade, China has sought to harness the river's power, and several hydropower stations have begun appearing, or are being planned,along its course.
But all of those projects pale in comparison to what it has planned here, at the most remote stretch of the river, known as the Great Bend.
As the river snakes its way through the remote eastern reaches of the Himalayas, near the disputed border with the Indian state of Arunachal Pradesh, it performs a dramatic U-turn.
The change of course in the river is so dramatic, that until the early-20th-century Western geographers and explorers were not sure if the Yarlung Tsangpo and the Brahmaputra were even the same river.
Another point that confused efforts to map the region was the dramatic difference in elevation between the two rivers. The Brahmaputra sat thousands of metres below the Yarlung Tsangpo.
Western explorers, who were forbidden from entering Tibet at the time, speculated that the rivers could be connected by an enormous waterfall. The lure of discovering what could potentially be the biggest waterfall on Earth inspired a series of audacious expeditions into the Himalayas.
In his book A Mountain in Tibet, Charles Allen documented a late-19th-century attempt to secretly trek into the remote regions of Tibet and send 500 logs, specially marked with metal rods, downstream to see if they could be spotted where the river entered India.
The plan failed, but information from the mission proved instrumental in the discovery, decades later, that the two rivers were in fact connected.
Instead of the one giant waterfall that some had envisioned, explorers found an enormous canyon forged through two of the Himalayas highest mountains, Namcha Barwa (7,782m) and Gyalha Peri (7,294m).
Chinese scientists who surveyed the region on foot in the late 1990s would later claim the Yarlung Tsangpo Grand Canyon was not only the world's longest canyon at more than 500 kilometres but also the deepest with a depth of more than 5,300 metres. That's almost three times as deep as the Grand Canyon in the US.
The team also identified this area as one of the greatest untapped hydropower resources on the planet.
That's because of the huge drop in elevation of the river over such a short period of time.
From one side of the Great Bend to the other there's a drop in elevation of more than 2,000 metres.
Since this discovery, China has toyed with the idea of building what would be the world's most powerful hydropower stations.
Details are extremely limited, but one proposal for the site is called the Motuo Hydropower Station, which experts believe could entail boring an enormous water diversion tunnel through Namcha Barwa.
The idea would be to send water plummeting through the tunnel and onto turbines on the other side of the bend below generating huge amounts of energy.
"It's nuts. It's completely nuts," said Dr Ruth Gamble, a historian at LaTrobe University and expert in this region.
Chinese media reported the head of Powerchina, the company believed to be spearheading the project, as saying the canyon had the potential to generate more than 60 gigawatts of power — that's three times the output of the Three Gorges dam.
While the designs for the project are yet to be released, China experts like Professor Mark Wang from the University of Melbourne, believe the fact that the project was referenced in Beijing's five-year plan means it will go ahead in some form.
"If they list something, even if it's impossible, that will get done. I'm 120 per cent sure of that," he said.
'The world's riskiest project'
The complexities and risk of building the world's most powerful hydropower facility in arguably the wildest stretch of river on Earth are almost incalculable.
The remoteness of the location means there is little infrastructure in place already to handle such a large-scale operation. Until 2013, the county was not connected to a major road that was accessible all year round.
The infrastructure required to transport such huge amounts of energy does not yet exist.
These projects alone are mammoth tasks. Add to that the geological volatility of the area, and it's enough to make some experts question whether the project is anything more than a pipe dream.
"This is the world's most riskiest project. It's technically the most difficult to build, ever, and it's the most expensive project ever undertaken on any river anywhere in the world. So in that context, I have always seen announcements like this with a bit of scepticism," said Himanshu Thakkar, a water expert from the South AsiaNetwork on Dams, Rivers and People.
What makes the project so risky is that the Great Bend sits atop what's known as the Indo-Tsangpo Suture Zone. A seismically active region of the Himalayas where the tectonic plates of India and Eurasia meet.
The epicentre of one of the biggest earthquakes ever recorded, a magnitude-8.6 quake in 1950, was 200 kilometres away in Assam state in north-eastern India.
Any project at the Great Bend site would need to reckon with the possibility of powerful quakes occurring.
The region is also prone to major landslides, which can have disastrous impacts along the river.
In March, just upstream from the Great Bend site, a hanging glacier high in the mountains broke free, sending ice and rock plummeting almost 4 kilometres down to the river below. Satellite imagery captured the Yarlung Tsangpo swelling upstream in the aftermath, after the landslide partially dammed the river.
A remarkably similar landslide earlier this year in India's Uttarakhand state in the Himalayastemporarily dammed the Rishi Ganga river. When it broke, a torrent of water was sent flooding downstream, killing scores of people and wiping out two hydropower plants.
The likelihood of landslides along the Yarlung Tsangpo would only increase, Himanshu Thakkar says, as a result of major land clearing that would be required to construct this mega-project.
"So the disaster potential in the downstream area goes up many fold," he said.
Despite the geological challenges facing the project, professor Mark Wang believes that Beijing has the technology to complete the project. He said he would not be surprised if it was done in the next few years.
But he believes the biggest challenge facing the project is not technical but political.
This region sits along a poorly defined borderknown as the Line of Actual Control, stretching from Pakistan to the west down to this region in eastern Tibet.
It includes large pockets of territory claimed by India and occupied by China, and vice versa.
Since the early 1960s, there has been a series of wars and confrontations in disputed territory.
In June 2020, a skirmish broke out in the Galwan Valley to the north that resulted in the first combat-related death between the two countries since 1975.
The idea of a mega-dam just kilometres from the Line of Actual Control between China and India's Arunachal Pradesh has for years caused angst downstream.
The fear in India is that China is trying to weaponise water by cutting off or diverting the water of the Yarlung Tsangpo.
Shortly after announcing its plans for the Yarlung Tsangpo, Indian media reported that its government was exploring a 10-gigawatt hydropower dam and reservoir as a way of counteracting the impacts of the Chinese project.
"The need of the hour is to have a big dam in Arunachal Pradesh to mitigate the adverse impact of the Chinese dam projects," a senior Indian government official told Reuters.
China has always said it has no plans to divert water, but this has done little to allay concerns in India.
Professor Wang said the lack of transparency surrounding the project had not helped.
"I don't think Chinese people will think of that as a weapon, but for India, obviously, or a downstream country, that's a big concern," he said.
So why is China pursuing such a risky and costly project?
For its part, China says the project is a key part of its efforts to hit peak carbon emissions by 2035 and to become carbon neutral by 2060.
To do that, the country will need to wean itself off its reliance on coal. Currently, more than 60 per cent of China's energy comes from its emissions-intensive coal-fired power stations, and it is still building more.
In 2020, China approved almost 37 gigawatts of new coal power, bringing the total amount of coal power either in planning or development to almost 250 gigawatts.
Reports suggest the potential energy out of the Motuo project could be somewhere between 40 to 60 gigawatts. While that would barely scratch the surface of what's required to reach carbon neutrality, Dr Gamble says the project is a good example of how the Chinese government plans to tackle its green energy targets: through its love of engineering solutions.
"The way that they started talking about it, in the Chinese press, reminded me of the way that they're talking about going to the Moon," she said.
"There is this thing about this being a technological challenge. 'We're up for it. We've done all the work. Here's how we're going to do it'."
The 'enormous consequences' of dams
Regardless of the motives for the project, those monitoring the impact of China's dams, say it will have a huge impact on the lives of those who live downstream.
One of the biggest impacts hydropower dams have on a river's ecology is that they trap sediment that would otherwise travel downstream.
"This has really enormous consequences," said Maureen Harris, director of programs with International Rivers, an advocacy group for the protection of rivers.
"These dams have disrupted fish species, flows of water, contributed to issues such as riverbank erosion, and loss of agricultural productivity and other issues community livelihoods downstream."
For many, China signalling that it was looking to tackle climate change was a huge step forward for the world's largest emitter of carbon dioxide.
But there is concern about its approach to reining in its emissions. Groups like International Riversbelieve dams are not the answer and that China should be looking to other forms of renewable energy.
"So I think we need to ask, 'At what cost?' 'What would be destroyed in the process?'. I think this is not the only route that can or should be explored to carbon neutrality," Ms Harris said.
Credits:
Reporting, mapping andresearch: Mark Doman
Development and mapping: Katia Shatoba
Design: Alex Palmer
Notes about this story
Digital elevation data for base maps and 3D model were sourced from the USGS/NASA's Global Multi-resolution Terrain Elevation Data 2010.
Earthquake data for the Himalayan region was sourced from the USGS Earthquake Catalogue. The data show quakes above magnitude 4.5 since 1900.
Country borders and disputed territories were sourced and mapped using the Natural Earth countries and disputed areas datasets.
Dam data was visualised using a combination ofthe open-sourceGlobal GeoreferencedDatabase of Dams and theGlobal Reservoir and Dam Database.
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