Quick Answer: China’s Medog Hydropower Station, under construction on the Yarlung Tsangpo River in Tibet, will be the biggest dam project the world has ever seen. At an estimated cost of roughly 1.2 trillion yuan (US$137–170 billion) and a generating capacity of 60 gigawatts — three times the Three Gorges Dam — it’s not so much a dam as a network of five cascade stations feeding four 20-kilometre tunnels bored straight through a Himalayan mountain. Commercial operation is planned for 2033.
A Number That Doesn’t Really Fit in Your Head
On 19 July 2025, Chinese Premier Li Qiang travelled to the remote Tibetan city of Nyingchi and declared construction officially underway on what he called a “project of the century.” For most of us sitting in Australia, the Medog Hydropower Station is an abstraction — a headline about a dam in a place we’ll never see, on a river most people can’t name. But the numbers are worth slowing down for, because they reframe what’s physically possible with an earth-moving project.
Most of what we build at Big Ditch is at the other end of the scale — farm dams, stock dams, irrigation storages, the odd council job. But the principles that make a small earth dam work are the same ones engineers are wrestling with at Medog. Water, gravity, geology, and the limits of what human beings can reasonably build. The Medog project is just those principles pushed to the absolute edge.
Where Is It, and Why There?
The dam is being built in Medog County, in the southeast corner of Tibet, near the border with India’s Arunachal Pradesh. The Yarlung Tsangpo River flows across the Tibetan Plateau, then makes a dramatic U-turn around the sacred Mount Namcha Barwa — the so-called “Great Bend” — before plunging south into India, where it becomes the Brahmaputra, and then into Bangladesh as the Jamuna.
What makes this location irresistible to hydro engineers is simple: in just 50 kilometres, the river drops about 2,000 metres. That’s a vertical fall roughly the height of eight Sydney Towers stacked end to end, over a run shorter than the distance from Sydney to the Blue Mountains. The energy potential locked up in that drop is estimated at seven times that of the Three Gorges Dam.
It’s Not One Dam — It’s Five, Plus Four Tunnels
The popular image of a mega-dam is a single vast concrete wall, like Hoover or Three Gorges. Medog is not that. The terrain simply will not allow a giant reservoir — the canyons are too narrow, the geology too seismic, and the environmental stakes too high.
Instead, engineers are using a “run-of-the-river” design. A cascade of five smaller hydropower stations will divert a portion of the river’s flow into four tunnels, each roughly 20 kilometres long, bored directly through Namcha Barwa mountain. The diverted water plunges down the tunnels under enormous pressure, spins turbines at the bottom of the canyon, and is returned to the river before it crosses into India. No vast reservoir. No 180-metre dam wall. Just tunnels, turbines, and the mountain itself doing the work.
Why Tunnels Instead of a Wall?
Two reasons. First, the region sits on the Indus-Yarlung Suture Zone — the collision line where the Indian tectonic plate is ramming underneath the Eurasian plate. It’s one of the most earthquake-prone places on earth. A traditional reservoir dam would be a catastrophic liability if it failed. Second, a giant reservoir behind a wall would flood vast areas of irreplaceable Tibetan canyon ecosystem and displace an enormous human population. Tunnels let you harvest the drop without the storage.
The tunnels themselves are being built with tunnel boring machines (TBMs) — the same technology used to dig rail and road tunnels under cities, scaled up and toughened to handle granite, heat, and earthquake risk up to magnitude 8.5.
How Medog Compares to the World’s Other Mega Dams
| Project | Country | Installed Capacity | Estimated Cost | Status |
|---|---|---|---|---|
| Medog Hydropower Station | China (Tibet) | 60 GW (up to 81 GW) | US$137–170 billion | Under construction — operational 2033 |
| Three Gorges Dam | China | 22.5 GW | ~US$32 billion (2009) | Operational since 2012 |
| Itaipu Dam | Brazil / Paraguay | 14 GW | ~US$19 billion | Operational since 1984 |
| Grand Coulee Dam | USA | 6.8 GW | ~US$1.2 billion (1940s) | Operational since 1942 |
| Snowy 2.0 (pumped hydro) | Australia | 2.0 GW | ~A$12 billion | Under construction |
At 60 GW, Medog will generate roughly three times the power of Three Gorges and thirty times the capacity of Australia’s Snowy 2.0 project. Its estimated annual output of 300 billion kilowatt-hours is enough electricity to power the entire United Kingdom, or supply about 20 per cent of China’s residential consumption.
The Numbers Behind the Cost
Published figures put the price tag between 1 and 1.2 trillion yuan — roughly US$137 to US$170 billion, depending on exchange rate and which Chinese source you believe. That is more than four times the real-terms cost of Three Gorges, and makes Medog one of the most expensive infrastructure projects in human history.
Put another way: at A$250 billion-plus, a single hydro project will cost more than Australia’s entire annual federal health budget.
What It Means for the Rest of Us
Medog sits a long way from the rural dams we design and build. But three things about this project are worth noting if you care about water infrastructure at any scale.
- Downstream matters more than people admit. India and Bangladesh both depend on the Brahmaputra. Even though China says the run-of-the-river design won’t reduce flows, downstream nations have requested environmental impact assessments that have not yet been publicly released. The principle applies on any scale: when you change how water moves through a landscape, you change it for everyone downstream. It’s just as true on a 100-hectare property as it is on the Brahmaputra.
- Geology always gets a vote. The reason Medog is a tunnel project and not a wall-and-reservoir project is that the geology simply won’t allow the latter. On a farm dam, the same logic applies — the wrong site will beat the best design every time. That’s why a proper site assessment always comes before a dig day.
- Run-of-the-river is a design worth understanding. Diverting water through a controlled path and returning it to the river, rather than holding it back behind a wall, is a model with applications well beyond mega-projects. For landowners with creek or spring resources, it’s a concept worth exploring.
Will It Actually Happen on Schedule?
Construction commenced in July 2025, with commercial operation planned for 2033. That’s an eight-year build for the largest and most technically demanding hydropower project ever attempted. For context, Three Gorges took 17 years from start of construction to full commissioning. Snowy 2.0 has already slipped several years behind schedule and almost tripled in cost.
Nobody should be surprised if Medog runs long or over-budget — every mega-dam in history has. The real questions are whether the environmental and downstream consequences can be managed, and whether the seismic risk in the tunnels can be engineered around. China’s state construction arm, PowerChina, has plenty of experience with big tunnels and big dams. But nothing this big, in a place this dangerous, has ever been attempted.
Key Takeaways
- Medog will be the largest hydropower project ever built — 60 GW, three times the Three Gorges Dam
- Estimated cost is US$137–170 billion, making it one of the most expensive infrastructure projects in history
- It’s a cascade of five stations and four 20 km tunnels, not a single wall-and-reservoir dam
- The design takes advantage of a 2,000 metre river drop over a 50 km stretch of the Yarlung Tsangpo
- Construction started July 2025, with commercial operation targeted for 2033
- Downstream impacts on India and Bangladesh remain a serious diplomatic concern
Frequently Asked Questions
Where exactly is the Medog dam being built?
On the Yarlung Tsangpo River in Medog County, in the southeast of the Tibet Autonomous Region, near the Indian border state of Arunachal Pradesh. The key feature is the “Great Bend,” where the river drops about 2,000 metres over 50 kilometres around Mount Namcha Barwa.
How much will Medog dam cost?
Published figures range from 1 to 1.2 trillion yuan, roughly US$137 billion to US$170 billion. That makes it more than four times the real-terms cost of the Three Gorges Dam and one of the most expensive infrastructure projects ever built.
How does Medog compare to the Three Gorges Dam?
Three Gorges has an installed capacity of 22.5 GW and produces about 90 billion kWh per year. Medog is designed for 60 GW and 300 billion kWh per year — nearly three times the output. Unlike Three Gorges, Medog does not create a large reservoir; it uses tunnels and turbines to harness the river’s natural drop.
Will the Medog dam affect water supply to India and Bangladesh?
China says the run-of-the-river design means water is diverted through tunnels and returned to the Yarlung Tsangpo before it crosses into India as the Brahmaputra. In theory this means downstream flow is not reduced. In practice, India and Bangladesh have requested comprehensive environmental impact, climate, and disaster assessments that China has not yet publicly released.
When will Medog start generating electricity?
Commercial operation is planned for 2033, eight years after the official construction start in July 2025. Given the scale and the remote, earthquake-prone terrain, schedule slippage would be unsurprising.
Thinking about a dam on a scale that’s actually useful to you? Book a site inspection with Big Ditch — we’ll tell you what’s possible on your land, for a fraction of 1.2 trillion yuan.