How China Is Building the Impossible $167B Mega-Dam that Controls India's Water Supply

[00:00:03]The deepest canyon on Earth, a river dropping 2,000 m in 50 km.

[00:00:10]Right here, China is building a dam that produces triple the power of three [music] gorges. Three gorges, 22 gaw.

[00:00:19]Medig, 60. Nothing like it has ever been built.

[00:00:23]>> This isn't just the world's biggest dam.

[00:00:25]It's being built in the world's most extreme place to build anything.

[00:00:32]$167 billion. Construction started July 2025. Target 2033.

[00:00:40]But downstream, India is watching. 300 million people drink from this river.

[00:00:48]This river becomes the Brahmautra in India. Then the Jamuna in Bangladesh.

[00:00:53]China controls the source. Power China broke ground July 19th, 2025 in one of the most inaccessible places on Earth.

[00:01:05]Four tunnels, 20 km each, board straight through a Himalayan mountain starting now.

[00:01:13]This is how China builds the world's most powerful dam. Step by step, starting from nothing.

[00:01:23]Without a road, nothing reaches this site. The Pyen Medog Highway opened 2022.

[00:01:30]Construction's only artery. 40 million tons of cement, millions of tons of steel, all arriving by this road. No other way in. New access spurs blasted from the canyon walls. Every construction platform needs its own road.

[00:01:47]>> We drill the face first, check the rock, then the charges go in. We've done 12 km of new road in 4 months.

[00:01:55]>> Rock bolts drilled into every cut face.

[00:01:58]The Himalayas's earthquake constantly.

[00:02:00]Nothing is left unsecured. Side canyon crossings bridged as the access network grows. Six new bridges just to reach the first dam site. The deepest canyon positions unreachable by road. Even now, supplied by heavy lift helicopter.

[00:02:17]>> We use helicopters for the gear that can't wait for the road extension.

[00:02:21]Precision parts, emergency equipment.

[00:02:25]The canyon doesn't care about your schedule.

[00:02:27]>> A cable car system installed across the main canyon. Workers cross the gorge in 8 minutes. The alternative is 3 hours by road. The logistics network alone costs billions. Before a single dam wall rises, the site has to be reachable.

[00:02:44]Site power wired in along the highway route. The machines need electricity before they can build the dam that makes it. Everything you're about to see built started here. A road, then a power line, then a camp, then the machines arrived.

[00:03:00]>> The road network is live. Now the river has to move. The Yalaong Sanangpo runs at 14,000 cub m/s in monsoon. It has to be moved.

[00:03:15]First, blast a channel through the canyon wall. The river gets a temporary new path while the dam is built in its bed.

[00:03:22]>> This rock is 200 million years old.

[00:03:25]Cambrian granite. The explosives don't care. We've got 30 m to clear in 6 weeks.

[00:03:33]>> The blast.

[00:03:35]A canyon wall gone in 4 seconds. The diversion channel begins. Excavators clear the blast debris. Dump trucks carry it out. The diversion channel takes shape in the canyon wall. The upstream coffer dam rises across the river. Rockfill first, then the clay core seals it against leakage.

[00:03:55]>> This coffer dam costs hundreds of millions to build and gets demolished when the main dam is done. It's a tool, a one-use tool for moving the most powerful river in Asia.

[00:04:05]>> The river finds the channel. The original bed slows. For the first time in geological history, the Yalong Sanpo changes course. Workers take the riverbed. The ground where the dam wall will stand dry for the first time.

[00:04:22]>> Standing on the river bottom. Never thought I'd say that in the Yalong Tangpo. The rock here is clean. Better than we expected.

[00:04:30]>> Every loose fragment cleaned from the foundation rock. The dam sits on this surface. Nothing weak stays. Foundation cores drilled and logged. Every meter of rock described before the concrete starts. Grout curtain injected under the foundation. Fractures in Himalayan granite sealed with cement. No water path under the dam. Five cascade sites.

[00:04:54]All working simultaneously. The canyon transformed into the world's largest construction site. Four tunnels 20 km each board straight through this mountain. Namcha 7,700 m of granite above. The TBM assembly begins. 14 m in diameter, the largest tunnel boring machine ever deployed in Asia.

[00:05:19]>> This machine weighs 4,000 tons. We shipped it in 300 pieces from the factory. Assembly alone took 4 months.

[00:05:27]And now we are ready.

[00:05:29]>> 240 disc cutters on the face. Each one made from tungsten carbide. At full speed, the mountain has no answer to this machine. First rotation, the machine bites into Namcha.

[00:05:42]20 km to go >> inside the tunnel. It's loud, hot, and the mountain is pressing from every direction. Workers live in this for 12-hour shifts. 20 km ahead is daylight.

[00:05:58]>> Pre-cast concrete segments lined behind the TBM as it advances. Rings of concrete. The tunnel supports itself as it grows.

[00:06:07]>> Every ring is nine segments plus a key.

[00:06:10]We place one ring every 40 minutes when it's running smooth. The machine never stops if we're doing our job right.

[00:06:17]>> 50,000 cubic meters of Himalayan granite removed per tunnel. The mountain becomes the fill for the access roads outside.

[00:06:25]Four machines boring simultaneously.

[00:06:28]Four crews working 24 hours. The mountain is being hollowed from four directions. At kilometer 8 groundwater, Himalayan rock is fractured. The water finds every crack the TBM opens.

[00:06:42]>> We inject cement grout under 50 bar pressure into that fracture. Give it 48 hours. If it holds, we bore through. If not, we grout again.

[00:06:51]>> Steel pentock pipe installed through the concrete lined tunnel. This is where the water will travel at 60 m/s.

[00:06:58]Seismic sensors every 100 m inside every tunnel. The Himalayas move. The sensors know before anyone else does. 20 km, four years of boring and the machine breaks through. The tunnel is done.

[00:07:13]Three more to go.

[00:07:15]>> The tunnel exit portal formed in concrete. Water will enter at the intake. Travel 20 km underground exit here at the powerhouse. Intake gates fitted at the river end of every tunnel.

[00:07:28]These steel gates control the water entering the pentock.

[00:07:32]>> People ask how long it takes to bore 20 km through the Himalaya. The answer is exactly as long 51 months.

[00:07:40]>> The mountain has been rooted. The river is ready. Now the five cascade dams rise. Cascade one, the highest point.

[00:07:50]The river drops most steeply here. The first dam catches the full energy of the great bend. A dedicated concrete batching plant for each cascade. Mixed at the rim, delivered to the base.

[00:08:02]Continuous pour. No stopping. Roller compacted concrete. No forms for the main dam body. We place the mix in layers with dump trucks and compact each one with vibratory rollers. Faster than conventional pores. Roller compacted concrete placed in [music] 300 mm layers. Compacted immediately. The next layer poured before the previous one fully sets. Cooling pipes run through the dam body continuously. Himalayan temperatures are extreme.

[00:08:30]Layer by layer. The wall rises. Each band is one day's work. You can read the construction history in the dam face.

[00:08:38]>> Standing at the canyon walls are vertical on both sides. The dam wall rising in front and the bedrock under my boots is the foundation China will never see again.

[00:08:47]>> 5 km downstream. Cascade 2 rising simultaneously.

[00:08:52]Five operations, one timeline.

[00:08:55]Everything must finish together. The spillway gates go in alongside the main wall. These are the emergency release valves built for the worst monsoon the Himalayas ever produce.

[00:09:06]>> Each gate weighs 900 tons. One crane pick. If the gate doesn't seat correctly in the first lift, you don't get a second chance in this canyon.

[00:09:15]>> Nightpore at Cascade 3. The cold Himalayan night helps. Lower ambient temperature means less cooling load on the concrete. Every RCC layer core sampled for density and strength. A rejection means the layer is demolished and recast.

[00:09:32]Cascade one wall complete. The reservoir fills behind it. The water that once raced through this canyon now slows.

[00:09:39]Held. Cascade four and five walls topped [music] out. The five dam cascade is structurally complete. The river's 2,000 m drop captured. Five dams 50 km. The Yaong Sanangpo has five new masters.

[00:10:00]The coffer dams demolished when each main wall is sealed. Billions of dollars of temporary structure bulldozed into the reservoir. Pentocks fitted through every dam wall. Water enters the intake, falls through the pentock, hits the turbines at the bottom. The powerhouses built at the base of each cascade. The water falls. The turbines sit at the bottom. One powerhouse per cascade. 12 turbine units each. 60 turbines total across all five [music] stations.

[00:10:32]Turbine pits poured inside the powerhouse. Each pit [music] 12 m diameter for a single turbine rated at 1,000 megawatt. The spiral casing guides the water onto the turbine runner. Water spirals [music] inward. The runner spins. The generator above turns. This casing alone weighs 300 tons. We cast it in Shanghai. We ship it by rail to Lassa. then road freight the last 500 km into the canyon. 18 weeks total journey.

[00:11:00]>> Wicket gates fitted inside the spiral casing. These gates throttle the water flow to control turbine output. Runner alignment checked to hundreds of a millimeter. A misaligned runner destroys itself in hours at operating speed. The draft tube below the runner. Water exits here. Slowed down. Energy spent.

[00:11:21]Returning to the river downstream.

[00:11:24]Five powerhouses, all under construction. The canyon is running on three shifts around the clock.

[00:11:32]>> Three shifts, 800 workers per site. We rotate every 8 hours. When the mountain decides to move, we pause. When it settles, we go again.

[00:11:42]>> Tailra tunnels carry the spent water back to the river. The energy is gone.

[00:11:47]The water continues to India.

[00:11:49]The water that came from the Tibetan glaciers fell 2,000 ft through these turbines generated electricity for them [music] exits here.

[00:11:57]>> Switch gear rooms fitted alongside every generator. These are the buildings where 12,000 megawatt per [music] station gets switched. Stepup transformers outside the powerhouse. Generator voltage stepped up to 800 kovts for long-d distanceance transmission. Cascade 3 complete. Water enters the intake at the top. falls 60 m through the pentock, turns the turbines, returns to the river at the bottom. Five cascades complete.

[00:12:27]The river that once ran free through the world's deepest canyon now powers a country. The turbines for Medogined in Harbin, the largest Frances turbines ever made. Each runner alone weighs 280 tons. Each runner shipped by heavy rail from Harbin to Lassa, then road freight into [music] the canyon, 3 months per unit. The runner goes in by overhead crane. 60 turbines total, each one a precision lift into a pit that took months to build. The generator stator goes in above the turbine. [music] The rotor will spin inside it. Magnetic field, current induced, electricity, stator winding connections [music] made by specialist crews. The resistance of every connection measured before the generator housing closes around it.

[00:13:16]>> 12 generators in one hall. Each one a,000 megawatt. 12,000 under this one roof. Three. Gorgeous dam produces 22.

[00:13:24]This is one station of five.

[00:13:26]>> Unit by [music] unit. The stations come online. Cascade 1, then two, then three, then four, then five. A centralized control room monitors all five stations simultaneously.

[00:13:40]One operator can manage 60 turbines from one desk. Gas insulated switch gear installed at every station. 800 kovolt switchyards are too dangerous to build outdoors in a Himalayan canyon. 800 kovolt transmission towers going up from the canyon rim. The electricity leaves Tibet heading for eastern China. 60 gaw ready to leave the canyon. The transmission lines are the last piece.

[00:14:06]4,000 km of ultraigh voltage line. The electricity arrives in eastern China in milliseconds. Converter stations in Sichuan and Eunan. DC power converted back to AC. The electricity enters the national grid here. India monitors every change in river flow. External affairs minister Jishanka raised it [music] directly at the SEO meeting in July 2025.

[00:14:32]30 million people in Assam alone depend on this river. 300 million across India and Bangladesh.

[00:14:40]>> The water goes back into the river right here. Same volume that went in at the intake. We're not consuming it. We're borrowing the drop. The river continues downstream.

[00:14:50]>> The border is invisible from the air.

[00:14:52]The river doesn't know it. China controls the dam. India controls the monitoring. Neither controls the river.

[00:15:00]25 km from where I'm standing, India begins. The same canyon, a different country with no say over what was just built upstream of it.

[00:15:09]>> The most powerful hydropower complex ever built on a river shared by three countries with treaties covering none of it. Bangladesh is at the end of the same system. The river becomes the Jamuna here. Whatever happens upstream arrives here last. The river continues. It always has. The question now is who decides when it does and how much. Five dams, four tunnels, 60 turbines, 167 billion.

[00:15:41]Started July 2025.

[00:15:44]Road, river, tunnels, walls, turbines, [music] power. 8 years of construction in this canyon. One turbine, 1,000 megawatt. 60 of these running simultaneously. By 2033, three gorges, 22.5 gaw, med 60. Nothing in human history generates more electricity from a single river. The downstream flow continues for now. Every megawatt generated upstream is a river management decision. For 300 million people who weren't in the room, the power lights 300 million Chinese homes.

[00:16:24]Clean power, no coal, no carbon from water and gravity and the deepest canyon on Earth. The mountain stands. The tunnels are inside it now. The river still runs around its base, but nothing here is as it was before July 2025.

[00:16:42]>> This construction is not finished yet, but we brought the plan to life. So, you can see what China is trying to build.

[00:16:52]Medog is still under construction, but if this plan succeeds, the Yaalong Sanangpo will never look the same again.