from the Waters of the Yangtze river in China Rises the biggest concrete structure on the planet the Three Gorges Dam is over two kilometers long and 60 stories tall it has taken forty thousand workers over 17 years to build when it fully comes online this one Dam will produce over twenty thousand megawatts of power twice as much as all the nuclear power stations in Britain put together it is the Pinnacle of dam engineering [Music] gorgeous Dam owes its success to five Landmark dams at the heart of each lies a major technological innovation that allowed Engineers
to build ever bigger dams one by one traveling up the scale we'll reveal the incredible Stories Behind these structures [Music] and the inventions that allowed them to produce ever more power six ingenious leaps forward from Big to bigger into the world's biggest [Music] foreign [Music] economies on Earth all the need of its ever accelerating industry the nation needs more power foreign much of this will be provided by an enormous Dam spanning the mighty Yangtze River in central China called the Three Gorges Dam [Music] our cameras have been granted privileged access to capture this amazing feat
of Engineering in its full Glory foreign before they could start building the three gorgeous Dam the Chinese first had to divert the Yangtze River which is almost two kilometers wide and move over a million people from the area about to be flooded [Music] and when they filled the reservoir behind the dam a huge mass of water actually slowed down the speed of the Earth's rotation by a fraction well it's three gorgeous damn is the biggest hydroelectric project in the world stem used 28 million cubic meters of concrete maybe one way to look at it is
to say it's a solid pipe of concrete a meter diameter right around the world it's a lot of concrete Chinese authorities think it's worth the effort as the Three Gorges Dam will provide clean and cheap electric power to millions of people foreign [Music] to understand how the Three Gorges Dam can produce so much power we need to travel back in time to 19th century Britain and a modest stream in Northumberland the power behind the world's first hydroelectric Dam [Applause] [Music] in the 1800s when Britain was at the heart of the Industrial Revolution this house was
the last word in modern living it belonged to Lord Armstrong an entrepreneur and obsessive inventor he fitted his house with state-of-the-art technology including Central Heating and Mechanical Devices that drove elevators laundry machines and roasting spits but there was one place in the house where modern technology was sadly lacking as historian Anthony Burton explains [Music] this was Armstrong's real pride and joy the picture gallery full of wonderful Victorian paintings bit gloomy even in daylight but what he really wanted to do was to bring his guests here in the evening but by the flicker of Candlelight nothing
really worked what Armstrong needed were electric lights and a way to power them how do you generate electricity well that's something that was known for 50 years because Michael Faraday had given the secret you move a magnet in relation to a coil of wire with a little setup here so how it might work now here we are here we've got two magnets on the end of this disk and right here is a coil of wire now if I make this spin in relation to that we should make electricity and yes we're getting a reading on
the ammeter we are definitely making electricity every time the magnets on the disk move past the coil they generate a tiny electric pulse in the copper wire so make a lot of electricity you need much bigger kit and this is what Armstrong bought the Thompson Vortex turbine a grand piece of equipment the Thompson turbine needed a huge volume of fast-flowing water to drive the rotor all Lord Armstrong had available was a tiny stream trickling through his estate what he needed was voter out of a small stream he built a dam [Music] Armstrong built an earth
wall nearly 10 meters high which turned his stream into a deep lake its mass of water pushed down in in pressure at lower depths Armstrong channeled this high pressure water down through a pipe to the bottom of his Dam [Music] here he injected it into a Thompson turbine where the torrent spun the rotor this in turn rotated a shaft linked to a generator produced 4000 watts of electricity for Armstrong this was only the first step to enlightenment he then needed to get the electricity from the turbine house at the bottom of the dam all the
way to his picture gallery over a kilometer away Armstrong connected two strands of thick copper wire to the generator to carry the electricity up to his mansion [Music] all in all he used five tons of copper to power a single light bulb but he created a world first a house lit by the power of water [Music] on the other side of the planet in central China the three gorgeous Dam can light up two and a quarter billion light bulbs foreign [Music] the Three Gorges Dam is China's biggest construction project British engineer Robin charlwood has been
working on it since 2003 and is still impressed by its scale we're in one of the three very large powerhouses of the Three Gorges project in this 700 meter long rum here you can see 14 of the large turbine generators then beyond this one a kilometer away is the second Powerhouse and then beyond that one is yet another Powerhouse which will be underground in the Rock on the far side of the river each one of these generators cost about 50 million dollars give you an idea of the scale of this project [Music] debden Dam had
one generator Three Gorges has 32. together they produce 5 million times more power than debton to drive them the Chinese have harnessed the power of the mighty Yangtze River [Music] in the reservoir behind the dam the river now Rises up to 60 stories above the riverbed the water is channeled down gigantic concrete tubes towards the generators [Music] here the torrent of water hits the turbines and makes them spin this motion is in turn transferred to the rotor of the generator this is fitted with massive magnets which move past copper coils in the casing to generate
electricity just one of these machines makes as much electricity as a small nuclear power plant all 32 generators together produce enough power for 60 million Chinese this project is setting a new Benchmark in the international hydroelectric industry it's almost twice the size of the next largest project it's ipu in Brazil because it's only the first of a whole series of Mega dams that are under construction here in China back in 1878 debden Dam showed that even the smallest stream can be harnessed to produce electricity but to generate power on a larger scale Engineers had to
wrestle with bigger Rivers to build a dam that could produce 128 megawatts French Engineers had to persuade the Raging dordoin River to run a new course 1914 France the outbreak of the first world war plunged the country into a deep energy crisis with their coal Fields occupied by the Germans the French were forced to import coal from abroad to feed their power plants and keep the country going so after the war they decided to boost the nation's power supply with electricity from a hydroelectric Dam but building a concrete dam in the fast-flowing dordoing river presented
quite a challenge and this is our Mighty River door here on the beach now you can't just pour concrete into the middle of a river they wanted their Dam here but in order to get one Dam they had to build three first of all a temporary Dam goes in here what's called a coffer Dam that stops the river flowing you can't just stop it it's going to go over the top unless you do something different which is built a diversion channel right round there and then to stop it backing back up again you put in
a second Coffer Dam here and you've got a space in between which you can drain and it's there that you can build your main Dam foreign the engineers blasted two tunnels through the rock to carry the diverted River they dropped steel cages containing rocks into the river to make their temporary cofferda then they strengthened it with concrete now is the river behind the dam began to rise it could drain through the tunnels to stop this water from backing up the engineers built a second Coffer Dam once the water had drained from the riverbed between the
dams it left a perfect dry spot to build the main Dam [Music] fortunately for the engineer they discovered when they emptied the central part that actually the riverbed was Solid Rock they could build straight on top of it layer by layer the giant concrete structure Rose 30 stories up from the riverbank the engineers then closed the diversion tunnels and allowed the reservoir to fill up and submerge the cofferdams their job done finally they could open the gates to the turbines and start producing electricity when the Mirage dam was finished it produced 128 megawatts enough to
help power a train line to Olio and Supply the City of Paris 400 kilometers away with electricity [Music] the Yangtze River is over 6 000 kilometers long and in places several kilometers wide the biggest river in China [Music] it presents enormous logistical challenges to the dam engineers as the Yangtze Rises behind the Three Gorges Dam it will flood over a hundred and fifty thousand acres of land along its banks so the Chinese have to relocate over a million people from the land behind the dam thousands of new houses have to be built for the displaced
citizens to live in then the engineers can begin to damn the river [Music] the engineers Begin work on a series of stone Coffer dams to block off part of the axi whilst leaving a channel open for the rest of the river to flow through they build the first two sections of the main Dam on the dry Riverbank then they dump tons of Earth into the river and on top of it build another cofferdan this time from concrete [Music] with the river held in check behind it they can finally build the last section of the dam
then they must remove the Coffer Dam so that water can flow through the turbines of the main Dam [Music] having built such substantial confidence structures it's a major challenge how to remove these things so in the in the earlier stages where they were built of very large rocks like this then that could be handled with big excavator equipment relatively conventional but in the final stage where they had a solid concrete wall to remove this required some serious innovation unlike the coffee Dam in Mirage the Chinese version is too tall to Simply leave it in place
so the Chinese engineers build it leaving holes for explosive charges on the 6th of June 2006 they filled them with 190 tons of dynamite and hold their breath is tomorrow what has taken months to build takes only seconds to destroy cofferdam crumbles it unleashes the water stored behind it It's the final test for the three gorgeous Dam and it holds back in 1935 the marriage Dam proved that Engineers could divert rivers to build powerful dams but to break through the 1000 megawatt Mark American Engineers building the Hoover Dam had to take their building material to
the Limit [Music] foreign in the 1930s the USA decided to tackle one of their big economic problems cities in the Western United States couldn't grow because they lacked both Water and Power [Music] so to break the deadlock Engineers began work on the world's biggest dam it would contain more concrete than any other construction project before it foreign but as concrete sets a chemical reaction causes it to heat up this created a problem for the Hoover Dam's engineers if the concrete of the Hoover Dam was poured in one go the concrete on the outside would have
cooled and hardened first while in the core of the dam the concrete would have stayed hot and tried to expand this could stress the concrete and make it crack foreign so the engineers cast the concrete for the Hoover Dam in small individual blocks as the concrete in each block cooled it shrank but didn't crack the contraction left small gaps between the blocks which Engineers filled with cement [Music] but this clever design didn't solve all the problems it's enormous I mean there are six million tons of concrete in the Hoover Dam and if we were able
to concentrate all of the heat that's generated by that curing concrete into a single oven we could cook half a million loaves of bread every day for three years this structure if it was left on its own they figure out it's going to take 125 years for it to finish shrinking and cooling down basically and that's not nearly quick enough now the guy in charge is a fellow called Frank Crow and they call him hurry up Crow because he's a man in a rush and he says this is not good enough I can't weigh 125
years what I'm going to do is I'm going to use the Colorado River to cool my dam [Music] Crow embedded over 950 kilometers of steel water pipes into the concrete of the Hoover Dam he built a huge water chilling Factory [Music] here he called river water down to four degrees and then shot it through the pipes into the hot concrete yeah this shortened the cooling time from 125 years to only 22 months [Music] now this works a treat all I have to do is finish the dam cement grout up the pipes and they're out there
fantastic effort it actually took 5 000 men only 21 months to build this structure not only that they finished two years ahead of time and they finish ahead of budget Hoover Dam stored 35 billion cubic meters of water and at the time generated more power than any other dam in the world with this magnificent Dam behind them the cities in the American West could finally begin to thrive [Music] the three gorgeous Dam contains more concrete than any other structure on Earth you look at it you can just picture the thickness of the concrete at the
base of the dam the height of it 180 meters then it's two kilometers long so it's a colossal amount of concrete [Music] with this much concrete on their hands Chinese Engineers had to pull out all the stops to keep their Dam cool and they basically used everything in the book they cooled the Aggregates and the materials the Sands before they put it into the mix they added ice they did everything they could to get the temperature down as low as they could before it started to warm up all by itself and here because of the
issue of some of the summer weather being especially hot July and August they actually went so far as to use a fog spray system to blow effectively a fog blanket over the top of the dam with the objective of blocking the solar radiation from piling down into the concrete and adding to the heat that was being generated on the inside with all the cooling measures in place the Chinese Engineers don't have to worry about cracks in their Dam [Music] 36 the Hoover Dam proved that Engineers could build impossibly big concrete dams but as dams grew
they held back ever more water and with it tremendous destructive power to build the Grand Coulee Dam American Engineers had to protect it from the catastrophic effects of overflowing Johnstown Pennsylvania 30th of May 1889. the town is hit by the heaviest rainfall in its history the Tranquility of a dam Reservoir was about to be shattered it rained for 24 hours and the water reached the top of the dam soon it had nowhere to go but over the top the dam failed and 20 million tons of water emptied in 45 minutes a wall of water 18
meters high crashed down the valley and hit Johnstown utter destruction ensued over 2 200 lives were lost in the flood worst disaster the U.S had ever seen why do dams Burst when they overflow engineer Ed McCann explains now a particular problem is when water flows over the top and weakens all of the ground the ground in front here they're very vulnerable to a thing called Toe scour and we're going to have a go at modeling to see if we can see what happens with toe scour this is our flood coming along in our River and
it fills up behind the dam we're right up at the top here now and the water will soon start pushing over the top and coming down and it will fall down this face and scour away underneath and you can see the dam starting to move already as the ground in front of it is lost the dam loses its foundation and begins to rotate over it won't be too long before it goes all together and bang which is a reasonably satisfactory Dam failure when it goes we get a tremendous wall of water come down the valley
and if you happen to be down there you're probably dead now well you can see their toe scare on this sort of dam is a huge potential problem it's something that absolutely has to be fixed [Music] in 1933 American Engineers started work on the Grand Coulee Dam across the Columbia River in the northwest of America it would need three times more concrete than the Hoover Dam and span three times the distance as the engineers completed the Grand Coulee Dam they had to make sure that what happened in Johnstown wouldn't happen here [Music] water rushing over
the dam could have quickly eroded the riverbed and caused disaster so the engineers formed the bottom of the dam into a concrete ramp [Music] the water shooting down the spillway into a tumbling Vortex which dissipated its energy as the water cascaded off the ramp it lost much of its destructive power with the ramp in place Engineers could safely run the largest hydroelectric dam in the U.S a title that the Grand Coulee Dam retained to this day the Builders of the Three Gorges Dam face a similar problem they too must make sure that their dam is
not damaged by flood water rushing through it [Music] basically the dam holds back a large volume of the water during the flood period here it can hold back about 22 billion cubic meters of water and then it's released in the controlled way through this system of 46 Spillway Gates and these chutes as you can see below me here the design of a Spillway like this has to deal with the force of the water as the drops over 100 meters in this case here and then achieves huge velocity at the bottom of the dam to deflect
the force of the water crashing down the Chinese use technology similar to the Grand Coulee as the water levels rise Engineers open a series of gates to drain the flood water from the reservoir but if the water fell straight down it could undermine the foundations of the dam so the engineers fit the spillway with concrete shoots unlike the Grand Coulee ramp which is underwater the Three Gorges shoots hurl the water into the air once Airborne the water breaks up into small droplets and loses much of its destructive energy it lands over a hundred meters Downstream
where it can't do any damage so now when they open their Spillway Gates the Chinese have nothing to worry about thank you back in 1942 the Grand Coulee showed how dams could deal with the abrasive power of flood water but to build a dam across the mighty yennessy river in Russia Engineers had to find a way to stop the water while keeping the ships moving [Music] in the 1960s the Soviet Union wanted to upscale its industrial power so they planned a series of gigantic dams [Music] one of the first the cruise noisk Dam would stretch
a whole kilometer across the river yennessy and generate 6 000 megawatts of power but this River was also the main shipping route into Siberia and would get blocked by the dam to keep the ships moving Engineers hatched an ingenious plan they decided to build a steel trough big enough to carry a ship then they planned to push trough and ship up to the top of the dam [Music] here they would spin the whole Contraption round and lower it back down to the river on the other side to move the seven thousand ton load they would
use hydraulic pumps [Music] engineer Ed McCann employs a hot water bottle to demonstrate the principle behind hydraulic power what water bottle is a is a pipe which goes into this bit of garden hose and is connected up to this little water tank here so let's see what happens I'm going to lift it up by about about a meter so I've lifted it up a meter now the pressure in this system has gone up but it's not gone up enough to lift this yet so there's no movement the hot water bottle is still squashed flat now
I'm going to stand back here because I don't want a load of blocks on my head so I'm lifting up it's about three meters now and you can see the concrete blocks moving very quickly now I'm going to take it up right to the top which is about four meters and there they go [Applause] what you can see there is the Amazing Power and force you can get out of water under pressure and that's what we use to lift big heavy stuff the Russian Engineers used liquid Under Pressure to lift their ship [Music] in the
walls of the chamber were powerful pumps which squeezed hydraulic fluid under immense pressure into a set of Motors mounted below these drove huge steel cogs that propelled the trough along a guide ramp the motors generated so much traction that they lifted the Chamber from River to Reservoir in only 90 minutes when the ship lift opened the citizens of krusnayask turned out in droves foreign Marvel was the crowning glory of the biggest dam in the world [Music] at China's three gorgeous Dam the engineers also face a major traffic problem their Dam sits on one of the
busiest rivers in Asia the Yangtze is a really important Waterway for navigation traffic in China leaving all the way from Shanghai the coast up to Yi Chang all the way to Chongqing it's been carrying about 18 million tons of freight per year getting about 170 ships a day over a dam that's more than 100 meters high is a tall order for the engineers befitting the biggest dam on Earth the Chinese solve it by building the biggest shiplock on Earth ships enter the lock at the bottom of the dam the gates close water floods in and
lifts the ships up to the next lock ships must go through five tiers of locks to get to the top which can take up to four hours fine for cargo ships but for the many passenger boats operating on the Yangtze it's just too slow to provide a more efficient Transit opportunity for passenger traffic they've built this ship lift system here which will allow boats to go through in about 36 minutes unlike the ship left at krusnayask the one of the Three Gorges will lift ships straight up like an elevator [Music] and the secret of its
success will lie hidden in its concrete walls [Music] Engineers will fit a series of massive counterweights that will do most of the lifting [Applause] [Music] sixteen one thousand ton concrete blocks will be connected by cables to the steel trough that will carry the ship and the water it floats in as the counterweights drop they will Hoist the trough upwards and lift the ship to the top [Music] um this chip lift here is 113 meters high and can handle vessels up to 3000 tons it'll make it the largest in the world and twice the size of
the one that crushed meowsk certainly when you look at the structure now it's got a ways to go in terms of construction it won't be finished till 2015 but it's it's clearly huge it's a another very impressive achievement underway here foreign [Music] dams have produced ever more power the day there is hardly a form of energy that is as clean as hydroelectric power but as dams grow bigger so does their impact on the environment in their design of the three gorgeous Dam Chinese Engineers have to make sure that their structure doesn't completely block Nature's Way
of feeding the land [Applause] [Music] the Three Gorges Dam produces more power than any other but that's not the main reason it was built the Yangtze River is notorious for its really severe flooding over the last two thousand years there's been about one major flood every 10 years in 1931 there was a really bad one killed about 135 000 people destroyed almost 2 million homes and so this is the main reason why they've built the Three Gorges Dam is to control this terrible flooding problem the dam blocks the path of the destructive flood water the
water is stored in its Reservoir and is then released in a controlled way [Music] managing flood water can also have serious environmental side effects as recent history has shown in 1970 Egyptian Engineers built the US-1 High Dam Across the River Nile to control flooding foreign [Music] but soon Farmers Downstream noticed that their harvests were beginning to fail their soil became so Barren that the farmers needed millions of tons of fertilizer every year to nourish their crops their land had suffered because it had been deprived of flood water which carries with it the vital building blocks
of life chemist Dr Andrew shidlow demonstrates so we have here our clean rain water which has been falling we're adding to it some good quality topsoil we then add some animal excrements we have some snail shells essentially made of calcium carbonate then we have some dried leaves plant vegetation here and of course fish as the storm proceeds as the water starts to flow rapidly all of these ingredients get mashed up in the hugely violent storm Waters which occur [Music] so here we have it a veritable cocktail of Mother Nature's most important plant nutrients nitrogen phosphorus
calcium magnesium and potassium but if flood water stops flowing these nutritious particles of silt will begin to settle this is a big problem especially at the biggest dam in the world [Music] the flow of precious yangtsy silt is blocked by the dam and trapped in the slow-moving water of the reservoir it rapidly sinks to the bottom where it builds up [Music] Consulting problem on the Yangtze is a huge problem total amount coming down is about 500 million tons per year which equates to about one kilometer Cube that's enough to fill big sports stadiums hundreds of
times it's a huge amount of silt [Music] if this silt remains trapped behind the dam it would mean that farmers fishermen and Wildlife would be deprived of nutrients in the water for hundreds of miles Downstream and the tons of settled silt or sediment could build up in the reservoir and threatened the dam itself basically sediment falling into the reservoir here would reduce the capacity the reservoir capacity and would eventually perhaps interfere with the ability to run the turbines if it was came up that high cleverly the Chinese Engineers exploit the power of flood water to
flush the sediment out of the reservoir and send it Downstream foreign they installed sluice Gates deep inside the dam each gate weighs as much as a bus and needs a powerful hydraulic piston to lift it up when The Operators open the gates flood water rushes over the trapped sediment and sweeps it through the dam [Music] this way the Chinese authorities hope that it will be at least another 100 years before the build-up of sediment affects power production at the time as the Three Gorges project draws to completion its scale is breathtaking even with some of
its turbines still to be switched on it produces more power than any other dam in the world standing on the shoulders of historic engineering Giants the Three Gorges really is the ultimate hydroelectric Dam until someone Builds an even bigger one [Music] [Applause] foreign [Applause] [Music]
