00:00The concrete of this imposing structure is cracking under the pressure of thousands of tons of water.
00:04A slight seismic shake then occurs,
00:07shaking the situation.
00:10The old dam does not resist.
00:12A torrent of water spills through cracks that widen at an alarming speed,
00:16exerting a devastating force on the stone wall that collapses.
00:21In an instant, the building disappears under the assault of roaring waves,
00:25drifting with an uncontrollable force towards the village nestled in the valley.
00:30When a dam reaches the age of 50,
00:32it enters a period called alert.
00:35This term actually designates a critical point
00:38where its maintenance becomes much more complex,
00:40while the associated risks increase.
00:43A recent study carried out by the Institute of the United Nations for Water, Environment and Health
00:49revealed that the United Kingdom and Japan
00:51had the largest number of dams in this category.
00:54This is not surprising.
00:56In these two countries, the average age of dams exceeds largely a century.
01:00If you are also wondering about the reasons
01:03why so many dams reach this canonical age at the same time,
01:07the answer is quite obvious.
01:09The middle of the 20th century was marked by a frenzy of construction.
01:13Between the end of the 1950s and the 1970s,
01:16more than 1,100 dams were built each year.
01:19But, as early as 1990,
01:22this frenzied rhythm has slowed considerably,
01:25with less than 500 new dams per year.
01:27Since the 2000s, this figure has decreased again,
01:31falling below 300.
01:33The biggest problem lies in the fact that many of the dams built
01:36during this post-war boom are aging simultaneously today,
01:40while many countries face degraded infrastructures.
01:43And what happens when these works reach a critical state?
01:47In the absence of rigorous maintenance, they risk collapsing,
01:51which could cause disasters
01:53both for water supply and for public safety.
01:56This is similar to a gigantic game of aquatic jenga,
01:59where it is imperative to prevent the whole from collapsing.
02:03A tragic example of such a disaster occurred with the Bankiao Dam,
02:07built in 1952.
02:10In 1975, it collapsed under the torrential rains caused by the Nina Typhoon,
02:16causing the loss of nearly 240,000 lives.
02:19One of the main causes of this tragedy was a flawed design.
02:23The dam was not designed to withstand extreme climatic conditions.
02:27When the region was hit by unprecedented intensities,
02:31it collapsed under pressure.
02:33You are probably wondering if the one near you is at risk.
02:37If its name is on our list of the most dangerous dams in the world,
02:41it would be wise to move.
02:44The Hoover Dam is one of the highest in the United States.
02:47It rises on the Colorado River,
02:49at the border between Nevada and Arizona.
02:51With its 220 meters of height,
02:54it offers an impressive spectacle
02:56and is a formidable source of energy.
02:59The thickness of its base is equivalent to the length of two football fields
03:03and each downpour can handle a volume of water comparable to that of Niagara Falls.
03:08However, experts warn of the catastrophic consequences
03:11of a possible collapse of this gigantic building,
03:14which would put millions of lives at risk.
03:16This risk is all the more worrying
03:18as the dam is aging and is located in a seismic zone.
03:22The Almandra Dam, the highest in Spain,
03:25was built between 1963 and 1970.
03:30Its main role is to regulate the flow of the Torres River,
03:34and this work is far from trivial.
03:36A simple human error could cause considerable damage.
03:40It is therefore a serious concern for the populations living downstream.
03:44The Jinping-Yi Dam, also known as the first Jinping Waterfall,
03:49holds the title of the highest dam in the world with its 305 meters of height.
03:54Located in China, it was built to control the flow of the Yalong River.
03:58This impressive structure plays a crucial role,
04:01producing 16 to 18 billion kWh per year.
04:05To put this into perspective,
04:07an average American household consumes about 11,000 kWh per year,
04:11which means that the Jinping hydroelectric power plant
04:14can power about 1.6 million homes.
04:17The Kariba Dam is an impressive construction
04:20located on the Zambezi River,
04:22on the border between Zambia and Zimbabwe.
04:24Although several authorities share the task of its maintenance,
04:28reports indicate that urgent repairs are necessary.
04:32Without these interventions,
04:33the dam could cause major damage in the surrounding regions.
04:37It is therefore imperative to monitor this giant.
04:40The Mosul Dam, considered one of the most dangerous in the world,
04:44has a disturbing peculiarity.
04:46It is composed of friable mud rather than concrete.
04:49This design flaw causes constant erosion,
04:52the mud being slowly carried away by the water.
04:55Teams are working tirelessly to ensure maintenance and repairs,
04:59but this site remains a major source of concern.
05:02The Diduki Dam, located in the state of Kerala, India,
05:06is a spectacular double-curved mud dam on the Periyar River.
05:10Ranked among the highest mud dams in Asia,
05:13it retains an immense amount of water.
05:16A problem on this dam would lead to tragic consequences
05:19for vast regions,
05:20risking the lives of many people.
05:23Therefore, its maintenance is essential
05:25to guarantee the safety of all.
05:27The Three Gorges Dam in China
05:29is one of the most imposing works in the world
05:32and houses the largest hydroelectric power plant on the planet,
05:35completed in 2012.
05:37It rises to nearly 185 meters and expands to 2,335 meters,
05:42more than half the width of Manhattan at its narrowest point.
05:46This titanic construction
05:48has even had notable repercussions on the earth itself,
05:51notably influencing the rotation of our planet, according to experts.
05:55As impressive as it is,
05:57this dam represents considerable risks
05:59for the environment and safety.
06:01It has been built in a region subject to earthquakes,
06:05a worrying factor.
06:06In addition, the accumulation of sediment in its reservoir
06:09could affect its stability.
06:11During its construction,
06:12more than a million people had to be relocated
06:15and the ecosystem was deeply impacted.
06:18Recognized for its aesthetic appeal,
06:20the Monticello Dam in the United States
06:23attracts thousands of curious people every year.
06:25One of the reasons why people are so eager to go there
06:29is its fascinating Glory Hole.
06:31Although it may seem picturesque at first glance,
06:34this Glory Hole actually represents an open door to danger.
06:39It is essentially a huge concrete funnel
06:42that stands at the top of the dam.
06:44When the water level in the lake exceeds 134 meters
06:47above sea level,
06:49thus approaching the overflow,
06:51the water begins to evacuate through this funnel
06:54like a bathtub that empties.
06:56This phenomenon creates a fascinating whirlwind,
06:59but it is better to avoid approaching it
07:01so as not to run the risk.
07:03Located on the Columbia River in the state of Washington,
07:06the Grand Coulee Dam has been supplying electricity
07:09to the northwest of the Pacific since 1942.
07:12It contains nearly 9.1 million cubic meters of concrete,
07:16which would allow to build a sidewalk
07:181.20 meters wide and 10 centimeters thick,
07:21by going around the equator twice.
07:24However, this impressive structure also presents challenges.
07:28Over 80 years old,
07:30it requires special attention for its maintenance.
07:33In addition, its location in a seismic zone
07:36raises questions about its stability.
07:38The Kurobe Dam, in Japan,
07:40is a wonder of 186 meters high,
07:43completed in 1963.
07:45However, with the years,
07:47it shows signs of aging
07:49and frequent earthquakes in Japan
07:51increase the risks associated with this dam.
07:53In addition,
07:55the region is often affected by torrential rains,
07:58able to exert additional pressure on the entire structure.
08:02The Tarbela Dam, located on the Indus River,
08:05is the largest compacted earth dam in the world.
08:08Completed in 1976,
08:10it faces challenges such as sediment accumulation,
08:14which reduces its storage capacity.
08:16In addition, climate change has disrupted water flow,
08:21thus endangering the stability of this monumental structure.
08:25The main utility of the dams lies in irrigation,
08:28allowing water to flow towards crops.
08:31Indeed, about 40% of the food consumed worldwide
08:35depends on these hydraulic infrastructures.
08:37Then, hydroelectricity is one of their main functions.
08:41The dams act like gigantic batteries,
08:44transforming the flow of water into energy.
08:46They also contribute to water supply,
08:49flood control,
08:51and offer recreational activities
08:52such as sailing and fishing.
08:55Given the aging of the dams,
08:57measures must be taken to protect living populations,
09:00including those living nearby.
09:02The United States is an example of this
09:04by initiating the dismantling of dams,
09:06which have already removed more than 1,200 structures
09:09over the past 30 years.
09:11Old dams are not only dangerous,
09:14but also expensive to maintain,
09:16making their dismantling often more judicious.
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