| Jr. Feature |

The Dam That Slowed Down Earth 

Let’s take a deep dive into the Three Gorges Dam

What if I told you that the world’s biggest dam is so massive that it literally caused the earth’s rotation to slow down?

I know, it sounds crazy, but it’s a fact. The Three Gorges Dam (which sounds like it’s gorgeous but is actually pretty ugly) was supposed to prevent devastating floods from destroying villages along the Yangtze River in China. Instead, the world’s largest concrete structure has turned into a giant disaster, with endless repercussions.

Let’s take a deep dive into the Three Gorges Dam.

Okay, we got it. The Yangtze River is immense and important. But where do the curses come in?

The great flood of 1931 was the first clue. The Yangtze River is very prone to flooding. On average, the river floods once every ten years. And when the river overflows its banks, it floods in a big way.

Every time the Yangtze River floods, the cost is exorbitant. Tens, if not hundreds, of thousands of lives are lost. Repairs cost billions of yuan and take years. Basically, just as soon as everyone has recovered, another flood hits.

There had to be some solution to the disaster-in-waiting that is the Yangtze River. That solution was the Three Gorges Dam.

The Yangtze River

China is one of the world’s largest countries and has the world’s largest population. So, it makes sense that they like doing things in a big way. As the world’s largest dam and concrete structure, the Three Gorges Dam certainly checks off a lot of boxes in the “big” department. (The sidebar has lots of jaw-dropping numbers about just how ginormous the Three Gorges Dam is.) But besides for the large factor, why was the dam built?

China makes the top ten list of countries that suffer from the most natural disasters. In fact, did you know that the world’s very worst natural disaster happened in China? It was the Yangtze River Flood of 1931, which affected 50 million people, and in which 3.7 million people died.

The Yangtze River (which is the third-longest in the world, and the largest river to run through a single country) has been the source of blessings and curses for the Chinese. Through the centuries, the Yangtze has been vital for trade and transportation. The Yangtze flows right across China, making it perfect for traders who want to ply their wares all over the country. The massive river is also used by farmers to irrigate their fields. This is super important, as 35% of China’s grain is grown in the Yangtze River basin. (A river basin is the area that a river and all its tributaries cover.) Since humans have always established settlements along rivers, it won’t surprise you to learn that 40% of China’s population lives in the Yangtze River basin.

A dam will do it

The Three Gorges is a geographical location along the Yangtze River. It is where the Yangtze flows between three gorges (a gorge is a narrow valley with steep cliffs, like a canyon). It was in 1919 that the idea of building a dam in this place first came up. The idea belonged to Sun Yat-sen, who was an important Chinese politician. (In fact, Sun Yat-sen is known as the “Father of the Republic of China.”) He figured that building a dam in this exact spot would generate 33 million horsepower, or 22 gigawatts of electricity — which is a lot! Of course, it would also help to prevent flooding further downriver. (Read the sidebar for more info on how dams work.)

It took decades for Sun’s idea to turn into reality. There were lots of starts and stops along the way. In 1932, the first plans for the dam were drawn up. But things skidded to a halt when war broke out with the Japanese in 1939 (the Second Sino-Japanese War), and the Japanese took control of the area.

In 1944, an American engineer drew up a new set of plans for the dam. Fifty-four Chinese engineers traveled to the US for training in preparation for the dam’s construction. But then another war broke out (this time it was the Chinese Civil War of 1947), and that was the end of that.

Fast forward to 1992, when the dam was finally approved by the National People’s Congress. Construction began in 1994… and didn’t end until 2006.

A terrible secret

War wasn’t the only thing that delayed the dam. The Three Gorges Dam had been controversial almost from the beginning. It’s true that the dam was built to save lives, but many lives were destroyed during its construction. Experts who realized that this would happen fought against the building of the dam.

Dams are like spoiled princesses. They need their space and creature comforts. The bigger the dam, the more space it needs. For a hydroelectric dam to be effective, its reservoir needs to be as large as possible. Guess how that reservoir is created? By submerging everything in its way.

If that sounds terrible and tragic, it’s because it is. Dams may save future lives from floods, but they only manage to do that by wreaking havoc first. Turns out, the engineering wonder that is the Three Gorges Dam is hiding a terrible secret.

How do hydroelectric dams work?

Dams have been around for centuries. At first, dams were built to prevent flooding and to store water in the reservoir — the water body created at one end of the dam.

During the rainy season, water collects in the reservoir instead of being allowed to flow downriver. This helps to lower the river’s water levels. When it begins to rain, the river has space for all that rainwater and won’t overflow its banks. After the threat of flooding is over, the dam is opened to allow a controlled amount of water to flow into the river once more.

When hydropower became a thing in the late 19th century, engineers realized that dams could multitask. Not only could dams control the water flow along a river and prevent flooding, but they could generate electricity at the same time.

Most dams look like simple concrete structures that do nothing but hold back water. Don’t let this façade fool you. Inside all that concrete, you’ll find a bunch of generators. When water is released from the reservoir down into the river below, it passes through turbines. All the power of rushing water rotates the turbines like mad, which in turn causes the generators to generate electricity. That electricity can be stored for when it’s needed, at which point it is used to power whatever needs powering — think homes, businesses, and factories.

Too high a price

To create the Three Gorges Dam and its massive reservoir, two cities, 114 towns, and 1,680 villages were flooded. Take a moment to think of all those homes, stores, schools, parks, farms, and businesses that literally disappeared overnight. Over one million people were forced to leave their homes. Many of these were ancestral homes that had been lived in by the same families for generations. Now, they had to start again from scratch in a new place.

Beneath the reservoir of the Three Gorges Dam lies an entire world. It’s not just a tragic thing that this world was lost forever, it’s also toxic. In those cities, towns, and villages that were flooded were 1,300 factories and mines, 40,000 graveyards, and 200 landfills. All those chemicals and hazardous waste was released into the Yangtze River, making it even more toxic than it already was. This was disastrous for the wildlife in the river.

A lot of history was buried in the reservoir, too. The area of the Three Gorges Dam was once home to 1,282 cultural heritage sites. Several of the most important ones were relocated. One UNESCO site was turned into an awesome underwater museum. But the rest were buried in a watery grave, forgotten forever.

Landslides and earthquakes

The catastrophic results of the dam didn’t stop after it was built. If anything, things have gotten worse, and there doesn’t seem to be an end in sight.

Experts warned that the dam would cause landslides by creating too much pressure on the surrounding cliffs. Their warnings came true in 2003, when the reservoir began to be filled. The pressure caused 700 million cubic feet of rock to slide into the Quinggan River, very close to where it flows into the Yangtze. This caused huge waves, which killed 14 people. Since then, landslides in the area have become a fairly common phenomenon, and one of them killed another 30 people.

The dam sits near two geographical fault lines — fault lines are fractures, or breaks, between two blocks of rock. The huge amount of water in the reservoir presses down on these fault lines, triggering earthquakes. According to the China Earthquake Administration, between 2003 (when the reservoir began to be filled) and 2009, 3,429 earthquakes were recorded along the reservoir. In comparison, just 94 earthquakes had been recorded from January 2000 to May 2003.

Earth, slow down

Now, you might be thinking, “It’s sad and all, but what does this have to with me?” Well, I’m here to tell you that the Three Gorges Dam affects our entire planet.

NASA says that the dam is so huge, it is visible to the naked eye from space. And that’s not the only thing that NASA has to say about the dam. According to NASA, the dam has caused the earth’s rotation to slow down!

This is due to a scientific phenomenon called “moment of inertia.” Try spinning on one leg with your arms opened wide. Now fold your arms in front of you and spin again. You’ll notice that you spin faster with your arms closed. That’s because you’ve reduced your moment of inertia to increase angular velocity. In simple terms, that means that when an object is tucked into itself, it will spin faster. And the opposite is true as well. If an object is spread wide, it will spin slower.

Let’s take this back to our dam. In order to generate as much hydroelectricity as possible, the dam’s reservoir had to be made as large as possible. The water level in the area of the reservoir was raised by 90 meters. Suddenly, there was a lot more weight in one place than there had been before. According to NASA, this affected the earth’s moment of inertia, and caused our planet to slow down.

NASA says that the dam slowed earth down by 0.06 microseconds, which means that our day is now a teeny bit longer than it was before. But it’s not just time that changed. The changing of the earth’s rotation also changed the positions of the North and South Poles by 0.8 inches. And you’re gonna love this last one. A change in the earth’s rotation also affects our weight. So, because of the Three Gorges Dam, we’re all a little bit heavier.

Does the dam actually work?

The dam was supposed to be the answer to China’s prayers. It was supposed to stop those terrible floods from stealing millions of lives. It was supposed to create renewable energy for a good percentage of the population. But does it do those things?

The answer to the second question is ,“yes!” Without a doubt, the Three Gorges Dam is a modern-day wonder when it comes to hydropower. The dam is the world’s largest hydroelectric powerplant, and an amazing source of renewable energy.

The answer to the first question is, “debatable.” In 2020, the Yangtze River reached its highest water levels in 60 years. The flood affected 54.8 million and killed 158 people. As you can imagine, people were in an uproar. “You said the dam would stop this from happening!” they cried.

A professor at the University of Alabama said that this flooding showed that the Three Gorges Dam could not prevent severe floods. “This dam has been fully operational for many years now,” he said, “and now we have the highest water level ever recorded.”

Is the dam making things worse? The Chinese government denies this. It claims that if not for the dam, the 2020 flooding would have been much worse.


(Originally featured in Mishpacha Jr., Issue 948)

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