Hydroelectric Dams: 12 Things (2024) You Need to Know

Today we have many methods of creating energy: solar, wind, geothermal, and fossil fuels–but for some reason, hydroelectric dams aren’t as famous as these others.

Yet, hydroelectric dams are the primary source of energy for many cities.

Which makes them a big player in our electrical network.

But how the heck do they work?

Well, although these structures just look like a big slab of concrete, there’s a lot going on that leads to the creation of energy.

So, how about we dive into all the things you need to know about hydroelectric dams?

From how they work to their advantages and disadvantages, you’ll learn the ins and outs of these fascinating structures.

And you might be surprised by just how interesting hydroelectric dams are!

So, without further ado, let’s get into it!

1. What is a Hydroelectric Dam?

A hydroelectric dam is a part of a greater hydroelectric facility that is built to generate electricity from the falling or flowing of water.

These structures are built to block the flow of a river, causing standing bodies of water (referred to as water reservoirs), which can then be used through a process that we’ll cover below to make energy.

Water reservoirs can also be used as a water supply and irrigation for nearby cities and towns.

Hydroelectric dams come in all shapes and sizes.

They have to be constructed in a way that works with the geography, so each one truly has its own thumbprint.

There is also no standard size for these dams. Some are massive, like the Hoover Dam, and others can be surprisingly small–again, it all depends on the landscape and size of the river.

The world’s first hydroelectric dam was built in 1882 on the Fox River of Wisconsin.

Since then, thousands of these structures have popped up around the world, and they’re now an important supplier of energy.

Now that we have an idea of what a hydroelectric dam is, let’s take a look at how they work.

2. How Do Hydroelectric Dams Work?

Hydroelectric dams block the natural flow of a river, causing the water levels to rise behind the structure.

This standing body of water is known as a reservoir.

These dams have large tunnels that direct the water from the reservoir down a shoot (called a penstock) and through a turbine propeller.

The flow of water spins the shaft of the turbine, which is connected to a generator above to generate electricity–genius, right?

Energy from the generators is then sent through a transformer to power lines or power stations, which towns and cities can use.

Once the water passes through the turbines, it flows down draft tubes and flows out the other end of the dam.

It’s a fairly straightforward process, but dealing with massive amounts of water is tricky business, and there is a lot of room for error.

If you had to guess, how long do you think a hydroelectric dam lasts?


Keep reading to find out!

3. How Long Do Hydroelectric Dams Last?

A hydroelectric dam can last upwards of 100 years.

That’s a fairly long time.

And with continuous upgrades, these dams can actually last much longer.

To keep everything running smoothly and to ensure they reach their full lifespan, maintenance is crucial.

But with regular monitoring and careful planning, hydroelectric dams don’t require a lot of major work or manpower to operate them.

However, dams that aren’t properly maintained can result in a world of problems that constantly need to be solved.

Some of the less fortunate circumstances that can happen are water flowing over the top (overtopping), unstable foundations, cracking, and faulty piping.

The good news is that massive dam tragedies are far and few between.

There are about ten dam failures per year in the U.S., which isn’t bad when you consider that there are almost 100,000 dams in the country!

So, if you live near a dam, don’t worry too much about it collapsing and wreaking havoc. The chances of that happening are razor-thin.

4. How Are Hydroelectric Dams Built?

Have you ever wondered how in the world hydroelectric dams are built?

It seems impossible to build a structure over a flowing river, but there’s a way!

Building a hydroelectric dam requires a lot of planning.

The water of the river first has to be diverted so that the foundation area can be prepared, which includes excavating rocks and looking for stable and unstable ground.

It’s very important that the initial foundation is built on solid ground to avoid shifting in the future.

Concrete is then poured into columns or blocks one layer at a time.

Once the first layer of concrete is dried, the next one can be added.

It’s a very time-consuming process that cannot be rushed.

As the dam gets higher and higher, and the necessary penstocks and generator facilities are built, water will slowly be diverted back to its original route to begin creating a water reservoir.

All in all, it can take upwards of 8 years to build a dam, depending on its size (smaller projects can be completed in a couple of years).

The Hoover Dam, for example, took five years to build–pretty fast for such a massive structure, huh?

5. What Are the Advantages of Hydroelectric Dams?

Hydroelectric dams come with a lot of benefits.

It’s one of the cheapest energy sources, and it can be relied on for 100+ years.

Hydroelectric dams also supply energy directly to the grid, which is hugely beneficial during power outages and disruptions.

Since hydroelectric dams only rely on the force of water, it’s renewable!

Although there are some environmental disadvantages to these dams, they are a clean source of energy and a safe way to generate electricity.

If we compare a nuclear power plant to a hydroelectric dam, I think we could all agree on which one is less dangerous, right?

Hydro dams give virtually every state and country a local way to produce energy, which reduces and eliminates the dependence on other places to provide electricity.

On top of all the great advantages in terms of generating renewable power, hydroelectric dams also create a lot of jobs.

The current hydropower industry in the U.S. employs around 300,000 jobs!

6. What Are the Disadvantages?

Hydroelectric dams come with many advantages, but there are a few serious disadvantages that need to be considered.

Let’s first talk about their impact on the environment.

Hydro dams block the natural flow of the river, which causes problems upstream and downstream.

When reservoirs are created, it floods the surrounding area, which impacts the creatures that live there.

Additionally, constructing a dam requires new roads to be built and powerlines to be installed, disrupting the natural habitat.

A dam can also greatly impact fish migration.

In fact, according to some reports, four dams in Washington are the primary reason why salmon may soon be gone from the Snake River.

The fish are of vital spiritual importance to the Nez Pierce and other Columbia River Basin tribes, which is why they and other local politicians are advocating for the removal of the dams.

And if fish kills aren’t enough, hydroelectric power is also not always 100% reliable.

Water levels aren’t consistent, and droughts do happen.

During dry periods, hydroelectric dams are virtually worthless, and with the pressing issue of climate change, there’s no telling which rivers will dry up and when.

Lastly, although hydroelectric dams are safe, the possibility of catastrophe exists.

The best example of this was in 1975, when a typhoon in China caused a dam to fail, resulting in over 150,000 casualties.

The chances of this happening are very unlikely, but the danger is there.

7. Are Hydroelectric Dams Good for The Environment?

Whether or not hydroelectric dams are good for the environment is debatable.

On the one hand, they are better for the environment because they don’t burn fossil fuels.

The only greenhouse gases they release are from decomposing organic materials.

Luckily, their emissions rate is usually the highest for the first 10 to 20 years and then begins to decrease.

So, hydro dams don’t contribute to air pollution, acid rain, or climate change.

But that doesn’t mean the hands of these dams are entirely clean, either.

Hydro dams are quite intrusive to the surrounding environment.

They disrupt the migration of fish, their reservoirs flood into surrounding areas, and new infrastructure disrupts or displaces natural habitats.

Hydroelectric dams create a catch-22.

They’re a clean, renewable form of energy, which is good for the planet, but they are harmful to the surrounding nature.

So, are they good for the environment?

Yes and no.

But hydropower is, without a doubt, cleaner and safer than many other forms of energy.

8. What is the Largest Hydroelectric Dam in the US?

Do you think you know the largest hydro dam in the United States?

It’s not the Hoover Dam…

The largest hydroelectric dam in the United States is the Grand Coulee Dam!

Although the Grand Coulee Dam is not the tallest of the bunch, with a height of 550 feet–that reputation goes to the Oroville Dam, standing at 770 feet–it is still the largest in the country.

The structure spans 5,223 feet, which is just under a mile–impressive, to say the least.

It’s been calculated that the 12 million cubic yards of concrete used to construct the site is enough to build a highway from Miami to Seattle.

That’s a lot of cement.

Each year, the Grand Coulee Dam generates upwards of 21 billion kilowatt-hours of electricity–enough energy to provide a yearlong supply of electricity to around 2 million homes.

The Hoover Dam only generates around 4 billion kilowatt-hours each year.

So, yeah, the Grand Coulee Dam is by far the largest hydroelectric dam in the United States.

9. What is the Largest Hydroelectric Dam in the world?

The Grand Coulee Dam may be impressive, but it is not the largest hydroelectric dam in the world–not even close.

The largest hydroelectric dam in the world is the Three Gorges Dam in Yichang, China.

It stands 607 feet tall and stretches for 7,660 feet!

In 2021 the dam successfully generated 100 billion kilowatt-hours of electricity–yes, 100 billion.

Suddenly, the largest hydroelectric dam in the United States doesn’t seem so big, huh?

Oh, and if you thought the structure was big, the Three Gorges Dam’s reservoir spans 400 square miles.

It’s worth noting that China is also home to the second-largest hydroelectric dam in the world.

The Baihetan Dam’s opening ceremony was in 2021, and it’s expected to generate around 64 billion kilowatt-hours of electricity.

China is so keen on using hydropower due to the country’s lack of fossil fuel reserves and not wanting to rely on other countries for energy.

10. What Percentage of the US’s Electricity Comes from Hydroelectric Dams?

Although hydroelectric dams aren’t something you come across every day–unless you live by one–they make up a decent amount of the United States’ electricity generation.

Currently, hydroelectric dams make up about 6.3% of all the electricity generated in the United States.

But they’re also responsible for generating 31.5% of all renewable electricity.

California, Oregon, and Washington (as a whole region) are responsible for generating the most hydropower in the country. Those three states combined produce about 115 billion kilowatt-hours of electricity per year.

Now compare that to China’s Three Gorges Dam, which produces 100 billion kilowatt-hours by itself, and you’ll start to get an idea of how massive it truly is.

New York is actually the fourth-highest producer of hydropower in the United States, generating around 28 billion kilowatt-hours of energy.

A considerable sum, but still far away from the 70 billion kilowatt-hours generated in Washington alone.

11. Why Doesn’t the US Have More Hydropower?

The reason the United States doesn’t have more hydropower is that many of the best locations for dams are already in use, and the environmental impact is not something to simply ignore.

Each new hydro dam has to be strategically designed and located to ensure the negative implications are worth the rewards.

If a dam is put somewhere that could severely disrupt the environment, in the grand scheme of things, it can be just as harmful as nonrenewable forms of energy.

So, hydropower is a bit tricky to plan out.

With that being said, the Department of Energy has announced that hydropower in the United States could expand to a total of 50% of all the renewable energy generated (it’s currently at about 31.5%).

In the next few decades, we’ll see whether or not this vision comes to fruition or if another renewable energy source becomes the top dog.

12. Is Solar Power Better Than Hydroelectric?

Solar power and hydropower both have their benefits, but which one is better?

Well, hydroelectricity is more reliable than solar power, but it’s difficult to find the right locations to build dams.

Solar power, on the other hand, can be installed almost anywhere, and it even gives individuals the option to install solar panels in their homes.

Neither form of energy is entirely clean.

Solar power requires the mining of certain materials to build panels (requiring equipment that creates greenhouse gases), while hydroelectric dams cause major disruptions in the environments around them.

With that being said, once solar panels are made, they have less of an impact on the surrounding area.

The problem with hydroelectric dams is that there are not many ways to make them less intrusive, whereas solar companies are continuously working to make solar panels more efficient and find more sustainable ways to produce them.

Final Thoughts

After reading this article, I can assure you that you’ll never look at a hydroelectric dam the same way again.

And you shouldn’t!

They are remarkable structures that are capable of generating immense amounts of power.

In fact, the energy powering your device right now may have come from hydroelectricity!

Of course, hydroelectric dams are not without their faults, but until we are able to find a better solution, they’re a damn good option–pun intended.

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Erika Gokce Capital

Disclaimer: we are not lawyers, accountants or financial advisors and the information in this article is for informational purposes only. This article is based on our own research and experience and we do our best to keep it accurate and up-to-date, but it may contain errors. Please be sure to consult a legal or financial professional before making any investment decisions.


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