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Carillon Hydroelectric Power Station, Saint-André-d'Argenteuil, Quebec

Carillon Hydroelectric Power Station, Saint-André-d'Argenteuil, Quebec (P199 [CC BY-SA 3.0], Wikimedia Commons)

STEM in Context

How it Works: Hydroelectric Power

Digital Programs team


Learn how moving water can be used to generate electricity. This is called hydroelectric power generation.

In Canada, we often use moving water to generate electricity. This is called hydroelectric power. For short, we call it hydropower. Hydropower produces almost two-thirds of electricity in Canada.

Did you know?

Hydroelectricity generates 16% of all the electricity in the world.

Hydroelectric Power - How it Works (2014) by Ontario Power Generation (2:10 min.).

A hydroelectric system has pipes, a turbine, and a generator. The pipes are called the penstock. They direct the water. A hydroelectric system may also include a dam. Is there a dam near where you live?

Potential energy is stored energy. Kinetic energy is the energy of motion. Water in the reservoir has potential energy. When that water moves down into the turbine, it becomes kinetic energy. The moving water spins the turbine. This converts kinetic energy into mechanical energy. The turbine is attached to a rotor in the generator.

Parts of a hydroelectric system
Parts of a hydroelectric system (Let’s Talk Science using an image by Tennessee Valley Authority; SVG version by Tomia [CC BY-SA 3.0] via Wikimedia Commons).
Legend for image

A: Reservoir; B: Power station; C: Turbine; D: Generator; E: Intake; F: Penstock; G: Long distance power lines; H: River. Arrows show the flow of water.

How much energy does a hydroelectric system produce? Mostly, it depends on two things:

  1. the pressure of the water hitting the turbine 
  2. the volume of water passing by the turbine

Sometimes, dams are located above generators. These dams increase the pressure and control the volume of water. They help the hydroelectric station generate more electricity.
Hydroelectricity is a renewable resource. We can use the water over and over again to produce electricity. But there are some downsides to hydroelectricity, too. 

Hydroelectric systems divert natural water systems. This impacts water flow and can change the ecosystem. These changes can affect the plants and animals that live there. 

Some hydroelectric systems use dams. The reservoir behind a dam can be very useful. During dry periods, people can use this water for drinking water. They can also use this water for irrigation. They can even use this water for recreation.

Dam of the Ghost Reservoir, Alberta
Dam of the Ghost Reservoir, Alberta (Source: Ingo Schwarze [CC BY 4.0] via Wikimedia Commons).

But a dam can cause some problems, too. Dams can flood land. If land is flooded, people cannot farm or hunt on it. Flooding can also damage the ecosystem. For example, animals nearby might lose their habitat. The type of aquatic life in the area can change, too. 

When there is a flood, plants can decay under the water. This produces a greenhouse gas called methane

Finally, sometimes dams fail. This can cause a lot of damage to human and natural environments nearby.

There are many benefits to hydropower. But it is also important to weigh the risks!



Connecting and Relating
  • An electric company has plans to construct a hydroelectric dam in your area. What are your thoughts? Would you agree or disagree with the construction?
  • Have you ever seen a hydroelectric power plant up close? If so, where was it and what did it look like?
Relating Science and Technology to Society and the Environment
  • Hydroelectric power is often said to be one of the cleanest types of electricity generation. Would you agree with this? Why or why not?
  • What are the environmental and social impacts of building a hydroelectric dam?
  • Are there any ethical concerns with the construction of a hydroelectric facility? Explain.
  • If an environmental study of an area indicates a hydroelectric dam will have a negative impact on an ecosystem, should the project still be allowed to go ahead? Explain.
Exploring Concepts
  • What is hydroelectricity?
  • In general, where is an ideal location to construct a hydroelectric dam or facility?
  • How is electricity generated by a hydroelectric generating site?
  • How does the energy produced from a hydroelectric generating site get transported to our homes, schools and community?
Nature of Science/Nature of Technology
  • Should scientists help the public make a reasoned decision for supporting or opposing the construction of new hydroelectric generating facilities? Explain.
Media Literacy
  • When a new hydroelectricity generating facility is planned for an area, do you think media reports are more positive, negative or neutral in nature? Explain
Teaching Suggestions
  • This article can be used in Science and Physics for teaching and learning related to electricity, electricity generation and energy transformations. Concepts introduced include hydroelectric station, electrons, electricity, forebay, pinstock, turbine, rotor, electromagnets, stater, voltage, transformers, transmission lines, tailrace and renewable energy.   
  • Prior to viewing this video, a Write-Around Discussion learning strategy could be used to introduce the topic of renewable energy sources. Download ready-to-use BLMs using the Write-Around Discussion learning strategy for this article in [Google doc] and [.pdf]
  • Prior to viewing this video, teachers could also provide students with a Vocabulary Preview learning strategy to help introduce and consolidate new terminology. Ready-to-use BLMs are available in [Google doc] and [.pdf] formats. 
  • After viewing the video, teachers could have students use the ready-to-use BLMs of the Pros & Cons Organizer learning strategy to discuss the advantages and disadvantages of hydroelectric dams. These BLMs are available to download in [Google doc] and [.pdf] formats. 
  • Taking it further: Teachers could extend the Pros & Cons Organizer activity by either providing students with additional resources or having them conduct their own research to add to their knowledge of the positive and negative attributes of hydroelectric dams and continue to add to the pros and cons columns
  • To conclude, the teacher can facilitate a class discussion on the advantages and disadvantages of hydroelectric electricity generation with a focus on the question: “Do the advantages outweigh the disadvantages?”

Learn more

Five Things You Need to Know About Hydropower: Canada's Number One Electricity Source Waterpower Canada -- Article containing information about hydropower in Canada; includes stats, infographics, and images

Electricity Generation Games Hydro Quebec -- Includes interactive games to help demonstrate the generation of hydropower


Canadian Geographic. (2016). Canadian Hydropower Interactive Map. Retrieved from

Natural Resources Canada. (2017, December 13). About Renewable Energy. Retrieved from

Ontario Power Generation. Powering the next generation. Retrieved from