Efficiency of hydro power | BCHydro Power Smart for Schools

Improving the efficiency of water power

Decide which changes to water power technology have increased the efficiency of hydro power the most.

Activity Image
25 mins
Thought starter


By examining changes in water power technologies, deepen their understanding of the formula used to calculate mechanical efficiency.  


What you'll need

  • Digital projector and screen
  • "Improving the efficiency of water power" worksheet
  • "Water power" handout
  • "Mechanical efficiency of water power" slideshow

  1. Organize your students into pairs and provide each group with a copy of the "Improving the efficiency of water power" worksheet and the "Water power" handout.
  2. Bring up the "Mechanical efficiency of water power" slideshow. Show slide 2, and suggest that the slide shows a water wheel from 1895. This type of water wheel was used to directly power industrial machinery and also generate electricity. Water wheels such as these could be up to 30m (100 feet) in diameter. 
  3. Show slides 3 and 4, and invite groups to identify similarities and differences in energy input, energy output, and where energy is lost between the two water power systems. Prompt students to record the differences and their effects on efficiency on their worksheets.
  4. Ask your students to suggest what changes may have improved the efficiency of water power the most. Encourage students to share their decisions and thinking with the class. Student responses might include size of the water wheel, the amount and speed of water flowing into/onto the water wheel, and the type of materials. 
  5. Show slide 5 and briefly explain that efficiency is calculated as a ratio of output divided by input energy and can be expressed as a percentage. 
  6. Show slide 6 and invite groups to describe how each of these factors would affect either the numerator or denominator of the efficiency formula. Prompt groups to note these factors on their worksheets beside either the numerator or denominator of the efficiency formula.
  7. Ask groups to sort the differences noted on the top of their worksheet beside either the numerator or denominator of the efficiency formula.
  8. Invite groups to share their decisions and thinking with the class. 
  9. Conclude the activity by showing slide 7 and inviting groups to suggest which change improved the efficiency of water power the most. 

Curriculum Fit

Physics 11

Big ideas

  • Energy is found in different forms, is conserved, and has the ability to do work.


  • Power and efficiency

Curriculum competencies

Questioning and predicting
  • Demonstrate a sustained intellectual curiosity about a scientific topic or problem of personal, local, or global interest
  • Formulate multiple hypotheses and predict multiple outcomes
Processing and analyzing data and information
  • Seek and analyze patterns, trends, and connections in data, including describing relationships between variables, performing calculations, and identifying inconsistencies
  • Construct, analyze, and interpret graphs, models, and/or diagrams
  • Use knowledge of scientific concepts to draw conclusions that are consistent with evidence
  • Analyze cause-and-effect relationships
Applying and innovating 
  • Implement multiple strategies to solve problems in real-life, applied, and conceptual situations
  • Communicate scientific ideas and information, and perhaps a suggested course of action, for a specific purpose and audience, constructing evidence-based arguments and using appropriate scientific language, conventions, and representations


Assess your students’ ability to:

  • Use details in diagrams to infer improvements in efficiency
  • Use the efficiency formula when describing changes in water power technology


Select the materials you require for this activity or download all

Water Power Handout

87.9 kb pdf

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