You probably know water is powerful, but did you know that we can use that power in our homes? This lesson introduces you to hydropower, and tells you how it works.

Hydropower Basics

Crashing waves, roaring rapids, splashing rain…water is always on the move! It takes a lot of energy to move water over and around our planet. That energy can be captured in the form of electricity as water moves from one location to the next. The electricity we get from this water is called hydropower.

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How Does Hydropower Work?

Hydropower plants are usually built on rivers, and often use structures called dams to collect or control the passing water. The water flows into the dam and goes through a spinning generator. The generator uses the water’s kinetic energy, or energy of motion, to produce electricity. That electricity is passed into power lines and used for all sorts of things, like lighting street lamps and powering video games. The water continues to flow out of the dam and down the river.

A hydroelectric dam captures energy from moving water, and uses it to produce electricity.
hydroelectric dam

Building a dam along the river causes water to back up behind it, forming a man-made lake called a reservoir. Water is allowed through the dam through motorized spillways. Some hydropower plants are called run-of-river plants, meaning that they do not cause water to back up behind them. A portion of the river or stream is channeled through a smaller power plant, and later rejoins the river.

Dams used for hydropower often create lakes called reservoirs.

The Pros and Cons of Hydropower

Hydropower is one of our cheapest energy sources, and is a form of renewable energy. This means that the energy source is never totally used up. Water is constantly flowing back into rivers when it rains, or when snow melts. It also creates less pollution than the burning of oil or coal. Reservoirs created by dams can serve as a water source, and also provide space for recreational activities like fishing and boating.

Hydropower has a lot of things going for it, but it also carries some risks. Damming a river changes the surrounding environment, which may cause problems for plants and fish. And poorly built dams have collapsed, leading to major flooding and loss of life. Scientists and engineers know about these issues, and work hard to prevent them.

Engineers monitor hydropower plants closely to make sure they operate safely.

Engineers keep a close eye on dams to make sure they are operating safely, while environmental scientists monitor the surrounding environment to make sure animal and plant populations remain healthy, and step in to help when needed. Many dams have fish ladders that help fish move past the dam, which is one way to reduce environmental problems.

Lesson Summary

Hydropower is electricity generated by moving water. Hydroelectric plants are often built on rivers, using dams to control the water flow. Hydropower is renewable, and creates less pollution than other energy sources, but can harm the local environment. Scientists and engineers keep a close eye on hydropower plants to make sure they run safely.