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Joan Cartan-Hansen, Host: More 
than seven percent of America's

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electricity comes from 
hydroelectric dams.

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Dams create electricity using 
stored water.

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Dams store water from rivers and 
spring melt into reservoirs.

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Dam managers then allow water to 
flow through a long pipe called

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a penstock. 
From the top of the dam to the

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bottom. 
The falling water spins blades

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in turbines. 
Those spinning blades are

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connected to a generator. 
Those generators use magnets and

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copper coils to create 
electricity which is sent out on

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power lines. 
Some rivers also have specially

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designed turbines to capture the 
power of moving water to create

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electricity. 
But dams and turbines do change

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the course of rivers. 
And that can be deadly for fish

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like salmon that need a free 
flow to migrate downstream.

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Hydroelectric power is 
considered a green source of

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energy because it doesn't 
require the burning of fossil

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fuels. 
Most dams in the United States

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don't generate electricity, but 
scientists say they could be a

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potential new source of power. 
For more information about dams,

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check out the science trek 
website.

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You'll find it at science trek