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

electricity comes from
hydroelectric dams.

Dams create electricity using
stored water.

Dams store water from rivers and
spring melt into reservoirs.

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

a penstock.
From the top of the dam to the

bottom.
The falling water spins blades

in turbines.
Those spinning blades are

connected to a generator.
Those generators use magnets and

copper coils to create
electricity which is sent out on

power lines.
Some rivers also have specially

designed turbines to capture the
power of moving water to create

electricity.
But dams and turbines do change

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

like salmon that need a free
flow to migrate downstream.

Hydroelectric power is
considered a green source of

energy because it doesn't
require the burning of fossil

fuels.
Most dams in the United States

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

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

check out the science trek
website.

You'll find it at science trek