Renewable energy
Hydropower is readily available; engineers can control the flow of
water through the turbines to produce electricity on demand.
In addition, reservoirs may offer recreational opportunities, such as
swimming and boating.
A typical hydro plant is a system with three parts: an electric plant
where the electricity is produced; a dam that can be opened or closed
to control water flow; and a reservoir where water can be stored.
Hydroelectric power provides almost onefifth of the world's
electricity.
China, Canada, Brazil, the United States, and Russia were the five
largest producers of hydropower in 2004.
The first hydroelectric power plant was built at Niagara Falls in
1879.
Negative aspects of hydropower
Damming rivers may destroy or disrupt wildlife and other natural
resources.
Hydropower plants can cause low dissolved oxygen levels in the
water, which is harmful to river habitats.
Hydroelectric power plants don't work for a very long time.
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