Rivers and Streams

Hydroelectric Power (Dams)

The Bonneville Dam along the Columbia River in Oregon
What is a dam?
A dam is a man-made structure built across a river. Most dams are built to control river flow, improve navigation, and regulate flooding. However, some dams are built to produce hydroelectric power.

How do dams make hydroelectric power?
These are electric turbines inside a dam. When water from the dam passes through, the turbines spin. This creates electricity.

Hydroelectric power is produced as water passes through a dam, and into a river below. The more water that passes through a dam, the more energy is produced. Once a dam is built, an artificial man-made lake is created behind the dam.

Electricity is produced by a device called a turbine. Turbines contain metal coils surrounded by magnets. When the magnets spin over the metal coils, electricity is produced. Turbines are located inside dams. The falling water spins the magnets.

Dams provide clean, pollution free energy, but they can also harm the environment. Species that use rivers to spawn are often hurt by dams. In the Northwest, sockeye salmon and trout populations have dropped from 16 million to 2.5 million since hydroelectric plants were built on the Columbia River. Dams all over the world have hurt some species. 

What are the highest dams in the U.S.?
The highest dam in the Unites States is located near Oroville, California. The Oroville Dam rises 754 feet (230 meters) and is more than a mile (1.6 km) wide. This dam was built in 1968, 22 years after the Hoover Dam. The Hoover Dam, on the Nevada-Arizona border controls the Colorado river. It is 726 (221 meters) feet high and stores 21.125 million acre-feet (2.6 million hectare-meters) of water in the 115 mile (192 km) long Lake Mead reservoir, behind the dam. 

Where is the highest dam in the world?
The highest dam in the world is Nurek Dam on the Vakhsh River in Tadzikistan, a country in central Asia. This dam is 984 feet (300 meters) tall! 

Questions for you to answer:

  • Can you find these places on a map? 
  • Why do you think dams are so important there? 

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