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A hydroelectic power station in Germany
The energy of falling water has been used by humans for thousands of years.[1]

Hydroelectricity is electricity that is made by the movement of water. It is usually made with dams that block a river to make a reservoir or collect water that is pumped there. When the water is "let go" the huge pressure behind the dam forces the water down pipes that lead to a turbine, this causes the turbine to turn, which turns a generator which makes electricity. This use of renewable energy produces less pollution than steam engines do. Some places such as Norway and Quebec get most their electricity this way.

Hydroelectric power plants

Rank Station Country Location Capacity (MW)
1 Three Gorges  China 30°49′15″N 111°00′08″E / 30.82083°N 111.00222°E / 30.82083; 111.00222 (Three Gorges Dam) 22,500
2 Itaipu  Brazil
25°24′31″S 54°35′21″W / 25.40861°S 54.58917°W / -25.40861; -54.58917 (Itaipu Dam) 14,000
3 Xiluodu (in construction)  China 28°15′52″N 103°38′47″E / 28.26444°N 103.64639°E / 28.26444; 103.64639 (Xiluodu Dam) 10,780
4 Guri  Venezuela 07°45′59″N 62°59′57″W / 7.76639°N 62.99917°W / 7.76639; -62.99917 (Guri Dam) 10,235
5 Tucuruí  Brazil 03°49′53″S 49°38′36″W / 3.83139°S 49.64333°W / -3.83139; -49.64333 (Tucuruí Dam) 8,370
6 Grand Coulee  United States 47°57′23″N 118°58′56″W / 47.95639°N 118.98222°W / 47.95639; -118.98222 (Grand Coulee Dam) 6,809

Advantages of hydroelectricity

The way the electricity is produced does not harm the environment as much as fossil fuels like oil or coal. Hydroelectricity is very powerful, safe and produces no waste.

Hydroelectricity can be made very quickly. This makes it useful for times when demand for electricity is high. Water that has been stored in a dam can be released (let go) when needed, so the energy can be made quickly. This ability to control also makes a good match for less controllable intermittent energy sources. When the wind isn't blowing or the sun isn't shining, hydroelectricity can be released.

Also hydroelectricity cannot run out as long as there is a good water supply. Once the dam is built the electricity costs very little, no waste or pollution produced and electricity can be generated whenever wanted.

A few hydro turbines do not have a dam but instead use the current of the "run of the river". They produce less electricity and cannot store energy for later use.

Disadvantages of hydroelectricity

The building of large dams to hold the water can damage the environment. In 1983 Australian government stopped the Tasmanian state government from building a dam on the Gordon River in Tasmania after a huge public protest.[2] The dam would have flooded the beautiful Franklin River. The Three Gorges Dam in China will be the world's largest hydroelectricity project. The dam has flooded a huge area, meaning that 1.2 million people have had to be moved. Scientists are concerned about many problems with the dam, such as pollution, silt, and the danger of the dam wall breaking.[3]


  1. Earth Science. Holt, Rinehart and Winston. 2001. pp. 211. ISBN 0-03-055667-8 .
  2. "History of the Franklin River Campaign 1976-83 — The Wilderness Society". Retrieved 2009-07-02.
  3. "Three Gorges Dam". Retrieved 2009-07-02.

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