Dams and Hydroelectricity

Environment and climate change


Everyone who has electricity knows how convenient it is. You turn on a switch and your home has light. Electricity seems so simple. But did you ever wonder how electricity gets to your home? Let’s see how.

Hydroelectric dams create and supply electrical power. These dams are not like the dams you may be used to, though. They aren’t simple structures that block rivers using logs and twigs. Big hydroelectric dams are made out of cement and steel. Most are over 30 meters high, and some even reach up to 150 meters high.

Hydroelectric dams are built on large rivers to hold water back from the regular river flow. The bigger the dam, the more water it holds back. This backed?up water is kept in an area called a reservoir.

To make electricity, the water in the reservoir is forced to rise very high and then is dropped sharply through a pipe. At the end of this pipe are wheels called turbines. The force of the falling water makes these turbines spin. As they spin, they turn the generator which produces electricity. The electricity is carried across wire powerlines to stations where people direct the electricity to your home or factory. The water, meanwhile, goes back out into the river.

Where are these dams being built? Countries in Asia are very busy building large hydroelectric dams. Cambodia, India, Laos, Vietnam and China are constructing dams across many of their rivers to meet the growing demands of their people for water and electricity.

Big hydroelectric dams provide a clean and renewable source of electricity for homes and factories. These dams also provide farmers with water for dry croplands.

But hydroelectric dams have their bad points too. Large areas of land beside the rivers are flooded when these dams are built. Trees, plants and some animals die in these floods. And people who live along river banks are forced to move because of the floods. These people are often moved to areas that are worse than where they came from. They lose their homes, their customs and their way of life. For instance, a person whose family fished for generations may be forced to move to the mountains where he or she has to learn how to farm. The Three Gorges Dam on the Yangtze River in China, for example, will force about one million people to leave their homes by the time the dam is completed in the year 2020.

What’s more, these reservoirs of water can cause outbreaks of diseases. This is because standing water can become the home of insects carrying diseases, such as mosquitoes which transmit malaria. So, people who live near dams sometimes get sick.

Directing the water in the reservoirs to areas with dry crops helps farmers. But, like any watering project that uses river water, too much salt can end up in the soil and ruin it.

Big dams also change the natural flow and temperature of rivers, which can scare off or even kill fish. So, dams can cut off one important supply of food for people who live in the area.

As you can see hydroelectric dams have advantages and disadvantages. We can’t personally do much to control the building of these dams, but we can control how much water and electricity we each use. This means that people everywhere should use the water and electricity they do have more wisely. Simple things will help. For instance, turn off dripping water taps. Turn off lights that nobody is using. You might even want to find out how other energy sources, such as the rays from the sun, can heat your water and cook your food.


This script was written by Chris Szuskiewicz, a freelance writer in Toronto, Canada

Information sources

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“China moves the Yangtze,” by the Panos Institute in Development and Cooperation (D&C), No. 4, July/August, 1993, page 6. Deutsche Stiftung fur internationale Entwicklung (DSE), Postfach 30 32 10, D?10729 Berlin, Germany.

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