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Hydroelectric Power

Hydroelectric power is a topic that you study in relation to several sections of your geography GCSE and also in different subjects, for example science. You need to know about it in the context of land use (e.g. how we use fold mountains), renewable energy sources and also the hydrological cycle (e.g. dam building). It is useful to know and understand the factors that influence the siting of hydroelectric power plants and the conflicts these schemes create as well as the basics of how it works.

Hydroelectric power generates electricity from flowing water. The energy it produces is clean, in other words, no waste materials, greenhouse gases or other pollutants are produced as the electricity is generated. It is possible to generate small amounts of electricity from the water flowing along a river or stream, however, commercial power plants work by storing water behind a dam in a reservoir.

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Water flows through large turbines which contain blades connected to a central shaft that is also connected to a generator. The movement of the shaft is used in the generator to generate electricity.

Dams are built for several different reasons. Some are built as a hard engineering option to manage river flow, reducing flooding downstream. The inclusion of a hydroelectric plant is a secondary concern. Water is held back by the dam and released in a controlled manner. This can ensure a steady flow of water throughout the year rather than the usual seasonal variations. Other dams are built to provide water supplies for cities and some are built with the single idea of generating hydroelectric power. Quite often, the reservoirs and surrounding areas are used for leisure activities like sailing and hiking.

Building a dam for even a small hydroelectric scheme is usually very expensive and can take many years. Before building begins, the best location for the dam needs to be researched and there must be at least one public enquiry as many people will be affected. At the enquiry, each interest group presents their case. When a dam is constructed, land must be drowned. This land is usually being farmed and may also contain woodlands and in some cases, farmhouses and communities like hamlets or even whole villages will be covered by the water. It is important that the needs of everyone, including the flora and fauna, are taken into account. Although hydroelectric power is clean and renewable, it still has an effect on the environment. Hydroelectric power stations need to be built on a huge scale (like the Three Gorges Dam in China) if they are to generate similar amounts of electricity to conventional methods.

Dams for hydroelectric power are usually built in the upper course of rivers. The valleys are narrower so the dams are not as wide, cutting construction costs. There is usually more rain which ensures that electricity production is at a maximum. In fold mountains, e.g. the Yuncan dam in the Peruvian Andes, melting snow can provide most of the water. The disadvantage of that is that production will be reduced during the winter.

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  1. Where does the electricity from most hydroelectric schemes go?
    Hydroelectric power stations can be started up very quickly to put extra electricity into the National Grid when electricity demand is high
  2. What is the name of the device that turns the generators to make electricity?
    This is linked to a generator via a gearbox
  3. Which of the following is a good reason for building a hydroelectric power dam?
    No fuel is burnt to generate the electricity so no polluting gases are emitted
  4. Which of the following is not a valid socio-economic disadvantage of building a large hydroelectric scheme in the mountains of Scotland?
    When farmland is flooded, farmers need compensation for their loss of income. Where communities are lost because they will be underwater when the dam is full, the people need to be given new homes to live in. Getting the materials to a remote mountain location is costly
  5. Why are hydroelectric power schemes usually sited in the upper course of rivers?
    There are other reasons too like the narrow deep valleys mean that narrow dams can store a lot of water but are cheaper to build
  6. Which of the following is an environmental problem that is associated with hydroelectric power?
    The access roads require aggregates which has to be quarried and transported to make the road. The road destroys wildlife habitat and can disturb the flow of surface water
  7. Which of the following statements about hydroelectric power is true?
    Hydroelectric scheme dams are expensive to build. Water is a renewable resource and mountainous areas are excellent places for hydroelectric schemes
  8. In China, the Three Gorges Dam on the Yangtze river is the largest hydroelectric power station in the world and caused great controversy before it was built. Which of the following is the least likely to be a reason that some people did not want it to be built?
    The building of the dam has lead to the extinction of a river dolphin that was only found in the Yangtze
  9. Hydroelectric dams can be used to control ...
    Water can be released in a predictable way which can ensure that there is a constant flow below the dam. This can help local communities downstream by reducing the likelihood of flooding
  10. Although hydroelectric dams flood large areas of the countryside, reducing the amount of farmland, they can also bring long-term economic benefits to the local economy. How?
    They can be used for water sports and fishing. The surrounding hillsides can be developed to provide paths for walkers and tracks for mountain bikers and other cyclists. Construction jobs are only temporary whilst the dam and power station are being built

Author: Kev Woodward

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