Advantages and Disadvantages

Advantages:

• Hydroelectricity is a renewable energy source.


• Operation and maintenance costs for hydroelectricity plants are much lower than for thermal electricity power plants. Breakdowns are few because their mechanical design is relatively simple, and no excess heat is generated during operations.


• Hydroelectricity generating plants have a long life.


• When a hydroelectricity water storage dam is built, the water in the dam can be used as a source of drinking water and for recreational purposes such as boating and fishing.


• To meet any changes in demand for electricity, hydroelectricity generators can be stopped and started in minutes. A fossil fuel power station can take up to eight hours to shut down or restart and a nuclear power station can take up to several days.


• Although dams prevent the natural flushing out of a river during a flood, they also control flooding downstream in times of high rainfall and snowmelt.


• Hydroelectricity is one of the most efficient energy sources because most of the kinetic energy of the water is converted to electrical energy.


• No greenhouse gases or other dangerous gases are produced by the hydroplant.
  

Disadvantages:

• Usually a large area of land has to be flooded to ensure a continuous flow of water to the turbine. In some cases when a dam is built, large populations have to be relocated. In China, the Three Gorges Dam Project on the Yangtze River will displace more than 1 million people. (Reference: http://ipsnews.net/news.asp?idnews=39621)
  
• Dams affect river ecosystems. Rivers usually experience seasonal flooding that flush out river backwaters and deposit silt on riverbanks. Dams prevent those seasonal floods and allow silt and vegetation to clog up river backwaters. This causes changes to the environments, which may impact plant and animal habitats.


• Hydroelectricity dams are costly to build (though less costly then other power plants)


• An adequate supply of water from rain or snow is required for hydroelectricity plants to continue operation. If a drought occurs, electricity production can be severely affected. Countries that produce hydroelectricity need alternative electricity supplies for such events.