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HYDRO ENERGY: Understanding how Hydroelectric power works

By Jim-Rex Lawson MOSES

Hydroelectric energy is power made by moving water. Hydro comes from the Greek word for water. To harness energy from flowing water, the water must be controlled. A large reservoir is created, usually by damming a river to create an artificial lake, or reservoir. The water is then channeled through tunnels in the dam.

The power of water flowing through the dam’s tunnels causes turbines to turn. The turbines make generators move. Generators are machines that produce electricity.

Engineers control the amount of water let through the dam. The process used to control this flow of water is called the intake system. When a lot of energy is needed, most of the tunnels to the turbines are open, and millions of gallons of water flow through them. When less energy is needed, engineers slow down the intake system by closing some of the tunnels.

During floods, the intake system is helped by a spillway. A spillway is a structure that allows water to flow directly into the river or other body of water below the dam, bypassing all tunnels, turbines, and generators. Spillways prevent the dam and the community from being damaged. Spillways, which look like long ramps, are empty and dry most of the time.

From Water Currents to Electrical Currents

Hydroelectric power plants near waterfalls can create huge amounts of energy, too. Water crashing over the fall line is full of energy. A famous example of this is the hydroelectric plant at Niagara Falls, which spans the border between the United States and Canada.

Hydroelectric energy generated by Niagara Falls is split between the U.S. state of New York and the Canadian province of Ontario. Engineers at Niagara Falls cannot turn the falls off, but they can severely limit the intake and control the amount of water rushing over the waterfall.

The largest hydroelectric power plant in the world is the enormous Three Gorges Dam, which spans the Yangtze River in China. It is 185 meters (607 feet) tall and 115 meters (377 feet) thick at its base. It has 26 turbines and will be able to generate more than a billion watts of power. The Three Gorges Dam is operating, but engineers are still working on the system. They are adding even more turbines and generators to the project.

Environmental and Social Impacts

Hydro-electric power plants have lots of environmental impacts; some of these are just beginning to be understood. Until now there is an almost universal belief that hydro-power is a clean and environmentally safe method of producing electricity.

Hydro-electric power plants do not send out any of the standard atmospheric pollutants such as carbon dioxide or sulfur dioxide. In this respect, hydro-electric power is better than burning coal, oil or natural gas to produce electricity, as it doesn’t contribute to global warming. Similarly, it does not result in the risks of radioactive pollution associated with nuclear power plants.

The most obvious impact of hydro-power dams are the flooding of vast areas of land, much of them forested or used for agriculture before. The size of reservoirs created can be extremely large. Reservoirs can be used for ensuring adequate water supplies and irrigation, recreation; but in several cases they have flooded the homelands of local peoples, whose way of life has then been destroyed. A typical example is the recent flooding in the South-East and South- South Nigeria.  Many rare ecosystems are also imperiled by hydro-electric power development.

Large dams and reservoirs can have other effects on watershed. Damming a river can change the amount and quality of water in the river downstream. These effects can be reduced by requiring minimum flows downstream of a dam, and by arousing fish ladder which allow fishes to move upstream past the dam. Silt usually carried downstream to the lower reaches of the river, is hold up by the dam and deposited on the bed of the reservoir.

The silt can slowly fill up the reservoir, reducing the amount of water which can be stored and used for electricity generation. Bacteria incept decaying vegetation can also change to mercury, into a form which is soluble in water. The mercury cumuli in the bodies of fish and arose a health hazard to those who depend on these fish for food.

The water quality of many reservoirs also arise the health hazard due to new forms of bacteria which grow in many of the hydro rivers. Dams can facilitate the development of diseases. Possible dam failure is the worst impact that one could imagine. It would destroy everything to its step killing thousands of human lives, thousands of flooded hectares… total catastrophe.

Vegetation rotting under water produces methane. Emissions from northern reservoirs are typically about 5% of conventional power plants, while emissions from tropical reservoirs are typically 25%. High levels of total dissolved gas causes bubble disease in aquatic organisms and can lead to their death.


The advantages of the hydroelectric power stations are evident:

It doesn’t need fuel because it uses a renewable energy, constantly replaced by nature for free.

It’s clean, because it contaminates neither the air nor the water.

Often times, it can be combined with other benefits, like irrigation, protection against flood, water provision, ways and also navigation.

The maintenance and operation costs are low.

The hydraulic turbine is simple, efficient and safe. It can be started up and stopped quickly and requires very few attention.

It generates jobs in its construction, maintenance and operation.

It generates experience in these subjects and this makes the technology to be easily exported to developing countries.


The costs per installed kilowatt are frequently very high.

It alters the normal course in the biological life of the river.

The dam power stations have the problem of the water evaporation: In the zone where it is constructed, the relative humidity of the atmosphere increases as a result of the evaporation of the water contained in the dam.

In the case of the dam power stations constructed in tropical regions, some studies have demonstrated that they generate, as a result of the stagnation of water, big amounts of infectious bacteria and diseases.

The location of the hydroelectric power station, determined by natural causes, can be far from the centre of consumption and this can demand the construction of a electricity transmission system. Thus, it would increase the cost of the investment, maintenance and loss of energy.

The construction lasts more time than the construction of thermo electrical power stations.


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