Hydropower can be defined as a source of renewable energy produced by fast-flowing water. It is responsible for producing 90 percent of all renewable electricity and 17 percent of the world’s total electricity.

Hydropower Plant
Image by GS S from Pixabay

Hydropower is believed to be the first and simplest method of electricity generation. In many places, hydropower is also used to operate many mechanical devices along with the production of electricity. A hydropower plant, however, is more focused on producing electricity on a large scale. 

How do Hydropower Plants Work?

Hydropower plants are generally made on the basis of the conversion of energy. Big dams are built on large rivers which have a significant drop in elevation. The dams are responsible to store water which contains potential energy. When the water inlet is open, gravity causes the water to flow through the penstock (a large tunnel). At the end of the penstock, there is a big turbine propellor which is turned by moving water.

The turbine converts the kinetic energy of flowing water to mechanical energy. The mechanical energy is then converted into electrical energy with the help of a generator which is based on the principle of electromagnetic induction. Power lines are connected to the generator which helps to carry electricity to various places. 

A Brief History

Water wheels or Watermills, the earliest form of hydropower, dates back to 4th Century BC, in regions like Iran and Egypt. The Roman Empire used water-powered mills for processing grains and sawing marbles. China, during the time of engineer Du Shi, used water wheels to piston-bellows in forged cast iron. 

During the Islamic Golden Age, engineers made a variety of water-powered devices including fulling mills, paper mills, and hullers. By the 11th century, North Africa, the Middle East, and Central Asia had industrial watermills do the heavy work. Using dams to store water power and extensive use of water turbines also fostered in this period.

Hydropower became the source of electricity in the late 19th century after the development of modern water turbine. The world’s first Edison hydropower plant was built on Fox River in Appleton, Wisconsin on September 30, 1882, which generated 12.5 kilowatt-hours of electricity. Today, hydropower plants produce more than 3000 terawatt hour annually with China being the highest hydroelectricity producer (about 20% of the total). 

Advantages of Hydropower Plants

1. Renewable source of energy

Hydropower is a renewable source of energy which means they are naturally replenished and we cannot use it up. Problems like scarcity of electricity will not be a matter of concern as hydroelectricity will be available all the time. Also, this helps to conserve the limited and renewable sources of energy like petroleum.

2. Clean energy source

Hydropower plants produce energy without emitting any greenhouse gases or toxic byproducts that can pollute the environment. This makes hydropower plants a clean source of energy which helps mitigate world issues like climate change and global warming.

3. Price Stability

Non-renewable sources of energy like petroleum and coal are subject to an increase or decrease in price with market volatility. But river water, the source of hydroelectricity has nothing to do with market fluctuations which results in guaranteed price stability.

4. Recreational Opportunities

The lake formed by the dam can be used for various recreational activities like fishing, swimming, and irrigational purposes. Dams have the capacity to store a tremendous amount of water which can be used for various activities when there’s a scarcity.

5. Higher flexibility

The output of electricity can be easily controlled by controlling the flow of water. At times when electricity consumption is low, the hydropower plants can be adjusted easily to yield less energy and opposite when there’s high demand. This gives the ability to produce as the exact amount of energy we want which is fairly difficult in cases like nuclear energy.

6. Development of rural areas

The farther energy has to be supplied, the more difficult and costly it is. But if there are hydropower plants in various different places in the country, it can cover more places. This way, the remote communities will get a huge uplift as electricity is one of the key infrastructures of development.

7. Employment opportunities

According to the National Hydropower Association, about 300,000 workers are provided employment in Hydropower plants in the US alone. It is estimated that the hydropower industry has the potential to provide 1.4 million job opportunities. Providing employment to people along with electricity production is a huge win.

8. Durability

Hydropower plants are considered to be a one-time investment. They have an average life span of 50-100 years meaning one plant can support many future generations. Also, the maintenance cost is relatively low compared to the outcome. The flowing water which is the primary part of the hydropower plant is also completely free.

Disadvantages of Hydropower Plants

1. Environmental Impacts

Although hydropower plants are non-polluting, they cause other environmental problems. Interrupting the natural flow of water also has an effect on the river ecosystem. Hydropower plants also affect the land use and natural habitats of other animals.

2. High Initial Capital

Construction of power plants is very expensive and hydropower plants are no exception. Challenges like topography and building underwater make building a power plant really expensive. A 500 kW hydropower plant can cost you well over 1.5 million pounds which is an average estimate as generalizing is really difficult in this case.

3. Risk of Drought

The amount of water available is directly related to the amount of energy produced. If a severe drought occurs, rivers tend to dry up resulting in no or very less hydroelectricity generation. This has been a serious concern in east African countries. Power cuts are usually followed up by the drought.


While there are some disadvantages of Hydropower plants, the advantages clearly outweigh them. Being a renewable source of energy, they are far more reliable than other sources like petroleum or coal. They are also comparatively safe as it does not include combustion of any kind. The long term benefits of hydropower plants are truly notable and are the reason why electricity is available to everyone so cheaply.