What Is The Definition Of Hydropower?

What is the definition of hydropower?

Hydropower, or hydroelectric power, is electricity generated using the energy of moving water. It is one of the oldest and largest sources of renewable energy in the world. The term hydropower refers to the conversion of the kinetic energy in flowing water into electrical energy.

Humans have been harnessing the power of water for thousands of years. Water wheels were used in ancient Greece to grind wheat into flour. In the late 19th century, hydropower played a major role in the electrification of many countries. Today, it continues to serve as a reliable source of renewable power around the world.

Hydropower is considered renewable since it uses the earth’s water cycle to generate electricity. Rain and snow replenish the water used in rivers and reservoirs. In 2019, hydropower accounted for around 16% of total electricity generation globally, making it an essential part of the world’s renewable energy portfolio https://www.eia.gov/energyexplained/hydropower/.

How Hydropower Works

Hydropower uses the energy of flowing or falling water to produce electricity. Hydropower plants capture the energy of moving water to generate electricity. There are three main components of a conventional hydropower plant: a dam, turbines, and generators. The dam stores river water in a reservoir and controls its flow. When water is released from the reservoir, it flows through turbines, causing them to spin. The spinning turbines power the generators to produce electricity.

A dam creates a height difference in the water, called head, and forms a reservoir. The amount of electricity that can be generated depends on the volume of water flow and the height from which it falls. When water is released from the reservoir through intake gates, it flows down large pipes called penstocks and turns the blades of the turbines. The most common types of turbines used in hydropower plants are Francis or Kaplan. As the turbines spin from the moving water, their mechanical power turns generators to produce electricity. The electricity is then transferred via cables to transformers where voltage is increased for transmission on the grid.

(Source: https://www.energy.gov/eere/water/how-hydropower-works)

Types of Hydropower Plants

There are three main types of hydropower plants: impoundment, diversion, and pumped storage plants. Each type varies in design and how it harnesses the energy from flowing water (Energy.gov, 2023).

Impoundment plants are the most common type of hydropower plant. They use a dam to store river water in a reservoir, which is then released through turbines to generate electricity. The height of the water behind the dam creates potential energy, allowing impoundment facilities to generate power on demand when electricity is needed. The water can be released as needed for electricity generation (Hydropower.org, 2023).

Diversion hydropower plants channel a portion of a river through a canal or penstock, where the moving water rotates turbines. They do not require dams or impoundments, making their environmental impact smaller. However, they provide less control over power generation compared to impoundment plants (Energy.gov, 2023).

Pumped storage hydropower plants function differently, as they store energy rather than generate it directly. Water is pumped uphill into a reservoir at times of low electricity demand. Then during peak demand, the water is released downhill through turbines to generate extra power (Hydropower.org, 2023).

Small hydropower systems with under 10 megawatts capacity are considered micro hydropower plants. They provide localized renewable energy solutions with minimal environmental impacts (Energy.gov, 2023).

Hydropower Generation Capacity

Hydropower currently provides about 16% of the world’s electricity supply, making it the largest renewable energy source for electricity generation globally. As of 2021, the total installed hydropower generation capacity worldwide was approximately 1,308 gigawatts (GW).

China has the highest installed hydropower capacity in the world, with over 350 GW as of 2021. This accounts for over a quarter of the global hydropower capacity. Other top countries for hydropower capacity include Brazil, Canada, the United States, and Russia, all of which have over 100 GW of installed capacity.

The development of hydropower capacity has continued to grow steadily over the past decade. From 2011 to 2021, global hydropower capacity increased by over 25%. The largest growth has occurred in emerging economies in Asia, South America, and Africa. For example, hydropower capacity in India doubled in the past 10 years.

The future outlook for growth in hydropower generation remains positive, especially in developing countries that have untapped potential hydro resources. However, growth in some established markets such as North America and Europe is expected to be more modest. Overall, the International Hydropower Association projects total global hydropower capacity could reach nearly 2,000 GW by 2030 if development continues at the current pace.

Advantages of Hydropower

Hydropower offers several key advantages that make it an important renewable energy source (https://www.energy.gov/eere/water/benefits-hydropower):

Renewable: Hydropower is considered a renewable energy source because it relies on the water cycle. As long as there is adequate water supply, hydropower can be generated again and again.

Reliable: Hydropower can deliver a very stable and reliable supply of energy. The flow of water that drives hydro turbines is relatively predictable compared to other renewable sources like wind and solar power.

Flexible: Hydropower plants can ramp up and down very quickly to meet shifts in energy demand. Reservoirs provide storage capacity so power can be generated on demand.

Low Operating Costs: Once a hydropower system is built, it has relatively low maintenance and operational costs compared to other energy sources. Fuel costs are zero since hydropower relies on water.

Disadvantages of Hydropower

While hydropower is a renewable and clean source of energy, it also comes with some downsides. Two major disadvantages of hydropower plants are the high upfront costs and the potential impacts on rivers and wildlife.

Constructing a hydropower plant requires a massive financial investment. Significant infrastructure like dams, reservoirs, tunnels and turbines needs to be built. According to the U.S. Department of Energy, the average cost for hydropower projects larger than 30 megawatts is between $1,500 per kilowatt to $2,500 per kilowatt of capacity. The huge upfront costs mean it can take many years for hydropower projects to become profitable.

Hydropower facilities, especially large dams, can also negatively impact river ecosystems and habitats. The dams obstruct the natural flow of rivers which can harm the migration and spawning of fish species. Flooding land for the reservoir also destroys forests and wildlife habitats. One study by Washington State University researchers found the average hydropower dam reduces a river’s biodiversity by 25% https://kiwienergy.us/pros-and-cons-of-hydroelectric-energy/. Proper planning and mitigation measures like fish ladders can help reduce the environmental impact.

Notable Hydropower Projects

Some of the most noteworthy and famous hydropower projects around the world include:

The Three Gorges Dam in China is one of the world’s largest power stations. Built on the Yangtze River, it has a generating capacity of 22,500 MW, supplying energy to central China. Construction began in 1993 and was completed in 2012 after displacing over 1 million people. While providing emission-free energy, it has also raised environmental concerns over habitat loss ([1], [2]).

The Itaipu Dam on the Paraná River bordering Brazil and Paraguay is one of the largest operational hydroelectric dams with 14,000 MW capacity. Construction started in 1975 and was completed in 1991 after displacing 10,000 families. Itaipu supplies 17% of Brazil’s electricity and holds the record for the most energy generated by a hydroelectric plant ([3]).

The Hoover Dam on the Colorado River bordering Nevada and Arizona, USA generates over 4 billion kWh annually. Built between 1931-1936, it was one of the largest hydro projects of its time, supplying electricity to several states. Hoover Dam created Lake Mead, which supports recreation, water supply and flood control ([4]).

Small Scale and Micro Hydropower

Small scale and micro hydropower projects produce up to 100 kW and 1 MW of electricity, respectively. They are an attractive option for remote communities that lack access to an electricity grid. Micro hydropower systems make use of small rivers and streams with low head heights between 1 to 20 meters. The small scale allows these projects to be cost effective and have low environmental impact.

Some of the major benefits of micro hydropower include: It has a high return on investment compared to other renewable sources because of consistent output. Micro hydropower can provide energy access to remote communities and improve quality of life. The technology can last for decades with proper maintenance. Projects utilize local water resources without the need for dams or reservoirs, minimizing environmental impact.[1]

Some example micro hydropower projects include the 75 kW system providing electricity to Ghandruk village in Nepal and the 45 kW generator lighting up Huancavelica province in Peru.[1] With decreasing costs and modular designs, micro hydropower has strong potential for growth globally. Small scale hydro could realistically provide electricity access to over 150 million people by 2030.[1]

Future of Hydropower

The future looks bright for hydropower, with projections for significant growth globally over the next decade. According to the International Energy Agency (IEA), global hydropower capacity is set to increase by 17%, or 230 GW, between 2021 and 2030. This growth will be driven by rising electricity demand and commitments by governments to increase renewable energy generation.

Much of the hydropower growth is expected in emerging economies in Asia, Latin America and Africa. China alone aims to boost its hydropower capacity by 25% by 2025. Major new projects are underway on rivers like the Congo, Mekong and Brahmaputra. However, developed regions like North America and Europe will also see continued growth in the hydropower sector.

Advancements in turbine technology and civil engineering techniques will enable further exploitation of hydropower resources globally. New variable-speed turbine designs can optimize efficiency across a wider range of water flows. Pumped storage capacity is also expected to grow significantly, providing vital grid storage and stability services.

The growth of small scale and micro hydropower will broaden access to clean electricity in rural areas of developing countries. With modular and standardized turbine designs, small hydropower can be quickly deployed across river networks.

Nevertheless, new hydropower projects face environmental challenges and scrutiny. Sustainable development of dams and reservoirs will require balancing energy needs with impacts on ecosystems and communities. With proper planning and management, hydropower’s immense potential can be harnessed while safeguarding biodiversity.


In summary, hydropower is an important and efficient renewable energy source that provides several benefits. Hydropower plants capture the energy of flowing water to generate electricity, using turbines and generators without combustion or pollution. The different types of hydropower plants allow electricity generation in various water settings and capacities.

Globally, hydropower accounts for around 16% of electricity generation, making it the largest renewable energy source. With the proper geographical conditions, hydropower can provide clean, reliable baseload power. Advantages of hydropower include its fuel-free operation, low operating costs, system flexibility, and minimal greenhouse gas emissions. It also enables energy storage and flood control capabilities.

However, hydropower relies on suitable water conditions and has high upfront infrastructure costs. Dam-based projects can impact local ecosystems, habitats, and communities. Yet innovations in low-head, run-of-river, and small hydro plants are minimizing environmental impacts. Overall, hydropower will continue serving a vital role in renewable energy production, energy storage, and electricity access worldwide.

In conclusion, hydropower harnesses the renewable power of water for clean electricity generation. When developed responsibly, hydropower provides a sustainable energy solution with economic and environmental benefits.

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