What Are Three Hydropower Examples?

What is Hydropower?

Hydropower, also called hydroelectric power, is the process of using the energy from flowing water to generate electricity. It is one of the oldest and largest sources of renewable energy in the world. Hydropower plants capture the energy created by falling or fast-running water to produce power using the following process:

  • A dam is constructed to control the flow of water and create a reservoir.
  • The water in the reservoir flows through large pipes called penstocks towards turbines within the hydropower plant.
  • As the water moves past the turbines, it causes them to spin rapidly.
  • The spinning turbines turn electromagnets within a generator to produce electricity.

Hydropower is considered a renewable energy source because it utilizes the earth’s continuous hydrologic cycle to generate power. It does not rely on any fuel sources that could be depleted over time. Hydropower generation also does not directly produce greenhouse gas emissions like fossil fuel-based power plants.

Compared to other energy sources, the benefits of hydropower include its ability to quickly adjust electricity output to meet demand as well as its long project lifespan. Hydropower plays an important role in the renewable energy sector and makes up over 15% of global electricity generation (Energy.gov, 2023).

History of Hydropower

Humans have harnessed the power of moving water for centuries. Ancient civilizations used water wheels to grind grains into flour and saw lumber. The Greeks used water wheels for tasks like milling wheat into flour over 2,000 years ago. However, it wasn’t until the late 19th century that hydropower began to be used for generating electricity.

In the early 1880s, the first hydroelectric power plants were built in the United States and the United Kingdom. These pioneering projects helped spur the development of hydropower infrastructure across North America and Europe in the early 20th century. The Hoover Dam, completed in 1936, was one of the first large hydroelectric power complexes. The massive dam on the Colorado River was the largest in the world at the time and generated electricity for the developing cities of the American Southwest.

Today, hydropower accounts for over 16% of global electricity generation and is the most widely used form of renewable energy. According to the International Hydropower Association, the total installed capacity worldwide is approximately 1,308 gigawatts as of 2022. China, Brazil, Canada, the United States, and Russia are the leading producers of hydroelectricity globally. With growing concerns over climate change, many countries are investing in hydropower as a clean and renewable energy source.

Hoover Dam (USA)

The Hoover Dam is located on the border between the U.S. states of Nevada and Arizona. Construction on the dam began in 1931 and was completed in 1936 (Encyclopedia Britannica).

The specifications of the Hoover Dam are impressive. The dam is 726 feet high and 1,244 feet long at its crest. It contains over 4 million cubic yards of concrete (U.S. Bureau of Reclamation).

The Hoover Dam has a power generation capacity of over 2,000 megawatts. Its 17 main turbines generate billions of kilowatt-hours of hydroelectric power each year, which is distributed across Nevada, Arizona, and California (Wikipedia).

The Hoover Dam stands as an engineering marvel and was considered one of the largest concrete structures in the world at the time it was built. The project employed thousands of workers during the Great Depression and provided needed jobs and electricity to the growing Southwest U.S. (Encyclopedia Britannica).

Three Gorges Dam (China)

The Three Gorges Dam is a hydroelectric gravity dam located along the Yangtze River in Sandouping, Yiling District, Yichang, Hubei province in central China. Construction on the dam began in 1994 and was completed in 2008.

The Three Gorges Dam is 2,335 meters (7,660 feet) long and has a total generating capacity of 22,500 MW from 32 generators, making it the world’s largest capacity hydroelectric power station (Encyclopedia Britannica). The dam is 181 meters (594 feet) high and created a reservoir that extends 660 km (410 miles) and contains 39.3 cubic km (39.3 billion cubic meters) of water (Wikipedia).

Construction of the dam and its massive reservoir has had significant environmental and social impacts. It led to the flooding of many villages, towns and cities, requiring the relocation of 1.3 million people. The dam has affected endangered species like the Yangtze River dolphin and altered the river’s ecosystem. There are also concerns about increased risk of landslides and seismic activity due to the immense pressure and weight of the dam and reservoir on the region’s geology.

Itaipu Dam (Brazil/Paraguay)

The Itaipu Dam is a hydroelectric dam on the Paraná River located on the border between Brazil and Paraguay. Construction began in 1975 and was completed in 1982, making it a joint effort between the two countries. At 196 meters tall, Itaipu was the world’s tallest dam at the time of completion and is currently the second largest operational hydroelectric facility in terms of annual generation, producing over 100 terawatt-hours in 2016.

The dam is 7,235 meters long and 225 meters high. With an installed generation capacity of 14 GW, Itaipu has the world’s largest hydroelectric power generating capacity and supplies approximately 75% of the electricity consumed in Paraguay and 17% of that consumed in Brazil.

In terms of generation capacity, the Itaipu Dam is comparable in size to the Three Gorges Dam in China, which has a capacity of 22.5 GW. However, it produces nearly twice as much electricity as the Grand Coulee Dam in the United States, which has a capacity of 6.8 GW.

The massive size and power generation capabilities of the Itaipu Dam highlight the potential of hydropower to produce renewable energy on a large scale when countries cooperate on projects.

Advantages of Hydropower

Hydropower offers several advantages as an energy source:

Renewable Resource – Hydropower relies on water, which is continuously renewed through Earth’s natural water cycle. Unlike fossil fuels which take millions of years to form, hydropower is considered a renewable energy source because it is replenished at a rapid rate through the water cycle. Hydropower is an ideal “clean energy” for producing electricity sustainably over the long term.
(Benefits of Hydropower)

flowing water turning a hydropower turbine to generate renewable electricity
Low Operating Costs – Once a dam is built and infrastructure is in place, operating costs are very low compared to other energy sources. No fuel costs are needed. With regular maintenance, hydropower facilities can reliably generate electricity for decades. This makes it a very affordable option over the long term.
(All the benefits of hydropower)

Emissions-Free – Hydropower does not produce air pollutants or greenhouse gases. It utilizes flowing water to generate electricity, which does not emit anything harmful into the atmosphere. Hydropower helps keep air clean and safeguards public health.

Energy Storage Capabilities – An advantage unique to hydropower is its built-in storage capabilities at many facilities. Dams can instantly adjust output to meet demand for electricity, as well as store excess energy by pumping water uphill into reservoirs. The stored energy can then be released on demand to generate electricity later when needed.

Disadvantages of Hydropower

While hydropower provides clean, renewable energy, it also comes with some downsides. Four major disadvantages of hydropower include:

High Upfront Costs

Constructing a hydroelectric dam and power plant requires a huge upfront investment. For example, the Three Gorges Dam in China cost over $60 billion to build (https://climate.mit.edu/ask-mit/why-arent-we-looking-more-hydropower). This massive financial commitment can deter countries and investors from pursuing hydropower projects.

Impact on Fish Migration

Dams present an obstacle for migratory fish like salmon that swim upstream to spawn. Fish ladders and elevators can assist fish to get past dams, but many are still injured or killed by turbine blades (https://www.eia.gov/energyexplained/hydropower/hydropower-and-the-environment.php). This disrupts local ecosystems that depend on fish migration and population.

Habitat Destruction

The reservoirs created by hydroelectric dams cover a large area that was once natural habitat for plants and animals. The flooding of land destroys forests, wetlands, wildlife habitats, agricultural land, and scenic landscapes (https://www.usgs.gov/special-topics/water-science-school/science/hydroelectric-power-water-use). It also displaces human populations living in those areas.

Drought Risk

Hydropower relies on steady water flow, so output can decrease significantly during droughts. Lower water levels in reservoirs means less generation capacity. Droughts caused by climate change pose an increasing challenge for hydropower generation in some regions.

Small Scale and Micro Hydropower

Small scale hydropower projects generate up to 10 megawatts of electricity, while micro hydropower projects generate up to 100 kilowatts. These small-scale hydropower systems provide clean, renewable electricity often in remote areas or developing countries.

Some examples of small and micro hydropower projects include:

  • Homeowners utilizing small turbines in existing waterways or streams to generate electricity for their houses. Many micro hydropower kits are available for purchase to generate up to 1-2 kilowatts.
  • Remote villages installing micro hydropower systems that divert water from a stream to spin a turbine and generate electricity. These systems often provide the only source of power in remote mountain regions.
  • Small dams constructed on existing irrigation canals to capture energy from flowing water. The Tarbela Dam Irrigation System in Pakistan has multiple micro hydropower projects generating electricity from its canal network.

The benefits of small scale and micro hydropower, especially for developing regions, include:

  • Providing electricity access to rural or remote areas that lack grid connectivity.
  • Being cheaper and easier to construct compared to large scale dams.
  • Having a smaller environmental impact since they divert less water and inundate less land.
  • Allowing local ownership and operation of electricity generation.

With lower construction costs and smaller environmental impacts, small scale and micro hydropower can provide clean renewable electricity even in areas unsuitable for larger projects. Their decentralized nature also increases energy access and supports rural development.

Future of Hydropower

Hydropower has substantial growth potential worldwide, especially in developing countries. According to the International Energy Agency, global hydropower capacity could increase by over 200 GW between 2021-2030, with most growth occurring in Asia and South America [1]. China and India alone account for half of the global hydropower growth potential. Africa also has significant untapped resources, with less than 10% of feasible sites currently utilized [2].

Technological improvements are increasing hydropower efficiency and output. Upgrades to existing infrastructure can boost generation without requiring new dams. Innovation in materials, turbine design, and civil engineering allow new projects to maximize energy production while minimizing environmental disturbances [1].

Sustainability remains a key focus area. New run-of-river and low-impact projects aim to avoid substantial disruption to river systems. Improved environmental assessments and mitigation strategies can reduce biodiversity impacts. Multi-purpose dams that also provide flood control, irrigation, and recreation may gain wider public acceptance [2].


In summary, hydropower is an important renewable energy source with many notable examples around the world. The Hoover, Three Gorges, and Itaipu dams showcase the ability of hydropower to generate large amounts of electricity to power cities and industries. While not without downsides, the advantages of emissions-free, renewable electricity from hydropower dams have made them an integral part of the world’s energy infrastructure, especially in emerging economies.

As countries seek to reduce reliance on fossil fuels and mitigate climate change, hydropower will continue playing a major role. Improvements in turbine technology and building smaller, less environmentally disruptive dams can further increase hydropower’s importance as a clean energy source. Though not appropriate everywhere, hydropower’s flexibility and storage capacity give it a unique advantage over intermittent renewable sources like wind and solar. With more investment and innovation, hydropower can remain a key part of building a sustainable energy future.

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