What Are The Biggest Hydropower Projects?

What are the biggest hydropower projects?

Hydropower is the process of generating electricity by using the energy from moving water. Hydropower projects utilize dams and turbines to convert the kinetic energy from flowing water into mechanical energy, which powers the turbines to generate electricity.

Large hydropower projects are defined as dams that have an electricity generating capacity of more than 30 megawatts. These large-scale projects allow for the production of significant amounts of renewable power. According to the U.S. Department of Energy, hydropower is the largest source of renewable electricity in the United States, accounting for over 6% of total U.S. electricity generation and 41% of electricity generation from renewables.

Some key benefits of large hydropower projects include:

  • Clean renewable energy production on a large scale
  • Energy storage capabilities by using dams as a battery to even out electricity supply
  • Ability to quickly adjust electricity output to meet demand
  • Flood control and water supply benefits from reservoirs
  • Recreational opportunities such as boating, swimming, and fishing




History of Large Hydropower Projects

The history of large hydropower projects dates back to the early 20th century with the construction of massive dams and reservoirs around the world. Some of the earliest large-scale hydropower projects include the Hoover Dam in the United States, completed in 1936, and the Tennessee Valley Authority system of 29 hydroelectric dams built in the southeastern US from 1933 to 1979.[1] These ambitious infrastructure projects aimed to provide electricity, control flooding, and spur economic growth and development.

In the post-World War II era, there was a major global boom in dam construction for hydropower and other purposes like irrigation. Developing countries invested heavily in massive hydro projects as a way to boost electricity access and support rapid industrialization. Some of the most notable projects from this period include the Kariba Dam on the Zambezi River between Zambia and Zimbabwe, completed in 1959, and Brazil’s Itaipu Dam, which was the world’s largest power facility upon completion in 1984.[1]

By the late 20th century, large hydro accounted for over 30% of global power capacity as these megaprojects proliferated around the world, especially in developing countries. However, rising concerns over environmental impacts and controversies over large dam projects have slowed growth in recent decades. Nonetheless, large hydro remains an important electricity source today, supplying about 16% of the world’s power. [1]

Largest Hydropower Projects by Generation Capacity

The largest hydropower projects in the world are ranked by their generation capacity in megawatts (MW). Here are some of the biggest hydropower dams globally based on installed capacity:

1. Three Gorges Dam, China – 22,500 MW

The Three Gorges Dam on the Yangtze River in China is the world’s largest power station in terms of installed capacity at 22,500 MW. Construction was completed in 2006.

2. Itaipu Dam, Brazil/Paraguay – 14,000 MW

The Itaipu Dam on the Paraná River bordering Brazil and Paraguay has an installed capacity of 14,000 MW, completed in 1991. It supplies 17% of Brazil’s electricity.

3. Xiluodu Dam, China – 13,860 MW

With an installed capacity of 13,860 MW, the Xiluodu Dam on the Jinsha River in China ranks third globally. It began operating in 2014.

4. Guri Dam, Venezuela – 10,235 MW

The Guri Dam in Venezuela on the Caroni River was completed in 1986 and has a generation capacity of 10,235 MW.

5. Tucuruí Dam, Brazil – 8,370 MW

Located on the Tocantins River in Brazil, the Tucuruí Dam was finished in 1984 with 8,370 MW capacity, making it Brazil’s second largest hydroelectric dam.

Largest Hydropower Projects by Structure Volume

The largest hydropower dams in the world ranked by volume of structure are:

1. Three Gorges Dam, China – The Three Gorges Dam on the Yangtze River in China is the largest hydropower project in the world by structure volume at 39.3 million m3. Construction was completed in 2006.

2. Tarbela Dam, Pakistan – The Tarbela Dam on the Indus River in Pakistan has a total structural volume of 33.14 million m3. Completed in 1976, it was the largest earth and rockfill dam in the world at the time.

3. Fort Peck Dam, United States – Located in northeast Montana on the Missouri river, the Fort Peck Dam has a structure volume of 26.8 million m3. Built by the Army Corps of Engineers, it was completed in 1940.

4. Ataturk Dam, Turkey – With a structural volume of 24.5 million m3, the Ataturk Dam on the Euphrates River in southeastern Turkey ranks as one of the largest embankment dams in the world.

5. Guri Dam, Venezuela – The massive Guri hydroelectric power project on Venezuela’s Caroni River has a structural volume of 21 million m3, making it one of the largest dams in South America.

Other noteworthy massive hydropower dams by structure volume include the Grande Dixence Dam in Switzerland, the Mica Dam in Canada, and the Tucurui Dam in Brazil, each with volumes over 15 million m3.

Largest Hydropower Projects by Reservoir Size

When ranking hydropower projects by size, the massive reservoirs they create are an impressive indicator. Here are some of the largest reservoirs created by hydro dams:

1. Lake Kariba, Zambia/Zimbabwe on the Zambezi River – Formed by the Kariba Dam, Lake Kariba is the largest reservoir in the world at 5,580 km2. Its volume is over 180 km3.

2. Bratsk Reservoir, Russia on the Angara River – The reservoir for the Bratsk Dam is the 2nd largest in the world at 5,470 km2. Its volume is over 169 km3.

3. Lake Volta, Ghana on the Volta River – With a surface area of 8,502 km2 and volume of about 148 km3, Lake Volta behind the Akosombo Dam is 3rd.

4. Lake Nasser, Egypt on the Nile River – The reservoir formed by the Aswan High Dam is one of the largest man-made lakes, with a surface area of 5,250 km2 and volume of 132 km3.

5. Kuybyshev Reservoir, Russia on the Volga River – At 6,450 km2 in size, this is the largest reservoir in Europe behind the Kuybyshev Dam. It has a volume of around 58 km3.

The enormous size of these reservoirs highlights the incredible scale of large hydro projects and their ability to vastly transform landscapes and river systems.

Technical Feats of Large Hydropower

Some of the largest hydropower projects ever built have incredible engineering accomplishments. The Hoover Dam, completed in 1936, was an engineering marvel as the largest hydroelectric power station in the world at the time. At 726 feet tall, it was the tallest concrete arch dam in the US for decades (History of Hydropower).

The Three Gorges Dam in China, completed in 2006, set records as the world’s largest power station in terms of installed capacity at 22,500 MW. The dam itself stands at 185 meters tall and 2,335 meters wide (60 most influential people in the industry).

The Grand Coulee Dam, built between 1933 and 1942, was the largest electric power producing facility in the United States for multiple decades. With a capacity of 6,809 MW, it still ranks in the top 10 largest hydroelectric facilities in the country today (The Six Biggest Hydroelectric Plants in America).

These massive projects demonstrate the incredible scale and capacity that can be achieved through hydroelectric engineering. Their construction was only made possible through innovative techniques and designs.

Environmental and Social Impacts

Large hydropower projects often come with major environmental and social consequences. Damming rivers and flooding valleys disrupts ecosystems, alters natural water flows, blocks fish migration routes and impacts biodiversity. According to one report, large dams have led to the extinction of some freshwater fish species and the population decline of many others (source). Reservoirs also increase waterborne diseases like malaria and schistosomiasis. Large reservoirs can displace millions of people from their homes and land. For example, the Three Gorges Dam in China displaced over 1.4 million people (source). Dams and reservoirs significantly alter downstream flows, negatively impacting floodplain ecosystems, agriculture and livelihoods. Sediment buildup behind dams also robs nutrients from downstream soils. Some argue large hydropower projects fail to account for long-term environmental and social costs (source). More research is needed to better understand these complex impacts.

Costs and Benefits

Large hydropower projects come with both costs and benefits that must be carefully weighed. The major costs include:

  • High upfront construction costs, often billions of dollars
  • Displacement of communities and loss of land that is flooded
  • Negative impacts on the local environment and ecosystems
  • Methane emissions from the decomposition of flooded vegetation
  • Siltation buildup over time that reduces reservoir capacity

On the benefits side, large dams provide:

  • Massive electricity generation capacity to power industries and cities
  • Flood control by regulating river flows
  • Water storage for irrigation and drinking water
  • Reservoirs for recreation, transportation, and fish habitat
  • Jobs and economic stimulus during construction

Proponents argue large dams provide clean, renewable power that spurs development, while opponents believe the environmental and social costs often outweigh the benefits. Careful planning and impact assessments are crucial to determine if a mega dam project is appropriate for a given region’s needs.

Controversial Large Dam Projects

Many large hydropower projects have faced major opposition and controversies due to their significant environmental and social impacts. Some examples of controversial large dam projects include:

The Three Gorges Dam in China, which displaced over 1 million people and submerged numerous cities, archeological sites and cultural relics. There were concerns about the ecological impacts on the Yangtze River as well as geological impacts like increased risk of earthquakes. [1]

The Ilisu Dam project in Turkey, which would have displaced up to 78,000 people and flooded hundreds of sites of archeological significance. The project faced opposition over inadequate resettlement plans and lack of transparency. [2]

The HidroAysén dam project in Chile, which aimed to build five large dams in the remote Patagonia region. There was strong public opposition over the environmental impacts and threats to wilderness areas. The project was later cancelled after years of controversy. [3]

Future of Large Hydropower

The future of large hydropower projects is uncertain due to rising sustainability concerns. Large dams have major environmental and social impacts that have prompted increased opposition in recent decades (https://sandrp.in/2023/04/03/). Many believe large hydro projects are no longer sustainable or socially responsible (https://www.researchgate.net/publication/283442367_Hydropower_plants_price_and_prejudice).

Global trends show a slowdown in the number and scale of new big dam projects. According to the International Renewable Energy Agency, 2021 set a record for new renewable energy capacity added globally, yet the hydropower sector saw its lowest growth in the past two decades. The agency predicts slower growth for hydropower going forward compared to other renewables like solar and wind power (https://sandrp.in/2023/04/03/).

Developing mega hydropower projects often involves long lead times of 5-10 years and massive upfront investments. This makes large dams less attractive compared to faster and cheaper renewable energy options. Many developed countries have already tapped most of their viable large hydro resources. Developing countries still have potential for big hydro expansion but face rising environmental standards and opposition from local communities.

The future of large dams will depend on successfully addressing sustainability challenges around biodiversity loss, deforestation, displacement of communities, and managing downstream flow impacts. New large hydro projects may only be feasible if they can demonstrate robust environmental and social safeguards through comprehensive impact assessments and mitigation plans.

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