Science and Nature

Today, hydropower is the most widely used form of renewable energy, but still accounts for only 16 percent of global electricity generation. Lack of accessible water sources is one of the main reasons why hydropower is lagging behind alternatives such as fossil fuels and nuclear power. But this is expected to change in the next few decades as several major hydroelectric projects are underway mostly in the Asia-Pacific region, that already generates 32 percent of global hydropower. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. Paraguay produces 100% of its electricity from hydroelectric dams, and Norway 98–99%. Brazil, Canada, New Zealand, Austria, Switzerland, and Venezuela – all have a majority of the internal electric energy production from hydroelectric power.

Three Gorges Dam, China
The Three Gorges Dam that spans the Yangtze River in Hubei province, China, is the world’s largest power station in terms of installed capacity (22,500 MW). Made of concrete and steel, the dam is 2,335 meters long and 181 meters tall. More than 102.6 million cubic meters of earth was moved to make way for 27.2 million cubic meters of concrete and 463,000 tonnes of steel, enough to build 63 Eiffel Towers. It cost the state US$ 22.5 billion to build the dam.
When the water level is at its maximum of 175 meters above sea level, which is 110 meters higher than the river level downstream, the dam reservoir is on average about 660 kilometers in length and 1.12 kilometers in width, giving it an effective capacity of 39.3 km3 and 1,045 square kilometers of surface area.
The Chinese government takes huge pride in the project, in its state-of-the-art large turbines, and its move toward limiting greenhouse gas emissions, even though it displaced some 1.3 million people, causing significant ecological changes as well as controversy both domestically and abroad.

Itaipu Dam, Brazil and Paraguay
The Itaipu Dam is located on the Paraná River on the border between Brazil and Paraguay. Although the dam has a capacity of 14,000 MW, lower than that of the Three Gorges Dam, it has a higher annual yield generating an average of 91 ~ 95 TWh in comparison to 80 TWh by the latter. The plant supplies 90% of the electricity consumed by Paraguay and 19% of that consumed by Brazil.
The Itaipu Dam is actually four dams joined together — from the far left, an earth fill dam, a rock fill dam, a concrete buttress main dam, and a concrete wing dam to the right, giving it a total length of 7235 meters. To build this massive structure, the course of the seventh biggest river in the world had to be altered, and 50 million tons of earth and rock had to moved. To give you an idea, the amount of concrete used to build the Itaipu Power Plant would be enough to build 210 football stadiums; the iron and steel used would allow for the construction of 380 Eiffel Towers and the volume of excavation of earth and rock in Itaipu is 8.5 times greater than that of the Channel Tunnel.

Guri Dam, Venezuela
The Guri Dam is 7,426 meters long and 162 meters high and is located in Venezuela on the Caroni River. As of 2009, the hydroelectric plant is the third-largest in the world, with 10,235 MW capacity and eighth-largest by volume of water. The Guri Dam alone supplies 73% of Venezuela’s electricity.
The dam has been the source of controversy for a long time because the lake it created flooded some 4,250 square km of a forest that was renowned for its biodiversity and rare wildlife, including the only place where the recently discovered Carrizal Seedeater (a finch-like tanager) was ever found.

Tucuruí Dam, Brazil
The Tucuruí Dam is a concrete gravity dam on the Tocantins River located on the Tucuruí County in Brazil. The main portion Tucuruí Dam is 78 meters high and 6.9 km long and made of concrete. The addition of the Mojú and Caraipé earth-fill dikes increases the total length to 12,515 m. The reservoir impounded by the dam has a capacity of 45 km³ with a live volume of 32 km³. The main dam’s Creager-type service spillway is the second largest in the world with a maximum capacity of 110,000 m³/sec. The dam is also used for navigation between the upper and lower Tocantins River.
The Tucuruí Dam brings power to 13 million people and 60% of the power is transferred to industries which create just under 2,000 jobs. But construction of the dam attracted large number of migrants to the area leading to deforestation and negative impacts from increased cattle-raising. The dam also displaced between 25,000 and 35,000 people in the early 1980s, out of which 3,750 people returned to live in the new islands created by the reservoir.

Grand Coulee Dam, the U.S.
Grand Coulee Dam is a gravity dam on the Columbia River in the U.S. state of Washington built to produce hydroelectric power and provide irrigation. It was constructed between 1933 and 1942, originally with two power plants. A third power station was completed in 1974 to increase its energy production. It is the largest electric power-producing facility in the United States and one of the largest concrete structures in the world. Through a series of upgrades and the installation of pump-generators, the dam now supplies four power stations with an installed capacity of 6,809 MW. The reservoir supplies water for the irrigation of 671,000 acres.

Sayano–Shushenskaya Dam, Russia
The Sayano–Shushenskaya Dam is located on the Yenisei River, near Sayanogorsk in Khakassia, Russia. It is the largest power plant in Russia and the sixth-largest hydroelectric plant in the world, by average power generation. The dam is constructed to “safely” withstand earthquakes up to 8 on the Richter scale, and was recorded by the Guinness Book of World Records for the strongest construction of its type.

Longtan Dam, China
Longtan Dam is located on the Hongshui River in Tian’e County in China. The dam is 216.2 meters high and 849 meters long, and is the tallest “roller-compacted concrete (RCC) gravity dam” in the world.