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| Fig. 1: The Three Gorges Dam under construction in 2009. (Source: Wikimedia Commons) |
The Three Gorges Dam in Hubei province, China (Fig. 1) is the largest hydroelectricity dam in the world by far. Spanning more than 2.3 kilometers across the Yangtze River, the third longest river in the world, the dam is 181 meters in height and can hold more than 39 billion cubic-meters (roughly 10 trillion gallons) of water. [1] Construction of the dam began in late 1994, and the dam body was completed in 2006 (shown on the right), though the last generator was not installed until 2012. After its completion, the installed capacity of Three Gorges Dam reached 22,500 MW, 1.6 times of the world's second-largest hydroelectric power stations, the Itaipu Dam between Brazil and Paraguay.
To achieve the 22,500 MW capacity, there are 32 main water turbines installed at the plant (14 on the north side, 12 on the south side, and 6 on the south side underground), each rated at 700 MW; there are two smaller generators each of 50 MW to power the plant operation. While the actual amount of electricity generated by the plant depends on the precipitation of the year, in 2020, due to the extra precipitation brought by the unusually strong monsoon season, the annual production reached 111.8 TWh, beating the record of 103 TWh set by the Itaipu Dam in 2016. According to BP, China generated 7779 TWh of electricity in 2020, and Three Gorges Dam accounted for ~1.43% of the total. [2] Considering the main source of electricity generation in China is still fossil fuel (coal, in particular), this can still reap considerable environmental benefits. According to the EIA, generating 1 kWh of electricity in US in 2021 uses 1.12 pounds of coal (0.89 lbs kWh-1). [3] To replace Three Gorges Dam, China would need to burn approimately
or 5.68 × 1010 kg of extra coal. Nevertheless, compared to the original expectation of Three Gorges Dam being able to supply 10% of China's electricity, the actual percentage seems rather modest, mostly due to how fast China's electricity consumption has grown.
Furthermore, like many other rivers that pass through densely populated regions, Yangtze River has certainly had its fair share of floods throughout the history. Because of the river's facilitation of trade in the history, Yangtze River flows by or flows right through a number of important cities like Shanghai and Nanjing, where millions of people reside and are home to many important industrial facilities. Thus, another important function of the dam is to regulate the seasonal variations of Yangtze's water flow. In 1998, prior to the dam's completion, a flood impacted multiple regions downstream of the Yangtze River, killed ~4000 people, flooded 2039 squared-kilometers of farmland, and resulted billions of dollars in damages. [4] With the dam's completion, the water output to downstream can be effectively regulated by storing more upstream water in its reservoir. Similarly, during dry seasons, the dam can also increase its outflow to provide more freshwater to downstream cities.
Because of the mountain terrains in western China, a considerable portion of China's planned renewable energy is through hydroelectricity, by harvesting the gravitational potential energy in the rivers. Sichuan is one of the biggest provinces building out hydroelectricity power stations. It alone accounts for 30% of China's hydropower. In fact, nearly 80% of the province's electricity comes from hydropower, whereas coal only accounts for 16%. [5] In 2022, because of the fluctuations in precipitation (60% less year-over-year in August) and the extreme heat, Sichuan's grid actually became very constrained as hydroelectricity stations output decreased but electricity demand went up by 25% year-over-year, which has led the provincial and the central government of China to rethink its ambitious expansion of renewable energy. [5,6] A report estimates that China uses 500 TWh for air conditioning in 2022, about 6.5% of the country's total generation. [7]
A small note about the situation in Sichuan: there have been numerous news reports in 2021 about some hydroelectricity stations in Sichuan were quietly selling some off-the-grid electricity to bitcoin and other cryptocurrency miners since precipitation was abundant. [8] Thus the figures above about the actual hydropower installed capacity may still be underestimated.
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| Fig. 2: Satellite maps showing the Three Gorges reservoir area being flooded. (Source: Wikimedia Commons) |
Many studies and reports have pointed out that building out the Three Gorges Dam and its reservoir took a hard toll on the environment. After the dam's completion, the water level in the reservoir's region rose by about 175 meters. As can be seen from Fig. 2, a considerable portion of the previous land is now submerged under water. This eliminated the natural habitat of many species and further increased the isolation between different species. Furthermore, by creating a hard barrier on the river stream, this effectively blocked the migration for many fish species, leading to a dramatic decrease in the count of Chinese sturgeon and the (possible) extinction of Baiji (white river dolphin). [1,9]
Furthermore, during the construction, at least 1.4 million people were displaced or relocated. Many people have also been forced to find new jobs despite their lack of skills other than farming. While the official cost figure was said to be $23 billion, outside experts have estimated as much as twice of that amount. Many have also raised concerns about holding this massive body of water would induce risk of earthquakes and landslides. Some have speculated that this may have caused the massive earthquake in May 2008 in Sichuan. [10] While forest cover in the area has also dropped substantially during its construction, a large portion has been restored due to China's reforestation effort. [11,12]
There has been much controversy over Three Gorges Dam to this date. We cannot deny there have been a lot of benefits as well as negative consequences as a part of this project. While certain environmental impacts were definitely overlooked or purposefully ignored at the time, the success of this project has also motivated China to invest more in hydropower and other types of renewable energy, establishing itself as one of the leaders in that domain.
© Xuelin Yang. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] J. Wu et al., "Three-Gorges Dam - Experiment in Habitat Fragmentation?" Science 300, 1239 (2003).
[2] "BP Statistical Review of World Energy 2021," British Petroleum, June 2021.
[3] "Electric Power Annual 2021," U.S. Energy Information Administration, November 2022.
[4] Q. Ye and M. Glantz, "The 1998 Yangtze Floods: The Use of Short-Term Forecasts in the Context of Seasonal to Interannual Water Resource Management," Mitig. Adapt. Strateg. Glob. Change 10, 159 (2005).
[5] M. Xu and D. Stanway, "Explainer: The Power Crunch in China's Sichuan and Why It Matters", Reuters, 25 Aug 22.
[6] E. Downie, "China Had Another Hot Summer and Another Electricity Crisis," Washington Post, 2 Sep 22.
[7] "The Future of Cooling in China," International Energy Agency, June 2019.
[8] S. Shen and A. John, "China's Cryptocurrency-Mining Crackdown Spreads to Sichuan," Reuters, 18 Jun 21.
[9] Y. Ma, "Three Gorges Dam," Physics 240, Stanford University, Fall 2010.
[10] M. Wines, "China Admits Problems With Three Gorges Dam," New York Times, 19 May 11.
[11] J. Hui, "Water Pollution in the Three Gorges Reservoir," in The River Dragon Has Come: Three Gorges Dam and the Fate of China's Yangtze River and Its People, ed. by Q. Dai, (Routledge, 1998).
[12] R. Shi, "Ecological Environment Problems of the Three Gorges Reservoir Area and Countermeasures," Procedia Environ. Sci. 10B, Part B, 1431 (2011).
