Cluster 1 · What it is
Three Gorges Dam — the key facts
Three Gorges Dam is the world's largest power station — not just the largest hydroelectric dam, but the largest any-type power station ever built, by both installed capacity (22,500 MW) and annual electricity generation (88–100 TWh). It sits across the Yangtze River in central China, where the river cuts through three dramatic gorges before reaching the plains. The dam is 185 metres tall and 2.3 kilometres long. Its reservoir stretches 660 kilometres upstream — far enough to fill a lake the length of England. Began generating power in 2003; fully commissioned in 2012. Built by China Three Gorges Corporation, owned by the Chinese government.
Technical specifications:
Turbines: 32 × 700 MW Francis turbines (26 on the left and right banks, 6 underground) + 2 × 50 MW plant-use turbines = 22,500 MW total.
Generators: Each 700 MW unit weighs approximately 6,000 tonnes. Rotor diameter: ~18 metres. The generator hall is longer than the Eiffel Tower laid on its side.
Operating head: 61–113 metres (varies with reservoir level). Designed head: 80.6 m.
Turbine type: Francis — the most common type for medium-to-high head, high-flow applications.
Annual generation: 88–102 TWh depending on Yangtze rainfall — in wet years exceeds 100 TWh, equivalent to the entire annual electricity production of Portugal.
Turbines: 32 × 700 MW Francis turbines (26 on the left and right banks, 6 underground) + 2 × 50 MW plant-use turbines = 22,500 MW total.
Generators: Each 700 MW unit weighs approximately 6,000 tonnes. Rotor diameter: ~18 metres. The generator hall is longer than the Eiffel Tower laid on its side.
Operating head: 61–113 metres (varies with reservoir level). Designed head: 80.6 m.
Turbine type: Francis — the most common type for medium-to-high head, high-flow applications.
Annual generation: 88–102 TWh depending on Yangtze rainfall — in wet years exceeds 100 TWh, equivalent to the entire annual electricity production of Portugal.
Source: China Three Gorges Corporation · IHA World Hydropower Outlook
Power output formula: P = η × ρ × g × Q × H. At design point: η=93%, ρ=1,000 kg/m³, g=9.81 m/s², Q=966 m³/s per turbine, H=80.6 m → P = 0.93 × 1,000 × 9.81 × 966 × 80.6 = 712 MW per turbine (slightly above nameplate due to head variability). The 32 × 700 MW units total 22,400 MW (nameplate), with 2 × 50 MW plant-use units totalling 22,500 MW. The reservoir stores 39.3 km³ of water — providing approximately 22 days of flood control buffer for downstream cities. The Three Gorges Dam reduced Yangtze flood risk from a 10-year return period flood causing major damage to a 100-year return period event threshold before major damage. Sedimentation: The Yangtze carries approximately 520 million tonnes of sediment annually. The dam traps ~90% of this upstream, causing riverbed erosion downstream, reduced agricultural nutrient delivery to coastal plains, and erosion at the Yangtze delta (Shanghai region). This is the primary ongoing environmental concern.
Source: China Three Gorges Corporation technical reports · IHA · World Bank Yangtze River studies
Cluster 5 · What it cost and who was displaced
The human and environmental cost — documented
Resettlement — 1.4 million people
The Three Gorges reservoir flooded 13 cities, 140 towns, and 1,350 villages. Approximately 1.4 million people were resettled — the largest forced resettlement in dam construction history. The Chinese government confirmed this figure. Resettled populations received compensation and were relocated to new towns primarily in the same region, though some were relocated to other provinces. The Three Gorges Museum in Chongqing documents the submerged cities and towns. Source: Chinese National Development and Reform Commission · World Bank
Environmental impacts — documented
Three major documented impacts: (1) Yangtze finless porpoise: listed as critically endangered (IUCN), habitat disrupted by dam construction and reservoir; (2) Sediment trapping: dam blocks ~90% of Yangtze's 520 MT/year sediment, causing downstream erosion and reducing soil fertility; (3) Seismic risk: water weight of 39.3 km³ of reservoir water has been associated with increased local seismic activity in the reservoir area. These impacts are documented by Chinese government agencies and international bodies including IUCN. Source: IUCN · China Three Gorges Corporation Environmental Reports · Nature journal
Scale in context
What 88–100 TWh/year means
Scale comparison
Three Gorges' annual generation of 88–100 TWh/year is equivalent to:
— The entire annual electricity production of Portugal (~50 TWh) × 2
— Powering approximately 60–70 million average Chinese urban households
— Avoiding approximately 50 million tonnes of CO₂/year that would otherwise come from coal power (at 820 g/kWh)
— Supplying approximately 3% of China's total electricity consumption (~9,000 TWh/year)
Despite being the world's single largest power station, Three Gorges supplies only 3% of China's electricity — illustrating the scale of China's total energy consumption. Source: China Three Gorges Corporation · IEA China data
— The entire annual electricity production of Portugal (~50 TWh) × 2
— Powering approximately 60–70 million average Chinese urban households
— Avoiding approximately 50 million tonnes of CO₂/year that would otherwise come from coal power (at 820 g/kWh)
— Supplying approximately 3% of China's total electricity consumption (~9,000 TWh/year)
Despite being the world's single largest power station, Three Gorges supplies only 3% of China's electricity — illustrating the scale of China's total energy consumption. Source: China Three Gorges Corporation · IEA China data
Questions
How did China decide to build Three Gorges Dam?
The Three Gorges Dam concept dates to Sun Yat-sen's 1919 proposal. After the catastrophic 1954 Yangtze flood (killed ~33,000 people) and 1975 Banqiao Dam collapse (killed 26,000–170,000 people), flood control became a national priority. The National People's Congress approved the project in (1,767 for, 177 against, 664 abstentions — one of the most contested votes in its history, reflecting unusual public debate). Construction began 1994. The primary justification: simultaneous flood control, navigation improvement (raising water level makes the Yangtze navigable to large ships 600 km further upstream to Chongqing), and electricity generation. Source: Chinese National People's Congress records · Probe International dam studies.
Source: Chinese NPC Historical Records · Probe International Three Gorges Dam Study
Is Three Gorges Dam at risk of collapse?
No credible engineering assessment suggests Three Gorges Dam is at imminent collapse risk. The dam is a gravity dam — concrete held in place by its own weight — and was designed to withstand a Probable Maximum Flood (PMF). Concerns occasionally circulate online, often based on satellite imagery showing the curved appearance of the dam in wide-angle lenses (an optical distortion, not structural deformation). China Three Gorges Corporation publishes structural monitoring data regularly. The dam underwent its first full capacity test (reservoir at 175m) in 2010. Independent engineering assessments from international dam safety bodies have not raised structural concerns. The legitimate concerns about Three Gorges relate to seismic risk (reservoir-induced seismicity) and the consequences if a flood overtops it — both managed through strict reservoir management protocols. Source: China Three Gorges Corporation Safety Reports · ICOLD (International Commission on Large Dams).
Source: China Three Gorges Corporation structural monitoring · ICOLD dam safety standards
How does Three Gorges compare to India's largest power stations?
Three Gorges (22,500 MW) is the world's largest power station — roughly five times India's largest single power station (Vindhyachal STPS, 4,760 MW, operated by NTPC in Madhya Pradesh). India's total installed electricity capacity is approximately 250 GW — Three Gorges alone represents approximately 9% of that. For context: India's entire hydro fleet is approximately 47 GW; Three Gorges alone nearly equals half of India's entire hydro sector. The fundamental geographic difference: the Yangtze River's vast catchment and the Three Gorges gorge's natural dam site have no equivalent in India. India's largest single planned hydro project (Dibang, Arunachal Pradesh, ~2,880 MW) is 12.8% the size of Three Gorges. Source: CEA India · China Three Gorges Corporation.
Source: CEA India 2024 · China Three Gorges Corporation Annual Report · NHPC India
What was the controversy around building Three Gorges Dam?
Three Gorges Dam is one of the most controversial infrastructure projects in history. The National People's Congress vote to approve it (1,767 for, 177 against, 664 abstentions) was remarkably contested for a Chinese government project — reflecting unusual public debate. The main controversies: (1) The resettlement of approximately 1.4 million people — critics documented inadequate compensation, psychological trauma, and economic marginalisation of relocated communities; (2) Submersion of approximately 1,300 archaeological sites; (3) Destruction of unique Yangtze River ecosystems including the likely extinction of the baiji (Yangtze river dolphin, last reliably sighted 2004) and near-extinction of the Yangtze finless porpoise; (4) Geological instability — the reservoir has been associated with increased landslide frequency; (5) Sediment trapping — reducing agricultural fertility downstream and accelerating Yangtze Delta erosion. Engineers and economists from Probe International documented many of these concerns in advance. Source: Probe International · IUCN · NPC historical records.
Source: Probe International Three Gorges Report · IUCN Red List · Chinese NPC 1992 vote records
How much CO₂ does Three Gorges avoid each year?
Three Gorges generates approximately 88–102 TWh/year. If this electricity were instead generated by coal (China's marginal generation source, at approximately 820 g CO₂/kWh), it would emit approximately 72–84 million tonnes of CO₂ per year. China Three Gorges Corporation quotes approximately 50 million tonnes of CO₂ avoided per year — a more conservative estimate accounting for different reference scenarios and reservoir methane emissions. For context: 50 million tonnes CO₂/year is equivalent to taking approximately 25 million cars off the road. The IPCC AR6 lifecycle emissions for reservoir hydropower are approximately 24 g CO₂eq/kWh median (but with a range of 4–306 g/kWh depending on reservoir methane emissions — tropical reservoirs can be significantly higher). Source: China Three Gorges Corporation · IPCC AR6 WG3.
Source: China Three Gorges Corporation · IPCC AR6 WG3 Annex II
What comes after Three Gorges — is China building more mega-dams?
Yes — China is building the Baihetan Dam on the Jinsha River (Sichuan/Yunnan border, 27.22°N 102.89°E), which at 16,000 MW is the world's second-largest hydropower station, surpassing Itaipu. Baihetan started generating power in 2021 and reached full capacity in 2022. The Wudongde Dam (upstream, 10,200 MW) reached full operation in 2021. Together, these four dams on the Yangtze and its Jinsha tributary — Three Gorges, Gezhouba, Baihetan, Wudongde — form an integrated cascade system with combined capacity exceeding 60,000 MW. China's total hydropower capacity reached approximately 420 GW in 2023 — the world's largest by a wide margin. China's next major development is hydropower in Tibet and Yunnan. Source: China Three Gorges Corporation · IHA World Hydropower Outlook 2024.
Source: China Three Gorges Corporation Baihetan documentation · IHA World Hydropower Outlook 2024
China Three Gorges CorpProject data · Annual generation reports · Environmental reportsctgpc.com.cn
IHAInternational Hydropower Association · World Hydropower Outlookhydropower.org
GEM Hydro TrackerGlobal Hydropower Tracker · GPS, capacity · CC BY 4.0globalenergymonitor.org/hydro-tracker
IUCNYangtze finless porpoise · Baiji extinction · Red List dataiucnredlist.org