Three Gorges Dam
The Three Gorges Dam is a concrete gravity dam on the Yangtze River at Sandouping near Yichang in Hubei Province, China, measuring 2,309 meters across at the crest and rising 185 meters above the riverbed.[1] Construction of the main structure began in 1994 and reached completion in 2006, with the reservoir's initial impoundment starting in 2003 and the final turbine units becoming operational by 2012, establishing it as the world's largest hydroelectric facility with an installed capacity of 22,500 megawatts from 32 main generators.[1][2] The project was engineered primarily to mitigate catastrophic flooding along the Yangtze basin, generate vast quantities of clean electricity to support China's industrialization, and enhance navigational capacity on the river by accommodating larger vessels through integrated ship locks and a ship lift.[3][1] Its operational achievements include averting severe flood damage during extreme events like the 2020 Yangtze floods by storing over 20 billion cubic meters of water, producing cumulative electricity exceeding 1.6 trillion kilowatt-hours by 2023—equivalent to displacing coal-fired generation and reducing carbon emissions—and boosting annual cargo throughput on the river to over 100 million tons.[4][1] However, the dam's construction displaced approximately 1.3 million residents from the reservoir area, necessitating large-scale resettlement that strained local resources and social structures.[5] Environmentally, it has triggered ecological disruptions such as increased landslide risks due to reservoir-induced seismicity and water level fluctuations, habitat fragmentation for aquatic species, and accumulation of silt and pollutants behind the barrier, though proponents argue these are offset by downstream sediment management and biodiversity protections implemented post-construction.[6][7] Ongoing debates center on its long-term structural integrity amid geological stresses and the net balance of benefits versus unintended consequences like altered regional hydrology and potential exacerbation of droughts.[8]History
Planning and Proposal
The concept of a dam at the Three Gorges originated with Sun Yat-sen, who in 1918 outlined the project in The Fundamentals of National Reconstruction to harness hydroelectric power for industrialization, mitigate recurrent Yangtze floods, and facilitate navigation by stabilizing river levels.[9] Early 20th-century proposals emphasized the Yangtze's engineering challenges and potential benefits, with American engineers conducting surveys in the 1920s and John L. Savage proposing in 1944 a structure yielding a 200-meter-deep reservoir and 10.65 gigawatts of capacity to address flood risks and power shortages.[10] [9] Catastrophic floods reinforced the rationale, notably the 1931 Yangtze event, regarded as one of the deadliest natural disasters with a death toll exceeding 2 million from direct inundation and associated effects, highlighting the river's historical volatility that had claimed over 300,000 lives in the 20th century alone.[11] [10] These disasters, combined with hydropower needs for economic growth and navigation upgrades to enable large oceangoing vessels far inland, drove intermittent advocacy amid civil unrest and war.[10] Post-1949, the People's Republic initiated formal studies in the 1950s, enlisting Soviet experts from 1955 for technical assessments including site surveys and design, though geopolitical shifts and resource constraints sidelined the full-scale project in favor of tributary works.[12] [13] Feasibility debates intensified in the 1970s-1980s, with economic models evaluating flood storage capacity, power output equivalent to multiple nuclear plants, and shipping efficiencies against sedimentation risks and displacement, leading to expert-led reviews that refined site-specific parameters without resolving all technical uncertainties.[10] [9]Approval and Initial Construction
In April 1992, China's National People's Congress (NPC) formally approved the "Resolution on the Construction of the Yangtze River Three Gorges Project," with 1,767 of 2,633 delegates voting in favor, 177 against, 664 abstaining, and 25 not voting—a record level of dissent reflecting internal divisions over the project's risks.[14][15] Prominent opposition came from scientists, economists, environmentalists, and journalists, including activist Dai Qing, who highlighted potential ecological damage, massive population displacement exceeding 1 million people, seismic vulnerabilities, and questionable cost-benefit economics; critics argued the NPC delegates lacked full data, leading to claims of inadequate deliberation.[16][17][18] Despite these hurdles, proponents, led by Premier Li Peng, prevailed by emphasizing flood control benefits after historical Yangtze inundations, hydropower for industrial growth, and improved navigation, framing the dam as essential for overcoming China's developmental bottlenecks amid bureaucratic and technical skepticism.[19] Funding mechanisms were established to bypass fiscal constraints, including the State Three Gorges Construction Fund launched in 1992 via special upstream electricity surcharges on consumers, supplemented by revenues from existing hydropower plants, state budget allocations, long-term construction bonds, and bank loans such as a RMB 30 billion facility from the China Development Bank in 1994; foreign financing was limited to under 10% of needs, with total project costs later audited at ¥249 billion (approximately US$37 billion).[20][21][22] These sources ensured self-reliance, though they imposed upstream economic burdens and drew criticism for opaque accounting and reliance on consumer levies without proportional benefits.[23] Preparatory site work commenced in 1993, followed by official groundbreaking on December 14, 1994, initiating access infrastructure like a 28-kilometer highway from Yichang completed by October 1997.[24][25] Initial construction focused on river diversion preparations, culminating in the erection of cofferdams and blocking of the Yangtze on November 8, 1997—attended by leaders including President Jiang Zemin—to enable dry foundation excavation amid high-flow challenges.[10][26] This phase overcame logistical barriers in the rugged terrain, prioritizing national infrastructure imperatives over lingering environmental and relocation concerns.[27]Major Construction Phases and Milestones
The initial phase of construction, spanning 1993 to November 1997, encompassed site preparation, cofferdam erection, and river diversion infrastructure to isolate the foundation area from the Yangtze's flow.[28][29] Actual groundwork began on December 14, 1994, involving excavation and foundation stabilization through grouting to secure the bedrock against seismic and hydraulic stresses.[24] This period achieved the critical milestone of Yangtze River closure on November 8, 1997, redirecting water through temporary channels and enabling dry-site foundation work, an engineering feat that minimized flood risks during peak flow seasons.[29] Subsequent phases from 1998 to 2006 concentrated on the main dam wall assembly, pouring over 28 million cubic meters of concrete into a gravity structure measuring 185 meters high and 2,309 meters long.[1] Progressive block pouring techniques allowed for thermal control and stress management in the massive pour volumes, with the final concrete placement occurring on May 20, 2006, completing the dam body one year ahead of initial projections despite logistical demands of supplying materials via rail and barge across rugged terrain.[30] Reservoir impoundment commenced in June 2003 behind the rising structure, initially raising water levels to 135 meters to test stability and integrate early power units, while staged filling mitigated downstream sedimentation buildup.[31] Key milestones included the activation of the first turbine generator in July 2003, enabling preliminary hydroelectric output amid ongoing wall elevation, and incremental impoundment to 156 meters by 2006 for flood control trials.[32] Construction faced setbacks from equipment failures, such as a 2000 conveyor collapse killing three workers, but overall fatalities totaled approximately 100 across 17 years, low relative to the mobilization of 40,000 peak personnel and the handling of 463 million cubic meters of earthworks.[33][34] These phases underscored causal engineering priorities, prioritizing sequential load-bearing integrity over accelerated timelines to avert structural vulnerabilities in the seismically active region.[35]Completion and Initial Operation
The first phase of reservoir impoundment commenced on June 1, 2003, with water levels rising to 135 meters by the end of the year, enabling initial power generation despite ongoing construction behind a temporary cofferdam.[36][27] The inaugural turbine unit connected to the national grid on July 10, 2003, marking the start of hydroelectric output at 700 MW per unit, which provided relief during the severe drought affecting the Yangtze basin that year by storing upstream water for downstream release.[37][38] The permanent dam structure reached completion in May 2006, allowing for expanded reservoir filling and the progressive installation of additional turbines.[39] Ship locks, operational since late 2003, facilitated a rapid increase in navigation capacity, transitioning the Yangtze from seasonal limitations to year-round shipping with annual cargo volumes rising from approximately 10 million tons pre-dam to over 100 million tons by the mid-2000s through the five-stage lock system.[40] Initial flood management tests during tentative operations in 2003–2006 demonstrated the reservoir's ability to attenuate peak flows, though adjustments were made to cofferdam outlets for sediment flushing and water level control amid variable inflows.[27] By 2007, nine turbines were online, contributing to power output that exceeded initial phased projections for the period, with cumulative generation reaching several tens of terawatt-hours annually as more units activated.[27] Reservoir levels advanced incrementally, hitting 156 meters in 2008 and achieving the full 175-meter elevation for the first time in October 2010, enabling optimal flood storage capacity of 22 billion cubic meters during early operational trials.[39] These phases involved refinements to turbine synchronization and spillway operations to balance power demands, navigation scheduling, and drought mitigation, setting the stage for full-scale functionality.[41] The power station attained its designed capacity of 22,500 MW on July 4, 2012, with the final left-bank turbine entering commercial service, though initial operations from 2003 onward had already integrated into China's grid, supplying electricity equivalent to reducing coal consumption by millions of tons yearly in the early years.[32][42] Early data indicated navigation throughput boosts of tenfold or more compared to pre-dam eras, driven by lock efficiency despite occasional congestion adjustments.[40]Design and Technical Specifications
Dam Composition and Dimensions
The Three Gorges Dam is constructed as a concrete gravity dam, relying on its mass to resist water pressure. The main structure reaches a maximum height of 181 meters above the foundation, with a crest elevation of 185 meters and a crest length of 2,335 meters along the river span.[4][1] The total dam axis measures 2,309.5 meters, incorporating the central spillway section and flanking non-overflow sections on the left and right banks.[1] Construction utilized 27.2 million cubic meters of concrete for the dam body and associated structures, forming large blocks poured in controlled sequences to manage thermal stresses. Approximately 463,000 tonnes of steel were employed, including reinforcing bars and structural elements sufficient to construct around 63 Eiffel Towers.[43][44] The central spillway section extends 483 meters, featuring 22 surface sluice gates and 23 bottom outlets designed for high-capacity flood discharge.[45] Flanking the spillways are the riverine powerhouse at the dam toe, spanning the base, and underground powerhouse complexes embedded into the left and right bank hillsides, integrating structural reinforcement with hydraulic intake galleries. Auxiliary dams and embankments supplement the main structure to enclose the reservoir.[46][47]| Component | Key Dimensions |
|---|---|
| Main Dam Height | 181 m |
| Crest Elevation | 185 m |
| Crest Length | 2,335 m |
| Concrete Volume | 27.2 million m³ |
| Steel Usage | 463,000 tonnes |
| Spillway Length | 483 m |