Three Gorges Dam: The World's Largest Hydroelectric Power Station

The **Three Gorges Dam** is the world's largest hydroelectric power station, with an installed capacity of **22,500 megawatts** across 32 main turbines and two smaller generators. Spanning the Yangtze River in Yichang, Hubei Province, this concrete gravity dam stretches **2,335 meters** in length and rises **185 meters** above its foundation, making it one of the most monumental engineering achievements in human history.

Introduction

Construction began in 1994 and the dam became fully operational in 2012 after nearly two decades of work. The resulting Three Gorges Reservoir extends approximately 660 kilometers upstream, fundamentally transforming the geography of the Yangtze River gorges that gave the project its name. The dam serves multiple purposes: flood control, hydroelectric power generation, and navigation improvement along one of the world's busiest inland waterways.

Engineering & Structure

• Type: Concrete gravity dam
• Height: 185 meters
• Length: 2,335 meters
• Turbines: 32 main (700 MW each) + 2 smaller (50 MW each)

The Three Gorges Dam is a concrete gravity dam, relying on its sheer mass — approximately 27.2 million cubic meters of concrete — to resist the pressure of the reservoir behind it. The dam's crest sits at 185 meters above sea level, with a normal pool level of 175 meters. The spillway can discharge floodwater at a rate of 116,000 cubic meters per second, essential for taming the Yangtze's devastating floods.

The dam includes a ship lock system with five stages, each chamber measuring 280 meters long and 35 meters wide, allowing vessels up to 10,000 tonnes to transit the dam. A ship lift capable of carrying vessels up to 3,000 tonnes was completed in 2015, reducing transit time from several hours through the locks to roughly 40 minutes.

Geographic Setting

• River: Yangtze River
• Location: Sandouping, Yichang, Hubei Province, China
• Coordinates: 30.82°N, 111.00°E
• Reservoir Length: ~660 km

The dam sits at Sandouping in the Xiling Gorge, the easternmost of the three famous gorges that carve through the Wu Mountains of central China. The Yangtze River, at 6,300 kilometers the longest river in Asia and third-longest in the world, drains a basin of 1.8 million square kilometers before passing through the dam on its way to the East China Sea.

The Three Gorges Reservoir extends upstream to Chongqing, one of China's largest municipalities. The reservoir flooded portions of the spectacular limestone gorges — Qutang, Wu, and Xiling — that have inspired Chinese art and poetry for millennia. Water levels fluctuate seasonally between 145 and 175 meters as the reservoir stores monsoon floodwaters and releases them during the dry season.

Hydroelectric Power

• Installed Capacity: 22,500 MW
• Annual Output: ~101.6 TWh (2020 record)
• Transmission: Central and eastern China via UHVDC lines

The Three Gorges Dam's 22,500 MW of installed capacity made it the world's largest power station by capacity when it surpassed the Itaipu Dam in 2012. In 2020, the dam set a world record by generating 101.6 terawatt-hours of electricity, enough to power roughly 80 million average Chinese households for a year. Each of the 32 main turbines is rated at 700 MW, among the largest ever manufactured.

Electricity from the dam is transmitted via ultra-high-voltage direct current (UHVDC) lines to load centers in Shanghai, Guangdong, and other eastern provinces, spanning distances exceeding 1,000 kilometers. The dam's output displaces an estimated 49 million tonnes of coal annually and reduces China's carbon dioxide emissions by roughly 100 million tonnes per year compared to equivalent coal-fired generation.

Environmental & Social Impact

• People Relocated: ~1.3 million
• Area Flooded: ~632 km²
• Species Affected: Chinese paddlefish (extinct), Yangtze finless porpoise (endangered)

The creation of the Three Gorges Reservoir required the relocation of approximately 1.3 million people from 1,600 settlements, factories, and towns — one of the largest mass resettlements in history. Entire cities, including much of old Fengdu and Wanzhou, were submerged, and residents were moved to newly built towns on higher ground or resettled in distant provinces.

Environmentally, the dam has disrupted the Yangtze's sediment transport, trapping an estimated 60 percent of the river's sediment load behind the dam wall. This has caused erosion of downstream riverbanks and the shrinking of the Yangtze Delta. The reservoir inundated critical habitat, and the Chinese paddlefish, once one of the world's largest freshwater fish, was declared extinct in 2022 partly due to habitat fragmentation caused by the dam and other barriers along the Yangtze.

Key Facts

• The Three Gorges Dam has an installed capacity of 22,500 MW, making it the world's largest hydroelectric power station.
• The dam's reservoir extends approximately 660 km upstream to Chongqing.
• Roughly 1.3 million people were relocated to make way for the reservoir.
• The dam required 27.2 million cubic meters of concrete to build.
• In 2020, it set a world record by generating 101.6 TWh of electricity.

Fun Facts

• The mass of the Three Gorges Dam's reservoir water is so enormous that NASA scientists calculated it slightly slows Earth's rotation and shifts the position of the poles.
• The dam's ship lift can raise a 3,000-tonne vessel 113 meters in about 40 minutes — like an elevator for boats.
• The Three Gorges area was once home to the Ba people, an ancient civilization whose artifacts were discovered during construction.

Final Thoughts

The Three Gorges Dam represents both the pinnacle of hydroelectric engineering and a cautionary tale about the environmental and social costs of mega-infrastructure. As the world's largest power station, it remains central to China's energy strategy, even as its ecological impacts on the Yangtze River basin continue to unfold.