🏗️ Water Management: Large-Scale Strategy — Three Gorges Dam, China
The Three Gorges Dam on the Yangtze River in central China is the largest structure for generating electricity ever built. It took 20 years of construction and cost approximately $25 billion. When it was completed in 2006, it stretched 2.3 km across the river, rose 185 metres high, and created a reservoir 600 km long — roughly the distance from London to Edinburgh. It can generate 22.5 gigawatts of electricity, equivalent to burning 50 million tonnes of coal annually, supplying around 2% of China's total electricity needs. It is the boldest example of large-scale water engineering in the modern world — and the most controversial.
Why Was It Built?
The Yangtze River had killed hundreds of thousands of people in China over the 20th century. In 1931, flooding across the Yangtze basin killed between 145,000 and 400,000 people. In 1935, 142,000 died. In 1954, over 33,000. In 1998, the river flooded again, killing 3,000 directly but displacing 15 million people. The dam was, first and foremost, a flood control project — a deliberate attempt to end the cycle of catastrophic flooding that had defined life along the river for centuries.
Benefits
Flood control — the reservoir stores floodwaters during the wet season and releases them slowly; major Yangtze flooding events downstream have been significantly reduced since completion
Clean electricity — 22.5 GW of hydroelectric power replaces coal-fired generation, reducing carbon emissions by an estimated 100 million tonnes annually
Water supply — improved water flow management benefits cities downstream; water is diverted to water-scarce northern China through the South-North Water Diversion Project
Improved navigation — the reservoir calmed rapids that previously made the upper Yangtze gorges unnavigable for large vessels; freight capacity increased tenfold
Economic development — electricity supports industrialisation across central China; improved navigation boosts trade in Sichuan province
Problems
1.2 million people displaced — the reservoir flooded 13 cities, 140 towns, and over 1,300 villages. People who had lived in the Yangtze gorges for generations were relocated to new settlements, often far from their homes. Many were moved to hilly land less fertile than their original farms. Displacement caused significant social disruption and long-term economic hardship for many communities.
Cultural heritage destroyed — hundreds of archaeological sites, temples and historic structures were submerged forever. The Three Gorges region — celebrated in Chinese poetry and painting for two thousand years — now lies under water.
Sediment trapped behind dam — the Yangtze naturally carried enormous quantities of sediment to its delta and floodplain. The dam traps this sediment in the reservoir. Downstream, the river is now sediment-poor and flows faster, increasing erosion of riverbanks and the delta. The Yangtze Delta — which feeds some of China's most productive farmland — is losing land to the sea as sediment no longer replenishes it. The floodplain's fertility, dependent on annual sediment deposits, has declined.
Biodiversity collapse — the Yangtze River dolphin (baiji) was declared functionally extinct in 2007 — the first large mammal driven to extinction in modern times primarily by a river management project. The Yangtze finless porpoise is now critically endangered. Fish migration has been severely disrupted by the dam blocking the river.
Landslide risk — the weight of water in the reservoir increases pressure on surrounding slopes. Over 70 large landslides have occurred around the reservoir since filling began, killing hundreds of people and threatening the stability of reservoir shores.
Earthquake risk — the reservoir's water pressure increases stress on geological faults. The 2008 Sichuan earthquake — which killed nearly 90,000 people — occurred near the reservoir, and some seismologists believe reservoir-induced seismicity contributed to its triggering, though this remains debated.
The key exam point: large dams concentrate benefits — electricity for millions, flood protection for downstream cities, economic development — while concentrating costs on a smaller, often poorer group: those who are displaced, those whose ecology is destroyed, those who lose cultural heritage. The people who gain and the people who lose are different people. A Level 3 answer recognises and evaluates this trade-off explicitly.
