Episode Details

According to NASA, the water held back by China's Three Gorges Dam lengthened the day by 0.06 microseconds and made the planet slightly rounder at the middle. The idea dates to 1919, when Sun Yat-sen proposed a dam of about 22 gigawatts in The International Development of China. The Nationalist government began preliminary work in the 1930s and brought in US Bureau of Reclamation engineer John L. Savage in 1944, but war shelved it. Mao Zedong championed it after the 1954 Yangtze floods and wrote of a great lake in the gorges in his 1956 poem Swimming. When the National People's Congress finally approved it in 1992, only 67.75 percent voted yes, with about a third of over 2,600 delegates abstaining or opposing. Construction began in December 1994.

The concrete gravity dam stands 181 meters high and over 2.3 kilometers long, with 32 main Francis turbines that produced nearly 112 terawatt hours in 2020. In the 2010 floods it absorbed a peak inflow of 70,000 cubic meters per second while releasing 40,000. Yet by 2024 it supplied under 1 percent of China's electricity. Its 600 kilometer reservoir displaced 1.13 to 1.4 million people and submerged 13 cities, 140 towns, and over 1,300 villages. A 505 million yuan salvage effort recovered over 200,000 artifacts, but many hanging coffins in the Shennong Gorge were lost, and the dam contributed to the extinction of the baiji dolphin and the Chinese paddlefish.

• How five stage locks take four hours while a counterweighted ship lift raises 3,000 ton vessels in about 40 minutes
• Shipping costs falling 25 percent and river freight capacity rising sixfold to reach Chongqing
• About 40 million tons of sediment trapped each year, starving downstream waters
• Methane from vegetation that grows on exposed banks when the reservoir drops from 175 to 145 meters, then rots underwater
• A 2004 US Defense Department report naming the dam a potential target, sparking Chinese debate over no first use nuclear policy