Short answers, pulled from the story.
Hydroelectricity supplies 15% of the world's electricity, generating almost 4,210 terawatt-hours in 2023. That figure exceeds all other renewable sources combined and also surpasses nuclear power output.
The world's first hydroelectric power scheme was developed in 1878 at Cragside in Northumberland, England, by William Armstrong. It was used to power a single arc lamp in his art gallery.
The Three Gorges Dam in China is the largest hydroelectric power station in the world, with a capacity of 22,500 megawatts. It surpassed the Itaipu Dam in 2008.
The World Commission on Dams estimated in 2000 that dams had physically displaced 40 to 80 million people worldwide. Population displacement remains one of the most significant social costs of large hydroelectric projects.
The Banqiao Dam in southern China failed during Typhoon Nina in 1975 after more than a year's worth of rain fell within 24 hours. The flood killed 26,000 people directly and another 145,000 died from subsequent epidemics, with millions left homeless.
Pumped-storage plants use surplus electricity to pump water into a higher reservoir, then release it through turbines when demand peaks. In 2021, pumped-storage schemes provided almost 85% of the world's 190 gigawatts of grid energy storage.