Rio needs 30 percent more power for the upcoming Summer Olympics and World Cup. Hydroelectricity supplies 90 percent of Brazil’s fledgling 1,500-mile grid, but tapping the city’s nearest source of water would have required building a dam that would have flooded a city of 130,000. Instead, the state utility created the world’s largest construction project. It rerouted 780 billion gallons of water through a 15-mile landscape of seven mountains
and 13 man-made channels.