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Ageing dams, droughts and floods strain the world’s oldest clean-energy source.

Global Hydropower Faces Rising Uncertainty as Climate Extremes Undermine Reliability.

Hydropower—long considered the world’s most dependable clean-energy source—is becoming increasingly unreliable as climate extremes intensify and ageing dams struggle to cope. Brazil’s Tucuruí Dam, one of the world’s largest hydro plants, shows visible signs of stress from drought, heavy rainfall and four decades of operation. Brazil’s hydro output fell 3% last year, producing less than half its potential as dry spells, deforestation and floods disrupted generation. Similar declines have hit Canada, China and the United States, contributing to the biggest global drop in hydropower output since 1965. While some governments push for new mega-dams, critics argue that environmental and social costs are too high and advocate modernising existing infrastructure instead. Brazil is investing $270 million to overhaul Tucuruí and is increasingly relying on wind and solar to stabilise supply. As climate volatility grows, experts warn the world must rethink hydropower’s role and strengthen resilience to secure future energy needs.