The story. Two major Brazilian government studies conclude that climate change is fundamentally reshaping the country's hydropower outlook, with Amazon plants facing up to 40% generation losses in coming decades. Belo Monte, the controversial mega-dam on the Xingu River, averaged just 145 MW during the 2024 dry season — barely 1% of its 11,233 MW capacity.

The bigger picture. That vulnerability matters because Brazil's grid depends on water like few others. Hydro generated 413 TWh in 2024 (Ember), roughly 55% of the country's electricity — a dependence that keeps Brazil's carbon intensity at just 106 gCO2/kWh (Ember), less than a quarter of the global average of 471. Carbon intensity measures how much CO2 it takes to produce a unit of electricity, and Brazil's remarkably low figure exists almost entirely because of hydropower. But the water underpinning that clean grid faces compounding threats. Brazil lost 5.4 million hectares of tree cover in 2024 (GFW), and Amazon forests generate much of their own rainfall through transpiration — trees pull water from soil and release it as vapor, seeding rain clouds downwind. Each hectare cleared weakens the moisture recycling that feeds the rivers powering these dams. Government researchers estimate that compensating for declining hydro reliability will require 121 GW of new wind, solar, and storage capacity, at a cost of $28 billion.

The tension. Rising temperatures will push electricity demand higher, especially for cooling, at the very moment drought is eroding the clean energy source Brazil most depends on. Building replacements takes decades; the rivers are already shrinking.