Water cycle
The Sun evaporates water, rain refills rivers and lakes, and gravity brings it down again.
Natural sources · Solar-derived flows · No. 3
- Natural sources
- Origin: Indirect solar
- Renewable: Yes
A cubic metre of water falling 100 metres holds only about 0.27 kWh, so hydropower has to move whole rivers.
Chart: Illustration: Water cycle
Where it comes from
Chart: Map of where it comes from
The Sun evaporates water, rain and snow drop it on high ground, and gravity pulls it back down through turbines, producing about 4,400-4,600 TWh in 2024.
Three things to know
- Africa has harnessed only about 11% of its more than 600 GW of hydropower potential.
- World hydro output fell about 5% in 2023 in drought, then rose about 10% in 2024.
- Türkiye's hydro output dropped 14% over five years even though its capacity grew 15%.
The journey
- 1 EvaporationSunlight lifts water from seas and land
- 2 Rain and snowWater falls on high ground
- 3 Rivers and reservoirsGravity gathers it into valleys and dams
- 4 TurbinesFalling water spins generators
- 5 Power and storageReleased on demand; 189 GW pumped storage