Salinity gradient: Across the Earth
Big rivers, open seas: where the resource sits
What this tab covers How the resource varies with latitude, climate, terrain and geology: the richest and poorest regions and the leading countries.Concentrated at the mouths of large rivers meeting salty seas; Asia and South America hold most of the technical potential.
Potential scales with fresh-water discharge and with the salinity contrast, so large tropical and monsoon rivers flowing into open ocean are best. IRENA also rates equatorial areas with high, stable year-round temperatures as attractive.
Rich and poor regions
| Region | Resource | Level |
|---|---|---|
| Asia | 208 GW technical potential1 | high |
| South America | 199 GW1 | high |
| North America | 98 GW (the St Lawrence singled out as very high)1 | medium |
| Africa | 63 GW1 | medium |
| Europe | 49 GW1 | low |
| Australia and Oceania | 30 GW1 | low |
| Rhône estuary, France | up to 500 MW if replicated (developer estimate)4 | medium |
Most of the resource sits where large rivers reach the open sea, which is why Asia and South America together hold about 60% of IRENA's technical potential. Sources of concentrated brine raise the energy per cubic metre (up to about 15 MJ with saturated brine, against 1.4 MJ in an ordinary estuary), which is why Japan's first plant, at Fukuoka, uses concentrated seawater from a desalination works and why hybrid designs attract research interest.
Sources
- Salinity Gradient Energy: Technology Brief IRENA, 2014
- What is osmotic energy and how could it generate one-fifth of the world's energy needs? World Economic Forum, 2025