2.1 Regional hydro resources
Looking at the first four columns of Table 1 below shows the estimated total hydro resource and technical potential for different regions of the world, together with their percentage share of the technical potential, with the total here mainly based on national data, which may include small-scale hydro plants.
| Resources | Output | |||||
| Region | Total resource/TWh y Footnotes -1 | Technical potential/TWh y Footnotes -1 | % of world technical potential | Installed capacity/GW | Annual output/TWh y Footnotes -1 | Percentage of technical potential used |
| North America | 5500 | 2420 | 15% | 168 | 680 | 28% |
| South America | 7500 | 2840 | 18% | 132 | 689 | 24% |
| Europe | 4900 | 2760 | 17% | 221 | 892 | 32% |
| Middle East | 690 | 280 | 1.7% | 22 | 21 | 7% |
| Africa | 3900 | 1890 | 12% | 22 | 114 | 6% |
| Asia-Pacific | 17300 | 5820 | 36% | 307 | 1627 | 28% |
| World | 39800 | 16000 | 4023 | |||
Some sources suggest that world total capacity, including small-scale hydro is close to 1000 GW (source: WEC, 2010a; (British Petroleum, 2017)), around one-fifth of the technical potential, suggesting that a fourfold increase in output might be possible in future, but this is by no means the case for individual regions.
Hydro resources on a national level are examined next.