| Countries | Tigris River | Euphrates River | ||
| Catchment area (km2) | Catchment area (%) | Catchment area (km2) | Catchment area (%) | |
| Turkey | 57,614 | 12.2 | 125,000 | 28.2 |
| Syria | 834 | 0.2 | 76,000 | 17.1 |
| Iraq | 253,000 | 58 | 177,000 | 39.9 |
| Iran | 140,180 | 29.6 | - | - |
| Saudi Arabia | - | - | 66,000 | 14.9 |
| Total | 473,103 | 100 | 444,000 | 100 |