| River | Tributaries inside Iraq | Length (km) | Catchment area | Flow (m3/S) | |
| Total (km2) | Inside Iraq (%) | ||||
| Tigris | Main River | 1800 | 472,606 | 58 | 630 (Mosul) |
| Fiesh Khabur | 181 | 6143 | 43 | 68 | |
| Greater Zab | 462 | 25,810 | 62 | 418 | |
| Lesser Zab | 302 | 21,476 | 75 | 227 | |
| Adhaim | 330 | 13,000 | 100 | 25.5 | |
| Diyala | 574 | 31,846 | 80 | 182 | |
| Euphrates | Main River | 2786 | 444,000 | 41 | 909 (Hit) |