Executive Summary 

The Tigris River Basin has several sub-basins that are shared between Iraq and Turkey or between Iran and Iraq. The main shared tributaries are the Feesh Khabour, the Greater Zab, the Lesser Zab and the Diyala.

With more than 27 BCM, the Tigris tributaries significantly contribute to total Tigris river flow. The main contribution to discharge originates from the Greater and Lesser Zab Rivers, which contribute 40-60% of total Tigris flow in Baghdad. In general, the four shared tributaries exhibit similar flow regimes, with normal fluctuations of wet and dry years around the mean annual flow. Although the Lesser Zab and the Diyala have been dammed since the 1960s, there is currently no evidence of a regulated stream-flow regime.

Water resources management differs from one shared basin to another. While the Greater Zab is to date unregulated, several of the dams and regulators on the Lesser Zab and the Diyala support irrigated agriculture projects in the region. No specific water agreements govern any of the four tributaries.

  • The Lesser Zab in Bekhme, Iraq, 2005. Source: Ed Kashi/VII.
  • The Greater Zab River, at Zahko, Iraq, 2012. Source: James Gordon.
  • Irrigation canal near the town of Taweela in the Diyala Basin, Iraq, 1992. Source: Ed Kashi/VII.
  • The Greater Zab in Bekhme, Iraq, 2005. Source: Ed Kashi/VII.

Basin Facts 

River Feesh Khabour Greater Zab Lesser Zab Diyala
Basin Area Shares Iraq 43%
Turkey 57%
Iraq 65%
Turkey 35%
Iran 24%
Iraq 76%
Iran 25%
Iraq 75%
Basin Area 6,143 km2 26,310 km2 19,780 km2 33,240 km2
River Length 181 km 462 km 302 km 574 km
Mean Annual Flow Volume 2 BCM 12.7 BCM 7.8 BCM 4.6 BCM
Dams Unregulated to date Unregulated to date 2 (~7 BCM capacity) 4 (>7 BCM capacity)
Projected Irrigated Area ~37,000 ha -- -- --