Executive Summary 

The Tigris River is the second largest river in Western Asia. Its basin is shared by four countries: Iran, Iraq, Syria and Turkey. Besides contributions from precipitation that originates in the Armenian Highlands, the Tigris is fed by numerous tributaries that rise in the Zagros Mountains in Iran, Iraq and Turkey.

The Tigris has a higher water yield than the Euphrates River. Historically, the natural annual flow of the Tigris at the Iraqi-Syrian-Turkish border was around 21 BCM. In recent years, Tigris flow volumes have been affected by large water development projects in Iraq and Turkey. The flow volume records for Kut show a significant negative trend. Water supplies to the Mesopotamian Marshlands have also dwindled over the past 40 years.

In addition to Turkey's use of the Tigris River for the Southeastern Anatolia Project (GAP), Iraq has built several dams and diversion projects on the river, centring on the Tharthar Canal between the Euphrates and Tigris. Water from the Tigris is mainly used for agriculture, with irrigation projects in all riparian countries.

Water quality in the basin is primarily threatened by rising salinity rates resulting from intensive irrigated agriculture and high evaporation rates.

Apart from historic agreements that jointly address the Euphrates and Tigris Rivers, water resources in the Tigris Basin have not received much attention at the negotiation table. There is no basin-wide agreement in place, and the Tigris River has been the subject of only one bilateral agreement.

Main Agreements 

Iraq - Turkey

1946 – The Treaty of Friendship and Good Neighbourly Relations is the first legal instrument of cooperation on water between the two riparian countries. Among others, it addresses flow regulation on the Tigris and Euphrates and their tributaries and the monitoring of flow data. The parties also commit to the principle of prior notification with regards to water infrastructure projects.

Iran - Iraq

1975 – Agreement on the use of shared watercourses in which the signatory parties agree on the division of a number of shared Tigris tributaries.

Iraq - Syria

2002 – Agreement on the establishment of a pumping station on the Tigris River in Syria, specifying project area and volume of water extracted.

Syria - Turkey

2009 – The Turkish-Syrian Strategic Cooperation Council Agreement covers water issues and can be regarded as the Turkish approval of Syria's pumping project on the Tigris River.

Key Concerns 

Water Quantity

Water use for irrigation and hydropower production is constantly increasing, with numerous operational and planned projects along the river's main course and its tributaries placing pressure on flow regimes in the basin. Periodic droughts affect water supply and may impact water allocation to different sectors in the future. There is no basin-wide agreement and no common approach or consensus on how to regard the Euphrates and Tigris Rivers (i.e whether the two rivers should be considered part of a single watercourse system or as separate basins).

While the development of new infrastructure along the river course has in general not sparked disputes among basin countries, the Ilisu Dam Project in Turkey remains controversial. Iran's damming of the Wand River has also caused tensions between Iran and Iraq.

Water Quality

Water quality is relatively good in the upper part of the basin, but salinity levels increase in the Iraqi part of the basin.

Rising pollution from domestic and industrial sources is a cause for concern.


The Mesopotamian Marshes have suffered severe damage as a result of upstream damming projects in the 20th century, reducing the marshes to 14% of their original size. More than half of the original area of this unique freshwater system has recently been rehabilitated in a joint effort by the Iraqi Government and international organizations.

  • Hasankeyf, Turkey, 1992. Source: Ed Kashi/VII.
  • The Tigris River at Baghdad, Iraq, 2006. Source: James Gordan.
  • Agriculture in the region of Arbil, Iraq, 2007. Source: Ben Barber, USAID.
  • The Tigris at Diyarbakir, Turkey, 2007. Source: Raki Man.
  • Bridge spanning Tigris River in Baghdad, Iraq, 2010. Source: Larisa Epatko.

Basin Facts 

Riparian Countries Iran, Iraq, Syria, Turkey
Basin Area Shares Iran 19%, Iraq 56.1%, Syria 0.4%, Turkey 24.5%
Basin Area 221,000 km2
River Length 1,800 km
Mean Annual Flow Volume 26 BCM (at Kut)
Dams 14 (max. storage capacity 116.5 BCM)
Projected Irrigated Area (In Basin) ~4.6 million ha
Projected Irrigated Area (Outside of Basin) 150,000 ha
Basin Population 23.4 million