The Land Between the Rivers

Four countries share the two rivers. There is no agreement between them all.

Two rivers rise in the mountains of eastern Turkey. They run south on either side of a single flood plain before meeting in southern Iraq, where they form the Shatt al-Arab and empty into the Gulf. Between them lies Mesopotamia, a Greek name meaning “the land between the rivers”. This is the plain where some of the first cities and the first writing system emerged.

The Euphrates is the longer of the two rivers. The Tigris is shorter, less meandering and carries more water. About 89% of the Euphrates’ flow is generated in Turkey. The Tigris draws more evenly on tributaries in Iraq and Iran. This geography determines the modern story of the rivers: the water is generated in the mountains and used on the plain.

Whoever controls the mountains controls the rivers, and the mountains are in Turkey.

Turkey promised Syria a minimum Euphrates flow of 500 cubic metres per second in a 1987 protocol. In 1990, Syria and Iraq agreed to divide the river, with 42% going to Syria and 58% to Iraq. But no agreement binds all the riparian states. The pledged minimum, about 16 billion cubic metres a year, is roughly half the 30 billion that crossed the border before 1973. As less water arrives from upstream, the Shatt al-Arab can no longer hold back the sea. Salt water therefore intrudes up the river towards Basra.

Schematic rather than cartographic: positions are indicative and the boundaries are drawn only to show which reach lies in which country.

Hammurabi’s Code already fixed who must keep which dam in repair.

For the people who first settled beside them, the two rivers were part of religious belief as well as agriculture. Cuneiform texts show how the marshes where the rivers meet shaped the region’s religious beliefs, rituals and literature. The Book of Genesis describes a river flowing out of Eden and dividing into four branches. It names two of them as the Hiddekel, meaning the Tigris, and the Euphrates. On this same flood-prone plain, Babylonian scribes recorded some of the oldest surviving stories of a great deluge. These stories were later retold in the Epic of Gilgamesh.

The rivers flooded violently and unpredictably, but they also carried something priceless: silt. When people channelled the flood water onto fields at the right moment, the plain became some of the most productive farmland in the ancient world. Learning to do this together and at scale was arguably the founding act of civilisation. It also required rules. Hammurabi’s Code, set down in Babylon under a king who reigned from 1792 to 1750 BCE, already specified who had to keep which dam in repair and who owed whom compensation for a flooded field.

Downstream, in the wetlands where the rivers braid together, the Ma‘dan, the Marsh Arabs, build villages on islands of reed and mud. They live from fish, rice and water buffalo in marshes that people have inhabited for more than five millennia.

• c. 5000 BCE

  The first canals

  At Choga Mami, on the plain’s eastern edge, farmers of the Samarra culture dig irrigation ditches, probably fed by a canal from the foothills. Large-scale irrigation later sustains the cities of Sumer, among them Uruk, Ur and Eridu.

• c. 1750 BCE

  Water, written into law

  Hammurabi’s Code sets penalties for neglecting a dam and for flooding a neighbour’s field.

• for 5,000 years

  The Marsh Arabs

  People have lived in the marshes for more than five millennia; the Ma‘dan build reed houses on artificial islands. About half a million live there in the 1950s.

• 1950s–70s

  The age of the barrage

  Iraq diverts Tigris floodwater at Samarra from 1954, and Turkey’s Keban Dam (1974) and Syria’s Tabqa Dam (1975) follow on the Euphrates. Regulation flattens the rivers’ natural seasonal flood.

• 1977–1992

  The GAP transforms the headwaters

  Turkey launches its Southeastern Anatolia Project across the sources of both rivers in 1977. The Atatürk Dam on the Euphrates, its centrepiece, is completed in 1992.

• 2020

  Ilısu at full power

  Turkey’s Ilısu Dam on the Tigris reaches full generating capacity. It sits at the heart of a planned reservoir system to regulate the second river.

In 2018, 118,000 people or more were hospitalised in Basra over the water.

Upstream in Turkey, the GAP project was planned around 22 dams and 19 hydropower plants across the headwaters of both rivers. Syria dammed the Euphrates at Tabqa, while Iran dammed Tigris tributaries such as the headwaters of the Diyala. The states above the plain now store, measure and release the water. The plain itself no longer controls those flows.

The consequences are felt at the bottom of the system. In 2018, reduced flows from upstream raised the levels of sewage, pollution and salt in the water, and 118,000 people or more were hospitalised in Basra. A city at the mouth of two great rivers could not supply its own population with water that was safe to drink.

The marshes went from 20,000 square kilometres to almost nothing, then partly came back.

No part of the system tells the story more starkly than the wetlands at its end. After the Gulf War and the unrest of 1991, a massive engineering programme drained the marshes. By 2000, the Central and Al Hammar marshes had lost more than nine-tenths of their land cover to bare earth and salt crust. The Ma‘dan population fell from about half a million in the 1950s to around 20,000. UNEP called the loss one of the world’s greatest environmental disasters.

After 2003, the water returned. Iraqis broke open the dikes and canals that had drained the marshes. By 2006, a UNEP assessment found that about 58% of the mid-1970s marsh area had been restored, with fish and birds re-establishing. Many Marsh Arabs returned too. UNESCO inscribed the Ahwar of Southern Iraq as a World Heritage site in 2016.

Each marsh is drawn as a simple shape whose area, not its width, carries the share. The dashed outline is the mid-1970s extent. Extent varies widely with rainfall and upstream releases.

The recovery is fragile because the water that refills the marshes is the same water that everyone upstream now wants. Satellite records show major losses of water and vegetation again in 2022 and 2023, linked to drought and upstream dams. Restoration here is not a single victory. It is a struggle that has to be won afresh every dry season.

The room to manoeuvre is no longer in the volume of water. It is in how it is used.

More efficient irrigation and putting treated water back to work could stretch the remaining supply a long way. So could a basin-wide bargain that finally treats the Tigris and Euphrates as the single system they have always been. No such bargain yet exists.