Shatt al Arab (shät äl äˈräb) [key], tidal river, 120 mi (193 km) long, formed by the confluence of the Tigris and Euphrates rivers, flowing SE to the Persian Gulf, forming part of the Iraq-Iran border; the Karun is its chief tributary. The Shatt al Arab flowed through a broad, swampy delta, but the marshlands in Iraq were drained in the early 1990s in order to increase government control over the Arab Shiites (Marsh Arabs) who lived there. Restoration of the marshlands began in 2003, following the invasion of Iraq by Anglo-American forces, but only half the area has been restored. The river supplies fresh water to S Iraq and Kuwait but the construction of dams and the demand for water upstream has led to a greatly increased salt content. The Shatt al Arab is navigable for oceangoing vessels as far as Basra, Iraq's chief port.
Iraq and Iran have disputed navigation rights on the Shatt al Arab since 1935, when an international commission gave Iraq total control of the Shatt al Arab, leaving Iran with control only of the approaches to Abadan and Khorramshahr, its chief ports, and unable to develop new port facilities in the delta. To preclude Iraqi political pressure and interference with its oil and freight shipments on the Shatt al Arab, Iran built ports on the Persian Gulf to handle foreign trade. Iran and Iraq negotiated territorial agreements over the Shatt al Arab waterway in 1975, but by the end of the decade skirmishes in the area became prevalent. Full-scale war between the two countries broke out in Sept., 1980, leading to eight years of attacks on coastal areas (see Iran-Iraq War). The Shatt al Arab remains a source of conflict, as limited water access and unresolved maritime boundaries in the region persist.
See R. N. Schofield, Evolution of the Shatt al Arab Boundary Dispute (1986).