“Tigris River: Arabic Shatt Dijla: biblical Hiddekel. River, southeast Turkey and Iraq. It is 1,180 miles (1900 kilometers) long. It originates in the Taurus Mountains at Lake Hazar, Kurdistan, and flows southeast through Turkey and past Baghdad to unite with the Euphrates River at Al Qurnah in southeast Iraq; there it forms the Shatt al Arab. With the Euphrates it defined the ancient religion of Mesopotamia. Important for its irrigation capacity, it gave rise to sustained civilization. The ruins of many ancient cities lie on its banks, including those of Nineveh, Calah, Ashur, Ctesiphon, and Seleucia.”
Excerpted from: Stevens, Mark A., Ed. Merriam Webster’s Collegiate Encyclopedia. Springfield, Massachusetts: Merriam-Webster, 2000.