evidence: SHATT al-ARAB (ŠAṬṬ al-ʿARAB), name given to the ca. 200 km long, 400-1500 m wide (Rzóska, p. 47), combined effluent of the Euphrates and Tigris below Qurna, to which the Karun (Kārūn) contributes from Khorramshahr (Ḵorramšahr; formerly, until 1937, Moḥammara) southward. The name derives from Arabic šaṭṭ "bank, side" , with reference to a river (Eilers, pp. 301, 316; cf. New Persian rud-bār; hence not the "Arab stream" as stated by Le Strange, p. 26). The Shatt al-Arab is influenced by tides in the Persian Gulf, from ca. 5 m around Basra to ca. 3 m at its mouth, which contribute to the high level of dissolved salts in it (Rzóska, pp. 47, 68-72). While only 10 percent of the sediment deposited in the Shatt al-Arab is brought by the Tigris and Euphrates, 90 percent is carried south by the Karun (Cressey, p. 449), and "depressions, inundation basins and marshes act as silt tanks" (Rzóska, p. 52). At different times in the past, massive dredging operations have been undertaken in order to keep the Shatt al-Arab navigable (e.g. Ferrier, p. 449 ff).