|This article does not cite any references or sources. (May 2010)|
During the early Islamic centuries, the Daylamite Buwayhid king, Panah Khusraw Adud ad-Dawlah, ordered the digging of a canal to join the Karun River, which at the time emptied independently into the Persian Gulf through the Bahmanshir channel, to the Arvand Rud/Shatt al-Arab waterway, the joint estuary of the Tigris and Euphrates rivers. The extra water from the Karun, which, at times during the spring melt, discharged over 27 times the volume of the Tigris-Euphrates water that reaches the Shatta al-Arab) makes the joint estuary more reliably navigable.
The estuary thus created was known as the Haffar, Arabic for "excavated," "dug out," which exactly described what the channel was: a man-made canal. The Haffar soon became the main estuary of the Karun, as it is at present, replacing the Bahmanshir.