Map of the canals (nahrs) along the medieval course of the Tigris below Wasit in southern Iraq, in around 900 AD. The canals are as follows:
1. Nahr (A)ban
2. Nahr Quraysh
3. Nahr al-Sib	
4. Nahr Barduda
Background map is from Le Strange, Lands, Map II. The information on the canals comes from Le Strange, Ibn Serapion, pp. 271, 273-274.
References:

Le Strange, Guy. "Description of Mesopotamia and Baghdad, written about the year 900 A.D. by Ibn Serapion." The Journal of the Royal Asiatic Society of Great Britain and Ireland for 1895. London: Royal Asiatic Society, 1895.
Le Strange, Guy. The Lands of the Eastern Caliphate: Mesopotamia, Persia, and Central Asia, from the Moslem conquest to the time of Timur. Cambridge: Cambridge University Press, 1905.
Own work
Ro4444