R.E. Emmerick: ĀQSŪ. In: Encyclopaedia Iranica. “The name is Turkish and is first used of this town in the 14th century. Turkish aq sū (“white water”) is a technical term referring to the original bed of a river, by contrast with qara sū (‘black water’), used of a derivative canal. Āqsū is the name of several rivers including the one in Sin-kiang that flows southeast from the T’ien-shan mountains.”
