Ulai

the Eulaus of the Greeks; a river of Susiana. It was probably the eastern branch of the Choasper (Kerkhan), which divided into two branches some 20 miles above the city of Susa. Hence Daniel (Dan 8:2 ; 8:16) speaks of standing "between the banks of Ulai", i.e., between the two streams of the divided river.

EBD - Easton's Bible Dictionary