In Daniel 8, beside which waterway did Daniel see himself in his vision at Susa?

Answer: The Ulai

In the vision Daniel was in the citadel of Susa (KJV: Shushan) in the province of Elam, beside the Ulai Canal (KJV: river of Ulai).

“And in the vision I saw myself in the citadel of Susa, in the province of Elam. I saw in the vision that I was beside the Ulai Canal.”— Daniel 8:2 (BSB)