that the waters which came down from above stood, and rose up in one heap, a great way off, at Adam, the city that is beside Zarethan; and those that went down toward the sea of the Arabah, even the Salt Sea, were wholly cut off: and the people passed over right against Jericho.
There is additional information here in  Joshua 3:17.  At some point in the progress of Israel over Jordan, the priests moved into the very midst of Jordan, where they stood until the passage was completed.  "The priests bearing the ark first took up their stand on the brink of the river, but as they advanced to mid-channel, the river was dried up before them."[26]