Albert Barnes Commentary 2 Kings 3:9

"So the king of Israel went, and the king of Judah, and the king of Edom; and they made a circuit of seven days` journey: and there was no water for the host, nor for the beasts that followed them." — 2 Kings 3:9 (ASV)

Seven days’ journey - The distance of the route they probably followed is not much more than 100 miles. However, the difficulties of the way are great, and the army might not have been able to move along it at a faster rate than about 15 miles a day.

No water - The kings had probably expected to find sufficient water for both their men and baggage animals in the Wadi el-Hasa, which divides Edom from Moab and has a stream that is now regarded as perennial. But it had dried up—a very possible occurrence with any of the streams in this region.