Jamieson, Fausset and Brown on Exodus 15:27

27. they came to Elim, where were twelve wells of water--supposed to be what is now called Wady-Ghurandel, the most extensive watercourse in the western desert--an oasis, adorned with a great variety of trees, among which the palm is still conspicuous, and fertilized by a copious stream. It is estimated to be a mile in breadth, but stretching out far to the northeast. After the weary travel through the desert, this must have appeared a most delightful encampment from its shade and verdure, as well as from its abundant supply of sweet water for the thirsty multitude. The palm is called "the tree of the desert," as its presence is always a sign of water. The palms in this spot are greatly increased in number, but the wells are diminished.