What was the significance of the twelve springs and seventy date-palms?
Rashi and Targum Yonasan: The twelve springs corresponded to the twelve tribes; 1 and the seventy date-palms to the seventy elders. 2
Ramban (citing Ibn Ezra): The Pasuk mentions it to stress the contrast between it and the previous encampment (in Marah) where the water was bitter, 3 and date-palms do not flourish where the water is bitter.
Seforno: Even though the location was so convenient, they did not hesitate to move on when ordered to travel. 4
One for each tribe (Ramban and Targum Yonasan). Toras Avigdor (Beshalach, p. 2) - Hashem wanted each tribe to be independent. Similarly, we find (24:4) that Moshe built twelve Matzevos, one for each tribe.
Ramban: The seventy elders sat in the shade of the date-palms - all this in praise of Hashem, who miraculously prepared it for them from the day of the creation in an arid land.
Ramban: In fact it was because of the pleasant conditions that they remained there longer than most of the other encampments in the desert - as hinted in the words "va'Yachanu Sham."
Seforno: As Hashem stated in praise of Yisrael, "You followed Me in the desert" (Yirmeyah 2:20).