"I agree with Misa," added Violet. "And, you could also use transfiguration to create signals to mark your path and signal for help. If you transfigure natural things into something different, they would really stand out and alert rescuers." As for water, the Aguamenti charm would do for that, as long as you had your wand. And food--Violet knew a person could go a lot longer without food than without water or shelter, so she didn't really see that as a priority, unless you were going to be lost for a long time.