That I don't know, where would it go? I read about using the evaporation method years ago and wherever it was from, it said to leave the lid off, but I liked a clean thin towel to keep stuff out.
Whatever works for you is what matters. We have a generator that will pump water and run the rest of our household essentials for quite a long time if used sparingly.
Our well water is bad, even the dogs will not drink it, and thus we rely on the artesian spring. We can also get water from our lake to flush the toilet if all our back-up options fail.
People in the areas that expect to lose electrical power might want to check to see if there are any safe artesian wells in there area. They are not always well publicized. Those who sell water do not usually like a free water source widely known to the public.