Otter Creek gamma rays

her mother appears again, offering an open-ended question that moonshine thinks on before replying. she doesn't want to waste the chance, and so after a moment, says, "I want to know where the river comes from." and then a moment later, "and where all the water comes from. shouldn't it run out? it's not raining, and it has to come from somewhere."

a source of infinite water seems unlikely and unrealistic, and if all this water came from a second lake, wouldn't that have to empty sometime, too?