It's not about parts per billion or what other animals do in the reservoir, it's about irrationality and phobia of pee that came out of humans; and to work with irrationality (to keep people drinking the water as opposed to switching to bottled as a result of this knucklehead), overreactions, like draining the whole thing, might be the right move.
How can that be the right move? If everyone stopped using water and there was a massive run on bottled water, it might be worth doing as a concession, but doing it pre-emptively is nonsense. What irrationality are we going to have to pander to next?