Animal urine and feces are not clean water, if you only have a couple of animals it doesn't matter but at a large scale you need to treat it before releasing it into the wild unless you want to taint the water supply. Of course the water molecules don't disappear, but that's not the point. There's plenty of water on earth, but only a tiny fraction is clean enough for human consumption. If you pour your bottle of mineral water into the ocean, the water doesn't disappear but you still effectively wasted it.

>you wouldn’t have a farm away from a water source.

That's sort of the problem actually. Many aquifers are tainted to various levels because of farming. We need clean water, not cow piss.