I find understanding this sort of thing is much easier to look at from an energy perspective than a materials perspective. Water is "used" when entropy is dumpe

I find understanding this sort of thing is much easier to look at from an energy perspective than a materials perspective. Water is "used" when entropy is dumped into it that makes it less suitable for usage. It takes energy to turn it back into useful pure water. Nature provides a lot of energy that turns it back into pure water, but it may not do it as quickly as we use it, or where we want it, or when we want it. And sometimes the problem is that it dumps fresh water on us far in excess of our desires. It's still not a perfect perspective, because the exact nature of what's in the water can be an issue (i.e., urine is "bad" for most uses, but may fertilize well, etc.). But it's at least closer to the truth than the mindset that water is poured into a cow and disappears from the universe entirely. If goodness and pureness was a one-time consumable item that way, the way some people seem to conceive of it, the ecosystem would have run out of it billions of years ago. It is a renewable resource.