system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can we run out of clean water ?

From my understanding, water has a pretty complex life cycle that can boil down to (hehe) this : it'll move around in the ground and in the air forever, sometimes passing through  alive creatures in the process.

But water is water, if I buy 100L of bottled water and pour it to the ground, is it really wasted? It's just moving through the cycle and it'll come back just as clean eventually. The waste is financial for me or for the cleaning process in the water treatment plant. But really the water on the planet is always the same amount, right? It's finite, but both abundant and "self cleaning", no?

When I see the rivers being dry I can't help but think the water is just elsewhere, which is just a matter of reaching it. 

Bonus question : How does toxic waste affect that cycle? Is evaporating enough to be clean again?
gpt
>it'll come back just as clean eventually.

Your "eventually" is doing a lot of heavy lifting there. It might not precipitate out as rain for 1,000 years or more - and when it does, if it falls over the ocean then it's not going to be available as drinking water anyway.

So yes, over a timespan of millennia there is always "enough" fresh water on earth. But that sort of timespan is irrelevant to most living things on earth, who will die if they don't get water for a week, let alone for the next thousand years.