I know that water can exist in various states (liquid, solid, ...) and can be in various places (clouds, oceans, ground, ...). What I want to know is whether or not the total number of water molecules on planet Earth is steadily increasing or decreasing and why? For example, is the amount of water now on planet Earth the same as it was 1000 years ago or a million years ago?
Based on answers from allure and farcher, I realize that my original question was not exactly what I wanted to know about so I have revised my question.