If the water on our planet does not disappear anywhere, then where did the problem of decreasing

If the water on our planet does not disappear anywhere, then where did the problem of decreasing fresh water supplies come from?

There are 3 reasons for the problem of lack of fresh water:
1. General climate change on the planet, as a result of which the regions that were once full of water are becoming arid.
2. Poisoning of fresh water supplies by enterprises and cities.
3. Growth in the number of mankind itself. It is with its increase, which every year becomes more and more impetuous, that less and less fresh water falls on each inhabitant of the Earth.