The water doesn't just "disappear". If it's not in the ground, or on the ground, then it's in the air above the ground. And if you put enough water into the air above the ground, it will fall back onto the ground somewhere. Or maybe into the sea...

The problem we have is that we're reproducing too much in areas without enough natural resources, and too little in areas with enough resources. Humanity is incorrectly distributed around the Earth.

edit

A coworker just sent me this article about a billboard that devaporates water from the air, and provides it from a tap at the bottom:

http://news.yahoo.com/blogs/sideshow/billboard-air-water-per...