All the water on earth is involved in an endless cycle in which it moves from the surface of the earth into the atmosphere and then back again. This constant movement is called the water cycle. Water rises into the atmosphere, cools, condenses and returns to the Earth's surface as rain or snow.
Then the water either evaporates straight back into the atmosphere, is carried by rivers to the sea or goes deep underground. Some water is locked into ice caps and glaciers.
It might take thousands of years, but eventually all this water will evaporate back into the atmosphere where it will once again condense and fall back to Earth. And so the cycle continues. - Violent Planet, ticktock