There is an old saying 'What goes up, must come down' - which is a very simple way to describe the 'Water Cycle'

Put very simply, the Water Cycle is when water from the sea or land evaporates, rises into the atmosphere, condenses and falls back to earth, where it collects and the whole cycle starts again.
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It's actually rather more complicated than that so why not go to the downloads page and save the document there called Sky to Tap and this will tell you the story in full.