Most people think the water never runs out. But we are faced with the problem of water shortage? The water is really day gone? Do you know what causes the water never runs out. It is because the water cycle itself with circulation water cycle is that the water in the water source, such as a river, sea and ocean, etc. Volatile into water vapor when the solar heat. Vapor in the atmosphere when it gets cold condensation into clouds. The water in the air was to organize a rain and snow to the earth. Most of which fall to the area of the ocean. The fall in the form of rain and snow, and some can absorb into soil and flows into the water.