Water is the only substance found at all three levels of the earth (surface, subsurface and atmosphere). The hydrological cycle is a process of circulation of a fluid through a system of a closed-loop.
It happens due to the conservation of energy and momentum. This makes sure that water will always reach its lowest level, till it becomes ocean again.
About 71 per cent of the planetary water is found in the oceans. The remaining is held as freshwater in glaciers and icecaps, groundwater sources, lakes, soil moisture, atmosphere, streams and within life.
Nearly 59 per cent of the water that falls on land returns to the atmosphere through evaporation from over the oceans as well as from other places. The remainder runs-off on the surface, infiltrates into the ground or a part of it becomes glacier.
