the water cycle

1943 Words8 Pages
بسم الله الرحمن الرحيم السلام عليكم ورحمة الله وبركاته Water cycle The Earth 's water is always in movement, and the water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Since the water cycle is truly a "cycle," there is no beginning or end. Water can change states among liquid, vapor, and ice at various places in the water cycle, with these processes happening in the blink of an eye and over millions of years. Although the balance of water on Earth remains fairly constant over time, individual water molecules can come and go in a hurry, but there is always the same amount of water on the surface of the earth Description The…show more content…
Evaporation often implicitly includes transpiration from plants, though together they are specifically referred to as evapotranspiration. Total annual evapotranspiration amounts to approximately 505,000 km³ of water, 434,000 km³ of which evaporates from the oceans.[5] Sublimation is the state change directly from solid water (snow or ice) to water vapor.[6] Advection is the movement of water — in solid, liquid, or vapour states — through the atmosphere. Without advection, water that evaporated over the oceans could not precipitate over land.[7] Condensation is the transformation of water vapour to liquid water droplets in the air, producing clouds and fog.[8] Reservoirs In the context of the water cycle, a reservoir represents the water contained in different steps within the cycle. The largest reservoir is the collection of oceans, accounting for 97% of the Earth 's water. The next largest quantity (2%) is stored in solid form in the ice caps and glaciers. This small amount accounts for approximately 75% of all fresh water reserves on the planet. The water contained within all living organisms represents the smallest reservoir. The volume of water in the fresh water reservoirs, particularly those that are available for human use, are important water resources.[10 Residence times The residence time of a reservoir within the hydrologic cycle is the average time a water
Get Access