The natural water sources in continual motion and transitions (liquid, solid, gas) make up the water cycle in the biosphere: evaporation, condensation and precipitation. Water transport in the atmosphere, dissolving and carrying more nutrients, minerals and some substances necessary for the life of animals and plants.
The water ponds, lakes, rivers and oceans ... thanks to solar energy sun evaporates into the atmosphere, water vapor condenses and rains down on Earth's surface. Water flows in the global scope, make up the balance of the country and participate in the process of the Earth's climate. The vapors from the plants to increase air moisture. Part of rainfall through soil into groundwater, groundwater and surface water are seaward to circulate again, it's water cycle. However, fresh water and rain water on the planet is not evenly distributed. Currently, annual worldwide use only about 4000 km3 of freshwater, accounting for over 40% of the fresh water can be exploited.
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