Water Cycle

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The vertical and horizontal transport of water in all its states between the earth, the atmosphere, and the seas.

For a detailed explanation of where Earth's water exists, see the chart and data table below. The water cycle describes the movement of Earth's water, so realize that the chart and table below represent the presence of Earth's water at a single point in time.

Water regulates climate, storing heat during the day and releasing it at night. Water in the ocean and atmosphere carry heat from the tropics to the poles. The process by which water moves around the earth, from the ocean, to the atmosphere, to the land and back to the ocean is called the water cycle.

The world's total water supply of about 332.5 million cubic miles of water, over 96 percent is saline. And, of the total freshwater, over 68 percent is locked up in ice and glaciers. Another 30 percent of freshwater is in the ground. Fresh surface-water sources, such as rivers and lakes, only constitute about 22,300 cubic miles (93,100 cubic kilometers), which is about 1/150th of one percent of total water. Yet, rivers and lakes are the sources of most of the water people use everyday.


One estimate of global water distribution:
Water sourceWater volume, in cubic milesWater volume, in cubic kilometersPercent of freshwaterPercent of total water
Oceans, Seas, & Bays321,000,0001,338,000,000--96.5
Ice caps, Glaciers, & Permanent Snow5,773,00024,064,00068.71.74
Groundwater5,614,00023,400,000--1.7
    Fresh2,526,00010,530,00030.10.76
    Saline3,088,00012,870,000--0.94
Soil Moisture3,95916,5000.050.001
Ground Ice & Permafrost71,970300,0000.860.022
Lakes42,320176,400--0.013
    Fresh21,83091,0000.260.007
    Saline20,49085,400--0.006
Atmosphere3,09512,9000.040.001
Swamp Water2,75211,4700.030.0008
Rivers5092,1200.0060.0002
Biological Water2691,1200.0030.0001
Total332,500,0001,386,000,000-100
Source: Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp.817-823.

[edit] Also See

[edit] Reference

  1. Wikipedia Water Cycle [1]

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