Water on Earth

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The earth contains about 1.36 billion tons of water.  This water is in constant motion, cycling through the earth’s water circulation system, moving through the oceans, the air, the land, and back again.

The great majority of the earth’s water is contained in the oceans, seas, and bays with 96.5% and totals about 321,000,000 cubic miles.  Only about 2.5% of the earth is freshwater.   Over two-thirds of the earth’s freshwater is locked up in icecaps and glaciers, totaling about 5,773,000 cubic miles in volume. The majority of the remaining freshwater is found in the world’s groundwater at 30.1%.

The remaining 1.2% of the world’s freshwater is mainly from surface water such as lakes, ground ice cover, the atmosphere, and biological water.  The atmosphere holds about 0.04% of the world’s water and biological matter (such as plants) contains another 0.003%.  The table below shows estimated sources of water.

Global Water Distribution

Water sourceWater volume, in cubic milesWater volume, in cubic kilometers% Freshwater% total water
Oceans, Seas, & Bays321,000,0001,338,000,000--96.5
Ice caps, Glaciers, & Permanent Snow5,773,00024,064,00068.71.74
Ground water5,614,00023,400,000--1.69
~ Fresh2,526,00010,530,00030.10.76
~ Saline3,088,00012,870,000--0.93
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

Source: Shiklomanov, 1993

Sources of Freshwater

This infographic from the United Nations Environmental Programme also adapted from Shiklomanov’s work shows the global distribution of freshwater sources from glaciers and ice caps, rivers and estuaries, and groundwater.

water-sources

References

Shiklomanov, Igor . 1993. “World fresh water resources”.  Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World’s Fresh Water Resources.

The World’s Water.  USGS.


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