Water on Earth

Caitlin Dempsey

Updated:

According to the USGS, the Earth contains about 332.5 million cubic miles (mi3), or 1,386 million cubic kilometers (km3) of water.  

Earth’s water is in constant motion, cycling through the Earth’s water circulation system, moving through the oceans, the air, the land, and back again.

What is the Hydrosphere?

In geography, all the water on Earth, whether it is found in water bodies, the ground, the air, or in living organisms is known as the hydrosphere.

Where is Water Found on Earth?

The great majority of Earth’s water is contained in the oceans, seas, and bays with 96.5% and totals about 321,000,000 cubic miles.  


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Earth’s Freshwater Sources

Only about 2.5% of the Earth’s water is freshwater.   

Over two-thirds of Earth’s freshwater is locked up in ice caps and glaciers, totaling about 5,773,000 cubic miles in volume.

Outside of the polar regions, the world’s largest reservoir of freshwater is stored within tens of thousands of glaciers in the Tibetan Plateau. The Tibetan Plateau is nicknamed the “Third Pole” because of its enormous reservoir of freshwater.

Some of the lakes in the Tibetan Plateau. Image: NASA Aqua Satellite, November 10, 2010.
Some of the lakes in the Tibetan Plateau. Image: NASA Aqua Satellite, November 10, 2010.

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 and animals) contains another 0.003%.  

A meandering stream in North Dakota.  Photo: Kathleen Macek-Rowland, USGS. Public domain.
A meandering stream in North Dakota. Photo: Kathleen Macek-Rowland, USGS. Public domain.

The table below shows estimated sources of water.

Table: Global Water Distribution

Water sourceWater volume, in cubic milesWater volume, in cubic kilometers% Freshwater% total water
Oceans, Seas, & Bays321,000,0001,338,000,00096.5
Ice caps, Glaciers, & Permanent Snow5,773,00024,064,00068.71.74
Ground water5,614,00023,400,0001.69
~ Fresh2,526,00010,530,00030.10.76
~ Saline3,088,00012,870,0000.93
Soil Moisture3,95916,5000.050.001
Ground Ice & Permafrost71,970300,0000.860.022
Lakes42,320176,4000.013
~ Fresh21,83091,0000.260.007
~ Saline20,49085,4000.006
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

Watch: Earth’s Water

YouTube video

Read next: Groundwater on Earth

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.

This article was first published November 13,2014 and has since been updated.

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About the author
Caitlin Dempsey
Caitlin Dempsey is the editor of Geography Realm and holds a master's degree in Geography from UCLA as well as a Master of Library and Information Science (MLIS) from SJSU.