How much water is on Earth? On Earth there is about 332.5 million cubic miles (mi³) or about 1,386 million cubic kilometers (km³) of water, (source: United States Geological Survey). The Earth’s water is circulating through oceans, the atmosphere, land, and living organisms. This cycle is known as the hydrologic cycle.
What is the Hydrosphere?
In the field of geography, the hydrosphere contains all of Earth’s water. This is the water found in oceans, lakes, rivers, underground reservoirs, ice, the atmosphere, and within living organisms.
Where is Water Found on Earth?
Saltwater: oceans, seas, and bays
Most of the water found on Earth —about 96.5%— is saltwater and found in oceans, seas, and bays, totaling around 321 million cubic miles (~1.34 billion cubic kilometers).
Freshwater sources
Only about 2.5% of Earth’s total water is freshwater.
- Ice caps and glaciers: Over two-thirds (about 68.7%) of Earth’s freshwater is locked in ice caps, glaciers, and permanent snow, representing roughly 5.8 million cubic miles (24 million cubic kilometers).
- Groundwater: About 30.1% of Earth’s freshwater exists underground, stored in aquifers and accessible via wells and natural springs.
The “Third Pole”: the Tibetan Plateau
Most of the freshwater reserves are stored in in ice and glaciers in the polar regions. After the polar regions (North and South poles), the Earth’s largest freshwater reserve is the Tibetan Plateau, home to tens of thousands of glaciers and is known as the “Third Pole.”
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Other freshwater reservoirs
The remaining freshwater—approximately 1.2%—includes:
- Surface water: Lakes and rivers hold only a small fraction, about 0.26% and 0.006% respectively.
- Ground ice and permafrost: About 0.86% is trapped as ground ice or permafrost.
- Atmosphere and organisms: Approximately 0.04% is atmospheric moisture, while a very small amount (about 0.003%) is contained within living organisms, including plants and animals.
Table: Global Water Distribution
The table below shows estimated sources of water.
| Water source | Water volume, in cubic miles | Water volume, in cubic kilometers | % Freshwater | % total water |
|---|---|---|---|---|
| Oceans, Seas, & Bays | 321,000,000 | 1,338,000,000 | — | 96.5 |
| Ice caps, Glaciers, & Permanent Snow | 5,773,000 | 24,064,000 | 68.7 | 1.74 |
| Ground water | 5,614,000 | 23,400,000 | — | 1.69 |
| ~ Fresh | 2,526,000 | 10,530,000 | 30.1 | 0.76 |
| ~ Saline | 3,088,000 | 12,870,000 | — | 0.93 |
| Soil Moisture | 3,959 | 16,500 | 0.05 | 0.001 |
| Ground Ice & Permafrost | 71,970 | 300,000 | 0.86 | 0.022 |
| Lakes | 42,320 | 176,400 | — | 0.013 |
| ~ Fresh | 21,830 | 91,000 | 0.26 | 0.007 |
| ~ Saline | 20,490 | 85,400 | — | 0.006 |
| Atmosphere | 3,095 | 12,900 | 0.04 | 0.001 |
| Swamp Water | 2,752 | 11,470 | 0.03 | 0.0008 |
| Rivers | 509 | 2,120 | 0.006 | 0.0002 |
| Biological Water | 269 | 1,120 | 0.003 | 0.0001 |
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.
Watch: Earth’s Water
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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.
Fonte : National Geographic
