The Water Cycle - Water Science for Schools

## Water Cycle Pages

Water Cycle for Kids

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# The Water Cycle

## Water Cycle for Schools

Water cycle for kids (ages 5-95) and schools - in many languages. Available as:

Earth's water is always in movement, and the natural water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years.

## Global water distribution

For an estimated explanation of where Earth's water exists, look at the chart below. By now, you know that 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. If you check back in a thousand or million years, no doubt these numbers will be different!

Notice how of 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.

Source: Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York).

## Where is Earth's water?

For a detailed explanation of where Earth's water is, look at the data table below. Notice how of the world's total water supply of about 333 million cubic miles (1,386 million cubic kilometers) 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. Thus, rivers and lakes that supply surface water for human uses only constitute about 22,300 cubic miles (93,100 cubic kilometers), which is about 0.007 percent of total water, yet rivers are the source of most of the water people use.

One Estimate of Global Water Distribution
(Numbers are rounded)
Water sourceWater volume, in cubic milesWater volume, in cubic kilometersPercent of
freshwater
Percent 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--1.69
Fresh2,526,00010,530,00030.1  0.76
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: Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York).

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