SPC Water, Sanitation and Hygiene : Water Distribution

Water Distribution

What is the big deal?

Water on and in the Earth

Where is Earth's water located and in what forms does it exist? You can see how water is distributed by viewing these pie charts. The left-side pie shows where the water on Earth exists; about 97 percent of all water is in the oceans. The middle pie shows the distribution of that three percent of all Earth's water that is freshwater. The majority, about 69 percent, is locked up in glaciers and icecaps, mainly in Greenland and Antarctica. You might be surprised that of the remaining freshwater, almost all of it is below your feet, as ground water. No matter where on Earth you are standing, chances are that, at some depth, the ground below you is saturated with water. Of all the freshwater on Earth, only about 0.3 percent is contained in rivers and lakes—yet rivers and lakes are not only the water we are most familiar with, it is also where most of the water we use in our everyday lives exists.

How much of Earth's water is available for our uses

...and in what forms does it exist? You can best see how water is distributed by viewing these pie charts. The right-side pie chart shows that over 99 percent of all water (oceans, seas, ice, most saline water, and atmosphereic water) is not available for our uses. And even of the remaining fraction of one percent (the small blue slice in the top pie chart), much of that is out of reach. Considering that most of the water we use in everyday life comes from rivers (the small dark blue slice in the bottom pie chart), you'll see we generally only make use of a tiny portion of the available water supplies. The right-side pie shows that the vast majority of the fresh water available for our uses is stored in the ground (the large grey slice in the second pie chart).

Estimate of global water distribution

Total AreaWater source	Volume in miles³	Volume in kilometers³	% of Freshwater	% of 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
Groundwater	5,614,000	23,400,000	–	1.7
Fresh	2,526,000	10,530,000	30.1	0.76
Saline	3,088,000	12,870,000	–	0.94
Soil Moisture	3,959	16,500	0.05	0.001
Gound Ice and 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
Total	332,500,000	1,386,000,000	–	100

For a detailed explanation of where Earth's water is, look at this table. Notice how of the world's total water supply of about 332.5 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, surface-water sources (such as rivers) only constitute about 22,300 cubic miles (93,100 cubic kilometers), which is about 1/700th of one percent of total water, yet rivers are the source of most of the water people use.

Credit: U.S. Geological Survey Department of the Interior/USGS, 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.