Water use
Water use can mean the amount of water used by a household or a country, or the amount used for a given task or for the production of a given quantity of some product or crop, or the amount allocated for a particular purpose.
Globally, of precipitation falling on land each year (about 117,000 km3 (28,000 cu mi)), about 4 percent is used by rainfed agriculture and about half is subject to evaporation and transpiration in forests and other natural or quasi-natural landscapes. The remainder, which goes to groundwater replenishment and surface runoff, is sometimes called “total actual renewable freshwater resources”. Its magnitude was recently estimated at 52,579 km3 (12,614 cu mi)/year. It represents water that can be used either instream or after withdrawal from surface and groundwater sources. Of this remainder, about 3,918 km3 were withdrawn in 2007, of which 2,722 km3 (69 percent) were used by agriculture, and 734 km3 (19 percent) by other industry. Most agricultural use of withdrawn water is for irrigation, which uses about 5.1 percent of total actual renewable freshwater resources. World water use has been growing rapidly in the last hundred years (see graph from New Scientist article).
There are numerous measures of water use, including total water use, drinking water consumption, non-consumptive use, withdrawn water use (from surface and groundwater sources), instream use, water footprint, etc. Each of these (and other) measures of water use is appropriate for some purposes and inappropriate for others. Water “footprints” have become popular measures of use, e.g. in relation to personal consumption. The term "water footprint" is often used to refer to the amount of water used by an individual, community, business, or nation, or the amount of water use associated with (although not necessarily assignable to) a product.
The total water footprint of a typical 3-person household in the U.S. is 23,360 l (5,140 imp gal; 6,170 US gal). By comparison, a typical single family home in the U.S. only uses about 262 l (58 imp gal; 69 US gal) of water per day (2008 estimate). This includes (in decreasing order) toilet use, washing machine use, showers, baths, faucet use, and leaks.More recent study of residential end uses of water showed that since the late 1990s, total indoor use has decreased by 22 percent, primarily due to the improved water efficiency of clothes washers and toilets.
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