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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),〔Schneider, U. et al. 2014. GPCC’s new land surface precipitation climatology based on quality-controlled in-situ data and its role in quantifying the global water cycle. Theoretical and Applied Climatology. 115: 15-40.〕 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.〔FAO. Water use. http://www.fao.org/nr/water/aquastat/water_use/index.stm#tables〕 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/year.〔Frenken, K. and V. Gillet. 2012. Irrigation water requirement and water withdrawal by country. AQUASTAT, FAO.〕 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 Of this remainder, about 3,918 km3 were withdrawn in 2007, of which 2,722 km3 (69 percent) were used by agriculture, and 734 km3 (19 percent) by other industry.〔FAO. 2014. Water withdrawal by sector, around 2007. http://www.fao.org/nr/water/aquastat/tables/WorldData-Withdrawal_eng.pdf〕 Most agricultural use of withdrawn water is for irrigation, which uses about 5.1 percent of total actual renewable freshwater resources.〔 World water use has been growing rapidly in the last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〔("Looming water crisis simply a management problem" ) by Jonathan Chenoweth, New Scientist 28 Aug., 2008, pp. 28-32.〕). There are numerous measures of water use, including total water use, water consumption, non-consumptive use, withdrawn water use (from surface and groundwater sources), instream use, water footprint, etc.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 liters (6171 gallons). By comparison, a typical single family home in the U.S. only uses about 262 liters (69.3 gallons) of water per day (2008 estimate). This includes (in decreasing order) toilet use, washing machine use, showers, baths, faucet use, and leaks. ==Water footprint== The water footprint of an individual, community or business is defined as the total volume of freshwater used to produce the goods and services consumed by the individual or community or produced by the business. Water use is measured in water volume consumed (evaporated) and/or polluted per unit of time. A water footprint can be calculated for any well-defined group of consumers (e.g., an individual, family, village, city, province, state or nation) or producers (e.g., a public organization, private enterprise or economic sector). The water footprint is a geographically explicit indicator, not only showing volumes of water use and pollution, but also the locations.〔Definition taken from the Hoekstra, A.Y. and Chapagain, A.K. (2008) Globalization of water: Sharing the planet's freshwater resources, Blackwell Publishing, Oxford, UK.()〕〔(【引用サイトリンク】url=http://www.waterfootprint.org/?page=files/home )〕 The water footprint of a country is related to what its people eat. In 1993, Professor John Allan (2008 Stockholm Water Prize Laureate), strikingly demonstrated this by introducing the "virtual water" concept,〔 which measures how water is embedded in the production and trade of food and other products. For example, it is a common thought that the water involved in a cup of coffee is just the water in the cup.〔 There is actually 140 litres of water involved. The 140 litres of water is the amount of water that was used to grow, produce, package, and ship the coffee beans.〔 A hamburger needs an estimated 2,400 litres of water. This hidden water is technically called virtual water.〔 Therefore, eating a lot of meat means a large water footprint. However, care is needed to avoid misunderstanding the significance of water footprints of food. (See "Water footprint of products", below.) Water footprint is one of a family of footprint indicators, which also includes carbon footprint and land footprint. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「water use」の詳細全文を読む スポンサード リンク
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