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. The term "water footprint" is often used to refer to the amount of water used by an individual, community, business, or nation.
World water use has been growing rapidly in the last hundred years (see graph from New Scientist article). From 1900 to 2000, water use for agriculture went from about 500 to 2,500 cubic kilometers per year, while total use rose from around 600 to more than 3,000 cubic kilometres per year. Agriculture uses 70% of water resources.
In the U.S, the typical single family home uses about 69.3 gallons (262 litres) 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.
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 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. The more food comes from irrigated land, the larger is the water footprint.
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