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Water scarcity is the lack of sufficient available water resources to meet the demands of water usage within a region. It already affects every continent and around 2.8 billion people around the world at least one month out of every year. More than 1.2 billion people lack access to clean drinking water.〔(【引用サイトリンク】Water Scarcity. International Decade for Action 'Water for Life' 2005–2015 )〕 Water scarcity involves ''water stress'', ''water shortage'' or deficits, and ''water crisis''. While the concept of ''water stress'' is relatively new, it is the difficulty of obtaining sources of fresh water for use during a period of time and may result in further depletion and deterioration of available water resources.〔(【引用サイトリンク】Water Stress )〕 ''Water shortages ''may be caused by climate change, such as altered weather patterns including droughts or floods, increased pollution, and increased human demand and overuse of water. A ''water crisis'' is a situation where the available potable, unpolluted water within a region is less than that region's demand.〔(Freshwater: lifeblood of the planet ). peopleandplanet.net (11 November 2002). Retrieved on 27 August 2013.〕 Water scarcity is being driven by two converging phenomena: growing freshwater use and depletion of usable freshwater resources.〔Chance, Clifford (October 2011), (''Tackling Water Scarcity'' ). Advocates for International Development〕 Water scarcity can be a result of two mechanisms: physical (absolute) water scarcity and economic water scarcity, where physical water scarcity is a result of inadequate natural water resources to supply a region's demand, and economic water scarcity is a result of poor management of the sufficient available water resources. According to the United Nations Development Programme, the latter is found more often to be the cause of countries or regions experiencing water scarcity, as most countries or regions have enough water to meet household, industrial, agricultural, and environmental needs, but lack the means to provide it in an accessible manner.〔United Nations Development Programme (2006). (Human Development Report 2006: Beyond Scarcity–Power, Poverty and the Global Water Crisis ). Basingstoke, United Kingdom:Palgrave Macmillan.〕 The reduction of water scarcity is a goal of many countries and governments. The UN recognizes the importance of reducing the number of people without sustainable access to clean water and sanitation. The Millennium Development Goals within the United Nations Millennium Declaration state that by 2015 they resolve to "halve the proportion of people who are unable to reach or to afford safe drinking water."〔(Background page ), United Nations Millennium Development Goals website, retrieved 16 June 2009〕 ==Water stress== The United Nations (UN) estimates that, of 1.4 billion cubic kilometers (1 quadrillion acre-feet) of water on Earth, just 200,000 cubic kilometers (162.1 billion acre-feet) represent fresh water available for human consumption.〔(Texas Water Report: Going Deeper for the Solution ). Texas Comptroller of Public Accounts. 〕 More than one in every six people in the world is water stressed, meaning that they do not have access to potable water.〔 Those that are water stressed make up 1.1 billion people in the world and are living in developing countries. According to the Falkenmark Water Stress Indicator,〔 a country or region is said to experience "water stress" when annual water supplies drop below 1,700 cubic metres per person per year. At levels between 1,700 and 1,000 cubic meters per person per year, periodic or limited water shortages can be expected. When a country is below 1,000 cubic meters per person per year, the country then faces water scarcity . In 2006, about 700 million people in 43 countries were living below the 1,700 cubic metres per person threshold.〔 Water stress is ever intensifying in regions such as China, India, and Sub-Saharan Africa, which contains the largest number of water stressed countries of any region with almost one fourth of the population living in a water stressed country.〔 The world's most water stressed region is the Middle East with averages of 1,200 cubic metres of water per person.〔 In China, more than 538 million people are living in a water-stressed region. Much of the water stressed population currently live in river basins where the usage of water resources greatly exceed the renewal of the water source. 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 scarcity」の詳細全文を読む スポンサード リンク
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