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Drinking water, also known as potable water, is water that is safe to drink or to use for food preparation. The amount of drinking water required to maintain good health varies, and depends on physical activity level, age, health-related issues, and environmental conditions.[1] In the USA people, on average, drink one litre of water per day and 95% drink less than three litres per day.[2] For those who work in a hot climate, up to 16 litres a day may be required.[1]

Typically in developed countries, tap water meets drinking water quality standards, even though only a small proportion is actually consumed or used in food preparation. Other typical uses include washing, toilets, and irrigation. Greywater may also be used for toilets or irrigation. Its use for irrigation however may be associated with risks.[3] Water may also be unacceptable due to levels of toxins or suspended solids.

Globally, by 2015, 89% of people had access to water from a source that is suitable for drinking – called improved water source.[3] In Sub-Saharan Africa, access to potable water ranged from 40% to 80% of the population. Nearly 4.2 billion people worldwide had access to tap water, while another 2.4 billion had access to wells or public taps.[3] The World Health Organization considers access to safe drinking-water a basic human right.

About 1 to 2 billion people lack safe drinking water,[4] a problem that causes 30,000 deaths each week.[5] More people die from unsafe water than from war, U.N. Secretary-General Ban Ki-Moon said in 2010.[6]

Definitions

Typically in developed countries, tap water meets drinking water quality standards, even though only a small proportion is actually consumed or used in food preparation. Other typical uses include washing, toilets, and irrigation. Greywater may also be used for toilets or irrigation. Its use for irrigation however may be associated with risks.[3] Water may also be unacceptable due to levels of toxins or suspended solids.

Globally, by 2015, 89% of people had access to water from a source that is suitable for drinking – called improved water source.[3] In Sub-Saharan Africa, access to potable water ranged from 40% to 80% of the population. Nearly 4.2 billion people worldwide had access to tap water, while another 2.4 billion had access to wells or public taps.[3] The World Health Organization considers access to safe drinking-water a basic human right.

About 1 to 2 billion people lack safe drinking water,[4] a problem that causes 30,000 deaths each week.[5] More people die from unsafe water than from war, U.N. Secretary-General Ban Ki-Moon said in 2010.[6]

According to the World Health Organization's 2017 report, safe drinking-water is water that "does not represent any significant risk to health over a lifetime of consumption, including different sensitivities that may occur between life stages".[7]:2

A 'safely managed drinking water service" is "one located on premises, available when needed and free from contamination". By 2015, 5.2 billion people representing 71% of the global population used safely managed drinking water service.[8]

The terms 'improved water source' and 'unimproved water source' were coined in 2002 as a drinking water monitoring tool by the JMP of UNICEF and WHO. The term, improved water source refers to "piped water on premises (piped household water connection located inside the user’s dwelling, plot or yard), and other improved drinking water sources (public taps or standpipes, tube wells or boreholes, protected dug wells, protected springs, and rainwater collection)".[9] Improved sources are also monitored based on whether water is available when needed (5.8 billion people), located on premises (5.4 billion), free from contamination (5.4 billion), and "within 30 minutes' round trip to collect water.'[8]:3 While improved water sources such as protected piped water are more likely to provide safe and adequate water as they may prevent contact with human excreta, for example, this is not always the case.[9] According to a 2014 study, approximately 25% of improved sources contained fecal contamination.[10]

The SDC basic drinking water service is one in which a "round trip to collect water takes 30 minutes or less". Only Australia, New Zealand, North America and Europe have almost achieved universal basic drinking water services.[8]:3

Importance of access to safe drinking water

A fountain in Saint-Paul-de-Vence, France. The sign reading Eau potable indicates that the water is safe to drink.

According to the World Health Organization, "access to safe drinking-water is essential to health, a basic human right and a component of effective policy for health protection."[7]:2

Requirements

The amount of drinking water required per day is variable.[1] It depends on physical activity, age, health, and environmental conditions. In a temperate climate under normal conditions, adequate water intake is about 2.7 litres (95 imp fl oz; 91 US fl oz) for adult women and 3.7 litres (130 imp fl oz; 130 US fl oz) for adult men. Physical exercise and heat exposure cause loss of water and therefore may induce thirst and greater water intake.[11] Physically active individuals in hot climates may have total daily water needs of 6 litres (210 imp fl oz; 200 US fl oz) or more.[11] The European Food Safety Authority recommends 2.0 litres (70 imp fl oz; 68 US fl oz) per day for adult women and 2.5 litres (88 imp fl oz; 85 US fl oz) per day for adult men.[12]

In the United States, the reference daily intake (RDI) for total water is 3.7 litres (130 imp fl oz; 130 US fl oz) per day for human males older than 18, and 2.7 litres (0.59 imp gal; 0.71 US gal) per day for human females older than 18 which includes drinking water, water in b

A 'safely managed drinking water service" is "one located on premises, available when needed and free from contamination". By 2015, 5.2 billion people representing 71% of the global population used safely managed drinking water service.[8]

The terms 'improved water source' and 'unimproved water source' were coined in 2002 as a drinking water monitoring tool by the JMP of UNICEF and WHO. The term, improved water source refers to "piped water on premises (piped household water connection located inside the user’s dwelling, plot or yard), and other improved drinking water sources (public taps or standpipes, tube wells or boreholes, protected dug wells, protected springs, and rainwater collection)".[9] Improved sources are also monitored based on whether water is available when needed (5.8 billion people), located on premises (5.4 billion), free from contamination (5.4 billion), and "within 30 minutes' round trip to collect water.'[8]:3 While improved water sources such as protected piped water are more likely to provide safe and adequate water as they may prevent contact with human excreta, for example, this is not always the case.[9] According to a 2014 study, approximately 25% of improved sources contained fecal contamination.[10]

The SDC basic drinking water service is one in which a "round trip to collect water takes 30 minutes or less". Only Australia, New Zealand, North America and Europe have almost achieved universal basic drinking water services.[8]:3

According to the World Health Organization, "access to safe drinking-water is essential to health, a basic human right and a component of effective policy for health protection."[7]:2

Requirements

The amount of drinking water required per day is variable.[1] It depends on physical activity, age, health, and environmental conditions. In a temperate climate under normal conditions, adequate water intake is about 2.7 litres (95 imp fl oz; 91 US fl oz) for adult women and 3.7 litres (130 imp fl oz; 130 US fl oz) for adult men. Physical exercise and heat exposure cause loss of water and therefore may induce thirst and greater water intake.[11] Physically active individuals in hot climates may have total daily water needs of 6 litres (210 imp fl oz; 200 US fl oz) or more.[11] The European Food Safety Authority recommends 2.0 litres (70

The amount of drinking water required per day is variable.[1] It depends on physical activity, age, health, and environmental conditions. In a temperate climate under normal conditions, adequate water intake is about 2.7 litres (95 imp fl oz; 91 US fl oz) for adult women and 3.7 litres (130 imp fl oz; 130 US fl oz) for adult men. Physical exercise and heat exposure cause loss of water and therefore may induce thirst and greater water intake.[11] Physically active individuals in hot climates may have total daily water needs of 6 litres (210 imp fl oz; 200 US fl oz) or more.[11] The European Food Safety Authority recommends 2.0 litres (70 imp fl oz; 68 US fl oz) per day for adult women and 2.5 litres (88 imp fl oz; 85 US fl oz) per day for adult men.[12]

In the United States, the reference daily intake (RDI) for total water is 3.7 litres (130 imp fl oz; 130 US fl oz) per day for human males older than 18, and 2.7 litres (0.59 imp gal; 0.71 US gal) per day for human females older than 18 which includes drinking water, water in beverages, and water contained in food.In the United States, the reference daily intake (RDI) for total water is 3.7 litres (130 imp fl oz; 130 US fl oz) per day for human males older than 18, and 2.7 litres (0.59 imp gal; 0.71 US gal) per day for human females older than 18 which includes drinking water, water in beverages, and water contained in food.[13] An individual's thirst provides a better guide for how much water they require rather than a specific, fixed quantity.[14] Americans, on average, drink one litre (35 imp fl oz; 34 US fl oz) of water a day and 95% drink less than three litres (110 imp fl oz; 100 US fl oz) per day.[2]

Water makes up about 60% of the body weight in men and 55% of weight in women.[15] A baby is composed of about 70% to 80% water while the elderly are composed of around 45%.[16]

The drinking water contribution to mineral nutrients intake is also unclear. Inorganic minerals generally enter surface water and ground water via storm water runoff or through the Earth's crust. Treatment processes also lead to the presence of some minerals. Examples include calcium, zinc, manganese, phosphate, fluoride and sodium compounds.[17] Water generated from the biochemical metabolism of nutrients provides a significant proportion of the daily water requirements for some arthropods and desert animals, but provides only a small fraction of a human's necessary intake. There are a variety of trace elements present in virtually all potable water, some of which play a role in metabolism. For example, sodium, potassium and chloride are common chemicals found in small quantities in most waters, and these elements play a role in body metabolism. Other elements such as fluoride, while beneficial in low concentrations, can cause dental problems and other issues when present at high levels.

Fluid balance is key. Profuse sweating can increase the need for electrolyte (salt) replacement. Water intoxication (which results in hyponatremia), the process of consuming too much water too quickly, can be fatal.[18][19]

Water covers some 70% of the Earth's surface. Approximately 97.2% of it is saline, just 2.8% fresh. Potable water is available in almost all populated areas of the Earth, although it may be expensive and the supply may not always be sustainable. Sources where water may be obtained include:

Springs are often used as sources for bottled waters.[20] Tap water, delivered by domestic water systems refers to water piped to homes and delivered to a tap or spigot. For these water sources to be consumed safely, they must receive adequate treatment and meet drinking water regulations.[21]

The most efficient way to transport and deliver potable water is through pipes. Plumbing can require significant capital investment. Some systems suffer high operating costs. The cost to replace the deteriorating wate

Springs are often used as sources for bottled waters.[20] Tap water, delivered by domestic water systems refers to water piped to homes and delivered to a tap or spigot. For these water sources to be consumed safely, they must receive adequate treatment and meet drinking water regulations.[21]

The most efficient way to transport and deliver potable water is through pipes. Plumbing can require significant capital investment. Some systems suffer high operating costs. The cost to replace the deteriorating water and sanitation infrastructure of industrialized countries may be as high as $200 billion a year. Leakage of untreated and treated water from pipes reduces access to water. Leakage rates of 50% are not uncommon in urban systems.[22]

Because of the high initial investments, many less wealthy nations cannot afford to develop or sustain appropriate infrastructure, and as a consequence people in these areas may spend a correspondingly higher fraction of their income on water.[23] 2003 statistics from El Salvador, for example, indicate that the poorest 20% of households spend more than 10% of their total income on water. In the United Kingdom authorities define spending of more than 3% of one's income on water as a hardship.The most efficient way to transport and deliver potable water is through pipes. Plumbing can require significant capital investment. Some systems suffer high operating costs. The cost to replace the deteriorating water and sanitation infrastructure of industrialized countries may be as high as $200 billion a year. Leakage of untreated and treated water from pipes reduces access to water. Leakage rates of 50% are not uncommon in urban systems.[22]

Because of the high initial investments, many less wealthy nations cannot afford to develop or sustain appropriate infrastructure, and as a consequence people in these areas may spend a correspondingly higher fraction of their income on water.[23] 2003 statistics from El Salvador, for example, indicate that the poorest 20% of households spend more than 10% of their total income on water. In the United Kingdom authorities define spending of more than 3% of one's income on water as a hardship.[24]

In the US, the typical water consumption per capita, at home, is 69.3 US gallons (262 l; 57.7 imp gal) of water per day.[25][26] Of this, only 1% of the water provided by public water suppliers is for drinking and cooking.[27] Uses include (in decreasing order) toilets, washing machines, showers, baths, faucets, and leaks. Public water systems, defined as systems that serve more than 25 customers or 15 service connections, are regulated by the U.S. Environmental Protection Agency (EPA) under the Safe Drinking Water Act.[27] In some parts of the country water supplies are dangerously low due to drought and depletion of the aquifers, particularly in the West and the South East region of the U.S.[28][better source needed] Many of the dry, desert areas in the U.S. have this problem. According to AZCentral, "Arizona’s groundwater levels are plummeting in many areas... The water levels in more than 2,000 wells have dropped more than 100 feet since they were first drilled."[29] That sample size is approximately a fourth of Arizona's drinking-water wells.

Canada

The drinking water

The drinking water in Canada's cities is regularly tested and considered safe, but on many native reserves clean drinking water is considered a luxury.[30] The latest Canadian government of 2015 was to spend additional funds to fix the problem but has not had success.[31][32]

Access to potable water

One of the Millennium Development Goals (MDGs) set by the UN includes environmental sustainability. In 2004, only 42% of people in rural areas had access to clean water worldwide.[34] Projects such as Democratisation of Water and Sanitation Governance by Means of Socio-Technical Innovations work to develop new accessible water treatment systems for poor rural areas, reducing the price of drinking water from US$6.5 per cubic meter to US$1.[35]

The World Health Organization/UNICEF Joint Monitoring Program (JMP) for Water Supply and Sanitation[36] is the official United Nations mechanism tasked with monitoring progress towards the Millennium Development Goal (MDG) relating to drinking-water and sanitation (MDG 7, Target 7c), which is to: "Halve, by 2015, the proportion of people without sustainable access to safe drinking-water and basic sanitation".[37]

According to this indicator on improved water sources, the MDG was met in 2010, five years ahead of schedule. Over 2 billion more people us

Estimates suggest that at least 25% of improved sources contain fecal contamination.[10] 1.8 billion people still use an unsafe drinking water source which may be contaminated by feces.[3] This can result in infectious diseases, such as gastroenteritis, cholera, and typhoid, among others.[3] Reduction of waterborne diseases and development of safe water resources is a major public health goal in developing countries. Bottled water is sold for public consumption in most parts of the world.

One of the Millennium Development Goals (MDGs) set by the UN includes environmental sustainability. In 2004, only 42% of people in rural areas had access to clean water worldwide.[34] Projects such as Democratisation of Water and Sanitation Governance by Means of Socio-Technical Innovations work to develop new accessible water treatment systems for poor rural areas, reducing the price of drinking water from US$6.5 per cubic meter to US$1.[35]

The World Health Organization/UNICEF Joint Monitoring Program (JMP) for Wa

The World Health Organization/UNICEF Joint Monitoring Program (JMP) for Water Supply and Sanitation[36] is the official United Nations mechanism tasked with monitoring progress towards the Millennium Development Goal (MDG) relating to drinking-water and sanitation (MDG 7, Target 7c), which is to: "Halve, by 2015, the proportion of people without sustainable access to safe drinking-water and basic sanitation".[37]

According to this indicator on improved water sources, the MDG was met in 2010, five years ahead of schedule. Over 2 billion more people used improved drinking water sources in 2010 than did in 1990. However, the job is far from finished. 780 million people are still without improved sources of drinking water, and many more people still lack safe drinking water. Estimates suggest that at least 25% of improved sources contain fecal contamination[10] and an estimated 1.8 billion people globally use a source of drinking water which suffers from fecal contamination.[38] The quality of these sources varies over time and often gets worse during the wet season.[39] Continued efforts are needed to reduce urban-rural disparities and inequities associated with poverty; to dramatically increase safe drinking water coverage in countries in sub-Saharan Africa and Oceania; to promote global monitoring of drinking water quality; and to look beyond the MDG target towards universal coverage.[40]

Expanding WASH (Water, Sanitation, Hygiene) coverage and monitoring in non-household settings such as schools, healthcare facilities, and work places, is one of the Sustainable Development Goals.[41]

One organisation working to improve the availability of safe drinking water in some the world's poorest countries is WaterAid International. Operating in 26 countries,[42] WaterAid is working to make lasting improvements to peoples' quality of life by providing long-term sustainable access to clean water in countries such as Nepal, Tanzania, Ghana and India. It also works to educate people about sanitation and hygiene.[43]

Sanitation and Water for All (SWA) is a partnership that brings together national governments, donors, UN agencies, NGOs and other development partners. They work to improve sustainable access to sanitation and water supply to meet and go beyond the MDG target.[44] In 2014, 77 countries had already met the MDG sanitation target, 29 were on track and, 79 were not on-track.[45] The sustainable development goals were established and agreed by the UN in 2015 with the intention that they should be achieved by 2030. Goal 6 deals with the provision of clean water and sanitation.

Climate change aspects

The World Wildlife Fund predicts that in the Himalayas, retreating glaciers could reduce summer water flows by up to two-thirds. In the Ganges area, this would cause a water shortage for 500 million people. The head of China's national development agency in 2007 said 1/4th the length of China's seven main rivers were so poisoned the water har

The World Wildlife Fund predicts that in the Himalayas, retreating glaciers could reduce summer water flows by up to two-thirds. In the Ganges area, this would cause a water shortage for 500 million people. The head of China's national development agency in 2007 said 1/4th the length of China's seven main rivers were so poisoned the water harmed the skin.[46] United Nations secretary-general Ban Ki-moon has said this may lead to violent conflicts.[47][47]

Health aspects

Contaminated water is

Contaminated water is estimated to result in more than half a million deaths per year.[3] Contaminated water together with lack of sanitation was estimated to cause about one percent of disability adjusted life years worldwide in 2010.[48]

Diarrheal diseases<

Over 90% of deaths from diarrheal diseases in the developing world today occur in children under five years old.[49]:11 Malnutrition, especially protein-energy malnutrition, can decrease the children's resistance to infections, including water-related diarrheal diseases. Between 2000 and 2003, 769,000 children under five years old in sub-Saharan Africa died each year from diarrheal diseases. Only thirty-six percent of the population in the sub-Saharan region have access to proper means of sanitation. More than 2,000 children's lives are lost every day. In South Asia, 683,000 children under five years old died each year from diarrheal disease from 2000 to 2003. During the same period, in developed countries, 700 children under five years old died from diarrheal disease. Improved water supply reduces diarrhea morbidity by 25% and improvements in drinking water through proper storage in the home and chlorination reduces diarrhea episodes by 39%.[49]

Well contamination with arsenic and fluoride